Micro/nanoplastic pollution heterogeneously increased greenhouse gas emissions from wetlands: A multilevel meta-analysis

Abstract

The ubiquitous presence of micro/nanoplastics (MNPs) in the environment poses high potential risks to living organisms and ecosystems. Wetlands are important sinks for MNPs, which can impact the ecological and environmental functions of wetland systems. However, the responses of greenhouse gas (GHG) emissions from wetlands to MNPs have rarely been evaluated. A multilevel meta-analysis was conducted to assess the effect of MNPs on GHG (CO2, CH4, and N2O) emissions from wetlands. The results showed that the presence of MNPs generally led to increases in GHG emissions from wetlands, especially N2O emissions. MNP type and exposure dose were the decisive factors influencing wetland GHG emissions, with CO2 and N2O emissions stimulated by biodegradable MNPs made of polylactic acid and by a high MNP dose of 1-2%, while polystyrene reduced CO2 and N2O emissions, and a low MNP dose of less than 0.5% increased CH4 emissions. CO2 emissions from the sediment of coastal wetlands were more sensitive to MNP pollution, while CH4 emissions from the sediment of freshwater wetlands were significantly increased by MNP pollution. Furthermore, microbial diversity and the number of carbon–nitrogen cycling functional genes associated with GHG emissions in wetlands were increased by MNPs. More research on the effect of MNPs on GHG emissions from wetlands over a longer time is needed, especially in real wetland ecosystems with aquatic organisms.