崇明东滩湿地营养盐与重金属的分布与累积

Distribution and accumulation of nutrients and heavy metals in Dongtan wetlands on Chongming Island, China

测定了崇明东滩湿地盐沼植物和沉积物中TN、TP、重金属Cu、Zn、Pb和Cd的含量,阐明了它们在湿地中的分布与累积特征,评估3种盐沼植物对营养盐和重金属的富集能力,并讨论了互花米草入侵对长江口湿地生态系统可能造成的影响。海三棱镳草地上部分的TN、Cu、Pb和Cd的含量均显著高于芦苇和互花米草(p<0·01),而地上部分TP和Zn却表现为:海三棱镳草和互花米草无显著性差异(p>0·05),但均显著高于芦苇(p<0·01)。东滩湿地沉积物中TN和重金属的分布与累积特征为:芦苇带>互花米草带>海三棱镳草带>光滩,即随着高程的增加,沉积物中TN和重金属的含量逐步上升;但沉积物中TP含量变化不大,基本维持在0·06%左右。基于盐沼植物地上部分的生物量,估算了3种盐沼植物地上部分的营养盐和重金属库,结果表明:互花米草地上部分的养分库和重金属库均大于芦苇和海三棱镳草,表明收获互花米草对环境的净化效果最佳,特别对磷的去除效率是最高的。

The rapid growing estuary wetlands resulted from Yangtze River sedimentations on Chongming Island of eastern Shanghai, China is accompanied with invasion of spartina （ Spartina alterniflora）, which collective shape the overall function of the coastal ecosystems. The objective of this study is to quantify the distribution and accumulation of nutrients and heavy metals in the salt marsh plants and their sediments in Dongtan wetlands. The total nitrogen （TN）, total phosphorus （TP） and heavy metals （Cu, Zn, Pb and Cd） were measured from the sediments and the plant tissues of Phragmites australis, S. alterniflora, and Scirpus mariqueter. It was found that TN ,Cu,Pb and Cd in the aboveground part of S. mariqueter were significantly higher than those of P. australis and S. alterniflora （p 〈 0. 01 ）, while TP and Zn in the aboveground part of P. australis were significantly lower than those of S. mariqueter and S. alterniflora （p 〈 0.01 ）. We also found that the distribution of TN and heavy metals in the sediments had similar levels in an order of P. australls zone 〉 S. alterniflora zone 〉 S. mariqueter zone 〉 mudflat zone. With increasing in elevation, TN and heavy metals also increased but TP in the sediment remained at about 0.06%. Measured by aboveground standing stock, it appeared that all nutrients and heavy metals of invasive S. alterniflora had higher levels than those of native P. australis and S. mariqueter. The TN stock of S. alterniflora was about 1.5 and 2.6 times higher than those of P. australis and S. mariqueter, respectively. The aboveground standing TP stock was about 3.8 and 5.2 times higher than those of P. australis and S. mariqueter, respectively. Clearly, removals of S. alterniflora through harvesting can be an effective management protocols to reduce nutrients and toxic heavy metals from the site.