为了解地表水环境中广泛存在的自然水体生物膜表面巯基基团的存在情况和它们对典型重金属的吸附特征，建立了基于特异性巯基掩蔽剂的适用于自然水体生物膜中巯基掩蔽的方法，并利用该方法研究了生物膜中巯基的表面浓度，以及不同pH下生物膜巯基对典型重金属Cu、Pb和Cd的吸附特征。研究结果表明：所建立的巯基掩蔽方法能有效掩蔽巯基且对生物膜中微生物的影响很小。自然水体生物膜表面存在相对较低浓度的巯基基团，浓度为（5.8 ± 0.6） μmol/g，占生物膜表面总位点浓度的5.7%。尽管巯基浓度较低，但由于其具有更强的重金属结合能力，使其在重金属浓度较低时（吸附体系中生物膜对重金属的理论负载量 < 1.0 μmol/g时）对生物膜吸附重金属有重要贡献，显著影响生物膜吸附重金属的特征；且这种规律基本不受体系pH和重金属种类的影响。研究结果证明生物膜中巯基对天然水环境中重金属的环境行为和效应也有重要影响，进一步体现了自然水体生物膜的重要环境意义。

To determine the presence of sulfhydryl groups on natural aquatic biofilms and their adsorption characteristics for typical heavy metals, a method for sulfhydryl masking in the biofilms based on a specific masking agent was established in this study. Based on this method, surface concentration of sulfhydryl group in natural biofilms and their adsorption characteristics for typical heavy metals, including Cu, Pb, and Cd, at different pH were investigated. The results indicate that the established masking method can effectively mask sulfhydryl groups and has little effect on microorganisms in biofilms. There are relatively low concentrations of sulfhydryl groups on the surface of natural biofilms, with a concentration of (5.8 ± 0.6) μmol/g, accounting for 5.7% of the total site concentration on the biofilms. Despite the low concentration of sulfhydryl groups, their stronger metal binding capacity makes them significantly contribute to metal adsorption when the metal concentration is low (the theoretical loading of heavy metals by the biofilm is less than 1.0μmol/g). This pattern is essentially unaffected by the pH of the adsorption system and the type of heavy metal. This proves that sulfhydryl groups in biofilms also have an important impact on the behavior and risk of heavy metals in natural aquatic environments with low metal content, further highlighting the environmental significance of natural biofilms.