The nature of dissolved organic matter determines the biosorption capacity of Cu by algae. (August 2020)

• Record Type: Journal Article
• Authors: Chen, Xiujuan; Zheng, Mengmeng; Zhang, Gaoxiang; Li, Feili; Chen, Hexuan; Leng, Yaling
• Is Part Of: Chemosphere. Volume 252(2020)
• Publication Date: 2020-08
• Subjects: Transphilic acid -- Freshwater alga -- Bioaccumulation -- Ternary complex -- Multi-layer adsorption; Pollution -- Periodicals; Pollution -- Physiological effect -- Periodicals; Environmental sciences -- Periodicals; Atmospheric chemistry -- Periodicals; 551.511
• DOI: 10.1016/j.chemosphere.2020.126465
• Languages: English
• ISSNs: 0045-6535

Abstract

Abstract: The role of dissolved organic matter (DOM) on the biochemical behavior and toxicity of heavy metals in water is very important but complex and unclear. The present work extracted DOM from a natural water and separated it into three fractions, namely humic acid (HA), fulvic acid (FA) and transphilic acid (TPA). Optical detection showed that HA had most aromatic ring skeletons, FA had more aromatic ring hydrophilic groups, and TPA had the largest number of hydroxyl or carboxyl groups. Their effects on the toxicity of Cu by Chlorella pyrenoidosa depended on types and concentration of DOM. In the case of algal exposure to 0.003 mM initial Cu concentration, the final algal optical density increased from 0.317 of the control group to 0.345, 0.645 and 0.435 in the presence of 20, 10 mg L −1 HA, and 10 mg L −1 TPA, respectively, but were suppressed to 0.246, 0.117 and 0.234 in the presence of 10, 20 mg L −1 FA and 20 mg L −1 TPA. Most adsorption isotherms lost the linearity in the presence of HA, FA and TPA. The adsorbed Cu increased from 0.242 to 0.477 mmol g −1, following the order of increased concentration of HA, FA, and TPA. The formation of ternary complex and the multi-layer adsorption were proposed to explain the significant enhancement adsorption of Cu in the presence of FA and TPA. This study showed that the type and the density of effective functional groups in DOM determined its effects on Cu toxicity and bioavailability to algae. Highlights: Dissolved organic matter (DOM) was divided into three fractions based on polarities. Transphilic acid (TPA) was abundant in hydrophilic groups and aliphatic structures. TPA increased algal internalized Pb by 67–92%, while fulvic acid increased by19–33%. TPA increased the adsorbed Cu in algae to 0.48 mmol g −1 by forming ternary complex. The type of DOM and the density of effective functional groups were the key points.