环境科学  2024, Vol. 45 Issue (12): 7253-7261   PDF    
塑料中高关注物质(SVHCs)的赋存分布、物质流及环境释放研究进展
刘俊宙1, 陈嘉喆1, 景侨楠1, 张少轩1, 陈安娜1, 陆蓉静1, 刘建国1,2     
1. 北京大学环境科学与工程学院,环境模拟与污染控制国家重点联合实验室,北京 100871;
2. 北京大学碳中和研究院,北京 100871
摘要: 各类塑料制品中广泛分布的塑料添加剂赋予塑料以阻燃、增塑和抗氧化等优异功能, 但其中已有100多种因其潜在的环境和健康危害性被列入欧盟高关注物质(SVHCs)候选清单.以上SVHCs普遍分布在各类塑料及各行业产品中, 比较集中分布在PVC和PUR等类塑料和包装、汽车、建材、电子电器和纺织等行业中.在不同功能的SVHCs中, 增塑剂和阻燃剂用量最高, 品类相对集中, 一直是国内外化学品风险评估和风险管理关注的重点.现有研究已建立起塑料制品中SVHCs物质流分析方法, 揭示出PBDEs、HBCD和PAEs等典型阻燃剂和增塑剂类SVHCs在塑料制品全生命周期普遍存在的环境和健康风险;大量SVHCs随塑料产品寿命终结进入废物阶段, 揭示了各类含SVHCs塑料废物环境无害化管理的重要性.除在产品使用周期发生的环境释放外, 各种形式的塑料释放所产生的塑料碎片, 构成了环境中各种SVHCs的长期释放源, 对生态环境和人体健康造成持久威胁.未来亟需重视各类塑料制品中大量潜在有害化学品的识别及其全生命周期环境释放与风险评估研究, 尤其包括塑料中有害化学品排放系数测算、动态物质流分析方法的优化, 以及塑料释放途径有害化学品释放机制研究等.
关键词: 塑料中化学品      高关注物质(SVHCs)      赋存与分布      物质流分析(MFA)      环境释放     
Progress in the Study of Occurrence, Distribution, Material Flows, and Environmental Release of Substances of Very High Concern (SVHCs) in Plastics
LIU Jun-zhou1 , CHEN Jia-zhe1 , JING Qiao-nan1 , ZHANG Shao-xuan1 , CHEN An-na1 , LU Rong-jing1 , LIU Jian-guo1,2     
1. State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing 100871, China;
2. Institute of Carbon Neutrality, Peking University, Beijing 100871, China
Abstract: Plastic additives provide plastics with excellent functions such as plasticizing, flame retardant, and antioxidant properties and are widely used in various plastics. Of these, 189 plastic additives have been included in the European Union's Candidate List of substances of very high concern (SVHCs) due to their potential environmental and health risks. These SVHCs are mainly used in PVC, PUR, and PE plastics and in the packaging, automotive, construction, electronic and electrical equipment, and textile sectors. Plasticizers and flame retardants are the most widely used and therefore the focus of SVHC risk assessment and risk management. Existing studies have carried out material flow analysis (MFA) for SVHCs in plastics, revealing the environmental and health risks of typical flame retardants and plasticizers throughout the product life cycle, such as polybrominated diphenyl ethers (PBDEs), hexabromocyclododecane (HBCD), and phthalic acid esters (PAEs). A large amount of SVHCs enter waste streams at the end of the product life cycle, highlighting the importance of strengthening waste management for SVHCs risk management. In addition to the release of SVHCs from plastic products into the environment, plastic leakage is another important source of environmental release of SVHCs. Plastic debris that have been in the environment for a long time continue to release SVHCs and pose a long-term threat to the ecosystem and human health. In the future potentially hazardous chemicals must be crucially identified in different types of plastics and to assess their environmental release during their life cycle, in particular by establishing a database on hazardous chemicals in plastics and measuring emission factors, optimizing dynamic material flow analysis (d-MFA), as well as studying the release mechanisms of hazardous chemicals from plastic leakage.
Key words: chemicals in plastics      substances of very high concern (SVHCs)      occurrence and distribution      material flow analysis (MFA)      environmental release     

