With the substantial increase in karst groundwater pollution, the pollution caused by heavy metal migration has become one of the hottest topics. The migration characteristics of heavy metals in karst groundwater are closely related to the geological environment in which they are found. Therefore, this review focuses on the migration characteristics of heavy metals in karst groundwater in southern and northern China and highlights the effect of different environmental contexts such as atmosphere (precipitation), vegetation, soil, rock, and aquifers on the behavior of heavy metals. It also summarizes existing research methods on heavy metal migration in karst groundwater. Meanwhile, current advances and the future perspectives on karst groundwater heavy metal migration will be presented. It is hoped that this review may shed light on the study of heavy metal migration in karst areas.

In this study, 24 surface water samples were collected from the main trunk/tributary of the Lijiang River during the wet season (April) and the dry season (December) in 2021. The total concentration of 11 heavy metal(loid)s (Al, Cu, Pb, Zn, Cr, Ni, Co, Cd, Mn, As, and Hg) was determined to investigate their physicochemical properties and spatial-temporal distribution characteristics. The heavy metal evaluation index (HEI) and the positive matrix factorization (PMF) model were employed to evaluate water quality and to reveal quantitatively identified pollution sources for further investigation to obtain a health risk assessment using the hazard index (HI) and carcinogenic risk (CR) of various pollution sources. The mean concentrations of heavy metal(loid)s in surface water in the wet and dry seasons were ranked as: Al > Mn > Zn > Ni > Cd > Cr > Cu > As >Hg = Pb > Co, with the mean concentration of Hg being higher than the national Class II surface water environmental quality standard (GB3838-2002). In terms of time scale, the concentration of most heavy metal(loid)s was higher in the wet season; most heavy metal(loid)s were distributed mainly in the midstream area. HEI index indicated that the main water quality status was “slightly affected” in the study area. Five potential sources of pollution were obtained from the PMF model, including industrial activities, traffic sources, agricultural activities, domestic waste emissions, and natural resources. The source-oriented risk assessment indicated that the largest contributions of HI and CR were agricultural sources in the Lijiang River. This study provides a “target” for the precise control of pollution sources, which has a broad impact on improving the fine management of the water environment in the basin.

The hydrochemical characteristics of watersheds are influenced by many factors, with chemical weathering and human activities exerting the most substantial influence. Performing a quantitative evaluation of the factors contributing to the chemical weathering of rocks is of significant scientific importance. This research zeroes in on the Qingtang River basin to elaborate on the hydrochemical characteristic, explore the origins of ions, and quantify the influence of anthropogenic discharges amidst cation interferences, thus improving the accuracy of chemical weathering rate estimations. The samples encompassed surface water, groundwater, and water from dripping in karst caves. The findings indicate that human-induced alterations significantly influence hydrogeochemical dynamics, although chemical weathering of rocks in their natural state is the controlling factor. The mean contributions of cations from atmospheric deposition, human inputs, carbonate weathering, and silicate weathering were 17.56%, 21.05%, 51.77%, and 9.54%, respectively. The chemical weathering rate for carbonate rocks was 62.4 t·km⁻²·a⁻¹, which increased by 27.87% due to the influence of exogenous acids. The anthropogenic impact is predominantly evident in two aspects: (1) the alteration of hydrochemical processes within the watershed through direct input of ions, and (2) the acceleration of rock weathering rates in the watershed due to the exogenous acids.

