Interactions between viruses and goethite during saturated flow: effects of solution pH, carbonate, and phosphate

Metal oxides have great potential for controlling the fate and transport of viruses in the subsurface and water-treatment systems. The processes, however, are subject to solution chemistry. In this study, a number of column experiments were conducted to examine the effects of solution pH and anions (carbonate and phosphate) on attachment, transport, and inactivation of two bacteriophages (phiX174 and MS-2) in goethite-coated sand medium. Removal of both viruses on goethite-coated sand increased as solution pH decreased from 9.3 to 7.5, due mostly to virus inactivation. MS-2, a relatively hydrophobic virus with a lower isoelectric point (3.9), was more sensitive to the change of solution pH than phiX174, a relatively hydrophilic virus with a higher isoelectric point (6.6), in terms of their attachment and inactivation on goethite. About 90% of the MS-2 particles removed by goethite (accounting for 81% of the total input) were inactivated at pH 7.5, whereas all of the removed MS-2 particles (accounting for 10% of the total input) still remained infectious at pH 9.3. In comparison, approximately 74% of the goethite-bound phiX174 particles (accounting for 95% of the total input) lost their infectivity at pH 7.5, in contrast to a complete recovery at pH 9.3 (accounting for 65% of the total input) when the columns were eluted using a beef extract solution (pH 9.5). Presence of phosphate (20 mM H(2)PO(4)(-)) in input solution reduced virus attachment and appeared to protect the viruses from being inactivated during transport; this effect was more significant on MS-2 than on phiX174. Specifically, approximately 29% of the phiX174 particles and approximately 49% of MS-2 particles injected into the column were removed during transport. Mass recovery data showed that no phiX174 was inactivated in the presence of phosphate, whereas about 38% of the MS-2 particles attached on goethite lost their infectivity. Conversely, presence of carbonate on goethite increased virus attachment and inactivation due to contribution of additional attachment sites from protonated surface groups of the carbonate ions that were adsorbed on goethite. About 70% of the total input viruses (both phiX174 and MS-2) were removed during transport, of which 35% phiX174 and 85% MS-2 were eventually inactivated.     

Virus retention and transport through Al-oxide coated sand columns: effects of ionic strength and composition

Knowledge of the factors that influence the fate and transport of viruses in porous media is very important for accurately determining groundwater vulnerability and for developing protective regulations. In this study, six saturated sand column experiments were performed to examine the effects of a positively charged Al-oxide, which was coated on sand particles, on the retention and transport of viruses (phiX174 and MS-2) in background solutions of different ionic strength and composition. We found that the Al-oxide coating on sand significantly removed viruses during their transport in a phosphate buffered saline (PBS) solution. Mass balance calculations showed that 34% of the input MS-2 was inactivated/irreversibly sorbed on the surface of Al-oxide coated sand whereas 100% of phiX174 was recovered. Results from this study also indicated that higher ionic strength facilitated the transport of both phiX174 and MS-2 through the Al-oxide coated sand. This was attributed to the effect of ion shielding, which at higher ionic strength decreased the electrostatic attraction between the viral particles and the sand surface and consequently decreased virus sorption. Strong effect of the ionic strength indicates that an outer-sphere complexation mechanism was responsible for the virus sorption on the Al-oxide coated sand. Ion composition of the background solutions was also found to be a significant factor in influencing virus retention and transport. Virus transport was enhanced in the presence of phosphate (HPO(4)(2-)) as compared to bicarbonate (HCO(3)(-)), and the effect of HPO(4)(2-) was more significant on MS-2 than on phiX174. The presence of bivalent cations (Ca(2+) and Mg(2+)) increased virus transport because the cations partially screened the negative charges on the viruses therefore decreased the electrostatic attraction between the positively charged sand surface and the negatively charged viruses. Mass recovery data indicated that bivalent cations gave rise to a certain degree of inactivation/irreversibly sorption of phiX174 on the surface of Al-oxide coated sand. On the contrary, the bivalent cations appeared to have protected MS-2 from inactivation/irreversibly sorption. This study provides some insights into the mechanisms responsible for virus retention and transport in porous media.     

