The Characteristic Of Reduced Inorganic Sulfur Species In The Yangtze River Estuary And Its Environmental Significance

Most big coastal cities of east China are located in or near estuary area. With the rapid development of urban economy, a large number of heavy metal pollutants enter waters through surface runoff, and a large number of pollutants containing sulfur enter waters through acid rain, which aggravates the urban estuary and river pollution. As the origin and sink of inorganic sulfur,organic sulfur and heavy metals, the sediments of estuary area not only is the important accumulation base and pollution source, but also is the important reaction place of aquatic heavy metals.The pollutants transportation in the Yangtze River Estuary makes great contribution to the sea, and the aquatic environment of this area have great significance to the development of the surrounding cities.The study shows the research of reduced inorganic sulfur species and heavy metals in the Yangtze River Estuary area. The aim is to know the contents of inorganic sulfur species, and further find out the biology toxicity of heavy metals and pollution status to provide theoretical basis for the aquatic treatment of the Yangtze River Estuary area.The result shows that,contents of acid-volatile sulfide(AVS)in surface sediments of Chongming Dongtan range from 0.844 to 3.531μmol/g, chromium(Ⅱ)-reducible sulfide(CRS) from 2.531 to 5.156μmol/g, elemental sulfur(ES) from 0.719 to 1.125μmol/g. CRS(FeS2-S)is the main reduced inorganic sulfur species in surface sediments, which occupies from 48.2% to 67.9%.The content sequence of reduced inorganic sulfur(RIS) is high tidal flat>middle tidal flat>low tidal flat.The content sequence of RIS in surface sediments of Shanghai costal area is Lu River>Nanhui Zui>Luchaogang Farm>Wusong>Chaoyang Farm>Gulu>Fengxian>Liu River. The contents of CRS in all sampling points have the ascendant position, which shows the stability of pyrite in the sediments.The content distribution of the RIS species in columnar sediments of Chongming Dongtan present irregular characteristic. The content of ES in high tidal flat gradually increases from 10-25cm,while the content of AVS decreases.The content of humus in 5-10cm middle tidal flat is high, which shows the high extent of sulfate reduction and pyritization.So the contents of AVS and CRS are high. The palaeohydrodynamic condition in low tidal flat is strong, so the contents of three reduced inorganic sulfur in surface sediments(0-10cm) is low.The content sequence of active iron in surface sediments of Chongming Dongtan is high tidal flat>middle tidal flat>low tidal flat, and the situation is same in columnar sediments.The content sequence of active iron in surface sediments of Shanghai costal area is Lu River>Chaoyang Farm>Wusong>Luchaogang Farm>Gulu>Liu River> Fengxian>Nanhui Zui.The contribution of Zn to simultaneously extracted metals(SEM) in surface sediments of Chongming Dongtan is over 48%. SEM/AVS are all below 1 in high,middle and low tidal flat, which shows a low level of biology toxicity. Among the typical soil type of Chongming Dongtan, only the SEM/AVS of maize soil is above 1, which shows a middle level of biology toxicity. The contribution of Zn to simultaneously extracted metals(SEM) in columnar sediments of Chongming Dongtan is over 48%, so the columnar distribution pattern of SEM is mainly controlled by the distribution pattern of Zn. Among the columnar sediments of Chongming Dongtan, the heavy metal toxicity to biology in low tidal flat is the highest. Because the low tidal flat is located on the outer part of the coastal area, the sediments is greatly influenced by the tide,wind and hydrological conditions.So the heavy metal toxicity to biology reflects the heavy metal content characteristic in the tidal water.The contents of SEM in the surface sediments on different sampling points of Shanghai coastal area don't vary too much. The contribution of Zn to SEM is over 48%,and the content of Pb in all sampling points is the lowest.The SEM/AVS are all over 1 expect Gulu, which shows the middle heavy metals toxicity to biology in the surface sediments of Shanghai coastal area.