6种典型农田土壤的锌吸附-解吸特性

Zinc adsorption-desorption characteristics of six typical cropland soils from northwest and southeast China

研究了中国6种典型农田土壤对锌的吸附-解吸特性,其中采自西北陕甘地区和东南地区浙江省的农田土壤各3种。结果表明,6种农田土壤对锌的吸附量均随平衡液锌浓度的增加而增大,均可用Langmuir方程、Freundlich方程和Temkin方程来描述,相关系数均达到显著或极显著水平;6种土壤对锌的解吸量随吸附量的增大而增加,它们的相关性也达到了显著或极显著水平。东南地区土壤对锌的最大吸附量明显高于西北地区,其中青紫泥的吸附量最大,达到3 333 mg.kg-1,黄绵土的最小(909 mg.kg-1);而西北地区土壤对锌的缓冲能力、吸附固定能力和固定量方面强于东南地区的红壤和青紫泥,利用Langmuir方程得出6种土壤(黄绵土、石灰性褐土、塿土、红色石灰土、红壤和青紫泥)对锌的最大缓冲容量依次为213,164,263,294,16和25 mg.kg-1;根据土壤锌吸附-解吸的线性回归曲线,计算出当土壤锌解吸量为0时,这6种土壤锌的固定量分别为56,97,126,135,55和98 mg.kg-1。浙江红色石灰土由于其pH值与西北地区土壤相似,而有机质质量分数和阳离子交换量又比较高,故对锌的缓冲能力、吸附固定量高于西北地区土壤。

Soil zinc （Zn） availability varies very greatly among different soils. Adsorption-desorption charac teristics of six typical cropland soils from northwest（Loess soil, calcareous cinnamon soil, and Lou soil） and southeast（red calcareous soil, red soil, and blue-purple soil） China were studied. Results showed that Zn adsorbed by soils increased with initial concentrations of Zinc added（from 0 - 149 mg·L^-1 solutions） and that the soil Zn desorption rate increased with the soil adsorbed Zn. Isothermal curves of Zn adsorption from these six soils fit well to Langmuir, Freundlich, and Temkin equations with all the coefficients, except the blue-purple paddy soil, being〉0.9. Soil organic matter content contributed the most to soil Zn adsorption, so regardless soil pH, maximum Zn adsorbed by soils from northwest. Blue-purple paddy soil had the greatest maximum Zn southeast China was greater than from the adsorbed （3 333 mg·kg^-1） and Loess soil the least（909 mg·kg^-1）. Regardless of soil site locations, for all the calcareous soils, the maximum soil buffering capacity, the intensity of soil Zn adsorption, and the amount of soil fixed Zn were greater than for acid soils. Due to its high organic content and CEC, red calcareous soil showed greater maximum buffering capacity（294 mg·kg^-1） and maximum amount of soil Zn fixed （135 mg·kg^-1） than the calcareous soils col- leeted from northwest China. [Ch, 2 fig. 2 tab. 23 ref. ]