Two-site kinetic modeling of bacteriophages transport through columns of saturated dune sand

Breakthrough curves, on a semi-log scale, from tests in porous media with block-input of viruses, bacteria, protozoa and colloidal particles often exhibit a typical skewness: a rather slowly rising limb and a smooth transition of a declining limb to a very long tail. One-site kinetic models fail to fit the rising and declining limbs together with the tail satisfactorily. Inclusion of an equilibrium adsorption site does not seem to improve simulation results. This was encountered in the simulation of breakthrough curves from a recent field study on the removal of bacteriophages MS2 and PRD1 by passage through dune sand. In the present study, results of laboratory experiments for the study of this issue are presented. Breakthrough curves of salt and bacteriophages MS2, PRDI, and phiX174 in 1 D column experiments have been measured. One- and two-site kinetic models have been applied to fit and predict breakthrough curves from column experiments. The two-site model fitted all breakthrough curves very satisfactorily, accounting for the skewness of the rising limb as well as for the smooth transition of the declining limb to the tail of the breakthrough curve. The one-site model does not follow the curvature of the breakthrough tail, leading to an overestimation of the inactivation rate coefficient for attached viruses. Interaction with kinetic site 1 is characterized by relatively fast attachment and slow detachment, whereas attachment to and detachment from kinetic site 2 is fast. Inactivation of viruses and interaction with kinetic site 2 provide only a minor contribution to removal. Virus removal is mainly determined by the attachment to site 1. Bacteriophage phiX174 attached more than MS2 and PRD1, which can be explained by the greater electrostatic repulsion that MS2 and PRD1 experience compared to the less negatively charged phiX174.     

Effects of organic acids on adsorption of lead onto montmorillonite,goethite and humic acid

Adsorption isotherms for Pb onto six soil components (quartz, feldspar, kaolinite, montmorillonite, goethite and humic acid) were studied. The influence of pH, EDTA and citric acid on the adsorption of Pb onto montmorillonite, goethite and humic acid were considered. Results indicate that the experimental data fit the Langmuir Adsorption Isotherm. The adsorption capacity for Pb at pH 6 was found to be in the order: humic acid (22.7 mg g(-1)) > goethite (11.04 mg g(-1)) > montmorillonite (10.4 mg g(-1)) > kaolinite (0.91 mg g(-1)) > feldspar (0.503 mg g(-1)) > quartz (0.148 mg g(-1)). Generally, the amount of Pb adsorbed onto montmorillonite, goethite and humic acid decreased with increasing concentrations of EDTA and citric acid and with increases in alkality. However, there were two exceptions: (1) addition of citric acid increased the amount of Pb adsorbed onto humic acid; and (2) the amount of Pb adsorbed onto goethite decreased with increasing pH in the presence of EDTA. Some mechanisms involved in the adsorption reactions are discussed.     

Virus transport in physically and geochemically heterogeneous subsurface porous media

A two-dimensional model for virus transport in physically and geochemically heterogeneous subsurface porous media is presented. The model involves solution of the advection-dispersion equation, which additionally considers virus inactivation in the solution, as well as virus removal at the solid matrix surface due to attachment (deposition), release, and inactivation. Two surface inactivation models for the fate of attached inactive viruses and their subsequent role on virus attachment and release were considered. Geochemical heterogeneity, portrayed as patches of positively charged metal oxyhydroxide coatings on collector grain surfaces, and physical heterogeneity, portrayed as spatial variability of hydraulic conductivity, were incorporated in the model. Both layered and randomly (log-normally) distributed physical and geochemical heterogeneities were considered. The upstream weighted multiple cell balance method was employed to numerically solve the governing equations of groundwater flow and virus transport. Model predictions show that the presence of subsurface layered geochemical and physical heterogeneity results in preferential flow paths and thus significantly affect virus mobility. Random distributions of physical and geochemical heterogeneity have also notable influence on the virus transport behavior. While the solution inactivation rate was found to significantly influence the virus transport behavior, surface inactivation under realistic field conditions has probably a negligible influence on the overall virus transport. It was further demonstrated that large virus release rates result in extended periods of virus breakthrough over significant distances downstream from the injection sites. This behavior suggests that simpler models that account for virus adsorption through a retardation factor may yield a misleading assessment of virus transport in "hydrogeologically sensitive" subsurface environments.     

