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The distribution and ecological risk of heavy metals in sediments were studied through the systematic collection and analysis of mangrove wetland sediments in Dongzhai Harbor, Hainan. The main insights obtained were as follows: (1) The distribution characteristics and influencing factors of heavy metals in wetland sediments were analyzed by using the inverse-distance weight interpolation method. In terms of spatial distribution, the contents of heavy metals As, Ba, Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb, Sr, Ti, and Zn in the western part of the wetland were significantly higher than in the eastern part. The contents of heavy metals Cd, Co, Cr, Cu, Hg, Mn, Ni, Zn, and Ti near the anthropogenic area were significantly higher than at other points. (2) The pollution sources and ecological risks of heavy metals in wetland sediments were explored by using correlation analysis, cluster analysis, and potential ecological risk index analysis. The results showed that As, Ba, Pb, and Sr mainly originated from natural processes; Co, Cr, Cu, Mn, Ni, Ti, and Zn mainly originated from industry; and agricultural heavy metals mainly originated from Cd and Hg. The ecological risk analysis showed that there were obvious ecological risks of heavy metals in the western and southeastern corners of the wetland, which were both located in the vicinity of land far away from the coastline and near the human activities, and featured mangrove forests with dense vegetation characteristics. [ABSTRACT FROM AUTHOR]

The Hunan region is a high geological background area of black rock series rich in various metallic elements; accordingly, local heavy metal pollution is severe. Previous studies on black shale have primarily focused on the lower Cambrian strata, while research on Carboniferous black shale remains scarce. To better explore the activity law of heavy metals during Carboniferous black shale weathering, this study analyzed the elemental components of samples through field observations of outcrops in the Qiziqiao area of central Hunan province, China using inductively coupled plasma mass spectrometry and X-ray fluorescence spectrometry. The results showed that the heavy metal content of black shale under different degrees of weathering varied greatly, with different heavy metals maintaining distinct migration and enrichment rules throughout this process. The heavy metal content in Carboniferous black shale and soils of central Hunan was generally less than that of the regional lower Cambrian black shale and soil; however, the Cd content in the black shale soil was slightly higher than background values, while the Sr content was substantially higher than background values. Heavy metals V, Cr, Co, Ni, Cu, and Pb were not generally leached or released during weathering, and may undergo relative enrichment or secondary enrichment. Comparatively, Zn, Cd, and Ba can be more readily leached and released, and may undergo secondary enrichment. The lithophilic element Sr tended to leach out overall and expressed strong activity, whereas the chemical activities of the high-field-strength elements, Zr and Hf, were relatively stable. During soil formation, all heavy metal elements save Sr were significantly enriched. The enrichment factor analysis of different degrees of weathered black shale reveals that the heavy metals Ba, Hf, and Sr in black shale soil originate from the parent rock. V, Cr, Co, Ni, Cu, Zn, Cd, and Pb are influenced by both natural and anthropogenic factors, with Cd being significantly impacted by human activities. The evaluation of soil heavy metals using the geoaccumulation index method indicates that V, Cr, Co, Ni, Cu, Zn, Zr, Ba, Hf, and Pb are non-polluted, Cd exhibits moderate pollution, and Sr shows moderately heavy pollution. From a geochemical perspective, it can be inferred that heavy metals in black shale soil are likely to be secondarily enriched in clay and iron oxide minerals. [ABSTRACT FROM AUTHOR]

With the rapid development of the economy, heavy metal soil pollution causes ecosystem deterioration and raises serious concerns. Topsoil samples (n = 205) were collected to investigate the pollution characteristics, risk levels, and pollution sources of heavy metals in the topsoil of eastern Tibet. Heavy metal contents, such as As, Hg, Pb, Cr, Mn, Mo, Ni, Cu, Zn, and Cd, in the soil were tested, and the potential sources were analyzed using correlational and principal component analysis. The results showed high content levels of Cd and Hg, which were 1.42 and 2.45 times higher than the background values of the Tibet Plateau at the beginning of this century, respectively. The enrichment factor (EF), geoaccumulation index (Igeo), and Nemero composite index (PN) showed that Cd and Hg were the main pollutants due to higher traffic flow and mining activities, but the pollution degree was generally not high and was relatively concentrated in the central and northern parts. The results of the principal component analysis showed that the heavy metals in the soil of eastern Tibet were mainly affected by natural factors and traffic factors, and mining activities and agricultural activities also played a certain role. Mn, Cr, Ni, As, Hg, and Cu were mainly affected by natural factors, while Pb, Zn, Cd, and Mo were affected by multiple factors, such as nature and traffic. [ABSTRACT FROM AUTHOR]

The consequences of heavy metal contamination are progressively degrading soil quality in this modern period of industry. Due to this reason, improvement of the soil quality is necessary. Remediation is a method of removing pollutants from the root zone of plants in order to minimize stress and increase yield of plants grown in it. The use of plants to remove toxins from the soil, such as heavy metals, trace elements, organic chemicals, and radioactive substances, is referred to as bioremediation. Biochar and fly ash techniques are also studied for effectiveness in improving the quality of contaminated soil. This review compiles amelioration technologies and how they are used in the field. It also explains how nanoparticles are becoming a popular method of desalination, as well as how they can be employed in heavy metal phytoremediation. [ABSTRACT FROM AUTHOR]

A laboratory method was designed and verified that allows for the testing of alkaline, magnesite-based reactive materials for permeable reactive barriers (PRBs) to remove heavy metals from contaminated groundwater. It was found that caustic calcined magnesia (CCM) with high reactivity and low solubility to remove Cu2+, Zn2+, Ni2+, and Mn2+ cations from mixed aqueous solutions can be prepared by calcination at a suitable temperature and residence time. Regarding the solubility of both the reactive material itself and the precipitates formed, the CCM should contain just a limited content of lime. One way is the calcination of a ferroan magnesite at temperatures above 1000 °C. However, the decrease in pH is accompanied by lower efficiency, attributed to the solid-phase reactions of free lime. A different way is the calcination of magnesite under the conditions when CaCO3 is not thermally decomposed. The virtually complete removal of the heavy metals from the model solution was achieved using the CCM characterised by the fraction of carbonates decomposed of approximately 80% and with the highest specific surface area. CCM calcined at higher temperatures could also be used, but this would be associated with higher consumption of crude magnesite. Under the conditions considered in the present work, the product obtained by the calcination at 750 °C for 3 h appeared to be optimal. The full heavy metal removal was observed in this case using less magnesite, and, moreover, at a lower temperature (resulting, therefore, in a lower consumption of energy for the calcination and material handling). [ABSTRACT FROM AUTHOR]