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1 Lecture Note Soil and Groundwater Pollution Seoul National University Civil and Environmental Engineering Kyoungphile Nam

2 Contents Ⅰ. Soil and Pollutants 1) Water and Soil - Physical-Chemical Characteristics of Waters (EPS, Ch3) - Physical-Chemical Characteristics of Soils and the Subsurface (EPS, Ch.2) - Biotic Characteristics of the Environment (EPS, Ch.5) 2) Major Pollutants - Common Hazardous Wastes: Nomenclature, Industrial Uses, Disposal Histories (HW, Ch.2) - Common Hazardous Wastes: Properties and Classification (HW, p ) 3) Interactions between Soil and Pollutants(fate and transport) - Physical Processes Affecting Contaminant Transport and Fate (EPS, Ch.6) - Contaminant Release and Transport from the Source (HW, Ch.8) - Chemical Processes Affecting Contaminant Transport and Fate (EPS, Ch.7) - Biological Processes Affecting Contaminant Transport and Fate (EPS, Ch.8) Ⅱ. Site Investigation, Evaluation, Remediation 1) Contamination Investigation - Source Analysis (HW, Ch.4) 2) Risk Assessment - Risk Assessment (EPS, Ch.14) 3) Remediation Technologies - Soil and Groundwater Remediation (EPS, Ch.19) Ⅲ. Special Topic: Applied Ecological Engineering 1) Ecological Engineering (Ch.3-6) 2) Case Study: Ecological Restoration Examples (Texts) EPS: Environmental and Pollution Science (2nd Ed), I.L.Pepper, C.P.Gerba, M.L.Brusseau, 2006, Academic Press HW: Hazardous Wastes-Sources, Pathways, Receptors (2nd Ed), R.J. Watts, 1998, John Wiley & Sons Ecological Engineering-Bridging Between Ecology and Civil Engineering, 2005, Hein Van Bohemian, Aeneas Technical Publishers

3 (Lecture 1) EPS Ch 3. Physical-chemical characteristics of water Unique properties of water - polarity - universal solvent Gases in water - oxygen; DO - carbon dioxide <-> bicarbonate <-> carbonate (-> precipitates) Oxidation-reduction reaction - oxidation-reduction potential (ORP) or redox potential (1 volt = 1 Eh) - measures the tendency for a solution to either gain or lose electrons - higher (lower) ORP -> easily gain (lose) electrons - effect on bioavailability of metal ions (and nutrients). Fe(III)-phosphate <-> Fe(II) + phosphate. Hg <-> methyl-hg Water in the subsurface (groundwater): Supplement 1 - hydraulic head, soil-water potential - Darcy s law - hydraulic conductivity (K)

4 (Lecture 2) EPS Ch 2. Physical-chemical characteristics of soils and the subsurface Soil - weathered end product - soil-forming factors: parent material, climate, living organisms, topography, time - surface soil vs. subsurface soil - unsaturated zone (vadose zone, capillary fringe) vs. saturated zone - water movement; nonspontaneous vs. spontaneous - solid phase, gas phase, liquid phase - aggregation, structure Solid phase % inorganic, 1-5% organic matter - soil texture; clay, silt, sand (soil textural triangle) - pore space; filled with gas, liquid - interaggregate pores vs. intraaggregate pores - cation exchange capacity (CEC) - soil ph - soil organic matter (SOM) Gas phase - N2 >>>> O2 >> CO2 - soil respiration; aerobic vs. anaerobic - soil moisture; O2 availability

5 Liquid phase - water; polar - field capacity (water-holding capacity) Basic physical properties - bulk density (ρ b, dry soil mass/total volume, g/cm -3 ) - porosity (n, void volume/bulk volume, unitless). sand < silt < clay. packing arrangement, grain size distribution. when saturated soil, porosity = water content Soil water content - gravimetric water content; mass (θ g ) - volumetric water content; volume (θ v ) Soil temperature - temperature reaction rate - surface; fluctuate - subsurface; relatively constant

6 (Lecture 3) EPS Ch 5. Biotic Characteristics of the Environment Major groups of microbes; virus, bacteria, fungi, algae, protozoa - dominant culturable soil bacteria; Arthrobacter, Streptomyces, Pseeudomonas, Bacillus Bacteria μm, single-celled, no nuclear membrane - genetic exchange; conjugation, transformation, transduction - abundant, diverse, ubiquitous, (e.g.) cells/ g-subsurface soil, cells/ g-surface soil - main removal mechanism of pollutants in soil Mode of nutrition (energy, carbon source) - autotrophic; chemoautotrophic, photoautotrophic - heterotrophic; chemoheterotropic, photoheterotrophic Types of electron acceptors - aerobic (O 2 ) - denitrifying (NO 3- ) - sulfate-reducing (SO 4 2- ) - anaerobic (CO 2 ) Ecological classification - K-selected organisms; under eutrophic env, (e.g.) rhizobacteria - r-selected organisms; under oligotrophic, rapid growth, (e.g.) pollutants-degrading bacteria

7 Biological generation of energy; energy stored as ATP - photosynthesis; E needs to be provided (negative ΔG) by sunlight - respiration. aerobic heterotrophic respiration; negative ΔG, Pseudomonas, Bacillus. aerobic autotrohphic respiration; negative ΔG, Nitrosomonas, Nitrobacter. facultative anaerobic, heterotrophic/autotrophic respiration. anaerobic heterotrophic respiration. fermentation Soil as an environment for microbes - biotic stress;. competition for nutrients, water, growth factors. inhibitory or toxic substances by other microbes (e.g.) antibiotics. predation - abiotic stress;. light. soil moisture, soil temp, ph, texture. soil carbon, nitrogen. Soil redox potential; +800 mv -300 mv (Table 5.5), Eh-pH diagram (Fig. 5.12) Activity and physiological state - viable and culturable (i.e., CFU, plate counting) - viable but unculturable indigenous vs. introduced ecological niche

8 (Lecture 4) HW Ch 2. Common Hazardous Wastes: Nomenclature, Industrial Uses, Disposal Histories 1. Introduction to Organic Chemistry (p. 48) : organic compounds; mainly C, H but O, N, P, S, and halogens (Cl, Br,..) also 1) Carbon bonding a) ionic bonding; donation of a valence electron from an electropositive atom to an electronegative atom (e.g., NaCl, MgCl 2,...) b) covalent bonding; - occurs when two atoms share valence electrons - usually N, O, C, S, or Si is involved (e.g., H 2 O, NH 3, H 2 S,...) - the bonds of organic compounds are covalent! Polarity, nucleophilic attack, and degradation (p. 51) 1 polarity due to the differences in electronegativity between atoms 2 unequal distribution of electron clouds --> partial charges --> polarity (e.g.) compare the electron clouds of H 2 and H 2 O 3 chemical reaction: - low electron density (i.e., electron poor region of a chemical) allows attack by nuclephiles (such as H 2 O, OH - ), (e.g.) parathion 4 biological reaction: - biological degradation rates are lowered by electron-poor areas of organic compounds, (e.g.) pentachlorophenol

9 2) Nomenclature of organic compounds (p. 51) a) aliphatic hydrocarbons; alkanes (radical forms; alkyl groups), alkenes (PCE, TCE..), alkynes b) aromatic hydrocarbons; - monoaroatics (phenolics, BTEX,...) - polyaromatics (PAHs,...) c) isomers; same chemical formulas but different structural configurations (formed from 4-carbon aliphatic compounds) d) IUPAC (International Union of Pure and Applied Chemists) nomenclaure vs. conventional name (e.g.) CH 2 Cl 2 ; 1,2-dichloromethane, methylene chloride Aromatic compounds (p. 63) 1 resonance structure (alternating single and double bonds between C atoms) 2 π-bonds between aromatic compounds (stacking of aromatic rings possible!) 3 more stable than alkenes (e.g., benzene vs. cyclohexene) 4 substitution reaction for benzene and addtion reaction for cyclohexene e) Nomenclature of benzene derivatives (p. 64) f) Polycyclic Aromatic Hydrocarbons (PAHs, p. 68) ; incomplete combustion of organic compounds, heavier fractions of petroleum products, cigarette smoke, blackened barbecued food,...

