Bioconcentration of Inorganic and Methyl Mercury by Algae Revealed Using Dual-Mass Single-Cell ICP-MS with Double Isotope Tracers
Tian et al.
환경 과학 및 기술, 2024
DOI:10.1021/acs.est.3c10884
최근 발표된 환경 과학 및 기술 의 연구원들이 이끄는 중국과학원 생태환경과학연구센터, 중국 베이징, 중국, employed the icpTOF R to investigate the bioconcentration of mercury by freshwater and marine algae using single-cell ICP-MS, revealing how factors like cell size, algal density, and kinetics of mercury influx and efflux influence the biogeochemical cycling and environmental risk of mercury in the food web.
Mercury (Hg) is a toxic metal present in freshwater and marine environments, existing mainly as inorganic Hg (IHg) and organic Hg (methyl mercury, MeHg). IHg is the dominant form, while MeHg poses significant risks due to biomagnification and neurotoxicity, especially in the food web. Algae, as primary producers, accumulate MeHg at much higher concentrations than surrounding water, facilitating its transfer to higher trophic levels. IHg from algae can sink into sediments, acting as a Hg sink, and can be transformed into MeHg by microbial methylation.
Accurate detection of Hg, particularly in algae, is challenging due to its varied forms and low concentrations. Conventional methods are not suitable for unicellular algae, where Hg bioconcentration varies. The study used dual-mass single-cell inductively coupled plasma mass spectrometry (ICP-MS) and ICP-time-of-flight (TOF)-MS to detect and quantify IHg and MeHg in individual algae cells.
The study showed that MeHg is more efficiently transferred through the food web than IHg, and differences in Hg bioconcentration were observed at the primary producer stage. The bioconcentration of Hg in algae follows a dynamic equilibrium process influenced by influx/adsorption and efflux/desorption. Algal density affects Hg levels, with lower Hg concentrations in eutrophic waters leading to reduced Hg transfer efficiency in the food web. This suggests that MeHg proportions decrease with higher algal density, further reducing MeHg transfer efficiency. Significant intraspecies and interspecies heterogeneity in Hg concentrations was observed, with larger algal cells accumulating more Hg, potentially affecting Hg transfer through the food web due to their vertical distribution in the water column.
This study highlights the effectiveness of our cutting-edge icpTOF technology for high-throughput, precise measurement of Hg species, revealing heterogeneity in Hg bioconcentration across species and cells. It also uncovered energy-dependent mechanisms involved in the bioconcentration processes. By providing an optimized pretreatment procedure for single cell ICP-MS to analyze both freshwater and marine algae, this method offers high sensitivity, particularly with enriched Hg isotopes, and enables the study of multiple Hg species (IHg, MeHg, Hg0, HgS) in a single system.
