Differences of selenium and other trace elements abundances between the Kaschin-Beck disease area and nearby non-Kaschin-Beck disease area, Shaanxi Province, China.

In order to find out the environmental geochemical characteristics of KBD affected area, KBD and non-KBD villages in KBD Counties, Weibei KBD area, Shaanxi Province, China were studied. Contents of Se and other elements in soil, wheat, maize and drinking water were analyzed. The results show that soil of Weibei KBD area is deficient in trace elements comparing with BSC and non-KBD area. Wheat of Weibei KBD area is deficient both in major elements and trace elements comparing with REC. Wheat of KBD village is especially deficient in Cr, Co, Se, Mo and Mg. Contents of Sr, Li and Mo in wheat of KBD village are significantly lower than nearby non-KBD village, but the average Se content is slightly higher. The deficiency of trace elements, especially Se, Sr, Li and Mo in staple food and trace elements in soil, is the main characteristic for the environment of KBD area.

Distribution characteristics and main influencing factors of selenium in surface soil of natural selenium-rich area: a case study in Langao County, China.

In order to study the distribution of selenium in surface soil and its main influencing factor, we collected 360 surface soil samples and four groups of soil profiles with 210 corresponding parent rock samples in Langao County, Shaanxi Province (a typical high-selenium area of Daba Mountain). Samples were analyzed for trace elements by using ICP-MS, ICP-OES and HG-AFS. The results show the following. (1) selenium content in surface soils of Langao County varies greatly (0.03-16.96 mg/kg). The mean selenium content in surface soils of Langao County is 0.99 mg/kg, higher than the global (0.4 mg/kg) and China (0.29 mg/kg) soil average, and 3.4 times the mean of soil selenium in China. (2) Selenium content of bedrock in Langao County also varies greatly (0.01-56.22 mg/kg), with an average selenium content of 2.02 mg/kg, which is 40 times higher than the upper crust (0.05 mg/kg). (3) Selenium content in the strata of the Late Precambrian-Early Paleozoic and its variation is an important factor affecting the spatial variation of soil selenium content. The black rock series (carbonaceous slate and silicon-bearing carbonaceous slate) of the Upper Ediacaran-Cambrian on the north side has the highest mean selenium content (> 7.92 mg/kg), and the selenium content of the surface soil in the distribution area can reach up to 16.96 mg/kg. The Middle Cambrian, Upper Cambrian, Ordovician and Silurian (limestone and marl) in the south has the lowest mean selenium content (< 2 mg/kg), and the selenium content of surface soil in the distribution area is lower than 0.8 mg/kg mostly. (4) Soil samples at different depths in the same soil profile have similar composition of rare earth elements (REE), and bedrock and corresponding topsoil has similar composition of REE. This study indicates the selenium content in the topsoil varies greatly, even in high-selenium area. And the difference of selenium distribution is closely related to the original selenium content of the bedrock.

Geochemical valuation and intake of F, As, and Se in coal wastes contaminated areas and their potential impacts on local inhabitants, Shaanxi China.

