DETERMINING CRITICAL WATER QUALITY CONDITIONS FOR INORGANIC NITROGEN IN DRY,SEMI‐URBANIZED WATERSHEDS1

ABSTRACT: Traditional approaches to establishing critical water quality conditions, based on statistical analysis of low flow conditions and expressed as a recurrence interval for low flow conditions (e.g., 7Q10), may be inappropriate for drier watersheds. The use of 7Q10 as a standard design flow assumes year‐round flow, but in these watersheds, 7Q10 is zero or very small. In addition, the increasing use of multiple year dynamic water quality models at daily time steps can supercede the use of steady state approaches. Many of these watersheds are also under increasing urbanization pressure, which accentuates the flashiness of runoff and the episodic nature of critical water quality conditions. To illustrate, the conditions in the Santa Clara River, California, are considered. A statistical analysis indicates that higher inorganic nitrogen concentrations correlate strongly with low flow. However, peaks in concentrations can occur during the first storms, particularly where nonpoint source contribution is significant. Critical conditions can thus occur at different flow regimes depending on the relative magnitude of flow and pollutant contributions from various sources. The use of steady state models for these dry semi‐urbanized watersheds based on 7Q10 flows is thus unlikely to accurately simulate the potential for exceeding water quality objectives. Dynamic simulation of water quality is necessary, and as the recent intense storm event sampling data indicate, the models should be formulated to consider even smaller time steps. This places increasing demand on computational resources and datasets to accurately calibrate the models at this temporal resolution.     

华北地区主要农业灾害及灾情分析

本文分析了华北地区农业灾害发生的气象背景,并利用1981～1990年的农业统计资料分析了华北地区的农业灾情状况及因灾而造成的粮、棉损失量。华北地区单位耕地面积的受灾率及成灾率分别为47.3%和23.0%,大致相当于二年一遇灾和四年一成灾。华北地区因农业灾害而造成的粮、棉损失量平均每年为397.0和34.5万吨,粮、棉损失率分别为4.9%及15.3%。     

序批式曝气生物滤池处理含海水污水中的硝化性能

采用序批式曝气生物滤池工艺,以牡蛎壳为填料、含海水污水为处理对象,系统考察不同的海水含率、原水葡萄糖和氨氮浓度等原水条件下的硝化性能。结果表明,对于海水含率在40%到100%的污水处理,氨氮去除率可达到95%以上,表明该生物滤池中的氨氧化菌(AOB)可耐受较高的海水盐度;耐海水盐度的驯化硝化细菌中,AOB的耐盐度抑制能力强于亚硝酸氧化菌(NOB),当海水含率大于70%时,NOB的活性更容易受到抑制。在高海水盐度下,降低原水的葡萄糖与氨氮浓度可提高NOB活性。牡蛎壳附着生物膜与液相悬浮污泥中的AOB 和NOB均参与了氨氮去除,生物膜中的AOB和NOB活性高于悬浮污泥。     

改性半焦脱除烟气中SO2的研究

对内蒙工业副产褐煤半焦（比表面积49.187m^2／g,孔容0.0351cm^2／g）,采用加压水热化学活化法,HNO3活化法和高温煅烧相结合的方法制备出半焦烟气脱硫剂,并对脱硫剂的脱硫性能进行固定床活性评价。分析表明,其脱硫效果比较好,转化率维持在50％以上的累计硫容可达24．30％,脱硫时间长达35h,远远高于原料半焦的脱硫效果（硫容为0．68％,时间为1．5h）;同时采用水洗法对脱硫剂进行再生,其再生液可用来制备浓度为9.01％的稀硫酸。     

Air pollution and hospital visits for acute upper and lower respiratory infections among children in Ningbo,China: A time-series analysis

Acute upper and lower respiratory infections are main causes of mortality and morbidity in children. Air pollution has been recognized as an important contributor to development and exacerbation of respiratory infections. However, few studies are available in China. In this study, we investigated the short-term effect of air pollution on hospital visits for acute upper and lower respiratory infections among children under 15 years in Ningbo, China. Poisson generalized models were used to estimate the associations between air pollution and hospital visits for acute upper and lower respiratory infections adjusted for temporal, seasonal, and meteorological effects. We found that four pollutants (PM_2.5, PM₁₀, NO₂, and SO₂) were significantly associated with hospital visits for acute upper and lower respiratory infections. The effect estimates for acute upper respiratory infections tended to be higher (PM_2.5 ER = 3.46, 95% CI 2.18, 4.76; PM₁₀ ER = 2.81, 95% CI 1.93, 3.69; NO₂ ER = 11.27, 95% CI 8.70, 13.89; SO₂ ER = 15.17, 95% CI 11.29, 19.19). Significant associations for gaseous pollutants (NO₂ and SO₂) were observed after adjustment for particular matter. Stronger associations were observed among older children and in the cold period. Our study suggested that short-term exposure to outdoor air pollution was associated with hospital visits for acute upper and lower respiratory infections in Ningbo.     

