Interaction effects of insecticides on microbial populations and dehydrogenase activity in a black clay soil

Three insecticides, monocrotophos, quinalphos, and cypermethrin, were applied at 0, 5, 10, and 25 microg g(-1) either singly or in combination to a black clay soil to investigate their effects on the soil microflora and dehydrogenase activity. All three insecticides significantly enhanced the proliferation of bacteria and fungi and the soil dehydrogenase activity even at the highest level of 25 microg g(-1). Monocrotophos or quinalphos in combination with cypermethrin at tested levels interacted significantly to yield additive, synergistic, and antagonistic responses toward bacteria and fungi and dehydrogenase activity in soil. Antagonistic interactions were more pronounced toward soil microflora and dehydrogenase activity when the two (monocrotophos or quinalphos + cypermethrin) insecticides were present together in the soil at highest level (25 + 25 microg g(-1)), whereas synergistic or additive responses occurred at lower level with the same combination of insecticides in soil.     

Adsorption-desorption, persistence and leaching behavior of thifluzamide in alluvial soil

Investigations were undertaken to study the adsorption-desorption, persistence and leaching of thifluzamide (2',6'-dibromo-2-methyl-4'-trifluoromethoxy-4-trifluoro methyl-1,3-thiazole-5-carboxanilide) in an alluvial soil under laboratory conditions. The adsorption-desorption studies were carried out using batch equilibration technique. The results revealed high but weak adsorption of thifluzamide in alluvial soil with K(F) value of 9.62 and 'n' value of 0.63. About 47-62% of the adsorbed amount got desorbed in four desorption cycles, which further substantiate the hypothesis of weak binding. The hysteresis coefficient varied from 0.19 to 0.40. Persistence studies carried out at three concentration levels (0.1, 1.0 and 10.0 microgg(-1)) and under three moisture conditions (air-dry, field capacity moisture and submerged) revealed that thifluzamide is a persistent chemical and only 19.5-54.0% dissipation was recorded on 90th day. However, it appears that aerobic microbes are more efficient in degrading thifluzamide than anaerobic microbes. The preliminary leaching studies carried out in the laboratory revealed that thifluzamide was moderately mobile in alluvial soil. Only small amounts (<1%) were recovered from leachate fractions whereas major portion remained in 0-15 cm soil depth.     

Adsorption of uranium(VI) on amorphous ferric oxyhydroxide at high concentrations of dissolved carbon(IV) and sulfur(VI)

Amorphous ferric oxyhydroxide is being used to treat groundwater contaminated with uranium(VI); the compound also has potential for use as a component in in situ chemical barriers. To quantitatively evaluate its effectiveness in such applications, adsorption of uranium(VI) onto amorphous ferric oxyhydroxide was experimentally investigated under a wide range of uranium(VI) (8.40·10⁻⁷−2.10·10⁻³ mol L⁻¹; 0.2–500 mg L⁻¹), sulfur(VI) (0–0.07 mol L⁻¹; 0–2240 mg L⁻¹) and carbon(IV) (0–0.0195 mol L⁻¹; 0–234 mg L⁻¹) concentrations, and pH-values (4–9.6). The adsorption behavior of uranium(VI) (uranyl ion and its complexes) is similar to that of other cations; it exhibits a sharp rise in the extent of adsorption with increasing pH. Interactions among uranyl complexes and surface sites are interpreted using a site complexation model. Although the model does not incorporate electrostatics and includes only a single type of adsorption site, it provides a reasonable match to measured adsorption and proton exchange data. The simplicity of the model and the resulting reduction in computational demand allow its efficient incorporation into coupled reaction-transport models.     

Hydrodynamic assessment of sewage impact on water quality of Malad Creek, Mumbai, India

The rapid population growth and uncontrolled development in the coastal zone have led to major pollution impacts on creeks, estuarine, and coastal environment. Water quality models are valuable tools to understand the environmental processes for prediction of pollution impacts and evaluate future trends for management. Presently, the Malad creek in west coast of Mumbai receives wastewater and sewage from open drains and partially treated sewage from Malad and Versova treatment plants. The objective of the paper is to assess the environmental quality and estimate the extent of improvement in different parts of the creek by enhancing the collection efficiency and adequate treatment of sewage as well as disposal through ocean outfall. A hydrodynamic and water quality simulation has been carried out for the present condition in the creek and calibrated and validated with two different season data for better representation of the system. Calibrated model has been used to generate future scenarios based on various options. Among scenarios, option of treated effluent diverted to propose outfall and improvement in collection of unorganized flow through sewerage up to 40% and 60% are found most significant for biochemical oxygen demand reduction and increase in dissolved oxygen. Fecal coliform reduction is also found drastically but still very high against standard. To improve the environmental quality of the creek, still upper stretch requires more dilution and flushing due to narrow width and contribution of heavy pollution from open drains.     