Column experiments to study nonlinear removal of bacteriophages by passage through saturated dune sand

In a recent field study on dune recharge, bacteriophages MS2 and PRD1 were found to be removed 3 log10 over the first 2.4 m and only 5 log10 over the next 27 m. To understand the causes of this nonlinear removal, column experiments were carried out under conditions similar to the field: same recharge water, temperature (5 +/- 3 degrees C) and pore water velocity (1.5 m day(-1)). Soil samples were taken along a streamline between the recharge canal and the first monitoring well. Bacteriophage phiX174 was included for comparison. The high initial removal in the field was found not to be due to heterogeneity of phage suspensions but to soil heterogeneity. Phage removal rates correlated strongly positively with soil organic carbon content, and relatively strongly positively with silt content and the presence of ferric oxyhydroxides. Soil organic carbon content, silt content and the presence of ferric oxyhydroxides were found to decrease exponentially with travel distance. Removal rates of phiX174 were found to be 3-10 times higher than those of MS2 and PRD1 due to the lower electrostatic repulsion that the less negatively charged phiX174 experiences. It is suggested that the high initial removal in the field is due to the presence of favorable sites for attachment formed by ferric oxyhydroxides that decrease exponentially with travel distance. Similar removal rates may be found at both laboratory and field scale. However, due to local variations at field scale detailed knowledge on soil heterogeneity may be needed to enable a reliable prediction of removal.     

Dissolved organic matter effects on the performance of a barrier to polycyclic aromatic hydrocarbon transport by groundwater

In order to contain the movement of organic contaminants in groundwater, a subsurface sorption barrier consisting of sand or clay minerals coated with a cationic surfactant has been proposed. The effectiveness of such a sorption barrier might be affected by the presence of dissolved organic matter (DOM) in the groundwater. To study the impact of DOM on barrier performance, a series of batch experiments were performed by measuring naphthalene and phenanthrene sorption onto sand coated with cetylpyridinium chloride (CPC) and bentonite coated with hexadecyltrimethylammonium bromide (HDTMA) in the presence of various concentrations of DOM. The overall soil-water distribution coefficient (K*) of naphthalene and phenanthrene onto CPC-coated sand decreased with increasing DOM concentration, whereas the K* of the compounds onto HDTMA-coated bentonite slightly increased with increasing DOM concentration. To describe the overall distribution of polycyclic aromatic hydrocarbons (PAHs) in the systems, a competitive multiphase sorption (CMS) model was developed and compared with an overall mechanistic sorption (OMS) model. The modeling studies showed that while the OMS model did not explain the CPC-coated sand experimental results, a model that included competitive sorption between DOM and PAH did. The experimental results and the modeling study indicated that there was no apparent competition between DOM and PAH in the HDTMA-coated bentonite system, and indicated that in groundwater systems with high DOM, a barrier using HDTMA-coated bentonite might be more effective.     

Transport of coliphage PRD1 in a surface flow constructed wetland.

A tracer study was conducted in a 3-ha surface flow constructed wetland to analyze transport performance of PRD1, an enteric virus model. The convection-dispersion equation (CDE), including a first-order reaction model, adequately simulated transport performance of PRD1 in the wetland under an average hydraulic loading rate of 82 mm/d. Convective velocity (v) and longitudinal dispersion coefficient (D) were estimated by modeling a conservative tracer (bromide) pulse through the wetland. Both PRD1 and bromide were simultaneously added to the entering secondary treated wastewater effluent. The mass of bromide and PRD1 recovered was 76 and 16%, respectively. The PRD1 decay rate was calculated to be 0.3/day. The findings of this study suggest that the CDE model and analytical moment equations represent a suitable option to characterize virus transport performance in surface flow constructed wetlands.     

Mobility of Cd and Cu in formulated sediments coated with iron hydroxides and/or humic acids: a DGT and DGT-PROFS modeling approach

The diffusive gradients technique in thin films (DGT) was used to investigate the kinetic resupply of Cd and Cu to pore water from the solid phase. For the sake of simplification, experiments were performed using formulated sediments that differed in the presence or absence of humic acids (HA) and/or of iron hydroxides (i.e., goethite and ferrihydrite). The effects of the time after the contamination of the solid phase (aging effect) on formulated sediments that were coated with goethite and HA and spiked with Cd were also evaluated. Kinetic DGT results were interpreted using the newly developed, multi-compartmental model DGT-PROFS.Due to Cu humate formation, the addition of HA slightly increased the Cu concentration in the pore water independent of the effect of the iron hydroxide coating on the formulated sediments and slightly decreased that of Cd. The impact of 8-190 d of aging resulted in a significant decrease in the Cd concentration of the pore water over an increasing incubation time.Modeling our results with DGT-PROFS led to the following conclusions concerning the impact of HA and iron hydroxides on Cd and Cu availability. First, in the presence of HA and absence of iron hydroxides, Cd is associated mainly with weak sites, while Cu is bound to strong sites. Similarly, in the presence of both iron hydroxides and HA, Cu appeared to be more heavily associated with the strong sites than did Cd. When the incubation time increased from 8 to 190 d, a proportion of Cd initially adsorbed onto weak sites transferred to the strong sites, suggesting that the adsorption of Cd on sediments is controlled partially by slow kinetic processes.     

