[Simulation of Water Quality Response of Guishui River Wetland Plants and Water Diversion].

A two-dimensional model MIKE21 coupled with a modified EcoLab module was applied to model the water quality of surface flow wetlands. In the model, vegetation effects, oxygen production, nutrient consumption by microorganisms and vegetation were set in the solutions of hydrodynamic, chemical, and biological processes. Based on the field investigation and measurements in the Guishui River wetland, the model was established for the downstream reaches of the Guishui River and the Sanli River. The model calculated the hydrodynamics and water quality changes by vegetation type and distribution. The model parameters were calibrated and results were validated using the measurements. The concentrations of ammonia nitrogen, phosphate, and total nitrogen at outflow decreased by 14.29%, 33.33%, and 20.00% in the presence of wetland vegetation compared to no wetland vegetation. During water circulation, the flow rate increased by 0.4 m3 ·s-1 at the inlet of Guishui and Sanli rivers, increasing the water level and velocity in some parts of the rivers. The water areas with vegetation in Sanli and Guishui rivers increased by 144.44% and 13.16%, respectively. The concentrations of ammonia nitrogen, phosphate, and total nitrogen at outflow decreased by 35.71%, 50.00%, and 46.67% compared to no wetlands and no circulation. The circulation strengthened the wetland purification function. The wetland vegetation distribution was organically integrated into the model for water quality calculation, which provides the technical support for the water quality response research under comprehensive measures such as river and lake wetland ecological restoration and water conservancy regulation.

[Enhanced Sorption of Cetirizine to Loessial Soil Amended with Biochar].

Biochar could be used as a stabilizer to control the migration and transformation of pollutants in soil and reduce their environmental risks. Cetirizine (CTZ) was selected as a target pollutant to investigate the effect of biochar on sorption characteristics of loessial soil by batch experiments. Biochars were produced from walnut shell at different temperatures and added to soil at different mass ratios. The results indicated that all biochars showed obviously higher sorption capacity than loessial soil. The sorption capacity for CTZ was obviously enhanced by soils amended with biochars produced at 400-700℃, which could be attributed to the increased bulk carbon content and specific surface area (SA). Sorption of CTZ to mixtures, excluding the soils amended with biochar produced at 300℃, was lower than the theoretical value. This could be due to the cross-effect between soil components and biochar. At the same time, the organic matter and native sorbates in soil may block or compete for adsorption sites on biochar surface. Biochars would be helpful to stabilize the loessial soil contaminated with CTZ. However, for relatively low concentration of CTZ in aqueous solution and soils amended with relatively high biochar mass ratio, the sorption capacity of the mixtures could be overestimated theoretically without considering the cross-effect between soil and biochar.

[Effects of Dissolved Organic Matter Fractions Extracted from Humus Soil on Sorption of Benzotriazole in Brown Soil and Black Soil].

Dissolved organic matter (DOM) affects the sorption behavior of organic pollutants in soils. In this study, bulk DOM (marked as DOMbulk) was extracted from natural humus soil and divided into five individual fractions by XAD-8 resin and anion/cation exchange resins based on their hydrophobicity-hydrophilicity. The isolated DOM fractions were characterized by FTIR, elemental analysis, UV spectrophotometer and potentiometric titration. Batch experiments were conducted to investigate the effects of different fractions of DOM on sorption of benzotriazole (BTA) in two Chinese reference soils (brown soil and black soil). Proportions of hydrophobic acid (HOA), hydrophobic neutral (HON), hydrophilic acid (HIA), hydrophilic base (HIB) and hydrophilic neutral (HIN) in DOMbulk were 61%, 17%, 6%, 2% and 14%, respectively. Sorption affinity of BTA and DOM in black soil was greater than that in brown soil, which was attributed to the higher organic carbon (OC) content of black soil as compared to that of brown soil. Brown soil had higher normalized distribution coefficient Koc of sorbed DOM fractions than black soil, because brown soil has a greater proportion of clay and silt, which play important roles in sorption of DOM fractions. Dialysis-bag experiments demonstrated that binding coefficient between each isolated DOM fraction and BTA in solution was very weak. The reason is that the binding sites of DOM are occupied by water molecules in solution. Among the isolated DOM fractions, HIN showed the strongest sorption affinity in both soils, which increased OC content and consequently produced new sorption sites in soils. The enhanced sorption effect from new sorption sites was greater than that from competitive sorption between BTA and HIN. On a whole, HIN enhanced the sorption of BTA in soil. HOA and HON inhibited the sorption of BTA in soils. Because the sorption of hydrophobic fractions, especially HON, in soils was less than that of other fractions, competitive sorption between hydrophobic fractions and BTA was the main mechanism. DOMbulk that consists of 78% hydrophobic fractions had similar effects with hydrophobic fractions on sorption of BTA in two soils.

[Evaluating Biochar-Water Sorption Coefficients of Pharmaceutically Active Compounds by Using a Linear Free Energy Relationship].

A linear free energy relationship (LFER) approach was used to predict the sorption coefficients of pharmaceutically active compounds (PhACs) to commercial biochar from aqueous solution, and to investigate the contributions of different intermolecular interactions in the overall sorption process. 14 PhACs with diverse functional groups (carboxyl, hydroxyl and nitrogenous heterocyclic) were selected as sorbates. All isotherm data of PhACs sorption to commercial rice straws biochar (carbonization temperature: 400-500℃, 200 mesh) could be well fitted by the Freundlich equation. The established LFER model could predict the value of sorption coefficient lgKd,activity at arbitrary levels of chemical saturation. The values of multiple correlation coefficient (R2=0.93), standard error (SE=0.23), F-statistic (268), leave-one-out cross validation (QLOO2=0.90), external cross validation correlation coefficient (QEXT2=0.92) indicated that the model was stable and of high predictive ability. The calculated results of the LFER model showed that, at lower sorbate concentration, sorption was dominated by the positive effect of cavity and the negative effect of sorbate capability of electron donation.