洱海沉积物孔隙水中溶解有机质的三维荧光光谱特征

文章应用三维荧光光谱技术对洱海沉积物孔隙水中的溶解有机质进行了研究。结果表明,所有样品均含有4个明显的荧光峰,其中A和C为类腐殖酸荧光,B和D为类蛋白荧光。荧光强度在沉积物-水界面特别强,在1cm处急剧下降,之后随着沉积深度呈上升趋势。孔隙水溶解有机质均具有强的类蛋白荧光,揭示了溶解有机质中含有大量色氨酸、酪氨酸等芳环结构的类蛋白物质,并且在早期成岩过程中随着沉积深度呈积累趋势;类蛋白荧光与类腐殖酸荧光之间具有一定的相关关系,r(A,C)值在0.94-1.79之间,随着沉积深度逐渐下降,r(D,B)值在0.9-1.75之间,与r(A,C)值极为接近,且随着沉积深度有着类似的变化趋势,说明在洱海沉积物孔隙水中,r(D,B)与r(A,C)之间具有一定的相关性。     

近岸沉积物再悬浮期间所释放溶解有机物的荧光特征

对采自厦门湾九龙江人海河口的4个沉积物样品进行了室内再悬浮模拟实验,利用荧光激发-发射矩阵光谱(EEMs)研究了再悬浮过程中从沉积物中释放出的有色溶解有机物(CDOM)的荧光特征,同时通过与相应站位沉积物间隙水和底层水的对比分析,探讨了河口近岸海域的沉积物再悬浮作用作为水体中溶解有机物来源之一的可能性.结果表明,对给定站位,CDOM相对荧光强度和溶解有机碳(DOC)含量分布变化非常一致,均为间隙水最高,再悬浮次之,底层水最低;站位之间,底层水和再悬浮水样中CDOM相对荧光强度随盐度的降低而增加,从海端向河端增加的趋势明显.EEMs分析表明,各样品中均存在类腐殖质荧光与类蛋白质荧光团,且模拟实验也表明再悬浮作用可释放类腐殖质与类蛋白质荧光物质到底层水中,表明底质再悬浮将是近岸水体中CDOM的一个重要来源.与相应的底层水相比,间隙水的荧光峰(如峰A/C)的位置发生红移.再悬浮样品中EEMs的荧光团同时表现出相应底层水和间隙水的特征,但是荧光峰(峰A和峰C)的最大激发和发射波长更接近底层水中相应荧光团,与间隙水相比,则发生谱峰位置的蓝移.近海端样品中荧光峰M明显,随着盐度的降低,底层水和再悬浮水样的γ(M/C)值逐渐降低,且海源的峰M由海端向河端逐渐消失,表明峰M属于海洋自生来源.本研究区域DOM的荧光指数在1.61～1.93之间,表明近海端样品DOM主要为生物来源,而近河端样品DOM主要为陆源输入,或者为陆源与生物活动共同作用的结果.     

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。     

湿地沉积物-水界面营养盐交换的定量估算

为有效控制湖泊内源营养盐的释放,探讨了不同物理改良措施(覆沙、底质疏松)对沉积物-水界面营养盐的释放通量控制效果。利用原位孔隙水采样技术(Peeper)来获得沉积物孔隙水剖面,对改良后湿地沉积物孔隙水营养盐的垂向分布及其扩散通量进行了研究。结果发现,改良后沉积含水率、孔隙率分别提高了91%和54%。水土界面附近,随剖面深度增加,孔隙水中PO₄3-、NH₄+、NO₃-及NO₂-浓度分布符合指数关系,PO₄3-、NH₄+在8 cm左右达到最大值。种植芦苇后沉积物孔隙水中PO₄3-、NH₄+均有不同程度的下降,改良措施能有效降低表层弱结合态磷在总磷中比例但增加铁磷的比例,种植芦苇可强化这一效应。运用Fick第一定律对剖面孔隙水营养盐的扩散通量进行估算,发现沉积物经疏松后,NH₄+、PO₄3-的扩散通量由57.47~72.19μg/(m2·d)和2.55~3.21μg/(m2·d)变为-95.54~-130.94μg/(m2·d)和1.50~2.05μg/(m2·d),可考虑疏松沉积物-水界面附近沉积物来作为控制湖泊内源污染的有效手段之一。     

