Environmental Geosciences

Human Interactions with the Environment

Andrea KoschinskyOrganics

Characteristics of Organic CompoundsVapour pressure of organicsGiven a mixture (ideal) of organics the partial pressure of component i is given by Raoult’s law:Pi = xi Pi,o

where P0 is the vapor pressure of the pure substance.

Solubility of organics in waterThe aqueous solubility will obey Henry’s law:Pi = ki Ci

w

where Ciw is the concentration in water and ki is the Henry’s Law constant.

Estimating values for Koc

The partitioning of organics between solid organic matter and water is given by Koc. The values for Koc can be predicted from the measured octanol-water partitioning for insoluble organics:Kow = [organic in octanol]/[organic in water]log Koc = 0.49 + 0.72 log Kow

Sorption of organics onto soil organic matterThe partitioning between soil and groundwater is found by scaling Koc by the fraction of organic matter (f =0.0001-0.02.):Distribution coefficient Kd = Kocfoc

Organic Compounds

Aliphatic compounds

Organic Compounds

Cl

Organic Compounds

BTEX is an acronym for benzene, toluene, ethylbenzene, and xylene .

This group of volatile organic compounds (VOCs) is found in petroleum hydrocarbons, such as gasoline, and other common environmental contaminants.

Aromatic compounds

Organic CompoundsVolatile organic compounds (VOCs) are compounds that have a high vapor pressure and low water solubility. Many VOCs are human-made chemicals that are used and produced in the manufacture of paints, pharmaceuticals, and refrigerants. VOCs typically are industrial solvents, such as trichloroethylene; fuel oxygenates, such as methyl tertiary-butyl ether (MTBE); or by-products produced by chlorination in water treatment, such as chloroform. VOCs are often components of petroleum fuels, hydraulic fluids, paint thinners, and dry cleaning agents. VOCs are common ground-water contaminants.

Chemical structure of MTBE

Persistant bioaccumulative toxic chemicals (PBTs) are chemicals that are toxic, persist in the environment and bioaccumulate in food chains and, thus, pose risks to human health and ecosystems. The biggest concerns about PBTs are that they transfer rather easily among air, water, and land, and span boundaries of programs, geography, and generations.

Organic Compounds

Benzene

Naphthalene

Anthracene

Phenanthrene

Larger systems of benzene ring structure fused together is called PAH

Chemistry of the structures is the same but usually more reactive then benzene

Perylene

Polynuclear aromatic hydrocarbons (PAHs) are hydrocarbon compounds with multiple benzene rings. PAHs are typical components of asphalts, fuels, oils, and greases. They are also called Polycyclic Aromatic Hydrocarbons.

Organic Compounds

Sources of PAHs

• PAHs mainly arise from combustion-related or oil-related man-made sources.– burning of coal, oil, gas, wood, tobacco, rubbish, and other organic substances. – also present in coal tars, crude oil, and petroleum products such as asphalt.

• ubiquitous environmental contaminants • natural sources : forest fires and volcanoes, biological sources of PAHs

Effects of PAH

• Short-term: irritation, nausea, • Long term: Carcinogenic• Reproductive failures • Kidney, liver damage, jaundice • Bioaccumulates rapidly in aquatic life

• PAH burden in temperate environments is mostly pyrogenic Essential to understand and predict the global dynamics and trends of these compounds

Organic CompoundsPersistent Organic Pollutants (POPs) are chemical substances that persist in the environment, bioaccumulate through the food web, and pose a risk of causing adverse effects to human population and the environment. There has been a realization that these pollutants, upon exposure of human population, can cause serious health effects ranging from increased incidence of cancers to disruption of hormonal system. These effects have also been observed and recorded for various animal species. Developing countries are particularly vulnerable due to often indiscriminate use and disposal of POPs.

Organochlorines are synthetic organic compounds that contain chlorine. A generally used term referring to compounds that contain mostly or exclusively carbon, hydrogen, and chlorine. Examples are DDT, chlordane, and lindane; PCBs; and some solvents that contain chlorine.

Chemical structure of DDT, an insecticide formerly used to keep mosquito populations in check.

