Distribution and change of DDT and HCH levels in oysters (Crassostrea rivularis) from coast of Guangdong,China between 2003 and 2007

This investigation was undertaken to understand the temporal trend, the spatial distribution and the residue level of dichloro-diphenyl-trichloroethanes (DDTs) and hexachlorobenzenes(HCHs) in bivalves from the coast of the South China in recent years. Jinjiang oysters (Crassostrea rivularis) were sampled from 15 bays along the coast of Guangdong province, China between 2003 and 2007. Gas chromatography with electron capture detector was used to quantify the contents of HCH isomers (α-, β-, γ-, δ-HCH), DDT isomers (p,p′-, o,p′-DDT), p,p′-DDD and p,p′-DDE in the oyster tissues. The results demonstrate that annual level of DDTs in the tissue increase throughout the study, particularly between 2004 and 2006. The DDTs content in the tissue varied significantly among sampling regions and some sampling sites (p < 0.05). On the other hand, the HCHs content was significantly lower than DDTs content in the tissue (p < 0.01), and remain constant among sampling years, sampling regions and sampling sites (p > 0.10). Predominance of isomer form of DDTs and higher ratio of γ-HCH/HCHs at some sites indicated that recent input of DDT and lindane in the coastal waters of Guangdong, which might be caused by dicofol spraying in crop planting and lacquer painting on fisher boat. In the soft tissues of the oysters, the highest content of HCHs was 1.21 ng/g (wet weight), and DDTs levels ranged from 0.11 ng/g to 76.3 ng/g (wet weight), far below the Maximum Residual Limits in China and many developed nations.     

固态发酵法制备优势硝化菌固定化产品的工艺优化

为解决高效菌在工程应用中扩大培养、保存和接种等瓶颈,研究固态发酵法制备焦化废水优势硝化菌固定化产品.以TTC脱氢酶活性法作为固体发酵生物量测定指标,通过液态发酵单因素实验初步确定硝化菌发酵条件,再用响应面法对其固态发酵条件进行优化.结果表明,TTC脱氢酶活性法适合作为表征生物质载体固定化产品生物量的测定方法,不受载体和培养时间的影响,能较好地指示干燥前固态发酵生物量的变化.固态发酵主要影响参数依次为发酵时间、发酵温度、接种量和含水率.发酵时间的最佳值为47 h,发酵温度最佳为29.4℃,接种量的最佳值为9.9 mL/200 mL,最佳含水率为48.9％时,固态发酵固定化产品酶活达到17.091 μg TF/(g·h).与液态发酵参数相比其发酵温度、接种量最佳值接近,但发酵时间由1d延长至2d,产品酶活持平.     

Influence of algal bloom degradation on nutrient release at the sediment–water interface in Lake Taihu, China

Algal bloom could drastically influence the nutrient cycling in lakes. To understand how the internal nutrient release responds to algal bloom decay, water and sediment columns were sampled at 22 sites from four distinct regions of China’s eutrophic Lake Taihu and incubated in the laboratory to examine the influence of massive algal bloom decay on nutrient release from sediment. The column experiment involved three treatments: (1) water and sediment (WS); (2) water and algal bloom (WA); and (3) water, sediment, and algal bloom (WSA). Concentrations of dissolved oxygen (DO), total nitrogen (TN), total phosphorus (TP), ammonium (NH ₄ ⁺ -N), and orthophosphate (PO ₄ ^3? -P) were recorded during incubation. The decay of algal material caused a more rapid decrease in DO than in the algae-free controls and led to significant increases in NH ₄ ⁺ -N and PO ₄ ^3? -P in the water. The presence of algae during the incubation had a regionally variable effect on sediment nutrient profiles. In the absence of decaying algae (treatment WS), sediment nutrient concentrations decreased during the incubation. In the presence of blooms (WSA), sediments from the river mouth released P to the overlying water, while sediments from other regions absorbed surplus P from the water. This experiment showed that large-scale algal decay will dramatically affect nutrient cycling at the sediment–water interface and would potentially transfer the function of sediment as “container” or “supplier” in Taihu, although oxygen exchange with atmosphere in lake water was stronger than in columns. The magnitude of the effect depends on the physical–chemical character of the sediments.     

