广西英罗港不同红树林群落土壤CO2和CH4通量对气温变化的响应

采用WEST-1011便携式土壤通量测量仪对广西北海英罗港自然保护区不同红树植物群落土壤的CO2和CH4排放通量特征以及其与气温的关系进行研究。结果表明,各群落土壤CH4通量的值都较小,在-2~3μmol.m-2.s-1之间;红海榄Rhizophora stylosa群落、木榄Brugiera gymmonhiza群落一天的CO2通量变化很小,秋茄Kandelia candel群落一天的CO2通量变化比较明显,最大值出现在19：00,为5.001μmol.m-2.s-1,桐花树Aegiceras corniculatum群落一天的CO2通量变化明显,最大值出现在11：00,为8.325μmol.m-2.s-1。排放通量与气温做相关性研究发现,气温与红海榄群落、木榄群落土壤CH4通量与气温呈不显著的正相关关系,与秋茄群落呈现极其显著的负相关关系,与桐花树群落呈显著的负相关关系;气温与红海榄群落、木榄群落、秋茄群落、桐花树群落的土壤CO2通量均呈不显著的负相关关系。     

Modeling Nutrient Export From Coastal California Watersheds

Nitrate and phosphate export coefficient models were developed for coastal watersheds along the Santa Barbara Channel in central California. One approach was based on measurements of nutrient fluxes in streams from specific land use classes and included a watershed response function that scaled export up or down depending on antecedent moisture conditions. The second approach for nutrient export coefficient modeling used anthropogenic nutrient loading for land use classes and atmospheric nutrient deposition to model export. In an application of the first approach to one watershed, the nitrate and phosphate models were within 20% of measured values for most storms. When applied to another year, both nitrate and phosphate models generally performed adequately with annual, storm‐flow, and base‐flow values within 20% of measured nutrient loadings. Less satisfactory results were found when applied to neighboring watersheds with difference percentages of land use and hydrologic conditions. Application of the second approach was less successful than the first approach.     

NUTRIENT MASS BALANCE FOR THE ALBEMARLE-PAMLICO DRAINAGE BASIN,NORTH CAROLINA AND VIRGINIA, 19901

ABSTRACT: A 1990 nitrogen and phosphorus mass balance calculated for eight National Stream Quality Accounting Network (NASQAN) basins in the Albemarle-Pamlico Drainage Basin indicated the importance of agricultural nonpoint sources of nitrogen and phosphorus and watershed nitrogen retention and processing capabilities. Basin total nitrogen and phosphorus input estimates were calculated for atmospheric deposition (which averaged 27 percent of total nitrogen inputs and 22 percent of total phosphorus inputs); crop fertilizer (27 and 25 percent); animal-waste (22 and 50 percent, respectively); point sources (3 percent each of total nitrogen and total phosphorus inputs); and biological nitrogen fixation (21 percent of total nitrogen inputs). Highest in-stream nitrogen and phosphorus loads were measured in predominantly agricultural drainage areas. Intermediate loads were observed in mixed agricultural/urban drainage areas; the lowest loads were measured in mixed agricultural/forested drainage areas. The difference between the sum of the nutrient input categories and the sum of the in-stream nutrient loads and crop-harvest nutrient removal was assigned to a residual category for the basin. The residual category averaged 51 percent of total nitrogen inputs and 54 percent of total phosphorus inputs.     

Thermal neutron fluence from ultra low-level γ-ray spectrometry of spoons activated during the JCO criticality accident at Tokai-mura in 1999

During the JCO-accident in Tokai-mura in 1999, the surrounding village was irradiated by an uncontrolled neutron flux. At some locations in that village, the thermal neutron flux was determined retrospectively by measurement of the very low activity of ⁵¹Cr and ⁶⁰Co in stainless-steel spoons using γ-ray spectrometry in underground laboratories. Activities determined in the HADES underground facility are presented here, together with calibrations performed using a well-defined thermal neutron flux to directly estimate the fluence of thermal neutrons independent of most assumptions. The results show measurable ⁵¹Cr in three samples and ⁶⁰Co in four samples taken from locations at distances of up to 430 m from the accident location despite the elapse of 4 half-lives of ⁵¹Cr before measurement. Effects of air transport of the samples were considered and shown to be negligible.     

模拟SO_4~(2-)沉降对河口潮汐湿地甲烷排放通量的影响

2008年每月小潮日原位定期向闽江河口鳝鱼滩咸草(Cyperus malaccensis)潮汐湿地试验样地施加25,50,100kgSO42--S/(hm2·a)的硫酸钠溶液,探讨模拟SO42-酸沉降对河口潮汐湿地甲烷排放通量的影响.结果表明,SO42-酸沉降对于河口潮汐湿地甲烷排放通量基本无抑制作用.添加SO42-室内厌氧培养试验结果显示,虽然SO42-输入对湿地土壤CH4产生量具有一定的抑制作用,但相对对照组,下降幅度仅为8.5%~15.4%.室内添加甲烷产生基质的厌氧培养试验结果表明,非竞争性途径甲烷产生基质(甲醇和三甲胺)的添加可刺激并增加土壤的甲烷产生量,解释了原位施加SO42-对于河口潮汐湿地甲烷排放通量的基本无抑制作用的试验结果.     

