When Rain Falls To The Ground
When rain falls to the ground, the water does not stop moving. Some of it flows along the land surface to streams or lakes. Some are used by plants. Some evaporate and returns to the atmosphere. And some seep underground, into pores between sand, clay and rock formations called aquifers.
Water moves through aquifers much like a glass of water poured onto a pile of sand (EPA, 2010). Only a small fraction (about 2.5%) of earth's water is fresh and suitable for human consumption. The rest (more than 97%) is in oceans and seas. Of the less than 2.5% of fresh water approximately 13% is groundwater; an important source of drinking water for many people worldwide (Bachmat, 1994). For example, more than 50% of the world's population depends on groundwater for drinking water.
For many rural and small communities, groundwater is the only source of drinking water (Canter, 1987).Nitrate (NO3) is a problem as a contaminant in drinking water, primarily from groundwater and wells, due to its harmful biological effects. High concentrations can cause methemoglobinemia, and have been cited as a risk factor in developing gastric an intestinal cancer. Due to these heath risks, a great deal of emphasis has been placed on finding effective treatment processes to reduce nitrate concentrations to safe levels. An even more important facet to reduce the problem is prevention measures to stop the leaching of nitrate from the soil. Some suggest that reducing the amount of fertilizers used in agriculture will help alleviate the problem, and may not hurt crop yields (Lee H. et al, 2000).
Other new developments in leach pits and slurry stores help to control the nitrate that comes from stored manure. By installing these prevention methods and reducing the amount of fertilizer used, the concentration of nitrate in the groundwater can be reduced over time. Treatment processes, such as ion exchange can have an immediate effect on reducing levels in drinking water. These processes do not remove the entire nitrate, but can help to bring the concentration down to the suggested level of 10mg/L (WHO, 2004).
When nitrate - nitrogen concentrations reach excessive levels there can be harmful biological consequences for the organisms which depend on groundwater. Of course, human interest is of primary concern when setting guidelines for acceptable nitrate levels and proper agricultural practices. The United States Environmental Protection Agency established the current drinking water standard and health advisory level of 10 mg/L nitrate-nitrogen (equivalent to 10 ppm nitrate-nitrogen or 45 ppm nitrate) based on the human health risks due to nitrate consumption (Kross, 1993).
Although there have been studies performed attempting to link nitrate consumption to various illnesses, only methemoglobinemia, (also infant cyanosis or blue-baby syndrome) has been proven to result from ingestion of water containing high nitrate concentrations, above 10 ppm (Kross, 1993).Source: National Statistical Office, 2008Figures 1.1 Fertilizer use in ThailandNational Statistical Office, (2008) was reported the information of fertilizer use in Thailand, a trend of using is increasing in advance rate. For the using of nitrogen fertilizer (46-0-0, NPK) in study area is also very high;Paddy field406.25 kg/haClay : 16-20-0Sand 16-16-846-0-0Sugar cane468.75 kg/ha16-20-046-0-0
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