Assessment of imidacloprid degradation by soil-isolated Bacillus alkalinitrilicus

Imidacloprid is extensively used on a broad range of crops worldwide as seed dressing, soil treatment, and foliar application. Hence, the degradation potential of bacterial strains from sugarcane-growing soils was studied in liquid medium for subsequent use in bioremediation of contaminated soils. The microbe cultures degrading imidacloprid were isolated and enriched on Dorn’s broth containing imidacloprid as sole carbon source maintained at 28 °C and Bacillus alkalinitrilicus showed maximum potential to degrade imidacloprid. Clay loam soil samples were fortified with imidacloprid at 50, 100, and 150 mg kg^?1 along with 45?×?10⁷ microbe cells under two opposing sets of conditions, viz., autoclaved and unautoclaved. To study degradation and metabolism of imidacloprid under these two conditions, samples were drawn at regular intervals of 7, 14, 28, 35, 42, 49, and 56 days. Among metabolites, three metabolites were detected, viz., 6-chloronicotinic acid, nitrosimine followed by imidacloprid-NTG under both the conditions. Total imidacloprid residues were not found to follow the first-order kinetics in both types of conditions. This paper reports for the first time the potential use of pure cultures of soil-isolated native bacterium B. alkalinitrilicus and also its use along with natural soil microflora for remediation of imidacloprid-contaminated soils.     

Alumina-supported oxime for the degradation of sarin and diethylchlorophosphate

1-(4-Chlorophenyl))-N-hydroxymethanimine and cyclohexyl-N-hydroxymethanimine were synthesized and a well-established oxime, i.e., 2-[(hydroxyimino)methyl]-1-methylpyridinium chloride was purchased. Thereafter; all were loaded over Al₂O₃ using incipient wetness technique. The prepared systems were characterized using surface area analyzer, scanning electron microscope, energy dispersive X-ray spectrophotometer, Fourier transform infrared spectrophotometer and thermogravimetric analyzer. Kinetics of the degradation of sarin (GB) and simulant, i.e. diethylchlorophosphate (DEClP) was studied over synthesized oxime impregnated Al₂O₃ and results were compared with well reported oxime impregnated Al₂O₃. Kinetics of reaction was found to be following the pseudo first order reaction kinetics. The order of reactivity of the prepared systems was found to be cyclohexyl-N-hydroxymethanimine/Al₂O₃ > 1-(4-chlorophenyl)-N-hydroxymethanimine/Al₂O₃ > 2-[(hydroxyimino)methyl]-1-methylpyridinium chloride/Al₂O₃ > Al₂O₃. From the reaction kinetics it was observed that the reaction with DEClP was faster than with GB. Cyclohexyl-N-hydroxymethanimine/Al₂O₃ was found to be the most reactive system with half-life of 0.94 and 15 h for DEClP and GB respectively.     

Surveying of aquatic insect diversity of Chandrabhaga river,Garhwal Himalayas

Aquatic insect diversity in the Chandrabhaga, an important headwater stream of Garhwal Himalayas, was surveyed for a period of twelve months (October 1999 to September 2000). All the important physico-chemical environmental variables (temperature, water velocity, hydromedian depth, transparency, turbidity, total dissolved solids, pH, alkalinity, dissolved oxygen, free CO₂, nitrates, phosphates, sodium and potassium) of the aquatic ecosystem were measured monthly for one year. Aquatic insects were sampled from three sites (S₁, S₂ & S₃) of the headwater stream Chandrabhaga. Aquatic insects of Chandrabhaga were represented by the members of the orders of Ephemeroptera, Trichoptera, Coleoptera, Diptera, Plecoptera and Odonata. The maximum density of aquatic insects was recorded in the month of March (4,165 ind. m⁻²) and minimum in the month of August (680 ind. m⁻²). The annual contribution of Trichoptera (38%) and Ephemeroptera (32%) was observed to be maximum, while Odonata contributed minimum (2%) to the total aquatic insect density. The present study on the relationship between physico-chemical environmental variables and the density of aquatic insects revealed that the velocity of water, hydromedian depth, turbidity and dissolved oxygen in addition to composition and texture of the bottom substrates have significant impact on benthic aquatic insects’ density and their diversity. The ecological relevance of the measured hydrological attributes was investigated by composing their degree of correlation with insects density and diversity. The diversity index (Shannon–Weiner) of aquatic insects dwelling in the Chandrabhaga river ranged from 2.54 to 3.86. Some of the natural and anthropogenic environmental factors contributing towards the degradation of the watershed of the Chandrabhaga have been identified, and ameliorative measures for the conservation of the aquatic insect diversity have been suggested.     

Persistence behaviour of imidacloprid and its metabolites in soil under sugarcane

The persistence and metabolism of imidacloprid in soil under sugarcane were studied following application of imidacloprid at 20 and 80 g active ingredient (a.i.) ha^?1. Soil samples were collected at different time intervals (7, 15, 30, 45, 60 and 90 days after application), and the residues of imidacloprid and its metabolites (6-chloronicotinic acid, nitrosimine, imidacloprid-NTG, olefin, urea and 5-hydroxy) were quantified by high-performance liquid chromatography. In soil, the total imidacloprid residues were mainly constituted by the parent compound followed by 6-chloronicotinic acid, nitrosimine and imidacloprid-NTG metabolites. Maximum residues of imidacloprid and its metabolites were 4.29 and 7.81 mg kg^?1 in soil samples collected 7 days after the application of imidacloprid at 20 and 80 g a.i. ha^?1, respectively. At both doses, these residues declined to below the detectable limit in soil after 90 days of application. Olefin, urea and 5-hydroxy metabolites were not detected in soil. Dissipation of total imidacloprid residues did not follow the first-order kinetics with a coefficient of determination value of 0.883 and 0.838 for the recommended dose and four times the recommended dose, respectively. The half-life (T _1/2) value of total imidacloprid was observed to be 10.64 and 10.10 days for the recommended dose and four times the recommended dose, respectively.     

