The Keta Lagoon and its catchment areas in Ghana are influenced by intensive agriculture and the use of agro-chemicals. It has therefore, become necessary to assess the quality of water in the lagoon and the surroundi...The Keta Lagoon and its catchment areas in Ghana are influenced by intensive agriculture and the use of agro-chemicals. It has therefore, become necessary to assess the quality of water in the lagoon and the surrounding fresh water aquifers. In this study, a water quality index (WQI), indicating the water quality has been adopted. The WQI was determined on a basis of various physico-chemical parameters like pH, conductivity, turbidity, dissolved oxygen, calcium, magnesium, chloride, nitrates, ammonium and sodium. The index was used both for tracking changes at one site over time, and for comparisons among sites. The WQI was also employed to wells used for irrigation on farms along the Keta Sand Spit as well as that of the Keta Lagoon Complex and its surrounding floodplains, in order to ascertain the quality of water for public and livestock consumption, irrigation, recreation and other purposes. The WQI of the wells, Keta lagoon and its floodplains showed various degrees of poor water quality and therefore considered unsuitable for drinking and recreation. By WHO standards, this calls for intensive physical and chemical treatment of the water for human consumption.展开更多
In order to measure dust's nutrient input on farmland in different agro-ecological zones, Harmattan dust was sampled by mats with plastic straw in Ghana between 2002–2006. The inputs of total nutrients by Harmatt...In order to measure dust's nutrient input on farmland in different agro-ecological zones, Harmattan dust was sampled by mats with plastic straw in Ghana between 2002–2006. The inputs of total nutrients by Harmattan dust in Ghana per Harmattan period were about 1–2 kg Ca ha-1, 0.5–2 kg K ha-1, 0.5–1.5 kg Mg ha-1and less than 0.5 kg P ha-1. Compared with the annual input of nutrients by precipitation, the dust accounted for 10% or less of Ca, Mg and K but approximately 20%–40% of P. The input of nutrients by dust was only valid for areas with vegetation, because in areas with none or sparse vegetation, loss of soil due to wind erosion and hereby loss of nutrients might be significant. In farmland areas with bare and vegetated fields there seemed to be an internal redistribution of the nutrients and not a net gain of nutrients from outside the area(long-range transported dust). The input of P by dust might be of some importance in the traditional shifting cultivation systems, while the inputs of other three nutrients of Ca, Mg and K were so low that they must be considered insignificant. In the intensive agriculture systems with huge inputs of manures and fertilizers the nutrient input by dust is insignificant and could be neglected.展开更多
文摘The Keta Lagoon and its catchment areas in Ghana are influenced by intensive agriculture and the use of agro-chemicals. It has therefore, become necessary to assess the quality of water in the lagoon and the surrounding fresh water aquifers. In this study, a water quality index (WQI), indicating the water quality has been adopted. The WQI was determined on a basis of various physico-chemical parameters like pH, conductivity, turbidity, dissolved oxygen, calcium, magnesium, chloride, nitrates, ammonium and sodium. The index was used both for tracking changes at one site over time, and for comparisons among sites. The WQI was also employed to wells used for irrigation on farms along the Keta Sand Spit as well as that of the Keta Lagoon Complex and its surrounding floodplains, in order to ascertain the quality of water for public and livestock consumption, irrigation, recreation and other purposes. The WQI of the wells, Keta lagoon and its floodplains showed various degrees of poor water quality and therefore considered unsuitable for drinking and recreation. By WHO standards, this calls for intensive physical and chemical treatment of the water for human consumption.
基金supported by the Danida-Enreca project "Ecological Laboratory" of the University of Ghana, Legon, Accra, Ghana
文摘In order to measure dust's nutrient input on farmland in different agro-ecological zones, Harmattan dust was sampled by mats with plastic straw in Ghana between 2002–2006. The inputs of total nutrients by Harmattan dust in Ghana per Harmattan period were about 1–2 kg Ca ha-1, 0.5–2 kg K ha-1, 0.5–1.5 kg Mg ha-1and less than 0.5 kg P ha-1. Compared with the annual input of nutrients by precipitation, the dust accounted for 10% or less of Ca, Mg and K but approximately 20%–40% of P. The input of nutrients by dust was only valid for areas with vegetation, because in areas with none or sparse vegetation, loss of soil due to wind erosion and hereby loss of nutrients might be significant. In farmland areas with bare and vegetated fields there seemed to be an internal redistribution of the nutrients and not a net gain of nutrients from outside the area(long-range transported dust). The input of P by dust might be of some importance in the traditional shifting cultivation systems, while the inputs of other three nutrients of Ca, Mg and K were so low that they must be considered insignificant. In the intensive agriculture systems with huge inputs of manures and fertilizers the nutrient input by dust is insignificant and could be neglected.
