1212569_21823227.jpg logo_mu_cerne.gif 1212570_28446780.jpg logo_mu_cerne.gif Luděk Bláha, SCI MUNI Chemical compounds in ecosystems -introduction – OPVK_MU_stred_2 1212569_21823227.jpg logo_mu_cerne.gif Take home messages of this lecture: •Know the names, chemical properties (basic structural character) and sources of the main groups of pollutants •Explain what environmental factors influence the behavior of compounds in the environment (logKow, H, persistence)… •… and thus condition the extent of bioavailability of compounds in the environment and exposure of organisms 1212569_21823227.jpg logo_mu_cerne.gif Definitions are ambiguous... however, it is desired to understand the meaning of individual terms TOXICANTS / TOXINS / ECOTOXICANTS èTOXICANTS = compounds toxic in relatively low concentrations, introduced into the environment by human activities èTOXINS = natural tox. compounds – produced by plants, bacteria, animals èNote - some examples of environmentally significant natural toxins, which are at the same time ecotoxicants: cyanobacterial toxins – environmentally relevant due to anthropogenic activities - eutrophication è Important terms http://cdn.phys.org/newman/gfx/news/hires/2013/1-increasingto.jpg 1212569_21823227.jpg logo_mu_cerne.gif Ecotoxicants •Compounds selected from a wide range of chemical substances (petroleum and its products – organic compounds, pharmaceuticals, pesticides), which can be released into the environment and can cause specific effects/interactions in ecosystems • •Each human activity is accompanied by introduction of (toxic) compounds into the environment –products and side products of industry –household waste (detergents, plastics ....) –products used in agriculture –wastes from transport –veterinary and human pharmaceuticals –other … • https://encrypted-tbn3.gstatic.com/images?q=tbn:ANd9GcQYrBy1inGcFytovwR4-D2fwFegMAixkxWqeiEL1o6-jxO 6qdK1Zg 1212569_21823227.jpg logo_mu_cerne.gif •Contaminants •Compounds polluting the environment (Not necessarily directly toxic, but harmful at the end) • –! nutrients (NOx and POx) •are not ecotoxicants BUT do have many secondary effects à eutrophication – –! organic communal waste •not directly toxic BUT increases the content of organic carbon •à decomposition processes à reduction of oxygen content à toxic to aquatic organisms – –! toxic metals, polycyclic aromatic hydrocarbons (PAHs) •natural occurrence in the nature BUT in “background” concentrations • –! simple soaps •released in high concentrations BUT rapidly hydrolyzed to nontoxic products – Ecotoxicants vs. Contaminants ? 1212569_21823227.jpg logo_mu_cerne.gif Contamination of water - chemicals ? Degradable „nontoxic“ organic material + nutrients / fertilizers (N/P) „Other“ chemicals 1212569_21823227.jpg logo_mu_cerne.gif What chemicals for example?... In EU groundwaters? Loos et al. Pan-European survey on the occurrence of selected polar organic persistent pollutants in ground water (Water Research 44, 2010, 4115-4126) 1212569_21823227.jpg logo_mu_cerne.gif What numbers of CHEMICALS ? www.cas.org 1212569_21823227.jpg logo_mu_cerne.gif What numbers of CHEMICALS ? https://echa.europa.eu/information-on-chemicals/ec-inventory Cc 22,000 are used by industry 1212569_21823227.jpg logo_mu_cerne.gif •Overview of contamination sources –a student should have a general overview and be able to name representative examples – –POINT SOURCES (easier to control and penalize) •communal wastewaters •industrial wastewaters •solid urban- and industrial wastes – damps / combustion – –DIFFUSE SOURCES (difficult to control) •industry, engine emissions, energy production •surface run-offs (roads, roofs, coatings...) •agricultural activities • –LINE SOURCES (difficult to control) •(highways) traffic • • Sources... and examples of representative contaminants http://wwws3.eea.europa.eu/themes/water/water-pollution/figures-and-maps/sources-of-pollution/image 1212569_21823227.jpg logo_mu_cerne.gif Communal wastewaters •Effect on environmental components –Primary effect on water ... secondary also on soil and further influence on food chain (irrigation, WWT sludges) – •Significant contaminants –Nontoxic organic compounds (fecal pollution) –PPCP (Pharmaceuticals and Personal Care Products) •Pharmaceuticals •Household chemicals (detergents, softeners, fragrances/musks) –Polycyclic