Studies On Geochemical Characteristics And Environmental Influence Of Main Microelements In Farmlands Of Oasis

The soil from farmland of Zhangye area was studied in this paper. The physical and chemical properties of soil samples, the total and available contents of microelements (Fe, Cu, Zn, Ni, Mn, Co) in soils, as well as their relationship between each other were analyzed. By using geostatistics combined with GIS, the spatial variability and distribution of microelements in surveyed area were also studied, and the main results showed as follows:(1) The soils from surveyed area were of meta-alkalescence. On the whole, the content of carbonate in soils was relatively high while that of organic compound was moderate, the content of available phosphorus was low and the capacity of preserving fertility of soils was relatively weak.(2) The averages of total contents of Fe, Cu, Zn, Ni, Mn, Co in soil samples were 3.00%,31.86mg/kg,80.22mg/kg,40.22mg/kg,607.89mg/kg,13.80mg/kg, respectively. The averages of available contents of them were 8.95mg/kg,1.73mg/kg, 0.94mg/kg,0.42mg/kg,6.92mg/kg,26.13μg/kg, respectively. The variation coefficients of these microelements were high (>35%). The effective coefficients of the microelements were in the order of Cu>Zn>Mn>Ni>Co>Fe。(3) The results of correlation analysis showed that the contents of available Fe, Cu, Ni, Mn, Co were significantly negatively correlative with pH of soils. The contents of available Fe showed significantly negative correlation with the content of carbonate of the soil. The contents of available Fe, Zn, Ni, Mn, Co showed significantly positive correlation with the contents of organic compound, while the correlations of CEC content and the contents of all six available microelements were not significant. The contents of available Cu, Zn showed significantly positive correlation with the contents of available phosphorous.(4) The contents of available Ni in studied area showed strong spatial correlation, while those of available Fe, Cu, Zn, Mn, Co were of moderate spatial correlation. The ranges of the six microelements were in the order of Fe>Mn>Ni>Cu>Co>Zn。 (5) Inhomogeneity was showed in the distribution of microelements in studied area. The total contents of Fe, Cu, Zn, Co roughly decreased from southeast to northwest in this area, while those of Ni and Mn were higher in Ganzhou district than other areas. The contents of available Fe, Cu, Zn, Ni in Ganzhou district were relatively higher; the contents of available Mn in Shandan and Minle county were generally higher than that of Linze county and Ganzhou district; the distribution of available Co was similar to that of available Mn.