Yan Changzhou, Wang Zhenhong, Luo Zhuanxi
Key Laboratory of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China.
Key Laboratory of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China; College of Chemistry and Environment, Minnan Normal University, Zhangzhou 363000, China.
PLoS One. 2014 Dec 30;9(12):e116099. doi: 10.1371/journal.pone.0116099. eCollection 2014.
Phytoplankton plays an important role in arsenic speciation, distribution, and cycling in freshwater environments. Little information, however, is available on arsenic efflux from the cyanobacteria Microcystis aeruginosa under different phosphate regimes. This study investigated M. aeruginosa arsenic efflux and speciation by pre-exposing it to 10 µM arsenate or arsenite for 24 h during limited (12 h) and extended (13 d) depuration periods under phosphate enriched (+P) and phosphate depleted (-P) treatments. Arsenate was the predominant species detected in algal cells throughout the depuration period while arsenite only accounted for no greater than 45% of intracellular arsenic. During the limited depuration period, arsenic efflux occurred rapidly and only arsenate was detected in solutions. During the extended depuration period, however, arsenate and dimethylarsinic acid (DMA) were found to be the two predominant arsenic species detected in solutions under -P treatments, but arsenate was the only species detected under +P treatments. Experimental results also suggest that phosphorus has a significant effect in accelerating arsenic efflux and promoting arsenite bio-oxidation in M. aeruginosa. Furthermore, phosphorus depletion can reduce arsenic efflux from algal cells as well as accelerate arsenic reduction and methylation. These findings can contribute to our understanding of arsenic biogeochemistry in aquatic environments and its potential environmental risks under different phosphorus levels.
浮游植物在淡水环境中砷的形态、分布和循环中起着重要作用。然而，关于不同磷酸盐条件下铜绿微囊藻的砷流出情况，目前所知甚少。本研究通过在富含磷酸盐（+P）和磷酸盐耗尽（-P）处理的有限（12小时）和延长（13天）净化期内，将铜绿微囊藻预先暴露于10 µM砷酸盐或亚砷酸盐24小时，来研究其砷流出和形态。在整个净化期内，砷酸盐是在藻类细胞中检测到的主要形态，而亚砷酸盐仅占细胞内砷的不超过45%。在有限净化期内，砷迅速流出，溶液中仅检测到砷酸盐。然而，在延长净化期内，在-P处理下，砷酸盐和二甲基砷酸（DMA）是溶液中检测到的两种主要砷形态，但在+P处理下，仅检测到砷酸盐。实验结果还表明，磷对加速铜绿微囊藻的砷流出和促进亚砷酸盐生物氧化有显著影响。此外，磷的耗尽会减少藻类细胞的砷流出，并加速砷的还原和甲基化。这些发现有助于我们理解水生环境中砷的生物地球化学及其在不同磷水平下的潜在环境风险。
