Abstract:
Particulate plastics (i.e., ‘micro-plastics’ or ‘nano-plastics) are synthetic polymer
particles measuring less than 5 mm in diameter. These particles have extensively
been used worldwide as primary constituents (i.e., in cosmetics) and secondary
constituents (i.e., breakdown of plastic mulch). Therefore, particulate plastics are
widely found in aquatic and terrestrial environments and also identified as causing
severe pollution. Because their impact on microbial functions in terrestrial
environment remains largely unclear, an incubation study was conducted to
examine the impact of particulate plastic contamination on microbial activity in soil.
In this study soil samples were mixed with particulate plastics at the ratio of 6.4%
(w/w) in soil. Two types of contaminants, perfluorooctane sulfonate (PFOS) at 1000
μg kg−1 soil and copper (Cu) at 500 mg kg−1 soil, were also used. After two weeks of
the incubation period, soil respiration, microbial biomass carbon (MBC),
dehydrogenase activity (DHA) and bioavailable Cu were measured. Results
indicated low basal respiration, DHA and MBC in contaminated soil treatments.
Although Cu toxicity caused a 30% decrease in DHA in soil, the toxicity caused by
both Cu and PFOS was more profound. The microbial activities in the contaminated
soils were higher in the presence than absence of particulate plastic addition. Our
experimental evidence suggests that the particulate plastics interact with organic
and inorganic contaminants and modulate their toxicity to soil microbial activities.
