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| Effects of Cd addition on nitrogen mineralization processes of rural and urban river wetland soils in the Pearl River Estuary, China |
| Received:December 06, 2018 |
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| KeyWord:Organic nitrogen mineralization;Cd;Wetland soils;Urease enzymes;nitrifiers;The Pearl River Estuary |
| Author Name | Affiliation | E-mail | | HU Xing-yun | State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, Beijing 100875, China | | | BAI Jun-hong | State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, Beijing 100875, China | junhongbai@163.com | | WEN Xiao-jun | State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, Beijing 100875, China | | | LU Qiong-qiong | State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, Beijing 100875, China | | | WANG Wei | State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, Beijing 100875, China | | | WANG Da-wei | State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, Beijing 100875, China | |
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| Abstract: |
| Organic nitrogen mineralization of rural and urban river wetland soils from the Pearl River Estuary under different concentrations of Cd solution (A:control; B:low concentration addition, 15 mg·kg-1; C:high concentration addition, 100 mg·kg-1) were investigated using a 40-day laboratory incubation experiment. Furthermore, the effects of urease enzymes, nitrification microorganisms, and environmental factors on organic nitrogen mineralization were also analyzed. Our results showed that the rates of nitrogen mineralization of rural and urban river wetland soils under different levels of Cd treatments showed large fluctuations at the initial stage but remained stable during the late stage, and the mineralization rates of urban river wetland soils were higher than those in rural river wetland soils over the 40 days of incubation. Cd addition exhibited a stimulating effect on nitrogen mineralization at the early stage. With increasing incubation time, nitrogen mineralization of rural river wetland soils was inhibited with increasing Cd levels, while low level addition of Cd improved the rates of nitrogen mineralization of urban river wetland soils. The mineralization rates of the two types of wetland soils decreased, or even exhibited negative values, during the incubation period, which was mainly associated with an insufficient supply of substrates and with microbial nitrogen fixation and denitrification. Nitrogen mineralization rates were significantly correlated with urease activities (P<0.05). The addition of Cd inhibited urease activity in rural river wetland soils, but low levels of Cd enhanced urease activity of urban river wetland soils during the late stages of incubation. Ammonia oxidizing Archaea (AOA) undertook a large proportion of ammoxidation in rural river wetland soils (95.37%~97.86%) and urban river wetland soils (52.13%~78.15%) under different levels of Cd addition, and these are more adaptable to a pollution-stressed environment than ammonia oxidizing bacteria (AOB). With rapid development of industrialization and urbanization in the Pearl River Estuary, once Cd pollution exceeds the capacities of rural and urban river wetland soils (especially in rural river wetlands), enzyme and microbial activities are inhibited, prohibiting nitrogen mineralization of wetland soils in the long term. |
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