which of the following is an organic source of pollution
Answers
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Answer:
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Explanation:
Organic pollutants include many insecticides and herbicides that have been used in agriculture and pest control. ... Organic pollutants such as PCBs, dioxin and DDT are lipophilic; they are stored in fat cells and can be retained for years. They cross the placenta, and lactation is a significant source of exposure.
Organic pollutants in a constructed wetland could be estimated, in general lumped into the parameter of particulate organic carbon (POC) and/or dissolved organic carbon (DOC). The particulate or suspended solids are generally trapped physically in a wetland by sedimentation, straining, and flocculation. These sedimented solids could easily get re-suspended due to wind, gas flotation, and bioturbation.
The mechanisms responsible for removal of organic contaminants in wetlands can be divided into two classes of processes in the aquatic environment: transport and transformation. Individual contaminants tend to interact with sediments, suspended particulates, water, and biota (transport processes) and tend to be chemically and biologically transformed [42] to different extents due to physicochemical properties such as vapor pressure, solubility, hydrophobicity, and biodegradability. Sorption and volatilization are also important processes affecting some organic molecules.
Biochemical conversions in wetlands are based on degradation mechanisms of biodegradable organic matter. These mechanisms could remove some organic constituents by mineralization or gasification, and production of organic and inorganic matter. Degradation of organic compounds involves hydrolysis and catabolic activities of both autotrophic and heterotrophic microorganisms. Both aerobic and anaerobic degradations of soluble organic substances are responsible for the removal of BOD. Biodegradation by aerobic heterotrophic organisms is reflected in the following reaction:
[9]
Anaerobic degradation of organics also occurs in constructed wetlands when dissolved oxygen is diminished. This activity represents a multistep process carried out by either facultative or obligate anaerobic heterotrophic microorganisms. First step is the fermentation process carried out by facultative microorganisms leading to the formation of low molecular weight intermediates such as acetic, butyric, and lactic acids, alcohols with escaping end product gases such as CO2 and H2. In the second step, strictly anaerobic microorganisms utilize the group of intermediate fermentation products, converting them mainly into methane and some hydrogen sulfide.
Bacteria, anaerobic and aerobic, actinomycetes and fungi, play the most important role in wetlands in connection with the removal of organic matter by mineralization and gasification. They are also responsible for the synthesis of biomass and production of organic metabolic end products that may leach into the water column. They may also be classified with respect to their source of energy and type of chemical compound they use as a source of carbon.
The removal of organic matter is dependent on many factors such as temperature, pH, and oxygen availability, and, under some environmental conditions, process rates could slow down. Overloading of the system with organic matter could also affect oxygen levels in the water column, leading to anaerobic conditions. This could also even reverse many other pollutant removal processes.