Tracing groundwater flow and sources of organic carbon in sandstone aquifers using fluorescence properties of dissolved organic matter (DOM)

The fluorescence properties of groundwaters from sites in two UK aquifers, the Penrith Sandstone of Cumbria and the Sherwood Sandstone of South Yorkshire, were investigated using excitation–emission matrix (EEM) fluorescence spectroscopy. Both aquifers are regionally important sources of public supply water and are locally impacted by pollution. The Penrith Sandstone site is in a rural setting while the Sherwood Sandstone site is in suburban Doncaster. Fluorescence analysis of samples from discrete sample depths in the Penrith Sandstone shows decreasing fulvic-like intensities with depth and also shows a good correlation with CFC-12, an anthropogenic groundwater tracer. Tryptophan-like fluorescence centres in the depth profile may also provide evidence of rapid routing of relatively recent applications of organic slurry along fractures. Fluorescence analysis of groundwater sampled from multi-level piezometers installed within the Sherwood Sandstone aquifer also shows regions of tryptophan-like and relatively higher fulvic-like signatures. The fluorescence intensity profile in the piezometers shows tryptophan-like peaks at depths in excess of 50 m and mirrors the pattern exhibited by microbial species and CFCs highlighting the deep and rapid penetration of modern recharge due to rapid fracture flow. Fluorescence analysis has allowed the rapid assessment of different types and relative abundances of dissolved organic matter (DOM), and the fingerprinting of different sources of organic C within the groundwater system. The tryptophan:fulvic ratios found in the Penrith Sandstone were found to be between 0.5 and 3.0 and are characteristic of ratios from sheep waste sources. The Sherwood Sandstone has the lowest ratios (0.2–0.4) indicating a different source of DOM, most likely a mixture of terrestrial and microbial sources, although there is little evidence of pollution from leaking urban sewage systems. Results from these two studies suggest that intrinsic fluorescence may be used as a proxy for, or complementary tool to, other groundwater investigation methods in helping provide a conceptual model of groundwater flow and identifying different sources of DOM within the groundwater system.     

含水层中砷活化迁移的水化学与DOM三维荧光证据

为了认识高砷地下水中砷活化迁移的生物地球化学机制,对江汉平原地下水氧化还原敏感元素的水化学特征及溶解性有机物(DOM)三维荧光信息进行了研究.水化学研究显示,地下水中的砷与铁的还原和有机质的氧化分解过程有密切关系.水样DOM的三维荧光分析表明,地下水中存在微生物介导下氧化还原过程的反应性有机物组分,其中醌类腐殖质与铁、硫酸盐等的还原反应过程联系紧密.还原、氧化醌类及易降解DOM组分与还原产物、砷的关系进一步显示,砷的活化与微生物介导下的铁氧化物的还原过程联系在一起.在这一过程中,易降解有机物充当电子供体的角色并被消耗,而还原醌与氧化醌则很可能扮演了电子飞行过程中的电子飞行物,"催化"了砷活化的氧化还原过程.      

江汉平原高砷地下水中DOM三维荧光特征及其指示意义

水体中溶解性有机质(dissolved organic matter, DOM)是含水层中砷释放的主控因素之一.江汉平原河湖众多、沟渠广布,地表水体与浅层地下水的交互作用使得DOM的组分特征及其强度有显著差异.为查明江汉平原地下水中溶解性有机质在砷迁移转化过程中的作用,对江汉平原地表水和浅层地下水进行三维荧光光谱分析,使用平行因子分析法提取水体中有机质的分子组成、功能特点和荧光特征,并分析各组分相对含量与地下水中砷与铁的关联.江汉平原水体中DOM包括3种主要组分,组分C1、C2为类腐殖质,C2是生物降解过程中产生的小分子,C3为类蛋白物质.地下水DOM以类腐殖质组分C1、C2为主,地表水以类蛋白类物质C3和小分子腐殖质C2为主.高砷地下水中DOM以陆源为主,主要通过两种途径促进As的迁移转化:(1) DOM的腐殖质组分充当微生物群落的电子运输工具,促进微生物作用下的有机质氧化和铁氧化物的还原,并伴随As的释放及大量溶解性有机碳(dissolved organic carbon, DOC)和HCO₃-的产生;(2) As以铁等金属阳离子为桥接物与腐殖质结合,通过形成As-Fe-DOM络合物,导致地下水中砷的迁移.      

