Fractionation and speciation of arsenic in three tea gardens soil profiles and distribution of As in different parts of tea plant (Camellia sinensis L.)

The distribution pattern and fractionation of arsenic (As) in three soil profiles from tea (Camellia sinensis L.) gardens located in Karbi-Anglong (KA), Cachar (CA) and Karimganj (KG) districts in the state of Assam, India, were investigated depth-wise (0-10, 10-30, 30-60 and 60-100 cm). DTPA-extractable As was primarily restricted to surface horizons. Arsenic speciation study showed the presence of higher As(V) concentrations in the upper horizon and its gradual decrease with the increase in soil depths, following a decrease of Eh. As fractionation by sequential extraction in all the soil profiles showed that arsenic concentrations in the three most labile fractions (i.e., water-soluble, exchangeable and carbonate-bound fractions) were generally low. Most arsenic in soils was nominally associated with the organic and Fe-Mn oxide fractions, being extractable in oxidizing or reducing conditions. DTPA-extractable As (assumed to represent plant-available As) was found to be strongly correlated to the labile pool of As (i.e. the sum of the first three fractions). The statistical comparison of means (two-sample t-test) showed the presence of significant differences between the concentrations of As(III) and As(V) for different soil locations, depths and fractions. The risk assessment code (RAC) was found to be below the pollution level for all soils. The measurement of arsenic uptake by different parts of tea plants corroborated the hypothesis that roots act as a buffer and hold back contamination from the aerial parts.     

Long-term effect of rice-based farming systems on soil health

Integrated rice–fish culture, an age-old farming system, is a technology which could produce rice and fish sustainably at a time by optimizing scarce resource use through complementary use of land and water. An understanding of microbial processes is important for the management of farming systems as soil microbes are the living part of soil organic matter and play critical roles in soil C and N cycling and ecosystem functioning of farming system. Rice-based integrated farming system model for small and marginal farmers was established in 2001 at Central Rice Research Institute, Cuttack, Odisha. The different enterprises of farming system were rice–fish, fish–fingerlings, fruits, vegetables, rice–fish refuge, and agroforestry. This study was conducted with the objective to assess the soil physicochemical properties, microbial population, carbon and nitrogen fractions, soil enzymatic activity, and productivity of different enterprises. The effect of enterprises induced significant changes in the chemical composition and organic matter which in turn influenced the activities of enzymes (urease, acid, and alkaline phosphatase) involved in the C, N, and P cycles. The different enterprises of long-term rice-based farming system caused significant variations in nutrient content of soil, which was higher in rice–fish refuge followed by rice–fish enterprise. Highest microbial populations and enzymatic properties were recorded in rice–fish refuge system because of waterlogging and reduced condition prolonged in this system leading to less decomposition of organic matter. The maximum alkaline phosphatase, urease, and FDA were observed in rice–fish enterprise. However, highest acid phosphatase and dehydrogenase activity were obtained in vegetable enterprise and fish–fingerlings enterprise, respectively.     

Photodegradation of the herbicide penoxsulam in aqueous methanol and acetonitrile

Penoxsulam is a triazolopyrimidine sulfonamide group of rice herbicide. The phototransformation of penoxsulam was studied under UV light (lambda max >or= 290 nm) and sunlight in aqueous methanol and acetonitrile solvent system using TiO2 as sensitizer. The rate of photodegradation of penoxsulam in different solvent systems followed first-order kinetics and calculated half-lives was found to be in the range of 51.89-73.41 h and 62.70-97.09 h for UV light and sunlight respectively in the presence or absence of sensitizer. From this study, a total of six photoproducts were identified and characterized on the basis of Q-Tof micromass spectral data. The plausible mechanism of phototransformation involved were hydrolysis, photo oxidation of the sulfonamide group, breaking of sulfonamide bond, loss of amino and sulfonic acid group.     

