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Selenium (Se), a trace element in the soil, is mainly ingested by the human body from the soil-plant system through food chain. Meanwhile, Se in the soil is subjected to geological, geographical environmental factors and soil properties. Therefore, it is essential to study contents and distributions of Se in the soil for developing Se-enriched agricultural products and protecting human health. Jieyang City is one of distinctive agriculture areas of Guangdong Province, China, and the status of soil Se has an important impact on the development of local distinctive agriculture. Based on the above reasons, a total of 1 330 topsoil samples (0-20 cm) and 331 deep soil samples (150-200 cm) were collected systematically from Jieyang City to discuss the distribution, enrichment characteristics and influencing factors (including parent materials, soil types, land using types, soil physicochemical properties and elevation) of soil Se. Results showed that contents of Se in topsoil ranged from 0.02 to 2.01 mg/kg with a geometric mean value of 0.48 mg/kg that was 1.66 times larger than the average Se contents of soil in China. The topsoils of Jieyang City were in the category of Se sufficiency and Se abundance on the whole. According to the spatial distribution derived by the Kriging interpolation, soils of Se abundance were mainly distributed in Puning, Huilai and northern edge of Jieyang City. The Se enrichment area in the topsoil reached 52.03% of Jieyang City, but the spatial distribution was scattered, which may be related to factors such as parent materials and soil types. Strong Se enrichment soils were mainly distributed in the areas of granite and siltstone, while most of the soil which came from quaternary alluvial deposits was not enriched. Analysis of variance showed that different parent materials, soil types and land use patterns had different effects on soil Se contents and enrichment. The main factor affecting Se contents in surface soil of Jieyang City was soil parent materials. The soils which derived from mudstone and tuff were more likely to enrich Se. Among different land use types, farmland had great influences on soil Se content due to long-term agricultural activities. Among different soil types, yellow soil and latosolic red soil were easy to enrich Se due to their high contents of organic matter. Although soil Se content differed among different land use types, it was not obvious that soil Se was affected by human activities in Jieyang City. In addition, the physicochemical properties of soil and altitude were also important factors of leading to Se enrichment in the topsoil of Jieyang City. Regression analysis showed that there was a significantly negative correlation between Se and pH (P<0.01), and Se was significantly positively correlated with TOC (P<0.01), Fe2O3 (P<0.01) and Al2O3 (P<0.01) in the topsoil. Spearman correlation analysis showed that the Se content in the topsoil of Jieyang City had a significantly positive correlation with elevation (P<0.01). The higher elevation, the soil Se was more easily enriched. Thus, in the development process of distinctive agriculture in Jieyang City, it is recommended to rationally use Se-enriched soils, plant Se-enriched crops, and promote the development of local distinctive agriculture in accordance with the principle of adapting to local conditions. [ABSTRACT FROM AUTHOR]

The re-exploration about the law of trace elements migration during pyrolysis of coal samples, which were collected from Yima mining and Yanzhou, mining districts, were done by authors for studying pervasive law of trace element activity in this processes. It was discovered that in general, change trend on evaporation rate and enrichment rate of trace elements in coal, during the pyrolysis of coal,are comply with periodic law of elements. For this reason, difficult volatile elements in coal from Yima mining were divided into three categories within 1000 °C. V, Cr, Co, Cu, Ga, Zr, La, Pr, Nd, Tm are most difficult elements in volatile which belongs to the first sort one; Second sort of elements, there are 7 elements from Sm to Ho in REE and Ta, are more difficult ones; the third sorts of elements are relatively difficult ones in which there are Li, Ge, Nb, Mo, Er. In pyrolysis of coal, transformation of the lanthanide obeys geo-chemical effect of rare earth elements (REE). [ABSTRACT FROM AUTHOR]