Land use impact on soil quality in eastern Himalayan region of India

Quantitative assessment of soil quality is required to determine the sustainability of land uses in terms of environmental quality and plant productivity. Our objective was to identify the most appropriate soil quality indicators and to evaluate the impact of six most prevalent land use types (natural forestland, cultivated lowland, cultivated upland terrace, shifting cultivation, plantation land, and grassland) on soil quality in eastern Himalayan region of India. We collected 120 soil samples (20 cm depth) and analyzed them for 29 physical, chemical, and biological soil attributes. For selection of soil quality indicators, principal component analysis (PCA) was performed on the measured attributes, which provided four principal components (PC) with eigenvalues >1 and explaining at least 5 % of the variance in dataset. The four PCs together explained 92.6 % of the total variance. Based on rotated factor loadings of soil attributes, selected indicators were: soil organic carbon (SOC) from PC-1, exchangeable Al from PC-2, silt content from PC-3, and available P and Mn from PC-4. Indicators were transformed into scores (linear scoring method) and soil quality index (SQI) was determined, on a scale of 0–1, using the weighting factors obtained from PCA. SQI rating was the highest for the least-disturbed sites, i.e., natural forestland (0.93) and grassland (0.87), and the lowest for the most intensively cultivated site, i.e., cultivated upland terrace (0.44). Ratings for the other land uses were shifting cultivation (0.60)?>?cultivated low land (0.57)?>?plantation land (0.54). Overall contribution (in percent) of the indicators in determination of SQI was in the order: SOC (58 %)?>?exch. Al (17.1 %)?>?available P (8.9 %)?>?available Mn (8.2 %)?>?silt content (7.8 %). Results of this study suggest SOC and exch. Al as the two most powerful indicators of soil quality in study area. Thus, organic C and soil acidity management holds the key to improve soil quality under many exploitatively cultivated land use systems in eastern Himalayan region of India.     

Climate risk insurance in Pacific Small Island Developing States: possibilities,challenges and vulnerabilities—a comprehensive review

Climate change has become one of the most compelling fields of empirical research over the last couple of decades, partly due to its socio-economic impacts. Using a meta-analysis of 235 peer-reviewed articles published between January 2010 and July 2020, this paper appraises climate change adaptation (CCA) research in Nepal and draws lessons for future adaptation planning. The number of research is observed to have increased significantly in recent years (2015–2020) although there is no consistent pattern over the review period and at the thematic level. Findings submit that the agriculture and food security has the highest number of publications (37%) followed by gender equality and social inclusion (18%) and forest, biodiversity and watershed management (16%). There are no studies found in rural and urban settlement theme. Geographic distribution of CCA studies revealed that over 40% studies were carried out from central Nepal, while no study was conducted in ten districts of eastern and western Nepal. The study focus was also discrete, and the perception and attitude and impact assessment of climate change were common agendas; however, the drivers of change and options for adaptation were understudied. CCA with multipronged initiatives provide a broader understanding of dynamics and governance of climate change that not only affects rural livelihoods, but also influences regional and global environments and biodiversity.

     

Oxidative destabilization of dissolved organics and E. coli in domestic wastewater through immobilized cell reactor system

Domestic wastewater contains a considerable amount of pathogenic organisms besides non-biodegradable organics. The conventional technologies followed for the treatment of domestic wastewater are less efficient in removing pathogenic organisms despite substantial removal of dissolved organics. The focal theme of the present investigation was to use a chemo-autotrophic activated carbon oxidation (CAACO) system, an immobilized cell reactor using chemoautotrophs (Bacillus sp.) for the treatment of domestic wastewater. The oxidation of organics and Escherichia coli in wastewater is controlled by the parameters space time, O(2)/COD, bed height and cod loading. The scheme comprised of anaerobic treatment, sand filtration and CAACO treatment removed BOD. COD, Total organic carbon (TOC), dissolved protein, total Kjeldhal nitrogen (TKN) and bacterial count (most probable number (MPN)) by 81%, 92%, 84%, 94%, 93% and 99.9997%, respectively. The low concentration of E. coli in the CAACO-treated wastewater was completely eliminated through UV irradiation in 3 min at 254 nm.     

Experimental and statistical analyses to characterize in-vehicle fine particulate matter behavior inside public transit buses operating on B20-grade biodiesel fuel