包气带土壤DOM三维荧光表征及对砷污染的指示意义

为了解包气带土壤DOM组成特征, 探索其对砷向地下水中迁移的影响, 对江汉平原高砷区土壤DOM进行了三维荧光光谱分析.结果表明DOM主要为类腐殖质成分, 芳香性官能团的减少导致荧光强度随包气带深度增加而变小, 局部深度荧光信号不规则变化指示非均质土壤剖面上DOM组分或主导官能团的变化.平行因子分析表明, DOM组分可更细致地分解为4种组分, 与微生物源的还原、氧化醌类和陆生的腐殖质富里酸类等相似.砷很可能在DOM腐殖质成分络合作用下与之随水体一起向下迁移, 砷的迁移也可能与微生物源的醌类作用过程有关.三维荧光光谱分析准确、快速地刻画了包气带土壤DOM的组分类别及空间变化特征, 初步揭示了DOM影响砷迁移的可能作用方式, 为进一步的地下水砷污染机制的研究提供了重要的参考信息.      

Variability in dissolved organic matter fluorescence and reduced sulfur concentration in coastal marine and estuarine environments

Fluorescence characterization of dissolved organic matter (DOM) and measurements of Cr-reducible sulfide (CRS) are presented for 72 coastal marine and estuarine water samples obtained from the USA and Canada. Each sample is identified according to source: terrigenous, autochthonous, wastewater or mixed. Fluorescence data are resolved into contributions from humic, fulvic, tyrosine and tryptophan-like fluorophores. Humic and fulvic-like fluorophores correlate well with dissolved organic C (DOC) (r² = 0.73 and 0.71, respectively) but tyrosine and tryptophan-like fluorophores show no correlation with DOC. Quality factors are identified by normalization of fluorescence contributions to DOC. Humic and fulvic components show no statistical differences between sources but the amino acid-like fluorescence quality factors show significant variations between source, with highest values for autochthonous sources (0.07 ± 0.01 arbitrary fluorescence units per mg of C) versus low values (0.015 ± 0.005) for terrigenous source waters. CRS concentrations are highly variable from 0.07 ± 0.01 to 7703 ± 98 nM and do no correlate with DOC except when terrigenous source waters (n = 13) are separated out from the total sample set (r² = 0.55). There is an open question in the literature; does DOC source matter in terms of protective effects towards metal toxicity? Here is shown that DOC molecular-level quality does vary and that this variation is mostly in terms of the contributions of amino acids to total fluorescence.     

Utilising seasonal variations in hydrogeochemistry and excitation-emission fluorescence to develop a conceptual groundwater flow model with implications for subsidence hazards: an example from Co. Durham, UK

Groundwaters were sampled from four research boreholes, a private supply well and a natural karst resurgence in southern County Durham, England. Time series data sets of piezometric levels, groundwater major ions, and fluorescence of dissolved organic matter (DOM) were interpreted in the light of new geological mapping to assess the movement of groundwater and its potential for the dissolution of gypsum. Three distinct groundwater facies were identified representing contact with gypsiferous strata, dolomitic limestone and Quaternary Till. Piezometric data indicated time varying transverse flow across the gypsifeorus strata, which was confirmed from gradational mixing of groundwater types and cation ratios. Fluorescence of dissolved DOM identified variations in protein and fulvic-like acid fluorescence. The former was taken to represent surface derived, short-lived material. Spatial and temporal variations in protein fluorescence offered a means to trace groundwater movement along the regional groundwater gradient and indicated rapid lateral movement of groundwater. It was concluded that gypsum dissolution is occurring beneath the town of Darlington, however, the presence of a thick deposit of Quaternary till effectively confines the small head differences of approximately 1 m, across the gypsum strata beneath the town. Further to the south, the lowering of the ground surface results in a greater upwards flow of water across the gypsum and is used to explain the presence of historic collapse sinkholes.     

