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| Effects of different microplastics on soil properties and Cd availability and fraction in paddy soil |
| Received:February 27, 2023 Revised:April 13, 2023 |
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| KeyWord:microplastic;heavy metal speciation;available cadmium;biodegradable plastic;enzyme activity |
| Author Name | Affiliation | E-mail | | HU Yujie | College of Environmental Sciences, Sichuan Agricultural University, Chengdu 611130, China | | | WU Jun | College of Environmental Sciences, Sichuan Agricultural University, Chengdu 611130, China | | | YANG Gang | College of Environmental Sciences, Sichuan Agricultural University, Chengdu 611130, China | | | XU Min | College of Environmental Sciences, Sichuan Agricultural University, Chengdu 611130, China | xumin_xyz@126.com |
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| Abstract: |
| 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 types[polyethylene 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. |
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