地理学报 ›› 2019, Vol. 74 ›› Issue (9): 1878-1889.doi: 10.11821/dlxb201909013

• 土地利用与生态环境 • 上一篇    下一篇

基于水环境化学及稳定同位素联合示踪的土地利用类型对地下水体氮素归趋影响

路路1,2,戴尔阜2(),程千钉3,邬真真3   

  1. 1. 生态环境部环境规划院战略规划部,北京 100012
    2. 中国科学院地理科学与资源研究所,北京 100101
    3. 北京师范大学环境学院,北京 100875
  • 收稿日期:2018-05-31 修回日期:2019-07-31 出版日期:2019-09-25 发布日期:2019-09-25
  • 作者简介:路路(1985-), 男, 博士, 主要从事土地利用变化下的环境效应研究。E-mail: lulu@igsnrr.ac.cn
  • 基金资助:
    国家自然科学基金青年基金项目(41701559);中国博士后科学基金项目(2016LH0002);中国博士后科学基金项目(2017M620890)

The sources and fate of nitrogen in groundwater under different land use types: Stable isotope combined with a hydrochemical approach

LU Lu1,2,DAI Erfu2(),CHENG Qianding3,WU Zhenzhen3   

  1. 1. Environmental Strategy Institute, Chinese Academy for Environmental Planning, Beijing 100012, China
    2. Institute of Geographic Sciences and Natural Resources Research, CAS, Beijing 100101, China
    3. School of Environment, Beijing Normal University, Beijing 100875, China
  • Received:2018-05-31 Revised:2019-07-31 Published:2019-09-25 Online:2019-09-25
  • Supported by:
    National Natural Science Youth Foundation of China(41701559);Postdoctoral Science Foundation of China(2016LH0002);Postdoctoral Science Foundation of China(2017M620890)

摘要:

识别复杂土地利用类型对地下水体氮素归趋的影响一直是非点源污染研究中的重点及难点。本文采用水环境化学及同位素联合示踪法对具有复杂地类的三江平原阿布胶河流域地下水体中氮素归趋进行解析研究。结果表明:研究区域内地下水体中存在严重的氮素污染,部分点位超出标准限值近4倍。土地利用类型不仅是氮素浓度和水化学类型演变的主导因素,而且对地下水体氮素循环过程及氮素来源产生了重要的影响。其中:在林地区域内,硝态氮占主导,氮素主要来源于土壤有机氮硝化;在城镇区域内,硝态氮超标,具有较高的氯离子浓度,主要来源于粪便及废水,受硝化过程所控制;在水田区域:铵态氮超标,具有较高的硝酸盐同位素值(δ 15N-NO3 -和δ 18O-NO3 -)且二者存在显著的线性关系,表明存在着显著的反硝化过程。在旱田区域,硝态氮占主导,氮素来源及循环过程较为复杂,受反硝化及雨水混合过程等多重影响,难以单一使用同位素示踪法进行溯源解析。通过联合水化学解析法能进一步揭示该区域氮素污染主要来源于肥料施用。因此,通过联合示踪法能够补充复杂土地利用区域氮素来源识别工作的缺陷,提升地下水体氮素归趋识别的精度。

关键词: 地下水体氮素, 土地利用, 同位素, 归趋, 多变量统计分析

Abstract:

Identifying the sources and fate of nitrogen in groundwater is challenging in areas with diverse land use types and multiple potential inputs. The Abujiaohe river basin in China's Sanjiang Plain, which has mixed land use types, including forestland, upland, paddy fields, and residential areas, was selected as the study area. Multiple environmental tracers, including hydrochemical and stable isotopes of nitrate (δ 15N-NO3 - and δ 18O-NO3 -) from groundwater, were examined. A biplot approach (δ 15N-NO3 - and δ 18O-NO3 -) combined with multivariate statistical analysis of hydrochemical data was used to investigate the sources and fate of nitrogen in groundwater. The results showed that severe nitrogen pollution—the highest concentration found in this study exceeded the national limit by four times—was present in both towns and agricultural areas. Land use was not only the dominant determining factor of nitrogen concentration and groundwater chemistry type, but also had a key impact on the regional nitrogen cycle and nitrogen sources. In the forestland, dominant nitrate was mainly derived from organic nitrogen nitrification in the soil. In residential areas, excessive NO3 - with high Cl - concentrations derived from manure and septic waste, which was controlled by the nitrification process. In paddy fields, low NO3 -, combined with high NH4 + and stable isotopes of nitrate concentrations, was observed. The linear relationship between δ 15N-NO3 - and δ 18O-NO3 -indicated that the occurrence of significant denitrification led to the limited presence of isotopic tracer. The uplands, affected by multiple factors such as rainfall and denitrification, had a more complex N cyclic process. Ultimately, multivariate statistical analysis results showed that the reduction of nitrogen fertilizer input was the main reason for nitrogen pollution. Therefore, the combined approach of using nitrogen isotopic ratios and conventional multivariate statistical analysis allowed for the more reliable separation of nitrogen sources in groundwater. This approach can help us to initiate more targeted remediation strategies.

Key words: nitrogen in groundwater, land use, stable isotopes, sources and fate, multivariate statistical analysis