土壤溶解性有机质的研究进展

溶解性有机质(DOM)是土壤的重要组成部分,虽然含量占土壤有机质成分的比例不高,却是非常活跃的化学物质,可影响土壤的形成及肥力,通过水循环进入水生生态系统参与水体内的各个过程、经微生物作用进入大气圈对全球气候产生巨大影响,在土壤乃至全球系统中都发挥着极其重要的作用,已渐成为土壤学家、环境学家和生态学家研究的焦点。本文综述了众多学者的研究成果,讨论了土壤DOM的来源、含量、组成和分类,以及影响其含量变化的因素及其环境效应,指出了研究中存在的问题和未来发展趋势。     

铁氧化物矿物对苯酚和溶解性有机质表面吸附的初步研究

文中以铁氧化物矿物对苯酚和溶解性有机质(DOM)的吸附研究为例开展生态矿物学研究。铁氧化物矿物的吸附作用存在多种机制,这些吸附机制发生作用的条件主要取决于溶液化学性质和吸附质的理化性质。批处理实验研究表明,苯酚吸附在酸性微酸性条件下不强,吸附等温线符合Langmuir方程,属于表面分子吸附模型;DOM的吸附强并发生吸附分异,配体交换、憎水键和范氏力等多种模式并存,在酸性中性条件下对DOM在针铁矿上的吸附起着重要贡献。本文实验条件下DOM吸附等温线近于线性,不能采用Langmuir方程拟合,可能原因是DOM浓度较低。矿物表面荷电性对吸附影响显著,例如,当矿物表面净电荷为零(pH=pHpzc)时,矿物表面水化膜减薄甚至消失,苯酚分子、憎水DOM分子或片断都会倾向于在矿物表面上吸附。由于苯酚吸附机制单一,其受到的影响很明显,所以苯酚在pH值7～8范围内出现吸附最大值;由于配体交换作用主要发生在酸性微酸性条件下,所以在本文pH值约7.5的实验条件下,尽管配体交换仍在发生作用,但它不是主要吸附机制,针铁矿对DOM吸附的主要贡献应是憎水键和范氏力作用,此外,DOM吸附等温方程近于线性还可能与此有关。显然,铁矿物表面作用在对有机质含量低而铁矿物含量高的红壤中污染物和DOM的固定与归宿控制中扮演着重要的角色。     

溶解性有机质协同针铁矿光催化还原Cr(Ⅵ)的行为与机理研究

在上覆水体中,太阳光驱动下溶解性有机质与矿物之间的相互作用对污染物迁移转化行为的影响及其机制尚未引起足够的重视。本文以富里酸和针铁矿分别作为溶解性有机质和半导体矿物的代表,建立实验室光催化体系,系统探究了富里酸影响针铁矿光催化还原六价铬[Cr(Ⅵ)]的行为和机理。结果表明,与光照-针铁矿体系相比,光照-针铁矿-富里酸体系对Cr(Ⅵ)的去除率由19.8%提高至68.7%,故富里酸显著提高了针铁矿光催化还原Cr(Ⅵ)的能力,增强机制主要归结于富里酸提高了针铁矿产生光生电子的能力。此外,被还原的部分Cr(Ⅲ)与针铁矿表面羟基结合形成稳定的CrO(OH),并固定在针铁矿表面。这一成果可为半导体矿物在酸性矿山废水治理中的应用提供理论依据。     

湿地溶解性有机质（DOM）源识别方法研究

湿地是位于水陆生态系统之间的重要生态交错带,而溶解性有机质(DOM)是陆地向水生生态系统输送营养物质的重要载体物质。湿地中DOM的来源分为内源和外源。对湿地中DOM的来源进行识别有助于认识湿地中营养物质的生物化学循环特征,从而进一步了解水陆生态系统之间的物质循环。目前,对湿地DOM进行源识别的方法较多。根据各种方法在研究中应用的广泛性和可用性,本文主要介绍了光学法、同位素法、C/N比值法和生物标志法在湿地DOM源识别中的应用。综合分析表明,光学法、同位素法和C/N比值法在湿地DOM源识别研究中的应用较多。近几年,由于生物标志物(特别是木质素)不仅能够对来源进行识别,而且对源的变化很敏感,因此生物标志法在湿地DOM源识别中的应用成为研究的热点。论文在分析各种湿地DOM源识别方法的基础上,指出了目前研究中存在的问题,并提出进一步研究的方向。     

