有机污染水灌溉对土壤有机碳状况的影响

以长期采用有机污染型水灌溉的陕西交口灌区的农田土壤作为研究对象,并以气候条件、土壤条件以及耕作制度基本一致,长期采用未污染的地下水灌溉的农田土壤作为对照,分别测定土壤剖面上总有机碳含量、有机碳组成等指标,结合第二次全国土壤普查资料,分析长期采用有机污染水灌溉对土壤有机碳累积速率及有机碳密度的影响,探讨关中土壤"环境碳容量"水平及提升土壤有机碳潜力的途径。结果表明:长期采用有机污染水灌溉,土壤有机碳主要在耕层(0~20 cm)极显著地增加,且增加部分主要是活性有机碳组分,其累积速率是对照灌区的近3倍,非活性有机碳处于相对平衡状态。土壤有机碳的剖面分布发生了明显的分化现象,活性有机碳的变化比总有机碳的变化更为显著。有机污染水灌溉的土壤有机碳密度显著高于对照土壤,尤其在0~40 cm范围内其差异达极显著水平。结果证实渭河水中富含的有机污染物提升了灌溉农田土壤有机碳贮量,关中地区农田土壤环境碳容量仍未达到饱和水平,通过外源有机碳的输入,仍然有增加土壤有机碳含量的可能。

Effects of irrigation with organically polluted water on soil organic carbon

An experiment was carried out on the farmland soil which was irrigated with organically polluted water for many years in the Jiaokou Irrigation Area,and the soil irrigated with unpolluted ground water was used as the control treatment.The climatic conditions,soil conditions and farming system of the two sample areas were basically consistent.The total organic carbon content and composition in the soil profile were respectively determined,combined with the second national soil survey data,the accumulation rate and density of organic carbon were proved and "the environment carbon capacity" levels of Guanzhong soil and the rising potential of its soil organic carbon were analysed.The results show that: long-term irrigation with organically polluted water can significantly increase organic carbon content in topsoil(0～20 cm),and the increased part mainly was the active organic carbon fractions.The accumulation rate of organic carbon was nearly 3 times as much as the control soil.Non-active organic carbon was in relative balance.The profile distribution of soil organic carbon also underwent obvious differentiation.The change of active organic carbon was more remarkable than the total organic carbon.Soil organic carbon density was also evidently higher in the soil irrigated with organic polluted water than in the control soil,especially in the 0～40 cm layer,and the difference reaches extremely significant level.This experiment confirmed that the Weihe River water is rich in organic matter,and the environment carbon capacity of the farmland soil in Guanzhong area has not yet reached saturated level.The input of exogenous organic carbon can still enhance the soil organic carbon content.