Holocene estuarine sediments as a source of arsenic in Pleistocene groundwater in suburbs of Hanoi,Vietnam

Groundwater pollution by arsenic is a major health threat in suburban areas of Hanoi, Vietnam. The present study evaluates the effect of the sedimentary environments of the Pleistocene and Holocene deposits, and the recharge systems, on the groundwater arsenic pollution in Hanoi suburbs distant from the Red River. At two study sites (Linh Dam and Tai Mo communes), undisturbed soil cores identified a Pleistocene confined aquifer (PCA) and Holocene unconfined aquifer (HUA) as major aquifers, and Holocene estuarine and deltaic sediments as an aquitard layer between the two aquifers. The Holocene estuarine sediments (approximately 25–40 m depth, 9.6–4.8 cal ka BP) contained notably high concentrations of arsenic and organic matter, both likely to have been accumulated by mangroves during the Holocene sea-level highstand. The pore waters in these particular sediments exhibited elevated levels of arsenic and dissolved organic carbon. Arsenic in groundwater was higher in the PCA (25–94 μg/L) than in the HUA (5.2–42 μg/L), in both the monitoring wells and neighboring household tubewells. Elevated arsenic concentration in the PCA groundwater was likely due to vertical infiltration through the arsenic-rich and organic-matter-rich overlying Holocene estuarine sediments, caused by massive groundwater abstraction from the PCA. Countermeasures to prevent arsenic pollution of the PCA groundwater may include seeking alternative water resources, reducing water consumption, and/or appropriate choice of aquifers for groundwater supply.     

Spatial Variation in the Optical Properties of Dissolved Organic Matter (DOM) in Lakes on the Canadian Precambrian Shield and Links to Watershed Characteristics

In the present study, we explored the use of various optical parameters to detect differences in the composition of the dissolved organic matter (DOM) in a set of lakes that are all located on the Canadian Precambrian Shield, but within which Cu and Ni speciation predictions were previously shown to diverge from measured values in some lakes but not in others. Water samples were collected with in situ diffusion samplers in 2007 (N = 18 lakes) and 2008 (N = 8 lakes). Significant differences in DOM quality were identified between the sampling regions (Rouyn-Noranda, Québec and Sudbury, Ontario) and among lakes, based on dissolved organic carbon concentrations ([DOC]), specific UV absorbance (SUVA₂₅₄), fluorescence indices (FI), and excitation–emission matrix (EEM) fluorescence measurements. Parallel factor analysis (PARAFAC) of the EEM spectra revealed four components, two of which (C3, oxidized quinone fluorophore of allochthonous origin, and C4, tryptophan-like protein fluorescence of autochthonous origin) showed the greatest inter-regional variation. The inter-lake differences in DOM quality were consistent with the regional watershed characteristics as determined from satellite imagery (e.g., watershed-to-lake surface area ratios and relative percentages of surface water, rock outcrops vegetative cover and urban development). Source apportionment plots, built upon PARAFAC components ratios calculated for our lakes, were used to discriminate among DOM sources and to compare them to sources identified in the literature. These results have implications for other areas of research, such as quantifying lake-to-lake variations in the influence of organic matter on the speciation of trace elements in natural aquatic environments.     

Characterisation of rapid infiltration flows and vulnerability in a karst aquifer using a decomposed fluorescence signal of dissolved organic matter

The fluorescent properties of dissolved organic matter (DOM) have been used as natural tracers in various water systems. However, only few studies have focused on groundwater systems, specifically, on karst systems. The aim of this study was to develop the use of the DOM fluorescence signal as a natural tracer, considering the multiple compartments of a karst system. This method was applied to the Lez hydrosystem, which supplies the city of Montpellier with drinking water. The hydrodynamics and hydrochemistry of the spring were monitored beginning March 2006. The DOM fluorescence was measured by the excitation–emission matrix spectroscopy technique. The analysis of the total fluorescence signal confirms the efficiency of this tool to trace rapid infiltration flows. Moreover, the decomposition of the signal into different fluorophores complements the information provided by the total signal. Indeed, the fluorescence emitted by the humic compounds seems to be the ideal tool for identifying rapid infiltration flows. Nevertheless, the fluorescence of protein-like compounds is better correlated with the inflow of faecal bacteria at the outlet. This decomposition of the fluorescence signal is an interesting way to provide information on both the rapid infiltration flow as well as the vulnerability of the karst aquifers.     

江汉平原沙湖地区浅层含水层第四纪沉积环境演化

地下含水介质是地球关键带的重要研究对象,为了拓展江汉平原地下水环境问题研究维度,综合应用14C测年、δ13C、铁价态以及沉积物溶解态有机质(dissolved organic matter,DOM)的光谱信息等重要环境指标,对沙湖地区近30 ka的浅层含水层第四纪沉积环境演化特征进行了概化分析.沉积物中Zr/Rb、Rb/Sr比值以及δ13C值表明,剖面在5~7 m和16~18 m范围相对其他深度更显暖湿气候特征;Fe3+/Fe2+比值及沉积物颜色说明这两段暖湿期沉积物主要呈现还原环境.基于因子分析和DOM光谱信息可将沉积剖面的沉积环境演化概化为“近地表弱生物碎屑沉积单元”和“暖湿期强沉积单元”等5个单元.本沉积剖面所记录的沉积环境演化信息可为该区的地下水环境等相关问题的深入研究提供重要的背景支撑.      

