北部湾涠洲岛海水重金属污染现状研究

Heavy Metal Pollution of Seawater in Weizhou Island,Beibu Gulf of Guangxi

随着生产的不断发展,海水中重金属污染愈加严重,明确海水重金属污染程度对海区环境资源保护和可持续发展具有重要意义。运用单因子评价法、综合污染指数法和相关性分析法对2015—2016年北部湾涠洲岛海水重金属Cu、Pb、Zn、Cd、Cr、Hg、As进行污染程度分析。结果表明,2015年涠洲岛海水重金属质量浓度高低排序为Hg<Cr<Cd<As<Pb<Cu<Zn,质量浓度范围为0.052 0~10.0μg·L^(-1);2016年为Hg<Cd<As<Cr<Cu<Pb<Zn,质量浓度范围为0.019 4~45.8μg·L^(-1)。2015—2016年整个涠洲岛海域重金属综合污染指数均属于清洁级,但2016年位于岛北面的S4和东面的S6站位综合污染指数均大于1,分别属于轻度和中度污染。重金属Pb、Zn、Hg存在超标,最高可超一类海水水质标准5.6、11.7、0.3倍。2015年涠洲岛海水重金属Cu和Cd,2016年海水重金属Zn和Hg均呈显著正相关,且2016年重金属元素间的相关性大于2015年,相关系数分别为0.757 8和0.796 7;2016年的Zn和Hg均为超标元素,人类活动可能是涠洲岛海水重金属污染的主要原因。涠洲岛As含量总体上低于广西北部湾其他海域,其余6项重金属含量整体低于沿岸工业活动、河流汇入、农业和生活污染频繁的北部湾潮间带、北海、廉州湾、钦州湾、防城港等地。总体而言,涠洲岛重金属污染程度仍属于清洁水平,个别站位偶有超标。

Heavy metal elements of Cu, Pb, Zn, Cd, Cr, Hg and As in the sediments of Weizhou Island in 2015—2016 were determined and assessed by using single factor pollution index, integrated pollution index and correlation coefficient. In 2015, the mass concentration of heavy metals showed that Hg〈Cr〈Cd〈As〈Pb〈Cu〈Zn, corresponding with 0.052 0, 0.2, 0.28, 0.521, 0.76, 1.0, 10.0 μg·L-1. In 2016, the relation was Hg〈Cd〈As〈Cr〈Cu〈Pb〈Zn with 0.019 4, 0.07, 0.406, 0.5, 1.3, 2.29, 45.8 μg·L-1, respectively. When referring the first class of seawater quality standard of China, the synthetical pollution indexes for 2015 and 2016 in Weizhou Island were both less than 1.0, which means the seawater of Weizhou Island in these two years was in clean status. However, the synthetical pollution indexes from the location of S4 and S6 at 2016 exceeded 1.0, demonstrating light and medium pollution in these sites. In addition, Mass concentrations of Pb, Zn and Hg were beyond the seawater quality standard of China and the excesses reached as high as 5.6, 11.7 and 0.3 times of the standard value, respectively. The heavy metal elements of Cu and Cd in 2015 and Zn and Hg in 2016 on Weizhou Island were positively correlated, with the correlation coefficients of 0.757 8 and 0.796 7, respectively. Heavy metal elements of Zn and Hg exceeding the standard limits were due to the anthropogenic activity in Weizhou Island. Heavy metal of As was in a general lower in Weizhou Island than in other Beibu Gulf seawaters, in contrast, heavy metal concentrations of Cu, Pb, Zn, Cd, Cr and Hg in seawater in this island were lower than those seawaters from tidal flat of Beibu Gulf, Beihai, Lianzhou Bay, Qinzhou Bay and Fangcheng. The latter areas are strongly influenced by industry, river input, agriculture and domestic pollution associated with human activity. In general, the level of heavy metal pollution of seawater in Weizhou Island is still clean, but there are individual stations beyond the standard.