Assessment of Ammonium–N and Nitrate–N Contamination of Shallow Groundwater in a Complex Agricultural Region, Central Western Taiwan

Abstract

The characteristics of nitrogen contamination of shallow groundwater were evaluated through current status analysis and trend detection of ammonium–N and nitrate–N concentrations under various cropping patterns to assess the effectiveness of rational fertilization in the Choushui River alluvial fan, central Western Taiwan. The influence of cropping patterns on both ammonium–N and nitrate–N contamination associated with redox conditions/dissolved oxygen (DO) in shallow groundwater was also discussed in this study. The analysis revealed that shallow groundwater beneath double rice cropping and rotational cropping regions is still characterized by high ammonium–N concentration despite rational fertilization promotion. However, very few monitoring wells showed an upward trend of ammonium–N/nitrate–N concentrations, indicating that shallow groundwater is not further deteriorated by nitrogen pollution in most parts of the study area. Therefore, the remediation of nitrogen contaminated groundwater will be a long-term process and more effort must be invested. Moreover, the strict redox conditions defined by a single DO threshold value may not account for groundwater nitrogen pollution in the study area. It is difficult to determine the redox conditions and predominant nitrogen pollution patterns of shallow groundwater purely from cropping patterns. Instead, contamination may have resulted from an integrated process governed by several other factors. Tracing the potential sources of nitrogen pollution and establishing a more integral monitoring network should be implemented to formulate a more comprehensive nitrogen pollution control strategy in this area.

Challenges of Water Quality Management for Agricultural Development

“…The reasonable utilization of groundwater resources as agricultural irrigation can increase crop productivity and reduce the costs of the irrigation canal system. In the paper "Assessment of Ammonium-N, and Nitrate-N Contamination of Shallow Groundwater in a Complex Agricultural Region, Central Western Taiwan" [3], nitrogen contamination in shallow groundwater in a complex agricultural region in Taiwan was evaluated. The study analyzed the current status of Ammonium-N and Nitrate-N concentrations under various cropping patterns to assess the effectiveness of reasonable fertilization.…”

Dynamics of Organic Nitrogen Compound Mineralization in Organic Soils under Grassland, and the Mineral N Concentration in Groundwater (A Case Study of the Mazurian Lake District, Poland)

“…This was confirmed in a study by Daniels et al [64], who demonstrated that ammonium leaching was greater in the acidic upland peatlands of Great Britain. Part of the N-mineral is released in the form of ammonium, which is not readily available to plants and remains in the soil, and part is released in the nitrate form, which is the more labile form and is leached into the groundwater after phytosorption [65].…”