Yaling Su

Effect of water composition on TiO2 photocatalytic removal of endocrine disrupting compounds (EDCs) and estrogenic activity from secondary effluent

The effect of inorganic ions and dissolved organic matter (DOM) on the TiO(2) photocatalytic removal of estrogenic activity from secondary effluents of municipal wastewater treatment plants was investigated. The presence of HPO(4)(2-), NH(4)(+), and HCO(3)(-) resulted in a significantly negative impact on the photocatalytic removal of estrogenic activity from synthetic water due to their strong adsorption on the surface of TiO(2). However, only a weak impact was noted during photocatalytic removal of estrogenic activity from secondary effluent with these ions added, since the presence of DOM in real wastewater played a more important role in inhibiting photocatalytic removal of estrogenic activity than inorganic ions. By investigating the effect of different DOM fractions on photocatalytic removal of estrogenic activity, polar compounds (PC) were found to cause a temporary increase in estrogenic activity during TiO(2) photocatalysis. Fluorescence spectroscopy and molecular weight (MW) analysis on secondary effluent spiked with PC during TiO(2) photocatalysis suggest that large MW organic matter (>4.5kDa) in secondary effluent, such as humic/fulvic acid, not only could play an important role in inhibiting photocatalytic removal of estrogenic activity but also is responsible for the temporary increase in estrogenic activity during the same process.

Photodecomposition of 4-chlorophenol by reactive oxygen species in UV/air system.

In this article, the photo-degradation of 4-chlorophenol (4-CP) under UV irradiation was studied with focus on the photodecomposition of 4-CP by reactive oxygen species (ROS). 4-CP underwent much faster and more complete degradation in UV/air system than in UV/N(2) system. In UV/air system, the addition of t-butanol, a well-known (•)OH scavenger, significantly impeded the degradation of 4-CP. In the presence of t-butanol, the tendencies for the degradation of 4-CP and the formation of intermediates in UV/air system were very similar to those in UV/N(2) system. In UV/air system, 4-CP was degraded by two pathways, direct photolysis by absorbing the photons and the oxidation via •OH. The contribution of direct photolysis and the oxidation via •OH to 4-CP decomposition were 17.2% and 82.8%, respectively based on the apparent kinetic constants. Hydrogen peroxide, which could produce •OH through photolysis, was formed in UV/air system. It was shown that dissolved oxygen, organic matter in excited state and hydrogen ion are all necessary for the formation of hydrogen peroxide. The formation mechanism of H(2)O(2) was proposed based on experimental evidence.

Sedimentary lipid biomarker record of human-induced environmental change during the past century in Lake Changdang, Lake Taihu basin, Eastern China

During the past hundred years, the Lake Taihu basin has been greatly impacted by human interventions. The undesirable changes in water quality of lakes, presumably caused by the human activities, remain relatively undescribed in this area. In order to investigate these anthropogenic effects, a 210Pb dated sediment core from a relatively small lake in the upper reaches of Lake Taihu known as Lake Changdang was subject to a detailed lipid biomarker study and other geochemical analyses including quantification of biogenic silica (BSi), nutrients and heavy metals. Based on the results, the recent environmental history of Lake Changdang can be divided into three periods. The first period from approximately 1906 to 1950, represents a natural state, with minimal anthropogenic impact on the lake. Human induced environmental change is recorded in the following stage, ca. 1950-1982, during which the trophic status of the lake increased slightly in response to inputs of agricultural waste and nitrogen (N) and phosphorus (P) based fertilizers. In particular, the signs of eutrophication during this phase accelerated from ca. 1973, perhaps owing to large-scale using phosphate based chemical fertilizer around the lake at the time. A second phase of nutrient input in the most recent stage, ca. from 1982 to 2016, initiated by wastewater discharge from rapid urbanization and industrialization of the catchment, greatly enhanced the nutrient level in the lake. However, the central zone of the lake has yet to reach a phytoplankton-dominated stable state, with both algae and aquatic macrophytes tracking an increased trend in productivity driven by intermediate nutrient levels in the water of this zone.

