The changes of nitric oxide production during the growth of Microcystis aerugrinosa

This study characterized the changes of nitric oxide (NO) production during the growth of Microcystis aerugrinosa, a cyanobacterium which usually cause cyanobacterial blooms. Results showed a drastic NO release accompanying with cell density and Chl-a content sharp rises when M. aerugrinosa grew from fifth day to sixth day. Moreover, high N:P ratio accelerated the cyanobacterial growth and NO burst. Sodium nitroprusside, an exogenous NO donor, promoted M. aerugrinosa growth with the optimal concentration of 0.1 mg/L. Experiments by supplementing with sodium nitrite and l-arginine demonstrated NO production in M. aerugrinosa cells was mainly through nitrate reductase (NR) pathway while minorly through NO synthase pathway. All these data suggested M. aerugrinosa produced increasing NO during its growth mainly by NR pathway, during which NO positively regulated the growth of M. aerugrinosa.     

Effects of high atmospheric CO2 concentration on root hydraulic conductivity of conifers depend on species identity and inorganic nitrogen source

We examined root hydraulic conductivity (L_p) responses of one-year-old seedlings of four conifers to the combined effects of elevated CO₂ and inorganic nitrogen (N) sources. We found marked interspecific differences in L_p responses to high CO₂ ranging from a 37% increase in P. abies to a 27% decrease in P. menziesii, but these effects depended on N source. The results indicate that CO₂ effects on root water transport may be coupled to leaf area responses under nitrate (NO₃⁻), but not ammonium (NH₄⁺) dominated soils. To our knowledge, this is the first study that highlights the role of inorganic N source and species identity as critical factors that determine plant hydraulic responses to rising atmospheric CO₂ levels. The results have important implications for understanding root biology in a changing climate and for models designed to predict feedbacks between rising atmospheric CO₂, N deposition, and ecohydrology.     

分点进水A/O工艺处理低碳源生活污水的脱氮性能研究

针对低C/N比污水脱氮的难点问题,在缺氧段不同点设置进水口,采用分点进水A/O工艺处理校园生活污水.考察了在污泥回流比为100%,硝化液回流比为200%,分流比为1∶1,缺氧池水力停留时间(HRT)分别为2、2.4和3 h情况下,分点进水A/O工艺的反硝化性能,并与传统的A/O工艺进行比较.结果表明,当缺氧池的水力停留...     

同步硝化反硝化工艺中DO浓度对N2O产生量的影响

采用序批式生物膜反应器(SBBR),在连续曝气全程好氧的运行条件下,考察不同溶解氧浓度对同步硝化反硝化脱氮性能及N2O产量的影响.控制溶解氧浓度恒定在1、2、2.5和3 mg/L.结果表明,DO为2 mg/L和2.5 mg/L时,氨氮去除率分别为97.9%和98.5%,同步硝化反硝化率均为99%.DO为2 mg/L时,...     

UASB反应器中厌氧氨氧化菌的影响因素研究

在UASB反应器中接种实验室已经驯化好的厌氧氨氧化颗粒污泥,对其进行厌氧氨氧化菌活性提高和影响因素的实验研究。研究表明厌氧氨氧化菌对NH4＋-N和N02--N的适宜浓度负荷均为200mg／L,适宜水力停留时间HRT、温度、pH和进水基质比（N02--N／NH4＋-N）分别为2h、30～35℃、7．5～8．5和0．95～1．2,NH4＋-N、NO2--N和TN的平均去除率分别为97．1％、98．3％和92．7％。     

N,N-二乙基对苯二胺分光光度法测定饮用水中的游离余氯

文中采用N,N-二乙基对苯二胺分光光度法测定饮用水中的游离余氯,实验结果表明,该方法可以准确测定水中的游离余氯且有好的线性,相关系数大于99%。方法检测限为0.01 mg/L,相对标准偏差为2.47～9.08%,回收率在92.5～105%之间,检测方法符合《生活饮用水卫生标准》(GB 5749-2006)的要求。     

Determining C/N ratios for typical organic wastes using biodegradable fractions

It is well established that an optimal aerobic and anaerobic microbial metabolism is achieved with a C/N ratio between 20 and 30. Most studies are currently based on chemically-measured carbon and nitrogen contents. However, some organic wastes can be composed of recalcitrant carbon fractions that are not bioavailable. To know the biodegradable C/N ratio, two different methods to determine the aerobic and anaerobic biodegradable organic carbon (BOC_AE and BOC_AN) are proposed and used to analyze a wide variety of different organic samples. In general, raw wastes and digested products have more amount of BOC_AE. On the contrast, the samples collected after an aerobic treatment have higher content of BOC_AN. In any case, all the BOC fractions are lower than the total organic carbon (TOC). Therefore, the C/N ratios based on BOC are always lower than the total C/N ratio based on the TOC measure. The knowledge of the real bioavailable C/N ratio is crucial for the biological treatments of organic materials. To reduce the test time necessary for BOC determination, the values of BOC for all the samples obtained at different times were compared and correlated with the final BOC. A method that allows for the determination of BOC_AE in 4 d is proposed. In relation to the anaerobic assay, the biogas potential calculated after 21 and 50 d was positively correlated with the final potential defined after 100 d of assay.     

氮磷钾和乙二胺四乙酸对镉污染三叶鬼针草的吸收特征研究

超富集植物的筛选是植物修复重金属污染土壤技术的核心内容.采用盆栽试验的方法,研究了Cd胁迫下添加营养元素N、P、K和螯合剂乙二胺四乙酸(EDTA)对三叶鬼针草(Bidens pilosa L.)的生长反应和生理生化特性以及对Cd的吸收积累特征.盆栽试验结果显示,在Cd为10 mg/kg时,添加营养元素N、P、K和EDT...     

A GIS-based technique for linking landscape characteristics to non-point source nitrogen export potential: implications for contributing areas management

A Nitrate-N Leaching Index (NLI) is calculated and the results indicate that nitrogen loss in the study area occurs through both leaching and surface runoff. A non-linear regression model of trapping efficiency was combined with a first order decay model to examine the impact of soil characteristics, slope, vegetative cover, land use and distance to streams on the spatial pattern of non-point source nitrogen inputs to streams. The model evaluates the statistical significance of each landscape factor and provides an easy interpretation of the landscape delivery ratio of nitrogen based on a pixel-based characterisation of the watershed. The model was validated by comparing the distributions of the observed and estimated monthly nitrogen concentrations. The exploratory GIS-based method presented here can improve the understanding of the impact of landscape characteristics on nitrate-nitrogen contributing areas and therefore assist watershed management efforts.