Chemical structure of HCHs (hexachlorocyclohexane, Lindane), used as an insecticide

Organic Compounds

Polychlorinated biphenyls (PCBs) are mixtures of up to 209 individual chlorinated compounds (known as congeners). PCBs are either oily liquids or solids that are colorless to light yellow. Some PCBs can exist as a vapor in air. PCBs have no known smell or taste. Polychlorinated biphenyls persist in the environment and are passed up the food chain, with the highest levels accumulating in predatory birds and mammals.

Use: PCBs were predominantly used as coolant insulant and heat transfer agents in a number of electrical products such as transformers and capacitors. PCBs were also used in a wide variety of products including printing inks, adhesives and paints. There are no known natural sources of PCBs.

Chemical Structure: General structure C12 H10-x Clx where x = 1 to 10

--> 209 different congeners

Organic Compounds

Polychlorinated biphenyls (PCBs)

• PCB contamination first recognized more than 30 years ago by S. Jensen detecting PCBs in pike from Sweden. S. Jensen , Report of a new chemical hazard. New Scientist 32 (1966), p. 312.

• PCBs are now considered an environmental problem of global proportions.• Several of these studies have indicated that the trends in environmental

concentrations have followed the trends in production and use of PCBs. • Quantitative knowledge of the global historical consumption is a prerequisite for

estimating atmospheric emissions and eventually establishing source–receptor relationships for intentionally produced PCBs on a global scale.

• Not all congeners have been identified in commercial products or technical mixtures. • Individual PCB congeners are assigned a number, ranging from PCB-1 (2-CB) to

PCB-209 (2,2′,3,3′,4,4′,5,5′,6,6′-CB). //IUPAC system. This numbering system is used in the study, and 22 individual PCB congeners are studied.

Organic Compounds

Polychlorinated biphenyls (PCBs):

Global Total PCB production in t as reported in the literature

Organic Compounds

Polychlorinated biphenyls (PCBs):

Global consumption of total PCBs for six different time-periods (by latitude).

Organic Compounds

Polychlorinated biphenyls (PCBs):

Global consumption

Estimated cumulative global usage of PCBs (legends in t) with 1°×1° longitude and latitude resolution.

Organic Compounds

Dioxins - General name given to 210 organic compounds containing carbon, oxygen and hydrogen with one to eight chlorine atoms. Only 17 of the 210 dioxins are known to be toxic.

Dioxins in trace quantities are created naturally (e.g. volcanoes) and as unwanted by-products in numerous combustion processes (e.g. forest fires, cigarettes, bonfires, car engines etc.), in metal smelting and recycling processes and in the manufacture of a few chlorine-containing chemicals.

The intake of dioxins according to the different food groups

Organic CompoundsDioxins - Sources and Pathways

Organic CompoundsDioxins - Emission

Overview of Analytical Methods for Organic

Contaminants extraction, separation and clean-up

Regardless of the method used to identify and quantify organic chemical contaminants, steps must first be taken to extract chemicals of interest from the bulk of the sample material and to separate them from other chemicals that might be co-extracted. These steps are usually accomplished by "wet-chemistry" procedures in the laboratory. The extraction and separation methods selected by the analyst will ultimately affect the limit of detection of the chemical of interest and the final use of data. The analyst begins to make trade-off decisions (i.e., cost, method complexity, time, resolution, etc.) at the time of initial sampling. These early decisions concerning sample handling ultimately affect data interpretation.

Extraction columns for the separation and enrichment of PCBs

Overview of Analytical Methods for OrganicAnalytical instrumentation

Usually, the end result of the extraction, separation and clean-up procedures used is a concentrated mixture containing chemicals of similar structure that can be analyzed further. This further analysis is usually done by various kinds of instruments, where instrument selection is based on the specific data need. Some instrumentation will only detect compound groups while others can resolve and detect individual compounds. All instrumentation have inherent detection limits and these limits vary by orders-of-magnitude between types of instruments. In addition to sample resolution and limit detection characteristics, the analyst will consider initial cost, cost of operation, availability, and operation complexity when making an instrument decision.