贵德盆地三河流域高砷地下水中溶解性有机物三维荧光特性及其指示意义

溶解性有机物(dissolved organic matter, DOM)可以通过多种方式控制含水层中砷的迁移转化。贵德盆地承压含水层地下水砷含量显著高于潜水含水层。为查明承压水中溶解性有机物对砷浓度的影响,对研究区地表水、潜水以及承压水进行吸光度和三维荧光光谱的分析,利用平行因子分析法确定了水样中有机物成分及荧光特征。结果表明,贵德盆地水体中DOM包含陆源类腐殖质(C1)、受人为影响的腐殖质(C2)、类醌化合物(C3)和微生物来源的腐殖质(C4)4种组分。陆源类腐殖质C1可在地下水中富集,占总有机质的40%~55%。相比于地下水,C2和C3则在地表水中占据较高的比例。高砷承压水中C2、C3所占比例高于低砷潜水。其中,C1可以通过络合作用促进溶解性砷浓度的提高,C3作为电子穿梭体可以促进含砷铁氧化物或氢氧化物的还原性溶解从而释放砷。微生物降解有机质生成的HCO-3可以与砷竞争吸附,促进砷的解吸附。此外,还原性溶解产生的Fe(II)与HCO-3形成FeCO3固定一部分的砷。该研究表明,地下水中的天然有机物通过络合作用和作为电子穿梭体促进铁氧化物还原导致地下水砷的富集,为分析黄河上游地区高砷地下水的成因提供理论依据。     

Use of continuous measurements of dissolved organic matter fluorescence in groundwater to characterize fast infiltration through an unstable fractured hillslope (Valabres rockfall, French Alps)

Continuous measurements of natural fluorescence of dissolved organic matter (DOM) in groundwater have been used to characterize infiltration through an unstable fractured hillslope at the event time scale. Within the gneissic Valabres rockfall area in the southern French Alps, two sites, in the unstable massif and in the collapse area, were continuously monitored for electrical conductivity and for DOM natural fluorescence using a field fluorometer, and analyzed weekly for hydrochemical data. Two main results were found. From a methodological point of view, DOM natural fluorescence was a relevant tracer of fast infiltration in fissured media, knowing that continuous measurements improved the study of infiltration processes at the event time scale. From a hydrogeological point of view, the unstable fractured massif showed delayed dilution phenomena and the collapse areas showed fast and slow infiltration by piston-type flows via more or less open fractures. Consequently, from this conceptual model one may suppose that, unlike the collapse zones, the fractured hillslope threatening the valley is not submitted to strong pore-water pressure variations.     

Evidence for the enhanced lability of dissolved organic matter following permafrost slope disturbance in the Canadian High Arctic

Arctic landscapes are believed to be highly sensitive to climate change and accelerated disturbance of permafrost is expected to significantly impact the rate of carbon cycling. While half the global soil organic matter (SOM) is estimated to reside in Arctic soils, projected warmer temperatures and permafrost disturbance will release much of this SOM into waterways in the form of dissolved organic matter (DOM). The spring thaw and subsequent flushing of soils releases the highest contributions of DOM annually but has historically been undersampled due to the difficulties of sampling during this period. In this study, passive samplers were placed throughout paired High Arctic watersheds during the duration of the 2008 spring flush in Nunavut, Canada. The watersheds are very similar with the exception of widespread active layer detachments (ALDs) that occurred within one of the catchments during a period of elevated temperatures in the summer of 2007. DOM samples were analyzed for structural and spectral characteristics via nuclear magnetic resonance (NMR) and fluorescence spectroscopy as well as vulnerability to degradation with simulated solar exposure. Lignin-derived phenols were further assessed utilizing copper(II) oxide (CuO) oxidation and gas chromatography/mass spectrometry (GC/MS). The samples were found to have very low dissolved lignin phenol content (∼0.07% of DOC) and appear to originate from primarily non-woody angiosperm vegetation. The acid/aldehyde ratios for dissolved vanillyl phenols were found to be high (up to 3.6), indicating the presence of highly oxidized lignin. Differences between DOM released from the ALD vs. the undisturbed watershed suggest that these shallow detachment slides have significantly impacted the quality of Arctic DOM. Although material released from the disturbed catchment was found to be highly oxidized, DOM in the lake into which this catchment drained had chemical characteristics indicating high contributions from microbial and/or primary productivity. The resulting pool of dissolved carbon within the lake appears to be more biologically- and photochemically-labile than material from the undisturbed system. These disturbances may have implications for projected climate warming; sustained elevated temperatures would likely perpetuate widespread ALDs and further affect carbon cycling in this environment.     

