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371.
Gabriel Maltais-Landry Roxane Maranger Jacques Brisson Florent Chazarenc 《Environmental pollution (Barking, Essex : 1987)》2009,157(3):748-754
Greenhouse gas (GHG) emissions by constructed wetlands (CWs) could mitigate the environmental benefits of nutrient removal in these man-made ecosystems. We studied the effect of 3 different macrophyte species and artificial aeration on the rates of nitrous oxide (N2O), carbon dioxide (CO2) and methane (CH4) production in CW mesocosms over three seasons. CW emitted 2-10 times more GHG than natural wetlands. Overall, CH4 was the most important GHG emitted in unplanted treatments. Oxygen availability through artificial aeration reduced CH4 fluxes. Plant presence also decreased CH4 fluxes but favoured CO2 production. Nitrous oxide had a minor contribution to global warming potential (GWP < 15%). The introduction of oxygen through artificial aeration combined with plant presence, particularly Typha angustifolia, had the overall best performance among the treatments tested in this study, including lowest GWP, greatest nutrient removal, and best hydraulic properties. 相似文献
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373.
Karin Wiench Wendel Wohlleben Volker Hisgen Kristin Radke Edward Salinas Sabine Zok Robert Landsiedel 《Chemosphere》2009,76(10):1356-1365
Among the emerging literature addressing the biological effects of nanoparticles, very little information exists, particularly on aquatic organisms, that evaluates nanoparticles in comparison to non-nanocounterparts. Therefore, the potential effects of nano-scale and non-nano-scale TiO2 and ZnO on the water flea, Daphnia magna, were examined in 48-h acute toxicity tests using three different test media, several pigment formulations – including coated nanoparticles – and a variety of preparation steps. In addition, a 21-d chronic Daphnia reproduction study was performed using coated TiO2 nanoparticles. Analytical ultracentrifugation analyses provided evidence that the nanoparticles were present in a wide range of differently sized aggregates in the tested dispersions. While no pronounced effects on D. magna were observed for nano-scale and non-nano-scale TiO2 pigments in 19 of 25 acute (48-h) toxicity tests (EC50 > 100 mg L−1), six acute tests with both nano- and non-nano-scale TiO2 pigments showed slight effects (EC10, 0.5–91.2 mg L−1). For the nano-scale and non-nano-scale ZnO pigments, the acute 48-h EC50 values were close to the 1 mg L−1 level, which is within the reported range of zinc toxicity to Daphnia. In general, the toxicity in the acute tests was independent of particle size (non-nano-scale or nano-scale), coating of particles, aggregation of particles, the type of medium or the applied pre-treatment of the test dispersions. The chronic Daphnia test with coated TiO2 nanoparticles demonstrated that reproduction was a more sensitive endpoint than adult mortality. After 21 d, the NOEC for adult mortality was 30 mg L−1 and the NOEC for offspring production was 3 mg L−1. The 21-d EC10 and EC50 values for reproductive effects were 5 and 26.6 mg L−1, respectively. This study demonstrates the utility of evaluating nanoparticle effects relative to non-nano-scale counterparts and presents the first report of chronic exposure to TiO2 nanoparticles in D. magna. 相似文献
374.
An experiment was conducted to assess the role of different concentrations of dicyandiamide (DCD), a potent nitrification
inhibitor, on temporal changes in nitrous oxide emission from sandy loam agricultural soil. It was found that with increasing
concentration of DCD i.e. from 6 to 12% of nitrogen applied in the form of urea, there was a decrease in the both average
and peak N2O emissions. However, from 14% DCD treated soil, there was a non-significant alteration in the N2O emission. Maximum average N2O efflux of 217.55 μg m−2 h−1 was noted from control plots. As compared to control, there was an attenuation of 50, 58, 65, and 91% average N2O efflux from 6, 8, 10 and 12% DCD applied pots, respectively, whereas, there was a negative average of N2O efflux from the soil with 14% DCD treatment. The soil N content also showed a significant correlation with N2O emission. Therefore, 12% DCD treatment has been found to be the best with regard to attenuation of nitrous oxide from sandy
loam agricultural soils. 相似文献
375.