上海市桃浦垃圾填埋场封场植被的重金属吸收和积累特征

城市垃圾填埋场的生态修复问题越来越受到重视,选择合适的封场植被对生态恢复至关重要。本研究对上海市桃浦垃圾填埋场的土壤和29种优势植物的重金属含量进行检测,结果显示,该填埋埋场土壤呈现Zn和Cd的中度复合污染。在研究的优势植物中,杨树、雪松和夹竹桃吸收Zn的能力较强,杨树、紫薇、金丝桃吸收Cd的能力较强。荆芥表现为重金属Zn的富集型植物;龙葵表现为重金属Cd的富集型植物;麦冬和狗尾巴草则表现为重金属的根部囤积型植物。可综合选择这些植物用于城市垃圾填埋场的植物修复和植被恢复。     

小型燃煤锅炉与燃油(气)锅炉的环境影响及运行费用比较分析

从环境经济学的角度,对一般常用的小型燃煤锅炉与燃油(气)锅炉的环境影响及运行费用进行了比较分析。     

Dynamics of cyanobacterial bloom formation during short-term hydrodynamic fluctuation in a large shallow, eutrophic, and wind-exposed Lake Taihu, China

Short-term hydrodynamic fluctuations caused by extreme weather events are expected to increase worldwide because of global climate change, and such fluctuations can strongly influence cyanobacterial blooms. In this study, the cyanobacterial bloom disappearance and reappearance in Lake Taihu, China, in response to short-term hydrodynamic fluctuations, was investigated by field sampling, long-term ecological records, high-frequency sensors and MODIS satellite images. The horizontal drift caused by the dominant easterly wind during the phytoplankton growth season was mainly responsible for cyanobacterial biomass accumulation in the western and northern regions of the lake and subsequent bloom formation over relatively long time scales. The cyanobacterial bloom changed slowly under calm or gentle wind conditions. In contrast, the short-term bloom events within a day were mainly caused by entrainment and disentrainment of cyanobacterial colonies by wind-induced hydrodynamics. Observation of a westerly event in Lake Taihu revealed that when the 30 min mean wind speed (flow speed) exceeded the threshold value of 6 m/s (5.7 cm/s), cyanobacteria in colonies were entrained by the wind-induced hydrodynamics. Subsequently, the vertical migration of cyanobacterial colonies was controlled by hydrodynamics, resulting in thorough mixing of algal biomass throughout the water depth and the eventual disappearance of surface blooms. Moreover, the intense mixing can also increase the chance for forming larger and more cyanobacterial colonies, namely, aggregation. Subsequently, when the hydrodynamics became weak, the cyanobacterial colonies continuously float upward without effective buoyancy regulation, and cause cyanobacterial bloom explosive expansion after the westerly. Furthermore, the results of this study indicate that the strong wind happening frequently during April and October can be an important cause of the formation and expansion of cyanobacterial blooms in Lake Taihu.     

Atmospheric partitioning and the air–water exchange of polycyclic aromatic hydrocarbons in a large shallow Chinese lake (Lake Chaohu)

