Quantifying the phenolic content of freshwaters using simple assays with different underlying reaction mechanisms

Five different assays, Gibbs, Prussian Blue, Folin-Ciocalteau, fluorescence quenching of added phenol and precipitation of phenolics with bovine serum albumin (BSA) were investigated for their suitability in measuring the phenolic content of freshwaters. Phenol and a hydrolysable tannic acid were used as standards for monophenolics and polyphenolics, respectively. The individual and simultaneous application of both standards in doubly distilled water and filtered freshwater samples showed no matrix interference for the Gibbs, the Prussian Blue and the Folin-Ciocalteau assays. The quenching of phenol fluorescence and incomplete precipitation of added tannic acid in the freshwater samples were thought to originate from complexation. The Gibbs assay was specific for monophenolics, monohydroxybenzenes, with a Criterion of Detection (CoD) of 0.027 mg l(-1). Evaluating the assay using twenty-two monophenolics of lignin origin showed, apart from phenol itself, the phenolic acids vanillic, isovanillic, ferulic and syringic to have a linear response between 0 and 10 microM. The other monophenolics were not responsive in the Gibbs assay. The oxidation-based assays Prussian Blue and Folin-Ciocalteau had a CoD of 0.169 and 0.025 mg l(-1), respectively. The ratio of response of both assays for each sample was taken as an indication of the degree of polymerisation of the phenolic content. The Folin-Ciocalteau assay was used directly on the samples, on samples spiked with tannic acid at 2 and 4 mg l(-1), and after precipitation of phenolics with BSA. The difference in tannic acid equivalents before and after treatment, assayed the amount of protein precipitated phenolics. The results of all assays allowed differentiation between monophenolics (Gibbs), polyphenolics (Prussian Blue), total phenolics (Folin-Ciocalteau), complexation of added phenol and protein-precipitated phenolics. The reaction mechanisms underlying the assays were matched onto those occurring during humification. The assays were applied to six filtered freshwater samples and two humic and two fulvic acids. The results showed a different pattern for each site and illustrated varying reactivity of the 'phenolic content' of freshwater.     

Disinfection by-product formation and mutagenic assay caused by preozonation of groundwater containing bromide

Brominated organic and inorganic by-products are generated during ozonation of groundwater containing high bromide concentrations. This study measured concentrations of bromate, bromoform, bromoacetic acids, bromoacetonitriles, bromoacetone, 2,4-dibromophenol and aldehyde generated by ozonation. The potential mutagenicity of ozonated waters was assessed using the Ames and Microtox tests. Test results for the 18 ozonated groundwater samples demonstrate that bromate formation is associated with high pH, bromide and alkalinity content, low levels of dissolved organic carbon (DOC) and ammonia, and low alkalinity. Brominated organic by-products were correlated with high bromide ion and natural organic matter content, and low ammonia concentrations. The Ames test results demonstrate that all extracts from ozonated water have mutagenic activity; however, the 18 raw groundwater samples had no mutagenicity. The Microtox test results also show that the ozonated water samples were highly toxic. Generally, both bromide and DOC content promoted the formation of ozonation by-products and mutagenicity. Controlling of bromide and DOC concentrations is an effective method of reducing potential by-product formation and eliminating mutagenicity problems associated with groundwater ozonation.     

七虎林河流域上游溶解性有机质光谱特性分析

七虎林河源头区地表腐殖质随着径流的冲刷进入水体,形成了天然有机质(NOM),其中,溶解性有机质(DOM)易对河流水质造成影响。为了研究七虎林河中DOM的时空分布特征及其对水质的影响,开展了6次采样,分析了水体及土壤吸收光谱和荧光光谱特征参数,利用平行因子(PARAFAC)算法解析了水体DOM的特性及来源。结果表明：七虎林河上游水体五日生化需氧量(BOD₅)、高锰酸盐指数(COD_Mn)、化学需氧量(COD)、可溶性有机碳(DOC)的浓度分别为1.4 mg/L±0.2 mg/L、6.1 mg/L±3.0 mg/L、21 mg/L±8 mg/L、7.0 mg/L±3.2 mg/L,BOD₅/COD平均值为0.08,说明流域内水体DOM的可生化性差,对水质影响较小。光谱特征参数紫外吸收系数(SUVA₂₅₄)、荧光指数(FI)、腐殖化指数(HIX)、生物源指数(BIX)分析结果表明,七虎林河上游云山水库库上林区河段DOM的物质组成与水库及库下河段差异显著。库上河段DOM的芳香碳含量更高、分子量更大、自生源组分...     

