Biodegradation of Synthetic Dyes—A Review

The upper Great Egg Harbor River watershed in New Jersey’s Coastal Plain is urbanized but extensive freshwater wetlands are present downstream. In 2006–2007, studies to assess levels of total mercury (THg) found concentrations in unfiltered streamwater to range as high as 187 ng/L in urbanized areas. THg concentrations were <20 ng/L in streamwater in forested/wetlands areas where both THg and dissolved organic carbon concentrations tended to increase while pH and concentrations of dissolved oxygen and nitrate decreased with flushing of soils after rain. Most of the river’s flow comes from groundwater seepage; unfiltered groundwater samples contained up to 177 ng/L of THg in urban areas where there is a history of well water with THg that exceeds the drinking water standard (2,000 ng/L). THg concentrations were lower (<25 ng/L) in unfiltered groundwater from downstream wetland areas. In addition to higher THg concentrations (mostly particulate), concentrations of chloride were higher in streamwater and groundwater from urban areas than in those from downstream wetland areas. Methylmercury (MeHg) concentrations in unfiltered streamwater ranged from 0.17 ng/L at a forest/wetlands site to 2.94 ng/L at an urban site. The percentage of THg present as MeHg increased as the percentage of forest + wetlands increased, but also was high in some urban areas. MeHg was detected only in groundwater <1 m below the water/sediment interface. Atmospheric deposition is presumed to be the main source of Hg to the wetlands and also may be a source to groundwater, where wastewater inputs in urban areas are hypothesized to mobilize Hg deposited to soils.     

An Easy Method to Measure Total Particulate Hg in Water Without Chemical Digestion

Particle transport often plays an important role in trace metal cycling in aquatic systems. In this study, we propose a simple method to estimate total particulate Hg in water using combustion as a treatment prior to analysis as opposed to conventional chemical digestion. We also present a field validation of this method in a stream. We sampled water from a stream 24 and 48 h after a heavy storm to obtain two sets of water samples with contrasting particulate Hg levels. Measurements of particulate and dissolved Hg using our new direct combustion method compared favorably with those of total Hg in unfiltered samples (112 ± 15 %). U.S. E.P.A. standard method 1631 gave similar dissolved Hg levels but different particulate Hg levels (calculated as the difference between total and dissolved Hg concentrations) than those obtained with our new method. We suggest that this discrepancy is explained by the propagation of errors resulting from the several calculation steps used in the standard method. Our new method gives reliable results, without labor intensive and costly chemical digestion and analysis of filters.     

Fulvic Acid-Sulfide Ion Competition for Mercury Ion Binding in the Florida Everglades

Negatively charged functional groups of fulvic acid compete with inorganic sulfide ion for mercury ion binding. This competition is evaluated here by using a discrete site-electrostatic model to calculate mercury solution speciation in the presence of fulvic acid. Model calculatedspecies distributions are used to estimate a mercury-fulvicacid apparent binding constant to quantify fulvic acid and sulfide ion competition for dissolved inorganic mercury (Hg(II)) ion binding. Speciation calculations done with PHREEQC,modified to use the estimated mercury-fulvic acid apparent binding constant, suggest that mercury-fulvic acid and mercury-sulfide complex concentrations are equivalent for very low sulfide ion concentrations (about 10^-11 M) in Everglades' surface water. Where measurable total sulfide concentration (about 10^-7 M or greater) is present inEverglades' surface water, mercury-sulfide complexes shoulddominate dissolved inorganic mercury solution speciation. Inthe absence of sulfide ion (for example, in oxygenated Everglades' surface water), fulvic acid binding should dominateEverglades' dissolved inorganic mercury speciation.     

Transport of polychlorinated biphenyls (PCBs) in freshwater mesocosms from sediment to water and air

With sediment as a source the flux of PCBs to water and air was followed in mesocosms with and without fish for two vegetation seasons. The fish represented the largest lipid pool in the mesocosm, and their presence increased the flux of PCBs across the sediment/water interface. The flow of PCBs from sediment to water followed a seasonal pattern with higher rates during summer than in the winter. The rates were governed by the turbation activity of benthic invertebrates, the extent of gas production in the sediment, the amount and quality of the lipid pools in the water column, and the solubility of the PCBs. The greatest amount of PCBs among the lipid pools was found in the dissolved extractable lipids, which also showed the highest concentration of PCBs calculated on a lipid basis. After about 1.5 yr, >90% of the PCBs added was still in the sediment. The remainder was distributed within the mesocosms to various extents depending on the amount and quality of the lipid pools, or transferred into the air. Transfer into the air was governed by PCB concentrations in the water, and by water temperature. The flow was highest during summer, when the surface microlayer renewed its load of PCBs every 8th day.     

