We can't find the internet
Attempting to reconnect
Something went wrong!
Hang in there while we get back on track
Microplastics can Alter the Nitrogen Cycle in Surface Flow Constructed Wetlands
Summary
Both conventional PVC and biodegradable PLA microplastics disrupted nitrogen cycling in constructed wetlands, with PVC causing ammonium accumulation and PLA acting as a carbon source, while both enhanced biofilm formation and enzyme activities at higher concentrations. These polymer-specific effects on nitrogen dynamics reveal that microplastic contamination poses distinct and complex threats to the water treatment functions of natural and engineered wetlands.
The accumulation of microplastics (MPs) in wetlands poses threats to aquatic ecosystems. However, the impacts of MPs on the nitrogen cycle in surface flow constructed wetlands (SFCWs) remain unclear. This study investigated the impacts of polyvinyl chloride (PVC, conventional) and polylactic acid (PLA, biodegradable) MPs at concentrations of 0%, 0.1%, 1.0%, and 5.0% on nitrogen dynamics and key nitrogen cycle enzyme activities in SFCWs. Results showed that MPs altered nitrogen concentrations by decreasing total nitrogen (TN) in the overlying water while increasing organic nitrogen (Norg). Notably, PVC MPs caused ammonium nitrogen (NH4+-N) accumulation due to hindered oxygen diffusion, while PLA MPs decreased it by serving as carbon sources. Additionally, MPs promoted microbial colonization and increased biofilm biomass in sediments. Oxygen penetration depth decreased with increasing MP concentrations. The enzymatic analysis further demonstrated that MPs significantly enhanced the activities of key nitrogen cycle enzymes, including ammonia monooxygenase (AMO), hydroxylamine oxidoreductase (HAO), nitrate reductase (NR), nitrite reductase (NIR), and hydrazine synthase (HZS), particularly at higher concentrations. Overall, our findings fill the gap in understanding polymer-specific MP impacts on wetland nitrogen cycling and provide a scientific basis for mitigating ecological risks and safeguarding wetland functional stability.