Study on Factors Influencing Mercury Methylation in Shenyang Qixing Wetland under Different Seasonal Conditions

Dissolved organic matter (DOM), an active organic component in the soil, plays a pivotal regulatory role in mercury methylation within wetland ecosystems. This process, particularly amid escalating influences from climate change and anthropogenic activities, carries significant implications for global environmental health. To elucidate the key factors influencing mercury methylation in soil, sampling surveys were conducted in May, July, and September at the Qixing Wetland in Shenyang. The findings indicated that the average concentrations of methylmercury (MeHg) and total mercury (THg) at Qixing Wetland were 3.91 ng·g⁻¹ and 173.45 ng·g⁻¹, respectively, with notably lower concentrations observed during the summer months. The highest rate of soil mercury methylation (%MeHg) was recorded in May at 4.43%, yielding an overall methylation rate of 2.91%. Correlation analysis, principal component analysis, and random forest modeling revealed that %MeHg is jointly influenced by the sampling month and various environmental parameters within the wetland ecosystem. In May, pH and dissolved organic carbon (DOC) emerged as primary determinants, whereas in July, fulvic-like substance proportions (%Fmax(A)) alongside soil organic carbon (SOC) were predominant; conversely, DOM spectral characteristics were the dominant influence in September. This study underscores the intricate seasonal dynamics and environmental factors affecting mercury methylation processes within wetlands while highlighting their critical role in regulating the biogeochemical cycling of mercury. Consequently, safeguarding wetland ecosystems is essential for preserving their regulatory functions for environmental health while mitigating risks associated with mercury bioaccumulation.