Pilot scale thermal treatment of pig slurry for the inactivation of animal virus pathogens

This paper describes a pilot scale treatment plant that has been designed and built for the thermal inactivation in pig slurry of two viruses that infect pigs--African swine fever virus (ASFV) and swine vesicular disease virus (SVDV). The plant treats pig slurry continuously at a rate of up to 100 litres/hour and functions by heating the slurry, maintaining at least 99.99% of the slurry at the required temperature for a minimum period of 5 minutes, and then recovering the heat to raise the temperature of the incoming slurry. Results obtained indicated that SVDV was inactivated in pig slurry to below detectable levels with an alkaline pH (pH 7.5 to 8, as is usually the case) at a temperature of between 50 and 55 degrees C. In acidified slurry (pH 6.4), inactivation occurred between 55 and 60 degrees C. The difference in inactivation temperatures was probably due to the presence of free ammonia in the unacidified slurry. ASFV was inactivated by operating the plant at a temperature of 53 degrees C at a pH of 8.     

Microbiological reduction of chromium(VI) in presence of pyrolusite-coated sand by Shewanella alga Simidu ATCC 55627 in laboratory column experiments

Hexavalent chromium (Cr(VI)) was reduced to non-toxic trivalent chromium (Cr(III)) by a dissimilatory metal reducing bacteria, Shewanella alga Simidu (BrY-MT) ATCC 55627. A series of dynamic column experiments were conducted to provide an understanding of Cr(VI) reduction by the facultative anaerobe BrY-MT in the presence of pyrolusite (beta-MnO(2)) coated sand and uncoated-quartz sand. All dynamic column experiments were conducted under growth conditions using Cr(VI) as the terminal electron acceptor and lactate as the electron donor and energy source. Reduction of Cr(VI) was rapid (within 8 h) in columns packed with uncoated quartz sand and BrY-MT, whereas Cr(VI) reduction by BrY-MT was delayed (57 h) in the presence of beta-MnO(2)-coated sand. The role of beta-MnO(2) in this study was to provide oxidation of trivalent chromium (Cr(III)). BrY-MT attachment was higher on beta-MnO(2)-coated sand than on uncoated quartz sand at 10, 60, and 85.5 h. Results have shown that this particular strain of Shewanella did not appreciably reduce Mn(IV) to Mn(II) species nor biosorbed Cr and Mn during its metabolic activities.     

Mineralogy, morphology, and textural relationships in coatings on quartz grains in sediments in a quartz-sand aquifer

Mineralogical studies of coatings on quartz grains and bulk sediments from an aquifer on Western Cape Cod, Massachusetts, USA were carried out using a variety of transmission electron microscopy (TEM) techniques. Previous studies demonstrated that coatings on quartz grains control the adsorption properties of these sediments. Samples for TEM characterization were made by a gentle mechanical grinding method and focused ion beam (FIB) milling. The former method can make abundant electron-transparent coating assemblages for comprehensive and quantitative X-ray analysis and the latter technique protects the coating texture from being destroyed. Characterization of the samples from both a pristine area and an area heavily impacted by wastewater discharge shows similar coating textures and chemical compositions. Major constituents of the coating include Al-substituted goethite and illite/chlorite clays. Goethite is aggregated into well-crystallized domains through oriented attachment resulting in increased porosity. Illite/chlorite clays with various chemical compositions were observed to be mixed with goethite aggregates and aligned sub-parallel to the associated quartz surface. The uniform spatial distribution of wastewater-derived phosphorus throughout the coating from the wastewater-contaminated site suggests that all of the coating constituents, including those adjacent to the quartz surface, are accessible to groundwater solutes. Both TEM characterization and chemical extraction results indicate there is a significantly greater amount of amorphous iron oxide in samples from wastewater discharge area compared to those from the pristine region, which might reflect the impact of redox cycling of iron under the wastewater-discharge area. Coating compositions are consistent with the moderate metal and oxy-metalloid adsorption capacities, low but significant cation exchange capacities, and control of iron(III) solubility by goethite observed in reactive transport experimental and modeling studies conducted at the site.     

