Determination of Hg and MeHg complexation with dissolved organic matter by fluorescence quenching titration

In natural waters inorganic mercury （Hg） and methylmercury （MeHg） are complexed with a variety of inorganic and organic ligands, such as OH^-, Cl^-, sulfide, thiols, and dissolved organic matter （DOM）. The bioavailability and toxicity of Hg and MeHg are related to their speciation, instead of their total concentrations. Among these species, Hg-DOM and MeHg-DOM complexes are the least known, due to the complexity and site-specificity of DOM in natural waters. Here we report the complexation between DOM and Hg or MeHg using fluorescence spectroscopy. The Suwannee River fulvic acid, peat humic acid, amino acid typotophan, and natural organic matter from the Suwannee River, Nordic River, and Delta Marsh were studied at their respective excitation/emission maxima,     

Effects of water chemistry and concentrations of dissolved organic matter on its fluorescence characteristics and molecular conformation

Previous studies showed that water chemistry and concentrations of dissolved organic matter (DOM) could affect its molecular conformation and binding characteristics with hydrophobic organic contaminants (HOCs). However, the conformational change of DOM resultant from water chemistry and concentrations of DOM was not extensively investigated; therefore, the contradictory reports regarding the binding property with HOCs were available in literature. In this study, the effects of ionic strength, pH and DOM concentrations on the fluorescence properties of two humic acids (HA), namely Fluka HA and Amherst HA, were investigated by three-dimensional excitation-emission matrix fluorescence spectroscopy (3DEEM) and steady-state fluorescence polarization (FP) techniques. The results not only corroborated previous observations obtained by other investigators, but revealed some new information about the fluorescence properties and molecular conformation of the humic acids under different water chemistry and DOM concentration conditions, which could shed light on its binding mechanisms and binding properties with HOCs.     

水体中溶解有机物的特性与测量

系统评述了水体中溶解有机物的特性及测量方法。介绍了水体中溶解有机物的研究概况,指出了开展水体中溶解有机物定量监测的必要性;详述了水体中溶解有机物的激光诱导荧光测量方法、对水体中有机物荧光光谱进行分析的特征光谱荧光标记技术和荧光强度归一化处理技术,以及利用激光诱导荧光方法测量水体中溶解有机物浓度的标定方法;综述了多种因素对利用激光诱导荧光方法测量的影响。     

夏季丰水期河流输入对太湖有色可溶性有机物的贡献

结合2008年夏季丰水期对太湖上游直湖港、大浦河、长兜港3条河流有色可溶性有机物(CDOM)吸收和三维荧光的测定分析,探讨了夏季丰水期时河流输入对太湖中CDOM的贡献.3条河流中直湖港CDOM浓度最高,大浦河次之,长兜港最低,反映了太湖北部外源河流污染物输入大于西南部.3条河流内CDOM吸收α(355)的均值为(4.7...     

Optical characteristics and solar photodegradation of dissolved organic matter in Arkansas River, USA

Dissolved organic matter （DOM）, a mixture of numerous organic compounds of 30 to 300000 D, exists in all natural water resources including rivers, lakes and oceans, and plays a very important role in global carbon cycle and ecology. The DOM molecules absorb UV light strongly in short wavelengths and prevent microorganisms from being damaged by solar UV irradiation. Meanwhile, the large DOM molecules are then photodegraded into inorganic carbon and smaller organic molecules which are easier for bacterioplankton to digest. The Arkansas River is one of the largest rivers in the US, and a major input of organic materials to the Mississippi River and Gulf of Mexico. However, the photochemical properties of the DOM in the river water have not been investigated. To study this photodegradation process of the Arkansas River, water samples from the river were collected, filtered, sealed into quartz flasks, and exposed to sunlight for up to 15 hours. Some samples were retrieved from the flasks at certain time intervals. The intensity of the sunlight was measured during the exposure process at 30 min to 1 hr intervals. UV-vis absorption, fluorescence emission, 3D fluorescence spectra and DOM concentrations were determined for all retrieved samples. It was found that the total DOM concentration decreased while the dissolved inorganic carbon （DIC） concentration increased in the samples. UV absorption and fluorescence intensity of DOM decreased exponentially. The disappearance rate of UV absorption varied with wavelength. The loss of integral fluorescence was about 2.6 times that of the UV absorption at the excitation wavelength. In addition, the quantum yields also decreased, and the peak position of 3D fluorescence scan shifted to shorter wavelength.     

