Sources and behaviour of nitrogen compounds in the shallow groundwater of agricultural areas (Poyang Lake basin, China)

Evgeniya Soldatova, Natalia Guseva, Zhanxue Sun, Valeriy Bychinsky, Pascal Boeckx, Bai Gao

Research output: Contribution to journalArticle

23 Citations (Scopus)

Abstract

Nitrogen contamination of natural water is a typical problem for various territories throughout the world. One of the regions exposed to nitrogen pollution is located in the Poyang Lake basin. As a result of agricultural activity and dense population, the shallow groundwater of this area is characterised by a high concentration of nitrogen compounds, primarily NO3, with the concentration varying from 0.1 mg/L to 206 mg/L. Locally, high ammonium content occurs in the shallow groundwater with low reduction potential Eh (< 100 mV). However, in general, the shallow groundwater of the Poyang Lake basin has Eh > 100 mV. To identify sources of nitrogen species and the factors that determine their behaviour, the dual stable isotope approach (δ15N and δ18О) and physical-chemical modelling were applied. Actual data were collected by sampling shallow groundwater from domestic water supply wells around the lake. The δ18О values from − 4.1‰ to 13.9‰ with an average value of 5.3 permille indicate a significant influence of nitrification on nitrogen balance. The enrichment of nitrate with the 15N isotope indicates that manure and domestic sewage are the principal sources of nitrogen compounds. Inorganic nitrogen speciation and thermodynamic calculations demonstrate the high stability of nitrate in the studied groundwater. Computer simulation and field observations indicate the reducing conditions formed under joint effects of anthropogenic factors and appropriate natural conditions, such as the low-level topography in which decreased water exchange rate can occur. The simulation also demonstrates the growth in pH of the groundwater as a consequence of fertilisation, which, in turn, conduced to the clay mineral formation at lower concentrations of aqueous clay-forming components than the ones under the natural conditions.

Original languageEnglish
Pages (from-to)59-69
Number of pages11
JournalJournal of Contaminant Hydrology
Volume202
DOIs
Publication statusPublished - 2017

Keywords

  • Jiangxi Province
  • NH
  • Nitrogen cycle
  • Redox geochemistry
  • Stable isotopes
  • Thermodynamic modelling

ASJC Scopus subject areas

  • Environmental Chemistry
  • Water Science and Technology

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