基于习性和食物网的白洋淀大型底栖动物群落恢复研究

白洋淀由于长期受人类活动影响,部分区域内源污染严重.针对该类区域,"十三五"水专项开展了生态清淤试点工程以实现内源治理.在清淤过程中底栖生物容易遭到严重破坏,与之密切联系的食物网受到影响.在沉水植物补种成功后,如何科学地恢复底栖动物群落并维持长效稳定,急需寻求解决方案.本研究于2018年对白洋淀大型底栖动物群落进行调查,根据调研结果、习性特征和食物网模型,提出了受损后大型底栖动物群落恢复方案.研究发现,春季优势种为螺类软体动物和虾类甲壳类动物,夏季和秋季为螺类软体动物和昆虫类摇蚊幼虫.全年主要优势种为中华圆田螺、中国圆田螺、羽摇蚊和大红德永摇蚊.通过食物网模型计算,确定了软体动物是2010年和2018年的关键功能组.因此,综合优势种和关键种,底栖动物群落恢复物种主要选择虾类、螺类和摇蚊幼虫.根据底栖动物的习性,确定甲壳动物和摇蚊幼虫以自然恢复为主,螺类以人工恢复为主的恢复方式.针对螺类关键物种,根据2018年调研生物量、工程经验值和生态容量综合确定其恢复投加量合理范围.通过以上研究,建立了基于食物网成熟度和稳定性的底栖动物群落恢复优化调控方案,为受损底栖动物群落的恢复提供借鉴.     

Remediation of arsenic contaminated soil by sulfidated zero-valent iron

• Sulfidation significantly enhanced As(V) immobilization in soil by zerovalent iron. • S-ZVI promoted the conversion of exchangeable As to less mobile Fe-Mn bound As. • Column test further confirmed the feasibility of sulfidated ZVI on As retention. • S-ZVI amendment and magnetic separation markedly reduced TCLP leachability of As. In this study, the influences of sulfidation on zero-valent iron (ZVI) performance toward As(V) immobilization in soil were systemically investigated. It was found that, compared to unamended ZVI, sulfidated ZVI (S-ZVI) is more favorable to immobilize As(V) in soil and promote the conversion of water soluble As to less mobile Fe-Mn bound As. Specifically, under the optimal S/Fe molar ratio of 0.05, almost all of the leached As could be sequestrated by>0.5 wt.% S-ZVI within 3 h. Although the presence of HA could decrease the desorption of As from soil, HA inhibited the reactivity of S-ZVI to a greater extent. Column experiments further proved the feasibility of applying S-ZVI on soil As(V) immobilization. More importantly, to achieve a good As retention performance, S-ZVI should be fully mixed with soil or located on the downstream side of As migration. The test simulating the flooding conditions in rice culture revealed there was also a good long-term stability of soil As(V) after S-ZVI remediation, where only 0.7% of As was desorbed after 30 days of incubation. Magnetic separation was employed to separate the immobilized As(V) from soil after S-ZVI amendment, where the separation efficiency was found to be dependent of the iron dosage, liquid to soil ratio, and reaction time. Toxicity characteristic leaching procedure (TCLP) tests revealed that the leachability of As from soil was significantly reduced after the S-ZVI amendment and magnetic separation treatment. All these findings provided some insights into the remediation of As(V)-polluted soil by ZVI.     

Degradation characteristics and metabolic pathway of 4-nitrophenol by a halotolerant bacterium Arthrobacter sp. CN2

Arthrobacter sp. strain CN2, capable of degrading 4-nitrophenol, was isolated from activated sludge. Degradation of 4-nitrophenol was optimized at pH 7.7, 30?°C, and 0.53% of glucose. Salt tolerance of 4-nitrophenol degradation was as high as 6% (w/v). Several biodegradation intermediates were identified and quantified by high-performance liquid chromatography and mass spectrometry. 4-Nitrocatechol is involved in the degradation of 4-nitrophenol by CN2. Scale-up of 4-nitrophenol degradation was conducted in a bioreactor with different salinity. When the salinity was below 7%, the degradation rate of 4-nitrophenol was above 90% (100 mg L^?1, 3 L).     

Numerical study of wave–current–vegetation interaction in coastal waters

Research on interactions among wave, current, and vegetation has received increasing attention. An explicit depth-averaged hydrodynamic model coupled with a wave spectral model (CMS-wave) was proposed in this study in order to simulate the wave and wave-induced current in coastal waters. The hydrodynamic model was based on the finite volume method while the intercell flux was computed by employing the Harten–Lax–van Leer approximate Riemann solver to investigate the dry-to-wet interface, and the drag force of vegetation was modeled as the sink terms in the momentum equations. The CMS-wave model was used to investigate the non-breaking and the breaking random waves propagation in vegetation fields. Afterwards, an empirical wave energy dissipation term with plant effect was derived to represent the resistance induced by aquatic vegetation in the wave-action balance equation. The established model was calibrated and validated with both the experimental and field data. The results showed that the wave height decreased significantly along the wave propagation direction in the presence of vegetations. The sensitivity analysis for the plant density, the wave height, and the water depth were performed by comparing the numerical results for the wave height attenuation. In addition, wave and wave-induced current through a finite patch of vegetation in the surf zone were investigated as well. The strong radiation stress gradient could be produced due to the variation of the energy dissipation by vegetation effect in the nearshore zone, which impacted the direction and amplitude of the longshore current. The calculated results showed that the coupling model had good performance in predicting wave propagation and the current over vegetated water regions.     