10 2. Petroleum Products (p. 77) 1) UST (Underground Storage Tank) leakage 2) aliphatic and aromatic hydrocarbons 3) BTEX (Benzene, Toluene, Ethylbenzene, Xylenes) 4) TPHs (Total Petroleum Hydrocarbons) 5) Characteristics of petroleum products (Table 2.11, Table 2.12) 6) Gasoline additives; - Pb (leaded vs. unleaded) - oxygenates (e.g., methyl tert-butyl ether, MTBE) 3. Nonhalogenated Solvents (p. 81) 1) Hydrocarbons 2) Ketones 3) Alcohols and Esters 4. Halogenated Solvents (p. 85) : an important class of environmental contaminants (volatile, mobile, dense, moderate soluble, less degradable) - halogenation of hydrocarbons --> lower flammability, higher density and viscosity --> improved solvent properties (for degreasing and cleaning) - methane derivatives; methylene chloride (dichloromethane), chloroform (trichloromethane), carbon tetrachloride (tetrachloromethane) - derivatives of ethane, ethene (ethylene); 1,1,1-trichloroethane (TCA), trichloroethylene (trichloroethene, TCE), perchloroethylene (tetrachloroethene, PCE)

11 5. Pesticides (p. 90) 1) Insecticides a) organochlorine insecticides; - highly lipophilic, recalcitrant, bioconcentrated, chronic toxicity - most banned nowadays but present in the environment as residues (e.g.) DDT, methoxychlor, lindane, aldrin, dieldrin,... b) organophosphorus esters; - less persistent (days to weeks), less adverse effects, more degradation, but, higher acute toxicity than organochlorine insecticides, (e.g.) parathion, malathion,... c) carbamate esters; - widely used along with organophosphorus esters - moderately labile in the environment, low acute toxicity, (e.g.) carbaryl, carbofuran, aldicarb,... 2) Herbicides (generally less persistent and chronically toxic than organochlorines) a) acid amides; alachlor, propanil,,... b) aliphatics; glyphosate, methyl bromide,... c) phenoxy herbicides; 2,4-D (2,4-dichlorophenoxy acetic acid), 2,4,5-T (2,4,5-trichlorophenoxy acetic acids) d) substrate ureas; diuron, linuron (persist in soils for up to a year) e) triazines; atrazine (strongly sorb but mobile also, found in aquifers) 3) Fungicides a) pentachlorophenol (PCP); wood preservative and insecticide also b) ethylene dibromide (1,2-dibromoethane, EDB); soil fumigants

12 6. Explosives (p. 104) : aliphatic or aromatic structure with substituted nitro (-NO 2 ) groups - aliphatic nitrate esters; nitroglycerin - nitramines; RDX (cyclotrimethylenetrinitramine), HMX (cyclotetramethylenetetranitramine) - nitroaromatics; TNT (2,4,6-trinitrotoluene), picric acid (2,4,6-trinitrophenol) 7. Industrial Intermediates (p. 109) - phthalene esters; plasticizers or softners (e.g., phthalic acid) - chlorobenzenes, chlorophenols;. 2,4-dichlorophenol in the manufacture of 2,4-D. 2,4,5-trichlorophenol in the manufacture of 2,4,5-T - anilines; in the synthesis of inks, dyes, frugs, photographic developers - hexachlorocyclopentadiene; in the synthesis of aldrin, dieldrin, chlordane,,,, 8. Polychlorinated Biphenyls (p. 114) - heat-stable nonflammable oils once used extensively as transformer and hydraulic fluids (--> high persistence and toxicity) - banned in 1979, but still present in the environment - biphenyl molecule with chlorine substitution up to 10 positions - congeners; 207 products possible, (e.g.) Aroclor 1221, Aroclor 1232, Polychlorinated dibenzodioxins and dibenzofurans (PCDDs, PCDFs; p. 116) - not intentionally manufactured chemicals - trace impurities formed during the manufacture, chlorination or combustion of other organic compounds - collectively called "(chlorinated) dioxins", derivatives of dibenzo-p-dioxin - 75 possible congeners

13 Generation of dioxins and their toxicities 1 In the course of manufacturing 2,4,5-T (i.e., trichlorophenol + chloroacetic acid), two molecules of trichlorophenols may dimerize to form 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) 2 Chlorinated dioxins are produced during (incomplete) combustion at low-to-moderate temperatures, even from innocuous materials such as firewood (like PAHs) 3 2,3,7,8-TCDD is the most toxic (--> Toxic Equivalent Factor, TEF 1.0) 4 Other dioxins' toxicities are expressed based on a reference TEF of 1.0

14 10. Metals and Inorganic Nonmetals (p. 119) - semantic definitions of heavy metals; i) elements with atomic numbers greater than iron, ii) metals with densities greater than 5.0 g/cm 3 - what about Al (atomic number 13)?; regarded as a heavy metal - another definition; metals cause adverse biological (=toxic) effects 1) Arsenic (As) a) present as anionic forms in solution b) arsenite AsO 3 - (As 3+ ); under reduced conditions, most toxic c) arsenate AsO 4 3- (As 5+ ); under aerobic conditions, less toxic d) extensively used in agriculture (weed control, insecticidal ingredients,...) 2) Cadmium (Cd) a) always found as Cd 2+ b) highly toxic and accumulative 3) Chromium (Cr) a) highly toxic, stable, soluble; Cr 6+ (chromate CrO 4 2-, dichromate Cr 2 O 7 2- ) b) insoluble form in water; Cr 3+ (low toxicity) 4) Lead (Pb) a) low water solubility and strong tendency to sorb and exchange on solids b) less mobile in the environment 5) Nickel (Ni)

15 6) Mercury (Hg) a) three forms possible; elemental, inorganic, organic b) Hg 0 present as a liquid at room temperature c) Hg 0 for porosity measurement (e.g., Mercury porosimeter) d) bioconcentration (in fish); methyl mercury (CH 3 Hg + ) e) volatilization and global recycling; dimethyl mercury (CH 3 HgCH 3 ) f) HgCl 2 ; biocide (used to sterilize environmental samples) 7) Cyanides (-CN) a) inorganic nonmetal anions b) HCN; highly toxic, acute poison 8) Asbestos a) a group of six mineral fibers (hydrated magnesium silicates) b) nonflammable, strong, resistant to acids c) indoor air pollution d) toxic only through inhalation (not from dermal contact, ingestion,..) --> "route of exposure" is important!!! 11. Nuclear Wastes (p. 127)

16 (Lecture 5) HW Ch 3. Common Hazardous Wastes: Properties and Classification 1. Common Concentration Units (p. 155) 1) SI vs Non-SI units (SI; International System of Units) 2) conversion of ppm to concentration 2. Water Solubility (p. 160) 1) definition; "maximum (saturation) concentration of a substance that will dissolve in water in a given temperature" 2) soluble vs. insoluble (filtration through 0.45-μm pore sized membrane) 3) polar (hydrophilic) vs. nonpolar (hydrophobic); Table 3.5 (e.g.) water vs. hexane 4) controls the environmental fate of waste chemicals a) inversely proportional to sorptivity, bioaccumulation, volatilization from aqueous solutions b) influence biodegradation, photolysis, chemical oxidation,... 5) determined by intermolecular attractive forces between solute-solvent molecules a) van der Waals force b) hydrogen bonding (mainly with -OH, -NH 2 groups) c) dipole-dipole interaction (by electronegativity difference) 6) related to the size and structure of a chemical a) functional groups may or may not affect b) molecular volume (halogens increase m.v. -> decrease water solubility) c) Table 3.1

17 7) water solubilities of weak organic acids (bases) a) basic (ionized) form is more soluble than acidic (unionized) form b) [ionized forms] water solubility c) ph vs. pka (ph where [unionized forms] = [ionized forms]) - ph < pka ; protonated (acidic, unionized form) - ph > pka ; deprotonated (basic, ionized form) d) solubility change depending on ph e) Handerson-Hasselbalch equation (Fig. 3.1) - calculates the degree of acidic dissociation at a given ph f) fraction of unionized acid (α); - α = (1 + ) -1 (Ka = ; acid dissociation constant) - used to correct transport models; ionized forms are miscible in water -> no retardation (p. 281) 8) acidity of chlorophenols with higher chlorine substitution (Table 3.2) a) Cl- is a highly electronegative element b) more Cl- on the ring -> proton(s) more easily released -> higher acidity 3. Density and Specific Gravity (p. 167) - density; ratio of mass to volume (g/ml, kg/m 3 ) - specific gravity; a compound's density to that of water (1.0 g/ml at 4 C) - (aliphatic) hydrocarbons are lighter than water - substitution of a chlorine atom on a hydrocarbon increases its density (density; H < C < Cl) - influence contaminants' fate and remediation technology selection (esp. in groundwater); Table metals are more dense than water

18 4. Light and Dense Nonaqueous Phase Liquids (p. 170) ; NAPL(s) as a continuous source in the subsurface system 1) LNAPL (Light Nonaqueous Phase Liquid) / Fig. 3.2 (a) a) floats on groundwater surface easily detected b) aliphatic hydrocarbons, BTEX, nonhalogenated solvents,... 2) DNAPL (Dense Nonaqueous Phase Liquid) / Fig. 3.2 (b), Example 3.4 a) sinks into the bottom of subsurface system (fractures, pores,...) b) form pools, lenses c) halogenated solvents,... 3) dissolution a) transfer of a compound from its insoluble phase into the water b) generally rate-limiting step in degradation (remediation) of a contaminant c) rate of dissolution [(mg/l)/min] = K ㆍ (C s - C) K (min -1 ); mass transfer coefficient (from NAPL to water phase) C s (mg/l); contaminant water solubility C (mg/l); contaminant concentration at a site 4) effective solubility a) solubility of the mixtures of NAPLs b) usually less than the water solubility of a single compound c) effective solubility of compound i (mg/l) S i e = X i S i γ i X i = mole fraction of compound i in the NAPL mixture S i = water solubility of compound i found in literatures γ i = correction factor that normalizes solubility based on field conditions and water chemistry 5. Flammability Limits (p. 177)

19 (Lecture 6) EPS Ch 6. Physical Processes Affecting Contaminant Transport and Fate Contaminant transport and fate in the environment The health risk posed by a contaminant to humans is a function of its pollution potential as well as its toxicity advection dispersion - mechanical dispersion - molecular diffusion mass transfer - volatilization/evaporation - sorption - dissolution transformation - biological - chemical

20 Dispersion Spatial distribution of contaminant plume Breakthrough curves Advection-dispersion model What about transformation term is incorporated??? advection-dispersionreaction equation (ADRE)

21 Estimating phase distributions of contaminants Retardation factor R = groundwater velocity contaminant velocity dissolved conc + adsorbed conc dissolved conc

