湛江特呈岛红树林湿地土壤重金属含量特征及污染评价

摘要

近年来,随着沿海地区工业化和城市化的进程加快,人类活动产生的大量污染物汇集于河口和海湾地区,使得红树林湿地土壤污染日益严重.特呈岛红树林是中国古老的红树林古树群,由于养殖业发展、旅游开发等人类活动的加强,该地湿地土壤遭受了不同程度的影响.为了探讨特呈岛红树林湿地表层土壤重金属的污染特征,于2015年7月沿特呈岛南岸自西向东采集12个表层土壤样品,经过实验室处理和测试,分析砷(As)、镉(Cd)、钴(Co)、铬(Cr)、铜(Cu)、汞(Hg)、锰(Mn)、镍(Ni)、铅(Pb)、钒(V)、锌(Zn)等11种重金属的含量特征;并采用潜在生态风险指数法进行污染评价.结果表明:(1)特呈岛红树林湿地表层土壤11种主要重金属元素的含量平均值均未超过国家土壤环境质量一级标准限值;(2) Cd、As、Co、Cu、Zn等5种重金属元素的平均值均超过了环境背景值,其中Cd含量平均值是环境背景值的1.76倍;其次,As和Co含量平均值分别为环境背景值的1.39倍和1.37倍;(3)特呈岛红树林湿地表层土壤潜在生态风险总体上属于轻微-中等污染;其中,潜在生态风险较大的元素是Hg和Cd,属于中等污染;其他9种重金属元素属于轻微污染;(4)从空间分布看,TCD3和TCD10等8个样点属于中等污染,TCD12和TCD4等4个样点为轻微污染;(5)土壤重金属污染主要来自特呈岛居民和游客生活污水排放、农业化肥农药的使用和渔民船舶涂料脱落,但具体成因仍有待进一步研究.%In recent years,as the process of industrialization and urbanization in coastal areas are speeding up,a large number of pollutants produced by human activities are found in estuaries and bays,making the soil pollution of mangrove wetland become increasingly serious.Being known as the oldest and most beautiful ancient mangrove floral in China,the Techeng Island mangrove wetland has actually suffered from varying degrees of influence due to the intensification of human activities like aquaculture development,tourism development and so on.In order to research the pollution features of heavy metals in surface soils of Techeng mangrove wetland,12 surface sediment samples were collected along the south bank of Techeng Island from west to east in July 2015.Based on pretreatment and laboratory test,the characteristics of 11 kinds of heavy metals were analyzed;and the potential ecological risk index method was used to evaluate the level of pollution.The results are as follows:(1) The average concentrations of 11 major heavy metal elements in the surface sediment did not exceed the National soil environment quality level standard;(2) The average concentrations of Cd,As,Co,Cu and Zn had exceeded the environment background value;among them,the average concentration of Cd element was1.76 times of the environment background value;Followed by the average concentration of As and Co wasl.39 and 1.37 times respectively of the environment background value;(3) In general,the potential ecological risk of surface sediment in Techeng Island mangrove wetland was mild-moderate pollution.Among them,the Hg and Cd element got higher potential risk,belong to the medium pollution;and the other 9 kinds of heavy metal elements belong to the slight pollution;(4) From the spatial distribution,8 samples,such as TCD3 and TCD10,belong to the medium pollution;the other 4 samples,like TCD12 and TCD4,belong to the slightly pollution.And (5) the heavy metal pollution in the surface sediment mainly resulted from the discharge of domestic sewage,the use of agricultural chemical fertilizer and the fishermen ship paint off,and this caused by the residents and tourists of Techeng Island,but this still needs further study.