Mercury Reduction, Uptake, and Species Transformation by Freshwater Alga Chlorella vulgaris under Sunlit and Dark Conditions.
Xujun LiangNali ZhuAlexander JohsHongmei ChenDale A PelletierLijie ZhangXixiang YinYuxi GaoJiating ZhaoBaohua GuPublished in: Environmental science & technology (2022)
As a major entry point of mercury (Hg) to aquatic food webs, algae play an important role in taking up and transforming Hg species in aquatic ecosystems. However, little is known how and to what extent Hg reduction, uptake, and species transformations are mediated by algal cells and their exudates, algal organic matter (AOM), under either sunlit or dark conditions. Here, using Chlorella vulgaris (CV) as one of the most prevalent freshwater model algal species, we show that solar irradiation could enhance the reduction of mercuric Hg(II) to elemental Hg(0) by both CV cells and AOM. AOM reduced more Hg(II) than algal cells themselves due to cell surface adsorption and uptake of Hg(II) inside the cells under solar irradiation. Synchrotron radiation X-ray absorption near-edge spectroscopy (SR-XANES) analyses indicate that sunlight facilitated the transformation of Hg to less bioavailable species, such as β-HgS and Hg-phytochelatins, compared to Hg(Cysteine) 2 -like species formed in algal cells in the dark. These findings highlight important functional roles and potential mechanisms of algae in Hg reduction and immobilization under varying lighting conditions and how these processes may modulate Hg cycling and bioavailability in the aquatic environment.
Keyphrases
- fluorescent probe
- induced apoptosis
- aqueous solution
- living cells
- cell cycle arrest
- endoplasmic reticulum stress
- risk assessment
- oxidative stress
- high resolution
- magnetic resonance imaging
- computed tomography
- climate change
- signaling pathway
- magnetic resonance
- cell surface
- single molecule
- mass spectrometry
- organic matter
- human health
- high intensity