Hydrochemistry and Sr isotope compositions were measured in water samples collected during high- and low-water periods from the main stream and tributaries of the Xijiang River Basin in southern China. The primary weathering end-members were analyzed and calculated using the multi-model combination and classic hydrogeochemical method. During the high-water period, structural factors were found to be the main factors controlling chemical weathering in the basin, whereas anthropogenic activity and other random factors had a negligible influence. During the low-water period, both structural and random factors controlled chemical weathering. Through path-model and semi-variance analyses, we determined and quantified the relationship between the main weathering sources, whose results were stable; this is consistent with the inversion model. The total dissolved substances were mainly derived from carbonate weathering, which was approximately 76% (0–96%) while silicate weathering accounted for only 14% (5–19%). The inversion model results showed that the optimum silicate weathering rate was 7.264–35.551 × 10³ mol/km²/year, where carbonic acid was the main factor that induces weathering. The CO₂ flux consumed by rock weathering in the basin during the study period was 150.69 × 10⁹ mol/year, while the CO₂ flux consumed by carbonic acid weathering of carbonate (CCW) and silicate rocks (CSW) was 144.47 and 29.45 × 10⁹ mol/year, respectively. The CO₂ flux produced by H₂SO₄ weathered carbonate (SCW) was 23.23 × 10⁹ mol/year.

Three high-frequency sampling and monitoring experiments were performed at the Lutang and Luowei transects of the Liujiang River entrance and at the southeast exit of the Liuzhou during 2019 for the purpose of assessing physico-chemical variables and human health hazards of water heavy metals in different rainfall processes. There were significant seasonal variations in concentrations of 11 heavy metals and most variables showed higher levels during the dry season. The distribution of heavy metals in the Liuzhou area varied significantly by region. Pollution source analysis indicated distinct seasons of wetness and dryness. The dry season is dominated by anthropogenic activities, while the wet season is dominated by natural processes. The results of hazard quotient (HQ) and carcinogenic risk (CR) analysis showed that the health risk of non-carcinogenic heavy metals in the wet season is slightly higher than that in the dry season. Seasonal changes in carcinogenic risk are the opposite; this is due to the combined influence of natural and human activities on the concentration of heavy metals in the river. Among them, Al was the most important pollutant causing non-carcinogenic, with As being a significant contributor to carcinogenic health risk. Spatially, the downstream Luowei transect has a high health risk in both the dry and rainy seasons, probably due to the fact that the Luowei transect is located within a major industrial area in the study area. There are some input points for industrial effluent discharge in the area. Therefore, high-frequency monitoring is essential to analyze and reduce the heavy metal concentrations in the Liujiang River during dry and wet seasons in order to protect the health of the residents in the area.

The land use in agricultural areas contributes to economic growth while concurrently accompanied by a series of environmental pollution issues. Xingguo County, Ganzhou City, Jiangxi Province, is a typical agricultural area with selenium-rich soil, and the rice and navel oranges grown there have high nutritional value. This study analyzed the distribution of heavy metals in the soil of this area through the kriging interpolation method, evaluated the risks of heavy metals in the soil using different pollution index methods, and quantitatively analyzed their sources using principal component analysis (PCA) and positive matrix factorization (PMF), with the aim of protecting the ecological resources of this area and providing theoretical references for avoiding heavy metal pollution of crops in the soil. The research results indicate the following: (1) Based on the background values of Ganzhou, Jiangxi Province, all heavy metals have caused pollution to the soil except for As and Hg, among which Cd poses the highest potential ecological risk in the study area. According to the values of the Environmental Quality Standards for Soil (EQSS), the concentrations of heavy metals have not exceeded the standards and have relatively low potential ecological risks. (2) In terms of health risks, all soil heavy metals basically do not bring non-carcinogenic risks but acceptable carcinogenic risks to adults and children, except for Cd. The carcinogenic and non-carcinogenic risks of soil heavy metals for children are higher than those for adults, and the main exposure route is ingestion. Among different land use types, the carcinogenic and non-carcinogenic risks of soil heavy metals in orchards are the highest. (3) Combining the kriging interpolation method and the PCA and PMF models, it can be determined that there are two main sources of heavy metals in the study area: one is natural and the other is anthropogenic. Among the anthropogenic sources, agricultural sources contribute the most to soil heavy metal pollution. Through these research results, it can be found that soil heavy metal detection should be conducted in agricultural land, and risk-based management measures should be implemented.