塑料因其优越的功能性和低廉的成本, 已成为现代生产生活中的核心材料, 被广泛应用在包装、建材和电子电器等领域[1].在过去的半个多世纪中, 全球塑料产量不断增长, 从1950年的200万t迅速增长至2022年的4.3亿t[2].然而, 由于塑料部门线性经济的生产使用方式, 历史上生产的所有塑料中只有不到8%得到回收利用[3], 大量管理不善的塑料释放到环境中, 引发社会各界对塑料污染问题的广泛关注.目前, 围绕塑料物质流构建[4~7]、塑料释放评估[8~12]以及海洋[13~17]、内陆水域[18~20]和土壤[21, 22]等介质中塑料碎片(plastic debris)的监测已开展了大量研究.为应对塑料污染问题, 从源头上改变塑料部门的传统模式, 发展塑料循环经济已成为国际共识及塑料行业的发展趋势[23~26].

与塑料大量生产使用相对应的是近万种化学品在各类塑料制品中的广泛分布[25, 27].以上化学品主要是各种塑料添加剂, 它们大多以非键合的方式存在于塑料基体中[28, 29], 离开塑料制品释放进入环境.按照当前塑料生产使用保持增加的趋势, 到2050年全球塑料添加剂的累计产量将达到20亿t[3].现有各类塑料添加剂中包含有多种具PBT(persistence, bioaccumulation, and toxicity)、vPvB(very persistence, very bioaccumulation)、PMT(persistent, mobile, and toxic)、vPvM(very persistent, very mobile)和CMR(carcinogenic, mutagenic or reproductive toxicant)属性或内分泌干扰效应等潜在危害特性的化学品, 被欧盟列入高关注物质(substances of very high concern, SVHCs)候选清单.以上化学品在塑料生命周期各阶段释放进入环境, 发生远距离输送和长期累积, 带来环境和健康风险[30~32].

在当前发展塑料循环经济、扩大塑料回收再生的背景下, 揭示塑料中化学品赋存与分布面临更为复杂的挑战.塑料中的化学品往往通过机械回收等过程重新进入塑料制品和塑料流中.例如, 报废电子电气设备(waste electrical and electronic equipment, WEEE)中多溴联苯醚(polybrominated diphenyl ethers, PBDEs)阻燃剂有22%经回收进入塑料[33], 而一些本已淘汰的PBDEs也在玩具、厨具和食品材料中被检出[34].塑料中的有害化学品对塑料的循环再生构成了阻碍, 并引起全球环境和健康风险.随着塑料生产使用的快速增加及塑料循环再生的扩大, 塑料中的有害化学品在塑料制品中的赋存分布及其构成的环境和健康风险亟需得到更多关注.针对这一问题, 本文通过综述当前有关塑料中SVHCs的赋存分布、物质流和环境释放研究进展, 分析当前在此领域存在的知识与行动差距及未来研究需求.

1 塑料中的SVHCs的赋存与分布状况 1.1 塑料中的SVHCs的种类和用途

塑料的主要类型包括:聚乙烯(polyethylene, PE)、聚丙烯(polypropylene, PP)、聚氯乙烯(polyvinyl chloride, PVC)、聚对苯二甲酸乙二醇酯(polyethylene glycol terephthalate, PET)、聚苯乙烯(polystyrene, PS)、聚碳酸酯(polycarbonate, PC)、聚酰胺(polyamide, PA)、聚氨酯(polyurethane, PUR)和ABS(acrylonitrile-butadine-styrene)等.2018年, 中国消费量最大的塑料类型依次是PET(28.8%)、PE(18.9%)、PP(18.9%)、PVC(11.8%)、PS(9%)和ABS(6%);从用途分布来看, 塑料主要用于包装(26.6%)、纺织(18.9%)、家庭用品(17.4%)、建材(11.9%)和农业(8%)等行业[7].

