Investigation Of Water Quality And Study On The Mechanisms Of Hypoxia In Liaohe Estuaries

This article was supported by the special project of prophase research of key project of foundation research.----"Study on the mechanisms of hypoxia in Chinese estuaries and the controlling ways". Dissolved oxygen (DO) in water is important to maintain sea ecosystem, and "organism hungriness" will appear in some sea area if hypoxia occurs in estuaries. It is very harmful to ecosystem, organism resource, economy development and human health. There are more and more estraries in our coutry and the degree of lacking oxygen is severe because of discharging of ncessant pollutants. Liaohe estuary is investigated as typical area in this article and the mechanisms of hypoxia in estuaries and the oxygen-consumed in bottom sediments are clarified by invstigating distribution of entironmental factors and correlative analysis.Based on the analysis of marine research data of September, 2002 and September, 2003, the descriptions of the temporal and spacial distribution and changing law of DO, dissolved inorganic nitrogen (DIN), phosphate, BOD5, CODMn and total organic carbon (TOC) are made, and every environmental factor's influences on distribution of DO has been studied. The contents of nutritious matters in sendiments and sea water by experimental simulation have been studied, related with concentration of aquatic Dissolved oxygen (DO). Excessive diccharges of nutrient in riverway result in the form of hypoxia in Liaohe river estuary. Input of sea water is a primary factor that affects DO and other environmental fators distribution in the riverway and the estuary----mixing of sea water, Liaohe freshwater and discharged sewage from riverside results in complicated distribution. The changes of nutrient concentration influent DO distribution considerably, existing good correlativity between DO and nutrient. Comparing the changes of nutrient and DO concentration in sea water with sendiment by expexperimental simulation, we learn that nutrient in sendiment contribute greatly to DO distribution in water over sendiment. Growth and reproduction of phytoplankton and other biological activities add complexity on its distribution. The concentration of DO was below 0.25mmol/L in the Liaohe riverway during two years, which was not fit for survival of hydrophily life-form.