aromatic hydrocarbons (PAHs) –Chlorinated compounds –Toxic metals • http://www.omafra.gov.on.ca/english/nm/nasm/info/brochuref2.gif 1212569_21823227.jpg logo_mu_cerne.gif http://media.except.nl/media/cache/uploaded_images/asset_image/Industrie_All_v3_pure_image.jpg Industrial wastewaters •Effect on environmental components –Primary effect on water ... – •Significant contaminants –Specific products regarding the industrial type, examples: •Food industry – organic pollution, phytoestrogens •Pulp and paper industry – chlorine, organochlorine compounds •Metal processing – cooling and metalworking-fluids (chlorinated alkanes / paraffins) •etc. –Toxic metals –Acids, solvents (incl. halogenated) – –Contaminants with global importance •Polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs) •Polychlorinated biphenyls (PCBs) •Polycyclic aromatic hydrocarbons (PAHs) • • http://www.iswa.uni-stuttgart.de/lsww/bilder/iwt_bereiche.en.jpg 1212569_21823227.jpg logo_mu_cerne.gif Landfills & Industrial zones (brownfields) •Effect on environmental components –Primary effect on ground water (GW) • •Significant contaminants –Specific products regarding the industrial type and landfilling, frequent GW contaminants •BTEX – benzene, toluene, ethylbenzene, and xylenes •Low molecular weight halogenated solvents– e.g. ethylenes (TCE, DCE) –Toxic metals – –Contaminants with global importance •Polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs) •Polychlorinated biphenyls (PCBs) •Organochlorine pesticides (OCPs) • • http://wwws4.eea.europa.eu/publications/GH-07-97-595-EN-C2/Figure7_10.GIF 1212569_21823227.jpg logo_mu_cerne.gif Industry, internal combustion engines, energy production •Effect on environmental components –Diffuse pollution –Primary effect on atmosphere + on all ecosystems • •Significant contaminants –Toxic metals (e.g. Pb, Cd etc.) –CO, CO2 –Polycyclic aromatic hydrocarbons (PAHs) –SOx, NOx –Polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs) – –Specific organic compounds used by industry •Regarding the type of the industry •Global importance e.g. Polychlorinated biphenyls (PCBs) • http://tiki.oneworld.org/energy/wonder_pollution.gif 1212569_21823227.jpg logo_mu_cerne.gif Surface run off •Effect on environmental components –Diffuse pollution –Primary effect on water (surface and ground)... – •Significant contaminants –Construction chemicals –Chlorinated compounds –Toxic metals – –Contaminants with global importance •Polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs) •Polychlorinated biphenyls (PCBs) •Polycyclic aromatic hydrocarbons (PAHs) • • http://www.livingonkarst.org/images/image006.jpg http://pugetsound.org/education/polluted-runoff/images/stormwaterjourney.jpg 1212569_21823227.jpg logo_mu_cerne.gif Agriculture •Effect on environmental components –Diffuse pollution –Primary effect on soil... but indirectly also on all other env. components – •Significant contaminants –Pant protection treatments (pesticides) –Fertilizers (N-, P-) and contaminants therein (often e.g. Cd) –Veterinary pharmaceuticals (à application of manure) • • • http://univr-cms.u-strasbg.fr/depotcel/DepotCel/592/contexte/fig1_eng.jpg 1212569_21823227.jpg logo_mu_cerne.gif Main groups of pollutants Important terms, abbreviations... and structures 1212569_21823227.jpg logo_mu_cerne.gif Pesticides Toxic for pests DDT, parathion, glyphosate (round-up), atrazine Insecticides Toxic for insect/arthropods DDT, parathion Herbicides Toxic for plants 2,4-D, glyphosate, atrazine Fungicides Toxic for fungi/moulds Pesticides containing toxic metals (Hg, Cu) Rodenticides Toxic for rodents Cyanide Carcinogens Induce cancer Benzo[a]pyrene Reprotoxins Effect on reproduction Ethinylestradiol Endocrine disruptors Effect on hormone systems Ethinylestradiol, tributyltin Compounds grouped by effect 1212569_21823227.jpg logo_mu_cerne.gif Lipophilic (hydrophobic) Soluble in fat / low solubility in water DDT Hydrophilic Soluble in water Phenol, modern insecticides Neutral organic compounds Uncharged compounds (do not ionize) DDT, PCB Radioactive compounds Unstable, decay and emit radiation Radon Surfactants, detergents Compounds lowering surface tension between two phases Nonylphenol, alkylbenzene sulfonates Persistent compounds Very long half-life in the environment (do