土壤溶解性有机质对植物吸收-输送-贮存重金属的影响研究现状与进展

土壤溶解性有机质对重金属生物地球化学循环中的生物可利用性起着重要作用。近年来,在土壤溶解性有机质对植物吸收、输送和贮存重金属过程的影响研究领域,国际上主要聚焦于以下三个探索方向: ①土壤溶解性有机质与重金属形成配位体,改变重金属在土壤中的迁移性和植物根际环境的作用机理研究; ②土壤溶解性有机质可突破植物细胞内重金属吸附点位的限制,通过控制植物细胞壁-重金属复合体的形态及重金属在细胞壁内外的吸收平衡,来干预重金属穿过细胞壁进入植物体的动力学过程研究;③土壤溶解性有机质-重金属的络合形态影响重金属在植物体内的输送和贮存作用过程与机理研究。本文基于研究溶解性有机质和重金属的植物过程中,水体溶解性有机质研究多而土壤溶解性有机质研究少的现状,针对溶解性有机质异质性的研究难点和溶解性有机质与植物亚细胞结构的配位特征的复杂性与局限性,从极性、官能团、配位结构等角度,分析并评述了土壤溶解性有机质和重金属生物地球化学中,植物吸收、输送和贮存重金属过程的研究现状和未来发展趋势。     

某盐湖卤水中硼存在状态的初步研究

硼酸盐在水溶液中存在状态的研究,前人已经傲过较详细的工作,并有专门论述。硼在盐湖卤水中存在状态的测定,尚未见文献记载。本文选用pH法测定了莱盐湖卤水和人工配制卤水中硼酸的酸度曲线和电离常数,从而得出了对该湖卤水中硼存在状态的初步看法。     

溶解性有机质对冻融作用下污染土壤中重金属Pb的溶出释放规律

采用室内模拟实验方法研究了溶解性有机质（DOM）对冻融作用下污染土壤中重金属Pb的溶出规律。结果表明：冻融作用明显改变了土壤基本理化性质和重金属Pb的化学形态;与未冻融土壤相比,DOM明显促进了冻融土壤中Pb的溶出释放。DOM对污染土壤中Pb的溶出释放作用与土壤类型、土壤污染时间和污染程度有关：DOM对棕壤中Pb的溶出释放作用大于对黑土中Pb的溶出释放作用;而且随着土壤Pb污染时间越长和污染程度越重,DOM对土壤中Pb的溶出释放作用越大。DOM对土壤中Pb的溶出释放还与DOM质量浓度、性质和组成密切相关：DOM质量浓度的增加提高了污染土壤中Pb的溶出释放;DOM的低pH和小分子量亲水性组分利于土壤中Pb的溶出释放。     

大柴旦盐湖卤水的现场扩大蒸发试验初探

为了研究硫酸铁亚型卤水在自然蒸发时的相化学,确定钾盐、硼酸、镁盐的结晶特性,把小型自然蒸发试验与现场扩大试验数据进行了比较。     

西台吉乃尔盐湖卤水动态变化研究

以柴达木盆地西台吉乃尔盐湖为研究区域,利用野外建立的长观网所获得的数据和水文示踪等科技手段,配合不同季节、不同时段（枯水期、丰水期等）的同位素示踪测试,分析地下卤水的动态变化规律,枯水期流速相对丰水期流速小,但是随着卤水的开采规模和开采条件不同以及自然气候、水文条件的改变,卤水的渗透流速呈现多变性。     

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.     

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。     

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。     

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.     

Origin and three-dimensional fluorescence spectrum of the chromophoric dissolved organic matter in Yangtze estuary, East China

Dissolved organic matter （DOM） is an important chemical component in natural water. Chromophoric dissolved organic matter （CDOM）, a fraction of optical properties, plays art important role in the biogeochemical cycle of nutrients in aquatic environment. People realized that DOM cycle is crucial in the global carbon and nitrogen flux, and also is inherently related to nutrients and trace metal elements. Therefore, CDOM was concerned by scientists in global oceanography and limnology fields. Water samples were collected from three sections （North Channel, South Channel and Zhuyuan） of the Yangtze （Changjiang River） estuary in March 2006 Three-dimensional excitation emission matrix （3-DEEM） fluorescence spectra were analyzed for those filtrates through Whatman GF/F filters. Dissolved organic carbon （DOC） was also measured by TOC analyzer. The tidal variety was also taken into account. The 3-D EEM fluorescence scans suggested the fluorescence characteristics of humic acid （Ex=332-344 nm, Em=439-451 nm） and fulvic acid （Ex=250-254 nm, Em=472-478 nm） were obvious, and the fluorescence group of protein-like and tyrosine （Ex=230 nm, Em=283 nm） was also found. They are mainly composed of CDOM in the Yangtze estuary. Further data analysis, especially the fluorescence index （f 450/500）, showed that terrestrial signal was rather strong （1.41-1.65） in the surface water, however, some terrestrial CDOM signals of bottom water showed excursions （1.28-1.39）. On the other hand, anthropogenic sign was impressed in the waters of Zhuyuan, which is one of the main drain outlets of Shanghai Metropolis. DOC concentrations ranged from 2.2 mg/L to 3.4 mg/L in Zhuyuan and South Channel, and from 2.0 mg/L to 2.4 mg/L in North Channel. The tide effect played a role in the composition of the CDOM measured by 3-D fluorescence scan technology.     

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。     

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.     

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。     

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...