为满足不同塑料制品的加工工艺和性能要求, 多种化学品添加剂在塑料制品的生产加工阶段被有意添加到塑料制品当中, 以上化学品根据其在塑料制品中发挥的功能可分为抗氧化剂、稳定剂、增塑剂、阻燃剂、着色剂、填料和抗菌剂等类别.基于各国塑料中化学品调查及管控名录及行业数据库, Aurisano等[25]和Wiesinger等[27]初步构建起塑料中的化学品数据库, 提供了化学品的功能、塑料类别和应用行业等基础信息.对照欧盟现有SVHCs候选清单, 在Wiesinger等[27]给出塑料中化学品清单内, 有189种被列为SVHCs.本文对以上SVHCs的主要功能及典型添加水平进行检索和梳理, 结果如表 1所示.在塑料中应用的SVHCs中, 被用作着色剂、稳定剂、填料和增塑剂的SVHCs种类最多, 分别为107、59、44和42种.其中, 增塑剂和阻燃剂的典型添加水平最高, 分别为10%~70%和2%~28%.现有统计表明, 增塑剂和阻燃剂是目前全球应用量最大的塑料添加剂, 二者总用量占到了全球添加剂份额的50%以上[3].

表 1 塑料添加剂中的SVHCs种类及其典型添加水平 Table 1 Types of SVHCs in plastic additives and their typical concentrations

1.2 SVHCs在不同类型塑料中的分布

本文对当前识别的189种塑料中的SVHCs按照塑料类别及添加剂功能进行统计分析[3, 27], 得到分布结果如图 1所示.从总体上看, 各种类型的塑料中均应用到40种以上SVHCs, 说明各类塑料制品均存在一定的潜在化学品环境和健康风险.其中, PVC中应用的SVHCs的种类最多, 达到103种, 是潜在化学品环境和健康风险最集中的塑料类型;PUR和PE所应用的SVHCs种类次之, 分别为85种和75种;PP、PS、PET、PC和PA等其他类别塑料应用的SVHCs种类基本相当, 为46~62种;ABS中所应用的SHVCs种类相对略少.从各种功能的含SVHCs塑料添加剂在各类塑料的应用分布上看, 各类别塑料中普遍应用到不同功能的含SVHCs塑料添加剂, 进一步说明了各类塑料中潜在化学品环境和健康风险的普遍存在.其中, 塑料着色剂、稳定剂和填料中的SVHCs种类最多, 分别达到30~70、19~44和15~42种;增塑剂中的SVHCs种类也较多, 为13~31种, 并主要集中在PVC和PUR两类塑料, 分别达29种和27种;抗氧化剂、抗菌剂中的SVHCs种类也分别多达10~30种和4~20种;相比于其他功能的塑料添加剂, 阻燃剂中的SVHCs种类相对集中, 为6~14种, 但在各类塑料中仍普遍存在.

图 1 各类别塑料中SVHCs的分布 Fig. 1 Distribution of SVHCs in plastics of different types

从各类塑料添加剂在不同种类塑料中的分布状况看, PVC和PUR是着色剂、稳定剂、增塑剂、阻燃剂和抗氧化剂等各功能含SVHCs塑料添加剂分布最多的塑料类别;PP应用的填料和抗菌剂, PE、PC、PET和PA应用的着色剂、稳定剂和抗氧化剂, 均含有较多种类的SVHCs.在塑料中应用的各种SVHCs中, 阻燃剂和增塑剂具有普遍较高的添加量且相对集中的添加剂品类.其中, 四溴双酚A(tetrabromobisphenol A, TBBPA)、PBDEs和六溴环十二烷(hexabromocyclododecane, HBCD)是最主要的溴化阻燃剂(brominated flame retardants, BFRs), 约占全球BFRs市场份额的2/3[36], 邻苯二甲酸酯(phthalic acid esters, PAEs)是最主要的塑料增塑剂[37], 以上化学品目前均已被列为SVHCs, 是迄今塑料中有害化学品研究和管理中广泛予以重点关注的塑料添加剂.

