Fluorescence spectroscopic studies of the effect of granular activated carbon adsorption on structural properties of dissolved organic matter fractions

This work investigated the effect of granular activated carbon adsorption (GACA) on fluorescence characteristics of dissolved organic matter (DOM) in secondary effluent, by means of excitation–emission matrix (EEM) spectra, the fluorescence regional integration (FRI) method, synchronous spectra, the fluorescence index defined as the ratio of fluorescence emission intensity at wavelength 450 nm to that at 500 nm at excitation (λ_ex)=370 nm, and the wavelength that corresponds to the position of the normalized emission band at its half intensity (λ_0.5). DOM in the secondary effluent from the North Wastewater Treatment Plant (Shenyang, China) was fractionated using XAD resins into 5 fractions: hydrophobic acid (HPO–A), hydrophobic neutral (HPO–N), transphilic acid (TPI–A), transphilic neutral (TPI–N) and hydrophilic fraction (HPI). Results showed that fluorescent materials in HPO–N and TPI–N were less readily removed than those in the other fractions by GACA. The relative content of fluorescent materials in HPO–A, TPI–A and HPI decreased whereas that in HPO–N and TPI–N increased as a consequence of GACA. Polycyclic aromatics in all DOM fractions were preferentially absorbed by GACA, in comparison with bulk DOM expressed as DOC. On the other hand, the adsorption of aromatic amino acids and humic acid-like fluorophores exhibiting fluorescence peaks in synchronous spectra by GACA seemed to be dependent on the acid/neutral properties of DOM fractions. All five fractions had decreased fluorescence indices as a result of GACA. GACA led to a decreased λ_0.5 value for HPO–A, increased λ_0.5 values for HPO–N, TPI–A and HPI, and a consistent λ_0.5 value for TPI–N.     

黄棕壤中不同粒径组分的提取分级与表征

以去离子水为分散剂,采用连续分级法,结合使用筛分、沉降、离心及错流超滤(CFF)等技术,将60目黄棕壤提取分级为细砂粒(50~250μm)、粉粒(5~50μm)、粗黏粒(1~5μm)、细黏粒(0.1~1μm)、纳米微粒(<0.1μm)5个组分;采用激光粒度仪、透射电镜(TEM)、X射线衍射(XRD)等方法对分级结果进行了表征.激光衍射粒度分析所测得各组分实际粒径分布结果与划定的粒径分级范围均很好吻合,表明按上述方法对土壤颗粒进行分级是有效、可行的.TEM观察到的纳米粒级成分呈规则球形,绝大部分颗粒粒径在20~40nm之间,有少部分大颗粒团聚体存在.     

Variations in δ13C of water–soluble leaf and phloem organic matter of Platycladus orientalis: influences of photosynthetic and post–photosynthetic fractionation

Analysis of variations in water–soluble organic matter (WSOM) δ¹³C of leaves and phloem can efficiently describe the δ¹³C distributions within plants and identify the temporal variation of δ¹³C. In this study, WSOM δ¹³C values of both leaves and phloem (twig, stem, and root) of Platycladus orientalis were measured during seven sunny days, including 2–hour interval measurements at three days for diel pattern analysis and 6–hour interval measurements at the remaining four days for day–to–day variation analysis. Analysis of WSOM δ¹³C in different plant organs showed that ¹³C was generally depleted from leaves to twigs, then enriched in stems and subsequently depleted in roots. Stems were significantly ¹³C–enriched compared to twigs (p?<?0.05), while δ¹³C differences between stems and other organs and among leaves, twigs and roots were not significant (p?>?0.05). No clear diel patterns in δ¹³C of leaves and phloem were found. Daily average δ¹³C values indicated that all plant organs had more positive values on sunny days during the dry season than during the wet season. Both photosynthetic and post–photosynthetic fractionation influence variations in WSOM δ¹³C. These results have implications for research on plant physiology and plant water use.     

Spatial variation of phosphorus fractionation in the coral reef sediments of Lakshadweep Archipelago,Indian Ocean

Surface sediments were collected from the shore and lagoons of Kavaratti, Kadamat and Agatti islands of Lakshadweep Archipelago during May 2015 and analysed for the spatial distribution of the micronutrient element, phosphorus. Phosphorus was separated by sequential extraction procedure into five fractions – exchangeable (Ex-P), iron bound, (Fe-P), calcium bound (Ca-P), organic and residual fractions (OP) and total phosphorus (TP). The average relative contribution of each P species to TP was: OP?>?Ca –P?>?Ex – P?>?Fe – P. The high concentration of organic and residual phosphorus (87–96%) compared to inorganic phosphorus is particularly evident at stations characterised by higher total phosphorus concentrations. Among the three forms of IP in the sediments, Ca-P was dominant at all stations. The OC/OP ratio ranged from 3 to 163 in the sediments, suggesting that the organic matter in sediments had been subjected to degradation. Hence, the major contribution towards organic and residual phosphorus form is from the residual fraction comprising biologically resistant or non-available phosphorus form composed of refractory materials. The concentration of phosphorus reported in the present study is higher than that of the earlier studies in Lakshadweep, indicating a terrestrial and anthropogenic in?uence on the sediment.     

