Approach deliberation for source identification of sedimentary organic matters via comparing freshwater lakes with multi-ecotypes.

Despite of the importance of understanding the sediment quality for lacustrine management, the source evaluation of sedimentary organic matter (SOM) in freshwater lakes is still insufficient. In this study, two shallow eutrophic lakes of Lake Taihu, China and Lake Izunuma, Japan were systematically investigated. Results of fatty acid profiles demonstrated that a wide range of organic matters, varying ecotypically, was inputted into the sediments of both lakes. Interestingly, there was a strong contribution from terrestrial plants to the sediments across ecotypes, with an approximate input from bacteria, and a relatively minor input from microalgae mainly included cyanobacteria, green algae, diatom and dinoflagellates. In addition, isotopic mixing model depicted a complementary picture that a significant, but spatially variable, amount of organic matter was derived from emergent and floating-leaf plants of Phragmites, Nelumbo, Nymphoides and Trapa L in Lake Izunuma. A general indicator selection procedure for the source assignments of SOM in freshwater ecosystems was therefore proposed: fatty acids could be a valid biomarker when the potential sources are unknown or unavailable; stable isotopes could be an effective supplement approach when assessing the special or defined organic sources.

Effects of bacterial activity on estrogen removal in nitrifying activated sludge.

The effects of bacterial activity on the degradation of estrone (E1), estradiol (E2), estriol (E3) and ethinylestradiol (EE2) in nitrifying activated sludge (NAS) were studied with different substrates and organic loading rates (OLRs) and low temperature conditions. Heterotroph was shown to have utilized glucose prior to E1 for metabolism. The co-metabolism of ammonia oxidizing bacteria (AOB) dominated the degradation of E1, E2 and EE2 in NAS. The higher the organic loading, the higher the rate of organic matter transformation, with less ammonia oxidation and less degradation of E1, E2 and EE2. The degradation of E3 in NAS was shown to be largely due to heterotroph metabolism. On the basis of the difference of apparent activity between heterotroph and AOB at 4 degrees C, the process of estrogen degradation via the co-metabolism of AOB was able to be identified.

A thermodynamic analysis on adsorption of estrogens in activated sludge process.

The adsorption behaviors of estrone (E1), 17beta-estradiol (E2), estriol (E3), 17 alpha-ethinylestradiol (EE2), and equol were studied with a deactivated sludge subjected to heat treatment at 80 degrees C for 30 min. The heat-treatment hardly changed the adsorption features of activated sludge (AS). The adsorption equilibrium of all estrogens was approached within 10 min at 20 degrees C, and a high removal of estrogens was achieved simultaneously. The equilibrium data were well fitted by a Freundlich isotherm. The adsorption behaviors of E1, E2, E3 and EE2 in the AS system were independent of their Kow values. Thermodynamic analysis revealed that the adsorption behaviors of E1, E2, E3 and EE2 could be considered as an exothermic, physical and reversible process, resulting in their higher adsorption capacities at lower temperature. Regarding equol, its adsorption was an endothermic, chemical and irreversible process.

Phragmites australis: a novel biosorbent for the removal of heavy metals from aqueous solution.

Reed (Phragmites australis), a commonly used macrophyte in the wetlands constructed for water purification, was investigated as a new biosorbent for the removal of Cu(2+), Cd(2+), Ni(2+), Pb(2+) and Zn(2+) from aqueous solution. The metal adsorption capacity of reed biomass was improved significantly by water-wash, base- and acid-treatment. The maximum sorption of NaOH-pretreated reed biomass was observed near neutral pH for Cu(2+), Cd(2+), Ni(2+) and Zn(2+), while that for Pb(2+) was from an acidic range of pH 4.0 or higher. The maximum metal adsorption capacity on a molar basis assumed by Langmuir model was in the order of Cu(2+)>Ni(2+)>Cd(2+)>Zn(2+)>Pb(2+). Reed biosorbent showed a very high adsorption affinity value, which helps predict its high ability to adsorb heavy metals at low concentration. Desorption of heavy metals and regeneration of the biosorbent was attained simultaneously by acid elution. Even after three cycles of adsorption-elution, the adsorption capacity was regained completely and the desorption efficiency of metal was maintained at around 90%.

Feedback of threshold via estimating sources and composition of sedimentary organic matter across trophic gradients in freshwater lakes.

The quantity and quality of sedimentary organic matter (SOM) in relation to material and energy flows are crucial for understanding the current state and future development of lake systems, yet, characterization of organic matter sources and assessment of their relative contributions in different trophic-state lakes caused by anthropogenic impacts are scarcely known. In this study, for obtaining information concerning the source of SOM and its compositional diversity along different trophic gradients, a total of thirty-one sampling sites from four freshwater lakes located in China and Japan were performed by the molecular level analysis using source-specific fatty acid biomarkers. Results indicated that SOM in these lakes was composed of microalgae-, aquatic plant-, terrestrial plant- and bacteria-derived organic matters based on their fatty acid profiles. The scatter plot matrix exhibited correlations between these sources, however, only terrestrial plant-derived organic carbon was a well predictor for sediment TOC with strong, spatiotemporal dynamics. The source and composition of SOM were evidently influenced by lake trophic state with redundancy analysis. Moreover, increase of lake trophic state led to the relatively higher contribution of aquatic organic matter sources to SOM pool compared with terrigenous sources, as evidenced by significant correlations between the trophic state index [TSI (TP)] and the ratio of terrigenous to aquatic fatty acids (TARFA ratio). Yet, this changing trend became more gradual with higher trophic state and prevented the occurrence of regime shift from allochthonous to autochthonous dominant state by a threshold (0.683) of TARFA ratio. Together, a conceptual diagram was proposed, which highlighted the prevailing state of allochthonous source and implicated sedimentary organics in biogeochemistry cycle within freshwater lakes.

Estrogen removal from treated municipal effluent in small-scale constructed wetland with different depth.

The presence of estrone (E1), 17 beta-estradiol (E2) and 17 alpha-ethynylestradiol (EE2) in sewage treatment work (STW) effluent pose a potential risk to aquatic ecosystem. The objectives of this study were to evaluate the effectiveness of vertical-flow wetland as polishing step of conventional wastewater treatment in the removal of estrogens and to examine the effect of sand depth. The highest removal efficiency of 67.8+/-28.0%, 84.0+/-15.4% and 75.3+/-17.6% for E1, E2 and EE2, respectively, was achieved by the shallowest wetland among three constructed wetlands with different filter layer depth (i.e. 7.5, 30 and 60 cm). Together with the result that the performance of wetlands when operating in unsaturated condition was superior to that when operating in water-saturated condition, it is suggested that maintaining sufficient aerobic circumstance in constructed wetlands was important for estrogens removal. Core sampling indicated that the highest efficiency achieved in extremely shallow wetland might be due partly to the highest root density, besides the superior condition for penetration of oxygen. The adsorbed estrogens in sand accounted for less than 12% of the removed estrogens irrespective of the depth, indicating biotic processes play a major role in the estrogens removal.