1.3 SVHCs在不同行业塑料中的分布

本文对当前识别的189种SVHCs按照行业类型及添加剂功能进行统计分析[3, 27], 得到分布结果如图 2所示.从总体上看, 各行业塑料制品中均含有的多种不同性能的SVHCs, 说明各行业塑料制品中均存在一定的潜在化学品环境和健康风险.其中, 汽车、建材、电子电器、包装和纺织等行业的塑料制品中SVHCs种类最多, 分别达到116、108、100、98和88种.家庭日用品、食品接触材料、玩具和农业等行业的塑料制品中也有相当多种类的SVHCs, 分别为61、52、39和28种.医疗行业的塑料制品中的SVHCs的种类最少, 为8种.医疗、食品接触材料、玩具等行业涉及敏感用途和敏感人群, 意味着同等条件下更高的暴露风险.例如, 有研究在中国塑料餐盒中检出有机磷阻燃剂磷酸三(2-氯乙基)酯[tris(2-chloroethyl)phosphate, TCEP]等SVHCs[38].而在中国食品接触材料行业标准中, 如《食品安全国家标准食品接触用塑料材料及制品》(GB 4806.7-2023), 目前尚缺乏对上述SHVCs的限制规定, 由此可见食品接触材料中存在潜在的有害化学品健康风险.

1. 包装, 2. 建材, 3. 汽车, 4. 电子电器, 5. 纺织, 6. 家庭日用品, 7. 农业, 8. 食品接触材料, 9. 玩具, 10. 医疗 图 2 各行业塑料中的SVHCs的分布 Fig. 2 Distribution of SVHCs in plastics by industrial sector

从各类含SVHCs塑料添加剂在不同行业中的分布看, 其分布状况与其在不同类型塑料中的分布特征基本一致, 反映出不同类型塑料在各行业塑料制品中的普遍应用.各行业普遍应用到各类不同功能的塑料添加剂, 其中汽车、建材、电子电器、包装和纺织等行业几乎是各功能塑料添加剂含SVHCs种类最多的行业, 其次是日用品和玩具, 食品接触材料和医疗用品则含有相对较少的SVHCs种类.

本文进一步对SVHCs在不同塑料类型和行业类型中的分布进行正交分析, 结果如图 3所示, 清晰揭示出塑料中SVHCs在当前社会经济体系中的分布状况及特征.从中可见, SVHCs主要分布在包装、建材、汽车、电子电器和纺织这五大行业中, 较集中分布在PVC和PUR与其他多种塑料当中, 在PE、PP、PET和PC等当前社会生活中常用的塑料中也具有较普遍的分布.由此揭示出现代经济和社会中的人体和生态环境正面临着塑料中多种潜在有害化学品的环境和健康风险, 亟待采取必要的风险评估和风险管理措施.除PVC在建材行业应用的塑料添加剂外, 其他组合类型的SVHCs的种类均在50种以上, 意味着以上组合类型是SVHCs的重点关注领域.对于涉及敏感用途和敏感人群的医疗、食品接触材料和玩具等行业, PVC、PUR和其他塑料同以上行业的组合类型的SVHCs的种类均超过20种, 意味着在以上行业需要更加关注PVC和PUR等塑料中SVHCs的识别和评估, 逐步开展安全替代, 消除其环境和健康风险, 实现对于塑料的可持续的生产和消费.

1. 包装, 2. 建材, 3. 汽车, 4. 电子电器, 5. 纺织, 6. 家庭日用品, 7. 农业, 8. 食品接触材料, 9. 玩具, 10. 医疗 图 3 塑料添加剂中的SVHCs在不同塑料类型和应用行业的分布 Fig. 3 Distribution of SVHCs in plastics with different material types and industrial sectors

需要注意的是, 这一统计结果仅仅表示可能涉及某类塑料及行业的SVHCs种类, 同一化学品可能在一类塑料制品中充当多种用途.即使某一化学品可能在一类塑料制品中起到某些功能, 并不代表这类SVHCs在其中一定存在.即使存在以上不确定性, 此项工作仍然可以初步呈现不同塑料及行业中SVHCs的潜在分布图景.

