珠江河口重金属镉的含量与分布的季节特征

摘要

Seasonal characteristics of cadmium were studied in the Pearl River estuary from February to November,2008, including distribution of cadmium in water bodies, sediments and aquatic animals. For water samples, 1L water was collected from 0.5 m below surface and fixed with 2 mL hydrogen nitrate. For sediment samples, the surface bottom mud was collected with grabtype sediment sampler and saved in sealed bag. For organism samples,we just selected muscle of the fish and shrimp and saved different species in its own sealed bag. The above sampling processes were all in accordance with The Specification for Marine Monitoring. The water samples were processed with resolution method according to National Standard (GB/T 7457-87) and the sediment samples were also processed with resolution method according to National Standard (GB/T 17137-40 1997). The mud was treated in the following sequence: cleared off sundries, air-dried, and grinded. The homogenate of organism muscle was processed according to National Standard (GB/T5009-2003). All the processed samples were detected with flame atomic absorption spectrophotometer (Varian SpectrAA 400). Our results indicated that the cadmium concentration in water bodies ranged from 0.022 mg/L to 0.047 1 mg/L, with an average of 0.012 8 mg/L. The highest value appeared in February, while the lowest value appeared in August, with the sequence of February, May, November and August. According to the Environmental Quality Standards for Surface Water GHZBI, our results showed that water quality of the studied area was worse than Class Ⅲ water quality standards. The cadmium concentration ia sediments ranged from 5.062 mg/kg to 9.239 mg/kg, with an average of 6.974 mg/kg, which was higher than those in other estuarine areas, and showed a steady increasing trend. The cadmium concentrations in aquatic animals ranged from 0.144 mg/kg to 0.430 mg/kg, which were higher than the national limiting standard.Furthermore, the cadmium concentration in predatory fish was relatively higher than that in omnivorous fish.Compared with previous studies in Pearl River estuary, we found an apparent increasing trend for cadmium concentration in fish bodies during recent years.%对珠江河口水体、沉积物和生物体中重金属镉(Cd)的含量与分布进行调查研究,结果表明,水体中Cd含量范围在0.022～0.047 1 mg/L,并且Cd含量在时间上由高到低依次为:2月、5月、11月、8月,2月Cd含量显著高于5月、8月和11月(P＜0.05).以海水水质标准衡量,珠江河口水体2008年中大部分时间为海水二类水质.沉积物中Cd含量范围在5.062～9.239 mg/kg,平均含量为6.974 me/kg,并且沉积物中Cd含量均超过海洋沉积物3类标准.与国内外河口比较,珠江河口沉积物中Cd含量处在较高水平,污染比较严重,并且有逐年升高的趋势.生物体中Cd含量范围在0.144～0.430 mg/kg,鱼类Cd含量均超过国家水产品卫生标准,并且肉食性鱼类Cd含量略高于杂食性鱼类,但差异不显著(P＞0.05).与往年调查进行比较发现,珠江河口鱼类Cd含量2000年较1988年有大幅增加,并且2000年以后增加也比较明显.