Coupled hydrological and biogeochemical modelling of nitrogen transport in the karst critical zone

Zhicai Zhang, Xi Chen*, Qinbo Cheng, Siliang Li, Fujun Yue, Tao Peng, Susan Waldron, David M. Oliver, Chris Soulsby

*Corresponding author for this work

Research output: Contribution to journalArticle

2 Citations (Scopus)

Abstract

Transport of nitrogen (N) in karst areas is more complex than in non-karst areas due to marked heterogeneity of hydrodynamic behaviour in the karst critical zone. Here, we present a novel, distributed, coupled hydrological-biogeochemical model that can simulate water and nitrogen transport in the critical zone of karst catchments. This new model was calibrated using integrated hydrometric, water stable isotope, and nitrogen-N concentration data at the outflow of Houzhai catchment in Guizhou province of Southwest China. Hydrological dynamics appears to control N load from the study catchment. Combining flow discharge and water stable isotopes significantly constrained model parameterisation and mitigate the equifinality effects of parameters on the simulated results. Karst geomorphology and land use have functional effects on spatiotemporal variations of hydrological processes and nitrogen transport. In the study catchment, agricultural fertilizer was the largest input source of N, accounting for 86% of the total. Plant uptake consumed about 45% of inputs, primarily in the low-lying valley bottom areas and the plain covered by relatively thick soils. Thus, a large amount of N released from soil reservoirs to the epikarst (via fractures or sinkholes) is then exported to the underground channel in the limestone area to the south. This N draining into groundwater could lead to extensive, potentially long-term contamination of the karst system. Therefore, improving the efficiency of fertilization and agricultural management in valleys/depressions is an urgent need to reduce N losses and contamination risk.

Original languageEnglish
Article number138902
Number of pages18
JournalScience of the Total Environment
Volume732
Early online date6 May 2020
DOIs
Publication statusE-pub ahead of print - 6 May 2020

Keywords

  • Distributed water-N model
  • Karst critical zone
  • Nitrogen transport
  • Tracer-aided

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