洞穴溶解有机质组分和循环过程的季节变化特征

溶解有机质（DOM）是岩溶碳汇的关键部分和重要的碳源,但是对于DOM在岩溶含水层中的性质和代谢过程的研究仍然有限。本研究以重庆雪玉洞地下河为例,对洞穴有机碳的来源、组成以及微生物作用对季节补给源变化的响应进行探讨,为进一步了解微生物介导的有机碳转化过程提供研究基础。运用三维荧光EEM研究水体有色溶解有机质（CDOM）的性质和组分并反演地下河水中有机质的来源和组成,结合地下河水水化学特征和16S rDNA细菌群落及功能多样性的季节变化特征,以了解季节性补给源的变化对洞穴地下水DOM输入和性质的影响。结果发现,雪玉洞地下河水以微生物内源有机质为主（61%~77%）,降雨是引起岩溶给地下河水中CDOM光谱特征变化的最重要因素,雨季外源有机质输入增加,地下河水中外源有机碳组分含量和芳香性、腐殖酸类物质增加,细菌群落多样性和代谢功能基因随之变化,洞穴中向外输出的外源有机碳增加;旱季地下河水滞留时间和蒸发作用增强,因而微生物对有机质的代谢降解过程更加充分,向洞外输出的有机碳以内源为主。本研究有助于增加对岩溶洞穴地下水系统中微生物对有机碳转化过程的理解。     

用三维荧光谱图分析原水输送过程中藻类和有机物的变化

采用新型分析技术三维荧光谱图方法对深圳东江水源工程水体中藻类进行了荧光分析。实验结果表明,水体中有较丰富的藻类,其中蓝藻、绿藻呈优势藻种,实验期间沿程水体叶绿素a浓度在1.71~16.43μg/L之间,藻密度在72.92万~1 375万个/L之间。三维荧光方法能较好表征水体中生长藻类种类和数量,三维荧光强度F(A.U)与叶绿素a浓度Chla(μg/L)、藻密度N(104个/L)呈较好的线性关系。三维荧光方法能较好的鉴别水体中可溶性有机物腐殖酸和蛋白质,并表征其含量多少。     

黄河口有机碳的时空输运特征及其影响因素分析

通过2004年4月,2004年9月,2005年9月,2006年4月4个航次,结合2003年8月对河道感潮带的连续同步观测,对低流量下黄河口有机碳的输运特征进行了考察。结果发现:黄河输入至河口的悬浮物中颗粒有机碳(POC)含量约为0.51%,主要以陆源输入为主,几乎不受季节变化影响,由于大量POC含量低的陆源泥沙的稀释作用,浮游植物对总颗粒有机碳的贡献只有在悬浮物含量(TSS)<200mg/L时才能显现出来;黄河口TSS超过455mg/L时,有机碳入海以颗粒有机碳为主;反之,以溶解有机碳为主。黄河口悬浮物在低盐度区沉降作用前后的中值粒径降低,Φ>16μm的悬浮物的沉降作用比Φ<16μm的悬浮物更为剧烈,POC含量随悬浮物粒径的降低而升高,黄河携带的颗粒有机碳80%以上集中在Φ<16μm的TSS中;低流量下,黄河口最大混浊带对POC的过滤效率为65%,混浊带对POC的过滤效应能造成黄河口POC的有效通量被高估;由于受黄河口沉积物向水体解析DOC的影响,在盐度小于10时,DOC几乎不受海水稀释作用的影响,但在盐度大于10的区域DOC与盐度表现出良好的负相关关系,黄河口枯、丰水期淡水端溶解有机碳的有效浓度分别高于实测最高值20%和10%左右,从而造成黄河口DOC有效通量被低估。     