22 (Lecture 7) HW Ch 8. Contaminant Release and Transport from the Source - Contaminants distributions are commonly quantified using sampling and analysis schemes because monitoring data are more reliable and thus preferred. - However, in some cases, values obtained from prediction models are still useful. 1. The Controlling Processes in Contaminant Release and Transport: Sorption, Volatilization, Transformation (p. 405) a) atmospheric and subsurface transport (Fig. 8.1) - major contaminants' trnasport through the subsurface and atmosphere - once released from the source, contaminants experience sorption, volatilization, and transformation b) conceptual pathway analysis (Example 8.1) 2. Mass Transfer of Contaminants in the Atmospheric and the Subsurface (p. 408) 1) Mass balance a) expressions change in storage of mass = mass transported IN - mass transported OUT +mass PRODUCED by sources - mass ELIMINATED by sinks rate of change in storage of mass = mass transport rate in - mass transport rate out +mass production rate by sources - mass elimination rate by sinks rate of mass accumulation within the system boundary = rate of mass flow into the system - rate of mass flow out of the system -/+rate of reaction within the system (* rate = mass per time [M/T]) If storage does not change with time the left-hand sides are zero steady state

23 b) described by a general mass flux vector J; the mass flux vector in the x, y, or z direction m; contaminant mass per unit volume t; time c) differences between atmospheric and subsurface definitions of mass - volume of air; total volume of the sample - in the subsurface; "porosity" and "retardation" concepts included m = C (atmosphere) m = n R C (subsurface) 2) Two important phenomena of movement a) advection (i.e., wind; pore-water velocity) b) dispersion c) flux J = J adv + J disp

24 3) Advective flux a) mainly resulting from bulk, large scale movement of a medium (e.g.) wind blows, water flows,... b) so, transported at the same velocity as the fluid - macroscale view; center of mass of chemical moves by advection - microscale view; Fickian transport occurs at the same time c) convection; often vertical advection (but, considered almost a similar term) d) flux density (J) - mass of chemical transported across an imaginary surface of unit area per unit of time J = C V J; advective flux (mg/m 2 -sec) [M/L 2 T] / C; contaminant conc. (mg/m 3 ) [M/L 3 ] V; fluid velocity (m/sec) [L/T] - in groundwater, V is pore-water velocity J = C (nv p ) n; porosity (i.e., n e ) / v p ; seepage (pore-water) velocity (m/sec) 4) Dispersive flux a) "all of the mass transfer exclusive of advection" b) Turbulent diffusion ("eddy diffusion") - resulting from random mixing of air or water by eddies - carries mass in the direction of decreasing chemical concentration (e.g.) dye blob injected into a river - important in surface water and air (not considered in the subsurface) - use Fick's first law to describe J [M/L 2 T]; dispersive flux in the x direction n; porosity D; turbulent diffusion coefficient C [M/L 3 ]; chemical concentration x [L]; distance over which a concentration change is considered

25 c) (mechanical) dispersion (hydraulic dispersion) - fluctuations in the velocity field at scales smaller than advection - groundwater flow;. no eddies present due to its low velocity. but still random detours exist, causing mixing chemicals - transport of a chemical from regions of higher to lower concentration - use Fick's first law to describe J [M/L 2 T]; dispersive flux in the x direction n; porosity D mech ; mechanical dispersion coefficient C [M/L 3 ]; chemical concentration x [L]; distance over which a concentration change is considered - related to the tortuous path of water through the subsurface solids - tortuosity of flow paths and contaminant concentration result in the longitudinal mixing of contaminants d) molecular diffusion - random movement of chemicals due to local concentration gradient - lower flux density compared to other Fickian transport processes - use Fick's first law to describe J [M/L 2 T]; dispersive flux in the x direction n; porosity D; molecular diffusion coefficient C [M/L 3 ]; chemical concentration x [L]; distance over which a concentration change is considered - not related to advective, dispersive, or turbulent motion but dependent on contaminants' molecular properties (primarily, size) and temperature

26 e) hydrodynamic dispersion - the spreading of a tracer beyond the region expected to the average flow alone - the macroscopic outcome of the actual movements of individual tracer particles through the pores and the various physico-chemical phenomena that take place within the pores - J disp = J mech + J mole - D = D mech + D mole Transport in total: J = J adv + J dis One-dimensional situation is considered, flow is anisotrophic - flow direction vs. perpendicular to flow, - homogeneous medium vs. heterogeneous medium, - time 5) The advection-dispersion equation - for the subsurface transport; characteristics of the medium - analytical methods - numerical methods 3. Atmospheric Transport Following Volatilization Releases (p. 413)

27 4. Subsurface Transport of Contaminants (p. 421) 1) Subsurface transport and exposure a) migration through the unsaturated zone to groundwater b) exposure routes - subsurface contamination; volatilization, leaching to groundwater - groundwater; drinking water wells, other uses 2) Nature of the subsurface environment (Fig. 8.12) a) vadose zone - subsurface region where the pore-water pressure is less than atmospheric pressure - pore-water pressure increases linearly with depth - water present as a thin film on solid surfaces - consists of solid particles, water (i.e,. volumetric water content) and air (i.e., empty pore space) - unsaurated zone; b) saturated zone - boundary of water table; pore-water pressure = atmospheric pressure - below the water table where the pore spaces are filled with water - pore-water pressure is greater than atmospheric, and increases linearly with depth c) more terms - capillary fringe; an area where the upward movement of water from the saturated zone due to surface tension and capillary forces - aquifer; a saturated permeable geologic unit that can transmit sufficient water under ordinary hydraulic gradients - aquitard; the strata that are less permeable than an aquifer - unconfined aquifer; - confined aquifer;

28 d) porous and heterogeneous; most important subsurface properties!!! e) Darcy's Law - an empirical mathematical description between the flow rate of a fluid through a porous medium and the head gradient (basis for advection in groundwater) f) hydraulic conductivity - a parameter that describes the ease with which a fluid passes through porous media - a function of a fluid and a medium (Table 8.2) g) pore-water velocity (seepage velocity) - the velocity that accounts for the cross-sectional area / related to porosity of a medium 4.1. Development and use of groundwater transport equations a) factors influencing subsurface transport (rates) of contaminants - media; characteristics of subsurface - fluid; flow (rate) of groundwater - interactions; sorption, transformation, volatilization,... b) assumptions - the media are characterized by constant density and viscosity - the media are isotrophic, the flow is incompressible, and the system is saturated c) many models are available - one-, two-, three-dimensional flow - pulse contaminant input and continuous contaminant input - presence or absence of transformation reactions - BUT, limited by estimation of parameters such as dispersion coefficient, transformation rate,... d) one-dimensional advection-dispersion equations - simple models relatively accurate for simple systems (e.g.) soil columns, landfill leachate migration,... - a pulse input with or without transformation - a continuous input with or without transformation

29 1) Pulse model a) describes a pulse input of contamination such as hazardous materials spill b) derived with zero background concentration at the beginning (x = 0) c) a pulse input model without transformation; at a distance x downgradient and time t d) a pulse input equation with transformation M; the mass spilled per cross-sectional area (g/m 2 ) D' x ; D/R (m 2 /day) D x ; dispersion coefficient in the x direction x; distance from the source (from the point of spill) v' x ; v/r (m/day) v x ; pore-water velocity in the x direction R; retardation factor k'; k/r (day -1 ) k; first-order transformation rate constant (day -1 ) e) estimation of downgradient concentration from a source with transformation (Example 8.4)

30 2) Plume model a) describes a continuous input from a source (e.g., landfill) b) a plume input equation without transformation C(x,t); contaminant conc. at point x and time t (mg/l) erfc; the complementary error function under most conditions, the right-hand term becomes negligible, c) estimation of downgradient conc from a surface impoundment without transformation (Example 8.5) 3) Advection-Dispersion-Reaction Equation (ADRE) a) from the advection-dispersion equation ADRE can be derived to account for transformation through the addition of a new term for first-order degradation (at a distance x and time t) C; contaminant conc. in the aqueous phase (mg/l) R; retardation factor (1+ K d ) D; groundwater dispersion coefficient (m 2 /day) v; pore-water velocity (m/day) k; first-order degradation rate constant (day -1 )

31 b) effect of retardation on contaminant profile (Fig. 8.13) c) effect of transformation on contaminant profile (Fig. 8.14) d) an analytical solution to the ADRE equation (Eq. 8.35, p. 431) - one-dimensional contaminant transport with transformation (Example 8.6) used to estimate the time required for a relative contaminant concentration to reach a distance downgradient - development of a contaminant profile in groundwater (Example 8.7) used to estimate a contaminant conc. profile as a function of time at a set distance (or as a function of distance at a set time) 4.2. Contaminant Transport in the Vadose Zone a) vadose zone - may be less than a meter to hundreds of meters deep - higher organic matter, more metal oxides, more microbial activity b) contaminants can move in the vadose zone - as a solute in the water phase - as a separate, immiscible NAPL phase - as a gas resulting from volatilization c) percolation rate - increases as a function of porosity - ranges from cm/h to cm/yr (recall infiltration rate!!!)

