Biomonitoring Toxicity Of Nitrogen, Phosphorus And Heavy Metal In Water And Soil By The Phototactic Behavior Of Daphnia

The sustainable development of economy and the healthy existence of the human beings are seriously endangered by environmental pollution. Great public attention has been paid to the environmental problems. Being fundamental work in environmental protection, the environmental monitoring is usually divided into the physicochemical monitor and biomonitor. The former can accurately determine the absolute concentration of specific pollutants, but it is difficult to detect biotoxicity of unknown toxicants, especially the joint toxicity of more toxicants. Compared to physicochemical ones, the effectiveness of biomonitor can, otherwise, test the overall toxicities produced by single or mixtures known or unknown toxicants, even though it can't accurately determine the absolute concentrations of specific pollutants. So, physicochemical monitoring and biomonitoring need to be cooperated and replenished mutually in order to accurately provide contamination information in time.Physicochemical methods have been well used in environmental monitoring, while the biomonitor method is under developing very and still exists many limits such as poor accuracy, and complex operation and difficult application. It is thus urgent to setup some accurate, quick and reliable methods of biomonitoring in present environmental protection activities.Daphnia {Cladocero. Crustacea), an important animal of the diet for many fish, has a critical role in aquatic ecology chains. They usually reproduce parthenogenetically and are easy to be cultured. Therefore, they are widely used as a standard organism in aquatic toxicology. Many investigators have studied the toxic effects of heavy metals on Daphnia. It is a new technology abroad to detect the toxicants by using phototactic behaviour of Daphnia as biomarker, which provides a prospect application in biomonitoring. But such research is just a beginning abroad and none in China. So, a lot of fundamental research work needed to be done, including screening Daphnia, as a biomonitor, that is sensitive to toxicant but less to environment changing so as to decrease the environmental interferences for obtaining more accurate determination results; exploring the relationship between the phototactic behavior of Daphnia and pollutantssuch as nitrogen, phosphate, heavy metal, hormone and pesticide, especially their mixtures; studying the effect of environmental conditions such as temperature, pH and fish kairomones on the phototactic behavior of Daphnia. All the research above is very important to establish standard detecting methods.At present, eutrophic water and soil contaminated by heavy metals are the main environmental problems. Nitrogen, phosphate and heavy metals coexist in soil polluted and eutrophic water. But it is difficult to carry out such research work because there is no effective research method nowadays. Scientists have to ignore the mutual effect (synergism and antagonism) among different pollutants and to consider the coexisting of different pollutants as single one. Thus, it is helpful to understand mutual reactions among pollutants in heavy metal polluted soil and eutrophic water, to clarify their biological and environmental effect through studying phototactic behavior of Daphnia influenced by nitrogen, phosphate and heavy metals. The above research work indicated it was an important science item that needed to be solved before tackling the soil and water pollution.In the present experiments, Daphnia carinata clone Dc42 was screened and cultured from upstream of Yangtze River and then studied their phototaxis as well as the effect of standard toxicant on them in order to establish quick biomonitor method of pollutants. Thereafter, the mutual relationship and biotoxicity of nitrogen, phosphate and heavy metals (Cu, Zn, Cd, Cr, Pb) was studied in water and soil. The objectives are to provide theoretical and applicable means (i) to establish a quick, accurate and sensitive biomonitor method, (ii) to explore interactions among N, P and heavy metals in soils and eutrophic waters an...