洱海沉积物间隙水中溶解有机质的地球化学特性

对洱海沉积物间隙水中溶解有机质(DOM)含量、紫外可见吸收、荧光以及分子量等的垂直分布特征进行了研究。结果表明,DOC含量在沉积物水界面明显富集,随后急剧下降,6cm处达到最小值,随后呈上升趋势。DOC与吸光度值、荧光发射光谱强度之间具有一定的线性相关关系。DOM的E3/E4值范围在1～6之间,绝大多数在1～35之间。表征DOM中腐殖质来源的指标荧光指数值处于148～159之间,说明DOM以陆源输入为主。此外,洱海沉积物间隙水DOM分子量分布呈多峰分布模式,重均分子量(M_w)值在1462～1953Da之间,数均分子量(M_n)值在547～900Da之间,多分散性系数ρ值在202～305之间。随着沉积深度增大,M_w和M_n有略微的增大趋势,但变化不大。沉积物的氧化还原条件、微生物活动以及铁、锰氧化物等在沉积剖面的差异是控制间隙水中DOM各种地球化学特性的主要因素。     

卤水中溶解性有机质的光谱学性质和光降解行为研究

卤水中溶解性有机质(dissolved organic matter,DOM)会对盐田日晒工艺和产品质量产生不利影响,如盐田卤水的蒸发速率减缓、蒸发度减小以及提取的矿物产品带有刺鼻的气味、浓重的颜色等。因此,对具有资源开发利用价值的卤水体系中DOM结构和性质的研究可以为后续DOM的有效去除或在DOM共存体系中调控无机盐结晶工艺路线提供有效的指导意见。本文以自然界中广泛存在的两种不同类型的卤水体系,即盐湖卤水DOM(SLDOM)和油田卤水DOM(OFDOM)为研究对象,采用溶解性有机碳(dissolved organic carbon,DOC)分析、光谱学分析和平行因子分析等手段对DOM的含量、分子量分布特征、光谱学结构和光降解行为开展了研究。DOC和荧光分析表明SLDOM和OFDOM的DOC含量和生物指数(BIX)值相似;与OFDOM相比,SLDOM的腐质化指数(HIX)值和高分子量组分(HMW)比例偏高;特别吸收光谱(SUVA₂₅₄)和糖类化合物含量检测结果表明,SLDOM和OFDOM的HMW组分中含有的芳香类和糖类化合物所占比例比低分子量组分(LMW)高;三维荧光谱图分析(EEM)结果表明,SLDOM主要以腐殖质类物质为主,而OFDOM以蛋白质类组分为主。此外,DOM的荧光组分在不同分子量中的分布也存在明显差异:对于SLDOM,富里酸主要分布在HMW DOM中,而腐殖酸主要在LMW DOM中;对于OFDOM,芳香胺类蛋白组分主要分布在HMW DOM中,色氨酸和酪氨酸类蛋白组分主要分布在LMM DOM中。在光降解实验中,SLDOM和OFDOM的DOC含量随光照时间增加而逐渐减少,分别下降了29.32%和15.11%。进一步的分析表明,光照过程中两种卤水中糖类化合物均减少,小分子量的DOM优先分解。此外,在光照过程中SLDOM芳香类化合物增加,腐质化程度基本不变;OFDOM芳香类化合物减少,腐质化程度增加。EEM平行因子分析(PARAFAC)结果表明,SLDOM荧光组分在光降解过程中荧光强度增加,而OFDOM荧光强度减少。     

Ultraviolet absorbance titration for the determination of conditional stability constants of Hg（Ⅱ） and dissolved organic matter

Strong interaction between natural dissolved organic matter （DOM） and Hg（Ⅱ） may influence the transport, conversion, toxicity and bio-validity of mercury in the environment. In this paper ultraviolet （UV） absorbance titration was employed for the first time for the determination of the conditional stability constants of Hg（Ⅱ） and （DOM）. With increasing Hg（Ⅱ） concentrations, the UV absorbance of fulvic acid, humic acid, and DOM in river increases progressively. By linear and non-linear model fitting, the conditional stability constants （lgK） of Hg（Ⅱ） and DOM were worked out to be 3.54-4.93 and 3.64-4.85, respectively. The results are consistent with those acquired by the typical fluorescence quenching titration method, with the maximum relative error of lgK being 2.6% and the average relative error being 0.2%. The UV absorbance titration method has the advantages of rapid determination, simple performance, and it will probably become a new approach to studying interactions between DOM and trace metallic ions.     