Effect of arsenic contamination on microbial biomass and its activities in arsenic contaminated soils of Gangetic West Bengal, India

A study was conducted to see the effect of arsenic contamination on soil quality indicators, viz., microbial biomass, soil respiration, fluorescein diacetate and dehydrogenase (DHG) activity in arsenic contaminated soils of West Bengal. All the parameters were significantly and negatively correlated with all the form of arsenic (bioavailable and total) but the microbial metabolic quotient was significantly and positively correlated with all forms of arsenic, indicating arsenic induced stress to the soil microbial community. This may be due to part of the microbial biomass, which is located in the inner parts of the micro-aggregates of soil, which is affected by arsenic accumulates present in soil particles. Linear regression analysis revealed that the bioavailable arsenic exerted greater inhibitory effect on the soil microbial population than the total arsenic content of soils. Water-soluble arsenic showed more inhibitory effect than NaHCO(3) extractable form, in their association with biological properties of the contaminated soils. Water-soluble form of arsenic was much more toxic than insoluble forms. This signified that with increase in bioavailability, the arsenic exerted more inhibitory effect on these parameters. It is thus suggested that the microbial biomass, fluorescein diacetate and dehydrogenase activity alone and expressed on a soil organic matter basis along with the soil respiration parameters can be helpful in assessing the effects of arsenic on the size and activity of microbial biomass in soils.     

PCB 77 dechlorination products modulate pro-inflammatory events in vascular endothelial cells

Persistent organic pollutants such as polychlorinated biphenyls (PCBs) are associated with detrimental health outcomes including cardiovascular diseases. Remediation of these compounds is a critical component of environmental policy. Although remediation efforts aim to completely remove toxicants, little is known about the effects of potential remediation byproducts. We previously published that Fe/Pd nanoparticles effectively dechlorinate PCB 77 to biphenyl, thus eliminating PCB-induced endothelial dysfunction using primary vascular endothelial cells. Herein, we analyzed the toxic effects of PCB congener mixtures (representative mixtures of commercial PCBs based on previous dechlorination data) produced at multiple time points during the dechlorination of PCB 77 to biphenyl. Compared with pure PCB 77, exposing endothelial cells to lower chlorinated PCB byproducts led to improved cellular viability, decreased superoxide production, and decreased nuclear factor kappa B activation based on duration of remediation. Presence of the parent compound, PCB 77, led to significant increases in mRNA and protein inflammatory marker expression. These data implicate that PCB dechlorination reduces biological toxicity to vascular endothelial cells.     

Effect of vermicomposting on calcium,sulphur and some heavy metal content of different biodegradable organic wastes under liming and microbial inoculation

A study was conducted to evaluate the changes in total calcium and sulphur and some heavy metal (Zn, Cu, and Pb) concentration of different organic wastes affected by liming and microorganism inoculation. Vermicomposting was an effective technology for disposal of organic substrates like municipal solid wastes (MSW), possessing comparatively higher concentration of heavy metals. The addition of lime in initial organic substrates significantly (P ≤ 0.05) increased total calcium and total sulphur content of vermicomposts. Inoculation of microorganisms significantly (P ≤ 0.05) reduced the heavy metal content of final products as compared to control. Fungal strains were comparatively more effective in detoxification of heavy metals than B. polymyxa.     

Agriculture,dairy and fishery farming practices and greenhouse gas emission footprint: a strategic appraisal for mitigation

Rising global population would force farmers to amplify food production substantially in upcoming 3–4 decades. The easiest way to increase grain production is through expanding cropping area by clearing uncultivated land. This is attained by permitting deadly loss of carbon (C) stocks, jeopardizing ecosystem biodiversity and deteriorating environmental quality. We aim to propose key agronomical tactics, livestock management strategy and advance approaches for aquaculture to increase productivity and simultaneously reduce the environmental impacts of farming sector. For this, we considered three major sectors of farming, i.e. agriculture, fishery and dairy. We collected literatures stating approaches or technologies that could reduce GHG emission from these sectors. Thereafter, we synthesized strategies or options that are more feasible and accessible for inclusion in farm sector to reduce GHG emission. Having comprehensively reviewed several publications, we propose potential strategies to reduce GHG emission. Agronomic practices like crop diversification, reducing summer fallow, soil organic carbon sequestration, tillage and crop residue management and inclusion of N2-fixing pulses in crop rotations are some of those. Livestock management through changing animals’ diets, optimal use of the gas produced from manures, frequent and complete manure removal from animal housing and aquaculture management strategies to improve fish health and improve feed conversion efficiency could reduce their GHG emission footprint too. Adapting of effective and economic practices GHG emission footprint reduction potential of farming sector could make farming sector a C neutral enterprise. To overcome the ecological, technological and institutional barriers, policy on trade, tax, grazing practice and GHG pricing should be implemented properly.