运用3DEEMs及荧光偏振方法研究pH、离子强度及浓度效应对腐殖酸荧光光谱特性的影响

利用三维荧光激发.发射光谱(3DEEMs)及荧光偏振法研究了3例腐殖酸和1例湖泊溶解有机物(DOM)在不同腐殖酸浓度、离子强度和pH条件下的荧光光谱特性.实验结果表明,随着浓度增大,各腐殖酸样的荧光强度增大,其中垃圾渗滤液腐殖酸和Pahokee泥炭腐殖酸的荧光峰出现红移.随着浓度进一步增大,腐殖酸的荧光偏振值增大,由此推断在此浓度范围内腐殖酸由于分子间的排斥作用使其构型出现伸展.离子强度增大导致腐殖酸及阿哈湖DOM的荧光强度降低.随着氯化钾(KCI)浓度增大,Fluka腐殖酸的荧光峰A蓝移,荧光峰B的荧光偏振值出现减小,推测是由于静电中和作用使其荧光基团发生卷曲造成的.离子强度对其余腐殖酸样和阿哈湖DOM的其他荧光特性没有明显的影响.总的来说,pH值的变化对腐殖酸和湖泊DOM的荧光特征的影响是很明显的.随着pH值增大,腐殖酸和湖泊DOM的荧光强度增强.而pH值减小时,Fluka腐殖酸和Pahokee泥炭腐殖酸的荧光峰(A峰)蓝移,当pH值降到5时,Fhka腐殖酸的荧光峰突然红移到最大,随后又继续蓝移;垃圾渗滤液腐殖酸和阿哈湖DOM的荧光峰位无明显的漂移.所有样品的荧光偏振值都减小(但阿哈湖DOM的A峰变化不大),但在pHi≤5时又增大,这种现象表明随着pH值降低,腐殖酸和湖泊DOM中有机大分子发生卷曲,但在pH≤5时由于羧基的质子化又以平面伸展构型出现在溶液中.     

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。      

沉积岩层中镁铝含量比的研究及其应用

镁铝含量比值定义为m=100×MgO/Al_2O_3。是根据沉积岩层中MgO含量的亲海性Al_2O_3含量的亲陆性特征而建立的比值关系。 m值有如下特征:在由淡水向海水过渡的沉积环境中,沉积岩层的m值随沉积环境中水体的盐度增加而增大;在理代沉积物中,m值与沉积区底层水的平均盐度成指数关系;碳酸盐含量高的沉积物中m值比同等盐度条件下碎屑沉积物中m值略高,但碳酸盐类沉积物的m值仍随着沉积区水体的盐度增加而增大。因此可以说,m值是沉积物形成环境中水体盐度和     

我国西北地区盐湖中的铀234U/238U比值示踪研究

内蒙古二连盆地、鄂尔多斯盆地典型含铀碳酸型盐湖水、岩两相234U/238U综合分析表明,碳酸型盐湖铀来源于大气降水和潜水对盐湖盆地周围中生代到现代富铀沉积物的溶滤、浸出,具有快速、近源物质来源特点。盐湖卤水和对应沉积物234U/238U值一般为0.8～1.2,湖卤水和潜卤水（晶间卤水）-岩两相中的铀处于沉积平衡状态。早白垩世～上新世含膏盐地层对比研究证实了富铀岩层234U/238U值随铀含量增大而减小,并趋近于1。室内盐湖水蒸发模拟实验发现残余卤水、沉积物234U/238U具有随蒸发程度增大逐渐减小的变化特征。盐湖现代沉积物物相研究发现铀主要以碳酸铀酰和吸附形式赋存在富含有机物和碎屑成分的含盐粘土沉积中,铀在盐类晶体中含量极少,仅存在于封闭水和结晶水中。卤水和沉积物ARu值是盐湖铀源及铀含量水平的指示标志之一。     