The residual levels of polycyclic aromatic hydrocarbons (PAHs) in the atmosphere and in dissolved phase from Lake Chaohu were measured by (GC–MS). The composition and seasonal variation were investigated. The diffusive air–water exchange flux was estimated by a two-film model, and the uncertainty in the flux calculations and the sensitivity of the parameters were evaluated. The following results were obtained: (1) the average residual levels of all PAHs (PAH16) in the atmosphere from Lake Chaohu were 60.85 ± 46.17 ng m⁻³ in the gaseous phase and 14.32 ± 23.82 ng m⁻³ in the particulate phase. The dissolved PAH16 level was 173.46 ± 132.89 ng L⁻¹. (2) The seasonal variation of average PAH16 contents ranged from 43.09 ± 33.20 ng m⁻³ (summer) to 137.47 ± 41.69 ng m⁻³ (winter) in gaseous phase, from 6.62 ± 2.72 ng m⁻³ (summer) to 56.13 ± 22.99 ng m⁻³ (winter) in particulate phase, and 142.68 ± 74.68 ng L⁻¹ (winter) to 360.00 ± 176.60 ng L⁻¹ (summer) in water samples. Obvious seasonal trends of PAH16 concentrations were found in the atmosphere and water. The values of PAH16 for both the atmosphere and the water were significantly correlated with temperature. (3) The monthly diffusive air–water exchange flux of total PAH16 ranged from −1.77 × 10⁴ ng m⁻² d⁻¹ to 1.11 × 10⁵ ng m⁻² d⁻¹, with an average value of 3.45 × 10⁴ ng m⁻² d⁻¹. (4) The results of a Monte Carlo simulation showed that the monthly average PAH fluxes ranged from −3.4 × 10³ ng m⁻² d⁻¹ to 1.6 × 10⁴ ng m⁻² d⁻¹ throughout the year, and the uncertainties for individual PAHs were compared. (5) According to the sensitivity analysis, the concentrations of dissolved and gaseous phase PAHs were the two most important factors affecting the results of the flux calculations.     

Characterization of cadmium (Cd) distribution and accumulation in Tagetes erecta L. seedlings: Effect of split-root and of remove-xylem/phloem

Tagetes erecta has a high potential for cadmium (Cd) phytoremediation. Through several hydroponic experiments, characteristics of ¹⁰⁸Cd distribution and accumulation were investigated in T. erecta with split -roots or removed xylem/phloem. The results showed that ¹⁰⁸Cd transport from roots to aboveground tissues showed the homolateral transport phenomenon in split-root seedlings. ¹⁰⁸Cd content of leaves on the +¹⁰⁸Cd side and the −¹⁰⁸Cd side was not significantly different, which implied that there was horizontal transport of ¹⁰⁸Cd from the +¹⁰⁸Cd side to the −¹⁰⁸Cd side in cut-root seedlings. Like ¹⁰⁸Cd transport, the transport of ⁷⁰Zn was homolateral. Reduction of water consumption in the removed xylem treatment significantly decreased ¹⁰⁸Cd accumulation; whereas, the removed phloem treatment had no significant effect on water consumption, but did decrease ¹⁰⁸Cd accumulation in leaves of the seedlings. The removal of phloem significantly reduced distal leaf ¹⁰⁸Cd content, which was significantly lower than that in the basal leaves in both the split-root and unsplit-root seedlings. Overall, the results presented in this study revealed that the root to aboveground cadmium translocation via phloem is as an important and common physiological process as xylem determination of the cadmium accumulation in stems and leaves of marigold seedlings.     

H2O2协同TiO2光催化处理模拟苯胺废水

采用TiO2光催化处理模拟苯胺废水.实验结果表明,最佳反应条件为:初始苯胺质量浓度10 mg/L,纳米TiO2加入量100 mg/L,光催化反应时间60 min,废水pH 7.5.加入20 mg/L的H2O2协同TiO2光催化处理苯胺废水,光催化反应24 min后,苯胺去除率达99％.H2O2协同TiO2光催化降解苯胺过程符合二级动力学方程.     

前驱体溶液pH对核壳型Cr/CeO2催化剂低温选择性催化氧化脱硝性能的影响

采用一步水热法合成了具有核壳结构的铬铈复合氧化物（Cr/CeO₂）,并将其用于选择性催化氧化（SCO）烟气脱硝,考察了前驱体溶液pH对催化剂低温催化活性的影响。实验结果表明,当前驱体溶液pH为2时制得的催化剂（CrCe2）具有较高的低温SCO活性,其在200 ℃下的NO转化率高达59%。XRD,SEM,BET,UV-Vis,TPD等表征结果显示：核壳结构的生成促进了Cr物种的高分散性,同时Cr的掺杂增大了催化剂的比表面积,从而提高了活性位点的总量;在该系列催化剂中,CrCe2催化剂具有最高的表面六价铬和化学吸附氧的占比,因此呈现出最高的低温SCO活性。