珠江口咸淡水交汇区水中COD_（Mn）、油类、砷自净规律的试验研究

用采自珠江口咸淡水交汇区河段的水和沉积物进行自净试验。试验池内介质由某一段面的水和相应断面的沉积物组成。试验按加入和未加入污染物、流动状态和静止状态的条件组合进行。从试验获得的数据看，在加入污染物的试验池水中，ＣＯＤＭｎ、油类和砷含量变化有如下规律：以石油含量降解最为迅速，在１—３ｄ内可降至未加入水平；其次是砷，自净速度与盐度有关，其含量降解５０％时在低盐度水试验池中为６ｈ，在盐度较高水中约需２ｄ，水中ＣＯＤＭｎ、油类和砷的自净作用在试验开始后的第一天里进行最快；相同介质的试验池比较，动态条件比静态条件更有利于水中污染物的自净。此外，还应用试验结果对珠江口咸淡水交汇区水中污染物自净效应作了初步的估算。

AN EXPERIMENTAL STUDY ON THE SELFPURIFICATION OF COD_(Mn),OIL AND AS IN THE MIXING AREA OF SALTWATER AND FRESHWATER IN ZHUJIANG RIVER ESTUARY

his paper reports on the self-purification experiment by using water and sediments taken from the mixing area of saltwater and freshwater in Zhujiang River estuary, which imitates the self-purification process.The experiment was conducted under conditions of having added or non-added pollutants,and in flowing or non-flowing state.According to concentration data of CODMn,oil and As in these processes,four trends have been discovered:(1)The decay of oil concentration is fastest among the pollutants,only taking 1-3 days to decrease to the level of non-added pollutant.(2) The decay of As concentration is slower,depending on the salinity of water.Half decay time is 6 hrs.in low salinity water,but 2 days in water with higher salinity.(3) Self-purification is the major process during the first 24 hrs.in each experiment,especially during the first 6 hrs..(4)The decay of concentrations of these pollutants takes faster place in a flowing system than in non-flowing systems with the same media.Based on these results, it can be estimated that: Oil in water will be purified completely,As will be reduced about 50%, and CODMn will be nearly unchanged when a pile of water flows through the mixing area.