Assessment of Mercury in Water, Sediments and Biota of a Southern European Estuary (Sado Estuary, Portugal)

The aim if this study was to assess the distribution of mercury in water, suspended particulate matter, surface sediments and biota from the Sado estuary, which, for the most part, is classified as a natural reserve, so as to evaluate its environmental quality status in terms of mercury contamination. Besides the diffuse sources of mercury coming into the Sado estuary, there are also additional contributions from the northern industrial zone and from the urban areas within the system. Applying national and international guidelines to different environmental matrices, the results obtained show that the system does not seem to be under environmental risk as far as mercury contamination is concerned. These quality guidelines can be used to rank and prioritise sites of concern. Hence, the area at the northern industrialised area deserves particular attention. The concentration of mercury in sediments of this area (0.54?mg kg^?1) simultaneously succeeded the European Union Water Framework Directive (EU-WFD) reference value, the OSPAR Convention Ecotoxicological Assessment Criteria (EACs) and is classified as class 2 in degree of contamination by the National legislation, which implies some legal restrictive rules. Considering the stations close to urbanised areas, one exceeded the OSPAR EACs for dissolved mercury, whilst the other exceeded the EU-WFD reference value for mercury concentrations in sediments. No statistical significant relations were found between mercury concentrations in biota (Ulva sp, Hediste diversicolor, Scrobicularia plana, Cerstoderma edule and Carcinus maenas) and in the abiotic matrices (sediment and water column, including mercury in its dissolved form and associated to suspended particulate matter). This paper provides an overview of the guidelines for Hg proposed for a considerable number of coastal systems of the northern hemisphere and highlights the complex interactions of Hg in the different environmental compartments in low contaminated systems.     

Distribution of Zn in a Northwestern Mediterranean River

Determination of Zn in the aqueous, suspended and sedimentary phases of the Rhone River was carried out by differential pulse anodic stripping voltammetry with static mercury drop electrode. For total desorbable Zn (operationally defined as that measured on unfiltered water at pH 1.5 to 2) the concentration was 2.0 ± 0.6 μg L^?1 in unfiltered upstream water (8 stations) and in the unfiltered delta water (2 stations) was 1.05 ± 0.25 μg L^?1. The delta values are slightly higher than values found recently for estuaries of other rivers such as the Amazon and Yangtse, but non-delta values correspond mainly with those from relatively unpolluted areas. Overall, in non-delta water about 35% of the Zn was in true solution, 25% adsorbed on suspended material and 40% was in the suspended material but not desorbable. The calculatedK _d for Zn on the suspended material was about 2.5E4. The Zn content in suspended matter including adsorbed Zn was 69 ± 33 mg kg^?1, much lower than other literature values, and is approximately equivalent to the concentration in fine sediment fractions. The Zn in Rhone river sediment was on average 40 times the amount from nearby non-industrialized areas such as the Roya river.     

Potential for Phosphate Mitigation from Agricultural Runoff by Three Aquatic Macrophytes

Phosphate from agricultural runoff is a major contributor to eutrophication in aquatic systems. Vegetated drainage ditches lining agricultural fields have been investigated for their potential to mitigate runoff, acting similarly to a wetland as they filter contaminants. It is hypothesized that some aquatic macrophytes will be more effective at removing phosphate than others. In a mesocosm study, three aquatic macrophyte species, cutgrass (Leersia oryzoides), cattail (Typha latifolia), and bur-reed (Sparganium americanum), were investigated for their ability to mitigate phosphate from water. Mesocosms were exposed to flowing phosphate-enriched water (10?mg?L^?1) for 6?h, left stagnant for 42?h, and then flushed with non-nutrient enriched water for an additional 6?h to simulate flushing effects of a second storm event. Both L. oryzoides and T. latifolia decreased the load of dissolved phosphate (DP) in outflows by greater than 50?%, significantly more than S. americanum, which only decreased DP by 15?±?6?% (p????0.002). All treatments decreased concentrations inside mesocosms by 90?% or more after 1?week, though the decrease occurred more rapidly in T. latifolia and L. oryzoides mesocosms. By discovering which species are better at mitigating phosphate in agricultural runoff, planning the community composition of vegetation in drainage ditches and constructed wetlands can be improved for optimal remediation results.     