not degrade) DDT, PCB Volatile organic compounds Volatile organic compounds (VOCs) Acetone, Benzene, Formaldehyde, Xylene Perchloroethylene, Toluene etc. Compounds grouped by phys-chem properties 1212569_21823227.jpg logo_mu_cerne.gif Chlorinated hydrocarbons, organochlorine compounds DDT, PCB, PCDD/Fs PCBs Polychlorinated biphenyls PCB153 PAHs Polycyclic aromatic hydrocarbons Benzo[a]pyrene PCDD/Fs Polychlorinated dibenzo-p-dioxins and -furans 2,3,7,8-TCDD Toxic metals, heavy metals Hg, Pb, Cd (+ others) Organometallics Alkyl tins OPs Organophosphates Compounds (insecticides) – e.g. parathion BTEX Benzene and its derivates –contamination of ground water and air (volatiles) Benzene, Toluene, Ethylbenzene, Xylenes Significant compounds grouped by their structure 1212569_21823227.jpg logo_mu_cerne.gif DDT PCB153 (very abundant) Polychlorinated dioxines and furans (PCDD/Fs) Benzo[a]pyrene – example of PAHs Tributyltin chloride (Organometal) Cypermethrin Organophosphates BTEX http://upload.wikimedia.org/wikipedia/commons/thumb/1/11/Benzene_Toluene_and_ortho-%2Cmeta-%2Cand_p ara-xylene.svg/317px-Benzene_Toluene_and_ortho-%2Cmeta-%2Cand_para-xylene.svg.png Be aware of the most important structures 1212569_21823227.jpg logo_mu_cerne.gif Further commont terms/abbreviations – groups of compounds •HPVC - High-production volume chemicals (from the REACH legislation) •CMR - Carcinogenic, mutagenic or reprotoxic (from the REACH legislation) •EDC - Endocrine disruptive compounds •POPs – Persistent organic pollutants (as defined in the Stockholm Convention) •OCPs – Organochlorine pesticides (e.g. DDT, lindane etc.) •PBT – Persistent bioaccumulative and toxic compounds –very dangerous - specific legislation •PPCP - Pharmaceuticals and personal care products •PPP - Plant protection products –(generally „pesticides“) •HCs - Halogenated compounds (usually at ground water contamination) •Emerging contaminants – generally polar compounds, which are not well studied, yet (previously most attention to persistent compounds!) 1212569_21823227.jpg logo_mu_cerne.gif Environmental processes 1212569_21823227.jpg logo_mu_cerne.gif Risk of compound presence to the environment – which parameters are determining? RISK (e.g. decline in fish population in CZ) Properties of the substance HAZARD Does it enter the fish? (bioconcentration) Can bioaccumulate? Concentrates in the food chain (biomagnification)? Is hazardous/toxic to fish? What is the mode of action/toxicity type? At what concentrations? Situation in the environment EXPOSURE Is the compound in the water? (fate) Is the compound in a form available to fish? (bioavailability) What is the bioavailable concentration? Chart summarizes terms explained in the next part of the lecture 1212569_21823227.jpg logo_mu_cerne.gif Environmental FATE of the compound determines the EXPOSURE E3 ENVIRONMENTAL FATE describes ? In which environmental compartments DISTRIBUTION between compartments is the compound present ? How it migrates within the compartments TRANSPORT – e.g. by air ? How it transforms within the compartments TRANSFORMATION – chemical and biological EXPOSURE Extent of exposure of an organism to a compound (in a specific concentration, for a specific time etc. = Exposure scenarios) 1212569_21823227.jpg logo_mu_cerne.gif What parameters determine the fate of a chemical compound? DISTRIBUTION TRANSPORT TRANSFORMATION Compound properties Polarity vs hydrophobicity (Kow, water solubility) Volatility, boiling point, evaporation (H, boiling point) Reactivity vs stability and persistence (t1/2) Environmental properties Drift (pace, direction, type ...) Temperature Light (and its parameters) Chemical composition pH (free H+) Redox potential (... presence of O2) Presence of inorganic ions / cation-exchange capacity (e.g. clay) Particles – type, size, amount Organic matter – type, amount (humic acids etc.) Water Sediments Soil Atmosphere Biota properties vegetation, consumers... Number / Motion / Size (surface) / Fat content (%) / Food chain level etc. etc. E3 The fate and resulting exposure of organisms is defined by a combination of listed parameters Kow, H, t1/2 1212569_21823227.jpg logo_mu_cerne.gif Which parameters are especially crucial regarding the risk of ECOTOXICITY? • •1) Tendency to enter the organism • - higher hydrophobicity (fat