2 SVHCs在塑料制品全生命周期的物质流 2.1 塑料制品中SVHCs全生命周期物质流分析方法

各种功能的SVHCs被添加到各类塑料制品中, 形成了其在各行业广泛存在的图景.塑料中的SVHCs沿着塑料制品生产加工、使用和废弃等生命周期阶段发生流动(图 4).物质流分析(material flow analysis, MFA)是工业生态学的核心方法, 以质量平衡原理为基础, 被用于产品生命周期各阶段物质库存和流动的定量评估[39].静态物质流分析(static material flow analysis)描绘了系统在某一特定时刻的状态, 动态物质流分析(dynamic material flow analysis, d-MFA)进一步考虑了在用库存, 并描绘了物质在一定时间间隔内的变化情况[39~41]. MFA早期被用于追踪电子产品废物回收处置过程中BFRs[36], 后被应用于追踪PS建材中BFRs的全生命周期的流动, 并与多介质环境归趋模型耦合, 构成了可应于各类产品中化学品(chemicals in products, CiPs)在产品全生命周期的流动、分布及环境释放的方法和模型工具[41, 42].此后, 上述方法被先后应用在电子电器产品中的溴化阻燃剂十溴二苯乙烷(decabromodiphenyl ethane, DBDPE)[43]、PVC和聚氨酯等塑料产品中的增塑剂兼阻燃剂、短链和中链氯化石蜡(short-chain & middle-chain chlorinated paraffins, SCCPs & MCCPs)[44~46]、塑料制品中的增塑剂PAEs[37, 47]以及PMT类化学品三聚氰胺[48]等SVHCs的物质流研究中.

图 4 塑料中高关注物质(SVHCs)全生命周期物质流 Fig. 4 Material flow of substances of very high concern (SVHCs) in plastics

2.2 塑料中典型SVHCs的物质流分析

BFRs是全球消费量最大的阻燃剂, 所占份额达到25%[36]. PBDEs和HBCD是主要的BFRs, DBDPE是传统BFRs的替代品, 以上BFRs主要用于电子电器、建材和汽车等行业. Morf等[36]在2005年即结合现场采样和物质流方法研究了PBDEs和HBCD这两种BFRs在瑞士某电子废物回收厂的流动情况, 估算二者在电子废物中的总流量, 以及通过回收最终进入塑料和木铸件中的比例. Li等[42]建立了针对产品中的化学品(chemicals in products, CiPs)d-MFA与多介质环境归趋耦合模拟的方法, 分析了中国房屋建材保温材料PS中HBCD从生产到废弃的全生命周期过程中动态物质流及向大气、水和土壤的多介质环境排放, 揭示出房屋建材中HBCD这类典型的POPs的长期环境排放潜力, 尤其是在废物阶段的排放潜力.Shen等[43]和Chen等[49]运用动态物质流和多介质环境归趋耦合模型研究揭示了中国EEE塑料外壳和线路板中DBDPE的持续增长及其在不同区域造成的环境释放与暴露水平, 并通过其EEE的出口贸易造成的全球污染迁移及影响.

PAEs是全球消费量最大的塑料增塑剂, 所占份额达到70%[37], 主要包括邻苯二甲酸二(2-乙基己)酯[di-(2-ethylhcxyl)phthalate, DEHP]、邻苯二甲酸二丁酯(dibutyl phthalate, DBP)和邻苯二甲酸二异丁酯(diisobutyl phthalate, DIBP), 约90%用于制造PVC产品[37], 主要用于建材和电子电器行业.在日本, DEHP使用量占PAEs使用量的60%以上[50]. Muchangos等[50]将MFA和生命周期影响评估(life cycle impact assessment, LCIA)相结合, 构建日本在1948~2030年期间的DEHP物质流, 并评估DEHP的人类健康影响.中国是世界上最大的PAEs生产国和消费国, 约80%的PAEs使用是DEHP[37]. Bi等[37]和Cui等[47]先后运用动态物质流方法分析了塑料制品中的PAEs的动态物质流, 揭示了中国在1958~2020年期间塑料制品中PAEs持续增长的使用量及其在废物流中的累积量.

随着塑料制品使用寿命的终结, 大量赋存在塑料制品中的SVHCs会随着塑料制品的报废进入废物阶段, 在垃圾拆解场、填埋场等废物处置场所及周边地区构成持续性环境和健康风险[46, 51, 52].此外, 忽视废物中赋存的大量SVHCs对相关废物进行回收利用, 将延长SVHCs在经济系统中的存在时间, 引起更加广泛和长期的环境和健康风险[53].

