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31.
A series of mesocosms was exposed to a suite of light treatments and nutrient enrichment in order to generate algal communities of varying biomass. the influence of this biomass on the speciation of copper (II) was studied. Distribution coefficients (Kd,Lkg-1) were relatively high (logKd = 5 to 7), indicative of robust trace metal sequestration, and were likely controlled by the particulate organic carbon content (foc). Differences in Kd over time and among treatments were significant, as was the relationship between Kd and foc. Fluorescence quenching was used to determine binding capacities (Lt, M) and their associated binding constants (Kcond,M-1) in order to model the solid phase copper speciation. the Kcond ranged between 2.1 and 5.2 × 1012M-1, indicating a very strong copper-ligand complex, and was higher in mesocosms that received more light. the light Lt increased over time, dramatically after the nutrient enrichment, but did not vary systematically among light treatments. Lt ranged from 7.2 × 10- 7 to 4.9 × 10- 5 M. the large magnitudes of Kd, Kcond and Lt ensured that greater than 97% of total copper in the mesocosms was complexed by organic matter. the total copper concentration ([Cu]T, M) needed to reach a target dissolved copper concentration of 10-12.5 M (pCu = 12.5) was determined for each mesocosm over time. [Cu]T was between 8.02 × 10-5 and 3.41 × 10-2 M, and increased over time. the [Cu]T normalized to the target pCu (Effective Dose Ratio, EDR) increased directly with increases in algal biomass, indicating a direct link between system productivity and copper exposure. Approximately 45% of the variance in EDR was explained by variance in total biomass, while the residual variance in EDR was due likely to differences in the strengths of particle associations and magnitude of binding capacities. 相似文献
32.
Mirela G. Tulbure Michael C. WimberlyArvid Boe Vance N. Owens 《Agriculture, ecosystems & environment》2012,146(1):121-129
The U.S. Renewable Fuel Standard calls for 136 billion liters of renewable fuels production by 2022. Switchgrass (Panicum virgatum L.) has emerged as a leading candidate to be developed as a bioenergy feedstock. To reach biofuel production goals in a sustainable manner, more information is needed to characterize potential production rates of switchgrass. We used switchgrass yield data and general additive models (GAMs) to model lowland and upland switchgrass yield as nonlinear functions of climate and environmental variables. We used the GAMs and a 39-year climate dataset to assess the spatio-temporal variability in switchgrass yield due to climate variables alone. Variables associated with fertilizer application, genetics, precipitation, and management practices were the most important for explaining variability in switchgrass yield. The relationship of switchgrass yield with climate variables was different for upland than lowland cultivars. The spatio-temporal analysis showed that considerable variability in switchgrass yields can occur due to climate variables alone. The highest switchgrass yields with the lowest variability occurred primarily in the Corn Belt region, suggesting that prime cropland regions are the best suited for a constant and high switchgrass biomass yield. Given that much lignocellulosic feedstock production will likely occur in regions with less suitable climates for agriculture, interannual variability in yields should be expected and incorporated into operational planning. 相似文献
33.
Zhiqiang Chen Lizhi Zhao Ye Ji Qinxue Wen Long Huang 《Frontiers of Environmental Science & Engineering》2019,13(4):54
34.
Mei Lei Ziping Dong Ying Jiang Philip Longhurst Xiaoming Wan Guangdong Zhou 《Frontiers of Environmental Science & Engineering》2019,13(2):24
35.
The macro-algae communities observed in the south lake of Tunis are characterized by the predominance of nitrophilous algae
which are in the order of biomass importance:Ulva, Cladophora andEnteromorpha. We have noted seasonal changes of alga distribution. The wind appears to be one of the most important factors influencing
this distribution. The total biomass reaches a maximum in the spring. Rapid decomposition of the biomass leads to a severe
ecological imbalance, resulting in crises of anoxia and fish death.
A restoration project has already started. It aims at removal of contaminated muds and the introduction of a new circulation
system.
The main objectives of this work were to collect information on the distribution and biomass of the phytobenthic communities
as a first step in the constitution of a database for further comparison. 相似文献
36.
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38.
