Spatial distribution of arsenic in groundwater in the northwestern Hanoi

Arsenic contamination in groundwater is commonly found in alluvial plains of major river basins, in which the Red river delta has also been reported to be contaminated with high levels of arsenic. In this study, groundwater from 50 household wells was collected to study the spatial distribution of arsenic in northwestern Hanoi. The results showed that arsenic concentration in groundwater varied in a wide range of less than 5 to 334 μg/l, of which up 62% of the wells exceeded the WHO guideline value of 10 μg/l for arsenic content in drinking water. Arsenic groundwater in this area is unevenly distributed throughout the area, high arsenic concentrations are found in a narrow band between Red river and Day river. This pattern of arsenic distribution is strongly related to the sediment age, sedimentary processes, and it is also modified by local groundwater flow parts and the occurrence of hydraulic connection between aquifers, which are observed in the study area. Arsenic is released into the groundwater during the reductive dissolution of arsenic-bearing minerals under the presence of organic matter.

Distribution of Arsenic in Fresh and Weathered Rocks in Sri Lanka

This study was carried out to determine the distribution of arsenic, which may slowly harm human health, in the weathered rocks of different parent rocks in the country. 293 samples were collected from different crystalline rocks and in-situ weathered formations above the particular parent rock in 50 localities. Selected minor elements (including arsenic) were analysed by X-ray fluorescence spectrometry on RIGAKU KG-X system (Japan). Results indicated that the maximum arsenic amount in the fresh rock was 12 and 48 ppm in completely weathered rocks. About 86.9% of fresh rocks showed less than 5 ppm of arsenic, while 89.8% of their weathered grades showed the arsenic concentration to be less than 10 ppm. Average arsenic in all fresh rock samples was 3.5ppm (lowest); it was 7.6 ppm (highest) in residual soils. This is the normal condition of arsenic distribution worldwide. Under this condition, the arsenic concentration in natural groundwater in the residual soil areas should be below the acceptable limit. Therefore, the amount of arsenic released from parent rocks and their weathered products due to natural geological processes is very low in Sri Lanka.

Antimony and arsenic distribution and impacts at a derelict antimony mine in Scotland

<p>Mining activities are acknowledged to introduce contaminants into localised environments and cause wider spread diffuse pollution. The concentration, distribution and fate of arsenic (As) and antimony (Sb) were studied at the former metalliferous Louisa Mine at Glendinning, Scotland. The associated deposit is one of very few able to produce Sb in the UK and was mined for three brief periods between 1793 and 1922.  </p><p>The remnants of the mine consist of the ore processing area and two spoils. Soils withing these zones as well as around the mine were sampled and complemented by water samples from the adjacent stream, the Glennshanna Burn. All samples were subsequently analysed to map the distribution of contamination and identify pollution sources. The maximum concentrations of As and Sb, 15490 and 1504.2 mg kg<sup>−1</sup> respectively, were determined in soils associated with the ore processing area and spoil heaps. Anthropogenic activities also redistributed As and Sb within these mine zones and altered their relative ratios. The fractions of dissolved As and Sb in soils were < 1 and < 5% of total soil content, respectively, confirming findings of previous studies that As and Sb are relatively immobile. Yet, the concentrations of As and Sb released by soils exceeded regulatory limits.</p><p>Concentrations of As and Sb in surface water in the immediate vicinity of the mine were impacted by a gully discharge, but rapidly diluted. While the concentrations affected by the run-off waters did not exceed EU environmental standards for freshwater, the concentrations of As and Sb sharply increased to 11.43 ± 3.43 and 9.28 ± 0.59 μg l<sup>−1</sup>, respectively, approximately 100 m downstream of the mine site. The unaltered As to Sb ratios in water samples suggested a geogenic source of contamination.</p><p>While there is a justifiable concern about the soil pollution caused by the historic mining in the studied area, the Glenshanna Burn is affected more by indigenous geochemical processes than the derelict mine.</p>