Abundance and morphology of microplastics in an agricultural soil following long-term repeated application of pig manure

Jie Yang; Ruijie Li; Qian Zhou; Lianzhen Li; Yuan Li; Chen Tu; Xinyue Zhao; Kuanxu Xiong; Peter Christie; Yongming Luo

doi:10.1016/j.envpol.2020.116028

Abundance and morphology of microplastics in an agricultural soil following long-term repeated application of pig manure

Environ Pollut. 2021 Mar 1:272:116028. doi: 10.1016/j.envpol.2020.116028. Epub 2020 Nov 9.

Authors

Jie Yang¹, Ruijie Li², Qian Zhou², Lianzhen Li³, Yuan Li³, Chen Tu³, Xinyue Zhao³, Kuanxu Xiong³, Peter Christie⁴, Yongming Luo⁵

Affiliations

¹ CAS Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, 210008, China; University of the Chinese Academy of Sciences, Beijing, 100049, China.
² CAS Key Laboratory of Coastal Zone Environmental Processes and Ecological Remediation, Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences, Yantai, 264003, China; University of the Chinese Academy of Sciences, Beijing, 100049, China.
³ CAS Key Laboratory of Coastal Zone Environmental Processes and Ecological Remediation, Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences, Yantai, 264003, China.
⁴ CAS Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, 210008, China.
⁵ CAS Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, 210008, China; CAS Key Laboratory of Coastal Zone Environmental Processes and Ecological Remediation, Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences, Yantai, 264003, China. Electronic address: ymluo@issas.ac.cn.

PMID: 33199067
DOI: 10.1016/j.envpol.2020.116028

Abstract

Microplastics occur widely in the terrestrial environment and they currently occur in organic fertilizers applied to agricultural land. However, there is little information available on the accumulation of microplastics in soils fertilized over the long term. Here, we investigate the characteristics of microplastics in both pig manure and soil following long-term manure application in an attempt to assess their accumulation and the potential risk to agricultural soils of repeated application of pig manure. Microplastics were separated from soil and pig manure samples using a sequential flow separation and flotation method. The abundances of microplastics were 16.4 ± 2.7 and 43.8 ± 16.2 particles kg^-1 in control plots (CK, no manure applied) and plots amended annually with pig manure for 22 years (PM), respectively. The microplastics (especially fragments) were significantly enriched in PM-amended soil compared with the control plots. The average annual abundance of microplastics was 1250 ± 640 particles kg^-1 in manure. Interestingly, the type and polymer composition of microplastics were very similar in the soil and manure. Differences in color and particle size indicate that microplastics sourced from pig manure may be gradually weathered and degraded after incorporation into the soil. The average accumulation rate of microplastics in the agricultural soil with long-term application of pig manure was estimated to be 3.50 ± 1.71 million particles ha^-1 a^-1. The microplastics in the manured soil displayed complicated weathered surfaces. The presence of carbonyl groups suggests that the weathered microplastics in soil may have the potential to adsorb contaminants.

Keywords: Accumulation; Farmland soil; Long-term fertilization; Microplastics; Morphology; Pig manure.

MeSH terms

Agriculture
Animals
Fertilizers / analysis
Manure*
Microplastics
Plastics
Soil*
Swine

Substances

Fertilizers
Manure
Microplastics
Plastics
Soil