in organisms) • - partition coefficient octanol/water (Kow, logP) • •2) Stability (persistence, low degradability) • - long-term functionality in the environment • - half-life (t1/2) • •3) Toxic effects in organisms • • … information on each parameter is needed • • 1+2 – in this part of the course • 3 – other lectures • • 1212569_21823227.jpg logo_mu_cerne.gif Entry of compound into the biota (transport from the environment into the organism) •Compound distribution between environmental compartments –Partition processes between environmental compartments (compartments/matrices/phases) –biota/atmosphere - sediment (soil) / water –soil/atmosphere - water/atmosphere – •BIOTA as one of the compartments –important are partition processes “environment ß à biota” –Atmosphere / biota –Water / biota –Sediment / biota –Soil / biota –Biota(food) / Biota (predator) • http://engineering.dartmouth.edu/sedg/images/clip_image002_005.gif 1212569_21823227.jpg logo_mu_cerne.gif •Ca = K. Cb 1/n • C – concentration in phases A (Ca) and B (Cb) • K – partition constant • n – nonlinearity constant • •In case of a linear relationship (n=1) K = Ca / Cb = “partition coefficient” –The size of K determines the tendency of the compound to transfer from phase B into phase A • •From a practical experiment (compound partitioning between two phases) respective constants can be determined • log Ca = 1/n . log Cb + log K • • Partition processes between two phases in EQUILIBRIUM are consistent with the first order kinetics – defined by the Freundlich equation E3 K = slope in the linear part of the curve 1212569_21823227.jpg logo_mu_cerne.gif •BIOTA / Water partition coefficient –difficult to determine (standard procedure –bioconcentration determination: see further) à Alternatively – model with n-octanol •N-octanol –Immiscible with water, similar properties to fats or phospholipids of biological membranes • •n-octanol/water partitioning •Kow – partition coefficient •Characterizes HYDROPHOBICITY (resp. LIPOPHILICITY) •Often expressed as logKow (resp. logP) “Biota-Water” partition model Experimental Kow determination http://chem3513-2007.pbworks.com/f/1196800274/11111.png System n-octanol/water + compound insertion https://encrypted-tbn1.gstatic.com/images?q=tbn:ANd9GcQCHJGqrBcYK2KfOl1kf14Rc2J0pbGmNIP5HmuUOSBqDsF q6YqGgA 4 different initial concentrations n-oct water Shaking until equilibrium is established Chemical analysis of concentrations Kow calculation E3 1212569_21823227.jpg logo_mu_cerne.gif Compound Kow logKow (logP) K_bioaccumulation (experimental) Lindane 5 250 3.72 470 DDT 2 290 000 6.35 1 100 000 Arochlor 1242 (PCB) 199 600 5.30 3 200 Naphthalene 3 900 3.59 430 Benzene 135 2.13 13 Kow – examples http://www.edusoft-lc.com/hint/manuals/gif/hydropho.gif https://encrypted-tbn3.gstatic.com/images?q=tbn:ANd9GcQOD6onm7_orG6StftSz9L80HMlRv2TVEDk8mcrvlMiOBb jnVkV 1212569_21823227.jpg logo_mu_cerne.gif Bioaccumulation, Bioconcentration, Biomagnification http://omicsonline.org/JMBDimages/2155-9929-S1-003-g001.gif https://encrypted-tbn3.gstatic.com/images?q=tbn:ANd9GcQOD6onm7_orG6StftSz9L80HMlRv2TVEDk8mcrvlMiOBb jnVkV Bioconcentration The extent of compound uptake into the organism (fish) from water BCF – Bioconcentration factor http://www.ibacon.de/tl_files/images/test-systems/environmental/14C/oecd_305_bioaccumulation_fish.j pg http://upload.wikimedia.org/math/a/a/9/aa9f301a0501c3cca3c98b71cc5ecfe2.png Experimental determination Tests with fish (standard OECD 305) Time consuming, demanding tests, tests with fish in vivo It is possible to predict BCF from Kow 1212569_21823227.jpg logo_mu_cerne.gif Bioaccumulation, Bioconcentration, Biomagnification Bioaccumulation Compound accumulation (all routes of exposure) BAF – Bioaccumulation factor http://sustainablenano.files.wordpress.com/2013/12/3-bioaccumulation-vs-biomagnification.png Biomagnification Increasing concentration of compounds in organisms via food chain BMF – Biomagnification factor (Cpredator/Cfood) 1212569_21823227.jpg logo_mu_cerne.gif http://www.itrcweb.org/contseds-bioavailability/images/fig_5_3.jpg Biomagnification 1212569_21823227.jpg logo_mu_cerne.gif ATMOSPHERE / WATER partitioning 1212569_21823227.jpg logo_mu_cerne.gif ATMOSPHERE / WATER partitioning - ionized compounds do not evaporate into the atmosphere - significant