32 (Lecture 8) EPS Ch 7. Chemical Processes Affecting Contaminant Transport and Fate Basic properties of inorganic contaminants 1) Speciation - ph, redox status - metal solubility - surface charge of minerals - adsorption(<-> desorption) - precipitation(<-> dissolution) 2) Aqueous phase activity and concentration - effective conc (or activity) concentration - activity coefficient (γ i ). approach 1 only in a very dilute solution - Ionic strength (I) - activity coefficient

33 Ion hydration and hydrolysis 1) Ion hydration - ions dissolved hydrated - ionic potential (Z/r) - small ionic potential hydrated cations, - high ionic potential hydrolysis insoluble oxides(hydroxides), soluble oxyanions 2) Ion hydrolysis - breaking of O-H bonds in water molecules that are attached to the ions - proton dissociation - depends on ph lead hydroxide (insoluble) at high ph. precipitation limited transport. low bioavailability low risk

34 Aqueous phase complexation reactions - metal-ligand complex. cation; central metal group. coordinating anion; ligand - stability constant (K stab ). mobility; HgCl + > Hg 2+ Precipitation-dissolution reactions solubility product constant (K sp )

35 Basic properties of organic contaminants 1) Phase transfer 2) Dissolution - likes dissolves likes - miscibility with water 3) Evaporation - transfer from the pure liquid (or solid) to the gas phase - vapor pressure. an index of the degree to which a compound will evaporate. a measure of solubility of a compound in air - governed by chemical-chemical interactions, temperature

36 Volatilization - transfer of contaminant molecules between water and gas phases - Henry s law; C g = H C w (at equilibrium) Multiple-component organic phase - NAPL - transfer of individual components of a multiple component into water; Raoult s law; C i w = X i S i w Sorption 1) Inorganics - surface complex - cation exchange capacity (CEC) exchangeable - adsorption mainly on clay minerals (as well as soil organic mater) - PZC (point of zero charge). the suspension ph at which a surface has a net charge of zero 2) Organics - hydrophobic effect. expulsion of a nonpolar compound from water. mainly on soil organic matter. distribution (partitioning) coefficient; K d (K p )

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38 3) Sorption isotherm - relationship between the conc of sorbed contaminant and the conc of dissolved contaminant - at the same temperature, in equilibrium - Freundlich isotherm; C sorb = K f C n w - n. a measure of nonlinearity. Indicates sorption mechanism - Langmuir isotherm Abiotic transformation mechanisms 1) Hydrolysis 2) Oxidation-reduction reactions - heterotrophic respiration - electron acceptors. nitrate. Mn(Fe) oxides. sulfate 3) Photochemical reactions 4) Radioactive decay

39 Transformation rates - reaction kinetics. zero order rxn; constant amount is lost per unit time, all substrates are available. first order rxn; exponential decrease of in initial conc, half-life (independent of initial conc). second order rxn; half-life (dependent of initial conc). pseudo-first order rxn; widely employed in the env. R = k[a][b] when [A] is in large excess amount, k[a] = k R = k [B] half-life = 0.693/k Log[S] remaining - saturation kinetics. surface catalysis (enzyme) reaction; Michaelis-Menton kinetics. bacterial growth; Monod equation zero Time 2nd 1st Enzyme reaction Bacterial growth

40 (Lecture 9) EPS Ch 8. Biological Processes Affecting Contaminant Transport and Fate Biodegradation - breakdown of organic compounds through microbial activity - pollutants as substrates (food C & E source) - when biodegraded into CO2 and H2O mineralization - a set of enzymatic activity - cometabolism; partial degradation, no benefit (C &E)

41 Environmental effects on biodegradation 1) Terminal electron acceptor (TEA) - oxygen; highest energy generation faster biodegradation addition of oxygen; can improve biodegradation rates - rule of thumb; reduced C oxidized C TPH stable under anaerobic conditions TCE stable under aerobic conditions

42 2) Microbial population and soil organic matter content - cultural bacterial numbers; ca CFU/g-soil - decrease with depth by > 2 orders of magnitude - mainly due to oxygen and nutrients (SOM and trace minerals) Number of bacteria participating in biodegradation is important - population growth; acclimation - acquisition of required metabolic activity; adaptation 3) Nitrogen and phosphorous - may act ac limiting factors - C:N:P 100:10:1 4) Pollutant structure - intrinsic property of p ollutants; recalcitrant matrix and time effect; persistent

43 Aerobic biodegradation - mainly use preexisting pathways; similar to naturally occurring compounds 1) Aliphatic hydrocarbons CH 3 -(CH 2 ) n -CH 3 CH 3 -(CH 2 ) n -CH 2 OH CH 3 -(CH 2 ) n -CHO CH 3 -(CH 2 ) n -COOH β-oxidation (C 2 -removal) TCA cycle CO 2 + H 2 O + NADH ADP NAD + 2) Aromatic hydrocarbons - low solubility & high sorption low biodegradation low bioavailability - dioxygenase ATP 3) Alicyclic hydrocarbons - saturated carbon chains single isolate consortium (mixed culture)

44 Anaerobic biodegradation - anaerobic respiration; use TEA (i.e., Fe/Mn, NO 3-, SO 4 2-, CO 2 ) other than oxygen is used 1) Aliphatic hydrocarbons - reductive dehalogenation 2) Aromatic hydrocarbons - benzoate

45 Transformation of metals - oxidation/reduction - complexation - alkylation - valence change Cr 6+ Cr 3+ As 3+ As 5+

46 (Lecture 10) HW Ch 4. Source Analysis 1. Materials Balances and Waste Audits (p. 212) 2. Hazardous Waste Site Assessments (p. 216) - Hazardous wastes sites must be assessed to determine the extent of contamination before cleanup is initiated. (a) Phase I assessment - to confirm the suspicions of the presence of hazardous wastes - involves documents and paper research including a chemical inventory evaluation, interviews with current and former personnel and neighbors, regulatory agency record searches and interviews, and title searches and reviews of historical ownership,... - on-site inspection also required (i.e., to find clues of contamination) - to determine the need for further investigation, not to determine whether a site is contaminated or not (b) Phase II assessment - to confirm or deny the presence of hazardous wastes at the site - includes a detailed evaluation of pathways and potential receptors - extensive sampling and analysis around source areas (c) Phase III assessment - conducted if Phase II assessment shows that the site is contaminated - to detail the extent of contamination in terms of the area, volume, and concentrations - more extensive sampling and analysis around the source and adjacent areas (i.e., soil, subsurface, groundwater) - to provide criteria for an appropriate remedial design

47 4. Source Sampling (p. 219) - one of the most important procedure - generally use statistical methods to minimize sampling errors - sampling errors mainly from heterogeneous media - sampling errors are usually greater than analytical errors 5. Source Sampling Procedures and Strategies (p. 229) 6. Sampling away from the Source (p. 232) - often a prerequisite before designing remediation systems and documenting their effectiveness during operation 7. Priority Pollutant and Sample Analyses (p. 241) - among a list of 129 chemicals, 114 organics, 13 metals, 1 mineral, and 1 inorganic nonmetal - organics; extraction through simple solvent shaking or Soxhlet apparatus (continuous solvent flushing with heat) - analysis; GC/FID (EDC...), HPLC, AA (Atomic Absorption) spectrophotometer, ICP (Inductively Couple Plasma) - US EPA Method 600 series (for aqueous samples), 8,000 series (for soils and sludges); Table 4.3

48 (Lecture 11) ESP Ch 14. Risk Assessment Risk assessment - the process of estimating both probability that an event will occur and the probable magnitude of its adverse effects - provides an effective framework for determining relative urgency of problems and the allocation of resources to reduce risks - human risk assessment, ecological risk assessment de minimis level of risk acceptable risk - depends on population. size/age/health conditions - for carcinogens, general range of for noncarcinogens, HI = 1

49 Risk assessment process (1) Hazard identification - a review of all relevant biological and chemical information bearing on whether or not an agent poses a specific threat - site investigation (contamination levels ) (2) Exposure assessment - the process of measuring intensity, frequency and duration of exposure to an agent - exposure routes; ingestion, derma contact, inhalation - exposure pathway. from source to receptors. affected by interactions between pollutants and environmental media (soil, water, aquifer ) - exposure factors

50 (3) Dose-response assessment - need quantitative toxicity data. mainly from animal experiments. IRIS (US EPA) - acute, subchronic, chronic toxicity - dose-response relationship. generally, sigmoid-type curve. dose; mg-chemical/kg-body weight/day. response; mortality

51 Surrogates vs. human dose vs. dosage - dose; the total mass of chemical to which an organism is exposed - dosage; the chemical dose normalized for body weight, surface area,..

52 - for carcinogens. linear multistage model (USEPA). slope factor (SF), cancer potency factor (CPF). risk by a lifetime average dose (AD) of 1 mg/kg/day. lifetime risk = AD * SF (70 years)

53 - for noncarcinogens. assumes threshold. reference dose (RfD). unit; mg/kg/day (4) Risk characterization - excessive lifetime risk = exposure * toxicity - carcinogenic risk - noncarcinogenic risk uncertainty analysis - sensitivity analysis - Monte Carlo simulation record of decision (ROD) site-specific - site investigation - risk assessment - remediation goals - remediation technologies,,, uncertainty factors - individual sensitivity - extrapolation to humans - extrapolation from high dose to low dose - professional judgement

54 Carcinogenic risk calculation Noncarcinogenic risk calculation Ecological risk assessment (ERA) - much more difficult and time-consuming - needs lots of database regarding biota and toxicity - food chain vs. target species

55 [ 참고 ] Routes of Pb exposure in the environment Biotransformation of toxicant in body How to deal with risk? (example) "During a shower, toxic chemicals are released from the water, exposing the person to chemicals that may be up to 100 times greater than normal exposure. Is there a risk in showering? Should individuals be afraid of shower?