The role of forest type in the variability of DOC in atmospheric deposition at forest plots in Italy

Dissolved organic carbon (DOC) was studied in atmospheric deposition samples collected on a weekly basis in 2005-2009 at 10 forest plots in Italy. The plots covered a wide range of geographical attributes and were representative of the main forest types in Italy. Both spatial and temporal variations in DOC concentrations and fluxes are discussed, with the aim of identifying the main factors affecting DOC variability. DOC concentration increased from bulk to throughfall and stemflow water samples at all sites, as an effect of leaching from leaves and branches, going from 0.7-1.7 mg C L(-1) in bulk samples to 1.8-15.8 mg C L(-1) in throughfall and 4.2-10.7 mg C L(-1) in stemflow, with striking differences among the various plots. Low concentrations were found in runoff (0.5-2.0 mg C L(-1)), showing that the export of DOC via running waters was limited. The seasonality of DOC in throughfall samples was evident, with the highest concentration in summer when biological activity is at a maximum, and minima in winter due to limited DOC production and leaching. Statistical analysis revealed that DOC had a close relationship with organic and total nitrogen, and with nutrient ions, and a negative correlation with precipitation amount. Forest type proved to be a major factor affecting DOC variability: concentration and, to a lesser extent, fluxes were lower in stands dominated by deciduous species. The character of evergreens, and the size and shape of their leaves and needles, which regulate the interception mechanism of dry deposition, are mainly responsible for this.     

Adsorption and detection of some phenolic compounds by rice husk ash of Kenyan origin

Rice husk ash (RHA) obtained from a rice mill in Kenya has been used as an inexpensive and effective adsorbent (and reagent) for the removal (and detection) of some phenolic compounds in water. The abundantly available rice mill waste was used in dual laboratory-scale batch experiments to evaluate its potential in: (i) the removal of phenol, 1,3-dihydroxybenzene (resorcinol) and 2-chlorophenol from water; and (ii) the detection of 1,2-dihydroxybenzene (pyrocatechol) and 1,2,3-trihydroxybenzene (pyrogallol) present in an aqueous medium. The studies were conducted using synthetic water with different initial concentrations of the phenolic compounds. The effects of different operating conditions (such as contact time, concentration of the phenolic compounds, adsorbent quantity, temperature, and pH) were assessed by evaluating the phenolic compound removal efficiency as well as the extent of their color formation reactions (where applicable). RHA exhibits reasonable adsorption capacity for the phenolic compounds and follows both Langmuir and Freundlich isotherm models. Adsorption capacities of 1.53 x 10(-4), 8.07 x 10(-5), and 1.63 x 10(-6) mol g(-1) were determined for phenol, resorcinol and 2-chlorophenol, respectively. Nearly 100% adsorption of the phenolic compounds was possible and this depended on the weight of RHA employed. For the detection experiments, pyrocatechol and pyrogallol present in water formed coloured complexes with RHA, with the rate of colour formation increasing with temperature, weight of RHA, concentration of the phenolic compounds and sonication. This study has proven that RHA is a useful agricultural waste product for the removal and detection of some phenolic compounds.     

