A Comprehensive Exploration on Pollution Characteristics and Ecological Risks of Heavy Metals in Surface Paddy Soils around a Large Copper Smelter, Southeast China

To assess heavy metal pollution and ecological risk, a total of 28 surface paddy soil samples were collected and analyzed around a famous copper smelter in Guixi, China. The results showed that all sites were heavily contaminated by both Cu and Cd, compared with soil background values, whose average concentrations exceeded the standard by 5.7 and 12.3 times, respectively, posing a slight ecological risk related to Cu (potential ecological risk index <40) and an extremely serious ecological risk related to Cd (potential ecological risk index >320). The risks were also demonstrated through the speciation analyses of Cu (CaCl2-Cu 2.63%, acid-soluble Cu 8.67%, and residual Cu 74.17%, on average) and Cd (CaCl2-Cd 47.30%, acid-soluble Cd 45.02%, and residual Cd 28.87%, on average) in the surface paddy soil, including the use of a CaCl2 extraction procedure and the BCR (Community Bureau of Reference) sequential extraction scheme. Several soil properties (residual carbon, cation exchange capacity, and soil texture) were significantly correlated with soil Cd but made a small contribution to their variability with a poor linear fit because of external Cd input to the soil, while soil total potassium largely influenced the soil Cu species except for residual Cu. Therefore, an effective Cu pollution regulation strategy through soil potassium control is suggested for this smelter soil.

Analysis of Soil Heavy Metal Pollution and Investigation of Dominant Plants in Abandon Gold Ming Area

In recent years, environmental pollution and ecological destruction in mining area has seriously affected the health and survival of surrounding people. To explore the degree of heavy metal pollution in soil of mining areas and phytoremediation strategies, we chose soil and dominant plants in an abandoned gold mining area as the research object. In this study, Arsenic (As) content in soil and plants was measured. The As pollution degree in local areas was evaluated by using geo-accumulation index and potential ecological risk index. And, As content in plants was analyzed by using enrichment coefficient method. The results show that 1) The pulp deposition area has the most serious As pollution of soil and the largest potential ecological risk index. 2) The composition of the plant community in the study area is dominated by herbaceous plants, among which gramineous, composites and legumes are the dominant plant types in the vegetation community restoration in the mining area. 3) The geoaccumulation index is significantly negatively correlated with species diversity index, Shannon-wiener diversity index and Pielou species evenness index. 4) The As content in dominant plants ranges from 0.11 to 15.92 mg/kg. The plants with strong As enrichment ability are Erigeron annuus (L.) Pers., Periploca sepium Bunge, and Setaria viridis (L.) Beauv., which can be considered as As-tolerant plants. This study can provide a basis and reference for plant management of As pollution in local soil.

Ecological Risk Assessment of Cadmium in Karst Lake Sediments Based on Daphnia pulex Ecotoxicology

The background value of cadmium (Cd) in soil and water sediments in the karst area is 0.31 mg kg−1, with a typical high background of cadmium geochemistry. It is well-known that Cd is classified as a highly toxic metal. Therefore, at the Yelang reservoir in Guizhou province, eco-toxicological tests were carried out using Daphnia pulex. The Geo-Accumulation Index and Potential Ecological Risk Index were used to assess the environmental risk of Cd in sediments. The Cd contents in the sediments of Yelang reservoir ranged from 2.51 to 5.23 mg kg−1, while the LC50 values of the acute toxicity test of Daphnia pulex and Cd at 24, 48, 72, and 96 h were 1.17, 0.50, 0.24, and 0.12 mg L−1, respectively, giving a Safe Concentration threshold of Cd of 1.20 × 10−3 mg L−1 in the water body. Based on curve fitting the solid–liquid two-phase distribution model of cadmium in Yelang reservoir was Y = 7.59 × 10−9 × X2.58 (R2 = 0.9995). The safety threshold sediment Cd concentration was 103 mg kg−1, and was much higher than the Cd content in the sediment of the Yelang reservoir. The Geo-Accumulation Index (Igeo 2.432–3.491) results show that the sediments had reached medium-strong or strong risk levels. The Potential Ecological Risk Index (Eri 242.8–505.9) reached a very high or extremely high-risk level. However, due to high concentrations of Ca2+ and Mg2+, and the pH being in the neutral–alkaline range of water body in karst areas, the Daphnia ecotoxicology evaluation method showed slight ecological risk, quite different from other assessment results, thus this method could be considered to use in such areas.

