氮肥-垃圾渗滤液复合影响区非饱和-饱和带全剖面氮素分布特征及微生物响应

农田氮肥和垃圾填埋场渗滤液是我国地下水氮素污染的两大来源,从氮肥-垃圾渗滤液复合影响区域内采集6份土壤剖面-地下水样品,分析非饱和-饱和带全剖面中氮素的分布特征,来清晰判识该类典型区域的氮素跨介质污染特征和途径,同时通过高通量测序进行氮循环功能微生物分析,来解析氮循环功能微生物对氮素分布的响应.结果发现,在高施肥量采样...

Nitrogen distribution characteristics and microbial responses in the unsaturated and saturated zones affected by both nitrogen fertilizer and landfill leachate

In China, nitrogen fertilizer from agricultural lands and leachate from landfills are two main sources of nitrogen pollution in groundwater. In this paper, the study area was affected simultaneously by nitrogen fertilizer and landfill leachate. We collected both profile soil and groundwater samples from six sampling sites, in order to clearly identify the distribution characteristics and transport pathways of nitrogen in the vadose zone-groundwater system in such an area. In addition, the nitrogen-cycling functional microorganisms were also investigated using the high throughput sequencing method to clarify the response of nitrogen-cycling functional microorganisms to nitrogen distribution. The results showed that both NO₃^--N and DON contents were significantly higher in the soil of sampling sites with higher fertilization rates. NO₃^--N accumulated mainly within the soils at depths of 0~240 cm (p<0.05). Part of the NO₃^--N infiltrated into the groundwater, resulting in the highNO₃^--N levels(accounting for 31.93%~84.70% of TDN) and high nitrifying bacteria abundance (accounting for 27.08%~87.99% of nitrogen-cycling functional microorganisms) in groundwater at highly fertilized sites (p<0.01). This indicated that nitrogen fertilizer was the main source of NO₃^--N in the groundwater of this area. Furthermore, NH₄⁺-N was mainly distributed at depths of 0~240 cm and 400~460 cm (p<0.05) in the unsaturated zone. The NH₄⁺-N in the groundwater samples downstream of the landfill accounted for 26.40%~59.71% of the TDN concentrations, all exceeding the groundwater quality standard (GB/T 14848-2017). The landfill leachate was probably not only a significant contributor to the NH₄⁺-N in groundwater, but was also likely to be a main cause for the high accumulation of NH₄⁺-N (p<0.05) in deep soil near the groundwater table. These results would be helpful to assess and control nitrogen pollution from multiple sources.