Influence of Natural Sources on Mercury in Water, Sediment and Aquatic Biota in Seven Tributary Streams of the East Fork of the Upper Carson River, California

The East Fork of the Upper Carson River (EFUCR) drainagebasin contains the Leviathan mine site, a known source of acidmine drainage, and numerous small prospects and mineralizedareas, some of which are enriched in mercury. In 1999 aninvestigation was undertaken to characterize total mercuryconcentrations in water, sediment, and whole aquaticmacroinvertebrates from seven tributaries of the EFUCR watershedon a seasonal time step. In the fall, methyl mercury in water,sediment and Stoneflys was determined for three sites. Both total and dissolved mercury in water at all sites, notimpacted by acid mine drainage, exhibited a seasonal trend withthe lowest concentrations occurring in the winter, higherconcentrations in the summer, and the highest concentrationsrecorded in the fall. Winter samples were taken during a periodof ice melt. It is hypothesized that the high fall concentrations were due to elevated mercury concentrations ingroundwater, which was recharging the stream under baseflow conditions and had interacted with substrate naturally enrichedin mercury. Mercury concentrations in Leviathan Creek wereelevated when acid mine drainage was being discharged directlyinto the Creek. Mercury concentrations in individual stoneflyscollected from specific stream reaches were similar, and methylmercury and total mercury concentrations in macroinvertebratetissue were roughly equivalent. Comparison of mercury bodyburden of macroinvertebrates between tributaries showed thatmacroinvertebrates in the Cottonwood Creek watershed had highermercury concentrations relative to the other sites. Thistributary had higher sediment mercury concentrations than allsimilar tributaries not impacted by acid mine drainage.     

Development of a fugacity/aquivalence model of mercury dynamics in lakes

A simple, mechanistic model of mercury (Hg) dynamics in a lake has been developed, based on the fugacity/aquivalence approach of Mackay (1991) and Mackay and Diamond (1989) and its extension to treat several interconverting chemical species (Diamond et al., 1992). The model considers the distribution of inorganic (HgII), elemental (Hg°) and methyl (MeHg) mercury species between dissolved and particle-sorbed phases, and fate and transport in a system consisting of a well-mixed water column and an active sediment layer. Hg can enter the lake from watershed runoff and by atmospheric deposition directly to the lake surface. Once in the lake, Hg exchanges between water and air, and water and sediments, and exits by sediment burial, advective flow and volatilization. The model was applied to a hypothetical drainage lake on the Canadian Shield. Model estimates of water and sediment concentrations compare well with measured values. The results suggest that the three Hg species experience significantly different fates and persistence, with overall Hg dynamics dominated by the fate of HgII (the predominant species). A sensitivity analysis illustrates the importance of physical/chemical properties and lake characteristics on the total amount and behavior of Hg in the lake.     

3-Chlorophenol Biodegradation in a Sequencing Batch Reactor: Kinetic Study and Effect of the Filling Time

Mercury pollution in the Second Songhua River (SSR) was serious in the last century due to effluent from a chemical corporation. Effects of riverine self-purification on mercury removal were studied by comparing monitoring data of mercury concentrations varieties in water, sediment, and fish in the past, about 30 years. The present work suggested that a river of such a size like the SSR possessed the potential ability to recover from mercury pollution under the condition that mercury sources were cut off, though it needs a very long time, which might be several decades or even a century of years. During the 30 years with no effluent containing mercury input, total mercury (T-Hg) of water and sediment in some typical segments, mostly near the past effluent outlet, had decreased radically but still higher than the background values, though the decrease amplitudes were over 90% compared with that in 1975. T-Hg had decreased by more than 90% in most fishes, but some were still not suitable for consumption. Methylmercury concentrations (MeHg) of water, sediment, and fish were higher or close to the background levels in 2004. In the coming decades, the purification processes in the SSR would be steady and slow for a long period.     

