Spatial variability and solubility of barium in a petroleum well-drilling waste disposal area

Impact of acid mine drainage on groundwater hydrogeochemistry at a pyrite mine (South China): a study using stable isotopes and multivariate statistical analyses

Combining environmental isotope analysis with principal component analysis can be an effective method to discriminate the inflows and sources of contamination in mining-affected watersheds. This paper presents a field-scale study conducted at an acid mine drainage (AMD)-contaminated site adjacent to a pyrite mine in South China. Samples of surface water and groundwater were collected to investigate transport in the vadose zone using stable isotopes of oxygen (δ¹⁸O) and hydrogen (δD) as environmental tracers. Principal component analysis of hydrogeochemical data was used to identify the probable sources of heavy metals in the AMD. The heavy metal pollution index (HPI) was applied to evaluate the pollution status of heavy metals in the groundwater. The groundwater associated with the Datai reservoir was recharged by atmospheric precipitation and surface water. On the side near the AMD pond, the groundwater was significantly affected by the soluble metals produced by pyrite oxidation. The concentrations of some metals (Al, Mn, and Pb) in all of the samples exceed the desirable limits prescribed by the World Health Organization (Guidelines for drinking-water quality, 4th edn. World Health Organization, Geneva, 2011). Among them, the concentration of Al is more than 30,000 times higher than the desirable limits prescribed by the World Health Organization (2011), and the concentration of Mn is more than 3000 times higher. The HPI values based on these heavy metal concentrations were found to be 10-1000 times higher than the critical pollution index value of 100. These findings provide a reference and guidance for research on the migration and evolution of heavy metals in vadose zone water in AMD-contaminated areas.

Health risk assessment of potentially toxic elements in soils along the Central Elbe River, Germany

Floodplain soils across Central Elbe River (CER), Germany, vary considerably in potentially toxic element (PTE) content. However, there has never been a comprehensive study that links PTE levels with human health risk for children and adults. Our objective was to determine the contamination of 13 PTEs in 94 soil profiles along CER and assess the associated health risk via diverse indices for adults and children. Of 94 soil profiles, we measured soil properties and total content of arsenic, barium, chromium, copper, nickel, lead, rubidium, tin, strontium, vanadium, zinc, and zirconium using x-ray fluorescence spectrometer (XRF). We calculated the Contamination Factor and the Pollution Load Index (PLI), and assessed the health risk for male and female adults as well as for children. Topsoil median contents of Cr (84 mg kg^-1), Cu (42), Ni (33), and Zn (195) exceeded the Precautionary Values for sandy soils according to the German Federal Soil Protection and Contaminated Sites Ordinance, while As, Pb, and V were 32, 73, and 77 mg kg^-1, respectively. Median topsoil PLI was 1.73, indicating elevated multi-element contamination, with 90th percentile and maximum values being 3.20 and 4.31, respectively. All PTE concentrations were higher in top- compared to subsoils. Also at the 50th percentile the most enriched elements were Sn and As, followed by Zr and Rb, while in the 90th percentile Sn and As were followed by Zn, Pb and Cu. Median children's hazard index (HI) was higher than unity (HI = 2.27) and the 90th percentile was 5.53, indicating elevated health risk. Adult median HIs were 0.18 for male and 0.21 for female persons. Arsenic was found to be the primary contributor to total risk, accounting of 57.4% of HI in all three-person groupings, with Cr (17.3%) being the second, and V (10.2%) the third. Children's health is at dramatically higher risk than that of adults; also As, Cr, Pb, and V have a predominant role in contamination-related health risks. The presence of V, a less-expected element, among those of major risk contribution, reveals the necessity of monitoring areas at large scale. Our results demonstrate that our study may serve as a model for similar works studying multi-element-contaminated areas in future.