Chemistry of Dissolved Organic Carbon at Bear Brook Watershed, Maine: Stream Water Response to (NH4)2SO4 Additions

This study was conducted to determine the response of stream water DOC and organic acidity to increased inputs of ammonium sulfate to a whole catchment. Precipitation, throughfall, soil solutions (from Spodosols) and stream waters were characterized for DOC concentrations and fractions (hydrophobic acids and neutrals, hydrophilic acids, bases, and neutrals) in both the control (East Bear) and the treatment (West Bear) catchments of Bear Brook Watershed, Maine (BBWM), a northern hardwood forest. In all solutions except precipitation, DOC was composed primarily of organic acids, with hydrophobic acids dominating (> 60% of DOC) in forest floor leachates (5000 mol C L-1), and a balance of hydrophobic and hydrophilic acids in deep B horizons and stream waters ( 150 mol C L-1). Stream waters had higher concentrations of DOC during storm or snowmelt events (high discharge), often reaching 300 to 400 mol C L-1. Forest floor leachate C was rapidly attenuated by the mineral soils under all flow conditions, indicating how important mineral soil sorption of DOC was in reducing the loss of C via surface water from BBWM. No differences occurred between control and treatment streams for concentration or composition of DOC due to treatment from 1989 through 1994. In 1995, West Bear Brook had much lower concentrations of DOC than East Bear for the first time. However, this occurred during a year of record low runoff, suggesting that hydrology may have affected export of C. Average annual export of DOC from the catchments was similar (1000 to 2000 mol C ha-1 yr-1). Organic anions in streamwaters increased slightly during high flow events (e.g., East Bear had means of 15 and 19 eq L-1 organic anions during base flow and high discharge in 1995). Treatment of West Bear caused a decrease in organic anions, both in concentration and contribution to overall anion composition (organic anions during high discharge as a percentage of total anions decreased from about 8 to 4% for 1987-89 and 1993-95 samples, respectively). This was probably due to decreased solution pH (greater protonation of organics) and higher concentrations of inorganic anions. Overall, there were no clear, detectable changes in stream water DOC, with only minor changes in organic anions, as a result of treatment with ammonium sulfate.     

Study of the effect of pH, salinity and DOC on fluorescence of synthetic mixtures of freshwater and marine salts

In order to provide support for the discussion of the fate of organic matter in estuaries, a laboratory simulation was performed by changing freshwater ionic strength, pH and organic matter content. The change in spectroscopic characteristics caused by variations in salinity, pH and organic matter concentration in the filtered samples was observed by UV-Vis and fluorescence spectroscopy. The increase in emission fluorescence intensity of dissolved organic matter (DOM) due to increasing salinity (in the range 0 to 5 g l-1) is affected by the pH of the samples. The emission fluorescence intensity at the three maxima observed in the fluorescence spectra, is linearly correlated with dissolved organic carbon (DOC) concentration at several salinity values in the same sample. The increase in organic matter concentration caused a shift in the emission peak wavelength at 410 nm for several salinity values. We concluded that it is necessary to take into account the influence of salinity and pH on emission fluorescence of dissolved organic matter if it is to be used as a tracer in estuarine or near shore areas.     

Characterization of dissolved organic carbon at low levels in environmental waters by microfluidic-chip-based capillary gel electrophoresis with a laser-induced fluorescence detector

A microfluidic analytical system for characterization of dissolved organic carbon (DOC) in environmental waters, based on a capillary gel electrophoresis (CGE) device with a laser-induced fluorescence (LEF) detector, was developed. The applied voltage and the running buffer were investigated to control the simple floating injection and CGE separation for convenient cross-type microchips made from polymethylmethacylate. We obtained reproducible peaks for standard organic solutions and the determination time is less than 70 s. The values of the relative standard deviation (RSD) were 0.17–2.01% for repetitive injection (n?=?12). We demonstrated high-throughput characterization of DOC in environmental water from the Biwa Lake and the Hino River using microfluidic chip and determined that the content of DOC in the Biwa Lake changed with the seasons.     

CDOM fluorescence as a proxy of DOC concentration in natural waters: a comparison of four contrasting tropical systems

Chromophoric dissolved organic matter (CDOM) fluorescence or absorption is often proposed as a rapid alternative to chemical methods for the estimation of bulk dissolved organic carbon (DOC) concentration in natural waters. However, the robustness of this method across a wide range of systems remains to be shown. We measured CDOM fluorescence and DOC concentration in four tropical freshwater and coastal environments (estuary and coastal, tropical shallow lakes, water from the freshwater lens of two small islands, and soil leachates). We found that although this method can provide an estimation of DOC concentration in sites with low variability in DOC and CDOM sources in systems where the variability of DOC and CDOM sources are high, this method should not be used as it will lead to errors in the estimation of the bulk DOC concentration.     