Modeling of Solute Transport with Bioremediation Processes using Sawdust as a Matrix

Hg and As are widespread contaminants globally and particularly in Asia. We conducted a field study in Baiyangdian Lake, the largest lake in the North China Plain, to investigate bioaccumulation and trophic transfer of potentially toxic metals (total mercury and arsenic) in sites differing in proximity from the major point sources of nutrients and metals. Hg concentrations in fish and As concentrations in water are above critical threshold levels (US Environmental Protection Agency based) considered to pose some risk to humans and wildlife. Hg concentrations in biota are within the range of concentrations in lakes in the Northeast US despite the high levels of Hg emission and deposition in China whereas As concentrations are much higher. Dissolved concentrations of both Hg and As decrease with increasing chlorophyll concentrations suggesting that there is significant uptake of metal from water by algae. These results provide evidence for algal blooms controlling dissolved metal concentrations and potentially mitigating the trophic transfer of Hg to fish. This study also underscores the need for further investigation into this contaminated ecosystem and others like it in China that are an important source of fish and drinking water for consumption by local human populations.     

Wet and dry deposition of nutrients in Central Alberta

Dry and wet deposition rates of various forms of phosphate and N and of Fe, sulphate, Na, K, and silica ions are reported for a 1 yr period in central Alberta. The results are extrapolated from event samples of rain and snow, and from dry deposition samples in distilled water collectors and snowpack. Following corrections for contamination and evaporation the most reliable dry deposition rates are found for orthophosphate, organic and nitrate N, and Fe, sulphate, and K ions. Ion concentrations in snow are significantly lower than those in rain for ammonia, organic, and total N and for sulphate and silica ions. More than 50% of the concentrations of total phosphate and total N in wet deposition samples is dissolved or in fine particles (less than 0.45 μ) but only about one third of dry deposition sample concentrations is in such form. Dry-to-wet deposition ratios for the year exceed one for filtered total N, filtered total phosphate, Fe, and sulphate. The largest dry-to-wet deposition ratios are about 5 for sulphate and unfiltered total N.     

Mobility and Availability of Copper in Agricultural Soils Irrigated from Water Treated with Copper Sulfate Algaecide

A mesocosm system was designed to study evaporation kinetics and transport of TCE in flowing surface water. The airtight unit, with a total internal volume of 52.01?×?10^?2 m³, was fabricated with glass and Teflon material, and was provided with 8.53 m long channel to simulate water flow in an open channel. The peristaltic pumps, connected to the inlet and the outlet of the mesocosm, provided a constant water flow through the channels. The experimental studies were conducted at two different velocities, 9.42?×?10^?3 and 4.71?×?10^–3 m/s, respectively. For both the velocities, a tracer (NaBr) test confirmed uniform water flow in the channels. The total length and the length between the sampling ports were found sufficient to record gradual decrease in TCE concentrations along the direction of the flow in the channels. The volatilization coefficient for TCE was found to be 0.49 and 1.07 h^?1 for the experiments conducted at lower and higher water velocities, respectively. The TCE evaporation half life (t 1/2) and the corresponding evaporation half distance (d 1/2) were 1.41 h and 23.98 m for lower velocity, and 0.65 h and 21.96 m for higher velocity, respectively.     

Effect of Abiotic and Biotic Factors on the Photo-Induced Production of Dissolved Gaseous Mercury

This study was conducted to evaluate the contribution of environmental factors such as solar radiation and dissolved organic matter (DOM) on the photo-induced dissolved gaseous mercury (DGM) production through laboratory experiments using field water samples collected from wetlands. DGM production was more significantly influenced by UVB intensity than UVA. DGM formation was also significantly affected by DOM chemical structure/composition rather than its concentration. Increasing NO ₃ ^? concentration limited DGM production, but photo-induced Hg oxidation stimulated by NO ₃ ^? would possibly occur when the NO ₃ ^? level is more than twice the DOC level. The addition of phosphorus into the field water samples induced a slight increase of DGM production; however, the addition of nitrogen decreased DGM formation, suggesting that an increase of limiting nutrients in water may promote biotic DGM production. Experiments using a Selenastrum capricornutum monoculture solution showed that cell density had a positive effect on DGM production. Moreover, the difference in DGM production between filtered and unfiltered samples showed that S. capricornutum significantly produced biotic DGM under UVA irradiation. Finally, our results imply that environmental factors such as light intensity, DOM sources, and site-specific microorganisms can significantly affect photo-induced Hg transformation.     

