A total of 28,095 surface soil samples were collected in areas with high natural background levels; the potential ecological risk is generally low, and the high-risk area is small and mainly affected by lead–zinc mines. The contribution to the potential ecological risk factor (RI) is as follows: Hg > Cd > As > Pb > Cu > Ni > Cr > Zn, with noncarcinogenic chronic risks of Cr > As > Cd > Pb > Ni > Cu > Hg > Zn; furthermore, dermal contact is the main pathway of exposure causing health risks. The total carcinogenic risks caused by heavy metals were as follows: Cr > Cd > As > Pb; and the risks posed by Cr, Cd, and As were higher than the threshold value (1.0 × 10⁻⁴); people face a higher threat to heavy metals in soils in Zhenxiong, Ludian, Huize, Weixin, and Zhaoyang. The evaluation result of the EPA PMF model shows that the soil heavy metals are mainly composed of five sources, of which basalt, Permian, and Triassic carbonate rock parent material constitute the natural background source, while the mining activities of lead–zinc mines and the emissions of coal burning by residents constitute the anthropogenic source. The contribution was ranked in order of lead–zinc mining (26.7%) > Triassic carbonate (23.7%) > basalt (20.9%) > coal burning and automobile emissions (16.1%) > Permian carbonate (12.6%).

Chishui River is an important ecological security barrier area in the upper reaches of the Yangtze River in China. Therefore, it is of great significance to conduct research on soil and water ecological risks in the Chishui River basin. In this paper, the risk of heavy metals pollution and its control factors was evaluated systematically by using surface water and soil samples from 16 tributaries in the Yunnan section of the Chishui River basin. The method of soil environmental capacity and ecological risk index were studied. The results showed that the average concentration of heavy metals in the surface water of the main stream was in the order of Fe > Mn > Zn > Cu > Pb > Cd > Hg. Except for Hg, all the concentrations of heavy metals were far lower than the Class I water limits in the Environmental Quality Standards for Surface Water (GB3838-2002) issued by the Ministry of Ecology and Environment, PRC. The average concentration of Hg concentration was 0.056 μg·L⁻¹, which was slightly higher than the limit value of Class II. Heavy metals in the surface water were distributed in a point-like manner in the main stream of the Chishui River, which was mainly affected by mining drainage, township sewage, and human production activities. Meanwhile, the environmental capacity study showed that the heavy metals in soil were in the order of Zn > Pb > Cr > Ni > As > Hg > Cu > Cd, and the environmental capacity were significant differences among different soils: purple soil > limestone soil > loess > yellow-brown soil. Soil Cd tended to migrate out of the soil under the control of the occurrence form, vegetation coverage, and human production activities, while Cr, Cu, and Ni tended to accumulate in the soil. The average comprehensive ecological risk index (RI) of heavy metals in all tributaries ranged from 44.86 to 154.15, mainly distributed in medium and low ecological risk. Therefore, it is recommended to dynamically monitor and control these pollution points in the Chishui River basin to prevent the risk of heavy metals from escalating.

Studying surface geochemical anomalies is important for detecting the presence of mineral deposits. However, distinguishing inconspicuous geochemical anomalies is a challenge for geochemists. This paper studies geochemical quantitative prediction for Pb–Zn metallic mineral deposits by identifying inconspicuous surface geochemical anomalies mainly associated with the Permian and Jurassic strata in the middle-southern Da Hinggan Mountains metallogenic belt. Some new methods are employed to highlight weak surface geochemical anomalies. The weak surface geochemical anomalies of Pb and Zn are effectively highlighted by the average contrast values of Pb–Zn–Ag–Cd. The similarity coefficient with the large typical discovered deposits is used to identify new Pb–Zn mineralized anomalies and delineate new prospecting target areas. The denudation degree of mineral deposit is determined by the ratio of (W × Sn)/(As × Sb). The analogy method and areal productivity method are employed for resource prediction. Thirty-six prediction areas with Pb–Zn resources of 307.73 million tons are delineated. Five prediction areas are verified, and some new mineral deposits are proven by drilling. The verification results show that the predicted resources are very reasonable and credible. This paper is a successful case of quantitative prediction assessment of mineral resource potential, which can be used as a reference for future prospecting activities.

To classify an image, traditional classifiers depend mainly on the spectral and/or textural distinctions between different land-cover units, while this study attempts to explore the properties of statistical distinction. Using the historical classification results, we present a novel algorithm for imagery classification that achieves high accuracy, automation and efficiency. Based on object-oriented image analysis, it exploits the advantages of d_ch (the Chaudhuri’s metric) using a multi-step approach, and the objective is not to reclassify an image, but to refine or update the existing land-use/-cover classification results by comparing the pairwise d_ch value (namely similarity) between different image segments. Finally, the similar/homogeneous segments will be confirmed as their original class labels, while the inhomogeneous/dissimilar segments will be masked out with an appropriate threshold on the similarity image and be relabeled. We have systematically evaluated the algorithm by running it on the basis of the existing GIS base maps, which indicated the good performance of it.

Geochemical background is the basis of anomaly evaluation in mineral exploration and environmental investigation. However, the background value obtained from secondary media is inevitably affected by weathering, transportation, and sorting, which leads to secondary depletion or enrichment of chemical elements. This problem can be avoided by the geochemical mapping of the exposed crust. In this paper, more than 38,000 samples of rocks data were collected, and an original method was presented for the first time to produce the cobalt geochemical map of exposed crust across the whole of China. Using a geological map grid of 1:200,000 as the basic calculation unit, the area and content of rock types in each unit were calculated, and then the grid was assigned using the area-weighted average method. Based on this, an geochemical contour map was drawn in ArcGIS. The results show that the median of the exposed crust is 9.74 mg/kg, which is lower than that of the whole crust and soils. This value is explained by the vertical heterogeneity of the crust and the secondary enrichment, respectively. Co anomalies and anomalous centers of exposed crust are distributed in southwest, north, and northwest China, where they are primarily related to Permian Emeishan Large Igneous Province (ELIP), Pacific plate, and the big mantle wedge (BMW), Archean metamorphic basic rocks, and ophiolite belts.

Particle size exerts significant control on the concentration of elements in stream sediments and is therefore critical in stream sediment-based geochemical exploration, which has proved important in China’s National Geochemical Mapping Project. There are various geographical landscapes in China with different distribution characteristics of stream sediments. Therefore, we studied the relationship between particle size and element distribution in stream sediments, which is always a crucial but challenging issue in geochemical surveys. The distributions of minerals and elements in eight size fractions of stream sediments (2–0.84, 0.84–0.42, 0.42–0.25, 0.25–0.177, 0.177–0.125, 0.125–0.096, 0.096–0.074, and <0.074 mm) from the Dongyuan W-Mo deposit in eastern China were studied. The results show that the 2–0.25 mm particle size fraction of stream sediments is composed mainly of rock debris and various minerals from broken bedrock upstream, while the <0.25 mm fraction is composed mainly of clay, individual minerals, and organic matter. The pilot survey results prove that using 2–0.25 mm as the sampling particle size fraction is better than using <0.25 mm, especially in geochemical prospecting and geological body delineation. Sampling the 2–0.25 mm particle size fraction of stream sediments can help to delineate proven ore bodies, ore-related anomalies, and geological bodies more effectively and more credibly. The suggested sampling particle size fraction for a stream sediment geochemical survey in a humid to semi-humid low mountain landscape in eastern China is therefore 2–0.25 mm, rather than the particle size fraction of <0.25 mm that was used for sampling in this area before. This paper depicts a successful example for determining the optimal sampling particle size fraction for stream sediment-based geochemical exploration.