长江口沉积物-水界面砷的迁移转化机制与微生物调控分析

为探析长江口沉积物-水界面砷的迁移转化机制,本文分析了2019年夏季长江口4个站位上覆水和间隙水中总As浓度及形态的剖面变化特征,耦合氧化还原敏感元素(Fe、Mn和S)的剖面变化剖析了沉积物-水界面砷循环的Fe-Mn-S控制机制,同时结合砷相关功能基因探讨了沉积物-水界面砷迁移转化的微生物调控过程,估算了沉积物-水界面总As的扩散通量。结果表明,除A7-4站位外,长江口其他3个站位间隙水总As以As³⁺为主要存在形态,且总As浓度均在上覆水中为最低值(0.748~1.57 μg·L^-1),而在间隙水中随着深度增加而逐渐增加并在6~9 cm深度达到峰值(7.14~26.9 μg·L^-1)。间隙水总As及As³⁺浓度的剖面变化趋势与溶解态Fe²⁺、Mn²⁺相似,其均在中间层出现高值,说明沉积物Fe/Mn还原带砷的释放可能是随固相Fe(Ⅲ)或Mn(Ⅳ)的还原而转移到间隙水中的。氧化层和Fe/Mn还原带过渡区间隙水砷浓度与砷异化还原菌功能基因arrA和arsC丰度存在对应关系(除A1-3站外),说明砷异化还原菌将溶解As⁵⁺或固相As⁵⁺还原为溶解As³⁺可能是该过渡层砷迁移转化的另一重要过程。硫酸盐还原带的间隙水总As和As³⁺浓度降低,但由于间隙水的低S^2-浓度不利于砷硫化物生成,因此深层间隙水砷可能与铁硫矿物结合而被移除。底层环境氧化还原条件是影响沉积物-水界面砷迁移转化的重要因素,随底层水DO浓度的降低,砷迁移转化更倾向于微生物还原控制。长江口沉积物-水界面总As的扩散通量为1.18×10^-7~2.07×10^-7 μmol·cm^-2·s^-1,均表现为沉积物间隙水中总As向上覆水释放,即沉积物是研究区域水体总As的来源之一。     

我国西北地区盐湖中234U/238U比值与铀关系研究——以内蒙古地区碳酸盐型盐湖为例

内蒙古二连盆地、鄂尔多斯盆地典型含铀碳酸型盐湖水、岩两相2344U/23898U综合分析表明,该类盐湖铀来源于降水和潜水对盐湖盆地周围中生代以来富铀沉积物的溶滤、浸出,具有快速、近源物质来源特点.盐湖卤水和对应沉积物234 U/238U比值一般为0.8～1.2,盐湖卤水和潜卤水(晶间卤水)岩两相中的铀处于沉积平衡状态.含铀盐湖水、沉积物的234 U/238U比值随其铀含量增大而减小,并趋近于1,富铀盐湖水及沉积物234U/238U比值介于0.9～1.5之间.室内盐湖水蒸发模拟实验发现,残余卤水、沉积物234U/238U、铀总量具有随蒸发程度增大逐渐减小的变化特征.铀主要以碳酸铀酰络合物和吸附形式赋存在富含有机物和碎屑成分的含盐粘土沉积中.卤水和沉积物234 U/238U比值是盐湖铀源及铀含量水平的有效指示标志之一.     

Characterization of dissolved organic matter in anoxic rock extracts and in situ pore water of the Opalinus Clay

Dissolved organic matter (DOM) from the Opalinus Clay, a potential host rock for the disposal of radioactive waste, was isolated under strictly anoxic conditions from ground rock material and compared with DOM of in situ pore water samples. For the extractions, deionized water, synthetic pore water (SPW, water containing all major ions at pore water concentrations but no organic matter) and 0.1 M NaOH were used. The influence of the solid-to-liquid ratio, extraction time, acid-pretreatment and O₂ exposure of the rock material on the isolated DOM were investigated. Liquid chromatography coupled with a total organic C detector (LC-OCD) and reverse-phase ion chromatography were used to characterize the DOM size distributions and to determine the low molecular weight organic acid (LMWOA) contents in the pore water samples and the rock extracts.The results revealed that only a small portion of the total organic C of the rock material (<0.38%) was extractable, even after removal of carbonates by acid-pretreatment. The concentrations of dissolved organic C (DOC) were found to range from 3.9 ± 0.4 to 8.0 ± 0.8 mg/L in the anoxic extracts. The pore waters exhibited similar DOC concentrations ranging from 1.2 to 15.8 ± 0.5 mg/L. The analysis by LC-OCD showed that the DOM extracted under anoxic conditions and the pore water DOM mainly consisted of hydrophilic compounds of less than 500 Da. The DOM extracted with SPW was most similar in size to the pore water DOM. Grinding the rock under oxic conditions increased the DOC yields and shifted the size distribution toward higher molecular weight compounds compared to the strictly anoxic treatment. Acetate, lactate and formate were identified in all extracts and in the pore water. In total, LMWOA accounted for 36% of the total DOC in both pore water and SPW extracts. The results imply that controlled anoxic conditions and the use of SPW as an extractant are required to isolate DOM from Opalinus Clay rocks which most resembles the in situ pore water DOM with respect to its size distribution and the LMWOA contents.     