水平潜流人工湿地脱氮功效中植物的作用

为了研究芦苇(Phragmites australis)在收割期前/后、湿地床体内部各个区域内、一年四季中在水平潜流人工湿地脱氮效用所起的作用,实验设置了有/无植物2组平行反应器。结果表明,芦苇在收割前/后对于水平潜流人工湿地脱氮效果均有促进作用,植物地上部分氮吸收量占湿地脱氮量的10.2%。在芦苇收割前/后(5月~9月、10月~次年5月),芦苇湿地日均脱氮量分别是无植物湿地的1.55倍与1.11倍。高、矮芦苇不同组织中总氮浓度分布趋势一致,2种芦苇各组织含量分别为:穗(28.69 g/kg)>叶(13.69 g/kg)>茎(5.31 g/kg)、穗(28.06 g/kg)>叶(14.61 g/kg)>茎(8.46 g/kg)。在湿地的各个沿程区域,总氮、氨氮累加去除率变化趋势一致,并且从反应器前部到尾部呈上升趋势,从上部到下部呈下降趋势。有芦苇湿地的脱氮效用优于无植物湿地,且底部氮积累含量也较少。一年四季中有芦苇湿地在各个季节脱氮量是无植物湿地的1.06~1.47倍。     

Decomplexation of Cr(III)-EDTA and simultaneous abatement of total Cr by photo-oxidation: efficiency and in situ reduction of intermediate Cr(VI)

Environmental Science and Pollution Research - Most prevailing processes are incapable of removing Cr(III)-organic complexes efficiently and facing the problem of in-process formation of highly...     

A TiO2/crosslinked carboxymethyl starch composite for high-efficiency adsorption and photodegradation of cationic golden yellow X-GL dye

In this paper, a crosslinked carboxymethyl starch (CCMS) was prepared with corn starch as the raw material, epichlorohydrin as the crosslinking agent, and chloroacetic acid as the etherifying agent through a series of crosslinking, alkalization, and etherification reactions, respectively. Nano-TiO₂ was loaded onto the surface of the CCMS by the sol-gel method to obtain a TiO₂/CCMS composite. The TiO₂/CCMS composite was characterized by XPS, XRD, SEM, and BET. XPS showed that the surface chemical composition of the TiO₂/CCMS composite material contained titanium; XRD diffraction patterns indicated that the crystal form of the TiO₂/CCMS composite was a combination of the CCMS and anatase TiO₂. The surface morphology obtained by SEM showed that there were nano-TiO₂ particles on the surface of the CCMS. The specific surface area of the TiO₂/CCMS composite was larger than that of CCMS. The adsorption-photodegradation performance of the TiO₂/CCMS composite was also studied under UV irradiation, and the results showed that significant adsorption-photodegradation synergies occurred.

     

朱集矿13-1煤瓦斯参数规律研究

为了采取合理的瓦斯抽采技术,实现矿井安全高效开采,对朱集矿13-1煤瓦斯基本参数进行了现场和实验室测定,得出了瓦斯含量、瓦斯压力、放散初速度,透气性系数、坚固性系数等参数,并对测定结果进行了理论分析,得出了这些参数的基本规律.结果表明:随着开采深度的增加,在一定深度范围内,其瓦斯压力、瓦斯含量呈线性增长,瓦斯压力与瓦斯含量都比较大;煤层钻孔瓦斯衰减系数较大,该煤层的透气性系数较小,D、K值小于其临界值,可判断出该煤层为难抽煤层且有突出危险性.     

地铁突发大客流安全控制方式设计

地铁突发大客流不仅影响单个车站,对整个地铁网也会产生影响.为了保证地铁的正常运营活动,从系统整体联合的角度出发,提出事先预测、系统联合、加强沟通、分级负责的应对突发大客流事件原则;重点设计了大客流情况下的行车组织和车站客流控制方式,提出了自组织与他组织的大客流安全控制措施,并从客流角度对大客流按阶段进行划分控制,以科学、灵活、安全的方式控制大客流.