Search

There is limited knowledge available on metalloid biosorption by freshwater algae. In this study, biosorption properties of anionic Sb(OH) by naturally occurring cyanobacteria Microcystis were investigated as a function of initial pH, biosorbent dosage, contact time, and addition sequences of competitive ions, and their binding mechanisms were discussed. The biosorption process was fast and equilibrium was reached at 2 h. Sb(V) biosorption decreased with the increase of pH and the optimum pH range was 2.5-3.0, which corresponded with the changes of surface charges of the cell wall of Microcystis. The biosorption data satisfactorily followed the Freundlich model. The simultaneous addition of HPO and Ca enhanced Sb(V) biosorption, while NO greatly inhibited the biosorption, compared with single Sb(V) addition. The initial addition of the competitive ions reduced Sb(V) biosorption at higher Sb(V) concentrations, compared with simultaneous addition. A fraction of biosorbed Sb(V) was replaced by the competitive ions which were added subsequently, and the exchange only occurred at higher concentrations of Sb(V). 1.0 mol/L HCl demonstrated the highest desorption efficiency. Speciation analyses indicated that no reduction of Sb(V) into Sb(III) occurred. Based on the results of zeta potential and attenuated total reflection infrared spectroscopy spectra, Sb(OH) bound to the biomass through electrostatic attraction and surface complexation, and amino, carboxyl, and hydroxyl groups were involved in the biosorption process. The study suggest that Microcystis from cyanobacteria blooms could be used as a potential biosorbent to remove Sb(V) from effluents at environmentally relevant concentrations (≤10.0 mg/L). [ABSTRACT FROM AUTHOR]

Nafine Chemical Industry Group Co. Ltd. extracted inorganic salts from the saline lake of Shanxi Yuncheng, China. Because of the complexity of component and the high content of organic matters in the saline lake water, the purity of the inorganic salts was influenced directly. As a result, the organic matters in the saline lake water were needed to be removed. In order to solve this problem, different water treatment processes were utilized to remove the organic matters in saline lake water, but some valuable metal ions would lose, especially the magnesium ion in water treatment processes. The purpose of this paper is to study the treatability of high concentrated organic matters in saline water by O2/H2O2 oxidation, O2/H2O2 oxidation followed coagulation and activated carbon adsorption respectively, and the mechanisms of magnesium ion loss were analyzed. The results showed that O2/H2O2 oxidation can change the structure of organic matter and increase the content of carboxylic groups in organic matters which resulted in the complexation with magnesium ion. So that magnesium ion would be lost along with the removal of organic matters by coagulation or activated carbon adsorption following oxidation. However, it indicated that the magnesium ion loss could be decreased effectively through pH adjusting after oxidation. [ABSTRACT FROM AUTHOR]

Abstract: The role of colloids in estuarine and marine systems has been studied extensively in recent years, whereas less is known about the polluted freshwater system. Yongdingxin River is one of the major recipients of industrial effluents in Tianjin. This article evaluates the role of colloids in controlling geochemical behavior of Cu, Zn, Fe, Mn, Hg and Cr at the confluences between Yongdingxin River and its major tributaries Beijing Drainage River, Jinzhong River and Beitang Drainage River. Based on the distribution of metal partitioning among particulate (>0.22μm), colloidal (1kDa to 0.22μm) and truly dissolved (<1kDa) fractions, the metals can be assigned to the following groups: Group 1 – organic colloidal pool-borne elements Cu and Cr; Group 2 – inorganic colloidal pool-borne metals Fe and Mn; Group 3 – Zn and Hg characterized by varying complexation patterns. The distribution of metal partitioning among particulate, colloidal and truly dissolved fractions was influenced by anthropogenic input. In addition, the theoretical concentrations of elements in case of conservative mixing between the waters of Yongdingxin River and the waters of its tributaries were compared with the measured values to evaluate the geochemical role of colloids. The result showed that all of the metals presented a non-conservative mixing behavior. Addition of colloids resulted in the removal of metals from the water column to bed sediment during river water mixing, which was furthermore confirmed by the similar partition coefficient of metal concentration between colloid and sediment. [Copyright &y& Elsevier]

Abstract: Although the sorption mechanism of hydrophobic organic pollutants on soils or sediments has been widely studied, the effects of coexisting heavy metals are seldom reported, especially the role of dissolved organic carbon (DOC) in sorption interactions involving heavy metals. This paper investigates the sorption interactions of phthalate esters (diethyl phthalate, DEP, and di-n-butyl phthalate, DnBP) and copper on Yellow River sediment in the presence of DOC. The results indicate that the sorption hardly varies for DEP but increases up to 20% for DnBP as the copper concentration increases in a water-sediment system with extremely low concentration of DOC. The copper-induced sorption of DnBP could be due to its complexation with copper, as well as its hydrophobicity. In a water-sediment system with the addition of 6.34mgl−1 of commercial humic acid (HA), the sorption of DEP is decreased by up to 37%, and that of DnBP is enhanced by up to 41%, as copper is gradually added. This finding is also consistent with the results for a river water-sediment system containing 8.1mgl−1 natural DOC. The copper-influenced sorption of DEP and DnBP are found to be due to the binding of copper to DOC that leads to the configuration change of DOC and thus to its enhanced sorption to sediment. By using polarograph and fluorescence spectrograph techniques, the complexation competition among coexisting phthalates, copper and DOC is examined. The resulting data confirm the significant role of DOC in sorption interactions. [Copyright &y& Elsevier]