partitioning (again) at organic neutral compounds - partitioning between water- and liquid phase is described by the Henry‘s law: p = H . CW p – partial pressure of a compound (Pa) H – Henry‘s law constant (Pa.m3.mol-1) – characteristic for a specific compound CW – concentration in water (mol . m3) Note: boiling point of a specific compound is a measure of volatility H (Pa . mol-1 . m-3) Description > 100 Very fast released from water Example: halogenated aliphatic hydrocarbons (dichloroethane and such) 25-100 Volatilization slower Example: chlorinated benzenes 1-25 Sow volatilization Example: most of the PCBs < 1 Insignificant volatilization Example: high chlorinated PCDDs 1212569_21823227.jpg logo_mu_cerne.gif Environmental transformation / Persistence 1212569_21823227.jpg logo_mu_cerne.gif •Types of transformation of organic compounds: –partial structural change (e.g. introduction od OH into neutral fatty acids) –degradation into smaller organic molecules –total degradation of the org. compound (CO2, H2O) • •Main processes –Chemical – regarding the type of the environment •atmosphere – photochemical reactions, reactions with oxygen (!) •water – hydrolysis, oxidations •anoxic environment (sediments, ground water) – reductions –Biotic (enzymatic) •Ready biodegradability – compound serves as a carbon source to microorganisms à CO2 production •Cometabolism – microorganisms require other (main) C source (compound transformation as a part of „ancillary/other“ processes) •Result of transformation –nontoxic products –production of even more toxic products (! e.g. Hg à methyl-Hg) • •Biodegradability vs Persistence –Polar and reactive compounds – mostly short half-life –Halogenated, neutral compounds – persistent in the environment – Environmental transformation – (bio)transformation 1212569_21823227.jpg logo_mu_cerne.gif E3 Simple transformation processes (with oxygen supply) 1212569_21823227.jpg logo_mu_cerne.gif Anaerobic biotransformation – example methylmercury http://scifun.chem.wisc.edu/chemweek/mercury/merccycle.gif Me-Hg •Bioaccumulation •High toxicity 1212569_21823227.jpg logo_mu_cerne.gif •Transformation kinetics – first order kinetics – Ct = C0 . e-kt Ct – concentration in time t C0 – initial concentration k – constant (degradation speed) t – time •After derivation (half-life) •t1/2 = ln2 / k = 0.693 / k • Persistence characterisation – half-life Time (days) 1212569_21823227.jpg logo_mu_cerne.gif Half-life of selected pesticides in soil - examples Compound Half-life in soil (years) (t1/2 or DT50 – disappearance time 50%) Chlorinated compounds DDT 3-10 Dieldrin 1-7 Toxaphene 10 Organophosphate – chlorfenos 0,2 Carbamate – carbofuran 0,05 – 1 1212569_21823227.jpg logo_mu_cerne.gif Degradation assessment in praxis (standards) OECD recommendation – guideline 307 •Aerobic and Anaerobic Transformation in Soil –Introduction of examined compound (can be radioactively labelled) –Incubation in time àsoil extraction (volatile fraction) àassessment of decrease in concentration of introduced compound and transformation products formation àChemical methods (GC, LC etc.) – – •Example of standardized OECD guideline • •Anaerobic Biodegradation Experiment see YOUTUBE •http://www.youtube.com/watch?v=Y_zFPkbrwSY 1212569_21823227.jpg logo_mu_cerne.gif Fate (processes) in the environment à Exposure à BIOAVAILABILITY 1212569_21823227.jpg logo_mu_cerne.gif BIOAVAILABILITY http://www.intechopen.com/source/html/45279/media/image3.jpeg •The term comes from pharmacology –compound fraction that is effective in the body •In environmental sciences –compound fraction, that can enter the organism = compound is in available form (it is not bound in the environment – e.g. to organic carbon etc.) • •Bioavailability describes processes (relations) between –Compounds present in the environment –Entry (accumulation) of compounds into the organisms –Environmental properties – Example - Soil two distinct soils (high and low organic carbon content) bioavailability (and thus bioaccumulation as well) is higher in the case of “low” 1212569_21823227.jpg logo_mu_cerne.gif Toxic metals in waters vs. water hardness -> higher water hardness (more Ca / Mg) – lower bioavailability / lower metal toxicity (competition with toxic metals for binding sites in biota) Bioavailability - examples