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塑料由于其轻便适用等优点,已成为人类日常生活不可或缺的一部分. 随着塑料大规模的使用,其产生的废弃塑料给环境带来了很大的压力[1]. 塑料经过风化或化学降解等作用会碎裂成粒径更小的塑料颗粒[2],当其粒径<5 mm时,即被称为微塑料(microplastics, MPs)[3]. 微塑料具有粒径小和比表面积大等特点[4],许多重金属和抗生素极易吸附在其表面[5-6],给环境带来的危害更大.
为了全面评估微塑料给环境带来的生态风险,需要表征其丰度,特征及潜在来源[4]. 科学家首先在大洋中发现微塑料的踪迹[7-8],随后在近海区域也发现了微塑料的存在,Zheng等[9]调查了胶州湾表层水中微塑料,其丰度为20—120 items·m−3,发现海湾中微塑料聚合物类型与河口的微塑料聚合物类型非常匹配,认为河流输入是海湾微塑料的重要贡献者. Zheng等[10]调查了胶州湾沉积物中微塑料,其丰度为2.5—27.5 items·kg−1,进一步发现微塑料丰度在深层沉积物中非常低,并且通常从地表向下呈下降趋势. 近年来研究发现淡水环境中的微塑料污染甚至比海水中的微塑料污染更加严重[11], Lin等[12]研究发现广州沿珠江地区表层水和沉积物微塑料丰度范围分别是379—7924 items·L−1和80—9597 items·kg−1,表层水中微塑料丰度最高是在支流的汇合处,而沉积物中微塑料丰度最高点位于上游,说明微塑料丰度会受到地形,人类活动等因素影响. Ding等[4]调查了渭河表层水和沉积物中的微塑料,其丰度分别为3.7—10.7 items·L−1和360—1320 items·kg−1,并进一步发现低水流和高含砂率会导致微塑料的积累和分布. 近年来国内对于微塑料的淡水研究集中在珠江[12]和渭河[4]等大型河流,大型河流支流较多,在进行微塑料来源探究时较困难. 而目前国内对于中小型河流研究较少,小型河流污染源单一,并且流经城市的中小型河流的沉积物可能是微塑料的初始汇,对其进行研究可以探究微塑料的来源,并可进一步了解城市中塑料污染状况.
大沽河位于胶东半岛,是青岛最大的河流,近年来受垃圾污染和污水排放等因素影响,河流水质退化,陆海生态连通性消失等问题接连出现. 本文以大沽河为例,在流域内不同功能区进行采样,探究其表层水和沉积物中微塑料的污染特征以及微塑料在相邻介质间的迁移,建立微塑料变量相关性模型,探寻微塑料各变量在相关功能区中可能的相关性,进一步分析各功能区中最常出现的微塑料,进而溯源塑料垃圾,为中小型河流微塑料分布特征及污染现状提供数据支持,并为大沽河流域生态环境治理提供了参考.
大沽河流域微塑料在不同介质中的空间分布及其潜在来源探究
Spatial distribution and potential sources of microplastics in different media of Dagu River basin
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摘要: 微塑料作为一种新型污染物已对环境健康构成了严重威胁. 为调查微塑料在城市河流不同介质中的污染特征及其迁移规律,并基于城市中不同功能区的划分探究微塑料的潜在来源,以青岛大沽河为例,在2020年6月对表层水和沉积物进行取样分析. 结果表明,大沽河表层水和沉积物中微塑料丰度 分别为0.6—3.8 items·L−1和60—480 items·kg−1,表层水体中大粒径微塑料(>3 mm)占比最多,为28.95%,而沉积物中小粒径微塑料(0.5—1 mm)占比最多,为40.48%;大沽河微塑料颜色以深色系为主(黑色、蓝色和红色),形状主要是纤维状,材质主要是人造丝、聚对苯二甲酸乙二醇酯和聚乙烯;表层水和沉积物中,微塑料丰度之间并无相关性,但微塑料在流域空间分布上存在迁移转化过程,并发现沉积物是城市河流微塑料的初始汇. 通过多重对应分析技术对大沽河流域不同功能区微塑料的颜色、粒径、聚合物成分和形状四个变量建立相关性模型,可以进一步溯源微塑料的源头。结果表明,无论水体还是沉积物,微塑料的来源因区域不同存在差异,但同一区域水体和沉积物中来源类似,具有受本地输入影响的明显特征.Abstract: As a new type of pollutant, microplastics(MPs)pose a serious threat to environmental health. To investigate the pollution characteristics and migration of MPs in different media of urban rivers, and to explore the potential sources of MPs in different functional areas, the surface water and sediment samples of Dagu River in Qingdao area were collected in June 2021 and analyzed for MPs . The results showed that the average abundance of MPs in surface water and sediment of Dagu River was 0.6—3.8 items·L−1 and 60—480 items·kg−1, respectively. Microplastics with large particle size (>3 mm) accounted for the most in surface water (28.95%), while MPs with smaller particle size (0.5—1 mm) accounted for the most in sediment (40.48%). In Dagu River, MPs were predominantly dark (black, blue and red) in color, and the polymer types were mainly rayon, polyethylene terephthalate and polyethylene, with fibers being the most frequently detected shape of MPs. There was no correlation between the abundance of MPs in surface water and that in sediment. However, a spatial migration was evident, as revealed in the distribution of MPs. It was found that sediment might be the initial sink of MPs in urban rivers. To further trace the sources of MPs in Dagu river basin, a correlation model was established according to multiple correspondence analysis based on the characteristics of MPs, namely, the color, particle size, polymer composition and shape of MPs in different functional areas. The results showed that the sources of MPs variated depending on the functional areas of the region, no matter in water or in sediment. However, the sources of MPs in water were similar to those in sediment. This is an apparent indication that MPs in the basin was influenced by local inputs.
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Key words:
- microplastics /
- spatial distribution /
- sources /
- correlation model /
- Dagu River
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