Comparison of Two Digestion Methods for Determining Total Phosphorus in Farm Canal Water

Abstract

Rapid and accurate determination of low‐level (0.01 to 1.0 mg L^?1) phosphorus (P) concentrations in farm canal water is important in evaluating water quality in the Everglades Agricultural Area (EAA) canals in south Florida. Two U.S. Environmental Protection Agency methods, persulfate digestion (365.1) and Kjeldahl digestion with mercury oxide (365.4), were used to analyze total P (TP) and total dissolved P (TDP) in two sets of representative canal water samples collected at low‐flow conditions in 2003 and high‐flow conditions in 2004. Quality assurance samples (blanks, duplicates, and spikes) were included to evaluate differences between the two digestion methods. Precision analysis had a mean of less than 5% for both TP and TDP using both methods. The high coefficient of correlations (r>0.98) indicated that the two methods were significantly correlated in determining TP and TDP of the samples. Low detection limits (0.004 mg L^?1) were achieved by the persulfate method. This method offers many other advantages over the mercury digestion: it produces no toxic mercury waste, uses less time, and uses a lower temperature. High suspended solids in canal water samples were not proven to be a problem when using the persulfate digestion, though lower spike recoveries were observed than those when using the mercury digestion. We conclude that persulfate digestion is a more sensitive and environmentally responsible alternative to and is, as precise as, the mercury method for routine determination of TP and TDP in water samples. This information is useful to environmental laboratories in monitoring P concentrations in surface and groundwater.     

Measurement of Atmospheric Mercury Species with Manual Sampling and Analysis Methods in a Case Study in Indiana

Ground-level concentrations of three atmospheric mercury species were measured using manual sampling and analysis to provide data for estimates of mercury dry deposition. Three monitoring stations were operated simultaneously during winter, spring, and summer 2004, adjacent to three mercury wet-deposition monitoring stations in northern, central, and southern Indiana. The monitoring locations differed in land-use setting and annual mercury-emissions level from nearby sources. A timer-controlled air-sampling system that contained a three-part sampling train was used to isolate reactive gaseous mercury, particulate-bound mercury, and elemental mercury. The sampling trains were exchanged every 6 days, and the mercury species were quantified in a laboratory. A quality-assurance study indicated the sampling trains could be held at least 120 h without a significant change in reactive gaseous or particulate-bound mercury concentrations. The manual sampling method was able to provide valid mercury concentrations in 90 to 95% of samples. Statistical differences in mercury concentrations were observed during the project. Concentrations of reactive gaseous and elemental mercury were higher in the daytime samples than in the nighttime samples. Concentrations of reactive gaseous mercury were higher in winter than in summer and were highest at the urban monitoring location. The results of this case study indicated manual sampling and analysis could be a reliable method for measurement of atmospheric mercury species and has the capability for supplying representative concentrations in an effective manner from a long-term deposition-monitoring network.     

Extractability and Bioavailability of Mercury from a Mercury Sulfide Contaminated Soil in Oak Ridge, Tennessee, USA

Historically as part of its national security mission, the U.S. Department of Energy’s Y-12 National Security Facility in Oak Ridge, TN acquired a significant fraction of the world’s supply of elemental mercury. During the 1950s and 1960s, a large amount of elemental mercury escaped confinement and is still present in the watershed surrounding the Y-12 facility. A series of remediation efforts have been deployed in the watersheds around the Oak Ridge site. However, most recently, concentration of total mercury in fish and water of the lower East Fork Poplar Creek (EFPC) of Oak Ridge has increased although majority of the mercury contamination in the local soils is present in the form of mercury sulfide. We have studied the extractability, solubility, and bioavailability of mercury sulfide in Oak Ridge soils. Dynamics of the dissolution of mercury sulfide by various extractants, including acids and a chelating agent, have been investigated. After three seasons of planting, soil mercury sulfide is more easily dissolved by both 4 M and 12 M nitric acid than is pure mercury sulfide reagent as indicated by their dissolution kinetics. Mercury release by EDTA from HgS-contaminated soil increased with time of reaction and soil mercury level. This chelating chemical increases the solubility of mercury in HgS-contaminated Oak Ridge soil. The results also show that mercury sulfide in contaminated Oak Ridge soils was still to some extent bioavailable to plants. The increase of bioavailability of soil mercury sulfide after three seasons of planting may contribute to the recent increase of mercury levels in water of the Lower East Fork Popular Creek (LEFPC) of Oak Ridge.     