水体冻结过程中卤乙酸前体物在水-冰体系中的分配研究

通过室内模拟试验,研究了水体冻结过程中,水体中溶解性有机物(DOM)和卤乙酸前体物在水-冰体系中的分配规律.按照DOM在XAD树脂上的吸附特性将其分为5个部分:疏水性有机酸(HPO-A),疏水性中性有机物(HPO-N),过渡亲水性有机酸(TPI-A),过渡亲水性中性有机物(TPI-N)和亲水性有机物(HPI).结果表明:在水体冻结过程中,5种DOM组分在水相中的DOC浓度均随冷冻时间的增长而增加,呈现冷冻浓缩效应.与溶解性有机碳(DOC)所表征的整体有机物相比,5种DOM组分中的卤乙酸(HAAs)前体物更倾向于停留在水相中浓缩.在5种DOM组分中,HPI是主要的HAAs前体物.5种DOM组分在未冻结水中的UV-254与HAAFP均表现出一定相关性,其中HPO-A, TPI-A和HPI的UV-254与HAAFP达到极显著水平.然而在融冰水中,这5种DOM组分的UV-254与HAAFP的相关性均不显著.     

Separation of Organic Materials and Metallic Elements from Marine Waters by the Operation of Gas-Bubble Extraction

A laboratory experimental investigation was conducted to define the action of rising bubbles with respect to heavy-metal enrichment at the sea surface. Analytical data (HMDE-differential pulse anodic stripping voltammetry technique) show possible enrichments of organic-bound Zn, Cu, Cd and Pb at the top of a laboratory bubble-extraction column filled with water samples collected in the Southern Tyrrhenian Sea. In consideration of analogy between natural and laboratory bubble-extraction processes, laboratory results, i.e., enriched-over-original concentration ratios, make it possible to assess the intrinsic heavy-metal flotation capability in marine waters.     

融雪期城市河流中溶解性有机物的时空分布特征

以沈阳市新开河为研究对象,考察了河水中溶解性有机物(DOM)含量的月份变化,以及融雪期河水中DOM含量和特性的时空变化规律.利用XAD树脂将DOM分为5个部分:疏水性有机酸(HPO-A),疏水性中性有机物(HPO-N),过渡亲水性有机酸(TPI-A),过渡亲水性中性有机物(TPI-N)和亲水性有机物(HPI).结果表明,融雪期河水中的溶解性有机碳(DOC)浓度较高,HPO-N和TPI-N是融雪期河水中的主要DOM组分,并且DOM中的荧光物质主要为类芳香族蛋白质荧光物质和类腐植酸荧光物质.融雪期水体中的DOC、波长254nm处的紫外吸光度(UV-254)和三卤甲烷生成势(THMFP)呈先降低然后波动最后升高的变化趋势.特征紫外吸光度(SUVA)和三卤甲烷生成活性(STHMFP)与以上三者的变化规律相反.融雪期河水中的DOC受污水排放影响大,有排污口处的DOC含量明显大于其他区域.污水排放也使受纳水体中UV-254对THMFP的指示作用减弱.     

金昌市郊农田土壤Cu,Zn,Ni形态分布特征与生物有效性评价

通过野外调查和室内测试分析,研究了金昌市郊农田土壤重金属Cu,Zn和Ni的形态特征,并以麦粒中重金属含量为重点进行了Cu,Zn和Ni的生物有效性评价.结果表明,研究区域土壤重金属Cu和Ni污染严重;Cu的主要存在形态为有机结合态,Zn的主要存在形态为残渣态,而Ni的主要存在形态为潜在可利用态;三种元素的生物有效性大小顺序为NiZnCu.对麦粒中重金属健康风险进行评价反映出麦粒中Ni含量对人体健康风险较大,而Cu和Zn对人体健康风险较小.逐步回归分析结果表明,农田土壤中Cu可交换态和碳酸盐结合态对麦粒中Cu含量贡献最大,而对麦粒吸收Zn和Ni贡献最大的形态分别为Zn的碳酸盐结合态和Ni的可交换态、碳酸盐结合态、铁锰氧化态和有机结合态.土壤重金属Cu,Zn和Ni各形态分配系数较总量和各形态含量更适合表征本研究区域土壤重金属的生物有效性.     

农业常用有机物料中水溶性有机物的理化性质特征

以水稻土水溶性有机物(DOM)为对照,采用物理化学和光谱学实验研究了农业上常用有机物料:猪粪、绿肥和污泥DOM的理化性质差异.结果表明,水稻土、污泥、猪粪和绿肥DOM含量分别为122, 23793, 12904, 380560mgC/kg.若施用等量有机物料,带入土壤的DOM量最多的应是绿肥.不同有机物料DOM中大分子组分含量高低顺序为:水稻土(51.08%)>猪粪(41.25%)>污泥(23.33%)>绿肥(7.36%);而极性组分含量的顺序则相反,水稻土(10.71%)猪粪DOM(1.12)>污泥DOM(1.11)>绿肥DOM(0.98),紫外图谱也证实了这一点.     

水稻不同生育期土壤砷形态分布特征及其生物有效性研究

采用田间原位试验和Tessier连续提取方法,在水稻（Oryza sativa L.）不同生育期研究了重金属复合污染高、中、低3个水平下的土壤砷的形态分布特征及其生物有效性。结果表明：在水稻不同生育期中,土壤各种形态的砷质量分数均表现为高污染水平土壤〉中等污染水平土壤〉低污染水平土壤;土壤中砷在水稻整个生育期均以残留态为主,占90%以上,交换态砷所占比例最低,不到0.5%;不同形态砷之间大都显著正相关,但是两种有效性较高的砷形态（交换态和碳酸盐结合态）与有机态砷之间的相关性较差;土壤砷的生物有效性表现为高污染水平土壤〉中等污染水平土壤〉低污染水平土壤,且随着水稻生育期的延长,土壤砷的生物有效性逐渐升高。