A brief overview of modern directions in marine DOC studies part I.--Methodological aspects

The necessity for determining the role of dissolved organic carbon (DOC) in the global carbon cycle stimulated the development of different methods of DOC analysis in aquatic environments. Progress in this direction has been made by oceanographers who developed and introduced a high-temperature catalytic oxidation (HTC) method for low organic carbon concentrations. Today this method is the reference method for marine DOC study. The combination of available reference materials and the participation in intercalibration exercises has resulted in both an increased accuracy and higher precision for this method. The HTC method completely oxidizes the more resistant DOC; makes information rapidly available following the completion of the field analysis; provides a high precision (down to 0.5 microM C); covers the range of seawater DOC concentrations (35-80 microM C and higher); with certain modifications it has proved to be both seaworthy and amenable to automated analysis; and the reliable and relatively easy to operate HTC analyzer is commercially available and easily combined with a total nitrogen analyzer for simultaneous measurements of both parameters in the same sample. In this review we summarize some aspects of sample collection, handling and the analytical chemistry of the DOC analysis by the HTC technique in marine study.     

Mercury proxies and mercury dynamics in a forested watershed of the US Northeast

Although many studies focus on mercury (Hg) and methylmercury (MeHg) dynamics in streams, challenges remain in identifying the relative importance of land cover and seasonality at regulating Hg and MeHg dynamics at the watershed scale. Developing robust proxies for Hg and/or MeHg determination also remains a challenge. Our study used Hg, MeHg, and dissolved organic carbon (DOC) concentration measurements and various DOC fluorescence indices to characterize Hg and DOC dynamics in a forested watershed of the US Northeast. Principal component analysis indicated that land cover/landscape position (i.e., headwater vs. wetland-influenced area vs. lake-influenced area) explained 44 % of the variance in Hg, MeHg, DOC concentrations, and DOC quality during the snow-free season, while seasonality (i.e., air temperature and discharge) explained only 21 % of the variance in the results. Furthermore, finding a good proxy for Hg that is valid across a range of landscape positions remains a challenge; however, regression analysis indicated that the fluorescence peak Humic C (excitation?=?350 nm; emission?=?max (420–480)), which corresponds to the presence of melanoidins in water, explained 21 % of the variability in MeHg concentrations across both space and time (p?=?0.001), and thus appears to be a possible proxy for MeHg determination in our study watershed. From a management perspective, land cover modifications (lake, reservoir, and wetland) are likely to play more important roles at regulating Hg, MeHg, and DOC exports at the watershed scale than long-term changes in the climate of this region.     

Landscape Controls on Mercury in Streamwater at Acadia National Park, USA

Fall and spring streamwater samples were analyzed for total mercury (Hg) and major ions from 47 locations on Mount Desert Island in Maine. Samples were collected in zones that were burned in a major wildfire in 1947 and in zones that were not burned. We hypothesized that Hg concentrations in streamwater would be higher from unburned sites than burned watersheds, because fire would volatilize stored Hg. The Hg concentrations, based on burn history, were not statistically distinct. However, significant statistical associations were noted between Hg and the amount of wetlands in the drainage systems and with streamwater dissolved organic carbon (DOC). An unexpected result was that wetlands mobilized more Hg by generating more DOC in total, but upland DOC was more efficient at transporting Hg because it transports more Hg per unit DOC. Mercury concentrations were higher in samples collected at lower elevations. Mercury was positively correlated with relative discharge, although this effect was not distinguished from the DOC association. In this research, sample site elevation and the presence of upstream wetlands and their associated DOC affected Hg concentrations more strongly than burn history.     