This paper presents results from an in-vehicle air quality study of public transit buses in Toledo, Ohio, involving continuous monitoring, and experimental and statistical analyses to understand in-vehicle particulate matter (PM) behavior inside buses operating on B20-grade biodiesel fuel. The study also focused on evaluating the effects of vehicle’s fuel type, operating periods, operation status, passenger counts, traffic conditions, and the seasonal and meteorological variation on particulates with aerodynamic diameter less than 1 micron (PM_1.0). The study found that the average PM_1.0 mass concentrations in B20-grade biodiesel-fueled bus compartments were approximately 15 μg m^?3, while PM_2.5 and PM₁₀ concentration averages were approximately 19 μg m^?3 and 37 μg m^?3, respectively. It was also observed that average hourly concentration trends of PM_1.0 and PM_2.5 followed a “μ-shaped” pattern during transit hours.Experimental analyses revealed that the in-vehicle PM_1.0 mass concentrations were higher inside diesel-fueled buses (10.0–71.0 μg m^?3 with a mean of 31.8 μg m^?3) as compared to biodiesel buses (3.3–33.5 μg m^?3 with a mean of 15.3 μg m^?3) when the windows were kept open. Vehicle idling conditions and open door status were found to facilitate smaller particle concentrations inside the cabin, while closed door facilitated larger particle concentrations suggesting that smaller particles were originating outside the vehicle and larger particles were formed within the cabin, potentially from passenger activity. The study also found that PM_1.0 mass concentrations at the back of bus compartment (5.7–39.1 μg m^?3 with a mean of 28.3 μg m^?3) were higher than the concentrations in the front (5.7–25.9 μg m^?3 with a mean of 21.9 μg m^?3), and the mass concentrations inside the bus compartment were generally 30–70% lower than the just-outside concentrations. Further, bus route, window position, and time of day were found to affect the in-vehicle PM concentrations significantly. Overall, the in-vehicle PM_1.0 concentrations inside the buses operating on B20-grade biodiesel ranged from 0.7 μg m^?3 to 243 μg m^?3, with a median of 11.6 μg m^?3.Statistical models developed to study the effects of vehicle operation and ambient conditions on in-vehicle PM concentrations suggested that while open door status was the most important influencing variable for finer particles and higher passenger activity resulted in higher coarse particles concentrations inside the vehicle compartments, ambient PM concentrations contributed to all PM fractions inside the bus irrespective of particle size.     

Sediment quality,elemental bioaccumulation and antimicrobial properties of mangroves of Indian Sundarban

Environmental Geochemistry and Health - Mangroves have wide applications in traditional medicines due to their several therapeutic properties. Potentially toxic elements (PTEs), in mangrove...     

An Improved Rating System for Assessing Surface Water Contamination Potential from MSW Landfills

Leachate emission from uncontrolled municipal solid waste landfills (referred to as waste sites in the present study) is a major threat to the environment and living beings in its vicinity. Surface water contamination potential resulting from leachate may be used as one of the criteria for prioritization of sites for remediation purposes. The existing hazard rating systems that prioritize waste sites considering surface water contamination potential as one of the criteria are mainly suited for the developed countries where these were developed initially. In developing countries like India, the set of conditions differ from those in developed countries, and therefore the existing systems may not be suitable for developing countries. Thus in the present study, an improved system is proposed to assess surface water contamination potential from MSW sites. The system is based on the concept of Source, Pathway and Receptor. The proposed system employs parameters derived from the review of existing rating systems and selects their best and worst values based on literature review, design standards and field conditions. The importance weights of the system parameters have been decided based on expert judgment using Delphi technique. Sensitivity analysis of the system shows that the improved system is more sensitive than the existing systems for the site conditions encountered in developing countries. Monte Carlo analysis of the proposed system confirms the spread of the scores obtained from the system over the full scale of 0–1000. The improved system is compared with existing systems by applying it to waste sites from metropolitan cities of India and performing clustering analysis on the rating scores. The clustering analysis shows that the rating scores from the improved system are less clustered as compared to the scores from the existing systems. This demonstrates that the improved system makes a better tool to distinctly prioritize the waste sites for remediation purpose.     

Arsenic in groundwater in six districts of West Bengal,India

Arsenic in groundwater above the WHO maximum permissible limit of 0.05 mg l^–1 has been found in six districts of West Bengal covering an area of 34 000 km² with a population of 30 million. At present, 37 administrative blocks by the side of the River Ganga and adjoining areas are affected. Areas affected by arsenic contamination in groundwater are all located in the upper delta plain, and are mostly in the abandoned meander belt. More than 800 000 people from 312 villages/wards are drinking arsenic contaminated water and amongst them at least 175 000 people show arsenical skin lesions. Thousands of tube-well water in these six districts have been analysed for arsenic species. Hair, nails, scales, urine, liver tissue analyses show elevated concentrations of arsenic in people drinking arsenic-contaminated water for a longer period. The source of the arsenic is geological. Bore-hole sediment analyses show high arsenic concentrations in only few soil layers which is found to be associated with iron-pyrites. Various social problems arise due to arsenical skin lesions in these districts. Malnutrition, poor socio-economic conditions, illiteracy, food habits and intake of arsenic-contaminated water for many years have aggravated the arsenic toxicity. In all these districts, major water demands are met from groundwater and the geochemical reaction, caused by high withdrawal of water may be the cause of arsenic leaching from the source. If alternative water resources are not utilised, a good percentage of the 30 million people of these six districts may suffer from arsenic toxicity in the near future.     

Influence of microbial and synthetic surfactant on the biodegradation of atrazine

The present study reports the effect of surfactants (rhamnolipids and triton X-100) on biodegradation of atrazine herbicide by strain A6, belonging to the genus Acinetobacter. The strain A6 was able to degrade nearly 80 % of the 250-ppm atrazine after 6 days of growth. The bacterium degraded atrazine by de-alkylation process. Bacterial cell surface hydrophobicity as well as atrazine solubility increased in the presence of surfactant. However, addition of surfactant to the mineral salt media reduced the rate and extent of atrazine degradation by decreasing the bioavailability of herbicide. On the contrary, addition of surfactant to atrazine-contaminated soil increased the rate and extent of biodegradation by increasing the bioavailability of herbicide. As compared to triton X-100, rhamnolipids were more efficient in enhancing microbial degradation of atrazine as a significant amount of atrazine was removed from the soil by rhamnolipids. Surfactants added for the purpose of hastening microbial degradation may have an unintended inhibitory effect on herbicide degradation depending upon contiguous condition, thus highlighting the fact that surfactant must be judiciously used in bioremediation of herbicides.