Question

Which of the followingabiotic transformations are most likely to occur in soil and groundwater systems for each of these chemicals? (a) n-butyl chloride,(b)2,4-Dichlorophenol,(c) carbon tetrachloride, (d)Mirex, (e) Trinitrobenzene, (f) Melathion

Answer 1

Ans A: n-butyl chloride is an alkyl halide with the chemical formula C₄H₉Cl.

It reacts with lithium metal to give n-butyllithium.N-Butyl Chloride is a chemical used mainly in veterinary worming applications.

Ingestion and other exposures to the chemical can cause various symptoms.

The type and harshness of signs differs depending on the amount of chemical involved and the nature of the exposure.

Ans.B 2,4-Dichlorophenol (2,4-D) with an emphasis and review of plant uptake, metabolism, and effects of exposure under forest conditions. Volatilization plays only a minor role in the breakdown and dissipation of the 2,4-D acid due to its low vapor pressure of 1.4x10-7 mmHg. In the aqueous environment, 2,4-D is most commonly found as the free anion,  

Therefore, the persistence of the 2,4-D anion is of primary concern. Residues of 2,4-D can enter ponds and streams by direct application or accidental drift; by inflow of herbicide previously deposited in dry streambeds, pond bottoms, or irrigation channels; runoff from soils; or by leaching through the soil column. 2,4-D esters and salts are first converted to the parent acid prior to degradation.

The rate of the ester hydrolysis decreases with decreasing soil moisture and with increasing molecular weight of the alcohol portion of the ester. The chance of 2,4-D may be affected by several methods including runoff, adsorption, chemical and microbial degradation, photodecomposition, and leaching. Water solubility and the soil adsorption coefficient (Koc) indicate the potential mobility of a chemical in soil

Ans.C Carbon tetra chloride is a continuous chemical that is ruined very slowly, so there has been a slow accumulation of carbon tetrachloride in the environment as a consequence of releases from human activities.Carbon tetrachloride accumulated from domestic manufacturing and processing facilities,small amounts of carbon tetrachloride are released to water.carbon tetrachloride to soils from domestic manufacturing and processing facilities and other sources of carbon tetrachloride clear to soil include wastes related with production and use of chlorofluorocarbons, metal cleaning compounds, adhesives, paints and other products.

Carbon tetrachloride dissolved in water does not photodegrade or oxidize in any measurable amounts The rate of hydrolysis in water is second order with respect to carbon tetrachloride, but is extremely slow.No studies located on the degradation of carbon tetrachloride in soil or sediment. Based on the estimated aqueous aerobic biodegradation half-life of carbon tetrachloride, the half-life of carbon tetrachloride in soil is estimated to be 6–12 months.

Ans.D. The insecticide mirex is a chlorinated hydrocarbon snow-white crystalline, odorless solid and it does not burn easily. Sunlight degrades mirex to photomirex, which can also have harmful effects. This chemical is highly resistant to microbiological degradation.Mirex breaks down slowly in the environment and it does not evaporate to any great extent from surface water or surface soil. Thus it is highly growing and it may remain on soil and water for years. Being very lipophilic, mirex is strongly adsorbed on sediments and it easily sticks to soil and sediment particles.

Ans.E. Trinitrobenzene spread in soil by following mean :1.ammunition production facilities, for example, wastewater lagoons, filtration pits;(ii)packing or warehouse facilities;(iii)waste disposal and destruction facilities, for example, open dumps, burn pits, incinerators;(iv)weapons firing ranges;(v)weapon impact areas..Different methods use in different medion, tranformation processes for trinitrobenzene in air may involve settling of vapour due to its higher density relative to air.

Trnitrobenzene will be transform through volatilization, sediment sorption for trinitrobenzene.sorbation technique is also useful in casetrinitrobenzene abiotic transformation .The amount of nitrobenzene adsorbed was largely determined by the organic carbon content of the sample, whereas the pH, cation exchange capacity and incubation temperature (5 °C and 21 °C) will be of minor importance.

Ans.F Malathion transformation products which are generally formed during storage or through natural or photochemical degradation. The conventional removal techniques of malathion include Reverse osmosis electrochemical oxidation, Fenton oxidation, solvent extraction, chemical oxidation and adsorption.Among all these abiotic condition, reverse osmosis is better technique. Nanofiltration is an economically attractive process and this led to its adaptation by many water suppliers.

Reverse osmosis is preferred for high retention parameters. High rejection rates of malathion during reverse osmosis process associated with cellulose-acetate, polyamide and ultra-low pressure membranes. The long-term application of reverse osmotic membranes exhibited rates higher than any transformation technique when ozonation will apply as a pre-treatment .Transformation of malathion will increase when nanofiltration can be effectively combined with other processes such as coagulation and adsorption