茅洲河沉积物重金属分布特征及生态风险评价

发布时间：2018-08-01 11:51

【摘要】：重金属污染来源广、毒性强,越来越受到国内外专家、学者的关注。而河流沉积物是水体重金属的主要富集场所,对河流沉积物重金属含量及生态风险的评价可以在一定程度上为水体污染现状了解和污染治理提供依据。本论文以深圳市第一大河——茅洲河上游、下游和沙井河支流为研究区域,布设采样点位71个,在沉积物深度0-400 cm范围根据物理性状的一致性和差异性分段切割,经风干、研磨、过筛及消解预处理,利用电感耦合等离子体质谱(ICP-MS)仪测定重金属含量分析重金属在流域内的分布特征并进行生态风险评价和相关性解析。得到的结论如下:(1)全流域重金属含量排序为CuZnCrNiPbCd,其中重金属Cu平均含量高达809.17 mg·kg-1,是广东省土壤环境背景值的101倍。重金属含量在深度上的分布主要集中在表层0-100 cm的范围内,总体趋势为深度越深含量越低,表明茅洲河沿岸重金属污染呈逐年加剧的趋势。重金属含量在不同分区上的分布情况大致为沙井河支流下游上游,总体来看沙井河污染最为严重,下游次之,上游相对较轻。(2)各重金属污染高值区主要集中在交汇口附近,其中Cr、Ni、Cu、Zn、Pb五种重金属均分布在自干、支流交汇处开始的茅洲河下游段上,重金属Cd的高值区污染带则分布在交汇口上方的上游段和沙井河支流段上。(3)入海口断面点位深度到达50-100 cm时各种金属含量变化基本趋于稳定,不会有急剧增加和降低,且越接近入海口的断面表层沉积物含量相对越高。对比同一断面河流两侧的重金属含量,河西岸明显高于河东岸,说明茅洲河受东莞工业污染影响高于深圳影响。(4)利用四种方法对茅洲河沉积物重金属进行生态风险评价,评估结果表明,Cu生态风险最大,Cr、Pb都位列六种重金属中的第五位和末位。除运用Tomlinson污染负荷指数法生态风险Zn大于Ni,其余三种计算方法均为Ni大于Zn。从地累积指数法结果看,重金属Cd虽然含量不及其他重金属高,但其生态毒性较大,较低浓度能造成较大的生态危害。(5)茅洲河流域内重金属之间存在极强相关性或较强相关性,流域内沉积物重金属可能具有相似的来源或沉积转化过程,来源主要可能为人为排污或生产活动含重金属废弃物的排放。不同环境因子与沉积物重金属在0.01水平上存在正相关性,重金属和总磷相关性最显著,在冗余分析中解释了13.1%的重金属含量变化,其次为有机质(TC)、TN和含水率。粒径小于250μm时与重金属相关性最好,此粒度范围内更容易吸附重金属Cr、Zn、Cd。
[Abstract]:Heavy metal pollution has been paid more and more attention by domestic and foreign experts and scholars because of its wide sources and strong toxicity. The river sediment is the main accumulation place of heavy metals in water body. The evaluation of heavy metal content and ecological risk of river sediment can provide the basis for the understanding of water pollution status and pollution control to a certain extent. Taking the upper, lower reaches and tributaries of Shajing River as the study area, 71 sampling sites were set up in this paper. The sampling sites were cut in the depth of 0-400 cm according to the consistency and difference of physical properties, and then dried by air. After grinding, sifting and digestion pretreatment, the distribution characteristics of heavy metals in the basin were analyzed by inductively coupled plasma mass spectrometry (ICP-MS), and the ecological risk assessment and correlation analysis were carried out. The conclusions are as follows: (1) the order of heavy metal content in the whole basin is CuZnCrNiPbCd2.The average content of heavy metal Cu is 809.17 mg 路kg ~ (-1), which is 101-fold of the background value of soil environment in Guangdong Province. The distribution of heavy metals in depth was mainly in the range of 0-100 cm in the surface layer, and the general trend was that the deeper the depth was, the lower the content of heavy metals was, which indicated that the pollution of heavy metals along the Maozhou River was increasing year by year. The distribution of heavy metal content in different zones is roughly upper reaches of tributaries of Shajing River. Generally speaking, the pollution of sand well river is the most serious, followed by the lower reaches, and the upper reaches are relatively light. (2) the high value areas of heavy metal pollution are mainly located near the junction. Among them, five heavy metals, Cr-NiNiCuZZn-Pb, are distributed in the lower reaches of Maozhou River, where the confluence of the main and tributaries begins. The pollution zone of heavy metal CD in high value area is distributed in the upstream section above the junction and in the tributary section of Shajing River. (3) when the depth of the cross section reaches 50-100 cm, the variation of various metal contents tends to be stable, and there will be no sharp increase or decrease. The higher the surface sediment content is, the closer it is to the mouth of the sea. Comparing the contents of heavy metals on both sides of the same section of the river, the west bank of the river is obviously higher than that of the east bank of the river, which indicates that the effect of industrial pollution on the Maozhou River is higher than that of Shenzhen. (4) the ecological risk assessment of heavy metals in the sediment of Maozhou River is carried out by four methods. The results show that the ecological risk of Cu is the highest, and Cr-Pb is the fifth and last of the six heavy metals. Except that the ecological risk Zn of Tomlinson pollution load index is greater than that of Ni, the other three calculation methods are Ni > Zn. According to the results of soil accumulation index method, although CD content is not as high as other heavy metals, its ecotoxicity is higher, and lower concentration can cause great ecological harm. (5) there is a strong correlation or a strong correlation between heavy metals in Maozhou River Basin. The sediment heavy metals in the basin may have similar sources or processes of sedimentary transformation, and the main sources may be the discharge of heavy metal wastes from sewage or production activities. There was a positive correlation between different environmental factors and sediment heavy metals at 0.01 level, and the correlation between heavy metals and total phosphorus was the most significant. The variation of heavy metals content was explained by 13.1% in redundancy analysis, followed by organic matter (TC) TN and water content. When the particle size is less than 250 渭 m, the correlation with heavy metals is the best, and it is easier to adsorb the heavy metal Cr ~ (2 +) Zn ~ (2 +) CD in this range.
【学位授予单位】：山东农业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X522;X826

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