56 RBRS (Risk-Based Remediation Strategy) 를이용한환경관리 Tier 1: 보수적기본값을이용한위해성평가 ( RBSL) Tier 2: 오염현장특수성을반영한위해성평가 ( SSTL) Tier 3: Tier 2 보다세분화된위해성평가 (ERA 포함 ) 기존규제농도 vs. 오염농도 RBSL/SSTL vs. 오염농도

57 General procedure Site characterization Extensive soil, hydrogeological survey Conceptual Site Model Site-specific CSM Target risk & Clean-up goal Site-specific remediation Source identification Pollutants migration Potential exposure routes Potential receptors Land use Control effective exposure pathways Remediation area Available technology

58 1. Site characterization Risk assessment involves uncertainty Site-specific parameters & predictions More reliable assessment possible!

59 2. Conceptual site model: An example 1 st Source 2 nd Source Migration mechanism Exposure route Receptor Storage tank (UST, etc) Pipelines Operation facilities Waste storage facilities Others Surface soil Surbsurface soil Groundwater wind (dust) volatilization (outdoor air) volatilization (indoor air) leaching Soil ingestion /inhalation Air inhalation residential commercial workers others residential commercial workers others NAPLs free NAPL Drinking water residential commercial workers others Sediment, Surface water rain water flow Recreational use recreational others

60 3. Exposure route identification Air: Groundwater: inhalation of indoor/outdoor air groundwater ingestion inhalation of pollutants volatilized from groundwater Subsurface soil: leaching to groundwater inhalation of pollutants volatilized from subsurface Surface soil: soil ingestion, dermal contact, particle inhalation Target Clean-up Levels TCL air (mg/m 3 ) TCL groundwater (mg/l) TCL subsurface soil (mg/kg) TCL surfice soil (mg/kg)

61 오염농도에따른발암위해성산정 ( 예 ) 벤젠으로오염된토양으로부터주거지실내공기의흡입으로인해성인이입게되는위해성의산정 현장상황. 오염물질 ; 벤젠 ( 발암성 ). 수용체 ; 성인. 노출경로 ; 주거지실내공기흡입으로인한노출 입력변수. 벤젠오염농도 ; 1 µg/m 3. 벤젠의 SF inhalation ; kg-day/mg. 실내공기흡입률 ; 15 m 3 / 일. 노출기간 ; 30 년. 노출빈도 ; 350 일 / 년. 평균기간 ; 70 년. 체중 ; 70 kg 발암위해성 = (1 µg/m 3 ) *(350 일 / 년 )*(30 년 )*(15 m 3 / 일 )*(0.029 kg-day/mg) (70 kg)*(70 년 )*(365 일 / 년 )*(1,000 µg/mg) = 2.55 x 10-6

62 목표위해성에따른정화수준산정 ( 예 ) 벤젠으로오염된토양으로부터주거지실내공기의흡입으로인한위해성으로부터성인을보호하기위한목표정화수준의산정 현장상황. 오염물질 ; 벤젠 ( 발암성 ). 수용체 ; 성인. 노출경로 ; 주거지실내공기흡입으로인한노출 입력변수. 목표위해성 ; 벤젠의 SF inhalation ; kg-day/mg. 실내공기흡입률 ; 15 m 3 / 일. 노출기간 ; 30 년. 노출빈도 ; 350 일 / 년. 평균기간 ; 70 년. 체중 ; 70 kg 목표정화수준 = (10-6 )*(70 kg)*(70 년 )*(365 일 / 년 )*(1,000 µg/mg) (350 일 / 년 )*(30 년 )*(15 m 3 / 일 )*(0.029 kg-day/mg) = 0.39 µg/m 3

63 주요노출인자기본값 (1) 토지이용용도별 Parameters Definition (units) Residential Commercial/ Industrial ATc 발암성물질에대한평균노출기간 (years) 70 (73.5) 70 ATn 비발암성물질에대한평균노출기간 (years) BW 성인평균체중 (kg) 70 (60.0) 70 ED 노출기간 (years) EF 노출빈도 (days/years) 350 d/yr 250 d/yr IR soil 토양섭취률 (mg/day) IR air (indoor) 일일실내공기흡입률 (m 3 /day) IR air (outdoor) 일일실외공기흡입률 (m 3 /day) IR w 일일물섭취량 (L/day) 2 (1.26) 1

64 주요노출인자기본값 (2) 토지이용용도별 Parameters Definition (units) Residential Commercial/ Industrial M 토양 - 피부접촉계수 (mg/cm 2 ) SA 피부표면적 (cm 2 /day) RAF d 피부를통한흡수계수, BTEX/PAHs chemical-specific RAF o 섭취를통한흡수계수 1 1 LFsw 토양 - 지하수용출계수 chemical-specific (mg/l-h 2 O)/(mg/kg-soil) VF 휘발계수 chemical-specific 토양 - 공기 (mg/m 3 -air)/(mg/kg-soil) 지하수 - 공기 (mg/m 3 -air)/(mg/l-h 2 O)

65 Risk variation by exposure routes (e.g., benzene) groundwater ingestion Risk: 9.87 µg/l RBSL = TR*BW*AT CFP oral *GW ingestion rate *EF*ED Exposure factor Exposure route Toxicity value groundwater dermal contact Risk: 241 µg/l RBSL = TR*BW*AT CFP dermal *Skin area*skin absorption rate *EF*ED

66 수돗물과생수...

67 (Lecture 12) ESP Ch 19. Soil and groundwater remediation

68 Site characterization - type, location, amount - NAPL (free product) present? - remedial options

69 Remediation technologies - principles: containment, removal, treatment Containment technologies - physical barrier - hydraulic barrier - immobilization (solidification/stabilization) Removal technologies - excavation - pump-and-treat - soil vapor extraction (SVE); permeability - air sparging,

70 In situ treatment - bioremediation - chemical treatment: Fenton s reagent Others - soil washing - magnetic separation - electrokinetic treatment

71 Phytoremediation - accumulation; hyperaccumulators - stabilization. root exudates. rhizobacterial activity - plants as hydraulic barriers

72 Monitored natural attenuation (MNA) - restricted application only where appropriate and needed - prerequisites. Are MNA process occurring at the site?. Is the magnitude and rate of MNA sufficient to accomplish the remediation goal? long-term site monitoring is important geochemical indicators be protective to human health and the environment

73 Monitored Natural attenuation (MNA) "needs to show favorable processes are ongoing at the site plume management technique - usu. for ground water remediation rationales - ground water (aquifer) contaminated by DNAPLs -> residual NAPLs limitation of conventional means (e.g., pump-and-treat) - plumes; relatively short, not expanding, and little or no risk * Plume life cycle. expanding: residual source present. mass flux of contaminants exceeds assimilative capacity of aquifer. stable: insignificant change. remediation processes are controlling plume length. shrinking: residual source nearly exhausted. remediation processes significantly reduce plume mass. exhausted: average plume conc. very low (e.g., 1 ppb) and unchanging over time key factors determining applicability. plume stability. required time frame.... site information (monitoring factors for MNA)

74 Attenuation processes 1) dispersion; a. mixing process caused by - ground water movement (velocity variations) in porous media - aquifer heterogenicities (--> flow velocity and path) b. results in sharp edge and dilution of solutes at the edge 2) sorption; represented by retardation factor 3) degradation; biotic and abiotic (hydrolysis of chlorinated solvents...) 4) dilution insignificant factors a. diffusion - molecular mass transfer by concentration gradients - can occur in the absence of velocity - only a factor in the case of very low velocities (tight soil, clay liner) or of mass transfer involving very long time periods b. volatilization c. advection; movement of contaminants along with flowing ground water

75 Geochemical indicators a. consumption of electron acceptors used for oxidative reactions (e.g., dissolved oxygen, nitrate, sulfate in the plume area...) b. production of metabolic by-products (e.g., ferrous iron, methane, c-dce, VC, ethene...) c. presence of appropriate redox/microbial environments (e.g., dissolved hydrogen...)

76 Attenuation rate calculation a. bulk attenuation rate (k); just indicates whether conc. declines or not... b. biodegradation rate (λ); attenuation rate model FATE V... Risk-based corrective action (RBCA); developed by ASTM (1995) a. identification of applicable risk factors on a site-specific basis b. identification of potential mechanisms for exposure on a site specific basis SSTL = RBEL x NAF SSTL; site-specific target level NAF; natural attenuation factor (rate; k) RBEL; risk-based exposure limit at POE (usu. standard level..) POE; point of exposure if, measured or calculated source conc. > SSTL-> remediation required if not, no further action required (based on RBCA) monitoring!!! (K = -slope*seepage velocity)

77 Summary: Remediation technologies

78 오염지역정화및복원기술 (1) 1) 생물학적정화기술 ( 개요 ) 정의및원리 ( 미 ) 생물의오염물질분해능력을이용하여오염토양또는지하수를처리하는기술 가수분해, cleavage, 산화, 환원, 탈수소화, 탈염소화, dehyrrohalogenation, 치환등의효소촉매반응 공대사 (Cometabolism) : 다른물질을분해하는미생물의효소에의하여우연히일어나는분해과정으로탄소원이나에너지원으로이용되지않음 전자수용체에따라호기성 (O 2 ), 혐기성 (NO 3-, SO 4 2-, CO 2 ), 발효 ( 유기물 ) 로구분 장단점 장점현장처리 (In-situ/On-site) 가능오염성분의궁극적제거비교적저렴타기술과연계용이부지 / 토양특성변형최소화주민친화성양호 단점일부오염성분의난분해성처리효과가부지특성의영향받음처리 / 사후감시기간이김미지 / 독성중간물질생성가능성기술의신뢰성에대한인식문제기술집약적

