School of Resources and Environment Science, East China Normal University, 500 Dongchuan Road, Shanghai, 200241, China.
Environ Sci Pollut Res Int. 2014 Sep;21(17):10174-85. doi: 10.1007/s11356-014-2944-2. Epub 2014 May 3.
The purpose of this research was to thoroughly analyze the influences of environmental factors on denitrification processes in urban riparian soils. Besides, the study was also carried out to identify whether the denitrification processes in urban riparian soils could control nonpoint source nitrogen pollution in urban areas. The denitrification rates (DR) over 1 year were measured using an acetylene inhibition technique during the incubation of intact soil cores from six urban riparian sites, which could be divided into three types according to their vegetation. The soil samples were analyzed to determine the soil organic carbon (SOC), soil total nitrogen (STN), C/N ratio, extractable NO3 (-)-N and NH4 (+)-N, pH value, soil water content (SWC), and the soil nitrification potential to evaluate which of these factors determined the final outcome of denitrification. A nitrate amendment experiment further indicated that the riparian DR was responsive to added nitrate. Although the DRs were very low (0.099 ~ 33.23 ng N2O-N g(-1) h(-1)) due to the small amount of nitrogen moving into the urban riparian zone, the spatial and temporal patterns of denitrification differed significantly. The extractable NO3 (-)-N proved to be the dominant factor influencing the spatial distribution of denitrification, whereas the soil temperature was a determinant of the seasonal DR variation. The six riparian sites could also be divided into two types (a nitrate-abundant and a nitrate-stressed riparian system) according to the soil NO3 (-)-N concentration. The DR in nitrate-abundant riparian systems was significantly higher than that in the nitrate-stressed riparian systems. The DR in riparian zones that were covered with bushes and had adjacent cropland was higher than in grass-covered riparian sites. Furthermore, the riparian DR decreased with soil depth, which was mainly attributed to the concentrated nitrate in surface soils. The DR was not associated with the SOC, STN, C/N ratio, and pH. Nitrate supply and temperature finally decided the spatiotemporal distribution patterns of urban riparian denitrification. Considering both the low DR of existing riparian soils and the significance of nonpoint source nitrogen pollution, the substantial denitrification potential of urban riparian soils should be utilized to reduce nitrogen pollution using proper engineering measures that would collect the polluted urban rainfall runoff and make it flow through the riparian zones.
本研究旨在深入分析环境因素对城市河岸带土壤反硝化过程的影响。此外，本研究还探讨了城市河岸带土壤的反硝化过程是否能够控制城市非点源氮污染。采用乙炔抑制技术，在 6 个城市河岸带不同植被类型的原状土芯培养过程中，测量了 1 年的反硝化速率（DR）。对土壤样品进行分析，以确定土壤有机碳（SOC）、土壤全氮（STN）、C/N 比、可提取的硝态氮（NO3--N）和铵态氮（NH4+-N）、pH 值、土壤含水量（SWC）和土壤硝化潜力，以评估这些因素中哪些决定了反硝化的最终结果。硝酸盐添加实验进一步表明，河岸带 DR 对添加的硝酸盐有响应。尽管由于进入城市河岸带的氮量较少，DR 非常低（0.099~33.23ngN2O-Ng(-1)h(-1)），但反硝化的时空格局差异显著。可提取的硝态氮被证明是影响反硝化空间分布的主导因素，而土壤温度是季节性 DR 变化的决定因素。根据土壤 NO3--N 浓度，这 6 个河岸带也可分为两种类型（硝酸盐丰富和硝酸盐胁迫的河岸系统）。硝酸盐丰富的河岸系统的 DR 明显高于硝酸盐胁迫的河岸系统。有灌木覆盖和毗邻农田的河岸带的 DR 高于草覆盖的河岸带。此外，随着土壤深度的增加，河岸带的 DR 降低，这主要归因于表层土壤中硝态氮的集中。DR 与 SOC、STN、C/N 比和 pH 值无关。硝酸盐供应和温度最终决定了城市河岸带反硝化的时空分布模式。考虑到现有河岸带土壤的 DR 较低和非点源氮污染的重要性，应利用城市河岸带土壤的大量反硝化潜力，通过适当的工程措施收集受污染的城市降雨径流，并使其流经河岸带，从而减少氮污染。