Potential ecological risk index for metals in a grazing area, Guasca, Cundinamarca

The presence of metals in soils used for primary economic activities can negatively impact the environment and public health. This research identified soil contamination by heavy metals (Lead, Copper, Zinc, and Manganese) by examining physical and chemical properties (Phosphorus, Potassium, organic carbon, cation exchange capacity, pH, texture, and bulk density) of the area during the dry and rainy seasons of 2017. Composite samplings of soil were carried out in both seasons, in order to obtain a representative value of the soil in certified laboratories. Thereafter, through interpolation by means of the Kriging method, a spatial scale of metal concentrations was conducted. This led to the conclusion that the study area has an acceptable environmental quality (5.8-6.9) for its current use of grazing. Likewise, the area presents a medium level (75.37), pursuant to the Potential Ecological Risk Index (RI) for the dry season, and a very high risk (195.04) during the rainy season. These estimates are directly related to lead concentrations, introduced to the soil of the area by human development activities and by contributions of parent material to the soil surface layers, through natural processes of weathering.

Spatial Variation in Cadmium and Mercury and Factors Influencing Their Potential Ecological Risks in Farmland Soil in Poyang Lake Plain, China

Due to the irreversibility of heavy metal pollution, the presence of heavy metals in farmland soil is associated with severe ecological risks that endanger both the environment and human health. Cadmium (Cd) and mercury (Hg) are two toxic heavy metals found widely in polluted soil. Cd is not readily fixed in the soil and is therefore easily accumulated by plants, while Hg has a wide range of pollution sources. The aims of this study were to explore the spatial variation in Cd and Hg concentrations in farmland soil in Poyang Lake Plain, China, and to assess their potential ecological risks as influenced by natural and human factors. A total of 283 soil samples were obtained from Fengcheng city, central Jiangxi Province. Data were then analyzed using geostatistics, the potential ecological risk index, Pearson’s correlation analysis, and Geodetector. The results showed moderate variation in soil Cd and Hg concentrations, with a remarkable difference in their spatial distribution. Cd concentrations in the northwest and northeast of Fengcheng were below the regional background level in Jiangxi; in most remaining areas, Cd concentrations were between the regional background level and national risk screening value. Areas with Hg concentrations lower than the regional background level were largely concentrated in the south, east and north of Fengcheng, and gradually increased towards the central, where they exceeded the regional background level but were below the national risk screening value. Overall, the potential ecological risk level of Cd was predominantly low, while that of Hg was moderate. The comprehensive potential ecological risk was low in most areas for both Cd and Hg, with some scattered areas of moderate risk. Moreover, the comprehensive potential ecological risk index of both Cd and Hg was significantly correlated with soil pH, total phosphorous, elevation, distance from a river (p &lt; 0.01), and distance from a road (p &lt; 0.05). The most significant factor influencing the comprehensive potential ecological risk index of these two heavy metals was soil pH of 5.2–5.6, followed by total p ≤ 0.52 mg kg−1. In conclusion, moderate pollution of Cd and Hg occurred in farmland soil in Poyang Lake Plain where their comprehensive potential ecological risk level was generally low and mainly influenced by soil pH and total phosphorous.

Induced changes of pyrolysis temperature on the physicochemical traits of sewage sludge and on the potential ecological risks

Biochar from sewage sludge is a low-cost sorbent that may be used for several environmental functions. This study evaluates the induced effects of pyrolysis temperature on the physicochemical characteristics of sewage sludge (SS) biochar produced at 350 (SSB350), 450 (SSB450) and 600 (SSB600), based on the metal enrichment index, metal mobility index (MMI), and potential ecological risk index (PERI) of Cd, Cu, Pb, and Zn. Increased pyrolysis temperature reduced the biochar concentration of elements that are lost as volatile compounds (C, N, H, O, and S), while the concentration of stable aromatic carbon, ash, alkalinity, some macro (Ca, Mg, P2O5, and K2O) and micronutrients (Cu and Zn), and toxic elements such as Pb and Cd increased. Increasing the pyrolysis temperature is also important in the transformation of metals from toxic and available forms into more stable potentially available and non-available forms. Based on the individual potential ecological risk index, Cd in the SS and SSB450 were in the moderate and considerable contamination ranges, respectively. For all pyrolysis temperature biochar Cd was the highest metal contributor to the PERI. Despite this, the potential ecological risk index of the SS and SSBs was graded as low.