79 오염지역정화및복원기술 (2) 2) 생물학적정화기술 ( 원리 ) 효소촉매반응 Enzyme Reaction Hydrolysis : Exoenzyme에의해서이루어지는반응. 물이첨가되어유기물분자가간단한형태로끊어지는반응 Cleavage : 탄소-탄소의단일 / 이중결합이끊어지는반응. Oxidation : Electrophilic form을이용하여유기물이분해되는반응 Reduction : Nucleophilic form이나직접적인전자전달을이용하여유기화합물이분해되는반응 Dehydrogenation : 수소원자 2개를잃음으로써두개의전자와두개의수소를잃는산화환원반응 Dechlorination : 염소계화합물이전자수용체로이용되어염소가떨어지고수소원자가붙는반응 Dehydrohalogenation : 유기화합물로부터수소원자와염소원자가떨어지는반응 Substitution : 한원자가다른원자로치환되는반응 공대사 Cometaboilsm 어떤기질을분해하는미생물의효소가낮은 기질특이성때문에에너지생산이나탄소동화 등의생장과정과관계없이다른기질전환 오염물의분해, 독성감소가능 염소계지방족화합물, 다환성방향족화합물 등의주요분해기작 전자수용체 Electron Acceptor 호기성산소 O 2 혐기성 Nitrate ( 질산 ) NO 3 - Sulfate ( 황산 ) SO 4 2- Carbon dioxide ( 이산화탄소 ) CO 2 발효 기질을전자공여체와전자수용체로동시에이용하며지극히혐기적인조건에서발생

80 오염지역정화및복원기술 (3) ( 참고 ) 생물학적정화기술적용사례 생물정화대상오염물질 ( 미국 ) Superfund 정화기술적용사례 ( 94) 유류크레오소트류용매류기타 ( 살충제등 ) 29% 29% 16% 26% 생물학적정화소각고형화 / 안정화 SVE 9% ( 원위치 4%, 지상 5%) 30% 26% 17% 열탈착 6% 토양세척 6% 기타 ( 탈염화등 ) 6%

81 오염지역정화및복원기술 (4) 3) 생물학적정화기술 ( 주요오염물의분해 1) 1 Aliphatic Hydrocarbons 지방족탄화수소 Aliphatic Hydrocarbon Monooxygenase or Dioxygenase O 2 토양에분해미생물多호기성분해수분 50% 이상 ph 8.5 이하 종류 : Alkanes, Alkenes, Alcohols, Aldehydes, Ketones, Acids 분해되는정도 Long Chain (C9 이상 ) > Short Chain Straight Chain > Branched Chain Saturated Hydrocarbons > Unsaturated Hydrocarbons

82 오염지역정화및복원기술 (5) 3) 생물학적정화기술 ( 주요오염물의분해 2) 2 Aromatic Hydrocarbons 방향족탄화수소 BTEX Benzene 생분해 Dihydrodiol Ring Fission Dioxygenase Catechol 치환기의위치, 수, 종류에따라분해성차이 호기성분해 탈질, 망간환원, 철환원, 황산염환원, 메탄생성등혐기조건에서도분해 전자수용체의이용가능성과산화환원전위에따라결정

83 오염지역정화및복원기술 (6) 3) 생물학적정화기술 ( 주요오염물의분해 3) 3 Polycyclic Aromatic Hydrocarbons 다환성방향족탄화수소 Ring Fission Dioxygenase Naphthalene 생분해 Ring Fission 벤젠고리와치환기의수, 종류, 위치에따라분해성차이 2~3 rings : 호기성분해 & 혐기성분해, 비교적빠른속도 4 rings 이상 : 큰분해저항성가짐 용해도낮을수록벤젠고리, 치환기복잡할수록분해어려움

84 오염지역정화및복원기술 (7) 3) 생물학적정화기술 ( 주요오염물의분해 4) 4 Chlorinated Aliphatic Hydrocarbons 염소계지방족탄화수소 Reductive Dehalogenation PCE, TCE 생분해 Vinyl Chloride PCE, TCE 보다독성이큼 에너지원으로산화 / 호기조건에서공대사 / 혐기적탈염소화 대부분공대사에의존 ( 호기 ) Oxygenase, Dehalogenase, Hydrolytic dehalogenase

85 오염지역정화및복원기술 (8) 3) 생물학적정화기술 ( 주요오염물의분해 4) ( 참고 ) Cometabolism of TCE by Methane Monooxygenase MMO Methane Methanol MMO TCE TCE epoxide Methanotrophic Bacteria 가생성하는 MMO 의기질특이성부족으로 TCE 공대사가일어남 메탄농도가높으면 MMO 에대하여 TCE 와메탄이경쟁할수있음 PCE 는많이산화된상태이므로공대사에의해서도분해되지않음. 환원으로만분해가능

86 오염지역정화및복원기술 (9) 3) 생물학적정화기술 ( 주요오염물의분해 5) 5 Chlorinated Aromatic Hydrocarbons 염소계방향족탄화수소 정화대상물질 - Chlorophenol, Chlorobenzene, Chloroaniline, PCBs, Pesticdes PCBs : Polychlorinated Biphenyls, 탄소와염소의무게비로구분하며용해도가작아서지하수보다는토양오염 염소의치환특성, 수, 위치에의해분해도결정 호기조건에서공대사 (cometabolism) 에의해분해 혐기조건에서탈염소화 (dechlorination) 에의해분해 메탄생성조건에서효율적

87 0 오염지역정화및복원기술 (10) 4) 생물학적정화기술 (Kinetics & Rates) substrate concentration time 2차 1차 0차 Thermodynamics 반응 ( 분해 ) 의가능성문제 과학자의영역 Kinetics 반응 ( 분해 ) 속도의문제 농도, 미생물, 환경조건의영향 공학자의영역 dc = dt dc = dt dc = dt k kc 2 kc 0 차반응 : 모든기질이이용가능한상태. 대수적감소 1 차반응 : 속도가기질농도에비례 2 차반응 : 실제와가장비슷 / 유사일차반응

88 오염지역정화및복원기술 (11) 5) 생물학적정화기술 ( 환경조건의영향 ) 미생물 Bacteria 호기성 vs. 혐기성 독립영양 vs. 종속영양 토양입자표면에붙어있음 지표가까이에많이존재 ph 세포기능, 세포막을통한물질이동, 효소반응의평형, 세포내에너지생산등에영향 자연환경 ph 5~9 일반적으로최적 6.5~7.5 영양분 C, H, O, N 이 95%, P, Ca 등이 3.5% Bacteria 화학식 C 5 H 7 O 2 N 질소, 인등이부족 미생물사멸로원소순환 Growth factor 필요 수분 오염물질의생물학적이용성, 기체전달, 오염물질의위해성, 미생물의움직임과생장, 미생물종의분포에영향 중력수비율, FC 로측정 온도 온도가증가할수록생화학반응속도증가 최적온도 Psychrophile(15±5 ) Mesophile(25~40 ) Thermophile(40 이상 ) 산화환원전위 EH 로표현 (+) 는산화환경, (-) 는환원환경 오염물의분해여부결정 특정산화제 / 환원제의농도가미생물대사활성에영향

89 오염지역정화및복원기술 (12) 6) 생물학적정화기술 1 Biodegradation 생분해법 개요 지중에존재하는오염물질을분해하는능력을가진미생물을이용하여토양및지하수내의유기오염물질을분해하는기술 처리물질 유류탄화수소, 용매, 살충제, 기타유기물 영향인자 오염물의흡착성, 화학적반응성, 생분해가능성, 오염물의농도, 오염물질과 미생물의접촉여부, 토양의특성과성상, 산화환원전위, 미생물활성에영향을 미치는독성물질의존재여부

90 오염지역정화및복원기술 (13) 6) 생물학적정화기술 1 Biodegradation 생분해법 Biostimulation Bioaugmentation 산소공급 산소발생물질공급 전자수용체공급 미생물공급 공기주입 : 저비용, 적용용이, 낮은산소전달률 산소주입 : 고비용, 높은산소전달률 영양분공급 질소, 인, 칼륨, 마그네슘등양분공급 : 주입구주변 biofouling 가능성, ph 변화주의 과산화수소 : 취급용이, 자체독성 MgO 등산소발생물질주입 산소녹아있는물 1 차기질공급 아세테이트, 에탄올등공급 : 혐기적공대사능향상, 환원적탈염소화촉진 질산 : 탈질활성화, 혐기조건지역까지정화가능, 질산나트륨오염기준및독성고려필요 기타 메탄, 암모니아등영양염류기체로공급 : CAH 공대사능향상 혐기화 : 설탕주입 토착미생물개체군을지상에서성장시킨것이나대상오염물질을분해할수있는미생물을토양에접종 ubiquity principle & 자생미생물의오염물질분해효소증진 주입미생물이동, 분포및현장적응도문제

91 오염지역정화및복원기술 (14) 6) 생물학적정화기술 2 Bioventing 생물학적통풍법 개요 오염된불포화지반에산소를공급함으로써토양에함유된유류탄 Delivery of Nutrient Valve Monitoring Well Property Boundary 처리물질 화수소생분해를활성화하는기술유류탄화수소, 비염소계용매, 살충제등유기화합물질 Working GW Level NAPL Plume Groundwater Recirculation System Vadose Zone Saturated Zone 영향인자 오염물의생분해성, 충분한산소, 토양의 ph와온도, 통기성, 수분함량및영양분 장점 낮은압력으로충분한산소공급가능미생물분해외에도휘발성물질제거가능 설계및운전 현장지질조건고려한관정의수와위치설계토양함수비와영양분에대한정기적모니터링필요 단점 무기물흡착, 흡수, 응집, 농축가능포화대에서는 Air Sparging 등병행필요방출가스처리시설필요무기물분해어려움