Comparison of bacterial growth in response to photodegraded terrestrial chromophoric dissolved organic matter in two lakes

Terrestrial chromophoric dissolved organic matter (CDOM) could subsidize lake food webs. Trophic state and altitude have a pronounced influence on the CDOM concentration and composition of a lake. The impact of future changes in solar radiation on high-altitude lakes is particularly alarming because these aquatic ecosystems experience the most pronounced radiation variation worldwide. Photodegradation experiments were conducted on terrestrial CDOM samples from oligotrophic alpine Lake Tiancai and low-altitude eutrophic Lake Xiaohu to investigate the response of bacterial growth to photodegraded CDOM. During the photo-irradiation process, the fluorescent CDOM intensity evidently decreased in an inflowing stream of Lake Tiancai, with the predominance of humic-like fluorescence. By contrast, minimal changes were observed in the riverine CDOM of Lake Xiaohu, with the predominance of protein-like fluorescence. The kinetic constants of photodegradation indicated that the degradation rate of terrestrial (soil) humic acid in Lake Tiancai was significantly higher than that in Lake Xiaohu (p<0.001). Soil humic and fulvic acids irradiated in the simulated experiment were applied to incubated bacteria. The specific growth rate of bacteria incubated with soil humic substances was significantly higher in Lake Tiancai than in Lake Xiaohu (p<0.05). Furthermore, the utilizing rate of dissolved oxygen (DO) confirmed that the DO consumption by bacteria incubated with terrestrial CDOM in Lake Tiancai was significantly greater than that in Lake Xiaohu (p<0.05). In summary, the exposure of terrestrial CDOM to light significantly enhances its availability to heterotrophic bacteria in Lake Tiancai, an oligotrophic alpine lake, which is of importance in understanding bacterial growth in response to photodegraded terrestrial CDOM for different types of lakes.

Geochemical records of anoxic water mass expansion in an oligotrophic alpine lake (Yunnan Province, SW China) in response to climate warming since the 1980s

In order to elucidate the effect of recent warming, we studied lipid biomarkers and trace elements in a dated sediment core from Lake Heihai, a small, deep, and ultraoligotrophic alpine lake in Yunnan Province (SW China), being only marginally affected by anthropogenic activities. The variation in lipid biomarkers (such as 10-methyl-C16:0 fatty acid (FA), iso-branched C15 (i-C15) and anteiso-branched C15 (ai-C15) FA, and tetrahymanol) suggests a rapid productivity increase in sulfate reducing bacteria and ciliates since 1980, likely reflecting expansion of the hypolimnion anoxia and a prolonged duration of an oxic–anoxic chemocline in the water column. The concentrations of element molybdenum (Mo) in pre-1980 sediments approach the values in average crust. After 1980, the concentration increased, reaching levels approximately sixfold higher than the initial abundances. This likely reflects a high authigenic Mo deposition when the bottom water was more anoxic and enrichment in H2S. The suggested spatial and temporal expansion of the anoxic bottom water since 1980 was probably a response to the regional climate warming, resulting in stronger water column stratification and terrestrial grass inputs to the lake, and thus higher dissolved oxygen (DO) loss in hypolimnion.

Tantalum (oxy)nitrides nanotube arrays for the degradation of atrazine in vis-Fenton-like process

In order to overcome the limitation of the application of nanoparticles, tantalum (oxy)nitrides nanotube arrays on a Ta foil were synthesized and introduced in vis (visible light)-Fenton-like system to enhance the degradation of atrazine. At first, the anodization of tantalum foil in a mild electrolyte solution containing ethylene glycol and water (v:v=2:1) plus 0.5wt.% NH(4)F produced tantala nanotubes with an average diameter of 30nm and a length of approximately 1μm. Then the nitridation of tantala nanotube arrays resulted in the replacement of N atoms to O atoms to form tantalum (oxy)nitrides (TaON and Ta(3)N(5)), as testified by XRD and XPS analyses. The synthesized tantalum (oxy)nitrides nanotubes absorb well in the visible region up to 600nm. Under visible light, tantalum (oxy)nitrides nanotube arrays were catalytically active for Fe(3+) reduction. With tantalum (oxy)nitrides nanotube arrays, the degradation of atrazine and the formation of the intermediates in vis/Fe(3+)/H(2)O(2) system were significantly accelerated. This was explained by the higher concentration of Fe(2+) and thus the faster decomposition of H(2)O(2) with tantalum (oxy)nitrides nanotubes. In addition, tantalum (oxy)nitrides nanotubes exhibited stable performance during atrazine degradation for three runs. The good performance and stability of the tantalum (oxy)nitrides nanotubes film with the convenient separation, suggest that this film is a promising catalyst for vis-Fenton-like degradation.