The influence of fulvic acid on molybdenum bioavailability assessed by Caenorhabditis elegans

Molybdenum (Mo), a vital metallic element for the growth of flora and fauna, holds considerable commercial significance. However, research on Mo toxicity and its bioavailability remains limited. This study exploited the model organism Caenorhabditis elegans to examine the biological toxicity of Mo exposure in aquatic environments. By simulating environmental systems, the influence of fulvic acid (FA) on the bioavailability of Mo was investigated. The EquRay (Equilibrium Partitioning Ray) method was utilized to develop a binary mixed exposure system, exposing nematodes to a combination of FA and Mo with increased reactivity to examine the impact of FA on the composite toxicity of Mo. The results indicated that high-concentration Mo exposure (3000 mg L^-1) led to significant abnormalities in nematode survival and movement, with a 24-h median lethal concentration (LC₅₀) of 6000 mg L^-1. However, the addition of FA did not significantly ameliorate the survival toxicity of Mo but instead generated abnormally hyperactive movement in nematodes, particularly manifested as robust head thrashing,which was significantly higher than that of the control group. This study integrates "pollutants - biomarkers - effects" to analyze the bioavailability of heavy metals and their influencing factors, offering experimental evidence and theoretical support for creating and forecasting ecological risk models of heavy metal Mo in aquatic environments.