Chemometric characterization of river water quality

Various industrial facilities in the city of Varanasi discharge their effluent mixed with municipal sewage into the River Ganges at different discharge points. In this study, chemometric tools such as cluster analysis and box–whisker plots were applied to interpret data obtained during examination of River Ganges water quality. Specifically, we investigated the temperature (T), pH, total alkalinity, total acidity, electrical conductivity (EC), biochemical oxygen demand (BOD), chemical oxygen demand (COD), dissolved oxygen (DO), nitrate nitrogen (N), phosphate (PO ₄ ^2? ), copper (Cu), cadmium (Cd), chromium (Cr), nickel (Ni), iron (Fe), lead (Pb), and zinc (Zn) in water samples collected from six sampling stations. Hierarchical agglomerative cluster analysis was conducted using Ward’s method. Proximity distance between EC and Cr was the smallest revealing a relationship between these parameters, which was confirmed by Pearson’s correlation. Based on proximity distances, EC, Cr, Ni, Fe, N, COD, temperature, BOD, and total acidity comprised one group; Zn, Pb, Cd, total alkalinity, Cu, and phosphate (PO ₄ ^2? ) were in another group; and DO and pH formed a separate group. These groups were confirmed by Pearson’s correlation (r) values that indicated significant and positive correlation between variables in the same group. Box–whisker plots revealed that as we go downstream, the pollutant concentration increases and maximum at the downstream station Raj Ghat and minimum at the upstream station Samane Ghat. Seasonal variations in water quality parameters signified that total alkalinity, total acidity, DO, BOD, COD, N, phosphate (PO ₄ ^2? ), Cu, Cd, Cr, Ni, Fe, Pb, and Zn were the highest in summer (March–June) and the lowest during monsoon season (July–October). Temperature was the highest in summer and the lowest in winter (November–February). DO was the highest in winter and the lowest in summer season. pH was observed to be the highest in monsoon and the lowest in summer season.     

Vegetation structure, niche width, niche overlap and types of competition in temperate grazingland of Garhwal Himalaya, India

Temperate grazing lands in Garhwal Himalaya are rich in herbaceous vegetation and extensively used for grazing by locally owned livestock. Capillipedium parviflorum is a frequently occurring and dominant grass species under Pine canopy in associate with several herbs. Beside, grazing and extensive fire, interactions among associated species is a determining factor of community structure. In this article the dominant diversity pattern of vegetation in temperate grazing land along two different altitudes and having different slope aspects is described. Interaction between dominant and co-dominant species with their niche appearance and niche overlap measurement was also observed and presented here. South and west facing slopes had maximum species and diversity values while east north facing slopes had higher species dominant. Capillipedium parviflorum and other grasses had maximum niche values and were dominant and co dominant species. Three types of interspecific interaction were observed between species and grasses were observed as succeeding species in all sites of different topographic conditions. Dominant diversity pattern along with resource partitioning and interspecific competition is discussed and presented here.     

Examining Marginalized Communities and Local Conservation Institutions: The Case of Nepal’s Annapurna Conservation Area

In developing countries, participatory conservation initiatives have been criticized for many reasons, mainly for excluding marginalized groups which have led to unequal benefits. Using concepts from the literature on participation, conservation, and political ecology, this research explored the participation of marginal groups, i.e., poor, women, lower caste, and landless, in management institutions in Nepal’s Annapurna Conservation Area. Field work for this research was conducted through the use of interviews and participant observation during August–October 2010. Results show that although marginal groups were involved in local management institutions, their representation was minimal and had not led to meaningful participation or empowerment to influence the decisions being made in conservation and development programs. Our study findings indicate that the involvement of marginal groups in local initiatives is complex and influenced by several factors. The study concludes that the Annapurna Conservation Area Project needs to re-orient its conservation projects by adopting a more inclusive form of participation and move beyond the quota system.     

Neurotoxic and genotoxic effects of methylmercury

The toxic form of methylmercury is of concern in terms of its neurotoxicity, genotoxicity and reproductive toxicity. Extensive research has been carried out on the effects of exposure to high levels of this toxic compound, but this is not true for research on exposure to lower levels. The harmful effects of methylmercury are a cause for concern irrespective of the exposure levels. The problem becomes more serious because of biomagnifications of methylmercury. Disorders may develop during neonatal stage and then develop further during the lifetime. The common effects which can be seen are retarded brain development and permanent disorders like cerebral palsy. This can also cause neurogenerative disorders like Alzheimer’s and Parkinson’s. Research on animals has also shown toxicity. Inorganic Hg was found to be present in brains of neonatal rats, in monkeys prenatal exposure to MeHg resulted in a reduced number of births, and birds laid a lesser number of eggs and the infant mortality rate was higher.