Long-term changes in acidity and DOC in throughfall and soil water in Finnish forests

The main objective of this study was to examine if any detectable trends in dissolved organic carbon (DOC), sulphate (SO₄-S) concentrations and acid neutralizing capacity (ANC) in throughfall (TF) and soil water (SW) could be found during 1990–2010 and to relate them to recent changes in decreased acid deposition. The study was conducted in seven boreal coniferous forest sites: four of which are managed and three unmanaged forests sites. Generally, temporal trend showed a significant decrease in SO₄-S concentrations in bulk precipitation (BP), TF and SW. At some of the sites, there was an increasing tendency in BP and TF in the DOC concentrations. This feature coincides with decreasing SO₄-S concentration, indicating that SO₄-S may be an important driver of DOC release from the canopy. However, a slightly increased temperature, larger senescing needle mass and consequently increased decaying activity in the canopy may partly explain the increasing trend in DOC. In SW, no consistent DOC trend was seen. At some sites, the decreased base cation concentrations mostly account for the decrease in the ANC values in SW and TF.     

The feasibility of monitoring wilderness lake chemistry with remote sensing methods

Wilderness lakes in the U.S. are at risk to the effects of atmospheric pollution. The results of the EPA Western Lake Survey, for example, show that many of the lakes in the West have very low concentrations of dissolved constituents, and are sensitive to acidification. Lakes located in wilderness areas were found to be particularly sensitive: median ANC values of 91.4 eq/1 compared to 282.7 eq/1 in non-wilderness areas. Sampling remote wilderness lakes is difficult and expensive. For example, the cost of sampling each lake in the National surface water survey was about $ 4000 per lake. Remote sensing methods may provide an alternative means of monitoring the chemistry of wilderness lakes. This study defines the feasibility of the remote monitoring of lake chemistry in the Adirondack Park region of New York by comparing measured lake chemistry with field reflectance measurements, remote reflectance measurements from aircraft and satellite and laboratory and airborne laser fluorosensor data.Water samples collected from a representative population of Adirondack Park lakes were analyzed for pH, acid neutralizing capacity (ANC), dissolved organic carbon (DOC), total reactive aluminum and plant pigment concentration concurrent with the collection of remote sensing data. Lake parameters estimated from field reflectance measurements which directly effect lake optical properties, total pigments, DOC, and turbidity were estimated with less error and more precision than those parameters not directly related to lake optics, pH, ANC and A1 concentration. Results from airborne MSS and Landsat MSS data produced lower R² values than estimates using field reflectance.The concentration of DOC can be estimated remotely by using laser fluorosensing. The spectral-fluorescence properties of DOC were correlated with the pH and aluminum concentrations in the lake water. Remotely measurable DOC fluorescence spectra were used to estimate DOC, H, and A1 concentrations.Of the methods investigated, laser fluorosensing shows the most promise for the remote prediction of lake DOC, hydrogen ion and aluminum concentration in Adirondack lakes while reflectance measures may be used to estimate lake chlorophyll, DOC and transparency. Given the large number of wilderness lakes and the difficulty of sampling in remote wilderness, remote sensing methods may provide an alternative, while less precise, method of monitoring lake chemistry. The applicability of these findings to lakes in other wilderness areas is unknown. Similar studies of the feasibility of monitoring Western wilderness lake chemistry with remote sensing methods are being initiated.Supported by an A. W. Mellon Foundation Grant to Dr. G. E. Likens while a student in the Section of Ecology and Systematics, Cornell University, Ithaca, NY and a Fellow of the Institute for Ecosystem Studies, New York Botanical Garden, Mary Flagler Cary Arboretum, Millbrook, NY.Contribution from Fourth World Wilderness Congress-Acid Rain Symposium, Denver (Estes Park), Colorado, September 11–18, 1987.     

Assessment of priority phenolic compounds in sediments from an extremely polluted coastal wetland (Lake Maryut, Egypt)