This study probe the human health risk of fluoride (F), arsenic (As), and selenium (Se) and their daily intake available quantity to human through different sources in different regions of Shaanxi, China. For this purpose, a number of samples, including coal and coal wastes, rocks, soil, and vegetables were collected from south Qinling Mountain stone-like coal (Geo type-I), Binxian-Jurassic (Geo type-II), Hancheng Permo-Carboniferous (Geo type-III), and countryside (Huanglong County) of Shaanxi province. All these samples were analyzed through atomic fluorescence spectroscopy and combustion hydrolysis methods. Results showed that Geo type-I was enriched with As, Se, and F, Geo type-II, III, and the countryside were slightly enriched with As and F and deficient in Se. The average daily intake (ADI) of Se in Geo type-I was 0.005-0.0045, Geo type-II 0.0005-0.0004, Geo type-III 0.0006-0.0005, and countryside 0.0002-0.001 in mg kg-1 day-1 adult-children, respectively, which was lower than the optimum level (0.06-0.075 mg kg-1day-1). ADI of As at Geo type-I was 0.0085-0.0075, Geo type-II 0.004-0.0037, Geo type-III 0.0008, and countryside 0.00022-0.00019 in mg kg-1 day-1 adult-children, respectively, which was above the acceptable range (10-6-10-4). ADI of F at Geo type-I was 0.0047-0.0041, Geo type-II 0.0098-0.0087, Geo type-III 0.002-0.0017 and countryside 0.0015-0.0013 in mg kg-1 day-1 adult-children, respectively. The toxicity level of Se and F at all the regions was lower than the NOAEL and LOAEL, while As was higher at Geo type-II and I. The extreme deficient of Se than the optimum range along with high F could deregulate the normal body growth especially causes bones and joint problems. However, the study found a rare patient with bone and joint disease (maybe Kashin-Beck disease) in the countryside. To find the exact cause of Kashin-Beck disease, the study needs further medical investigation in Se-deficient regions and their association with selenium deficiency and enriched fluoride.

Selenium and hazardous elements distribution in plant-soil-water system and human health risk assessment of Lower Cambrian, Southern Shaanxi, China.

The natural selenium poisoning due to toxic Se levels in food chain had been observed in humans and animals in Lower Cambrian outcrop areas in Southern Shaanxi, China. To find out the distribution pattern of selenium and other hazardous elements in the plant, soil and water of Lower Cambrian in Southern Shaanxi, China, and their possible potential health risk, a total of 30 elements were analyzed and the health risk assessment of 18 elements was calculated. Results showed that the soil, plant and natural water of Lower Cambrian all had relatively high Se levels. In Lower Cambrian, the soil was enriched with Se, As, Ba, Cu, Mo, Ni, Zn, Ga, Cd and Cr (1.68 < Igeo < 4.48, Igeo; geo-accumulation index). In same plants, the contents of Se, Cd and Zn (except Cd in corn and rice, Zn in potato and corn) of Lower Cambrian were higher than that of the other strata. Ba and Ga in natural water were higher than that of the other strata, while K and Cs were opposite. The health risk assessment results showed that the people living in outcrop areas of Lower Cambrian had both high total non-carcinogenic risk of 18 elements (HI = 16.12, acceptable range: < 1) and carcinogenic risk of As (3.98E-04, acceptable range: 10-6-10-4). High contents of Se, As, Mo and Tl of Lower Cambrian may pose a health risk to local people, and food intake was the major pathway. For minimizing potential health risk, the local inhabitants should use the mix-imported food with local growing foods.

Regional Distribution of Longevity Population and Elements in Drinking Water in Jiangjin District, Chongqing City, China.

In order to determine the spatial variation of longevity population and elements contained in the drinking water of longevity region in Jiangjin and investigate the relationship between the elements in drinking water and longevity, population censuses on township level and 98 drinking water samples from Jiangjin District, Chongqing City in West China were collected and analyzed. Population statistics on township level showed that the number of centenarians per 100,000 inhabitants (OC), centenarity index (CI), and number of centenarians per 10,000 over 65-year-old subjects (UC) present obvious geographic distribution properties, generally Central region > Northern region > Southern region (Kruskal-Wallis test, p < 0.05). Moderate hard water (150 mg/L < total hardness (TH) = 156.17 mg/L < 300 mg/L) was mainly found in drinking water from longevity township (OC > 7.5) in Jiangjin District, whereas soft water (75 mg/L < TH = 111.23 mg/L < 150 mg/L) was mostly in non-longevity township (OC < 7.5). The mean concentration of strontium (Sr) (0.73 mg/L) in drinking water from the longevity township was apparently higher than that of non-longevity township (0.44 mg/L) (Mann-Whitney U test, p = 0.019 < 0.05). The concentrations of Ba, Li, Mn, Ni, and Se in drinking water from longevity township were also higher than those of non-longevity township (Mann-Whitney U test, p < 0.05). The research indicates that exercising strict control over the concentrations of TH, Sr, Ba, Li, Mn, Ni, and Se in drinking water might be good for the health and prolong people's life.