东海陆架泥质区沉积有机质的物源分析

色谱和色谱／质谱分析表明，济州鸟西南泥质区正构烷烃、姥鲛烷、植烷、藿烷和甾烷等生物标志物的特征与现代长江口、老黄河口和新黄河口的河流沉积物均区别很大，该泥质区的沉积有机质主要来源于海洋低等生物（如细菌和藻类等）以及陆源高等植物的输入，表现为不同来源和成熟度的生物标志物的混合，同时该泥质区沉积有机质与矿物碎屑沉积物来源不尽相同。长江口泥质区正构烷烃高相对分子质量部分与长江口沉积物相似，正构烷烃和藿烷所反映的有机质成熟度高于现代长江和老黄河口沉积物，甾烷的成熟度与长江相仿而明显高于老黄河口沉积物。长江口泥质区的沉积有机质主要来源于长江输入的陆源高等植物碎片和海洋源的低等生物。东海陆架近岸与远端泥质区沉积有机质的物源很不相同。     

骆驼山煤矿不同含水层水中荧光性DOM分布特征

结合骆驼山煤矿不同含水层水文地质条件,通过检测分析各含水层水中天然有机质三维荧光光谱、总有机碳TOC和无机阴离子,研究了荧光性溶解有机物(Dissolved Organic Matter,DOM)的分布特征,结果表明:TOC和有机物在254 mm波长紫外光下的吸光度UV₂₅₄整体上随着含水层层位加深而减少,奥灰水中TOC和UV₂₅₄比其他水体分别低2~3.3倍和2.4~4.7倍;有机物芳香度也逐渐降低,紫外吸光度SUVA值在地表水、第四系水、砂岩水和奥灰水中分别为3.28、2.27、2.24和1.96。地表水和第四系水的三维荧光光谱(3DEEM)图存在5个指纹区域,随着地层层位的加深,水中有机物总体上呈递减趋势,最深层的奥灰水中没有酪氨酸、疏水性有机酸和海洋性腐植酸,而色氨酸的荧光强度比其他水体都高,表明地下水中有机物会反应生成色氨酸类有机物。奥灰水中TOC随着地下水流向逐渐减少(从0.27 mg/L减少至0.22 mg/L);有机物反应生成色氨酸,导致色氨酸FI随着水流而逐渐增加;根据3DEEM光谱图,骆驼山煤矿区奥灰水中有机物比较稳定,能够明显区分出其作为突水水源的特征离子。     

不同地质年代煤矸石中有机质的溶出特征对比

分别以神东矿区补连塔矿侏罗纪煤矸石和保德矿二叠纪煤矸石为研究对象,通过浸泡实验,结合三维荧光光谱测试技术及平行因子分析法,对比研究2种煤矸石中有机质的溶出特征,这对于开展煤矿区地下水库水处理机理研究具有重要意义。研究结果表明：由于煤矸石自身矿物组成不同,补连塔矿煤矸石浸泡液中总离子质量浓度高于保德矿,且2种煤矸石浸泡液均呈弱碱性;其中补连塔矿煤矸石溶解性有机质（DOM）中含有较多的共轭双键或苯环类简单芳香族化合物,以富里酸和分子量较大的陆源类腐殖质为主,且含量普遍高于保德矿,而保德矿煤矸石中富里酸和酪氨酸类有机质较多。根据DOM样品荧光指数（FI）、生物源指数（BIX）、腐殖化指数（HIX）的计算结果,2种煤矸石中DOM主要为内源有机质,并具有较强的自生源特征,且煤矸石形成地质年代越早,煤矸石DOM样品的\     

