Spectroscopic Distribution of Dissolved Organic Matter in a Dam Reservoir Impacted by Turbid Storm Runoff

Spectroscopic characteristics of dissolved organic matter (DOM) in a large dam reservoir were determined using ultraviolet absorbance and fluorescence spectroscopy to investigate spatial distribution of DOM composition after turbid storm runoff. Water samples were collected along a longitudinal axis of the reservoir at three to four depths after a severe storm runoff. Vertical profiles of turbidity data showed that a turbid water layer was located at a middle depth of the entire reservoir. The spectroscopic characteristics of DOM samples in the turbid water layer were similar to those of terrestrial DOM, as demonstrated by the higher specific UV absorbance (SUVA) and the lower fluorescence emission intensity ratio (F ₄₅₀/F ₅₀₀) compared to other surrounding DOM samples in the reservoir. Synchronous fluorescence spectroscopy revealed that higher content of humic-like DOM composition was contained in the turbid water. Fluorescence excitation–emission matrix (EEM) showed that lower content of protein-like aromatic amino acids was present in the turbid water DOM. The highest protein-like fluorescence was typically observed at a bottom layer of each sampling location. The bottom water DOM exhibited extremely high protein-like florescence near the dam site. The particular observation was attributed to the low water temperature and the isolation of the local bottom water due to the upper location of the withdrawal outlet near the dam. Our results suggest that the distribution of DOM composition in a dam reservoir is strongly influenced by the outflow operation, such as selective withdrawal, as well as terrestrial-origin DOM inputs from storm runoff.     

Volatile Organic Compounds: Sampling Methods and Their Worldwide Profile in Ambient Air

The atmosphere is a particularly difficult analytical system because of the very low levels of substances to be analysed, sharp variations in pollutant levels with time and location, differences in wind, temperature and humidity. This makes the selection of an efficient sampling technique for air analysis a key step to reliable results. Generally, methods for volatile organic compounds sampling include collection of the whole air or preconcentration of samples on adsorbents. All the methods vary from each other according to the sampling technique, type of sorbent, method of extraction and identification technique. In this review paper we discuss various important aspects for sampling of volatile organic compounds by the widely used and advanced sampling methods. Characteristics of various adsorbents used for VOCs sampling are also described. Furthermore, this paper makes an effort to comprehensively review the concentration levels of volatile organic compounds along with the methodology used for analysis, in major cities of the world.     

氨氧化木质素作为硝化抑制剂的研究

通过室内培养实验对氨氧化木质素(AOL)的硝化抑制作用进行了探讨。在相同条件下,分别加AOL和DCD处理的铵态氮质量分数都要比未加硝化抑制剂处理的高;相应地,在开始阶段硝态氮质量分数也要比未加硝化抑制剂处理的低。研究结果表明,AOL作为硝化抑制剂是有效果的。     

影响土壤中微生物体氮的因子

综述了影响土壤微生物体氮的因子,以及微生物体氮与可矿化氮之间的关系。着重讨论了土壤有机质、有机物料、氮肥、作物根系、土壤温度和湿度对微生物体氮的影响及研究进展;评价了土壤微生物体氮与可矿化氮的关系的研究结果。     

化肥氮素在水稻田中迁移与淋失的模拟研究

为了研究氮化肥施入农田对地表水和地下水的影响 ,在一种特殊的大型人工模拟土层和地下水装置中进行试验。研究结果表明 :即使尿素和生物矿质复混肥以中、低施肥量施入水田 ,也会造成地表淹水、耕层土壤和不同深度土层溶液有较高含量的有机 N和 N H3- N,并对地下水补给状况极差的地下水有明显的污染 ;水田中 N O- 3 - N很难长期存在 ,其污染程度可忽略不计     

有机肥对土壤NO3--N累积的影响

长期定位试验和调查取样的结果表明,土壤中NO3--N的累积量随有机肥施用量的增加而增加,过量施用有机肥会引起2 m以下深层次土壤中NO3--N的大量累积。当有机肥和无机肥配合施用时,土壤中NO3--N的累积量随总施N量的增加而增加。有机肥对土壤NO3--N累积的影响和对地下水的潜在威胁不容忽视。     

环境监测用氮气中多组分VOCs标准物质的研制

介绍了采用称量法制备瓶装1μmol/mol氮气中42个组分挥发性有机物(VOCs)标准物质的研制方法。建立了选择离子模式,气相色谱-质谱联用的分析方法,对目标组分在气瓶中的长期稳定性进行了考察。所选择的42种目标组分完全满足中国环境保护标准《环境空气挥发性有机物的测定吸附管采样-热脱附/气相色谱-质谱法》(HJ 644—2013)和美国环保署《使用特殊处理的采样罐/气相色谱仪检测环境大气中的挥发性有机物》(EPA TO—14A)这2个方法标准中所规定的环境空气中挥发性有机有害成分的监测要求。将研制的气体标准物质与中国计量科学研究院(NIM)和英国国家物理实验室(NPL)分别进行了比对测试,取得了良好的比对结果与国际等效度。结果表明,1μmol/mol氮气中42种组分VOCs标准物质的有效期为一年,相对扩展不确定度为5.0%(包含因子k=2),并取得国家标准物质证书GBW(E)062231。     

水杨酸法检测水质氨氮的改进方法

该氨氮检测方法是对水杨酸分光光度法的改进,通过将50 g/L的水杨酸改为150 g/L的水杨酸钠,将有效氯为3. 5 g/L的次氯酸钠溶液改为5 g/L的二氯异氰尿酸钠溶液,增加了检测试剂的稳定性和贮存时间,同时将氨氮测定上限从1 mg/L提高至2. 5 mg/L,并将显色时间从60 min优化为30 min,使得此方法更为便捷。该方法的氨氮标准曲线线性关系良好,相关系数为0. 999 6,准确性和精密度高,加标回收率良好,适用于不同类型水质中氨氮的检测。     

氨气敏电极法和纳氏试剂分光光度法对地表水中氨氮的比对测试

采用不同质量浓度的氨氮标准样品和实际样品,用氨气敏电极法和纳氏试剂分光光度法进行同步测试。结果表明,2种分析方法在水样氨氮质量浓度在0. 159～2. 81 mg/L范围内具有良好的可比性、精密性和准确性。氨气敏电极法的检出限为0. 03 mg/L,平行6次测定样品的相对标准偏差为0. 4%～4. 2%,加标回收率为85. 0%～110%;纳氏试剂分光光度法的检出限为0. 025 mg/L,平行6次测定样品的相对标准偏差为0. 5%～6. 4%,加标回收率为93. 0%～99. 8%。同时氨气敏电极法在样品预处理、试剂配制和分析时间上要优于纳氏试剂分光光度法。氨气敏电极法能够满足地表水自动监测在线比对实际工作的需求,该方法具有良好的适用性。     

微波强化CWPO工艺CuO_x-CeO_2/GAC催化剂的制备及其对二甲亚砜的降解

以颗粒活性炭(GAC)为载体、铜为活性组分、铈为助剂组分、草酸钠为沉淀剂,采用浸渍焙烧法制得CuO_x-CeO_2/GAC催化剂。以H_2O_2为氧化剂,微波强化催化湿式过氧化氢氧化(CWPO)处理二甲亚砜(DMSO)初始质量浓度为1 000 mg/L的废水,处理3 min后DMSO去除率达93.8%。催化剂第7次使用时DMSO去除率仍保持在75%以上。初始废水pH在3~9范围内,DMSO去除率均在85%以上。助剂Ce的加入提高了催化剂表面活性组分的分散性和稳定性,使催化剂的活性稳定性和使用寿命显著提高。