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自塑料问世以来,由于其稳定性、轻便性以及较低的价格,经过多年的发展,塑料已经成为生活中不可或缺的一部分. 在已经生产的塑料制品中,约50%是一次性使用的,只有20%至25%的塑料可以长期使用[1]. 尽管存在回收的潜力,但是考虑到经济成本,绝大多数(约92%)的塑料最终在废弃后被填埋或遗弃在自然环境中[1-2]. 近年来,有研究表明海洋已经成为了塑料最大的聚集地,每年有大量的塑料垃圾通过各种途径进入海洋并在海洋环境中累积[3]. 这些塑料垃圾在经历磨损、紫外线作用、微生物降解等过程后,会进一步形成微塑料. 当微塑料进入海洋环境后,容易被浮游生物、鱼类以及哺乳动物等多种海洋生物摄食,对生物体造成物理损伤并抑制生长. 除此之外,微塑料在环境中容易成为其它污染物的载体,如重金属、持久性有机污染物等[4-6],以及微塑料本身在生产过程中添加的增塑剂等. 在微塑料被摄食后,这些污染物可能会随着食物网传递,对生态系统造成不利影响,并可能由于食用海鲜等最终暴露于人体.
除了水体之外,海洋沉积物也被认为是海洋微塑料重要的汇. 漂浮在水体中的微塑料可能在多种因素的作用下发生沉降,水动力、生物摄食以及微生物作用等是影响微塑料下沉速率的主要因素[7]. 微塑料颗粒物表面生物膜的附着和颗粒物间的聚集也会进一步影响微塑料的沉降性能[8]. 有研究发现西班牙地中海沉积物中的微塑料丰度高达900 n·kg−1(干重)[9]. 北太平洋沉积物也发现了一定程度的微塑料[10],表明微塑料可以通过潮流运输到偏远地区,突出了塑料碎片的全球分布. 海洋中微塑料的来源多样,主要包括陆源输入、河流输入、污水排放、海上旅游活动及海洋渔业活动等[11].
目前,关于中国近海养殖海区中微塑料污染的报道较少,茅尾海是一个半封闭式内海,受河流影响较大,同时,茅尾海是一个典型的海水养殖区,长期的渔业养殖活动以及入海河流等为茅尾海带来了一系列的污染问题[12-14],海域内的微塑料污染问题比较明显. 因此本研究通过调查茅尾海水体、沉积物中存在的微塑料的数量、颜色、粒径和类型,了解微塑料在该海域的分布特征,并结合风险评估模型对茅尾海的微塑料污染风险进行初步的评估. 以期科学认识中国近海养殖海区茅尾海的微塑料污染特征,为养殖海域确定其潜在的生态风险提供参考.
水体及沉积物微塑料污染对近海养殖海区的生态风险
Study on the ecological risk of water and sediment microplastic pollution on offshore marine aquaculture areas
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摘要: 微塑料在全球海洋水体及沉积物中广泛存在,然而关于近海养殖海区的微塑料污染特征鲜有报道,本研究调查了中国近海养殖海区茅尾海水体和沉积物中微塑料的分布特征并初步对其微塑料污染进行风险评估. 结果表明,茅尾海区域广泛分布着微塑料,茅尾海水体中微塑料的平均丰度为(2.01±1.23) n·m−3,泡沫(60.1%)是主要的类型. 沉积物中的微塑料平均丰度为(22.4±19.6)n·kg−1,薄片(50%—100%)在采样点中占主要部分. 茅尾海水体、沉积物中的微塑料粒径都以1—5 mm为主(33.3%—100%),水体和沉积物中的微塑料主要来自钦江的输入、旅游活动以及海水养殖活动. 通过风险评估模型初步得出,茅尾海区域微塑料的污染水平属于中等偏低水平,水体中微塑料整体污染风险等级显著高于沉积物,生态风险等级分别属于Ⅲ级(较高风险)和Ⅱ级(较低风险). 风险指数最高的点位于茅尾海入海河流钦江入海处,达到了Ⅳ级(高风险),各沉积物采样点的风险等级主要集中在Ⅰ—Ⅱ级,属于较低风险. 危害评分高的聚合物聚丙烯腈(Polyacrylonitrile,PAN)是水体中微塑料污染风险的重要来源.Abstract: Microplastics are widely present in marine waters and sediments worldwide, However, the pollution characteristics of microplastics in offshore aquaculture areas are rarely reported. In this study, the distribution characteristics of microplastics in seawater and sediments in offshore aquaculture areas of Maowei Sea were investigated. Furthermore, a preliminary risk assessment of microplastic pollution was conducted. The results showed that microplastics were widely distributed in the Maowei Sea. The average abundance of microplastics in Maowei Sea was (2.01±1.23) n·m−3. Foam (60.1%) was the dominant type. The average abundance of microplastics in sediments was (22.4±19.6) n·kg−1. Sheet (50%—100%) were the main part in the sampling sites. The particle size of microplastics in seawater and sediment of Maowei Sea is 1—5 mm(33.3%—100%). It was found that the microplastics in the seawater and sediments were mainly from the input of Qinjiang River, tourism activities, and mariculture activities. According to the risk assessment model, the pollution level of microplastics in Maowei Sea is medium to low level. The overall pollution risk level of microplastics in water was significantly higher than that in sediments, belonging to grade Ⅲ(slightly higher risk) and Ⅱ(slightly low risk) respectively. The highest risk index is located in the Maowei Sea into the sea river Qinjiang River into the sea, reached Ⅳ level(high risk), Risk level of each sediment sampling point are mainly concentrated in Ⅰ—Ⅱ level, belongs to low risk. Polymer polyacrylonitrile (PAN) with high hazard score is an important source of microplastic pollution risk in water.
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Key words:
- Maowei Sea /
- microplastics /
- distribution characteristics /
- ecological risk
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表 1 中国近海养殖海区茅尾海微塑料聚合物的详细信息
Table 1. Detailed information of microplastic polymers in Maowei Sea of China offshore aquaculture area
聚合物
Polymer英文缩写
English abbreviations单体
Monocase密度/(g·cm−3)
Density危害评分
Hazard rating聚乙烯 PE Ethylene 0.89—0.98 11 聚丙烯 PP Propylene 0.85—0.92 1 聚对苯二甲酸乙二醇酯 PET Ethylene glycol 1.38—1.41 4 聚苯乙烯 PS Styrene 1.04—1.1 30 聚丙烯腈 PAN Acrylonitrile 1.184 11521 表 2 茅尾海中微塑料污染风险指数和风险等级
Table 2. Risk index and risk grade of microplastics pollution in Maowei Sea
微塑料污染风险指数
Microplastic pollution risk index风险等级
Risk level采样点
Sampling points<10 Ⅰ S2、S3、A2、A4、A5、A8、A10、A18 10—100 Ⅱ A1、A3、A6、A7、A9、A11、A12、A13、A14、A15、A16、A17、A19、A20、A21 101—1000 Ⅲ S4、S5 1001—10000 Ⅳ S1 -
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