物质流方法的构建, 依赖于产品寿命、SVHCs环境排放系数及其在流与流、流与库之间的转移系数等关键参数.不同来源的参数的可靠性、完整性、时间相关性和地理相关性通常并不相同, 亟需建立统一的不确定性表征方法, 科学刻画不同来源参数的不确定性, 表征物质流分析结果的不确定性.此外, 目前基于现场采样和实验分析的方法往往只能刻画微观层面SVHCs的赋存分布或污染状况, 难以验证物质流分析得到的宏观结果, 物质流分析结果的验证方法有待进一步探索.

3 SVHCs在塑料制品全生命周期的环境释放 3.1 SVHCs在产品使用周期的释放

各种塑料添加剂大多以非键合的方式存在于塑料基体中, 在塑料制品的生产加工、使用和报废等阶段, SVHCs均有可能从塑料中浸出, 释放进入环境[28, 29].厘清SVHCs在产品使用生命周期的释放过程及释放机制, 是科学评估塑料制品全生命周期SVHCs环境释放, 从而有效控制SVHCs长期性区域乃至全球环境和健康风险的关键.

塑料制品中SVHCs环境释放机制研究集中于对典型SVHCs在塑料制品, 特别是食品接触材料中的迁移机制探究, 包括对特定塑料制品中典型SVHCs的分配系数和扩散系数测算与预测, 以及SVHCs迁移影响因素的探究[54~56].塑料制品中SVHCs的环境释放量估算的关键参数是环境排放系数, 以上系数主要来源于欧洲化学品局(European Chemicals Agency, ECHA)、美国环保署(United States Environmental Protection Agency, US EPA)、经济合作与发展组织(Organization for Economic Co-operation and Development, OECD)及部分行业风险评估报告等.Managaki等[57]较早开展环境释放研究, 指出日本PS建材和纺织品中HBCD的环境释放来源将逐渐从产品链的上游转移到下游. 随后, 该领域研究引入情景分析方法, 探讨不同未来政策情景对塑料制品中SVHCs环境释放的影响.例如, Li等[42]比较了不同废物处置情景下PS建材中HBCD的环境释放量, 指出拆除前筛选与焚烧相结合是最有效的报废排放减排方案. Liu等[58]评估了不同废物处置情景对日本汽车行业BFRs环境释放量的影响, 指出通过消除车辆中使用的BFRs可以避免大量PBDEs和HBCD通过回收再次进入汽车行业. Chen等[46]探究了不同国际公约履约情景对中国未来待处置的含SCCPs和MCCPs废物的规模及分布的影响, 为含POPs废物管理提供现实参考.

SVHCs类阻燃剂和增塑剂生产和使用量巨大, 在产品使用周期各阶段存在大量环境释放, 意味着塑料制品的生产加工工人、消费者和废物处置人员普遍存在的健康风险.现有关于塑料制品中SVHCs的环境释放量依赖于环境排放系数, 以上系数的测定通常基于标准化排放场景, 与现实生产、使用和废物处置场景存在较大差别, 且不同数据来源间的排放系数往往存在数量级的差异, 以上因素都给SVHCs的环境释放估算带来较大的不确定性, 未来有待进一步探究SVHCs在不同场景下的环境释放机制, 科学测算其环境排放系数.

3.2 SVHCs通过塑料泄漏的释放

塑料泄漏(plastic leakage)是指塑料制品在没有保留在塑料循环中或在报废时没有得到妥善管理, 从而泄漏到环境中的大块塑料(macroplastics)和微塑料(microplastics)[59].大块塑料可进一步在风沙吹扫、海浪侵蚀、水体扰动等机械磨损作用下分解成粒径小于5 mm的微塑料.以上泄漏的塑料碎片具有不同的降解半衰期, 将在环境中持续存在数年到上千年, 并在风力、潮汐和洋流等外力作用下进行远距离迁移扩散, 在此过程中将向环境持续释放SVHCs, 构成全球性的环境风险[30, 60~63].