Phosphorus features in FT-IR spectra of natural organic matter

Fourier-Transform Infrared （FT-IR） spectroscopy has been used extensively to characterize natural organic matter （NOM）. Absorption bands at 1100-1000 cm^-1 in the FT-IR spectra of NOM have been frequently assigned to alcoholic and polysaccharide C-O stretching or to vibrations of SiO2-related impurities. However, these interpretations do not consider that a strong band associated with P-O bonds of phosphate also appears in the same region. We evaluated the correlation between absorbance in this region and P content of 19 NOM samples from terrestrial, aquatic and plant shoot sources. In the spectra of 10 humic and fulvic acid samples, shoulder to minor bands appeared around 1050 cm^-1. Absorbance intensity at 1050 cm^-1 （Y） was linearly related to P content （X） by the following： Y=4.38X＋0.3 l, with R2=0.90. We did not observe such a close correlation between absorbance and P content in two aquatic NOM samples. Apparently, this is because the aquatic NOM samples were concentrated by reverse osmosis, which would have concentrated not only humic and fulvic acids but also other soluble organic solutes present in natural waters. In the FT-IR spectra of seven dissolved organic matter （DOM） samples obtained from dried plant shoots, broad and/or multiple bands around 1075 cm^-1 were observed with a shoulder at 977 cm^-1. These characteristics were more like those of organic phosphate compounds （such as inositol hexaphosphate）. However, solution 31P nuclear magnetic resonance spectroscopic analysis showed no significant amount of organic phosphate present in these samples.     

Organochlorine pesticides characteristics in water column of strategic drinking water sources in the Yangtze estuary

Biandansha, Qingcaosha and Meimaosha sands located respectively in the upper, middle and lower reaches of the Yangtze （Changjiang River） estuary are regarded as strategic drinking water sources of Shanghai City. In the coming decade, the Qingcaosha Reservoir will first be built and gradually take the place of present water sources in the Huangpu River. However, there is little report on the occurrence of persistent organic pollutants （POPs） such as organochlorine pesticides （OCPs） in those strategic water sources. Water samples collected from those strategic water sources were filtered in-situ by Whatman GF/F filters in April 20-23, 2006. Pesticides in the filtrates were enriched on ENVI-18 solid phase extraction （SPE） tubes. OCPs eluted from SPE tubes were determined by GC-μECD method with a mixed standard solution of 20 OCPs compounds. Pentachloronitrobenzene was added as internal standard. Total concentrations of OCPs varied between 15.1 and 83.1 ng/L in water samples from Shanghai strategic water sources. A half of twenty objective OCPs compounds including DDTs were not detected. In Qingcaosha waters, there were six compounds such as a-HCH, dieldrin, endrin, endrin ketone, β-endosulfan and endosulfan sulfate. Total concentrations of these OCPs ranged from 15.1 to 31.6 ng/L and averaged 19.9 ng/L. OCPs had higher concentrations at low water tide than at high water tide, and in bottom water than in surface water. In Biandansha and Meimaosha waters, lindane （T-HCH） of 9.0 ng/L and γ-chlordane of 8.8 ng/L were found, respectively. There was no significant difference between total OCPs concentrations in surface water from Biandansha and Qingcaosha, which are much lower than those in the downstream Meimaosha waters.     

Molecular Weight Distribution of Dissolved Organic Matter in Lake Hongfeng Determined by High Performance Size Exclusion Chromatography （HPSEC） With On-Line UV-Vis Absorbance and Fluorescence Detection

1IntroductionDissolvedorganicmatter (DOM)isamixtureoforganicsubstancesconsistingmainlyofhighmolecularweightpolymericcompounds (KenandLee,1 974) .Itplaysanimportantroleincarboncyclingandbiogeochemicalmobilizationoftracemetalsandorganiccompoundsintheaquaticenvi ronment (BeffleandLeppard ,1 995) .InrecentyearsmanyresearchershavepaidattentiontothesecomplexesbasedontheMWDofDOM ,sincethefateandtransportoftracechemicalsareinfluencedbyitsmolecularsize (Chiouetal.,1 986) .Themolecularweightorfrac…     

Mapping and geochemical characterization of the Toarcian organic matter in the Mediterranean Tethys and Middle East

Organic matter from Toarcian outcrops and boreholes in several basins around the Mediterranean Sea and Middle East has been studied. Rock-Eval pyrolysis, elemental analyses of kerogens and gas chromatography of chloroform extracts within these different basins have been used to determine the amount, petroleum potential and type of the organic matter. The results have been used to compile a mapping of the organic matter for the Toarcian stage, which shows heterogeneities in the distribution and type of organic matter:

1. (1) Marine organic matter (type II) occurs in different environments of deposition. Whereas high contents (>5% total organic carbon) correspond to thick deposits within the West European realm (Great Britain, North Sea, Paris Basin and Germany), the organic matter is less abundant in the Mediterranean area where lower concentrations (1–2% TOC), preserved in Lower Toarcian thin levels, are limited only to restricted basins (northern Italy, Greece).