Contributions of humic substances to the dissolved organic carbon pool in wetlands from different climates

Wetlands are an important source of DOM. However, the quantity and quality of wetlands' DOM from various climatic regions have not been studied comprehensively. The relationship between the concentrations of DOM (DOC), humic substances (HS) and non-humic substances (NHS) in wetland associated sloughs, streams and rivers, in cool temperate (Hokkaido, Japan), sub-tropical (Florida, USA), and tropical (Sarawak, Malaysia) regions was investigated. The DOC ranged from 1.0 to 15.6 mg CL(-1) in Hokkaido, 6.0-24.4 mg CL(-1) in Florida, and 18.9-75.3 mg CL(-1) in Sarawak, respectively. The relationship between DOC and HS concentrations for the whole sample set was regressed to a primary function with y-intercept of zero (P<0.005) and a slope value of 0.841. A similar correlation was observed between DOC and NHS concentrations, with a smaller slope value of 0.159. However, the correlation coefficient of the latter was much larger when the data was regressed to a logarithmic curve. These observations suggest the presence of a general tendency that the increased DOC in the river waters was mainly due to the increased supply of HS from wetland soils, whereas the rate of the increase in the NHS supply has an upper limit which may be controlled by primary productivity.     

Accelerated photo-transformation of 2,2′,4,4′,5,5′-hexachlorobiphenyl (PCB 153) in water by dissolved organic matter

The ubiquitous dissolved organic matter (DOM) has an important influence on transformation of organic contaminants through the production of reactive substances, such as ^?OH, ¹O₂, and ³DOM*. The photolysis of a higher chlorinated polychlorinated biphenyl (PCB) congener (2,2′,4,4′,5,5′-hexachlorobiphenyl, PCB 153) under simulated sunlight in presence of humic acid (HA) was investigated. Degradation of PCB 153 was accelerated significantly by the addition of HA, with a rate constant of 0.0214, 0.0413, and 0.0358 h^?1 in the initial 18 h of irradiation in presence of 1, 5, and 20 mg/L HA, respectively. The main photodegradation products analyzed by gas chromatography mass spectrometry were 4-hydroxy-2,2′,4′,5,5′-pentaCB and 2,4,5-trichlorobenzoic acid. Main reactive species involved were determined by the electron spin-resonance spectroscopy, including ¹O₂ and ^?OH. Special scavengers were added to elucidate the photolysis mechanisms. By using the specific scavengers, it turned out that ^?OH accounted for 29.3 % of the degradation, and the intra-DOM reactive species (¹O₂, ^?OH, and ³DOM*) accounted for 59.6 % of the degradation. Photo-transformation sensitized by DOM, which involves both aqueous and intra-DOM reactions of PCBs with reactive species, may be one of the most important mechanisms for natural attenuation of PCBs.     

The effect of humic acid on uptake/adsorption of copper by a marine bacterium and two marine ciliates

The effect of humic acid (HA) on Cu uptake by a bacterium and two bacterivorus ciliates was investigated. The presence of HA resulted in a statistically significant (p<0.001) decrease in Cu associated with bacteria that were exposed to 67 microg Cu L(-1). Complexation of Cu appears to lower the availability of Cu with respect to bacterial cell surface binding and uptake. For ciliates, 10 mg HA L(-1) significantly reduced uptake of Cu by Uronema, but did not reduce uptake of Cu by Pleuronema. Uronema exposed to 67 microg Cu L(-1) accumulated 54% less Cu when 10 mg HA L(-1) was present (0.50 pg ciliate(-1) vs 0.23 pg ciliate(-1)). Uronema feeding on V. natriegens, took up less than half as much Cu as unfed Uronema when exposed to Cu without HA (0.41 pg Cu fed ciliate(-1) vs 0.86 pg Cu unfed ciliate(-1), but only 40% less when exposed to Cu and HA (0.31 pg Cu fed ciliate(-1) vs 0.51 pg Cu unfed ciliate(-1)). The lower % reduction attributable to fed ciliates in the presence of HA suggests that some of the Cu associated with HA is available through trophic processes.     