沉积物不同提取态有机物特征及水文地球化学意义——以河套盆地典型研究区为例

地下水系统中有机物（OM）特征和活性对于地下水化学特征的形成和演化起着十分重要的作用。将内蒙古河套盆地表层湖相沉积物按10 cm间隔采集,并对沉积有机质的性质及来源进行重点分析。测量了不同深度上不同岩性沉积物的色度、水溶性有机物（WEOM）和盐溶性有机物（SEOM）含量及其光谱学特性。结果显示,沉积物的色度（R530-520）与TOC含量呈现相反的变化趋势:色度值较大时,TOC含量反而较小。相对于细砂层,黏土层的色度值较低,但TOC含量较高。相同的沉积物中,SEOM含量高于WEOM,但WEOM更易迁移至地下水中。有机物的光谱指数表明,WEOM以微生物来源为主,而SEOM以陆源为主。通过三维荧光光谱分析发现,荧光强度和沉积物有机碳（SOC）含量呈正相关;黏土层沉积有机物荧光强度更高;WEOM和SEOM均含类腐殖质成分和类蛋白成分,但SEOM中腐殖质成分较高;类腐殖质是所研究的沉积物中OM最主要的存在形式。     

Punctual and continuous estimation of transit time from dissolved organic matter fluorescence properties in karst aquifers,application to groundwaters of ‘Fontaine de Vaucluse’ experimental basin (SE France)

For about 10 years, environmental tracing development using dissolved organic matter (DOM) has been the subject of several studies. Particularly, the use of characterization techniques, like fluorescence emission–excitation matrices has enabled the identification of DOM sources and monitoring them within mainland or marine hydrosystems. Moreover, hydrogeologists have shown the significance of total organic carbon content used as a fast seepage tracer in karstic aquifers. The aim of this study consists in using DOM fluorescence signals to develop a transit time semi-quantitative tracer in heterogeneous hydrosystems. The Low-Noise Underground Laboratory (Vaucluse, France) cuts the network of Fontaine de Vaucluse (FV) karstic vadose zone randomly, and offers a special access to different unstructured dripwaters, with different hydrodynamic behaviour, inside its galleries, i.e. not hierarchical as in natural caves. Previous long-term hydrodynamic and hydrochemical studies allowed the understanding of their hydrogeological behaviour and the estimation of mean transit times. That is why this site is adequate to develop new transit time tracers. After identification of the different DOM sources (i.e. lithic and rendzic leptosols), fluorescence intensities monitoring from soil leachates and dripwaters, for certain excitation–emission wavelength pairs, allowed the development of punctual transit time tracing, by spotting infiltration periods of fluorescent compounds, and monitoring their transfer within a hydrosystem. A fluorescence index (humification index) and the mean transit time of each gallery groundwater, stemmed from previous hydrodynamic and hydrochemical studies, allowed the calibration of a logarithmic relationship. This one allows the development of a continuous transit time tracing method that estimates transit times without long-term studies. It has been tested on two springs of FV catchment basin, providing transit time estimations for karstic hydrosystems that do not present a mixture between recent and pluriannual waters.     

Comparative study of dissolved organic matter from groundwater and surface water in the Florida coastal Everglades using multi-dimensional spectrofluorometry combined with multivariate statistics