The article presents abstracts of several studies on environmental geochemistry. Some of the abstracts presented include "Biogeochemical Cycling of Nutrients in Karstic Catchments, Southwestern China: Linkages to Changes of Eco-Environments," by Congqiang Liu and "Emerging Organic Contamination in China," by Guibin Jiang and colleagues.

The complexation constants for copper associated with different natural organic ligands, including dissolved organic carbon (DOC) extracted from water, water soluble organic carbon (WSOC), fulvic acid (FA) and humic acid (HA) from soil, were determined and then compared based on discrete single site model. Both ion-selective electrode (ISE) and anodic stripping voltammetry were used to determine the content of free copper ions, while the relative number of complexation sites was estimated using a fluorescence quenching (FQ) at the same time. ISE proved to be the most applicable technique when the concentration of copper was above 10−7 mol l−1. The log k values for two WSOC sample sites (Song Ziyuan and Xin Niangtan) were 4.64 and 4.66; higher than both the DOC and HA values yet lower than the FA values, which were unusually high due to unavoidable pollution from the cation exchange resin used during the purification process. Binding affinities between the copper ions and the organic ligands obtained from streams in Yong Wei (DOC) and Song Ziyuan (WSOC) were influenced by pH, ion strength, and reactant concentration. Values for log k increased with increases in pH (ion strength of 0.1 N). At pH 4, the log k values decreased with increases in the supporting electrolyte concentration and total copper ion additions. [Copyright &y& Elsevier]

Ge and Si differ strongly in their biogeochemical behavior due to the differences in binding capacity to organic matter. The mechanisms of soil organic matter affecting the mobility and bioavailability of Ge in soil-plant system remain unclear. This work aimed to investigate the soil Ge fractions and Ge binding to humic substances in paddy soil. Paddy soil samples taken from Changxing County, Zhejiang Province, China, were investigated by the sequential extraction method. Humic acid (HA) and fulvic acid (FA) isolated from paddy soils were characterized by Fourier transform infrared spectrometry (FT-IR) and 3-dimensional excitation-emission matrix (3D-EEM). The effect of humic substances on the binding of Ge was studied by fluorescence-quenching titration. Results showed that residual Ge was the dominant fraction in soil (up to 85%). The mobile Ge, organic matter bound Ge and easily reduceable compounds bound Ge accounted for approximately 10% of soil TGe and may represented critical labile pools of soil Ge. Organic matter bound Ge significantly correlated (r = 0.56, p < 0.01) with rice Ge concentrations. The fluorescence of HA and FA was markedly quenched by the addition of Ge. The conditional stability constant of HA-Ge complexes was larger than that of FA-Ge complexes, and the complexation capacity of HA-Ge complexes was lower than that of FA-Ge complexes. Humic substances played a dual role in affecting the behavior of dissolved Ge in paddy soil. HA formed stable complexes with Ge and tended to sequester Ge, while FA formed soluble and unstable complexes with Ge and tended to act as a Ge carrier in soil-plant system.

Natural dissolved organic matter (DOM) produced in algal blooms and overgrowths of macrophyte changes the elimination and ecotoxicity of estrogens in freshwater lakes. The complexation of 17α-ethinylestradiol (EE2) and various DOMs, including the water- and sediment-derived DOMs from the algal-dominant zone in Lake Taihu (TW and TS, respectively) and the macrophyte-dominant zone in Poyang Lake (PW and PS, respectively), and the humic acid (HA), was investigated along with the subsequent effects on EE2 biodegradation. Dialysis equilibrium experiments showed that binding to DOM significantly decreased the freely soluble concentrations of EE2. The binding capacity of the five DOMs followed the order of PW < TW < PS ≈ TS < HA. A negative correlation was found between the organic-carbon-normalized sorption coefficient (logK DOC ) and the absorption ratio (E 2 /E 3 ) of DOM, indicating that the large sized, aromatic molecules were involved in the complexation. The reduced freely soluble concentrations of EE2 did not inhibit its biodegradation by an EE2-degrading strain, Rhodobacter blasticus. Conversely, the autochthonous-dominated water-derived DOMs stimulated a more extensive biodegradation of EE2 than the sediment-derived DOMs, and the existence of HA resulted in the smallest increase in EE2 biodegradation. The promoting effect was associated with the increased concentration, activity, and transforming rate of R. blasticus by the bioavailable components in DOM. The present study suggests that the significant impact of natural DOM should be fully considered when assessing the fate and ecological risks of estrogens in eutrophic waters., (Copyright © 2019 Elsevier Ltd. All rights reserved.)