Boncompagni E, Muhammad A, Jabeen R, Orvini E, Gandini C, Sanpera C, Ruiz X, Fasola M
Dipartimento Biologia Animale, Università, Piazza Botta 9, 1-27100 Pavia, Italy.
Arch Environ Contam Toxicol. 2003 Oct;45(3):399-406. doi: 10.1007/s00244-003-0198-y.
Environments in Pakistan are subject to increasing pollution, but previous studies were very scanty. During 1999 and 2000, we assessed trace element contamination at three wetlands, Karachi Harbour (with presumed industrial-urban pollution), Taunsa Barrage (agricultural pollution), and Haleji Lake (relatively unpolluted), using as indicators the eggs and the feathers of colonial waterbirds, particularly Little Egrets, their prey, and the sediments collected within their foraging areas. The concentrations of As, Cd, Cr, Pb, Hg, Mn, Se, and Zn were generally within the normal background level, and mostly below the threshold that may affect bird survival or reproduction. However, somewhat high concentrations were found in fish from Karachi, for Pb that was at levels that may harm fish reproduction, and for Hg that was at limit concentration for human consumption. Alarming concentrations were found for Cr and Se in sediments from Karachi, that were above the critical levels for contaminated soil, and Se in eggs, that may affect egret reproduction. The differences among the three wetlands were less marked than hypothesized. The egret species within the same area differed in the concentration of certain elements in their eggs, possibly because females may have foraged in different habitats before breeding, whereas no interspecies difference was found in chick feathers, presumably because their food had been collected in similar habitats around the colony. High bioaccumulation from sediments to organic samples occurred for Hg, while Cd, Se, and Zn exhibited low accumulation; for all these elements, feathers of predatory birds such as the egrets are the best indicators of environmental contamination. On the other hand, As and Cr did not bioaccumulate, and the sediments, or the organisms low in the food chain, like fish or crustaceans, are better indicators of their presence in the environment than predatory birds.
巴基斯坦的环境正遭受日益严重的污染,但此前的研究非常匮乏。在1999年至2000年期间,我们以群居水鸟(特别是小白鹭)的卵和羽毛、它们的猎物以及在其觅食区域收集的沉积物为指标,评估了三个湿地的微量元素污染情况,这三个湿地分别是卡拉奇港(推测存在工业 - 城市污染)、陶恩萨拦河坝(农业污染)和哈莱吉湖(相对未受污染)。砷、镉、铬、铅、汞、锰、硒和锌的浓度总体上处于正常背景水平,且大多低于可能影响鸟类生存或繁殖的阈值。然而,在卡拉奇的鱼类中发现了一些较高的浓度,铅的浓度可能会损害鱼类繁殖,汞的浓度达到了人类食用的限量标准。在卡拉奇的沉积物中发现铬和硒的浓度令人担忧,高于污染土壤的临界水平,在卵中发现的硒可能会影响白鹭的繁殖。这三个湿地之间的差异并不像假设的那么明显。同一区域内的白鹭物种在其卵中某些元素的浓度上存在差异,可能是因为雌性在繁殖前可能在不同的栖息地觅食,而在雏鸟的羽毛中未发现种间差异,大概是因为它们的食物是在繁殖地周围类似的栖息地收集的。汞从沉积物到有机样本的生物累积量很高,而镉、硒和锌的累积量较低;对于所有这些元素,白鹭等食肉鸟类的羽毛是环境污染的最佳指标。另一方面,砷和铬不会生物累积,沉积物或食物链底层的生物,如鱼类或甲壳类动物,比食肉鸟类更能作为它们在环境中存在的指标。