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Guo R.,Water Resources University | Jin X.,Water Resources University | Wang X.,Hainan Institute of Geological Survey | Hu G.,CAS Institute of Remote Sensing
Earth Science Frontiers

In an arid inland basin, evapotranspiration (ET) is the major loss related to the water balance and precise estimation of ET is essential for evaluation of available water resources in these areas. The study of actual evapotranspiration on a regional scale has great significance for environmental protection. Based on SEBS algorithm (Surface Energy Balance System), the ET was estimated using DEM data, MODIS data and GLDAS data over the Qaidam Basin from 2001 to 2011 at a spatial resolution of 500 m. What's more, the long-term change and spatial distribution of ET and its relationship with pan observed evaporation in the Qaidam Basin were studied. The result indicated that the annual actual ET of Qaidam Basin increased with time and the value varied from 72.73 mm in 2001 to 182.34 mm in 2011, and the maximum of the mean daily ET varied between 2.62 mm and 3.20 mm during the year 2001 to 2011. The evaporation coefficient is 0.14 in the Qaidam Basin. The analysis of NDVI and its corresponding ET presented that the NDVI threshold between bare soil and vegetation is 0.055 in the Qaidam Basin. The water bodies had highest mean daily ET (2.31 mm/d) though they only make up 1.92% of the study area. The mean daily ET of bare soil, sparse shrub, dense shrub, grassland, farmland and forest in the Qaidam Basin from June to September in the year 2010 were 0.24 mm/d, 0.42 mm/d, 1.21 mm/d, 1.12 mm/d and 1.18 mm/d, respectively. Source

Xi X.,China Geological Survey | Li M.,China Geological Survey | Zhang X.,Hebei Institute of Geological Survey | Zhang Y.,Henan Institute of Geological Survey | And 4 more authors.
Earth Science Frontiers

Soil organic carbon in middle-east China can be studied by comparison based on the data obtained by multi-purpose regional geochemical survey. The middle-east plain covers the terrain of Hebei, Henan, Hubei, Hunan, Guangdong and Hainan provinces, ranging from relatively higher latitude to low latitude and crossing temperate zone, subtropical zone and tropical zone. More than 334000 km2 were covered in the multi-purpose regional geochemical survey. Top soil (0-0.2 m) carbon storage is 906.84 Mt and average carbon density is 2716.93 t/km2. Including the higher soil carbon density in the northeastern plain, the carbon density in middle-east regions of China exhibited the changing pattern of high low high low from the northeastern plain downward to Hainan Province, that is 3327.8 t/km2 (northeastern plain)→2207.39, 2421.02 t/km2 (Hebei and Henan)→3442.15, 3942.92 t/km2 (Hubei and Hunan)→2255.90, 2936.72 t/km2(Guangdong and Hainan). The soil carbon density in agricultural ecosystem and urban ecosystem presented different changing rule from higher latitude to lower latitude, i.e., in agricultural farmland it changes from low to high, and in urban soil from high to low. The soil organic carbon increased by 14.5% (totally increasing 115.18 Mt and annually averaging 5.76 Mt/a) during past 20 years compared to the value achieved by the second soil reconnaissance. However organic carbon did not increase evenly. The rising rate decreased from low latitude to high latitude, and organic carbon increased in agricultural and urban ecosystem but decreased in tideland, rivers, lakes, grassland, forest and swamp. Source

He Y.-S.,Hainan Institute of Geological Survey
Chinese Journal of Ecology

The concentration, distribution, and speciation of heavy metals in urban soils of Haikou City were investigated. The mean concentrations of heavy metals Hg, As, Cd, Cu, Cr, Ni, Pb and Zn were 0. 073, 3. 82, 0. 25, 26. 7, 92. 4, 52. 5, 29. 1 and 84. 1 mg·kg-1, respectively. In comparison with the background values, the enrichments of Hg, As, Cd, Cu, Cr, Ni, Pb and Zn in the soils of Haikou City were obvious, indicating a certain degree of heavy metal pollution. Cr, Ni, Cu, Cd and Zn were enriched in suburban areas, while Pb was enriched in roadside green belts and Hg was enriched in residential areas. Zn, As, Cr, Cu and Ni in the soils of Haikou were predominantly in residual fraction. Hg was mainly associated with strong organic-bound and residual fractions, while Pb was mainly presented as iron and/ or manganese oxide-bound fractions. On the contrary, Cd existed mainly in bio-available fractions. The results of multiple-metals ecological risk assessment indicate that the heavy metal pollution in the soils of Haikou is at a relatively low level. However, Cd and Hg pollution deserves much more attention. Source

Liao X.,Geological Bureau of Hainan Province | Fu Y.,Hainan Institute of Geological Survey | He Y.,Hainan Institute of Geological Survey | Yang Y.,Hainan Institute of Geological Survey

Arsenic is a highly toxic element and its presence in foodstuffs will do harm to human health. In this study, the levels of arsenic in the fruits of three mango cultivars (Mangifera indica L.) from Hainan Island, China were investigated and their relationships to soil properties were discussed. The concentrations of arsenic in the mango fruits ranged from 0.6 to 50μgkg-1 (FW) with a mean value of 8.6μgkg-1. The transfer factors (TFs) of arsenic from soil to fruit varied between 0.0001 and 0.055 with a mean value of 0.0059. Both arsenic concentrations in the mango fruits and TFs were negatively correlated with soil Al2O3, Fe2O3, and MnO concentrations that could be described by a power model (y=axb), suggesting that soil Al-Fe-Mn oxides may play an important role in limiting the bioavailability and bioaccumulation of arsenic in the mango fruits. In addition, arsenic accumulations in the mango fruits were influenced by the soil pH. Mango fruits from the soils with pH between 4.8 and 5.5 had relatively high arsenic concentrations and TF values. © 2013 Elsevier B.V. Source

Fu Y.,Wuhan University | Fu Y.,Hainan Institute of Geological Survey | Chen M.,Wuhan University | Chen M.,Hainan Institute of Geological Survey | And 8 more authors.
Environmental Pollution

The acquaintance of arsenic concentrations in rice grain is vital in risk assessment. In this study, we determined the concentration of arsenic in 282 brown rice grains sampled from Hainan Island, China, and discussed its possible relationships to the considered soil properties. Arsenic concentrations in the rice grain from Hainan Island varied from 5 to 309 μg/kg, with a mean (92 μg/kg) lower than most published data from other countries/regions and the maximum contaminant level (MCL) for Asi in rice. The result of correlation analysis between grain and soil properties showed that grain As concentrations correlated significantly to soil arsenic speciation, organic matter and soil P contents and could be best predicted by humic acid bound and Fe-Mn oxides bound As fractions. Grain arsenic rises steeply at soil As concentrations lower than 3.6 mg/kg and gently at higher concentrations. © 2011 Elsevier Ltd. All rights reserved. Source

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