Monitoring of inorganic nitrogen in surface and groimdwater at the intensive farming villages of the Red River Delta, Viet Nam

摘要

The quality of surface water (canal and pond water) and groimdwater (well water) was monitored with an interval of 6 months from 2002 to 2005 at two farming villages near Ha Noi, Viet Nam. In the villages, two rice and one winter crop were cultivatedwithin a year, in which massive amounts of chemical fertilizer-N were applied consecutively. The ammonium-N concentration ranged from 0.01 to 11.6 mg/L for surface water and from trace level to 5.6 mg/L for groundwater. The nitrate-N concentration rangedfrom 0.04 to 0.95 mg/L for surface water and from 0.01 to 1.2 mg/L for groundwater. These concentrations did not increase with time. It was considered that surface water must be carefully used for the irrigation of agricultural crops, because the ammonium-N plus nitrate-N concentration exceeded a threshold value of 5 mg/L at several times during the monitoring period, above which some damage for crop growth might happen. The ammonium-N concentration of groundwater was proportional to the annual amountof chemical fertilizer-N applied at the villages, suggesting a positive effect of the application of chemical fertilizer-N on an ammonium-N concentration of groundwater. Groundwater was unsuitable for drinking, because the ammonium-N concentrations mostly exceeded a level of 0.78 mg/L, above which human internal organ systems might be damaged. The nitrate-N concentration of groundwater satisfied the water standard for drinking use.