长期侧流提取对EBPR系统除磷及其磷回收性能的影响 总被引:1,自引:1,他引:0
实验采用交替厌氧/好氧(An/O)运行模式的SBR反应器,考察310 d内分3个批次提取侧流比为0、1/4、1/3、1/2的厌氧放磷上清液后EBPR系统的脱氮除磷效果及相应的磷回收性能.结果表明,整个实验阶段系统对COD和氨氮的去除较为稳定,出水均能满足《城镇污水处理厂污染物综合排放标准》一级A标准,总氮去除因厌氧阶段反硝化不断增强有所提升,达标率由88.2%显著上升至98.6%.然而,随着厌氧上清液提取次数的增多,系统释磷能力整体下降,但前两个批次中系统除磷均稳定高效,去除率在90%以上,相应地出水磷达标率大于75%,仅第3批次实验中侧流比为1/2时系统除磷率出现大幅波动,最低降为54.2%,并贡献该批次出水磷不达标率的60%,说明长期提取1/2侧流比不利于主流工艺出水稳定维持.研究还发现,长期进行侧流磷回收实验有利于污泥减量,且对污泥沉降性能影响不大.因此,在EBPR系统内长期提取适当侧流比的厌氧上清液以进行磷回收与主流工艺同步高效脱氮除磷具有可行性. 相似文献
39.
Peng Xu Junke Zhang Dongsheng Ji Zirui Liu Guiqian Tang Changsheng Jiang Yuesi Wang 《环境科学学报(英文版)》2018,30(1):16-27
In this study, we performed a highly time-resolved chemical characterization of nonrefractory submicron particles(NR-PM_1) in Beijing by using an Aerodyne high-resolution time-of-flight aerosol mass spectrometer(HR-ToF-AMS). The results showed the average NR-PM_1 mass concentration to be 56.4 ± 58.0 μg/m~3, with a peak at 307.4 μg/m~3. Due to the high frequency of biomass burning in autumn, submicron particles significantly increased in organic content, which accounted for 51% of NR-PM_1 on average. Secondary inorganic aerosols(sulfate + nitrate + ammonium) accounted for 46% of NR-PM_1, of which sulfate,nitrate, and ammonium contributed 15%, 20%, and 11%, respectively. To determine the intrinsic relationships between the organic and inorganic species, we used the positive matrix factorization(PMF) model to merge the high-resolution mass spectra of the organic species and NO+and NO_2~+ions. The PMF analysis separated the mixed organic and nitrate(NO+and NO_2~+) spectra into four organic factors, including hydrocarbon-like organic aerosol(HOA), oxygenated organic aerosol(OOA), cooking organic aerosol(COA), and biomass burning organic aerosol(BBOA), as well as one nitrate inorganic aerosol(NIA) factor. COA(33%) and OOA(30%) contributed the most to the total organic aerosol(OA) mass, followed by BBOA(20%) and HOA(17%). We successfully quantified the mass concentrations of the organic and inorganic nitrates by the NO+and NO2+ions signal in the organic and NIA factors. The organic nitrate mass varied from 0.01-6.8 μg/m~3, with an average of 1.0 ±1.1 μg/m~3, and organic nitrate components accounted for 10% of the total nitrate mass in this observation. 相似文献
40.
为了探讨生物质锅炉羰基化合物的排放特征,采用气袋采样-PFPH衍生-GC/MS分析的方法测量了6台生物质锅炉排放烟气中的21种羰基化合物.结果表明,这些生物质锅炉的烟气中羰基化合物排放特征存在明显差异,总体而言,己醛和丙醛浓度在测定的21种目标化合物中比重最高,分别占总量的29%~47%和19%~31%,其次为甲醛和丙酮,乙醛和壬醛.通过羰基化合物排放量与消耗的燃料质量比值估算了排放因子,6台锅炉羰基化合物排放因子介于3.06~18.29mg/kg之间,平均为9.45±6.05mg/kg.采用最大增量反应活性法(MIR)评价了羰基化合物的化学反应活性及臭氧生成潜势(OFP),平均总的臭氧生成潜势(以O3计)为5.97gO3/gVOCs;己醛、丙醛、甲醛对OFP的贡献尤为明显,丙酮虽然占有较高的质量浓度,但对OFP的贡献较低. 相似文献