珠江水体中有机物分布、组成及与消毒副产物生成的关系

以珠江水体为研究对象,利用XAD树脂分离溶解性有机物(DOC)中的腐殖质及其他有机组分.考察了珠江中DOC的质量浓度、组成分布、SUVA254和三卤甲烷生成势(THMFP),并分析有机物的组成与三卤甲烷生成势(THMFP)之间的关系.结果表明,珠江水域在广东省内的DOC质量浓度为0.7～33.0 mg.L-1,THMFP为30.39～1 091.52μg.L-1,两者呈正比例线性相关.在空间分布上,各支流的DOC质量浓度和THMFP均沿下游方向逐渐增加,而腐殖质在DOC中所占的质量分数却沿下游方向逐渐递减.在加氯实验中,腐殖质是珠江中最主要的消毒副产物前驱物(产生了珠江中64.6%的三卤甲烷),其三卤甲烷生成活性(STHMFP)是其他有机组分的2倍以上.另一方面,SUVA254和腐殖质的质量分数呈正比例线性相关,说明SUVA254对珠江水中消毒副产物前驱物也有一定的指示作用.     

贵州威宁草海湿地水体中有机碳时空分布特征及来源辨析

有机碳是陆地水生生态系统碳循环重要组成部分,湿地在维持岩溶碳汇稳定性方面具有十分重要的作用,揭示岩溶湿地水体中的有机碳时空分布特征及来源有助于明晰岩溶流域碳循环过程。本文以贵州威宁草海岩溶湿地为研究对象,对其丰、枯水期湿地水中溶解有机碳(DOC)、颗粒有机碳(POC)含量以及颗粒有机质(POM)碳、氮同位素等指标的测定,分析草海湿地水中POC、DOC浓度时空分布特征,探讨了水体中有机碳的来源。结果表明:草海湿地水体有机碳总体上以DOC为主,丰水期DOC变化范围为4.25～12.58 mg/L,平均值为8.19±1.49 mg/L,枯水期变化范围为4.79～15.93 mg/L,平均值为8.78±3.01 mg/L,丰水期略低于枯水期,DOC来源较为复杂,不同水文期受到外源和内源不同程度的影响;DOC在空间上丰水期呈现西部偏低,东及东南部偏高的分布特征,枯水期呈现南及西南部偏低,北及东北部偏高的分布特征。草海湿地水体丰水期POC变化范围为0.35～3.39 mg/L,平均值为1.13±0.78 mg/L,枯水期变化范围为0.32～1.84 mg/L,平均值为0.79±0.35 mg/L,丰水期高于枯水期;POC在空间上两期都呈现出中西低、中东高的分布特征。丰水期颗粒有机质的δ¹³C、δ¹⁵N值变化范围分别为-30.13‰～-14.80‰和-9.69‰～4.72‰,平均值分别为(-22.54±2.78)‰和(-2.88±2.89)‰,该时期POC以陆源有机质贡献为主;枯水期颗粒有机质的δ¹³C、δ¹⁵N值变化范围分别为-29.13‰～-21.91‰和-0.14‰～9.15‰,平均值分别为(-25.12±2.04)‰和(3.23±1.78)‰,该时期POC主要来源于沉积物。     

Turnover of dissolved organic carbon fuels nocturnal CO2 emissions from a headwater catchment reservoir, Southeastern China: Effects of ecosystem metabolism on source partitioning of CO2 emissions

Dam reservoirs in headwater catchments, as critical zones for their proximity to terrestrial sources, play important roles in dissolved organic carbon (DOC) cycling. However, the effects of ecosystem metabolism (EM) on DOC cycling are not well known. Here, in-situ diurnal and monthly observations were conducted to measure EM (including gross primary production (GPP), ecosystem respiration (ER) and heterotrophic respiration (HR)), DOC turnover and CO₂ emissions in a headwater catchment reservoir in Southeastern China in 2020. Our study showed the nocturnal CO₂ emission rate was about twice as high as in daytime, and was strongly driven by EM. The values for DOC turnover velocity ranged from 0.10 to 1.59 m/day, and the average DOC turnover rate was 0.13 day⁻¹, with the average removal efficiency of 12%. The contribution of respired DOC to daily CO₂ emissions ranged from 17% to 61%. The accumulated efficiencies were estimated to be 13% for the selected 15 reservoirs throughout the Changjiang River network, corresponding to about 0.34 Tg C/year of the respired DOC. The modified CO₂ flux was 0.75 Tg C/year, and respired DOC accounted for about 45% of total emitted CO₂ from the 15 larger reservoirs. Our research emphasizes the necessity of incorporating the effects of EM into studies of reservoir DOC removal and CO₂ emissions.     

Removal of chromophoric dissolved organic matter under combined photochemical and microbial degradation as a response to different irradiation intensities

Throughout the freshwater continuum, Dissolved Organic Carbon (DOC) and the colored fraction, Chromophoric Dissolved Organic Material (CDOM), are continuously being added, removed, and transformed, resulting in changes in the chromophoricity and lability of organic matter over time. We examined, experimentally, the effect of increasing irradiation-intensities on the combined photochemical and microbial degradation of CDOM and DOC. This was done by using a simulated mixed water column: aged water from a humic lake was exposed to four irradiation-intensities – representing winter, early and late spring, and summer conditions (0.10, 0.16, 0.36, and 0.58 W/m²) – and compared with dark controls over 37 days. We found a linear relationship between CDOM degradation and irradiation-intensities up to 0.36 W/m²; the degradation rate saturated at higher intensities, both at specific wavelengths and for broader intervals. After 37 days at high irradiation-intensity, CDOM absorption of irradiation at 340 nm had been reduced by 41%; 48% of DOC had been removed and DOC degradation continued to increase. Aromaticity (SUVA₂₅₄) declined significantly over 37 days at the two lowest but not at the two highest UV- intensities; levels in unexposed control water remained constant. Direct observations of the humic lake showed that CDOM absorption of irradiation (340 nm) declined by 27% from winter to summer. A model based on hydrological CDOM input and CDOM degradation calculated from field measurements of UV-radiation and experimental CDOM degradation with UV-exposure from sunlight accurately predicted the annual course as observed in the lake. With no external CDOM input, 92% of the CDOM could be degraded in a year. The results support the notion that combined photochemical and microbial CDOM degradation can be remarkably higher in lakes than previously thought and that humic lakes retain their color due to light absorption by ongoing CDOM input.     

DOC技术对柴油机排放颗粒物数浓度的影响

利用ELPI(电子低压冲击器)对不同转速、不同负荷以及安装DOC(氧化催化转化器)前后颗粒物排放及粒径分布进行了研究. 结果表明:无论安装DOC与否,柴油机排放颗粒物数浓度均随发动机转速的增加而增加. 增大负荷,颗粒物数浓度峰值处的粒径也随之增大. 经过DOC催化转化后,柴油机排放颗粒物的大部分仍呈单峰正态分布,且DOC对核模态粒子的氧化转化效率较高. 经过DOC后,在低转速下,不同粒径的颗粒物数浓度均有所降低;中、高转速下,DOC对粒径大于120 nm的颗粒物数浓度无明显降低作用.      

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.     

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。