Evaluation of the Barrier Effect of Polylactic Acid-Modified Membrane on Odours at the Excavated Soil Interface of a Pesticide-Contaminated Site

Abstract

Polylactic acid (PLA) is a highly promising bio-based polymer that can replace petroleum-based materials. The PLA-modified membrane has been found to effectively block soil odours in laboratory experiments, but its barrier effect at the excavated soil interfaces of actual pesticide sites requires further evaluation. This study investigates the barrier effect of the PLA-modified membrane on odours at the excavated soil interface of a pesticide-contaminated site in Guangdong Province, China. The membrane’s barrier effect on odours was comprehensively evaluated using the static chamber technique with three indicators: diffusion flux, odour concentration, and a health risk index. The results showed that the initial diffusion fluxes of six main odour substances: m- and p-xylene, o-xylene, toluene, ethylbenzene, n-propylbenzene, and cumene were 1.95 × 100, 2.88 × 10−1, 7.27 × 10−3, 1.49 × 100, 2.97 × 10−3, and 3.89 × 10−3 mg/(m2·s) based on the contribution rate. After laying the PLA-modified membrane, the flux reduction rate of all six odour substances was generally >90%. The background odour concentration in the test area was 109.56, and the odour concentration after laying the membrane was <1.12. The initial non-carcinogenic and carcinogenic risk indices of the test area were 3.03 and 1.62 × 10−4, respectively. After laying the membrane, these indices were <0.05 and <3.78 × 10−7, respectively, indicating no health risk. Overall, the PLA-modified membrane had a good barrier effect on odours in the on-site application, effectively reducing the diffusion and nuisances of odours, as well as their health risks.