No abstract

No abstract

No abstract

No abstract

No abstract

The elevated concentration of arsenic (As) in the groundwaters of many countries worldwide has received much attention during recent decades. This article presents an overview of the natural geochemical processes that mobilize As from aquifer sediments into groundwater and provides a concise description of the distribution of As in different global groundwater systems, with an emphasis on the highly vulnerable regions of Southeast Asia, the USA, Latin America, and Europe. Natural biogeochemical processes and anthropogenic activities may lead to the contamination of groundwaters by increased As concentrations. The primary source of As in groundwater is predominantly natural (geogenic) and mobilized through complex biogeochemical interactions within various aquifer solids and water. Sulfide minerals such as arsenopyrite and As-substituted pyrite, as well as other sulfide minerals, are susceptible to oxidation in the near-surface environment and quantitatively release significant quantities of As in the sediments. The geochemistry of As generally is a function of its multiple oxidation states, speciation, and redox transformation. The reductive dissolution of As-bearing Fe(III) oxides and sulfide oxidation are the most common and significant geochemical triggers that release As from aquifer sediments into groundwaters. The mobilization of As in groundwater is controlled by adsorption onto metal oxyhydroxides and clay minerals. According to recent estimates, more than 130 million people worldwide potentially are exposed to As in drinking water at levels above the World Health Organization's (WHO's) guideline value of 10 μg/L. Hence, community education to strengthen public awareness, the involvement and capacity building of local stakeholders in targeting As-safe aquifers, and direct action and implementation of best practices in identifying safe groundwater sources for the installation of safe drinking water wells through action and enforcement by local governments and international water sector professionals are urgent necessities for sustainable As mitigation on a global scale.

Purpose Serpentine soils derived from ultramafic rocks release elevated concentrations of toxic heavy metals into the environment. Hence, crop plants cultivated in or adjacent to serpentine soil may experience reduced growth due to phytotoxicity as well as accumulate toxic heavy metals in edible tissues. We investigated the potential of biochar (BC), a waste byproduct of bioenergy industry in Sri Lanka, as a soil amendment to immobilize Ni, Cr, and Mn in serpentine soil and minimize their phytotoxicity. Materials and methods The BC used in this study was a waste byproduct obtained from a Dendro bioenergy industry in Sri Lanka. This BC was produced by pyrolyzing Gliricidia sepium biomass at 900°C in a closed reactor. A pot experiment was conducted using tomato plants (Lycopersicon esculentum L.) by adding 1, 2.5, and 5 % (w/w) BC applications to evaluate the bioavailability and uptake of metals in serpentine soil. Sequential extractions were utilized to evaluate the effects of BC on bioavailable concentrations of Ni, Cr, and Mn as well as different metal fractionations in BCamended and BC-unamended soil. Postharvest soil in each pot was subjected to a microbial analysis to evaluate the total bacterial and fungal count in BC-amended and BCunamended serpentine soil. Results and discussion Tomato plants grown in 5 % BCamended soil showed approximately 40-fold higher biomass than that of BC-unamended soil, whereas highly favorable microbial growth was observed in the 2.5 % BC-amended soil. Bioaccumulation of Cr, Ni, and Mn decreased by 93-97 % in tomato plants grown in 5 % BC-amended soil compared to the BC-unamended soil. Sequentially extracted metals in the exchangeable fraction revealed that the bioavailabile concentrations of Cr, Ni, and Mn decreased by 99, 61, and 42 %, respectively, in the 5 % BC-amended soil. Conclusions Results suggested that the addition of BC to serpentine soil as a soil amendment immobilizes Cr, Ni, and Mn in serpentine soil and reduces metal-induced toxicities in tomato plants.

Involuntary resettlement caused by dam construction, especially in developing countries, is being criticized as an additional cause of impoverishment of the poor population being resettled. Despite current improvements in planning and implementation of involuntar y resettlement, there is little experience or research on the medium-to long-term consequences of involuntary resettlement on those being resettled.Within the comprehensive water resource development programme in Sri Lanka under the Mahaweli Accelerated Development Programme, Kotmale Dam was constructed in 1985 for the purpose of hydroelectric power generation and irrigation water supply. Construction of the dam caused ≈ 3000 households to be evacuated and relocated. There were two resettlement alternatives for the families being affected by the dam construction project. The first was to stay close to the reservoir, and receive smaller land plots. The other was to settle in newly developed areas for Mahaweli Development Programme, being located >100 km from original villages, but receive larger, irrigated land plots. In order to determine the consequences after 25 years of the resettlement caused by construction of Kotmale Dam, these authors conducted socioeconomic interview surveys of ≈250 households in three resettlement areas, including Mahaweli System H, System B, System C and villages located near the reservoir site.The study results indicated that the majority of the resettlers perceived their livelihoods as being improved after their resettlement. Furthermore, the majority of them expressed their satisfaction regarding their resettlement choices and their current livelihoods, either in the resettlement sites located near the reservoir or in resettlement sites located far from the original settlement sites. However, their satisfaction is usually based on different perceptions on the part of the resettlers that reflect different strategies for coping with involuntary resettlement. The major factors affecting the choices of resettlers were land ownership and/or the educational opportunities for their children. These sur vey results indicate that the resettled people made conscious choices for their future, especially for their children. For future resettlement programmes, these authors propose that it is important that the considerations of future generations be incorporated in a feasible, sustainable manner, particularly in regard to educational opportunities.