Transport of Explosive Residue Surrogates in Saturated Porous Media

Department of Defense operational ranges may become contaminated by particles of explosives residues (ER) as a result of low-order detonations of munitions. The goal of this study was to determine the extent to which particles of ER could migrate through columns of sandy sediment, representing model aquifer materials. Transport experiments were conducted in saturated columns (2?×?20?cm) packed with different grain sizes of clean sand or glass beads. Fine particles (approximately 2 to 50?μm) of 2,6-dinitrotoluene (DNT) were used as a surrogate for ER. DNT particles were applied to the top 1?cm of sand or beads in the columns, and the columns were subsequently leached with artificial groundwater solutions. DNT migration occurred as both dissolved and particulate phases. Concentration differences between unfiltered and filtered samples indicate that particulate DNT accounted for up to 41% of the mass recovered in effluent samples. Proportionally, more particulate than dissolved DNT was recovered in effluent solutions from columns with larger grain sizes, while total concentrations of DNT in effluent were inversely related to grain size. Of the total DNT mass applied to the uppermost layer of the column, <3% was recovered in the effluent with the bulk remaining in the top 2?cm of the column. Our results suggest there is some potential for subsurface migration of ER particles and that most of the particles will be retained over relatively short transport distances.     

Influence of Physical and Chemical Characteristics on Mercury in Aquatic Sediments

Given the variation observed in mercury in fish from natural lakes, it is difficult to determine what represents a background mercury level. Mercury in aquatic sediments is a potential source of this trace metal to biota, notably fish. Site specific factors, such as acidity and dissolved organic carbon have been shown to affect the mobilization of mercury and methylation of mercury. Methyl mercury is the most toxic form of this metal and the form most readily accumulated by biota. Thirty-four headwater lakes, selected for a range in pH, were sampled for sediment mercury levels as part of an investigation of the impacts of acid rain on insular Newfoundland lakes. Selected physical and chemical data were also collected on all of the study sites. Acidity was not found to be significantly related to sediment mercury concentrations despite the wide range in pH. Pearson correlation analysis indicated that sediment mercury level was positively correlated with WA:LA (watershed to lake area ratio). WA:LA was also correlated with Secchi depth and colour. Linear regression was used to estimate the parameters of a model relating sediment mercury to WA:LA. Watershed area to lake area ratio was more important than site specific factors in governing the concentration of sediment mercury in lakes without industrial input.     

Mercury Speciation in the Water of Minamata Bay, Japan

The speciation of mercury (Hg) in Minamata Bay (Japan) was studied over a 2-year period (2006?C2008). Concentrations of dissolved total Hg, dissolved methylmercury (MeHg), particulate total Hg, and suspended solids were 0.43?±?0.14 ng/l (mean?±?standard deviation), 0.10?±?0.06 ng/l, 3.04?±?2.96 ng/l, and 5.94?±?2.10 mg/l, respectively. Correlations between concentrations of particulate total Hg and suspended solids at four depths (surface: 0 m; mid-depth: ?6 m, ?10 m; and bottom +1 m layer) were only significant in the bottom +1 m layer. The mean dissolved MeHg concentration and the ratio of dissolved MeHg to dissolved total Hg were considerably higher in summer compared to other seasons. The data suggest that bottom sediment was not the sole source of MeHg, and that MeHg may be produced in the water column by the conversion of divalent Hg eluted from resuspended bottom sediment. The correlation between seawater characteristics such as salinity, temperature, dissolved oxygen (DO), and dissolved MeHg concentration indicates that Hg methylation could be influenced by the heterotrophic activity of microorganisms in the seawater. In particular, inverse correlations were observed between DO, salinity, and MeHg concentration. However, dissolved MeHg concentrations did not correlate with seawater characteristics such as pH or chlorophyll-a.