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Monitoring and assessment of polluting metals in the southeastern mining-impacted region of La Guajira, Colombia

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Technical Report
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The present report discusses the most common methods used for remediating contaminated sediment, the chemistry of mercury and its effect on the sorption of mercury on the sediment. The report also discusses some of the available mathematical models available to predict the fate and transport of mercury in the environment. Finally,the report presents several case studies. The first case study discusses the remediation efforts made at Lavaca Bay, Texas, where past activities have led to contamination of sediment. The second case is on the management of mercury present in Onandoga Lake in Syracuse, New York, and the third case study is on remediation and monitoring of mercury contaminated sediments in Lake Turingen, Sweden
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The goal of the presented research was to evaluate the possible heavy metal pollution in soil by applying Hakanson risk evaluation method with adjusting assessment domain combined with ArcGIS technology. The assessment standards were adjusted based on the amount and types of studied heavy metals. Topsoil samples in mining area were collected and tested the content of five kinds of heavy metals, Arsenic (As), mercury (Hg), copper (Cu), lead (Pb) and zinc (Zn). The area of different risk levels and the area ratio in each township were accurately calculate, and the regions with high pollution risk were further precisely located. The results indicate the following: (1) It was observed that the accuracy of soil-heavy metal assessment in Suxian was evidently improved by using Hakanson potential ecological risk with assessment domain adjustment. (2) The single factor and Nemero pollution indexes showed an evident contamination of five types of heavy metals in Suxian. (3) There is a high index of comprehensive ecological risk in Suxian; approximately 82.9% of Suxian is at a strong (level 3 or higher) risk level, demonstrating serious soil pollution. The quite strong risk region with the portion of 18.33% of total area is primarily concentrated in the area of the large Polymetallic mine and coal mining area. Using the single factor ecological risk index, the distribution of large areas of As and Pb high-risk pollution were explored. More than half of the soil in Suxian presents a strong Hg (level 3 and higher) risk level, and the primary strong ecological risk and quite strong ecological risk townships were identified as well. (4) A more finely characterized pollution status was achieved from this pollution assessment in Suxian based on the township level, rendering the study results a more practical guide and increasing their significance.
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The occurrence, toxicities, and ecological risks of five heavy metals (Pb, Cu, Cd, Zn and Ni) in the sediment of Taihu Lake were investigated in this study. To evaluate the toxicities caused by the heavy metals, the toxicities induced by organic contaminants and ammonia in the sediments were screened out with activated carbon and zeolite. The toxicities of heavy metals in sediments were tested with benthic invertebrates (tubificid and chironomid). The correlations between toxicity of sediment and the sediment quality guidelines (SQGs) derived previously were evaluated. There were significant correlations (p < 0.0001) between the observed toxicities and the total risk quotients of the heavy metals based on SQGs, indicating that threshold effect level (TEL) and probable effect level (PEL) were reliable to predict the toxicities of heavy metals in the sediments of Taihu Lake. By contrast, the method based on acid volatile sulfides (AVS) and simultaneously extracted metals (SEM), such as ∑ SEM/AVS and ∑ SEM-AVS, did not show correlations with the toxicities. Moreover, the predictive ability of SQGs was confirmed by a total predicting accuracy of 77%. Ecological risk assessment based on TELs and PELs showed that the contaminations of Pb, Cu, Cd and Zn in the sediments of Taihu Lake were at relatively low or medium levels. The risks caused by heavy metals in the sediments of northern bay of the lake, which received more wastewater discharge from upper stream, were higher than other area of the lake.
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In the southern part of the Atlantic Forest region, in Santa Catarina, Brazil, coal mining has led to severe degradation, with former mining areas abandoned decades ago without any concern about environmental and social damage. Up to recently, little restoration activity had been developed, despite severe and ongoing environmental degradation that also causes risks to human health. We argue that these areas should be made restoration priority, and that the development of specific restoration actions and measures for sites like these are urgent. To achieve effective restoration planning we must overcome some challenges, such as prioritization of areas for restoration, establishment long-term monitoring, development of realistic goals, avoidance of the use of invasive grasses, and inclusion of human population and their needs into discussion of restoration goals and approached. We recognize that, due to pollution and contamination problems, cost for restoration is a massive challenge in the region, but even higher costs for population and environment are expected if sites would not be restored. Considering the environment and human health risks of areas degraded by coal mining, restoration efforts should be of high priority on all level of governance, and ways should be found to include this into the procedures for prioritization of restoration activities.
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Cerium (Ce) and thorium (Th) are always thought to be chemically similar and have comparable toxic properties on living organisms. In the present study, the acute and chronic toxicity of these two elements to freshwater crustacean Daphnia magna were investigated in the modified reconstituted water (6 mg/L KCl, 123 mg/L MgSO 4 Á 7H 2 O, and 294 mg/L CaCl 2 Á 2H 2 O in Milli-Q water, pH 7.8). It seemed that Ce and Th had comparable acute toxicity on Daphnia: 24/48 h EC 50 for Th and Ce were 7.3/4.7 μM and 16.4/ 10.7 μM, respectively. However, Ce was present as soluble ions while all of Th was present as particulate ThO 2 in the exposure medium. Considering their different chemical forms and bioavailability, the toxic mechanisms of Ce 3 þ and ThO 2 on Daphnia would be totally different. To our knowledge, this is the first time to investigate the aquatic toxicity of thorium and cerium based on their actual chemical speciation in the exposure medium. The results also suggest that more attention should be paid on the detrimental effect of Th in the form of particulate ThO 2 .
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The international coal mining industry has experienced serious recent downturns, particularly in the electricity generating market, with steady declines projected into the future. In the United States, increased production from the natural gas sector has made coal-fired power production less competitive, and natural gas power plants are replacing aging coal-fired plants. As such, many of the larger coal companies are in or have recently been in bankruptcy, leaving all coal mining states in the United States at risk for liabilities from abandoned unreclaimed coal mines. Because of the various laws and regulations surrounding the permitting of coal mines, Kentucky, Maryland, Ohio, Pennsylvania, Virginia, and West Virginia employ some form of alternative bonding systems, and Alaska, Arkansas, Colorado, Illinois, Indiana, Kentucky, New Mexico, Texas, Virginia, West Virginia, and Wyoming employ self-bonding, which allows a coal operator to reduce its secured bond. These alternative bonding systems do not contemplate the risk of a large-scale industry downturn, leaving states at risk for hundreds of millions of dollars of liabilities to reclaim abandoned coal mines and protect the environment and its residents. We examined the reclamation bonds for all coal mines in West Virginia and found that West Virginia faces significant gaps between counties and watershed for the amount of the secured funding for site-specific reclamation. Significant disparities exist such that some residents are much more impacted by the amount of coal mining, as well as the amount of site-specific bonding. We also found that the areas most impacted by the amount of coal mining and reduced site-specific bonding are in the areas with the worst health outcomes. This is a concern for all regions with all types of extractive industries: how to maximize industry while protecting the environment and its residents. Moving forward, states should reconfigure bonding systems to alleviate these risks and burdens on its citizens to prepare for continued declines within the coal industry.