Nitrous oxide fluxes from upland soils in central Hokkaido, Japan

Nitrous oxide (N2O) fluxes from soils were measured using the closed chamber method during the snow-free seasons (middle April to early November),for three years,in a total of 11 upland crop fields in central Hokkaido,Japan.The annual mean N2O fluxes ranged from 2.95 to 164.17 μgN/(m2·h),with the lowest observed in a grassland and the highest in an onion field.The instantaneous N2O fluxes showed a large temporal variation with peak emissions generally occurring following fertilization and heavy rainfall eve...     

浸入式超滤膜工艺稳定运行影响因素研究

以确定浸入式超滤膜工艺稳定运行工况为目标,进行了混凝.浸入式超滤膜工艺处理滦河原水的中试研究.采用横跨膜压差(TMP)做为表征膜稳定运行的工艺参数,考察了膜通量、制水周期、原水水质条件的改变对膜工艺的影响.结果表明,采用浸入式膜处理滦河水时,膜通量为53.3 L/(m2·h)且制水周期为30 min时膜工艺运行稳定,能较好控制膜污染;水温变化对膜工艺运行影响较大,低温期单个过滤周期TMP比高藻期增加了76%;EFM和化学清洗结合是一种有效地控制膜污染、强化稳定运行的措施.     

Model evaluation of different mechanisms driving freeze–thaw N2O emissions

N₂O emissions from soil contribute significantly to global warming. Pulse emissions of N₂O from soils during freeze-thawing were recently recognized as important atmospheric sources. In this modelling study we explore three different hypotheses for explaining freeze–thaw related N₂O emissions: (1) soil frost or snow cover may reduce gas diffusion and create anaerobic conditions that stimulate N₂O production via denitrification, (2) microbes that die of frost deliver easy decomposable organic carbon and nitrogen to the soil, which stimulates microbial growth and vigorous N₂O production during freeze–thaw, and (3) the enzyme nitrous oxide reductase, which is responsible for the reduction of N₂O to N₂ during denitrification, is more sensitive to low temperatures than other enzymes, so that N₂O becomes the dominating end-product of denitrification at low temperatures. These hypotheses were tested with a biogeochemical model that combines hydrology and physics calculations with a newly developed, parameter-poor biochemistry module. The model was first calibrated with field datasets on soil–atmosphere fluxes of N₂O, NO and CO₂ and soil NO₃ and NH₄ concentrations that were measured in a spruce forest in Southeast Germany in the years 1994–1997. Subsequently, additional model mechanisms were implemented that allow the model to describe the outlined mechanisms potentially driving freeze–thaw N₂O fluxes. After each implementation the model was recalibrated. We were able to mimic dimension and timing of high N₂O emissions when either one of the first two hypotheses were assumed, but found no confirmation for the third. The best model fit was achieved by combining hypothesis one and two, indicating that freeze–thaw N₂O emissions are not mono-causal.     

Fouling of nanofiltration membrane by e uent organic matter: Characterization using di erent organic fractions in wastewater

The UF membrane with molecular weight cuto (MWCO) ranging from 2 to 100 kDa and XAD-8 resin were employed to identify the characteristic of molecular weight (MW) distribution of wastewater e uent organic matter (EfOM) in terms of TOC and UV254, as well as the amounts of the hydrophilic/hydrophobic organic fractions in di erent MW ranges. Then, the nanofiltration (NF) membrane fouling experiments were carried out using the above fractionated water to investigate the e ect of MW distribution and hydrophilic/hydrophobic characteristics of EfOM on the membrane flux decline using the fractionated water samples. The experimental results have shown that 45.61% of the total organics belongs to the low MW one, among which the percentage of the hydrophilic organics with low MW (less than 2 kDa) was up to 28.07%, while that of the hydrophobic organics was 17.54%. In particular, the hydrophilic fraction was found to be the most abundant fraction in the e uents. MW distribution has a significant e ect on the membrane fouling. When the MWwas less than 30 kDa, the lower the MW, the larger was the specific flux decline, while in the case of MW higher than 30 kDa, the higher the MW, the larger was the specific flux decline, and the decline degree of low MW organics was larger than the high MW one. With the same MW distribution range, specific flux decline of the hydrophilic organic was considerably slower than that of the hydrophobic organic, which indicated that the hydrophobic organic fractions dominantly contribute to the flux decline.     

基于能值分析的城市物质代谢研究

采用能值分析方法,构建了基于城市物质代谢通量指标、代谢存量指标和代谢效率指标的城市物质代谢指标体系,并以北京、天津、上海和重庆四个直辖市为例计算了2005年四城市物质代谢状况。分析结果表明:北京市代谢效率最低;上海市代谢通量和代谢存量最大,但是代谢效率不容乐观;重庆市代谢通量和代谢存量在四个城市中居于末位,但是代谢效率最高;天津市在四个城市中代谢呈中等水平。最后根据分析结果对城市今后的可持续发展提出了意见和建议。