Hydrochemical characteristics of natural water and selenium-rich water resources in the Northern Daba Mountains, China.

The Northern Daba Mountains (NDM) of Shaanxi Province, China, are a well-known selenium (Se)-rich area, and the area is also known for endemic fluorine (F) and arsenic (As) poisoning. In order to study the hydrochemical characteristics and trace element contents of the natural waters of this region, 62 water samples were collected from Lan'gao area in the NDM. The hydrochemical composition was principally characterized by Ca·Mg-HCO3·SO4. F and As concentrations ranged from 0.01 to 0.67 mg/L and from 0.33 to 6.29 µg/L, respectively, lower than Chinese national standard and international guidelines for drinking water quality. One year of monitoring proved that F and As in natural water were not the sources of the local fluorosis and arseniasis in the NDM. The average Se concentration in fissure water was 5.20 µg/L. The average Se content of river water was 2.82 µg/L, 14 times that of the world's surface level (0.2 µg/L). The Se content in eight samples reached the Chinese national standards for mineral drinking water quality (>10 µg/L). Contrasting the water samples of May, July, and September in 2015 shows that the Se content is relatively stable and the increase of humidity might be beneficial to increase the content of selenium and strontium in water.

Distribution and geological sources of selenium in environmental materials in Taoyuan County, Hunan Province, China.

The selenium (Se) distribution and geological sources in Taoyuan County, China, were determined by using hydride generation atomic fluorescence spectrometry on rock, soil, and food crop samples collected from various geological regions within the county. The results show Se contents of 0.02-223.85, 0.18-7.05, and 0.006-5.374 mg/kg in the rock, soil, and food crops in Taoyuan County, respectively. The region showing the highest Se content is western Taoyuan County amid the Lower Cambrian and Ediacaran black rock series outcrop, which has banding distributed west to east. A relatively high-Se environment is found in the central and southern areas of Taoyuan County, where Quaternary Limnetic sedimentary facies and Neoproterozoic metamorphic volcanic rocks outcrop, respectively. A relatively low-Se environment includes the central and northern areas of Taoyuan County, where Middle and Upper Cambrian and Ordovician carbonate rocks and Cretaceous sandstones and conglomerates outcrop. These results indicate that Se distribution in Taoyuan County varies markedly and is controlled by the Se content of the bedrock. The Se-enriched Lower Cambrian and Ediacaran black rock series is the primary source of the seleniferous environment observed in Taoyuan County. Potential seleniferous environments are likely to be found near outcrops of the Lower Cambrian and Ediacaran black rock series in southern China.

Environmental behaviors of selenium in soil of typical selenosis area, China.

Daba Mountain area is one of the two endemic selenosis areas in China, which may relate with the environmental behaviors of selenium (Se) in soil. This study focuses on the concentraion and distribution of Se and its relationships with some other elements in natural soil in the area. The average concentration of Se in Daba Mountain soils was 14.3 times higher than the value cited for natural soil background worldwide, suggesting that soils in the region were contaminated by the element. The finding was confirmed by Miller geoaccumulation index assessment with 22% slightly polluted, 15% moderately polluted, 11% highly to very highly polluted and 8% moderately polluted to highly polluted. Soil Se is generally enriched in topsoil, and its distribution is extremely uneven and significantly site-specific. However, the concentrations of Se in soils have significant positive correlation with them in corresponding parent materials (r = 0.995, P < 0.01). Besides of Se, the concentrations of elements, such as Ca, Sr, V, Cu, Zn, Ni, Mg, Co, and Fe are also obviously abnormal compared with their background values of Chinese soil. Selenium behaviors in the region were controlled by multifactors: in addition to the parent material, pedogenic processes, biologic processes, and element geochemical behaviors also impacted the concentration and distribution of selenium in soil.