Flow structure and turbulence characteristics downstream of a spanwise suspended linear array

Laboratory experiments are conducted to quantify the mean flow structure and turbulence properties downstream of a spanwise suspended linear array in a uniform ambient water flow using Particle Tracking Velocimetry. Eighteen experimental scenarios, with four depth ratios (array depth to water column depth) of 0.35, 0.52, 0.78, and 0.95 and bulk Reynolds number (length scale is the array depth) from 11,600 to 68,170, are investigated. Three sub-layers form downstream of the array: (1) an internal wake zone, where the time-averaged velocity decreases with increasing distance downstream, (2) a shear layer which increases in vertical extent with increasing distance downstream of the array, and the rate of the increase is independent of the bulk Reynolds number or the depth ratio, and (3) an external wake layer with enhanced velocity under the array. The location of the shear layer is dependent on the depth ratio. The spatially averaged and normalized TKE of the wake has a short production region, followed by a decay region which is comparable to grid turbulence decay and is dependent on the depth ratio. The results suggest that the shear layer increases the transfer of horizontal momentum into the internal wake zone from the fluid outside of the array and that the turbulence in the internal wake zone can be modeled similarly to that of grid turbulence.     

Comparison of growth and lipid accumulation properties of two oleaginous microalgae under different nutrient conditions

This study compared the growth and lipid accumulation properties of two oleaginous microalgae, namely, Scenedesmus sp. LX1 and Chlorella sp. HQ, under different nutrient conditions. Both algal species obtained the highest biomass, lipid content and lipid yield under low-nutrient conditions （mBGll medium）. The biomass, lipid content and lipid yield of Scenedesmus sp. LX1 were 0.42g·L^-1, 22.5% and 93.8mg·L^-1, respectively. These values were relatively higher than those of Chlorella sp. HQ （0.30g·L^-1, 17.1% and 51.3mg·L^-1, respectively）. These algae were then cultivated in an SE medium that contained more nutrients; as a result, the biomass and lipid yield of Scenedesmus sp. LX1 reduced more significantly than those of Chlorella sp. HQ. Opposite results were observed in lipid and triacylglycerols （TAGs） contents. The cell sizes of both algal species under low-nutrient conditions were larger than those under high-nutrient conditions. Chlorella sp. HQ cells did not aggregate, but Scenedesmus sp. LX1 cells flocculated easily, particularly under low-nutrient conditions. In summary, low-nutrient conditions favour the growth and lipid production of both algae, but Scenedesmus sp. LX1 outperforms Chlorella sp. HQ.     

还原铁法处理印染废水生化出水及原理

采用还原铁粉处理印染废水生化出水,以ADMI7.6作为主要测试指标,考察铁粉投加量、反应时间以及进水pH对出水水质的影响,并研究在此过程中铁粉还原作用和混凝絮凝作用对整体效果的贡献比.结果表明,条件1:铁粉投加量=1.0 g.L-1,反应时间150 min,进水pH 2;条件2:铁粉投加量1.0 g.L-1,反应时间150 min,进水pH 3.条件1时,ADMI7.6去除率达到80%,但铁泥量大,酸碱消耗大,在此反应条件下,铁粉还原去除40%,混凝絮凝去除60%;条件2时,ADMI7.6去除率达到50%左右,产铁泥量小,经济合理;在此反应条件下,铁粉还原去除55%—63%左右,混凝絮凝去除37%—45%左右.经XAD8/XAD4树脂联用,分析疏水酸、非酸疏水物质、弱疏水物质及亲水物质4类有机物的去除情况表明,条件1时,能够高效去除非酸疏水物质,去除率为95%,对于疏水酸以及弱疏水物质也有一定的去除效果;条件2时,对4类有机物去除均有一定作用,但对于非酸疏水物质以及疏水酸的去除效果要略差于条件1.     

光催化氧化（UV+TiO2）法处理印染废水生化出水及其各类有机物去除

采用UV+TiO2光催化氧化法处理印染废水生化出水,考察了反应时间、TiO2投加量以及初始pH对反应的影响,结果表明,TiO2投加量800 mg·L-1,反应时间8 h,反应pH为原水pH(6.5～8.0),在此操作条件下,ADMI7.6、DOC和COD的去除率分别为86%、20%及46%;选取两组反应条件,对其进出水采用XAD-8/XAD-4树脂联用技术,分析疏水酸、非酸疏水物质、弱疏水物质及亲水物质4类有机物的去除情况,结果表明,UV+TiO2光催化氧化处理工艺都能够长期有效去除印染废水生化出水中的弱疏水物质、疏水物质和非酸疏水物质引起的色度.     

汶川大地震宏观震中问题的讨论

采用大地震诱发崩塌滑坡特点与地面破坏程度相结合,以及极震区几何中心方法,定性判定了汶川大地震的宏观震中位置。判定结果是汶川大地震应该有2个宏观震中,一是映秀镇牛圈沟为映秀极震区宏观震中,坐标位置:31.045 6°N,103.455 6°E;二是北川老县城为北川极震区宏观震中,坐标位置:31.863 7°N,104.361 0°E。两种判定方法相比,前者更符合山区特殊地质地貌环境下的地震破坏规律。