Although high concentrations of trace organic pollutants were recorded along the Egyptian Mediterranean Coast and its corresponding coastal wetlands, no published data are available for the levels of phenolic compounds. Thus, this work aimed to investigate the levels of phenolic compounds in sediments of a heavily polluted coastal wetland (Lake Maryut, Egypt). For that purpose, a method was optimized for the extraction and detection of chlorophenols, methylphenols, and nitrophenols in sediments using GC-MS. Sediments were extracted with 0.1 M NaOH/methanol by sonication. Cleanup of sediment extracts using liquid–liquid extraction and SPE was found important to remove most of the interfering co-extracts. The proposed analytical methodology was validated by analysis of matrix spikes. Detection limits were 0.063–0.694 μg/kg dw for sediments. Good recoveries (70–110%) and precision values (RSD?<?20%) were obtained from the fortification experiments at the parts per billion level in sediments. The method was applied to investigate the level of contamination with phenols in 19 sediment samples from Lake Maryut. Results revealed that higher concentrations were observed in the main basin (MB) of Lake Maryut affected by the discharge of effluents from a primary wastewater treatment plant, direct discharge of industrial effluents, domestic wastes, and agricultural effluents from Qalaa Drain (QD). Chlorophenols (CPs) were the major group detected in the lake sediments followed by methylphenols (MPs) and nitrophenols (NPs). CPs were dominated by 2-, 4-, and 3-chlorophenols. Concentrations of CPs were higher at the north and northwestern parts of the MB indicating the influence of industrial effluents discharged into the lake. On the other hand, higher concentrations of NPs were observed at the south and southwestern parts of the MB, which is subjected to the discharge of agricultural and domestic effluents via QD. Results of the risk assessment revealed that phenol, cresols, 2,4-dinitrophenol, 4-NP, 2-CP, 2,3,4,6-tetrachlorophenol and 2,4-dimethylphenol are contaminants of concern and that adverse ecological effects could possibly occur to benthic species from the exposure to these pollutants in Lake Maryut and thus phenols should be included in monitoring and pollution prevention programs in the Egyptian aquatic environment affected by anthropogenic activities.     

Assessment of PAH pollution in the southern Baltic Sea through the analysis of sediment, mussels and fish bile

The concentrations of fifteen PAH compounds in samples of sediment and blue mussel tissue (Mytilus trossulus) were measured. In addition, the biliary polycyclic aromatic hydrocarbon metabolites present in flounder (Platichthys flesus) were analysed. Two methods were used in the analysis of PAH metabolites; high performance liquid chromatography (HPLC) and fixed wavelength fluorescence (FF). The major PAH metabolite which could be measured using the HPLC method was 1-OH pyrene. It was possible to detect 1-OH Phe and 3-OH B[a]P in 70 and 24 samples respectively, of the 87 samples analysed. However, the concentrations of 1-OH Phe and 3-OH B[a]P were below or near to the LOQ (0.002 μg ml(-1) bile). The bile of flounder samples from the Gulf of Gdańsk had 1-OH Pyr concentrations which ranged from 0.019 to 0.066 μg ml(-1) bile. The high linear correlation observed between the quantity of 1-OH pyrene determined by the HPLC-F method and the content of the sum of pyrene-type PAHs obtained by the FF method indicated the FF method of determination of pyrene-type PAH metabolites can be used as a screening method. The content of ∑(15)PAHs in sediments collected in the Gulf of Gdansk, in 2008, ranged from 29.3 to 103 μg kg(-1) dw. In mussel tissue ∑(15)PAHs concentrations were between 173.2 μg kg(-1) dw and 237.7 μg kg(-1) dw. All concentrations measured in the current study, in mussel tissue, were below the OSPAR toxicity threshold values.     

Phthalate and alkyl phenol concentrations in soil following applications of inorganic fertiliser or sewage sludge to pasture and potential rates of ingestion by grazing ruminants

