Effect of pH on binding of pyrene to hydrophobic fractions of dissolved organic matter(DOM) isolated from lake water

In order to better understand the compositional and structural complexity of dissolved organic matter(DOM) macromolecules and provide mechanistic information on the binding of hydrophobic organic contaminants(HOCs) to DOM, we fractionated large amounts of lake water into three hydrophobic DOM-fractions. The variation of the partitioning coef?cients(K_(DOC)) of pyrene at different p H levels was examined by ?orescence quenching titration. Results show that, relative to the more polar acidic DOM-fractions, the hydrophobic neutral fraction exhibits a higher sorption ability to pyrene. Generally, the sorption of pyrene to the three hydrophobic fractions is strongly pH-dependent. The K_(DOC) values of pyrene generally increase with decreasing p H levels, which is especially obvious in the sorption of pyrene to the fulvic acid fractions, suggesting that the binding is controlled by hydrophobic interactions. The mechanisms underlying the binding of pyrene to the hydrophobic fractions were also discussed. Our data are bene?cial to further understanding the binding of HOCs to DOM and how it has been affected,which may result in more accurate predictions of K_(DOC).

Control concept and countermeasures for shallow lakes’eutrophication in China

Research on lake eutrophication in China began in the early 1970s,and many lakes in China are now known to be in meso-eutrophic status.Lake eutrophication has been showing a rapidly increasing trend since 2000.Investigations show that the main reasons for lake eutrophication include a fragile lake background environment,excessive nutrient loading into lakes,excessive human activities,ecological degeneration,weak environmental protection awareness,and lax lake management.Major mechanisms resulting from lake eutrophication include nutrient recycling imbalance,major changes in water chemistry(pH,oxygen,and carbon),lake ecosystem imbalance,and algal prevalence in lakes.Some concepts for controlling eutrophication should be persistently proposed,including lake catchment control,combination of pollutant source control with ecological restoration,protection of three important aspects(terrestrial ecology,lake coast zone,and submerged plant),and combination of lake management with regulation.Measures to control lake eutrophication should include pollution source control(i.e.,optimize industrial structural adjustments in the lake catchment,reduce nitrogen and phosphorus emission amounts,and control endogenous pollution)and lake ecological restoration(i.e.establish a zone-lake buffer region and lakeside zone,protect regional vegetation,utilize hydrophytes in renovation technology);countermeasures for lake management should include implementing water quality management,identifying environmental and lake water goals,legislating and formulating laws and regulations to protect lakes,strengthening publicity and the education of people,increasing public awareness through participation in systems and mechanic innovations,establishing lake region management institutions,and ensuring implementation of governance and management measures.

Effects of overlying water aeration on phosphorus fractions and alkaline phosphatase activity in surface sediment

Microbial activity may influence phosphorus (P) deposit and release at the water sediment interface.The properties of DO (dissolved oxygen),pH,P fractions (TP,Ca-P,Fe-P,OP,IP),and APA (alkaline phosphatase activity) at the water sediment interface were measured to investigate microbial activity variations in surface sediment under conditions of two-month intermittent aeration in overlying water.Results showed that DO and TP of overlying water increased rapidly in the first week and then decreased gradually after 15 day of intermittent aeration.Microorganism metabolism in surface sediment increased pH and decreased DO and TP in the overlying water.After two-month intermittent aeration,APA and OP from surface sediment (0-2 cm) were both significantly higher than those from bottom sediment (6-8 cm) (p < 0.05),and surface sediment Fe-P was transferred to OP during the course of microorganism reproduction on the surface sediment.These results suggest that microbial activity and microorganism biomass from the surface sediment were higher than those from bottom sediment after two-month intermittent aeration in the overlying water.