2. (2) The predominance of continental organic matter (type III) along the northern margin of the Tethys corresponds to a deltaic environment.

3. (3) There is a predominance of altered organic matter within the carbonated platforms around the Mediterranean Tethys.

These results, supplemented with the data issuing from the literature, add a geochemical dimension to the paleogeography of the Tethys.     

Biomarker geochemistry of marine organic matter in the Hushan and Chaohu areas,Lower Yangtze region

Marine strata are widely exposed in the Hushan and Chaohu areas, Lower Yangtze region. As biomarker geochemistry of the strata has not been well documented, this paper deals with the biomarker composition of representative samples collected from the Silurian, Carboniferous and Triassic systems and their geological implications, thus providing clues to marine organic matter. On the basis of experimental results, it is shown that abundant biomarkers (e.g. n-alkanes, isoprenoids, terpanes and steranes) were detected. As organic matter in the strata is highly to over mature in general based on petrologic microobservation, some biomarkers (mainly n-alkanes) except terpanes and steranes cannot reflect the source, depositional environment and maturity of organic matter. Thus, primarily based on analyses of the terpanes and steranes, it is suggested that organic matter in the Silurian and Carboniferous strata is derived mainly from lower organisms, while higher plants are predominant in the Triassic organic matter. This further indicates that the depositional environment may have transformed from the marine to continental facies in the Late Triassic. These results provide new evidence for the study of regional depositional evolution, and have enriched the study of biological composition of organic matter. In addition, the biomarker geochemistry of organic matter at high to over maturation stage is addressed.     

Origin and transport of sedimentary organic matter in the Yalujiang estuary,North China

The biogeochemistry of organic matter (OM) in a macrotidal estuary, the Yalujiang River, was studied during two cruises: the flood season in August 1994 and the dry season in April 1996. Surface sediments were collected in the riverine zone (RZ), the turbidity maximum zone (TMZ), and the marine zone (MZ). The molecular distribution of the n-alkanes and fatty acid series and bulk sediment characteristics, such as C:N and δ¹³C, were used to assess differences in OM source and transport from the river upstream to the marine end member. Higher C:N values typical for terrestrial sources were observed at the upper reach for both seasons. The δ¹³C of OM in surface sediments varied from −27.3‰ to −21.6‰ in the flood season and from −26.8‰ to −31‰ in the dry season. The concentrations of n-alkanes varied between 0.3–21.4 μg g⁻¹ and the variation of fatty acids was 4.8–32.9 μg g⁻¹. The data showed mixing of terrestrial and autochthonous OM in the middle and lower reaches. The distribution of lipids (n-alkanes and Carbon Preference Index) encountered in this study confirmed the importance of terrestrial OM in the sediment samples from degraded soil material. The distribution of fatty acids suggested important phytoplankton, zooplankton, and microbial signals (short-chain and unsaturated acids; ≤C₂₀). Branched fatty acids, such as the iso- and anteiso-C₁₅ and C₁₇ compounds, relfect bacterial contributions. All samples were characterized by a high proportion of mixture inputs in both seasons. A slight decreasing trend was observed with increasing salinity except for the highest percentage of mixed fatty acids in the TMZ of the flood season. Terrestrial fatty acids were approximately 20% in the flood season and 27–46% in the dry season. Differences in hydrological conditions and primary production between the TMZ, RZ, and MZ resulted in different OM distributions, which are reflected in the sources and degree of diagenesis of the sedimentary OM. Seasonal variation may be strongly influenced by hydrological characteristics rather than primary productivity and anthropogenic activities in the Yalujiang region.