Visibility impairing aerosols in the urban atmosphere of Delhi

To study the visual air quality of Delhi, size fractionated aerosols – coarse and fine fractions of PM₁₀ – were collected and analysed for and EC at three sites with different background activities. The analysed species constitute a smaller portion of coarse fraction (39%) but a larger portion of fine fraction (69%). The sampling was performed from June 2003 to November 2003 which covers monsoon and post monsoon seasons.Aerosol data was used to describe the spatial variation of Visibility Range as a function of chemical composition of visibility impairing aerosols. During the study period, visibility was found to be poor varying between 4.7 and 13 km with an average value of 9.4 km. It is observed that visibility impairment was more due to carbonaceous aerosol followed by sulphate.     

DERIVATION OF SURFACE WATER LAG TIME FOR CONVERGING OVERLAND FLOW1

ABSTRACT: This study presents generalized and special forms of hydraulic solutions of surface water lag time, as conceptualized by Overton (1970), for the converging overland flow. It is shown that these solutions can be used to estimate lag time from physically measurable information on a given watershed.     

Evaluation of adsorption characteristics of an anionic azo dye Brilliant Yellow onto hen feathers in aqueous solutions

Purpose and aim

Removal of an anionic azo dye Brilliant Yellow has been carried out from its aqueous solutions by using hen feathers as potential adsorbent.

Materials and methods

Hen feathers procured from local poultry were cut, washed, and activated. Detailed chemical and physical analysis of hen feathers and its characterization through scanning electron microscopy, X-ray diffraction, and infrared measurements have been made. Procured dye has been adsorbed over under batch measurements and adsorption process is monitored using UV spectrophotometer.

Results

Optimum parameters for the adsorption of Brilliant Yellow over hen feathers have been determined by studying the effect of pH, temperature, concentration of dye, and amount of adsorbent. On the basis of Langmuir adsorption, isotherms feasibility of the ongoing adsorption has been ascertained and thermodynamic parameters have been calculated. Attempts have also been made to verify Freundlich, Tempkin, and Dubinin?CRadushkevich adsorption isotherm models. It is found that during adsorption, uniform distribution of binding energy takes place due to interaction of the dye molecules and the ongoing adsorption process is chemisorptions. The kinetic measurements indicate dominance of pseudo-second-order process during the adsorption. The mathematical treatment on the kinetic data reveals the rate-determining step to be governed through particle diffusion at 8?×?10^?5?M and involvement of film diffusion mechanism at higher concentration at temperatures at all the temperatures.

Conclusions

The developed process is highly efficient and it can be firmly concluded that hen feather exhibits excellent adsorption capacity towards hazardous azo dye Brilliant Yellow.     

PARAMETER ESTIMATION FOR TPLN DISTRIBUTION FOR FLOOD FREQUENCY ANALYSIS1

ABSTRACT: The principle of maximum entropy (POME) was used to derive an alternative method for parameter estimation for the three parameter lognormal (TPLN) distribution. Six sets of annual peak discharge data were used to evaluate this method and compare it with the methods of moments and maximum likelihood estimation.     

Time,affluence and pollution in the theory of consumer's behavior

This paper extends Becker's analysis on the allocation of time to provide a theoretical basis for the phrase “affluence breeds effluence.” Many environmentalists fear that a pollutant tax is merely a license to pollute. Their fears are well-founded if we consider the effect of increased affluence of the society on the pollutant stock. Assuming that relatively pollutant intensive “commodities” are also relatively less time intensive, an assumption applicable to most of the affluent societies, it is shown that the pollutant tax policy will be ineffective if the effect of increased wage rate on pollutant stock is ignored in spite of the efficiency of such a tax as a policy tool.     

A RAPID METHOD OF ESTIMATING MEAN AREAL RAINFALL1

ABSTRACT. A special case of generalized trend surface analysis is examined. This includes a linear surface. It is shown that for most hydrologic problems this case determines mean areal rainfall sufficiently accurately. Based on this conclusion, equations for rapid computation of mean areal rainfall are derived for this linear case. Results of the linear case are compared with other traditional methods of estimating mean areal rainfall.