Dissolved organic matter (DOM) in groundwater and surface water samples from the Florida coastal Everglades were studied using excitation–emission matrix fluorescence modeled through parallel factor analysis (EEM-PARAFAC). DOM in both surface and groundwater from the eastern Everglades S332 basin reflected a terrestrial-derived fingerprint through dominantly higher abundances of humic-like PARAFAC components. In contrast, surface water DOM from northeastern Florida Bay featured a microbial-derived DOM signature based on the higher abundance of microbial humic-like and protein-like components consistent with its marine source. Surprisingly, groundwater DOM from northeastern Florida Bay reflected a terrestrial-derived source except for samples from central Florida Bay well, which mirrored a combination of terrestrial and marine end-member origin. Furthermore, surface water and groundwater displayed effects of different degradation pathways such as photodegradation and biodegradation as exemplified by two PARAFAC components seemingly indicative of such degradation processes. Finally, Principal Component Analysis of the EEM-PARAFAC data was able to distinguish and classify most of the samples according to DOM origins and degradation processes experienced, except for a small overlap of S332 surface water and groundwater, implying rather active surface-to-ground water interaction in some sites particularly during the rainy season. This study highlights that EEM-PARAFAC could be used successfully to trace and differentiate DOM from diverse sources across both horizontal and vertical flow profiles, and as such could be a convenient and useful tool for the better understanding of hydrological interactions and carbon biogeochemical cycling.     

Arsenic Levels in Groundwater from Quaternary Alluvium in the Ganga Plain and the Bengal Basin, Indian Subcontinent: Insights into Influence of Stratigraphy

Late Quaternary stratigraphy and sedimentation in the Ganga Alluvial Plain and the Bengal Basin have influenced arsenic contamination of groundwater. Arsenic contaminated aquifers are pervasive within lowland organic rich, clayey deltaic sediments in the Bengal Basin and locally within similar facies in narrow, entrenched river valleys within the Ganga Alluvial Plain. These were mainly deposited during early-mid Holocene sea level rise. Arsenic was transported from disseminated sources as adsorbed on dispersed phases of hydrated-iron-oxide. These were preferentially entrapped as sediment coatings on organic-rich, fine-grained deltaic and floodplain sediments. Arsenic was released later to groundwater mainly by reductive dissolution of hydrated-iron-oxide and corresponding oxidation of sediment organic matter. Strong reducing nature of groundwater in the Bengal Basin and parts of affected middle Ganga floodplains is indicated by high concentration of dissolved iron (maximum 9-35 mg/l). Groundwater being virtually stagnant under these settings, released arsenic accumulates and contaminates groundwater. The upland terraces in the Bengal Basin and in the Central Ganga Alluvial Plain, made up of the Pleistocene sediments are free of arsenic contamination in groundwater. These sediments are weakly oxidised in nature and associated groundwater is mildly reducing in general with low concentration of iron (<1 mg/l), and thus incapable to release arsenic. These sediments are also flushed free of arsenic, released if any, by groundwater flow due to high hydraulic head, because of their initial low-stand setting and later upland terraced position.     

长江中游沿岸地下水中有机质分子组成特征及其对碘富集的指示

长期摄入高碘地下水（碘浓度＞100 μg/L）会造成人体甲状腺机能损伤.天然有机质被认为是影响高碘地下水形成的关键组分,为研究地下水中溶解性有机质（DOM）分子组成对碘富集的影响,选取长江中游沿岸浅层地下水作为研究对象,运用傅立叶变换离子回旋共振质谱仪（FT-ICR-MS）表征不同碘浓度地下水中DOM分子组成差异.研究发现碘易富集在还原环境的浅层地下水中,地下水中碘的浓度与溶解性有机碳（DOC）浓度无显著关系,DOM分子总数越多碘浓度越高;高碘地下水较低碘水DOM分子均一性、多样性更强,氧化程度和不饱和程度更高,含更多芳香性结构.长江中游沿岸高碘地下水的形成受DOM分子组成控制,主要与不饱和程度高尤其是含芳香性结构的大分子DOM有关,含芳香性结构的DOM分子与碘络合在高碘地下水的形成过程中起重要作用.      

高砷地下水研究的热点及发展趋势

全球范围内广泛分布的高砷地下水给人们的健康造成了极大的威胁.高砷地下水的形成机理是一项世界性的科学问题.介绍了高砷地下水的分布特点、富集机理,阐明了溶解性有机物、地下水流动特征对高砷地下水形成的影响机制.现今的研究揭示了有机物和微生物协同作用下高砷地下水的形成过程,并且在高砷地下水的空间分布、时间变化特征以及人类活动对高砷地下水形成的影响等方面取得了一些创新性成果.这3方面的研究也逐渐成为近些年高砷地下水研究的热点.这些研究不仅丰富了砷迁移转化的理论成果,而且有助于开辟低砷水源,保障水资源的可持续利用,具有重要的理论和现实意义.     

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。