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| Effects of PE and PLA microplastics on net nitrogen mineralization and nitrification of farmland soil in the northern Erhai basin |
| Received:July 04, 2024 |
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| KeyWord:microplastics;net nitrogen mineralization rate;net nitrification rate;farmland soil;polyethylene（PE）;polylactic acid（PLA） |
| Author Name | Affiliation | E-mail | | WANG Xin | College of Soil and Water Conservation, Southwest Forestry University, Kunming 650224, China | | | WANG Jinrui | College of Ecology and Environment, Southwest Forestry University, Kunming 650224, China | | | HOU Lei | College of Ecology and Environment, Southwest Forestry University, Kunming 650224, China | | | WANG Yanxia | College of Soil and Water Conservation, Southwest Forestry University, Kunming 650224, China | | | LI Xiaolin | College of Soil and Water Conservation, Southwest Forestry University, Kunming 650224, China | | | LIANG Qibin | College of Ecology and Environment, Southwest Forestry University, Kunming 650224, China | qbliang@swfu.edu.cn |
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| Abstract: |
| The environmental behavior of microplastics has received extensive attention, and the difference of effects of non-degradable and degradable microplastics on soil net nitrogen mineralization and nitrification in farmland soil is worth exploring. Non-degradable polyethylene（PE）and degradable polylactic acid（PLA）microplastics with different mass fractions（1%, 2% and 3%）and particle sizes（1 mm and 3 mm）were added to the farmland soil in northern Erhai basin for a 30-day laboratory incubation experiment. The effects of different microplastics on soil physicochemical properties, net nitrogen mineralization and nitrification rate were investigated. The results showed that：PE and PLA microplastics significantly increased soil nitrate content（P<0.05）, and the increase range of soil nitrate contentafter incubation experiment was 9.64% to 28.76% and 20.75% to 47.21%, respectively. However, PE and PLA reduced the content of ammonium nitrogen in soil, but not to a significant level. The addition of microplastics significantly increased the soil net nitrogen mineralization and nitrification rates（P<0.05）, and the net nitrogen mineralization rates（0.50 mg·kg-1·d-1 and 0.63 mg·kg-1·d-1）of PE and PLA treatment were 12.50 times and 15.75 times as much as that of CK treatment（0.04 mg·kg-1·d-1）, and the net nitrification rates （0.48 mg·kg-1·d-1 and 0.62 mg·kg-1·d-1）were 12.00 times and 15.50 times as much as that of CK（0.04 mg·kg-1·d-1）. The rates of soil net nitrogen mineralization and net nitrification increased first and then decreased with the increase of PE and PLA microplastics concentration. PLA with small particle size can affect soil net nitrogen mineralization and net nitrification rate. The rates of net nitrogen mineralization and nitrification were negatively correlated with pH（P<0.01）. The results showed that both PE and PLA could promote net nitrogen mineralization and nitrification of farmland soil, and the promotion effect of degradable microplastics is more obvious than that of non-degradable microplastics. |
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