塑岩:成因、分布与微塑料释放特征  

Plastistone:Diagenesis,Global Distribution,and Microplastic Generation Characteristics

作　　者：王刘炜 侯德义[1] WANG Liuwei;HOU Deyi(School of Environment,Tsinghua University,Beijing 100084,China)

机构地区：[1]清华大学环境学院,北京100084

出　　处：《环境科学研究》2023年第8期1457-1466,共10页Research of Environmental Sciences

基　　金：国家自然科学基金项目(No.42225703)。

摘　　要：塑料污染是受到全球广泛关注的环境问题,对人体健康与生态系统造成潜在威胁.已有证据表明,塑料能够与自然界的岩石发生稳定结合,成为人类活动作为一种新的地质营力影响地球地质周期的直接证据.在这些发现的基础上,本文提出并定义了一种新的沉积岩类型——塑岩.塑岩是塑料与碎屑物质胶结形成的沉积岩;在塑岩中,肉眼可见的塑料与沉积岩原始物质成分在地壳表层的条件下,经熔化-凝固、蒸发、吸附等物理、化学过程,发生了不可逆的结合.在前期发现的基础上,针对2022年7月在广西壮族自治区河池市采集得到的陆地生态系统塑岩样品,进一步研究其在干湿循环情形下微塑料的释放与粒径分布特征.研究表明,在干湿循环老化情形下,从塑岩中释放得到的微塑料的粒径分布可以被条件概率老化模型刻画.从塑岩中剥离的低密度聚乙烯(LDPE)和聚丙烯(PP)塑料的破碎维数总体在1.5~2.5之间浮动,呈现出二维破碎的特征;LDPE的破碎过程存在先加剧后减缓的过程,但PP的破碎维数恒定在2附近,预示塑岩结合的PP塑料具有长期释放微塑料的能力.除此之外,在塑岩释放的微塑料中,超过60%为具有较高迁移性的圆球状微塑料,其平均粒径显著低于其他形状,具有较高的迁移性,预示着潜在的生态风险.需要指出的是,目前针对塑岩的相关报道对其胶结成岩过程以及在自然界中的长期环境行为仍不甚明确,后续研究需要对其在自然环境中的成岩过程、赋存规律与长期归趋开展进一步研究与观测.Plastic pollution is an environmental problem of global concern,posing potential risks to human health and ecosystems.Mounting evidence suggests that plastic debris can irreversibly adhere to the host rock,providing direct evidence of how human activities are altering Earth's geological record.Based on these findings,this study defines a new type of sedimentary rock called plastistone.Plastistone is a sedimentary rock formed of visible plastic and clasts derived from pre-existing rock that were cemented together.In a plastistone,visible synthetic plastic polymers were irreversibly stuck onto or incorporated within the mineral matrix due to various physical and chemical processes such as melting-freezing,evaporation,and adsorption.This study aimed to examine the generation and size distribution of microplastics derived from plastistones collected in the terrestrial ecosystem during a field survey conducted in Hechi City,Guangxi Zhuang Autonomous Region,China,in July 2022.It was discovered that microplastics generated from plastistones during artificial wet-dry cycling followed a conditional fragmentation pattern.The fragmentation dimension modeling results showed a pseudo-2D fragmentation pattern for plastistones,with values falling within 1.5-2.5.The fragmentation dimension values for PP plastistones remained steady,while those for LDPE first increased and then decreased.Furthermore,more than 60% of the identified microplastics were spherical in shape and had smaller diameters compared to other polymer types.This emphasizes the potential ecological risks associated with these highly mobile microplastic particles.Additionally,it is important to note that the lithification process and long-term environmental behavior of plastistones remain unclear at present.Therefore,future research should focus on investigating these aspects in greater detail.

关 键 词：沉积岩 塑岩 地质 粒径分布 微塑料 

分 类 号：X54[环境科学与工程—环境工程]