92 오염지역정화및복원기술 (15) 6) 생물학적정화기술 3 Composting 퇴비화 개요 미생물에적정조건을제공함으로 써혐기성분해또는발효를이용 하여오염물질을생물학적분해 처리물질 유기물또는생분해가능한물질 영향인자 오염물질의농도, 토양의형태, 영 양분, 미생물의분해능력 한계 넓은부지필요 팽화재사용으로전체부피증가 중금속분해불가능

93 오염지역정화및복원기술 (16) 6) 생물학적정화기술 4 Controlled Solid Phase Biological Treatment 개요 토양을굴착하여토양개선재와혼합하고침출수처리장치, 폭기장치를설치하여생분해를활성화하는공법 처리물질 한계 유기물또는생분해가능한물질토양굴착필요 ( 비용 ) 각종장치설치필요넓은부지필요긴처리기간

94 오염지역정화및복원기술 (17) 6) 생물학적정화기술 5 Landfarming 토양경작법 오염토양을굴착 하여정기적으로 개요 혼합해줌으로써 호기적생분해를 유도하는공법 처리물질 유류탄화수소 살충제 영향인자 오염물질의농도와독성 무기물질의존재여부 토양의유기물함량 한계 시설설치를위한넒은부지필요배출가스정화시설필요상대적으로긴정화기간중금속등무기물분해불가능

95 오염지역정화및복원기술 (18) 6) 생물학적정화기술 6 White Rot Fungus 리그닌을분해 하는효소를가 개요 진미생물을이용하여다양한 유기물질을분 해하는공법 TNT, RDX, 처리물질 HMX 등폭약류 DDT, PAHs, PCBs, PCP 등유기오염물 영향인자 오염물질의농도토착미생물군의박테리아수오염물질의화학적흡착다른오염물질이나토양특성

96 오염지역정화및복원기술 (19) 7) 물리화학적정화기술 1 Air Sparging 공기분무법 휘발, 생분해를이용하여포화대내의용 개요 해상, 자유상, 흡착상오염물질정화하는 기법 헨리상수 10-5 atm-m 3 /mole 이상 처리물질 증기압 0.5~1.0 mmhg 용해도가낮은물질 (BTEX, PCE, TCE 등은저효율 ) 호기성생분해가잘일어나는물질 영향인자 대수층종류 ( 자유면 vs. 피압 ) 토양종류 ( 입도분포 / 균질 vs. 불균질 ) 지하수면깊이, 투수성, 통기성 ph, 온도, 산소, 수분함량, 영양분유기탄소함량오염물의휘발성, 용해도및생분해성 한계 피압대수층, 낮은투수성지반불가능불균질매질에적용어려움오염물확산가능성, channeling 현상주변구조물의안정성에영향휘발성큰오염물적용어려움두께 1ft 이상의 NAPLs 효율낮음

97 오염지역정화및복원기술 (20) 7) 물리화학적정화기술 1 Air Sparging 공기분무법 사전조사 오염물의종류, 위치, 분포양상대수층종류, 지하수면깊이, 토양의종류와특성등수리지질학적조건불균질성에따른 air plume 분포양상주입률에따른 air channel 분포양상 Pilot test ( 압력, 용존산소량, 지하수면, 오염물농도변화관측 ) 공기분포양상및영향반경오염물의휘발률과산소공급률 Horizontal Trench Sparging 오염지대깊이가 30ft 이하일때낮은투수성지반에적용 타기술과병행 In-Well Air Sparging 공기주입에비적합한지역에서 casing 을이용, 공기흐름형성 목표정화수준및정화시간주입형태 (continuous vs. pulsed) Biosparging Vapor Recovery via Trenches 설계요소 Standard vs. Site specific design 오염물질종류주입정, 추출정, 관측정위치및개수주입정의 clogging 여부 생분해만을목적으로하여포화대에낮은유속으로공기주입 얕은지하수대, 작은입자로구성된지역에갇힌증기제거

98 오염지역정화및복원기술 (21) 7) 물리화학적정화기술 2 Soil Vapor Extraction (SVE) 토양증기추출법 VOC/SVOC 로오염된불포화대에주 입정과추출정을설치하고깨끗한공 개요 기를지중에넣은뒤진공압을이용해 공기를빨아들임으로써휘발성오염물 질이공기와섞여배출되도록하는공 법 처리물질 불포화대의휘발성 NAPL 지중에잔류하거나 (trapped), 자유상태 (free-product) 로존재하는 NAPL 추가로주입되는시약이없음 증기압 0.5mmHg 이하오염물부적합 부작용이거의없음 균질 / 투수성불포화지반에적용가능 장점 설치용이, 비용저렴, 신속일반굴착보다깊이정화 한계 점토지반에서는파쇄공법병행필요중금속, DNAPL, PCBs, Dioxins 부적합 공기주입을통한생분해활성화 Bioventing 등으로추가정화필요 접근하기어려운지역에적용가능 방출가스처리시설필요

99 오염지역정화및복원기술 (22) 7) 물리화학적정화기술 2 Soil Vapor Extraction (SVE) 토양증기추출법 사전조사 영향인자 설계요소 오염물휘발성, 증기압, Henry 상수오염물공기 / 물분리계수, 용해성오염물분포깊이, 형상, 면적지반공기투과성, 투수성, 공극률유기탄소함유량, 함수비, 입도분포지반과지역내로의접근성오염물농도, 휘발성, 분포및면적, 적용가능한대수층깊이, 토양형태와성분, 수분 / 유기물함량, 공기투과도, 충분한산소와영양분의존재유무공기추출률 / 량, 영향반경을고려한추출정의수, 간격과형상, 세정시간, 방출가스처리, 지하수위변동의영향을고려한스크린범위결정, 물침투제어 SVE 적용전사전양수 지하수위저하로 SVE를통한정화영역확장 공기송풍기설치 송풍기로공기및오염물질의흐름을원활하게유도 타기술과병행 표면에불투수성장벽설치 공기의순환주기가너무짧아지는것을방지 Air Sparging 지하수대상부의오염물질을휘발시켜함께정화처리

100 오염지역정화및복원기술 (23) 7) 물리화학적정화기술 3 Pump and Treat (P&T) 양수처리법 개요 오염지역에추출정을설치, 오염된지하수를진공펌프로양수하여물리화학적혹은생물학적처리를거쳐정화한후다시지하수로유입시키는순환과정 장점 한계 안정한 NAPL 활성화로효율적제거지하수위저하로불포화대에남은 LNAPL 에타기술적용지하수위경사에따른 LNAPL 추출용이 DNAPL pool 직접제거용이적용초기에오염물신속히제거가능지하수위저하를위한다수의추출정필요비균질, 저투수성지반에서비효율적 Tailing Effect로타기술과병행필요 Tailing Effect 지하수대간극수에용해되어있는오염물과달리토양입자에흡착되거나간극속에갇힌용해되지않은상태의오염물이장기간배출되지않는현상

101 오염지역정화및복원기술 (24) 7) 물리화학적정화기술 4 Soil Washing / Flushing 토양세척 / 수세법 물이나다른수용체또는비수용액과같은 개요 적절한용매를사용하여지반내오염물질을 씻어내는방법 처리물질 SVOC, 중금속등과특정 VOC, 유류오염물, 살충제, 방사능오염물을포함한무기물, 광범위한유기및무기오염물 오염물의농도, 특성, 깊이, 형상, 면적, 세척 사전조사 용매와지반사이오염물의분리성, 지반의특성에미치는세척액의영향, 시스템설치와침수에대한현장적합성, 지역내특수지반의유량과흐름방향, 지반과지역의접근성 장점 성공시추가공정불필요, 오염물의영구적제거, 투수성지반에적합, 중간정도의비용 영향인자 세척용액과오염물의접촉, 오염물에따른적절한용액의선정, 오염물의지반흡착계수, 지반의투수계수 단점 세척용액의독성, 오염물확산가능, 계면활성제토양부착으로공극감소, 토양 / 계면활성제상호작용으로오염물유동성감소

102 오염지역정화및복원기술 (25) 7) 물리화학적정화기술 4 Soil Washing / Flushing 토양세척 / 수세법 ex-situ Soil Washing 오염토양을굴착하여부순다음세척제로오염물분리후정화된토양은현장에되돌리는방법사질토 + 휘발성오염물에적합휴믹물질많으면전처리필요고농도오염물전처리필요세척유출수응집제필요굴착및후처리필요 in-situ Soil Flushing 오염지역에세척용액을주입, 추출정 / 배수관으로배수후추출된오염수를처리하여정화지역에재순환오염물용해, 유제형성, 세척용액과화학반응세척용액집수시설필요 세척제 세척용액 대상오염물 계면의자유에너지를낮추고성질을변화 물 수용성물질 시켜오염물을토양으로부터분리, 용해시 산성용액 금속, 염기성유기물질 키는역할, 정화작업에악영향을미칠수있 염기성용액 금속, 페놀, 킬레이트화합물 으므로신중하게선택 계면활성제 흡착된소수성유기오염물

