[Show abstract][Hide abstract] ABSTRACT: This study investigated the distribution and sources of Cd in soils from a Cd-rich area in the Three Gorges region, China. The results showed that in the study area arable soils contain 0.42–42 mg kg−1 Cd with 0.12–8.5 mg kg−1 in the natural soils, corresponding to high amounts of Cd (0.22–42 mg kg−1) in outcropping sedimentary rocks in the area. Both lognormal distribution and enrichment factor (EF) plots were applied in an attempt to distinguish between geogenic and anthropogenic origins of Cd in the local soils. The lognormal distribution plots illustrated that geogenic sources dominated in soils with low and moderate Cd concentrations (<8.5 mg kg−1), whereas anthropogenic sources (agricultural activities, coal mining) significantly elevated Cd contents in some arable soils (>8.5 mg kg−1). The enrichment factor plots illustrated that the majority of the soil samples had EF values of <5, pointing to a geogenic origin of Cd in the soils, whereas some arable soils had EF values >5, pointing to an additional anthropogenic input of Cd to the soils. Sequential extraction results showed that Cd soluble in water and weak acid (water-soluble, exchangeable and carbonate fraction of the soil) accounts for an average of 31% of the total soil Cd, which indicates high potential for Cd mobility and bioavailability. The findings point to a potential health risk from Cd in areas with high geogenic background concentrations of this metal.
[Show abstract][Hide abstract] ABSTRACT: Environmental contamination with cadmium (Cd) and fluorine (F) and the associated health impacts on humans have raised significant concerns in the literature, but the additional health risks created by Cd have not been investigated in areas with endemic fluorine intoxication (fluorosis). Here, we report for the first time that naturally occurring Cd in areas where endemic fluorosis is related to coal combustion is a serious hidden toxin. The high Cd levels in rocks and soils of these areas may increase health risks to epidemiological level, irrespective of fluorine levels. We implemented a pilot study in a fluorosis-affected rural area within China's Three Gorges region, and revealed enrichment of Cd in local bedrock (4.48-187 mgkg(-1)), coal (11.5-53.4 mgkg(-1)), and arable soils (1.01-59.7 mgkg(-1)). Cadmium was also observed to concentrate in local food crops (0.58-14.9 mgkg(-1)) and in the urine of local residents (1.7-13.4 microgL(-1)). A routine epidemiological investigation revealed that the two major Cd exposure pathways were through crop consumption and inhalation of emissions from coal combustion. Therefore, the naturally occurring Cd in areas with endemic fluorosis related to coal combustion represents a previously unrecognized toxin that must be addressed as part of efforts to control the endemic problem. The biogeochemical processes of Cd and the associated environmental effects will require additional in-depth study.