School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China; School of Agriculture and Biology, Shanghai Jiao Tong University, Shanghai, 200240, China.
School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China; Department of Environmental Engineering, National Cheng Kung University, Tainan City, 701, Taiwan.
Chemosphere. 2021 Oct;280:130593. doi: 10.1016/j.chemosphere.2021.130593. Epub 2021 Apr 16.
With a narrow margin between beneficial and toxic effects, selenium (Se) is of great concern due to its increasing level in aquatic environments. The accumulation and transformation of Se by the cyanobacterium Microcystis aeruginosa and effects of nutrients, particularly sulfate, were investigated. The nutrient-deprived cyanobacterium removed water-borne selenate (82.2 ± 0.93%) faster than selenite (58.9 ± 1.77%), with 86.0 ± 1.41% and 77.2 ± 1.00%, respectively, of the Se accumulated in the biomass and the rest volatilized. When supplied with excess nutrients, the Se accumulation and volatilization rates were significantly inhibited, with the removal efficiency dropping to 50.2 ± 2.59% and 7.37 ± 0.93% for selenite and selenate, respectively. When M. aeruginosa was tested with inadequate, appropriate, and adequate levels of sulfate, Se uptake decreased with increasing sulfate concentrations, particularly for selenate (from 34.1 to 4.81%). Using X-ray absorption near-edge structure to speciate biomass Se, selenite and selenate were transformed to organo-Se (87.3-100%), with or without nutrients present, suggesting M. aeruginosa could efficiently reduce Se oxyanions to more bioavailable forms. With increasing sulfate levels (5.0 and 10.0 mg S/L), percentages of SeMet converted from selenite decreased by 28.2-33.0%, with 19.1-33.2% as elemental Se, while organo-Se remained dominant (93.6-95.1%) in selenate-treated M. aeruginosa. Transmission electron microscopy shows structural damage in the cell wall at exposure to selenite (1600 μg Se/L), with the intracellular structure intact. To prevent Se biomagnification along aquatic food chains, the Se-laden biomass was combusted as a post-treatment, leading to a significant reduction in Se content (∼99.2%) and Se bioavailability, with inorganic Se (45.0-70.5%) predominant in the residue.
由于硒在水生环境中的含量不断增加，其有益和有毒作用之间的差距很小，因此备受关注。本研究调查了蓝藻铜绿微囊藻对硒的积累和转化，以及营养物质（特别是硫酸盐）的影响。与亚硒酸盐（58.9 ± 1.77%）相比，缺营养的蓝藻更快地去除水中的硒酸盐（82.2 ± 0.93%），分别有 86.0 ± 1.41%和 77.2 ± 1.00%的硒积累在生物量中，其余部分挥发。当提供过量营养物质时，硒的积累和挥发率显著受到抑制，硒酸盐和硒酸盐的去除效率分别降至 50.2 ± 2.59%和 7.37 ± 0.93%。当用不足、适当和足够水平的硫酸盐测试铜绿微囊藻时，硒的吸收随硫酸盐浓度的增加而降低，特别是对于硒酸盐（从 34.1 降至 4.81%）。使用 X 射线吸收近边结构对生物质硒进行形态分析，结果表明，无论是否存在营养物质，亚硒酸盐和硒酸盐都转化为有机硒（87.3-100%），这表明铜绿微囊藻可以有效地将硒氧阴离子还原为更具生物利用性的形式。随着硫酸盐水平（5.0 和 10.0 mg S/L）的增加，亚硒酸盐转化为硒代蛋氨酸的百分比降低了 28.2-33.0%，其中元素硒为 19.1-33.2%，而有机硒在硒酸盐处理的铜绿微囊藻中仍占主导地位（93.6-95.1%）。透射电子显微镜显示，在暴露于亚硒酸盐（1600 μg Se/L）时，细胞壁结构受损，但细胞内结构完整。为了防止硒在水生食物链中生物放大，对负载硒的生物质进行了燃烧后处理，导致硒含量（约 99.2%）和硒生物利用度显著降低，残渣中以无机硒（45.0-70.5%）为主。
