4A10 Construction Research & Innovation BioGeoChemistry Professor Mark Dyer TrinityHaus

Hanworth Case Study – Plan (after Dyer 2004) Diesel Storage Tank (BTEX) Benzene Toluene Ethyl Benzene Xylene Solvent Bath (TCE) Trichloroethene and Metal Salts CN- Cr VI

MNA : Natural Processes Source Groundwater Flow Monitoring boreholes oDispersion & Diffusion oSorption oBiodegradation LNAPL’s DNAPL’s Monitored Natural Attenuation (MNA) Target

Evidence of Natural Attenuation Evidence of NATURAL ATTENUATION oReduction of aqueous concentration with distance (or gaseous) oShrinking of plume with time oAppearance of biodegradation by-products (e.g. dechlorination of TCE) oDepletion of alternative electron acceptors (e.g. oxygen, nitrate, ferric iron, sulphate ions) Plume Source

No 1 : Evidence of Biodegradation Evidence of NATURAL ATTENUATION oAppearance of biodegradation by-products (e.g. dechlorination of TCE Plume

Eg. Biodegradation at Philips Factory Zwolle NL Chlorinated Hydrocarbons PCETCEcis-DCEVCEthene Aqueous concentration (µg/l) 68,00017,00032,0006,8253,451

Zwolle NL: Evidence of strong biodegradation Presentation of results in relative molar concentration

No2 Depletion of Alternative Electron Acceptors Evidence of NATURAL ATTENUATION oDepletion of alternative electron acceptors close to source (e.g. oxygen, nitrate, ferric iron, sulphate ions) sulphate nitrate ferric iron oxygen Gradual reduction in redox potential towards the source of pollution due to consumption of electron acceptors by bacteria

Depletion of alternative electron acceptors nitrate ferric iron Time Eg. Progressive depletion of electron acceptors sulphate ferric iron nitrateoxygen

No 3 Reduction in Aqueous Concentration Evidence of NATURAL ATTENUATION oReduction of aqueous concentration with distance (or gaseous) oShrinking of plume with time Plume Source

Mechanisms:- Advection, Dispersion and Sorption Distance or time from source Relative Concentration C/Co ADVECTION

Advection, Dispersion and Sorption Distance or time from source Relative Concentration C/Co DISPERSION by tortuously & friction through pore space resulting in relative reduction but no overall reduction in mass of pollutant

Advection, Dispersion and Sorption Distance or time from source Relative Concentration C/Co SORPTION onto soil and organic matter resulting in an overall reduction of aqueous concentration & retardation

Advection, Dispersion and Sorption Distance or time from source Relative Concentration C/Co SORPTION onto soil and organic matter resulting in an overall reduction of aqueous concentration & retardation Adsorption onto the surface of clay particles or negative charged carboxylic acids (C-COOH) or alcohols (C-OH) for humus colloid Absorption into organic matter (humus)

Advection, Dispersion and Sorption Distance or time from source Relative Concentration C/Co SORPTION onto soil and organic matter resulting in an overall reduction of aqueous concentration & retardation Adsorption onto the surface of clay particles for metal ions Absorption into organic matter for organic pollutants (BTEX)

Adsorption Isotherms C s (  g/g) C eq (  g/L) Linear Langmuir C i C eq Cs = [(C i – C eq ) x volume of liquid]/weight of soil

Hypothetical Batch Test Ci (  g/L)Ceq (  g/L) Wt (g) Cs (  g/g) Ci Ceq Cs = [(Ci – Ceq) x volume of liquid]/weight of soil Cs = [(250 – 77.3) x 0.2]/20.42 = 1.69 (  g/g) 200 ml of influent

Hypothetical Batch Test Ci (  g/L)Ceq (  g/L) Wt (g) Cs (  g/g) Ci Ceq Cs = [(Ci – Ceq) x volume of liquid]/weight of soil Cs = [(250 – 77.3) x 0.2]/20.42 = 1.69 (  g/g) 200 ml of influent

Hypothetical Batch Test Ci (  g/L)Ceq (  g/L) Wt (g) Cs (  g/g) Ci Ceq Cs = [(Ci – Ceq) x volume of liquid]/weight of soil Cs = [(250 – 77.3) x 0.2]/20.42 = 1.69 (  g/g) 200 ml of influent

Hypothetical Batch Test

Hypothetical Batch Tests – Partition Coefficient K d Partition Coefficient K d K d = C s /C eq From batch test data K d = 31.5/2000 = (L/g)

Estimated Partition Coefficient However K d can also be calculated using K d = K oc x F oc where: K oc = soil sorption coefficient normalised for total organic content F oc = fraction of total organic content Example (see handout tables for F oc and K oc ) Clays F oc = 0.2 Benzene K oc = 87.1 L/kg K d = 87.1 x 0.2 L/kg K d = L/kg ( or L/g)

SAQ4 Sketch the biotransformation pathway for trichloroethylene to ethene. Self Assessment Q’s

SAQ5 (a)Describe the physical, geochemical and biological mechanisms involved in the natural attenuation of petroleum fuels and chlorinated solvents in an aquifer. (b)Explain the different mechanisms involved in absorption and adsorption of organic pollutants to soil particles. Used sketches where applicable to illustrate bonding mechanism and mention relevant minerals. (c)Use the following data from a soil batch test to calculate the sorbed concentration (  g/g), plot a linear isotherm and calculate the sorption coefficient K d. The weight of soil is 40.42g and the volume of the aqueous solution is 200 ml. Initial Concentration (  g/l)Equilibrium Concentration (  g/l)

Self Assessment Q’s SAQ6 A spillage of petroleum fuels and chlorinated solvent (trichloroethylene) has taken place at an industrial site. The results from chemical analyses of groundwater samples from 3 boreholes are shown below. Comment on evidence or potential for natural attenuation at each boreholes. ParametersBorehole 1Borehole 2Borehole 3 pH DOC (%) Redox (mV) TOC (mg/l) Nitrate (mg/l) Sulphate (mg/l) Tetrachloroethene (  g/l) Trichloroethene (  g/l) Cis-dichloroethene (  g/l) Trans-dichloroethene (  g/l) Vinyl Chloride (  g/l)