小冶炼地区PAHs污染及其风险评价

Assessment on the contamination and risk of PAHs in a metal smelting area

采样分析了中国东部沿海某镇小冶炼地区多介质环境中 PAHs的浓度水平 ,发现小冶炼集中生产区内大气中 17种PAHs总浓度 (Σ PAHs)高达 4 170 ng/ m3,是区外大气中 Σ PAHs平均值的 6倍 ;该区内河及边境河流下游河水中 Σ PAHs平均为 8.17μg/ L ,远大于边境河流上游河水中的Σ PAHs平均值 (2 .17μg/ L ) ;表层水稻土中Σ PAHs平均为 15 2 mg/ kg,并随着土壤深度增加逐渐减少 ;水稻根、茎叶、籽实中Σ PAHs平均分别为 5 2 9μg/ kg、5 39μg/ kg、10 5μg/ kg。类比调查表明 ,小冶炼地区各环境介质中的 PAHs浓度均不同程度地高于文献报道值。估算了当地居民及冶炼工人经呼吸进入体内的 8种致癌 PAHs的量 ,分别达 5 30 ng/ d和 1138ng/ d。调查了小冶炼地区及其周围地区近 3a死亡人群的死因 ,发现该区死亡人群中病死比例和死于癌症比例平均分别达 32 .2 %和 2 5 .6 % ,均高于周围地区的相应值 (2 3.3%和 16 .0 % )

It is well known that small-scale metal smelting industry leads to heavy PAHs pollution. However, little information is available on PAHs concentrations and distribution in various environmental elements around the smelting industry and its risk to local people. A field study was performed to determine the PAHs concentrations in different environmental elements, such as air (n=6), surface water (n=5), paddy soil (n=9), and rice (n=5) in 5 villages, located in a town of the eastern China, where still existed 5 smelters aggregated zones, respectively. Sampling was carried out on November 18th 2002, when rice was ripe for harvest. 17 PAHs in each sample were simultaneously measured by HPLC. It was observed that average total 17 PAHs concentrations (ΣPAHs) in air of the studied area ranged from 550 ng/m^3 to 4170 ng/m^3, with the highest concentration of 4170 ng/m^3 detected in one of the smelters aggregated zones, which was about 6 times of the mean ΣPAHs in air out of the zones. The average ΣPAHs in surface water of the downriver (running through the west boundary of the metal smelting area) and the branch river (located in the metal smelting area), being 8170 ng/L, was about 3.8 times higher than that of the upriver. ΣPAHs in surface paddy soil ranged from 108 mg/kg to 183 mg/kg, with a mean of 152 mg/kg. In addition, although ΣPAHs in soil decreased with the increase of the soil depth, it still was 92.4 mg/kg in the depth of 70 ～100 cm, implying that the paddy soil in the studied area had been contaminated by PAHs for a long time. The average ΣPAHs in rice root, rice shoot, and rice seed reached 529 ng/g, 539 ng/g, 105 ng/g, respectively. It was evident that ΣPAHs in all environmental elements were higher than recorded data, implying that the environment in this study was heavily polluted by PAHs originated from the metal smelting industry. Local residents and workers' daily exposures to 8 carcinogenic PAHs by breath were estimated to 530 ng/d and 1138 ng/d, respectively. The rates of the death because of diseases and cancers in the five villages reached 32.2% and 25.6%, respectively, being higher than those in 25 villages around (23.3% and 16.0%). It was certain that the metal smelting activity had already imposed threat on the health of the local people.