103 오염지역정화및복원기술 (26) 7) 물리화학적정화기술 5 Hydraulic and Pneumatic Fracturing 수압 / 공기파쇄공법 개요 공정과정 영향인자 장점 저투수성지반에압축공기나액체를오염지역에주 입하여기존균열을확장하고 2 차균열망 과 Channel 형성하여투수성과영향반경을증가시 킴으로써타정화공법의효율을증대시키는기술 목적심도까지시추 원하는 fracture 지점에 injector 설치 Packer 로 1 2ft 를밀폐 밀폐된공간에압축공기약 30 초간주입 다음지점 injector 설치및위과정반복 Fracture cycle 은약 15 분, 하루한개의시추공에 fracture 생성 Injection flow rate, 토양의점착력, 인장강도, 상재압, 토양입자크기, 토양액소성한계, 일축압축강도, 점성, 주입기체 / 액체의종류 투수성증가로인한 SVE 영향반경증가, 산소 / 영양분등공급으로미생물분해촉진, 철을주입함으로써 CAHs 환원적탈염소화유도, 유리화법 / 동전기에서전극으로사용가능

104 오염지역정화및복원기술 (27) 7) 물리화학적정화기술 6 Solvent Extraction 용매추출법 개요 처리물질 영향인자 한계 오염물질을분해하지는않지만토양, 슬러지, 퇴적물질로부터오염물질을분리시켜부피를감소시키며유기화학물질을용매로사용하는공법 PCBs, 휘발성유기물질, 할로겐용매, 유류와같은유기오염물질 토양의입경, ph, 분배계수, 양이온치환능력, 유기물함량, 수분함량금속, 휘발성물질, 점토, 복합오염물질의존재여부 수분함량이높으면공정에악영향, 청정제 / 유화제존재시추출반응에악영향, 추출용매독성, 고분자유기물질과친수성물질에부적합

105 오염지역정화및복원기술 (28) 7) 물리화학적정화기술 7 Thermal Desorption 열탈착공법 개요 처리물질 영향인자 설계인자 토양에열을가해오염물을증발시켜가스 를발생시킨후, 가스를처리장치로수집하 여처리하는공법 HTTD: 금속 ( 수은등 ) 처리가능 Coal tar, 목재, creosote, (SVOCs, PAHs, PCBs, 농약등 VOCs) LTTD: 가능비염소계휘발성유기화합물, 연료, (SVOCs) 토양점착력, 입도분포, 함수비, 열용적율, 유기물농도, 오염물농도, 끓는점범위, 증기압, 열에대한안정성, Dioxins 발생가능성 현장위치와조건, 오염물의수직적분포에따른고려사항, 목표정화수준, 탈수여부, 처리된토양의처리문제

106 오염지역정화및복원기술 (29) 7) 물리화학적정화기술 8 Solidification/Stabilization 고형화 / 안정화 개요 처리물질 영향인자 한계 화학적, 물리적인처리를통해서유동 성을감소시킴으로써위해성을낮추 는오염처리방법 방사능물질을포함한무기물질 토양의입경, 수분함량, 중금속농도, 황함유량, 유기물농도, 압축강도, 투수성, 토양의물리화학적특성 In-Situ: 깊이에따라특정장치설치필요, ex-situ에비해시약주입 / 혼합이어려움, 처리효율확인 Ex-Situ: 부피증가 ( 유기물부피의 2 배까지 ), 휘발성유기물질은고정화되지않음. 혼합되면처리시간이길어짐 Emissions, Dust and VOC Control ex-situ Auger Caisson 물리적으로안정한상태의물질내에서고형화하나안정화제를첨가하여화학반응에의해오염물질의유동성을감소시키는방법후처리필요 Reagent and/or Binder Injector Head in-situ 오염지역에약품을주입하여고형화 ( 이동성감소 ), 안정화 ( 독성물질이동성감소및처리 )

107 오염지역정화및복원기술 (30) 7) 물리화학적정화기술 9 Vitrification 유리화 오염토양및슬러지를전기적으로용 개요 처리물질 영향인자 한계 융시킴으로써용출특성이매우적은결정구조로만드는공법 VOCs, SVOCs, Dioxins, PCBs 토양의입경, 수분함량, 유기물함량, 밀도, 투수성, 물리화학적특성, 입도분포가스로부터입자나다른오염물을제거하는방출가스처리장치필요자갈비가 20% 가넘으면부적합재오염방지수단필요오염물확산가능유리화물질제거후토양재이용가능

108 오염지역정화및복원기술 (31) 7) 물리화학적정화기술 10 Chemical Oxidation/Reduction 화학적산화 / 환원 개요 오존, 과산화수소, 차아염소산염, 그리고이산화염소등을이용하여오염물질을화학적 으로더안정하고, 유동성이없으며, 비활성물질로변화시키는반응을이용하는공법 처리물질 주로무기오염물을대상 VOCs, SVOCs, 유류탄화수소등의비염소계물질에는비효과적 한계 오염물질과사용된시약에따라불완전산화혹은중간물질이형성될수있음시약이많이필요하므로오염물질의농도가높을때는비경제적토양에는기름과그리스성분이적어야함 영향인자 토양의수분함량, 알칼리금속, 부식토함량, 총유기할로겐화합물 오염물질의종류와형태, 토양입자의입경, 용매의용해도오염물의농도구배 약품의종류

109 오염지역정화및복원기술 (32) 7) 물리화학적정화기술 11 Incineration 소각 개요 처리물질 산소를공급하여유기물질을연소 / 분해하 는열적으로파괴하는공정, 토양내의유 해유기오염물을 871~1,204 의고온으 로소각하여이산화탄소, 수증기, 황화수 소, 할로겐화수소로분해 폭발성물질, 염소계탄화수소, PCBs, Dioxins 한계 불완전연소로중금속, 독성재생성가능오염토양투입량에따라소각로의크기가커지므로처리비용증가금속은염소, 황과반응하여유해물질생성가능, 가스정화장치필요저온에서 Na, K 재를형성하고점착성이강한입자를형성하여덕트를막히게함

110 오염지역정화및복원기술 (33) 8) 기타정화기술 1 Phytoremediation 식생정화법 개요 오염토양 / 지하수정화를위하여식물이용하는방법으로대부분의정화는식물뿌리가뻗는부분의토양층인 rhizosphere 에서발생 중금속, 과잉영양분 ( 질산, 암모니아, 인산 ), 처리물질 소수성오염물 (BTEX, 염소계유기용매, PAHs, nitrotoluene, ammunition wastes), 제초제, 유기용매, 동위원소 장점 한계 비용저렴, 미관상장점오염물누출최소화, 토양안정화적절한기후조건, 장기간의공정관리필요뿌리보다깊은곳의오염물추출불가능 설계및운전 대상오염물의추출, 흡수, 화학적분해에적합한식물의종선택오염물이궁극적으로제거되는것이아니므로식물소각등후처리필요

111 오염지역정화및복원기술 (34) 8) 기타정화기술 2 Monitored Natural Attenuation 자연저감법 개요 주요기작 적용여부판단 장점 오염물의자연적인정화나이동지체를이용하는방법. 방치와는다른개념. 다른적극적인정화방법에비교하여합리적인시간내에목표정화수준에도달할수있는자연저감과정 미생물분해, 분산, 희석, 흡착, 휘발, 방사성붕괴, 화학적 / 생물학적안정화, 변형, 파괴 Protocol: 작업에관련된규약, MNA 를적용하기위해고려해야할사항 Pattern: 오염물의상황과형태에따른 MNA 사용여부판단 비용경제적, 장비등이거의불필요감시강도에따른유연한시공비

112 오염지역정화및복원기술 (35) 8) 기타정화기술 3 Permeable Reactive Barrier 투수성반응벽체 개요 오염된지하수가흘러가는곳에오염물을처리할수있는수직투수성반응벽체를설치하여오염지하수가벽체를통과하면서생물학적또는화학적으로분해되도록하는현장구조물 오염물질오염원구성요소반응물질반응기작 염화유기물 영양염류 중금속 공단지역, 주유소, 정유공장등의산업시설및군사시설 매립지침출수, 축산폐수 TCE, PCE Fe 0, GP dust, HRM Sludge 탈염소화 PCBs Pd/Fe Bimetal, Nanoscale Fe 촉매적탈염소화 T-N, Ammonia Zeolite 이온교환, 흡착, 철에의한탈질 축산폐수 T-P Wastelime, SM Slag 흡착및침전 산업및군사시설, 폐광산산성폐수 Cr6+ HRM Sludge, SM Slag 환원 Cd, Hg, Mn, As, Cu, CN, Pb Zeolite, SM Slag 이온교환, 흡착 황산염폐광산산성폐수 Sulfate AlOH, SM Slag, Wastelime 침전, 중화

113 오염지역정화및복원기술 (36) 8) 기타정화기술 4 Electrokinetics 동전기법 개요 처리물질 지층속에전극을설치한후전류를가하여지층의물리 화학적및수리학적변화를유도한후전도현상을일으켜오염물질을이동추출 제거하는기술전기삼투 / 전기이동 / 전기영동 중금속, 핵종, 페놀, TCE, 톨루엔, 기타유기및무기물 물질이동기작 전기삼투흐름에의한간극수이류 (advection) 외적으로제고또는내적으로생성된수위차에의한간극수이류 (hydro-potential) 농도경사에의한확산 (diffusion) 전기경사에의한이온이동 (migration) 영향인자 점토의완충능력, 양이온교환능력, 유기물함량, 포화대내점토광물표면의전하밀도, 양이온물질의특성과농도, 유기질 / 탄산염의존재, ph