Heavy metals and As (HMs) pollution in mining areas are a widespread environmental concern. In this study, ground water, surface water, and sediment samples around the Dexing area, one of the largest Cu-polymetallic ore clusters in China, were collected to examine the concentrations and distributions of As, Cd, Cr, Cu, Hg, Pb, and Zn. Pollution indices, geo-accumulation index, and potential ecological risk index were used to estimate the pollution characteristics and ecological risk of HMs. The results show that the major pollutants in the surface water were Cd, Cu, Zn, and Pb, while the dominant ecological risk of HMs in the sediments originated from Cu, As, Hg, and Cd. Moreover, HMs in the surface water and sediments exhibited substantial spatial heterogeneity in the study area, indicating a severely disturbed environment due to mining activities. The proportions of HM pollutions were higher in the Dexing River and its tributaries than in the Le’an River and its tributaries. The surface water pollution was predominant at the tributaries closest to the mine area, while the sediment contamination has been expanded several kilometers downstream of the major rivers. Overall, the ecological risk of HMs was higher in the sediments than in the surface water.

Soils derived from black shale enriched in heavy metals pose risks to the environment and human health. Eighty sets of soil–rice samples were collected in northwest Zhejiang, China. The results showed significant enrichment of As, Cd, Pb, and Zn in the studied soil. Sequential extraction data indicated that Cd had relatively high bioavailability. Thirty-four percent of the rice samples exceeded the heavy metal pollution thresholds of national food safety standards. A comprehensive evaluation of soil heavy metals using the potential ecological risk index (RI) revealed low-to-moderate-grade risk. Risk assessment code (RAC) levels decreased as follows: Cd > Ni > Zn > Cr > Cu > Pb > As > Hg. The RAC of Cd was high and very high risk, whereas those of others were no or low risk. Cd was the major contributor to the environmental risk based on the total heavy metal concentration, toxicity, and chemical fractions. The health risk to the local populace was assessed using the method recommended by the USEPA. Local people may experience both non-carcinogenic and carcinogenic health risks, and children face greater health risks than adults. As, Cd, and Pb are the most significant contributors to non-carcinogenic health risks, and Cd is the main carcinogenic risk. In conclusion, special attention should be given to heavy metal pollution in black shale-derived soils.

Spatial–temporal variation in soil organic carbon is an important factor for national targets to mitigate climate change and land degradation impacts. In this research, we took Guangdong Province of China as the study area, evaluated the spatial–temporal distributions of soil organic carbon using data from three China Geochemical Baseline projects (conducted in 2009, 2016, and 2023, respectively), and quantified the main driving factors of spatial–temporal variations in soil organic carbon using the random forest algorithm, further predicting the density and inventories of soil organic carbon. The results demonstrate that the mean value of SOC in Guangdong in 2009 was 0.81%; in 2016 it was 1.13%; and in 2023 it was 1.02%. The inventories of soil organic carbon (0–30 cm) in Guangdong Province were 0.61 Pg in 2009, 0.74 Pg in 2016, and 0.62 Pg in 2023. Soil in Guangdong acted as a carbon sink from 2009 to 2023 as a whole, and the most important driving force behind spatial–temporal variations in soil organic carbon was temperature, followed by precipitation and vegetation cover.

The geoelectrochemical extraction method is effective for locating deep concealed deposits, but research on the particle size distribution of its anomaly-causing substances remains limited. To address this, 20 sampling points were established along the No. 20 exploration profile at the Tongjiangling Copper Deposit in Jiangxi Province. Using consistent technical conditions, geoelectrochemical measurements were compared across filter membranes/papers with pore sizes of 0.22 μm, 0.45 μm, 1 μm, 3 μm, and qualitative medium-speed filter paper (approx. 20–30 μm). The results are as follows: (1) The 20–30 μm filter paper effectively detected anomalies corresponding to both shallow and deep concealed ore bodies, whereas smaller pore sizes only revealed shallow ore bodies. (2) Element content and anomaly contrast were significantly higher with the 20–30 μm filter paper compared to smaller pore sizes. (3) Geoelectrochemical anomalies originate from various surface soil substances, which may exist independently or be adsorbed onto particles of different sizes. The applied electric field mobilizes these charged particles, enabling their adsorption onto the collector and acquisition of deep mineralization anomalies. (4) For similar landscapes and deposit types, using filter paper with a pore size of approximately 20–30 μm is recommended to effectively capture deep ore body anomalies while reducing analytical complexity.