硫酸钙对土壤盐度指标换算关系的影响

以新疆南部典型盐渍土为研究对象,分析了微溶性盐分CaSO4对土水比1∶5浸提液电导率(EC1∶5)与电解质总浓度(TEC1∶5)、溶解性固体浓度(TDS)、土壤含盐量(St)换算关系的影响。结果表明:当浸提液CaSO4浓度未饱和时,由EC1∶5推算TEC1∶5、TDS1∶5和St的换算系数分别为10.00、0.64和3.20;而当浸提液中CaSO4为饱和状态时,由于浸提液中存在CaSO4的电离平衡,测定Ca2+或SO42-时引起未电离的CaSO4进一步电离,进而使得测定得到的TEC1∶5数值较浸提液实际情况偏高,导致由EC1∶5推算TEC1∶5、TDS1∶5和St的转换系数变大,分别增加至12.50、0.80和4.00。

Effects of Calcium Sulphate on Conversion Relationships of Salinity Indices

Slat-affected soils in south Xinjiang Province were selected. Based on 1：5 soil to water extract method, electrical conductivity （EC1：5 ）, total electrolyte concentration （TEC1：5 ）, total dissolved solids （TDS1：5） and soil salt content （St） were determined. Then effects of CaSO4 on conversion factors between EC1：5 and TEC1：5 , TDS, and S, were analyzed. Results showed that when CaSO4 in 1：5 extract was unsaturated, the conversion factors from EC1：5 to TEC1：5 , TDS1：5 , and S, were 10.00, 0.64 and 3.20, respectively. If CaSO4 was in saturation condition, however, theses conversion factors would increase to 12.50, 0.80 and 4.0, respectively. There are some CaSO4 in unionization condition for a extract with CaSO4 in saturation. When determination is performed for Ca^2＋ or SO4^2- leading to decrease in Ca^2＋ or SO4^2- concentration in extract, the unionized CaSO4 will ionize into Ca^2＋ and SO4^2-. Therefore, the value of TEC1：5 increased thereby resulting in the increment of conversion factors between EC1：5 and TEC1：5 , TDS1：5 , and St.