微塑料是塑料泄漏的主要形式, 也是该领域的研究重点.目前已初步构建起基于产品全生命周期的微塑料总量评估方法[10, 64~66].现有关于塑料泄漏途径SVHCs环境释放研究, 基于现场采样和实验分析, 集中于环境介质中塑料碎片中典型SVHCs检出水平和环境释放机制研究, 以及全球、国家或区域尺度单个产品形成的塑料碎片的SVHCs传输量估算.与塑料制品中SVHCs的广泛分布一致的是, 在塑料碎片中检出了多种SVHCs[67~71].例如, Jang等[71]在韩国海洋PS塑料浮标中检出高浓度HBCD, Nurlatifah等[67]在北太平洋西部深海PVC塑料碎片中检测到极高浓度的DEHP, Deng等[68]在中国长江口塑料碎片中检出高浓度的PAEs和PBDEs.

塑料种类和化学品的物理化学性质等是影响塑料碎片和微塑料吸附和浸出SVHCs的重要因素.例如, O'Connor等[72]指出化学品在不同类别塑料中的分配大致遵循LDPE≈HDPE≥PP > PVC≈PS的顺序, Gouin等[73]研究发现化学品的辛醇-水分配系数高有利于海洋环境中的微塑料积累有机污染物.

海洋环境是塑料碎片重要的汇[74, 75], 河流是重要运输途径, 全球每年有1.15~2.41万t塑料碎片和微塑料经河流传输进入海洋, 中国被认为是贡献最大的国家[76, 77].Mai等[78]估算出中国珠江三角洲河流出水口塑料碎片赋存的多环芳烃(polycyclic aromatic hydrocarbons, PAHs)和PBDEs的平均流出量分别约为6.75 kg·a-1和3.77 kg·a-1. Zhang等[79]估算出2 017年中国农用塑料薄膜经回收和土壤侵蚀后形成的塑料碎片量达到46.50万t, 其中有4 329 t最终排入海洋;在农膜使用和残留过程中, 共释放了91.5 t典型PAEs.

现有关于塑料中SVHCs环境释放研究, 能够局部刻画塑料泄漏带来的环境污染现状, 但未能全面揭示环境释放的来源和机制, 识别重点污染环节和关键影响因素, 而从产品生命周期角度出发的微塑料总量评估方法则能够为SVHCs环境释放研究提供更宏观的研究视角.

4 结论与展望

(1)塑料制品中广泛存在各类SVHCs, 集中分布在PVC和PUR等塑料类别, 以及包装、建材、汽车、电子电器和纺织等行业类型.增塑剂和阻燃剂的用量最高, SVHCs品类集中, 以PAEs、PBDEs和HBCD为典型代表, 是SVHCs风险评估和风险管理的重点.塑料制品中的潜在有害化学品数量众多, 未来亟需重视各类塑料制品中潜在有害化学品的识别, 构建塑料中有害化学品数据库, 为有害化学品的淘汰和安全替代提供基础信息.

(2)塑料制品生产加工、使用和报废过程中持续发生SVHCs环境释放;大量SVHCs随产品使用寿命终结进入废物阶段, 废物源将构成SVHCs的长期潜在释放来源, 加强废物管理是降低塑料制品中SVHCs环境和健康风险的关键环节之一.物质流分析方法是开展塑料中SVHCs全生命周期环境释放研究的重要方法, 未来亟需优化SVHCs环境排放系数测算方法及动态物质流分析方法, 以构建更科学的物质流.

(3)塑料泄漏构成SVHCs环境释放的重要来源, SVHCs伴随塑料碎片和微塑料的迁移扩散而广泛分布在各类环境介质中.现有关于塑料泄漏途径SVHCs环境释放研究以微观研究为主, 未能全面揭示SVHCs环境释放来源, 未来亟需开展塑料泄漏途径化学品释放机制研究, 建立基于不同塑料制品全生命周期的塑料泄漏途径SVHCs环境释放评估方法, 全面揭示塑料碎片和微塑料的环境和健康风险.

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