Year over year comparison of sediment quality in the rivers of Eastern Slovakia

Quality is one of the most important risk indicators in river basins. Therefore, monitoring and evaluating water and sediment quality has a very important role in process of risk management. The aim of the monitoring is provide for the sustainability of water bodies and these results are the basis for the risk management in the river catchment area. Hornad, Laborec and Poprad are the rivers in Eastern Slovakia. Hornad and Laborec belongs to basin of Danube and Poprad belongs to basin of Vistula. Sediment sampling was carried out according to ISO 5667-6. Monitoring was carried out in the spring on 2017–2018. The chemical composition of sediments was determined by means of X-ray fluorescence (XRF) using SPECTRO iQ II (Ametek, Germany, 2000). The results of sediment quality evaluated by method PERI revealed that the quality of sediment in 2018 was better than 2017. Results of XRF analysis of sediments were compared with the limited values according to the Slovak Act 188/2003 Coll. of Laws on the application of treated sludge and bottom sediments to fields. It can be state that limit values comparing with Slovak legislation were not exceeding in all sediment samples in rivers in Eastern Slovakia. Based on the monitoring data of sediment quality in the study area, a quantitative analysis of heavy-metal pollution in sediment was conducted using the method of potential ecological risk index (PERI) which is method for evaluate the potential ecological risk of heavy metals. It is based exclusively on chemical parameters of sediments because sediment data show mean integrated values in time, with higher stability than water column parameters; sediments are easily sampled at field work; sediment samples are more representative for time and space scales and analytical data are easily obtained, especially because sediments present high concentrations of contaminants, decreasing the possible errors due to detection limits of the applied analytical method. This method comprehensively considers the synergy, toxic level, concentration of the heavy metals and ecological sensitivity of heavy metals. Potential ecological risk index can be obtained using three basic modules: degree of contamination (CD), toxic-response factor (TR) and potential ecological risk factor (ER). The results show on the basis on potential ecological risk index that the quality of sediment in 2018 is better than 2017. The worst result shows Hornad in 2017. Significant improvement occurred at the sampling point S2 in Hornad in 2018. The best results show Laborec in 2018. The results show on the basis on potential ecological risk index that quality of sediment in 2018 is better than 2017.

Historical Evolution of Sources and Pollution Levels of Heavy Metals in the Sediment of the Shuanglong Reservoir, China

In this study, the concentrations of seven heavy metals (Cr, Ni, Cu, Zn, As, Hg, and Pb) and Pb isotope in a sediment core from the Shuanglong reservoir, Southwestern China, were investigated. Based on the constant rate of supply (CRS) model, the age span of a 60 cm sediment sample was determined to range from the years 1944 to 2015. Combined with chronology and heavy metal content, the evolution of the sources and pollution levels of heavy metals showed a changing trend composed of various stages. The sources of heavy metals transitioned from natural origins in 1944–1964 to industrial origins in 1965–2004. The subsequent reduction in heavy metal content was mainly due to the vigorous implementation of environmental protection policies from 2005 to 2012. In recent years (2013–2015), the heavy metal content has increased due to frequent human activity. Principal component analysis (PCA), correlation analysis, and the coefficient of variation (CV) analysis indicated that Cr, Ni, Cu, Zn, and As were derived from natural processes, Pb mainly came from automobile manufacturing, and Hg was mainly from industrial sources. The values of the geo-accumulation index (Ig), single pollution index (Pi), and single potential ecological risk index (Er) showed that the contamination of Hg and Pb was slight to moderate. Moreover, the values of the potential ecological risk index (RI), pollution load index (PLI), and Nemerow index (PN) indicated that the Shuanglong reservoir is under low ecological risk.