Li Xin-Yu, Liu Hong-Tao, Wang Li-Xia, Guo Hao-Nan, Zhang Jun, Gao Ding
Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China; College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, China.
Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China; Engineering Laboratory for Yellow River Delta Modern Agriculture, Chinese Academy of Sciences, Beijing 100101, China.
Sci Total Environ. 2022 Jun 20;826:154206. doi: 10.1016/j.scitotenv.2022.154206. Epub 2022 Feb 28.
Microplastics (MPs) are emerging pollutants that are enriched in sludge. They enter soil through sludge soil amendment, landfill, and discard, which will cause inescapable environmental pollution risks. Sludge treatment technology commonly used in China include anaerobic digestion (AD), thermal drying (TD), thermal hydrolysis (TH) and aerobic composting (AC). In this study, characteristics of MPs in sewage sludge from four representative large cities in China (Zhengzhou, Chongqing, Guangzhou, and Guilin) were analyzed. Effects of four representative sludge treatment technology on sludge MPs were also studied. In addition, the amount of MPs input to soil from sludge in China was estimated. The abundance range of sludge MPs of representative cities in China was 1448-11,125 n∙kg DW. Previous studies indicate that this abundance range is low among other domestic cities and is close to that of European countries. MPs were predominantly fiber-shaped, accounting for 46.66%; 56.5% MPs were white and transparent, and 62.5% were polypropylene and polyethylene. The abundance of MPs in the sludge increased after TH, indicating that MPs broke into smaller particles. However, the other three treatment methods had no significant influence on the abundance of MPs. Scanning electron microscopy analysis showed that the micro-morphology of sludge MPs surface were rougher after AD, and MPs cracked following TD and TH. Furthermore, broken edges were more blurred after TH, and surfaces of MPs were damaged and eroded after AC. The input quantities of MPs in sludge to soil was deduced to be 10 particles per year. These results are important for controlling the potential risk of sludge MPs in China.
微塑料（MPs）是一类新兴污染物，在污泥中富集。它们通过污泥土壤改良、填埋和丢弃进入土壤，这将导致不可避免的环境污染风险。中国常用的污泥处理技术包括厌氧消化（AD）、热干燥（TD）、热水解（TH）和好氧堆肥（AC）。本研究分析了中国四个代表性大城市（郑州、重庆、广州和桂林）污水污泥中微塑料的特征。还研究了四种代表性污泥处理技术对污泥微塑料的影响。此外，估算了中国污泥进入土壤的微塑料数量。中国代表性城市污泥微塑料的丰度范围为1448 - 11125 n∙kg干重。先前的研究表明，在国内其他城市中，这个丰度范围较低，且接近欧洲国家。微塑料主要呈纤维状，占46.66%；56.5%的微塑料为白色透明，62.5%为聚丙烯和聚乙烯。热水解后污泥中微塑料的丰度增加，表明微塑料破碎成了更小的颗粒。然而，其他三种处理方法对微塑料的丰度没有显著影响。扫描电子显微镜分析表明，厌氧消化后污泥微塑料表面的微观形态更粗糙，热干燥和热水解后微塑料出现裂纹。此外，热水解后破碎边缘更模糊，好氧堆肥后微塑料表面受损并被侵蚀。推断污泥中微塑料进入土壤的数量为每年10个颗粒。这些结果对于控制中国污泥微塑料的潜在风险具有重要意义。
