Status of pesticide residues in water, sediment, and fishes of Chilika Lake, India.

Chilika Lake is the largest coastal lagoon in Asia and the second largest in the world covering an area of 1100 km2 and spread over three districts of Odisha state of India. It is the first Indian wetland designated as a wetland of international importance under the Ramsar Convention in 1981. The lake ecosystem sustains large and diversified resources of plants and animals including fisheries. Pollution of the ecosystem caused by residues of pesticides originating from different sources was assessed through multiple sampling from 2012 to 2016 from three potential sites of contamination, viz., Palur Bridge, Daya River Estuary, and Makara River. Incidence of organochlorinated (OC) pesticide residues was noticed in about 25% water samples. HCH (α, γ&δ), DDD (op|), DDE (op|&pp.|) and heptachlor were the OCs detected in concentration varying from 0.025 to 23.4 µg/l. None of the eight targeted synthetic pyrethroid (SP) pesticides was found in water, but among the organophosphates (OP), chlorpyrifos (0.019-2.73 µg/l), and dichlorvos (0.647 µg/l) were recorded. In sediment samples, residues of OC or OP pesticides were not present, but one SP pesticide was recorded. Fish samples were contaminated to the extent of 55%, mostly with residues of OCs and OPs and less with SPs. However, their concentrations were below the permissible limit, so there was no direct threat of health hazards to humans.

Emission of greenhouse gases and soil carbon sequestration in a riparian marsh wetland in central Ohio.

Wetlands are a C sink, but they also account for a large natural source of greenhouse gases (GHG), particularly methane (CH4). Soils of wetlands play an important role in alleviating the global climate change regardless of the emission of CH4. However, there are uncertainties about the amount of C stored and emitted from wetlands because of the site specific factors. Therefore, the present study was conducted in a temperate riverine flow-through wetland, part of which was covered with emerging macrophyte Typhus latifolia in central Ohio, USA, with the objective to assess emissions of GHGs (CH4, CO2, N2O) and measure C and nitrogen (N) stocks in wetland soil in comparison to a reference upland site. The data revealed that CH4 emission from the open and vegetated wetland ranged from 1.03-0.51 Mg C/ha/y and that of CO2 varied from 1.26-1.51 Mg C/ha/y. In comparison, CH4 emission from reference upland site was negligible (0.01 Mg C/ha/y), but CO2 emission was much higher (3.24 Mg C/ha/y). The stock of C in wetland soil was 85 to 125 Mg C/ha up to 0.3 m depth. The average rate of emission was 2.15 Mg C/ha/y, but the rate of sequestration was calculated as 5.55 Mg C/ha/y. Thus, the wetland was actually a C sink. Emission of N2O was slightly higher in vegetated wetland (0.153 mg N2O-N/m2/h) than the open wetland and the reference site (0.129 mg N2O-N/m2/h). Effect of temperature on emission of GHGs from the systems was also studied.

Poor efficacy of herbicides in biochar-amended soils as affected by their chemistry and mode of action.

We evaluated wheat straw biochar produced at 450°C for its ability to influence bioavailability and persistence of two commonly used herbicides (atrazine and trifluralin) with different modes of action (photosynthesis versus root tip mitosis inhibitors) in two contrasting soils. The biochar was added to soils at 0%, 0.5% and 1.0% (w/w) and the herbicides were applied to those soil-biochar mixes at nil, half, full, two times, and four times, the recommended dosage (H(4)). Annual ryegrass (Lolium rigidum) was grown in biochar amended soils for 1 month. Biochar had a positive impact on ryegrass survival rate and above-ground biomass at most of the application rates, and particularly at H(4). Within any given biochar treatment, increasing herbicide application decreased the survival rate and fresh weight of above-ground biomass. Biomass production across the biochar treatment gradient significantly differed (p<0.01) and was more pronounced in the case of atrazine than trifluralin. For example, the dose-response analysis showed that in the presence of 1% biochar in soil, the value of GR(50) (i.e. the dose required to reduce weed biomass by 50%) for atrazine increased by 3.5 times, whereas it increased only by a factor of 1.6 in the case of trifluralin. The combination of the chemical properties and the mode of action governed the extent of biochar-induced reduction in bioavailability of herbicides. The greater biomass of ryegrass in the soil containing the highest biochar (despite having the highest herbicide residues) demonstrates decreased bioavailability of the chemicals caused by the wheat straw biochar. This work clearly demonstrates decreased efficacy of herbicides in biochar amended soils. The role played by herbicide chemistry and mode of action will have major implications in choosing the appropriate application rates for biochar amended soils.

Organochlorine pesticide residues in bovine milk.

Monitoring of bovine milk of different places in Bundelkhand region of India was carried out to evaluate the status of organochlorine pesticide (OCP) residues. Out of a total of 325 samples 206 (63.38%) were contaminated with residues of different OCPs. The average concentration of total HCH was 0.162 mg/kg. Among the different HCH isomers the frequency of occurrence of alpha-isomer was maximum followed by delta-, gamma- and beta. Endosulfan (alpha, beta, sulfate) was detected in 89 samples with mean concentration of 0.0492 mg/kg while total DDT comprising of DDT, DDE and DDD was present in 114 samples having mean concentration of 0.1724 mg/kg. Dicofol was positive in 17 samples.

Environmental transformation of triadimefon in water and on plant leaf surface.

Phototransformation of triadimefon was studied in aqueous solution and on plant leaf surface under natural and simulated conditions. Photoproducts such as 4-chlorophenol, 1-(4-chlorophenoxy)-3,3-dimethyl-1-(1,2,4-triazole-1-yl)-butan-2-ol and 1-phenoxy-3,3-dimethyl-but-2-one were identified on leaf as well as in aqueous solution. A new photoproduct product 1-(4-chlorophenoxymethyl)-1,2,4-triazole was identified only on the leaf surface. The rate of degradation was more in tap water as compared to rain and distilled water.