不同微塑料对水稻土性质、镉有效性及其形态的影响

土壤中重金属与微塑料(MPs)复合污染越来越普遍，然而关于MPs对土壤中重金属的有效性和形态的影响及其机制尚不清楚。本文以镉(Cd)污染水稻土为研究对象，通过土培试验探究不同MPs类型聚乙烯微塑料(PE-MPs)、聚己二酸-对苯二甲酸丁二酯微塑料(PBAT-MPs)]及不同添加量(0.5%、1%、2%,m/m)对土壤理化性质和酶活性的影响，并分析MPs对土壤Cd有效性及形态的影响及其机制。结果表明，1%、2%PBAT-MPs处理能显著提高土壤pH、溶解性有机碳(DOC)含量、铵态氮含量、脲酶活性、脱氢酶活性和过氧化氢酶活性，并显著降低总溶解性氮(TDN)、硝态氮和速效磷含量；而PE-MPs处理降低了土壤DOC含量，增加了土壤TDN含量。可见，PBAT-MPs对土壤理化性质及酶活性的影响比PE-MPs更显著。PE-MPs和PBAT-MPs均能显著降低CaCl₂-Cd含量，分别降低了4.6%～8.7%和4.3%～22.4%。与空白相比，0.5%、1%和2%PE-MPs处理下酸溶态Cd占比增加了1.0%～1.8%，可氧化态Cd占比降低了1.0%～1.3%;1%和2%P...

Effects of different microplastics on soil properties and Cd availability and fraction in paddy soil

Co-contamination of soil with heavy metals and microplastics(MPs)is becoming more widespread. However, it is still unclear how microplastics affect the availability and fractions of heavy metals. In this study, a soil incubation experiment was conducted using cadmium(Cd) -contaminated paddy soil to determine the effects of different microplastic typespolyethylene microplastics, PE-MPs; poly (butylene adipate-co-butylene terephthalate)microplastics, PBAT-MPs] and varying microplastic dosages(0.5%, 1%, and 2%, m/m)on soil properties and enzyme activity. In addition, the change in and potential mechanism of the availability and fraction of Cd in soil induced by MPs were investigated. Results showed that 1% and 2% PBAT-MPs addition significantly increased the soil pH, dissolved organic carbon(DOC), ammonium nitrogen, urease, dehydrogenase, and catalase, and reduced total dissolved nitrogen(TDN), nitrate nitrogen, and available phosphorus. However, PE-MPs reduced the DOC but increased soil TDN. Both PBAT-MPs and PE-MPs altered soil properties, which was more prominent in PBAT-MPs-treated soil than in PE-MPs-treated soil. The intervention of PE-MPs and PBAT-MPs significantly reduced the content of CaCl₂-Cd by 4.6%-8.7% and 4.3%-22.4%, respectively. Compared to the control, 0.5%, 1%, and 2% PE-MPs treatments increased the proportion of acid extraction Cd by 1.0%-1.8%, and decreased the proportion of oxidizable Cd by 1.0%-1.3%. Treatments of 1% and 2% PBAT-MPs increased the proportion of acid extraction Cd by 6.6% and 9.5%, and decreased the reducible Cd by 6.6% and 9.2%. The results indicated that both PE-MPs and PBAT-MPs affected the availability and fractions of Cd in soil. Redundancy analysis showed that DOC was positively correlated with acid extraction Cd but had a negative correlation with reducible Cd. Moreover, pH was positively correlated with acid extraction Cd. This indicated that MPs affected the fraction of Cd in soil via soil DOC and pH. The results show that both MPs could affect the properties and Cd fraction of Cd-contaminated paddy soil, and that PBAT-MPs has the more significant effect on soil and has a stronger activation effect on Cd in soil.