http://what-when-how.com/wp-content/uploads/2012/04/tmp495.jpg 1212569_21823227.jpg logo_mu_cerne.gif Hydrophobicity – organic compounds vs. organic carbon (humins) -> hydrophobic compounds – tendency to accumulate in fat / in biota (at the same time also in dead organic matter - OC) -> high OC content in the environment (in water): lower bioavailability of compounds Bioavailability - examples http://www.itrcweb.org/contseds-bioavailability/images/text_box_2_2.jpg 1212569_21823227.jpg logo_mu_cerne.gif Toxic metals in water vs. pH / water composition -> higher pH: metals present in insoluble hydroxides (lower bioavailability) -> lower (acidic) pH – higher solubility and higher toxicity of metals Bioavailability - examples http://www.nps.gov/plants/restore/pubs/biosolids/img/biosolids10.jpg 1212569_21823227.jpg logo_mu_cerne.gif Where can the information on environmental properties be found? (Kow, t1/2 etc.) Where can the information on environmental properties be found 1212569_21823227.jpg logo_mu_cerne.gif •CAS – Chemical Abstract Services •Provided/Operated by American Chemical Society (ACS) •CAS Number – unique identifier •eChemPortal.org Look up information on one chemical “compound” that you could find in your bathroom 1212569_21823227.jpg logo_mu_cerne.gif Describe what are toxicants, ecotoxicants, toxins, and give examples. What are the main sources of toxic compounds in the environment? Provide an overview. Which human activity releases into the environment the most polychlorinated biphenyls, polychlorinated dioxins, polycyclic aromatic hydrocarbons? What is the main source of household chemistry (soaps, perfumes), pharmaceuticals for the environment? What compounds are released into the environment from areal pollution sources? Give examples – source:compounds What compounds enter the environment from point pollution sources? Give examples – source:compounds What are pesticides? insecticides? herbicides? fungicides? rodenticides? carcinogens? reprotoxins? endocrine disruptors? organophosphates? pyrethroids? toxic metals? Give example for each of the listed groups and describe the main features of the chemical structure (aromatic/aliphatic?, neutral/ionized?, halogenated?, hydrophilic or hydrophobic?, persistent or degradable?) SUMMARY – questions 1/3 1212569_21823227.jpg logo_mu_cerne.gif What key properties make a compound dangerous (hazardous) for the environment? What does the term “environmental fate of compounds” define/describe? Describe the main processes a compound can undergo in the environment and name the compound‘s properties (features) key for these processes. What properties play a key role in entering of a chemical compound into the organism? What is bioconcentration? What compound‘s property does it depend on? What is Kow? How can it be determined experimentally? Which compound has higher Kow - hexane OR hexanol? Which compound has higher Henry‘s law constant - dichloromethane or dichlorobenzene? What is biomagnification? Give an example of a compound that can be biomagnified and what levels does its BMF reach? What is bioavailability? Give examples of different scenarios, when the bioavailability of a selected compound would be very high and very low. The DDT concentrations in a river were determined as follows: (1) DDT bound to suspended particles 1 milligram/L water, (2) DDT dissolved in water 1 microgram/L water. What fraction (%) of DDT is approximately directly bioavailable for transfer through fish gills? SUMMARY – questions 2/3 1212569_21823227.jpg logo_mu_cerne.gif Which element plays a crucial role in chemical transformations of compounds in soil environment? What major transformation processes do compounds undergo in different environmental matrices (air, soil, water, sediments)? Define the half-life of a compound. Give examples of compounds with short and long half-life. How long are half-lives of these compounds? How is the biodegradability of a chemical compound determined in practice? How would the half-lives of benzo[a]pyrene (BaP) differ in the following scenarios? BaP bound to aerosol particles in the air, BaP bound to sediment on the bottom of a water reservoir/pond. The concentration of triazine in soil is 120 mg/kg and the DT50 is 180 days. When can we expect the decrease of triazine to 10 mg/kg? SUMMARY – questions 3/3