回灌型准好氧填埋场脱氮特性及加速稳定化研究

采用2个模拟填埋生物反应器,1号柱渗滤液简单回灌,2号柱为渗滤液回灌准好氧联合运行方式,研究了渗滤液回灌准好氧生物反应器填埋场的脱氮特性及加速垃圾稳定化特性.研究结果表明:渗滤液回灌准好氧填埋场具有很强的脱氮能力,2号柱由厌氧运行方式改为准好氧条件下,渗滤液中的氨氮和凯式氮浓度分别由最大值的3 198 mg/L和3 345 mg/L降低到第160 d的73 mg/L和81 mg/L,去除率分别为97.7%和97.6%,pH快速升高到8.0左右,COD浓度快速降低.渗滤液中溶解性有机物(DOM)分级结果表明,2号柱HA和FA含量的增加明显快于1号柱.2号柱DOM的三维荧光光谱特性发生了较大变化,荧光基团从60 d结构简单的类蛋白物质转变为95 d结构复杂的类胡敏酸和富里酸物质,而l号柱渗滤液DOM荧光基团一直是结构简单的类蛋白物质.结果表明回灌准好氧生物反应器填埋场的稳定化速度远快于简单回灌的生物反应器填埋场.     

Are photocatalytic processes effective for removal of airborne viruses from indoor air? A narrative review

A wide variety of methods have been applied in indoor air to reduce the microbial load and reduce the transmission rate of acute respiratory diseases to personnel in healthcare sittings. In recent months, with the occurrence of COVID-19 pandemic, the role of portable ventilation systems in reducing the load of virus in indoor air has received much attention. The present study delineates a comprehensive up-to-date overview of the available photocatalysis technologies that have been applied for inactivating and removing airborne viruses. The detection methods for identifying viral particles in air and the main mechanisms involving in virus inactivation during photocatalysis are described and discussed. The photocatalytic processes could effectively decrease the load of viruses in indoor air. However, a constant viral model may not be generalizable to other airborne viruses. In photocatalytic processes, temperature and humidity play a distinct role in the inactivation of viruses through changing photocatalytic rate. The main mechanisms for inactivation of airborne viruses in the photocatalytic processes included chemical oxidation by the reactive oxygen species (ROS), the toxicity of metal ions released from metal-containing photocatalysts, and morphological damage of viruses.

     

Sorption of phenanthrene by soils contaminated with heavy metals

The fate of polycyclic aromatic hydrocarbons (PAHs) in soils with co-contaminants of heavy metals has yet to be elucidated. This study examined sorption of phenanthrene as a representative of PAHs by three soils contaminated with Pb, Zn or Cu. Phenanthrene sorption was clearly higher after the addition of heavy metals. The distribution coefficient (K(d)) and the organic carbon-normalized distribution coefficient (K(oc)) for phenanthrene sorption by soils spiked with Pb, Zn or Cu (0-1000 mg kg(-1)) were approximately 24% larger than those by unspiked ones, and the higher contents of heavy metals added into soils resulted in the larger K(d) and K(oc) values. The enhanced sorption of phenanthrene in the case of heavy metal-contaminated soils could be ascribed to the decreased dissolved organic matter (DOM) in solution and increased soil organic matter (SOM) as a consequence of DOM sorption onto soil solids. Concentrations of DOM in equilibrium solution for phenanthrene sorption were lower in the case of the heavy metal-spiked than unspiked soils. However, the decreased DOM in solution contributed little to the enhanced sorption of phenanthrene in the presence of metals. On the other hand, the sorbed DOM on soil solids after the addition of heavy metals in soils was found to be much more reactive and have far stronger capacity of phenanthrene uptake than the inherent SOM. The distribution coefficients of phenanthrene between water and the sorbed DOM on soil solids (K(ph/soc)) were about 2-3 magnitude larger than K(d) between water and inherent SOM, which may be the dominant mechanism of the enhanced sorption of phenanthrene by soils with the addition of heavy metals.     

Structural and optical characterization of dissolved organic matter from the lower Athabasca River, Canada

Dissolved organic matter (DOM) is a ubiquitous constituent of natural waters and is comprised of a variety of chemically heterogeneous molecular structures and functional groups. DOM is often considered to be a major ligand for metals in most natural waters and its reactivity is thought to be strongly dependent on its chemical composition and structure. In this study, a combination of UV/visible, emission excitation matrix fluorescence (EEM) and ¹H NMR spectroscopies were used to characterize DOM from the Athabasca River (Alberta, Canada). The chemical characterization of river DOM showed that the most upstream samples located in agricultural areas were blue-shifted and less aromatic and contained more hydrogens connected with oxygen functional groups than those in the wetland dominated area in the Athabasca oil sand deposit region. The presence of paramagnetic ions (Fe and Al) was not found to significantly affect the structural composition of DOM as revealed by ¹H NMR. Such change in the quality of DOM may have a profound impact on metal binding in the Athabasca River watershed.