长期秸秆配施鸡粪对棉田土壤重金属累积的影响及生态风险评价

Effect of long-term straw application with chicken manure on the accumulation of heavy metals in cotton field soil and ecological risk evaluation

【目的】探明长期棉花秸秆配施鸡粪对重金属元素在土壤中积累与污染状况的影响,为棉田改土培肥和安全高效施肥提供科学依据。【方法】通过14年长期定位试验,研究氮磷化肥+秸秆清茬(NP)、氮磷化肥+秸秆还田(NPS)、氮磷化肥+秸秆清茬+鸡粪(NPM)、氮磷化肥+秸秆还田+鸡粪(NPSM)4个处理对土壤中重金属积累的影响,利用污染指数法和潜在生态风险指数法评价土壤污染状况和潜在生态风险。【结果】各处理中土壤重金属的含量均未超出国家标准中的污染风险筛选值。与NP相比,NPS处理土壤重金属含量无明显增加,NPM、NPSM处理土壤汞含量分别显著提高81.8%和90.9%,NPSM处理中土壤铬、锌含量分别显著提高了7.9%和63.2%,锌、汞、铬富集明显,富集度分别为139.99%、90.91%和13.77%;铜、铅富集但处理间无显著差异。棉田土壤重金属单项污染指数为0.03~0.51,土壤污染状况均为安全级;综合污染指数为0.36~0.79,仅NPSM土壤污染状况为警戒等级;潜在生态风险污染综合指数为20.68~22.66,为轻微生态危害。【结论】连续14年棉花秸秆还田配施鸡粪,土壤重金属含量均未超标,土壤重金属评价为警戒级,潜在生态危害评价为轻微生态危害,应控制有机肥源重金属含量,减缓锌、汞、铬富集,持续保护利用土壤。

[Objective] This study aims to investigate the accumulation of heavy metal in soil under long-term application of cotton straw and chicken manure in cotton field, and provide scientific basis for a safe and efficient utilization of organic fertilizer during cotton production. [Method] The 14 years’ long-term field experiment was conducted to study the accumulation of heavy metals in soil under the following treatment setup: nitrogen and phosphorus chemical fertilizer + clearing straw stubble(NP), nitrogen and phosphorus chemical fertilizer & straw returning(NPS), nitrogen and phosphorus chemical fertilizer +clearing straw stubble + chicken manure(NPM), and nitrogen and phosphorus chemical fertilizer + straw returning + chicken manure(NPSM). The state of soil pollution and potential ecological risk were evaluated using pollution index and potential ecological risk index. [Result] The levels of heavy metals in the soil from each treatment did not exceed the threshold of heavy metal pollution according to the national standard. There was no significant difference of heavy metals content in the soil between NPS and NP. However, compared with the NP treatment, the contents of Hg in the soils of NPM and NPSM treatments were significantly increased by 81.8% and 90.9%, respectively. In addition, the contents of Cr and Zn in the soil of NPSM treatment significantly increased by 7.9% and 63.2%, and Zn, Hg, and Cr were significantly enriched, with the enrichment degree of 139.90%, 90.91%, and 13.77%, respectively. And Cu and Pb were enriched but showed no significant difference among treatments. The contamination index of single heavy metal pollution in cotton field ranged from 0.03 to 0.51, and the soil contamination status were all at the safe level. The comprehensive pollution index of different treatments was in the range of0.36-0.79, among which the NPSM treatm ent was at the alarming level. And the potential ecological risk indexes among different treatments were 20.68-22.66, inferred to slight ecological hazard. [ Conclusion] The experiment of cotton straw returning to the field with chicken manure for 14 consecutive years showed that the heavy metal content in soil did not exceed softly threshold according to the national standard, and the heavy metal content in soil was evaluated as alert and slight ecological hazard, which should be controlled by reducing the input of Zn, Hg, and Cr to maintain the sustainability of soil.