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This study integrates observations from field and remote sensing data, along with geochemical and isotopic analyses, to assess the environmental impacts of cyanidation and mining activities in the Sukari gold mine (SGM), Eastern Desert, Egypt, in particular, and the orogenic gold deposits of the Arabian-Nubian Shield (ANS) in general. Our findings indicate: (1) groundwater flows south to north in the highly fractured basement aquifer related to the brittle deformation associated with the Najd Fault System; (2) massive gabbroic bodies separate the fractured basement aquifer into east and west conduits; (3) the tailings storage facility (TSF) pond and leach pad were constructed over the west conduit; and (4) cyanide-rich wastewater has leaked downward through tears and cuts in the lining of the TSF pond into the fractured aquifer and cyanide contaminants have migrated northward along the west conduit. Evidence for the latter includes: (1) toxic concentrations of cyanide (total: 0.018-9.4 mg/L; free weak-acid dissociable: 0.003-0.7 mg/L) were observed in groundwater samples north of the TSF pond; (2) similarities in electrical conductivity (EC) values and chloride/bromide (Cl - /Br - ) ratios between groundwater north of the pond (EC: 88.8 mS/cm; Cl - /Br - : 346 to 363) and those of the TSF pond water (mean EC: 99 mS/cm; Cl - /Br - : 242 to 383) were observed; (3) the geochemical (e.g., sodium [Na + ], Cl - ) and isotopic compositions (δ 18 O and δ 2 H values) of groundwater are consistent with mixing of groundwater upgradient from the SGM with isotopically enriched pond water; and (4) cyanide contamination could not have resulted from an overflow of the TSF pond during flash flood events, given that rainfall is negligible and effective flood control systems are in place. Our findings show that the international codes/regulations do not fully address site-specific characteristics and highlight the importance of considering these parameters in mining of orogenic gold deposits in the ANS., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 The Authors. Published by Elsevier B.V. All rights reserved.)

Perchlorate (ClO 4 - ) is a persistent water soluble oxyanion of growing environmental interest. Perchlorate contamination can be a health concern due to its ability to disrupt the use of iodine by the thyroid gland and the production of metabolic hormones. Its widespread presence in surface water and groundwater makes the aquatic environment a potential source of perchlorate exposure. However, the amount of published data on perchlorate origins and water contamination worldwide remains spatially limited. Here, we present an overview of research on perchlorate origins and occurrences in water, and the methodology to distinguish the different perchlorate sources based on isotope analysis. All published ranges of isotopic content in perchlorate from different sources are presented, including naturally occurring and man-made perchlorate source types, as well as the effects of isotope fractionation that accompanies biodegradation processes. An example of a case study in France is presented to emphasize the need for further research on this topic., (Copyright © 2019 Elsevier B.V. All rights reserved.)

A region-wide data analysis on polychlorinated biphenyls (PCBs) in the sediment of the Great Lakes reveals a total accumulation of approximately 300+/-50 tonnes, representing a >30% reduction from the 1980s. Evidence of in situ degradation of sediment PCB was found, with estimated t(1/2) of 11 and 17 years, at two open water locations in Lake Ontario. The relative abundance of heavy homologs as well as para-chlorines decreases with increasing depth, while the opposite is true for medium and light homologs and ortho-chlorines. In Lake Michigan, the vertical pattern features enrichment of heavier congeners and reduction of ortho-chlorines in deeper sediment layers, opposite to the trend in Lake Ontario. PCBs decrease log-linearly with increasing latitude and longitude. Air deposition of PCBs to lake sediment decreases at about 0.077 ng cm(-2) yr(-1) per degree latitude (N) for the geographic region extending from the Great Lakes to within the Arctic Circle.

A total of 199 sediment samples were collected from 16 locations in the five Laurentian Great Lakes, and each was analyzed for 10 congeners of polybrominated diphenyl ethers (PBDEs) as well as selected polychlorinated biphenyls (PCBs). This paper presents a comprehensive analysis on previously published results for individual lakes. The total accumulation of nine tri- to hepta-PBDE congeners (sigma9BDEs) in the sediments of all the Great Lakes was estimated to be approximately 5.2+/-1.1 tonnes, and that of decabromodiphenyl ether (BDE209) was 92+/-13 tonnes, around year 2002. The inventories of sigma9BDEs and major individual PBDE congeners show strong dependence on the latitude of sampling sites, and such dependence is believed to reflect both the influence of urbanization, which shows south-to-north gradient in the region, and the general direction of long-range transport of airborne pollutants in the northern hemisphere. From the 1970s to 2002, the increases in PBDE input flux to the sediments are exponential at all locations, with doubling times (t2) ranging from 9 to 43 years for sigma9BDEs, and from 7 to >70 year for BDE209. The longer t2 values found in sediments compared with those in human and fish in the region suggest the slower response of sediment to emissions. The correlations between the concentrations of sigma9BDEs or BDE209 in surface sediments and latitude are strengthened by normalization of the concentrations with sediment contents of the organic matter or organic carbon, but not soot carbon. Multivariate linear regression equations were developed using data obtained with sediment segments deposited after 1950. All the regressions are statistically significant; and the three independent variables-year of deposition, latitude, and organic matter content of the sediments-account for 73% and 62% of the variations in the concentrations or the fluxes of S9BDEs and BDE209, respectively, in the Great Lakes sediments.