[Effect of Land Use/Land Cover Change on the Concentration of Se and Heavy Metals in Soils from a "Return Cropland to Forest" Area, Southwest China].

Human activities (land use) and environmental change (land cover change) affect the concentration of Se and heavy metals in soils. The implementation of the "Return Cropland to Forest (RCF)" ecological project has changed the land use and cover, which has provided an ideal experimental area for studying the effects of land use and cover change on selenium (Se) and heavy metals in the soil. In this study, 91 top soil samples from different land use and land cover types, including dry land, paddy land, natural forest land, and secondary forest land, were collected, and the contents of Se, heavy metals, and soil organic matter (SOM) and pH were analyzed. The results showed that:① the average values of ω(Se) (0.42×10-6), ω(As) (13.0×10-6), and ω(Sb) (1.03×10-6) were higher than the soil background values of western Chongqing. ② The concentrations of Se, Cd, Cr, Ni, Pb, and Zn in soils from secondary forest land were significantly higher than those from dry land soils, suggesting that the Se and heavy metals might have significantly increased in the surface soil after the implementation of the RCF ecological project. ③ The SOM was the key controlling factor for the enrichment and distribution of Se and heavy metals in the top soils. Our results indicated that the land use and land cover change would deeply impact the concentrations of Se and heavy metals in the top soils via influencing the soil properties, especially the SOM.

Regional distribution of longevity population and chemical characteristics of natural water in Xinjiang, China.

Xinjiang Province, China is recognized for the longevity of its inhabitants. To study the temporal and spatial variation of longevity region and chemical characteristics of natural water of longevity region in Xinjiang, three population censuses on county-level and 51 natural water samples from Hotan Prefecture, Xinjiang were collected and analyzed. 103 natural water samples were collected from the public papers. Population statistics on county-level showed that the number of centenarians per 100,000 inhabitants (OC) in Southern Xinjiang was 7.4(year 1990), 4.9(year 2000) and 2.1 times (year 2010) more than that of Northern Xinjiang, respectively. And distribution of the longevity index (LI%), centenarity index (CI%) and number of centenarians per 10,000 over 65 year-old subjects (UC) on county-level decreased from south to north. Natural water in Northern Xinjiang was mainly fresh soft water, and it was mainly fresh hard water and brackish hard water in Southern Xinjiang. Water quality of natural water in Northern Xinjiang was superior compare to that of Southern Xinjiang, while number of centenarians 65 year-old & over per 10,000 subjects in Northern Xinjiang were less than that of Southern Xinjiang before 2010. The research indicates that keeping on drinking water with high total hardness (TH) and Mg/Ca ratio might be good for the health.