北京东南郊环境中砷污染的研究

ARSENIC POLLUTION IN THE SOUTHEASTERN SUBURB OF BEIJING

北京东南郊属于半湿润地区,年平均降雨量600多毫米,河流的天然水补给来源少,天然水的矿化度在200—400毫克/升,水化学类型属CICa型,PH值为7.5左右,Eh值在300—400毫伏。但在工业废水排入河道后,水化学条件发生明显变化,水化学类型出现CINa型,个别河段出现CIMg型,PH值变幅较大,最低为3.61,最高可达9.46,特别是矿化度有明显的增加,达到2克/升左右。

In this district, arsenic enters into the environment in the forms of sewage, sludge and waste gas. Arsenic exists in the surface water mainly as arsenate and arsenite. Under certain conditions, arsenite can be oxidized to arsenate quickly. The purification of arsenic in the water body is obvious. Due to the irrigation with sewage and the application of sludge, the soil is polluted by arsenic in some places. The arsenic toxicity varies with the chemical forms of arsenic. For instance, Na_2HAsO_4 and NaAsO_2 are much more harmful than As_2S_2. According to our experiments, the environmental standard of arsenic that enters into the soil should be about 15mg/kg. In order to reduce and control the arsenic pollution, it is important to improve the industrial technologies. As_2O_3 should not be used in the gas desulphurization process.