Soil concentrations of dioctyl phthalate (DOP) and the alkyl phenols, octyl phenol (OP) and nonyl phenol (NP), after repeated surface applications of sewage sludge to pastures, were investigated. Liquid sludge was applied at a rate of 2.25 tonnes dry matter (DM) per hectare to each of three treated (T) plots on three occasions during the summer and two occasions in the early spring over a period of 2.5 years. Control (C) plots were treated with inorganic fertiliser containing amounts of nitrogen equivalent to those applied to the treated plots. At between 69 and 81 days after the application of sludge, 15 separate soil samples were collected from one half of each of the plots (Experiment 1). Concentrations (microg g(-1)) of DOP were higher (P < 0.001) than those of NP, while those of OP were generally below detectable levels. Mean soil concentrations of DOP were not significantly different in T and C plots [0.233 vs. 0.155 microg g(-1); standard error of the difference (SED) = 0.046; not significant (NS)], partly because there was already a relatively large amount of DOP present. NP concentrations were, however, significantly higher in T than in C plots (0.021 vs. 0.013 microg g(-1) SED = 0.002; P < 0.05). There was no consistent change over time in the mean soil concentrations of these compounds when sampled at intervals of 3-6 months. Concentrations in soil samples collected at monthly intervals following sludge application indicated that the variation in concentrations of these endocrine-disrupting compounds (EDC) was unrelated to time since sludge application. Rates of soil ingestion, expressed as the percentage of DM intake represented by soil, were higher during the winter than the summer (5.40 vs. 1.17; SED = 0.360; P < 0.001) and estimated daily intakes of DOP and NP were up to 150 microg and 8 microg, respectively. It is concluded that the application of sewage sludge to pasture does not increase soil concentrations of phthalate (as DOP) or alkyl phenols. Thus, the risk of increased exposure to these EDC as a result of sludge application is small. However, the small effect of sludge application on soil concentrations may be largely a reflection of the relatively high concentrations of DOP already present in the soil, which may be biologically significant.     

溶解性有机碳对微库仑法测定水中可吸附有机卤素的影响

微库仑法测水样中可吸附有机卤素(AOX)受多种因素影响,其中溶解性有机碳(DOC)的影响非常显著。DOC对微库仑法2种前处理方法(双柱法和振荡法)的影响差异很大。双柱法受DOC影响较小,当DOC浓度小于1 000 mg/L时,AOX加标回收率范围为94.0%~104%。振荡法受DOC影响较明显,随着DOC浓度的升高,AOX回收率持续下降,当DOC浓度达到1 000 mg/L时,AOX加标回收率下降至72.1%,但DOC浓度小于100 mg/L时,AOX加标回收满足方法要求。进一步研究发现,DOC对振荡法的影响主要由于竞争吸附降低了活性炭对AOX的吸附容量,而非吸附速率,虽然增大活性炭用量可在一定程度上减小DOC对AOX测定的影响,但对样品进行稀释是减少DOC影响的最简单高效的办法。同时,DOC对不同类型的有机卤代物影响不同,有机溴受DOC影响程度小于有机氯。     

Excitation–emission matrices applied to the study of urban effluent discharges in the Chubut River (Patagonia, Argentina)

Natural and contaminated waters of the final reaches of the Chubut River (Patagonia, Argentina) were studied to obtain information about river organic matter and effects of domestic and industrial discharges (fishery effluents and sewages). Fluorescence Excitation–Emission Matrices (EEMs) were obtained from samples only filtered (0.45 μm) and diluted, if necessary, to avoid the inner filter effect. In addition, physicochemical parameters were measured to know the quality of the water and the effluents. Results show that EEMs allow a rapid and simple control of the effluents from fisheries and domestic sewage in Chubut River estuary, necessary to take management decisions.     

Does road salting induce or ameliorate DOC mobilisation from roadside soils to surface waters in the long term?

Soils down slope of roads have been affected over decades by road salting in the UK uplands. Salt additions to fresh soil facilitate dispersal of organic matter so there is a potential risk of release of DON and DOC to nearby rivers where these run parallel to roads. Over time, however, salting enhances soil pH of naturally acid soils, and thus organic matter degradation through to CO2, thereby, lowering soil organic matter content. In addition any relatively labile organic matter may have already been dispersed. Thus, it is hypothesised that enhanced DOC mobilisation should only be a potential problem if soils not previously exposed to salt become heavily exposed in the future. This paper combines data from field observations and laboratory simulations to elucidate mechanisms controlling organic matter mobilisation processes to determine what controls spatial and temporal trends in DOC concentrations in soil solutions down slope of roads. Organic matter solubilisation is dependent on the degree of road salt exposure soils have had. The laboratory experiment provided evidence that there are two competing effects upon which solubilisation is dependent (a) pH suppression and (b) sodium dispersion. Other organic matter solubility models, if correct, link quite well with the authors "when it's gone, it's gone" hypothesis.