Spatial and Temporal Variability of Soil Organic Matters in Se-rich Areas of Hainan Island in Recent 30 Years

[Objectives] The aim was to reveal the distribution of soil organic matter content in cultivated land in the Se-rich areas of Hainan in 1980and 2010, so as to provide reference for the study on the evolution of soil organic matter content.[Methods] With the combination of field investigation with indoor analysis, the characteristics of organic matter content in the Se-rich areas of Hainan in 1980 and 2010 was revealed by means of spatial analysis, and the differences were analyzed.[Results] In the last 30 years, the proportion of 20-30 g/kg of soil organic matter content in the Se-rich areas of Hainan was reduced, but the content of soil organic matter in the area generally increased. The average value of the content of organic matter in the area was increased from 25.3 g/kg in the 1980s to 28.1 g/kg, but its spatial distribution was uneven.[Conclusions] The farmers should be guided to change the fertilization structure, and attention should be paid to the application of organic fertilizer, so as to improve the soil organic matter content.

Application and Development Prospect of Se-rich & High-Ca Organic Fertilizer

Se is one of trace elements necessary for the human body,and human body could absorb Se via the food. Se intake is insufficient in 2/3 region of China,which seriously affects health of local residents. Therefore,the research of Se-rich fertilizer and the development of Se-rich product become the research focus in food science,medicine and other fields. There are rich marine resources in Beibu Gulf waters of Guangxi,and much carapace organic waste is generated. These carapace waste not only has high Se content but also is composed of a lot of Ca. The preparation of Se-rich ＆ high-Ca fertilizer by these carapace waste not only reaches the target of recycling and environment friendly but also increases the yield of agricultural products,reduces diseases and pests,improves quality,increases the added value of agricultural product,which brings better economic benefit and meets people＇s demand for healthy food.

Geochemical characteristics of soil selenium and evaluation of Serich land resources in the central area of Guiyang City,China

Based on the results of multipurpose regional geochemical surveys of the Guizhou Province, geochemical characteristics of soil Se and Se-rich land resources in the central area of Guiyang City were studied and evaluated.Major conclusions are as follows:(1) the Se content in surface soil of the central area of Guiyang City was 0.17–2.89 mg kg^(-1), and the average was 0.78 mg kg^(-1), which were respectively 2.6 and 3.9 times of the national background value of soil and the world background value of soil.The Se content in deep soil was 0.11–1.48 mg kg^(-1), and the average was 0.44 mg kg^(-1), which were respectively 1.5 and2.2 times of the national background value of soil and the world background value of soil. The soil Se content decreased with the increase in the soil depth on the vertical profile, and the surface soil had a higher Se content.(2)Distribution of Se content was mainly affected by parent material, physicochemical properties of soil and other components, soil type, and land use type. Parent material played a key role, as the soil Se content was mainly originated from parent rock and increased with the background value of Se in parent rock, physicochemical properties of soil and other components had certain influences upon the Se content. Se was shown to have a significant linear positive correlation with S and organic carbon but no significant correlation with p H value. Se content varied with different types of soil as follows: skeleton soil > yellow soil > paddy soil > limestone soil > purple soil. Land use type also hadcertain influences upon the soil Se content as follows: dry land > construction land > garden plot > grassland =garden plot > forest land.(3) Taking 0.4 mg kg^(-1)B x(Se) <3.0 mg kg^(-1) as the standard for Se-rich soil, Se-rich soil of the study area covered an area of 2224 km^2 and 92.5% of the total area; the remaining is general soil. The study area had no Se-excess soil. Therefore, the central area of Guiyang City has a high proportion of Se-rich land, a large area of Serich land resources, and a moderate selenium enrichment strength, which have been rarely seen anywhere and provide advantageous resources for the development of Se-rich featured agriculture.

Effects and mechanism of igneous rock on selenium in the tropical soil-rice system in Hainan Province, South China

To illuminate the migration and transformation of selenium(Se)in the igneous rock-soil-rice system,285 pairs of rhizosphere soil and rice samples were collected from the granitoid and basalt areas in Hainan Province,South China.The contents of Se in soils derived from granitoid and basalt are,respectively,0.19±0.12 mg/kg and 0.34±0.39 mg/kg,which are much higher than Se contents in granitoid and basalt.Selenium shows remarkable enrichment from granitoid and basalt to soils.The mobile fraction of Se in soils derived from granitoid is 0.0100±0.0034 mg/kg,which is significantly higher than that of basalt(0.0058±0.0039 mg/kg).Although soil derived from basalt shows higher Se contents,Se contents in rice samples,mobile fractions of Se in soils,and biological concentration factor(BCF)is similar or even lower than that from granitoid.Basalt consist of calcic plagioclase and pyroxene,and are much richer in Fe,Al,and Ca than granitoid.Correspondingly,the basalt-derived soils have higher goethite,hematite,kaolinite,cation exchange capacity(CEC)content,and higher p H than the granitoid-derived soils,which result in higher adsorption capacity for Se and relatively lower Se bioavailability.Soils derived from granitoid and basalt in tropical regions are beneficial to produce Se-rich rice.

Lithological and Si–O–S isotope geochemistry:constraints on the origin and genetic environment of the selenium(Se)-rich siliceous rocks in Enshi,Hubei Province,China

Se-rich black rock series of the Middle and Late Permian system is widely distributed in Enshi Prefecture with an exposed area of 850 km~2,among which the unique Yutangba black rock series independent selenium deposit with industrial mining significance in the world is produced.However,the source and metallogenic mechanisms of Se are still controversial.In general,terrestrial weathering and submarine hydrothermal processes are the main source end members of Si and Se,and the related siliceous rocks record the deposition process of Si and Se from different sources.The study of lithofacies and paleogeography shows that western Hubei belongs to the near eastwest turn of the Yangzi platform in the Middle and Late Permian and becomes an inter-platform basin with nearly north-south direction.Therefore,the comparative study of the Yutangba deposit and the selenium-rich black rock series in the northern Shadi with high selenium content is expected to reveal the provenance evolution of the two sections in space,and further restrict the Se mineralization mechanism in the Enshi basin.From the element geochemistry study,the black rock series in two study areas may have formed in a transitional position of either the continental margin or continental slope,in the process of sedimentary,more terrigenous clastic materials entered.They are rich in lithophile elements V and Cr.δU>1.0,U/Th and V/(V+Ni)ratio indicate that the Se-rich strata of black rock series in the Enshi areas occurred in an anoxic reducing environment and formed in an environment between the ocean basin and the continental margin.From Si-O isotope geochemistry,the original Si source of the study area is thought to relate to a volcanic eruption,which leads to the enrichment of Si in the seawater.The determined values of S isotope in the black rock series of the two study areas both show the characteristics related to organic reduction/biogenic.