Molecular characterization of dissolved organic matter in pore water of continental shelf sediments

Dissolved organic matter (DOM) in sediment pore water is a complex molecular mixture reflecting various sources and biogeochemical processes. In order to constrain those sources and processes, molecular variations of pore water DOM in surface sediments from the NW Iberian shelf were analyzed by ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) and compared to river and marine water column DOM. Weighted average molecular element ratios of oxygen to carbon ((O/C)_wa) and hydrogen to carbon ((H/C)_wa) provided general information about DOM sources. DOM in local rivers was more oxygenated ((O/C)_wa 0.52) and contained less hydrogen ((H/C)_wa 1.15) than marine pore water DOM (mean (O/C)_wa 0.50, mean (H/C)_wa 1.26). The relative abundance of specific compound groups, such as highly oxygenated aromatic compounds or nitrogen-bearing compounds with low H/C ratios, correspond to a high concentration of lignin phenols (160 μg/g sediment dry weight) and a high TOC/TN ratio (13.3) in the sedimentary organic matter and were therefore assigned to terrestrial sources. The lower degree of unsaturation and a higher relative abundance of nitrogen-bearing compounds in the pore water DOM reflected microbial activity within the sediment. One sampling site on the shelf with a high sediment accumulation, and a humic-rich river sample showed a wide range of sulfur compounds in the DOM, accompanied by a higher abundance of lipid biomarkers for sulfate-reducing bacteria, probably indicating early diagenetic sulfurization of organic matter.     

波流作用下黄河三角洲硬壳层液化渗流形成机制研究

波流作用于海床产生动态孔隙水压力,如不能及时消除会在其内部产生累积孔隙水压力,相邻两点间的孔隙水压力差值造成的水力梯度产生渗流力,渗流力引起水流动,海床表面为排水界面,从而会在海床内部形成向上的渗流力作用于泥沙颗粒上,使泥沙发生启动向海床表层运移,从而形成一定范围的粗颗粒层。本文采用数值模拟对不同流速下的海床累积孔隙水压力进行了研究,同时分析了硬壳层的存在对海床累积孔隙水压力的影响规律,根据取得的不同流速下海床内部的累积孔隙水压力值,计算海床任意位置处的渗流压力梯度,采用王虎等(2014)推导建立的海床临界冲刷深度的计算方法,分析不同流速下的硬壳层形成深度。结果表明: 海流流向与波浪行进方向一致时,对累积孔隙水压力起促进作用,流速越大累积孔隙水压力越大,反之对累积孔隙水压力有抑制作用。表面硬壳层的存在会显著促进累积孔压的消散,累积孔隙水压力沿深度分布的极值均出现在下层原始海床中,流速U₀=0m ·s-1时硬壳层厚度由1m增加到3m,极值点深度下降了1.38m。累积孔隙水压力引起的渗流力对于海床泥沙启动影响显著,在流速U₀=0m ·s-1,U₀=1m ·s-1时泥沙启动深度均为海床1.5m深度处,并且海流流向与波浪行进方向一致时,会产生较大ΔP/ΔL值带动较粗的泥沙颗粒至海床表层,但对泥沙启动的最大深度影响不大。     

Effect of organic matter on DOM sorption on lake sediments

The effect of organic matter on the sorption of dissolved organic matter (DOM) on lake sediments is critical to understanding the fate and transport of contaminants at the sediment–water interface in lake ecosystems. Results indicate that DOM sorption on sediment is largely due to ligand exchange between the DOM and hydroxyl groups, and the amount of DOC sorbed is a linear function of added DOC. With increasing organic matter content the sediment has lower binding strength, higher releasing ability for DOM, and the higher amount of DOM sorbed by sediment naturally. There was no clear difference before and after the sediment was treated with H₂O₂, but the constant b implied that after the sediments were treated DOC release was promoted. Organic matter in the sediment tends to impede the sorption of DOC and results in a remarkable decrease in DOC sorption rates.     