Spectroscopic Methods

UV-fluorescence

When excited by ultraviolet light, some organic molecules are caused to emit fluorescent light. By adjusting (or scanning) both the excitement and emission spectra, aromatic hydrocarbons may be analyzed. This method is specifically useful to indicate the presence of polycyclic aromatic hydrocarbons (PAH). This is a bulk measure and provides little indication of the complexity of a mixture or how much of a signal might derive from interfering compounds (e.g., conjugated alkenes). The use of this method is most appropriately limited to highly contaminated samples or as a screening technique. Reported results can not be directly compared to results from other methods of analysis.

Overview of Analytical Methods for Organic

Infra-red Spectroscopy (IR)

Organic molecules have a flexible structure, which allows infrared light to be absorbed by the molecule. The amount of light absorbed (percent transmission) can be related to structural characteristics of the molecule and thus be used for identification. This sensitive technique cannot be used for analysis of individual hydrocarbons as it is difficult to separate natural from contaminant hydrocarbons; however, it can be used for remote analysis of samples. IR data will probably be reported for environmental samples only in situations which involve remote sensing of complex mixtures such as for oil spills.

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Principle IR: With the absorption of light energy in the range from 0.8-

500 µm, different mechanical vibrations of atoms or functional

groups are excited in a molecule.

Overview of Analytical Methods for Organic

Chromatographic techniques

All chromatographic methods work on the same principle: differential mobility. Separation of molecular types, and even individual compounds, is achieved by exploiting the relative affinity of an organic compound (or groups of similar compounds) to two phases; one mobile and one stationary. The phases may be solid, liquid or gas and separation occurs as the compound that is being analyzed spends more or less time in either the mobile or the stationary phase. Chromatography is a reliable method for separation of hydrocarbon mixtures.

Gas Chromatography (GC)

In GC, a gas carries the volatilized sample mixture through a column in which a liquid stationary phase has been coated. After separation, the fractionated sample is sequentially eluted and compounds of interest are quantified on an appropriate detector. In early environmental studies (pre-1975), most GC analyses were accomplished in large diameter columns that were packed with an inert substrate on which the liquid phase was coated. Resolution of complex environmental samples was mediocre and full separation of most mixtures was not possible. Beginning in the mid-70s, high-resolution separation of environmental samples using capillary GC began to be introduced and eventually replaced packed column separations as a routine analytical tool.

Example: High-resolution gas chromatogram of the C6-C8 portion of a whole

oil showing the identification of more

than 40 hydrocarbon isomers, the distribution

of which provides information on source,

maturity and alteration.

Overview of Analytical Methods for OrganicDetectors

Several detectors are available for the analysis of the effluent stream from a gas chromatography column. The flame ionization detector is commonly selected because of its applicability to a broad range of analytes. Chemicals in the effluent stream are ionized in a flame that is burning between two electrodes. The ions migrate to one of the electrodes, and cause a change in potential that is amplified and detected.

The electron capture detector has a high sensitivity for analytes that contain halides and is commonly used for the analysis of chlorinated pesticides and PCBs.

Overview of Analytical Methods for OrganicHigh-Performance Liquid Chromatography (HPLC)

In HPLC, a liquid is pumped through a solid-phase column to allow for partitioning between the phases. With constantly improving resolution and sensitivity, HPLC has evolved slowly into a valuable analytical technique for separation of chemical contaminants. Compounds are subsequently eluted from the column and detection of the presence and amount of chemical in the column effluent is accomplished in a variety of ways, including spectroscopy, change in refractive index, UV-VIS absorption, or fluorescence after excitation with a suitable wavelength.

Organic Compounds in the Ecosystem

TCDD = Tetrachlordibenzo-p-dioxine

Organic Compounds in the Ecosystem

Bioaccumulation of PCBs

Organic Compounds in the Ecosystem

Ecochemical materials properties and their

relevance for bioaccumulation of

PCBs

Organic Compounds in the Ecosystem

Organic Compounds in the Ecosystem

Organic Compounds in the Ecosystem

Organic Compounds in the Ecosystem

Organic Compounds

Contamination with Organic Compounds

Contamination with Organic Compounds

Contamination with Organic Compounds

Contamination with Organic Compounds

Contamination with Organic Compounds