Quality of groundwater and surface water in terms of inorganic nitrogen concentration in an urbanized agricultural area around Ha Noi, Viet Nam
2006
Kurosawa, K.(Kyushu Univ., Fukuoka (Japan). Inst. of Tropical Agriculture) | Do, H.N. | Nguyen, T.H. | Tran, L.H.T. | Egashira, K.
In an urbanized agricultural area near the center of Ha Noi City, pH, ORP, and ammonium-N and nitrate-N concentrations were monitored for the surface water (canal/pond) and groundwater (shallow/deep tubewell) used locally for irrigation and domestic purposes, respectively. Only vegetables were cultivated eleven times throughout the year in farmland, and the rate of annual fertilizer N application amounted to 960 - 1,150 kg/ha. The pH was in the neutral range. The ORP varied from reductive/intermediate to oxidative states. The ammonium-N concentration was high (1.3 - 15.1 mg/L), while the nitrate-N concentration was low (0.09 - 2.2 mg/L). The effect of fertilizer N application on the ammonium-N concentration was recognized in the surface water. The presence of ammonium-N in the groundwater was due to the percolation of surface water contaminated with NH4+. The effect of fertilizer N application on the nitrate-N concentration was not recognized in either surface water or groundwater. In the canal water, the ammonium-N plus nitrate-N concentration reached a harmful level for irrigation use (5 mg/L). In the groundwater, the ammonium-N concentration exceeded the critical level of drinking use for human health. Therefore, countermeasures should be urgently implemented.
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