Understanding the enhanced aqueous solubility of styrene by terrestrial dissolved organic matter using stable isotope mass balance and FTIR

We present a new stable isotope mass balance method for measuring the enhanced aqueous solubility of specific organic compounds in the presence of natural dissolved organic matter (DOM). It involves interfacing a standard dissolved organic carbon (DOC) analyzer with a stable isotope ratio monitoring system, is applicable to a wide range of model organic compounds and can be tuned to provide maximum precision for a given range of compound solubility and initial natural DOC concentration. Using ¹³C-labeled styrene as a model compound, we applied the method to investigate the reactivity of Dismal Swamp DOM as a function of season, nominal molecular size and chemical composition as determined using Fourier Transform Infrared Spectroscopy (FTIR). The solubility enhancement of styrene ranged from 23% to 118% relative to deionized water, while DOC-normalized enhancements varied from about 0.04 to 0.35 μM styrene/μM DOC as a function of season and nominal molecular weight. Statistical analysis of FTIR spectra reveals a strong positive correlation between the styrene concentration and the carboxyl content of the natural DOM. Reactivity differences between high molecular weight (HMW), low molecular weight (LMW) and total DOM samples are consistent with potential variations in their higher order structures.     

The behaviour of dissolved organic material,iron and manganese in estuarine mixing

Fractionation by ultra-filtration of the dissolved organic material (DOM) in the River Beaulieu, with typical concentrations of dissolved organic carbon (DOC) of 7–8 mg C/l, showed it to be mainly in the nominal molecular weight range of 10³–10⁵, with 16–23% of the total DOC in the fraction > 10⁵. The molecular weight distribution of DOM in the more alkaline River Test (average DOC, 2 mg C/l) was similar. In the River Beaulieu water, containing 136–314 βg Fe/l in ‘dissolved’ forms, 90% or more of this Fe was in the nominal molecular weight fraction > 10⁵. Experiments showed that DOM of nominal molecular weight <10⁵ could stabilize Fe(III) in ‘dissolved’ forms. The concentrations of ‘dissolved’ Fe in the river water probably reflect the presence of colloidal Fe stabilized by organic material and this process may influence the apparent molecular weight of the DOM. Dissolved. Mn (100–136 βg/l) in the River Beaulieu was mainly in true solution, probably as Mn(II), with some 30% in forms of molecular weight greater than ca 10⁴.During mi xing in the Beaulieu Estuary, DOC and dissolved Mn behave essentially conservatively. This contrasts with the removal of a large fraction of the dissolved Fe (Holliday and LISS, 1976, Est. Coastal Mar. Sci. 4, 349–353). Concentrations of lattice-held Fe and Mn in suspended particulate material were essentially uniform in the estuary, at 3.2 and 0.012%, respectively, whereas the non-lattice held fractions decreased markedly with increase in salinity. For Mn the decrease was linear and could be most simply accounted for by the physical mixing of riverborne and marine participates, although the possibility that some desorption occurs is not excluded. The non-linear decrease in the concentration of non-lattice held Fe in particulates reflected the more complex situation in which physical mixing is accompanied by removal of material from the ‘dissolved’ fraction.     

水化学揭示的弱透水层孔隙水演化特征及其古气候指示意义

地下水开采、弱透水层释水, 以及污染物迁移转化、高危废物深埋选址等水文地质和工程地质活动中, 弱透水层的作用越来越受到重视.了解弱透水层孔隙水的演化特征是认识弱透水层作用的首要问题.采用机械压榨法提取了曹妃甸地区某钻孔0~100 m粘性土孔隙水, 对孔隙水化学特征进行了分析.结果显示钻孔粘性土孔隙水呈碱性, 总溶解固体为7.26~26.89 g/L, 从浅到深逐渐减小; 陆相沉积层Cl/Br比趋向无穷大, 而海相沉积层仅为279~289.分析得出弱透水层孔隙水基本为岩层沉积水, 陆相和海相沉积层孔隙水分别显示出淡水和海水起源特征, 没有后期海水入侵影响迹象; Cl-、Na+变化趋势主要受蒸发浓缩作用影响, SO₄2-受硫酸盐的还原作用和石膏的溶解作用共同控制, Ca2+、Na+、K+还受到沉积过程中阳离子交换与吸附作用影响; 由δ18O重建晚更新世古气温为5.21~5.81 ℃, 浅部40 m以内计算的气温偏高是由于全新世气候变暖、孔隙水向下扩散迁移混合的影响.