Detailed pollution map of an area highly contaminated by mercury containing wastewater from an organic chemical factory in People's Republic of China

A conceptional model integrating geographic information systems (GIS) and social media data for disease exposure assessment

Although previous studies have acknowledged the potential of geographic information systems (GIS) and social media data (SMD) in assessment of exposure to various environmental risks, none has presented a simple, effective and user-friendly tool. This study introduces a conceptual model that integrates individual mobility patterns extracted from social media, with the geographic footprints of infectious diseases and other environmental agents utilizing GIS. The efficacy of the model was independently evaluated for selected case studies involving lead in the ground; particulate matter in the air; and an infectious, viral disease (COVID- 19). A graphical user interface (GUI) was developed as the final output of this study. Overall, the evaluation of the model demonstrated feasibility in successfully extracting individual mobility patterns, identifying potential exposure sites and quantifying the frequency and magnitude of exposure. Importantly, the novelty of the developed model lies not merely in its efficiency in integrating GIS and SMD for exposure assessment, but also in considering the practical requirements of health practitioners. Although the conceptual model, developed together with its associated GUI, presents a promising and practical approach to assessment of the exposure to environmental risks discussed here, its applicability, versatility and efficacy extends beyond the case studies presented in this study.

Mercury (Hg) Contaminated Sites in Kazakhstan: Review of Current Cases and Site Remediation Responses

Mercury (Hg) emissions from anthropogenic sources pose a global problem. In Central Asia, Kazakhstan's central and northern regions are among the most severely Hg-contaminated territories. This is due to two former acetaldehyde (in Temirtau) and chlor-alkali (in Pavlodar) plants, discharges from which during the second half of the 20th century were estimated over 2000 tons of elemental Hg. However, the exact quantities of Hg released through atmospheric emissions to the environment, controlled discharges to the nearby aquatic systems, leakages in the cell plant, and contaminated sludge are still unknown. The present review is the initiation of a comprehensive field investigation study on the current state of these contaminated sites. It aims to provide a critical review of published literature on Hg in soils, sediments, water, and biota of the impacted ecosystems (Nura and Irtysh rivers, and Lake Balkyldak and their surrounding areas). It furthermore compares these contamination episodes with selected similar international cases as well as reviews and recommends demercuration efforts. The findings indicate that the contamination around the acetaldehyde plant site was significant and mainly localized with the majority of Hg deposited in topsoils and riverbanks within 25 km from the discharge point. In the chlor-alkali plant site, Lake Balkyldak in North Kazakhstan is the most seriously contaminated receptor. The local population of both regions might still be exposed to Hg due to fish consumption illegally caught from local rivers and reservoirs. Since the present field data is limited mainly to investigations conducted before 2010 and given the persisting contamination and nature of Hg, a recent up-to-date environmental assessment for both sites is highly needed, particularly around formerly detected hotspots. Due to incomplete site remediation efforts, recommendations given by several researchers for the territories of the former chlor-alkali and acetaldehyde plant site include ex-situ soil washing, soil pulping with gravitational separation, ultrasound and transgenic algae for sediments, and electrokinetic recovery for the former and removal and/or confinement of contaminated silt deposits and soils for the latter. However, their efficiency first needs to be validated. Findings and lessons from these sites will be useful not only on the local scale but also are valuable resources for the assessment and management of similar contaminated sites around the globe.

Distribution and characteristics of methylmercury in surface sediment in Minamata Bay

This study was carried out to evaluate the present-day chemical properties of methylmercury in surface sediment in Minamata Bay where a dredging project was completed 28years ago. Present-day sediment from Minamata Bay consists of sandy silt, and the average loss-on-ignition in surface sediment was 7.0±2.3%. The average methylmercury concentrations in the upper sediment layers were significantly higher than those in the lower sediment layers. Currently, the concentrations in sediments in Minamata Bay do not exceed the Japanese regulatory standard value for mercury. The average concentration of methylmercury in Minamata Bay surface sediment was 1.74±1.0ng/g on a dry weight basis (n=107). The methylmercury concentration in Minamata Bay surface sediment was almost 16 times higher than that in surface sediment from Isahaya Bay surface sediment, which was 0.11±0.045ng/g on a dry weight basis (n=5).

Rapid monitoring of mercury in air from an organic chemical factory in China using a portable mercury analyzer

A chemical factory, using a production technology of acetaldehyde with mercury catalysis, was located southeast of Qingzhen City in Guizhou Province, China. Previous research showed heavy mercury pollution through an extensive downstream area. A current investigation of the mercury distribution in ambient air, soils, and plants suggests that mobile mercury species in soils created elevated mercury concentrations in ambient air and vegetation. Mercury concentrations of up to 600 ng/m(3) in air over the contaminated area provided evidence of the mercury transformation to volatile Hg(0). Mercury analysis of soil and plant samples demonstrated that the mercury concentrations in soil with vaporized and plant-absorbable forms were higher in the southern area, which was closer to the factory. Our results suggest that air monitoring using a portable mercury analyzer can be a convenient and useful method for the rapid detection and mapping of mercury pollution in advanced field surveys.

Relationships between leaching of methylmercury from the soil and the basic characteristics of alkali soil polluted by mercury in Guizhou China

To determine the relationship between soluble methylmercury and soil characteristics which was contaminated by mercury, several experiments were conducted. As a result, a good correlation was founding between the leached methylmercury level from soil and the EC (electronic conductivity) level of soil. Moreover, to grasp the relationship between soluble methylmercury and soluble anions from soil, several anions (Cl(-), NO(3-), SO(4) (2-)) were measured using the ion chromatography method. Although the correlation coefficient was small (r = 0.40), only a correlation between the level of SO(4) (2-) and leached methylmercury was recognized.