Isolation and Chemical Characterization of Dissolved and Colloidal Organic Matter

An overview of the methods used for the isolation and characterization of organic matter in natural waters is presented. Commonly used techniques for the concentration and isolation of organic matter from water, such as preparative chromatography, ultrafiltration and reverse osmosis, and the methods used to analyze the organic matter obtained by these methods are reviewed. the development of methods to obtain organic matter that is associated with fractions of the dissolved organic carbon other than humic substances, such as organic bases, hydrophilic organic acids and colloidal organic matter are discussed. Methods specifically used to study dissolved organic nitrogen and dissolved organic phosphorous are also discussed.     

Non-point source-driven carbon and nutrient loading to Ganga River (India)

This study was designed to test whether the atmospheric deposition (AD) significantly influences gross primary productivity (GPP) and dissolved organic carbon (DOC) build-up in the Ganga River. We collected data for three consecutive years (2012–2014) along with 37 km river stretch with respect to AD-input of carbon, nutrients, and surface runoff chemistry to relate changes in the river water. We found strong linkages among carbon and nutrients in AD, surface runoff and in the river. The concentration of DOC in the river was highest in the rainy season while those of dissolved inorganic nitrogen and dissolved reactive phosphorus were highest in winter. Spatio-temporal changes in DOC indicated dependence on point- and non-point sources and within-system DOC build-up. The GPP in the river increased consistently over time and significantly correlated with AD-N (R^2?=?0.96, p?<?.001) and AD-P (R^2?=?0.97, p?<?.001). Basin level extrapolation showed that the Ganga River Basin receives 1.81?Tg organic-C, 2.77 Tg reactive-N, and 130?Gg reactive-P annually through atmospheric deposition. Non-point source contributions of carbon and nutrients to the river were substantially higher than those of point sources. The study has relevance for regional scale carbon and nutrient budgeting and action plans for integrated river basin management.     

Assessment of the Ecological Integrity of Traunsee (Austria) Via Analysis of Sediments and Benthic Microbial Communities

Since nearly one hundred years Traunsee experiences the import of tons of liquid and solid waste originating from salt and soda production. Today, the lake exhibits chloride concentrations of up to 170 mg L^-1 and 19% of the lake floor are directly or indirectly influenced by industrial deposits (ID). Based on the comparison of several microbial parameters in unaffected, directly affected and intermediate lake bottom sediments, the ecological integrity of the lake was evaluated. The highly alkaline ID, which were exclusively colonized by microorganisms, harbored a bacterial community reduced by a factor of 10 in abundance and biomass compared to undisturbed sediment areas within the lake. The bacterial community of ID was furthermore characterized by a reduced content of actively respiring cells (INT-formazan reduction), a lower frequency of dividing cells (FDC) and a significantly reduced cell and biomass production. A 80 to 90% reduction in carbon recycling is estimated for the area exclusively covered by ID. Protists, although occasionally absent from the industrial sediments, were in general found to be less sensitive to the contaminant stress. Differences in alkalinity and dissolved organic carbon (DOC) concentrations of sediment porewaters as well as the total organic content and C/N ratios of sediments partly explain the microbial pattern observed at the various sampling sites. Possible consequences of the continuous industrial tailings for the whole lake ecosystem and the validation of the ecological integrity are discussed.     

外源氮输入对湿地土壤有机碳矿化及可溶性有机碳的影响

采用室内模拟试验,在好气和淹水2个土壤水分条件下,研究了外源氮输入对沼泽湿地土壤有机碳矿化和土壤可溶性有机碳（DOC）含量的影响.结果表明,好气条件下,净氮输入量为1 mg·g^-1（N1）的氮处理水平对土壤有机碳矿化和DOC含量的影响不显著,而净氮输入量为2和5 mg·g^-1（N2、N3）时,土壤DOC含量显著增加,分别比对照（250.62 mg·kg^-1）增加了187.22％和203.25％,并显著促进了土壤有机碳的矿化;淹水条件下,外源氮输入则抑制了土壤有机碳的矿化, N1、N2、N3处理下土壤DOC含量分别比对照（642.52 mg·kg^-1）降低了88.34％、 82.69％、 80.04％;不同水分条件下,土壤DOC含量与有机碳的累积矿化量均呈显著正相关关系（r²分别为0.939、 0.843）,由外源氮输入引起土壤DOC含量的变化可能是导致土壤有机碳矿化差异的主要原因之一.研究结果还表明,伴随着沼泽湿地积水消退和外源氮输入的增多,将会加快湿地土壤有机碳的矿化和土壤DOC的淋失,造成湿地土壤有机碳的大量损失.     

UV/H_2O_2氧化处理水中去污剂

表面活性剂是一类特殊的有机污染物,在去污、洗衣、印染等废水中广泛存在.本文以某电厂实用的5种去污剂为研究对象,考察了UV/H2O2对5种去污剂的矿化能力,研究了H2O2和去污剂初始浓度、初始p H值、去污剂种类、辐照时间等因素对氧化效果的影响.结果表明,5种去污剂在254 nm处均无较强吸收,单独UV辐照对其降解效果不明显.当去污剂初始DOC浓度为50 mg·L-1,H2O2最佳投加量为1 m L·L-1,反应时间为90 min时,对5种去污剂的矿化率(即DOC去除率)在53%~87%,矿化率随去污剂种类的不同而不同.对去污剂的矿化率随着UV辐照时间的延长而增大,去除率曲线符合一级反应动力学方程.废水初始p H值对氧化效果的影响不显著,H2O2/DOC比值对氧化效果有显著影响.研究表明,UV/H2O2技术能高效矿化水中的去污剂,H2O2/DOC比值和UV辐照时间是影响氧化效率的关键因素.     

