知识与财富的链接
为了解电子废物不当处置活动对小流域内水体沉积物金属污染的影响,采集了位于广东省清远市龙塘镇和石角镇的电子废物焚烧和酸解活动核心区内水塘和水库的0～40cm沉积物以及附近河流大燕河表层(0～5cm)沉积物样本,分析了样本中的金属(水塘、水库:Zn、Cu、Pb、Cd、Cr;大燕河:Zn、Cu、Pb、Cd、Cr、Ni、Mg、Mn)含量.作为对照,对珠江口伶仃洋沉积物中的5种重金属(Zn、Cu、Pb、Cd、Cr)含量也进行了分析.结果表明,1)在核心区内,5种重金属的平均含量在接近酸解作坊的水塘沉积物中呈Cu(766.16mg·kg-1)>Zn(181.12mg·kg-1)>Pb(129.56mg·kg-1)>Cr(1.89mg·kg-1)≈Cd(1.12mg·kg-1),在其下游的水库沉积物中呈现相同的规律,但水塘沉积物的Cu、Zn、Pb含量均高于水库.水塘、水库沉积物重金属含量分布规律明显不同于伶仃洋沉积物,与伶仃洋沉积物相比,核心区水体沉积物Cu含量特别高,是伶仃洋沉积物的7～17倍,Pb和Cd则分别是伶仃洋的2.3～3.0倍和1.9～2.4倍,Zn、Cr含量与伶仃洋沉积物相近.2)Zn含量在核心区水体沉积物中均呈现出在20.0～30.0cm深度最高的趋势,Cu、Pb含量在水库沉积物中也有类似的表现,说明该深度的沉积物可能是电子废物回收处置活动最频繁的时期形成的,近年来随着政府取缔工作的加强,电子废物非法处置活动的减少,Zn、Cu、Pb含量有明显的下降.3)大燕河沉积物中6种重金属(Zn、Cu、Pb、Cr、Cd、Ni)的总含量表现为中游下段(1261.3mg·kg-1)>中游中段(1049.2mg·kg-1)>中游上段(401.8mg·kg-1)>上游(364.6mg·kg-1)>下游(215.4mg·kg-1).Cu、Zn、Pb和Cr含量均在中游下段的沉积物中出现最大值,次大值出现在中游中段,Ni、Cd在中游中段出现最大值,次大值出现在中游下段.中游中、下段沉积物中金属含量最大值和其上游(或中游上段)河段含量最低值的比值呈现Cu(10.1)>Cr(7.8)>Zn(3.8)>Cd(2.0)>Pb(1.9)>Ni(1.8),显示这些重金属主要从中游中、下段进入大燕河沉积物,其中Cu污染最为严重,而Cr污染可能与水土流失或当地其他活动释放的Cr有关.4)比较流域内土壤和各种沉积物以及伶仃洋沉积物中重金属的构成比例发现,核心区土壤和沉积物以及大燕河沉积物中的重金属具有明显的同源性.随着离源区距离的增加,重金属的构成比例中最明显的变化是Cu的比例下降以及Zn的比例上升。
In order to investigate metal contaminations to sediments by E-waste treating activities in a small scale valley located in Longtang Town and Shijiao Town, Guangdong, China, 0～40cm sediment samples of a pool and a small dam within the E-waste acid-treating and open-burning area, and surface sediments(0～5cm) of upstream, midstream and downstream of Dayan River crossing over the area were collected. Concentrations of metals in the samples(Zn, Cu, Pb, Cd and Cr for the sediments of the pool and the small dam; Zn, Cu, Pb, Cd, Cr, Ni, Mn and Mg for the sediments of the Dayan River) were analyzed. Concentrations of Zn, Cu, Pb, Cd and Cr in a 0～40cm sediment collected from Lingdingyang, one of the estuaries of the Pearl River, were also analyzed for comparing. It was found that, 1) average concentrations of Zn, Cu, Pb, Cd and Cr in the 0～40cm pool sediment were in order of Cu (766.16mg·kg-1)>Zn (181.12mg·kg-1)>Pb (129.56mg·kg-1)>Cr (1.89mg·kg-1)≈Cd(1.12mg·kg-1), and the concentrations in the 0～40cm sediment of the small dam located in lower reaches of the pool had the same trend but with much lower Zn, Cu and Pb concentrations than the pool. Profile of the heavy metal concentrations in the 0～40cm Lingdingyang sediment was obviously different. Cu, Pb and Cd concentrations in the pool and the small dam sediments were 7.0～17.0, 2.3～3.0 and 1.9～2.4 folds of those in the Lingdingyang sediment. Zn and Cr concentrations in the pool and small dam sediments were similar to the Lingdingyang sediment. 2) The highest concentrations of Zn in both the pool and the small dam sediments were observed in 20.0～30.0cm depth, and similar vertical distributions of Cu and Pb in the small dam sediment were observed. The results indicates that the sediment in the depth may be accumulated in the period when the metal contamination by the E-waste treating activities was mostly serious, and the decreased heavy metal accumulation in surface layer of the sediments can be likely attributed to the clampdown actions performed by the local government to the activities. 3) The highest total concentrations of Zn, Cu, Pb, Cr, Cd and Ni in the sediments of Dayan River were observed in rearward of the midstream(MS3, 1261.3mg·kg-1), followed by central section of the midstream(MS2, 1049.2mg·kg-1), foreside of the midstream(MS1, 401.8mg·kg-1), the upstream(US, 364.6mg·kg-1) and the downstream(DS, 215.4mg·kg-1). The highest concentrations of Cu, Zn, Pb and Cr appeared in the MS3, followed by the MS2, while the maxima of Ni and Cd were in the MS2, followed by the MS3. The highest concentrations of Zn, Cu, Pb, Cd, Cr and Ni in the sediments of the MS2 and MS3 were 3.8, 10.1, 1.9, 2.0, 7.8 and 1.8 folds of the minimal concentrations of the metals in US and the DS. Therefore, the MS3 and MS2 were the main entries of the metals flowing into the Dayan River. Cu was the mostly important sediment contaminant coming from the E-waste treating activities. 4) When comparing the proportions of the individual heavy metals in the soil and the tested sediments, it was found that the heavy metals in the soil and the sediments within the E-waste treating area had obviously similar origin, and the most characterized changes accompanying with transferring of the metals were the increase of the Cu proportion and the decrease of the Zn proportion with the increase of distance to origin area.