A trimetal oxide was developed as a fluoride adsorbent by coprecipitation of Fe(II), Al(III) and Ce(IV) salt solutions with a molar ratio of 1:4:1 under alkaline condition. The material retained amorphous structure and maintained relatively stable fluoride adsorption performance at calcination temperatures lower than 600 degrees C. The optimum pH range for fluoride adsorption was 6.0-6.5 and the adsorbent also showed high defluoridation ability around pH 5.5-7.0, which is preferable for actual application. A high fluoride adsorption capacity of 178 mg g(-1) was acquired under an equilibrium fluoride concentration of 84.5 mg l(-1), adsorbent dose of 150 mg l(-1) and pH 7.0. The adsorption isotherm could be better described by the two-site Langmuir model than the one-site model, suggesting the existence of two types of active sites on the adsorbent surface. Coexistence of high concentrations of phosphate or arsenate only led to partial inhibition of fluoride adsorption, which further suggests the existence of heterogeneous adsorption sites. Sulfate and chloride did not affect fluoride adsorption, and nitrate influenced it only when the concentration of NO(3)(-)-N exceeded 50 mg l(-1). A high desorption efficiency of 97% was achieved by treating fluoride loaded Fe-Al-Ce oxide with NaOH solution at pH 12.2. A column experiment using the adsorbent fabricated into 1mm pellets was performed at an initial fluoride concentration of 5.5 mg l(-1), space velocity of 5h(-1) and pH of 5.8, and 2240 bed volumes were treated with the effluent fluoride under 1.0 mg l(-1). 相似文献
376.
将废锂电池正极用酸溶解,再分别采用分步沉淀法和吸附沉淀法去除废锂电池液中的Fe^3+,Al^3+,Ca^2+,Mg^2+,抽滤后得到含CoSO。的滤液;用NaHCO3作沉淀剂,对CoSO4滤液进行沉淀反应,将得到的沉淀物过滤、洗涤、干燥后得CoCO4粉末;将CoCO4粉末进行煅烧后得Co3O4粉末。实验得出的制备CoCO4粉末的最佳工艺条件:反应温度50℃,用NaHCO,作沉淀剂;制备Co3O4粉末的最佳工艺条件:煅烧温度600℃,煅烧时间大于4h。在该条件下得到的Co3O4粉末符合锂电池生产的要求。 相似文献
377.
378.
水体沉积物中有效砷的测试新方法研究 总被引:2,自引:1,他引:1
一种氧化铁/醋酸纤维素复合膜(FeO/CAM)被用于太湖沉积物中砷的生物有效性评估.结果发现,在水介质中,FeO/CAM对沉积物中砷的富集量随土水比增加而呈乘幂函数减少,在土水质量比为0.025(即1:40)之后趋于某一平台值;在土水比为0.025并得到充分振荡的条件下,沉积物中释放的有效砷被FeO/CAM富集至膜中,并随时间增加而增加,至24 h后逐渐趋于平衡,这一过程恰当地模拟了生物对砷的吸收.因此,FeO/CAM可以用于有效砷的体外测试.利用FeO/CAM对12个总砷含量为6.4~34.6 mg·kg-1的太湖沉积物样品中的有效砷进行了测定.结果发现,FeO/CAM提取的有效砷含量与磷酸盐缓冲液提取的有效砷含量之间显著相关.太湖沉积物中的有效砷含量与总砷、总磷、有机质和吸附磷含量以及磷吸附饱和度显著相关,说明沉积物理化属性对有效砷含量有重要影响.FeO/CAM克服了化学试剂提取过程中引起的非有效态砷释放的根本缺陷,因此,FeO/CAM方法在沉积物有效砷含量的测定时比化学试剂提取法可能更准确. 相似文献
379.
380.
Juan WU Jian ZHANG Wenlin JIA Huijun XIE Bo ZHANG 《Frontiers of Environmental Science & Engineering in China》2009,3(2):241-247
The effects of chemical oxygen demand (COD) concentration in the influent on nitrous oxide (N2O) emissions, together with the relationships between N2O and water quality parameters in free water surface constructed wetlands, were investigated with laboratoryscale systems.
N2O emission and purification performance of wastewater were very strongly dependent on COD concentration in the influent, and
the total N2O emission in the system with middle COD influent concentration was the least. The relationships between N2O and the chemical and physical water quality variables were studied by using principal component scores in multiple linear
regression analysis to predict N2O flux. The multiple linear regression model against principal components indicated that different water parameters affected
N2O flux with different COD concentrations in the influent, but nitrate nitrogen affected N2O flux in all systems. 相似文献