京密引水中不同形态天然有机物的卤代活性

用过滤、XAD－8和XAD－4树脂串联吸附等方法将京密引水中的天然有机物定量分离为悬浮固体、憎水有机物、腐殖酸类化合物,XAD－4酸和其它亲水有机物。分别对不同形态有机物进行氯化处理,测定了产物中的挥发性卤代烃。结果表明,京密引水中天然有机物的主要挥发性氯化产物是氯仿,此外还生成一溴、二溴氯甲烷及少量溴仿。溶解态腐殖酸类化合物的悬浮固态和悬浮固态有机物是生成氯仿的最主要母体。亲水有机酸也具有较高的卤代活性,而其它有机成分则表现出相对惰性。     

溶解性有机碳的主要组成对青鳉鱼铜急性毒性的影响

为揭示溶解性有机碳(DOC)的组成对生物配体模型(BLM)预测铜的生物毒性准确性的影响,研究了不同浓度黄腐酸(FA)、腐殖酸(HA)和两者不同浓度比例混合物影响铜对青鳉急性毒性。结果表明:在相同水质条件下,黄腐酸或腐殖酸浓度增加时,铜对青鳉的LC50均增加;两者共存时,当腐殖酸质量百分比从10%增至90%时,铜对青鳉的LC50也增加。当天然水中DOC的组成不确定时,可假设HA和FA的组成比例为1∶1,此时BLM预测铜对青鳉的LC50的偏差最小。     

Natural and Anthropogenic Factors Controlling the Dissolved Organic Carbon Concentrations and Fluxes in a Large Tropical River, India

Carbon studies in tropical rivers have gained significance since it was realized that a significant chunk of anthropogenic CO₂ emitted into the atmosphere returns to the biosphere, that is eventually transported by the river and locked up in coastal sediments for a few thousand years. Carbon studies are also significant because dissolved organic carbon (DOC) is known to complex the toxic trace metals in the river and carry them in the dissolved form. For the first time, this work has made an attempt to study the variations in DOC concentrations in space and time for a period of 19 months, and estimate their fluxes in the largest peninsular Indian river, the Godavari at Rajahmundry. Anthropogenic influence on DOC concentrations possibly from the number of bathing ghats along the banks and domestic sewage discharge into the river are evident during the pre-monsoon of 2004 and 2005. The rise in DOC concentrations at the onset of monsoon could be due to the contributions from flood plains and soils from the river catchment. Spatial variations highlighted that the DOC concentrations in the river are affected more by the anthropogenic discharges in the downstream than in the upstream. The discharge weighted DOC concentrations in the Godavari river is 3–12 times lower than Ganga-Brahmaputra, Indus and major Chinese rivers. The total carbon fluxes from the Godavari into the Bay of Bengal is insignificant (0.5%) compared to the total carbon discharges by major rivers of the world into oceans.     

中国典型城市固体废物可降解有机碳含量的测定与研究

城市固体废物填埋处理产生的甲烷是一种重要的温室气体,城市固体废物中可降解有机碳(DOC)含量是计算其甲烷排放量的重要因子之一.1996年IPCC指南给出了不同可降解有机碳的公式和不同类型固体废物可降解有机碳缺省值.该缺省值主要来自发达国家的文献,不能完全适合中国的实际情况.选择武汉和沈阳作为我国南方和北方城市的代表,分别在其老城区、新建城区、综合市场、食品超市、垃圾填埋场等区域进行固体废物采样,经过化学分析得到代表城市干基和湿基固体废物的含水率、含碳量和可降解有机碳含量,并对其成分特征进行分析,得到中国城市固体废物可降解有机碳含量推荐值.      

Modelling geochemical and microbial consumption of dissolved oxygen after backfilling a high level radiactive waste repository

Dissolved oxygen (DO) left in the voids of buffer and backfill materials of a deep geological high level radioactive waste (HLW) repository could cause canister corrosion. Available data from laboratory and in situ experiments indicate that microbes play a substantial role in controlling redox conditions near a HLW repository. This paper presents the application of a coupled hydro-bio-geochemical model to evaluate geochemical and microbial consumption of DO in bentonite porewater after backfilling of a HLW repository designed according to the Swedish reference concept. In addition to geochemical reactions, the model accounts for dissolved organic carbon (DOC) respiration and methane oxidation. Parameters for microbial processes were derived from calibration of the REX in situ experiment carried out at the Asp? underground laboratory. The role of geochemical and microbial processes in consuming DO is evaluated for several scenarios. Numerical results show that both geochemical and microbial processes are relevant for DO consumption. However, the time needed to consume the DO trapped in the bentonite buffer decreases dramatically from several hundreds of years when only geochemical processes are considered to a few weeks when both geochemical reactions and microbially-mediated DOC respiration and methane oxidation are taken into account simultaneously.