Modeling copper partitioning in surface waters

Suspended particulate matter from the surface waters of the Susquehanna, Christina and Brandywine Rivers was collected by tangential flow filtration to study copper partitioning. Copper adsorption increased with an increase of suspended particles and decreased with low pH values or with an increase of dissolved organic matter. Effects of particulate organic matter on copper distribution between suspended particulate and solution phases were studied using modified aluminum oxide. An increase of particulate organic matter enhanced copper adsorption. Copper adsorption per mass of particulate organic carbon was similar for the different sources of suspended particles. A model, based on copper adsorption on particles and complexation with dissolved organic matter, was developed to assess copper partition coefficient as a function of the easily measurable water quality parameters: pH, alkalinity, dissolved organic carbon and particulate organic matter. The partitioning model was calibrated on pH edge data using suspended particles collected from the three rivers. The model was verified using partitioning data as a function of dissolved organic matter. The model adequately describes the system containing natural suspended solids collected from the surface waters.     

Organic matter transport and degradation in the river Seine (France) after a combined sewer overflow

The impact of a combined sewer overflow (CSO) upon receiving waters has been studied in the river Seine during Summers 1995 and 1996. Three main events have been monitored with special attention paid to the computation of oxygen, carbon and suspended solids budgets. Bacterial biomass and bacterial production rates have been measured to provide a more accurate understanding of the carbon cycle of the river Seine. Oxygen consumption inside the polluted water masses was totally due to the activity of large bacteria discharged into the river by the CSO, the activity of native small bacteria did not significantly increase after CSOs. Suspended solids issued from the CSO very quickly settles in this deep, slowly flowing river. However, discharged dissolved organic carbon (DOC) cannot account for the observed oxygen depletions, the additional carbon source could be phytoplankton or deflocculated/degraded particulate organic matter.     

Ultraviolet absorption properties of suspended particulate matter in untreated surface waters

Previous research has shown that wastewater disinfection using UV light can be impaired by attenuation of the UV light as it passes through particles to reach embedded and protected microorganisms. This study determined that the UV absorption (at 254 nm) of particles present in 10 untreated surface waters was similar to the absorption of wastewater particles. As such, it provides evidence that UV disinfection of surface waters during drinking water treatment may be impaired by the same mechanism if particles are present. The study also demonstrated that among the 10 untreated surface waters examined, there was no correlation between the UV absorption (254 nm) of the solid particulate material, total organic carbon, total suspended solids, turbidity, or UV absorbance (254) of the bulk water.     

Decay of intestinal enterococci concentrations in high-energy estuarine and coastal waters: towards real-time T90 values for modelling faecal indicators in recreational waters

Intestinal enterococci are the principal 'health-evidence-based' parameter recommended by WHO for the assessment of marine recreational water compliance. Understanding the survival characteristics of these organisms in nearshore waters is central to public health protection using robust modelling to effect real-time prediction of water quality at recreation sites as recently suggested by WHO and the Commission of the European Communities Previous models have more often focused on the coliform parameters and assumed two static day-time and night-time T90 values to characterise the decay process. The principal driver for enterococci survival is the received dose of irradiance from sunlight. In the water column, transmission of irradiance is determined by turbidity produced by suspended material. This paper reports the results of irradiated microcosm experiments using simulated sunlight to investigate the decay of intestinal enterococci in relatively turbid estuarine and coastal waters collected from the Severn Estuary and Bristol Channel, UK. High-turbidity estuarine waters produced a T90 value of 39.5 h. Low-turbidity coastal waters produced a much shorter T90 value of 6.6 h. In experiments receiving no irradiation, high-turbidity estuarine waters also produced a longer T90 of 65.1 h compared with corresponding low-turbidity coastal waters, T90 24.8 h. Irradiated T90 values were correlated with salinity, turbidity and suspended solids (r>0.8, p<0.001). The results suggest that enterococci decay in irradiated experiments with turbidity >200 NTU is similar to decay observed under dark conditions. Most significantly, these results suggest that modelling turbidity and or suspended solids offers a potential means of predicting T90 values in 'real-time' for discrete cells of a hydrodynamic model.     

Experimental and modelling study on the uptake and desorption kinetics of 133Ba by suspended estuarine sediments from southern Spain

Dispersion of pollutants in aquatic environments depends on their uptake by suspended solids. This work deals with the uptake kinetics of 133Ba (gamma-emitter and a good analogue of 226Ra) by suspended estuarine sediments (which can be resuspended into the water column under certain conditions). This study presents a wide set of tracing experiments, including second tracing, decantation and desorption processes. The purpose is to characterize 133Ba uptake by sediments and to investigate the use and limitations of box models in order to describe the uptake kinetics. Water and sediment samples were collected in the Huelva estuary (Spain), where environmental 226Ra concentrations have been increased by two phosphate fertilizer industries. Samples were characterized by granulometric, organic carbon content, cation exchange capacity and XRF-EP analyses. Results revealed three-step kinetics, with characteristic times of minutes, hours and days. These results enabled the selection and calibration of a suitable box model and facilitated the testing of its use as a fully predictive tool.     

Mercury in the river mersey, its estuary and tributaries during 1973 and 1974

Mercury levels found in waters and suspended matter from 53 stations, occupied four times at 3-monthly intervals, showed that most mercury was associated with particulates but the amount varied during the year. In the polluted region between Warrington and Runcorn, where fresh-water and sea-water converge, >80% of the mercury was associated with the particulates. Dissolved mercury concentrations and the mercury load on particulate matter were always greater in freshwater than in tidal waters, except during a flood. A model of partitioning of mercury between particulate and dissolved phases is presented. The River Weaver and the Manchester Ship Canal were grossly polluted with mercury throughout that year due to a Castner-Kelner plant at Runcorn. Dredge spoils and water flow transport 17 (range 8–138) and 1.55 ± 65% tonnes yr⁻¹ respectively of mercury into Liverpool Bay.     

Carbon and nitrogen isotopic compositions of particulate organic matter and biogeochemical processes in the eutrophic Danshuei Estuary in northern Taiwan

The Danshuei Estuary is distinctive for the relatively short residence time (1-2 d) of its estuarine water and the very high concentration of ammonia, which is the dominant species of dissolved inorganic nitrogen in the estuary, except near the river mouth. These characteristics make the dynamics of nitrogen cycling distinctively different from previously studied estuaries and result in unusual isotopic compositions of particulate nitrogen (PN). The delta(15)N(PN) values ranging from -16.4 per thousand to 3.8 per thousand lie in the lower end of nitrogen isotopic compositions (-16.4 to +18.7 per thousand) of suspended particulate matter observed in estuaries, while the delta(13)C values of particulate organic carbon (POC) and the C/N (organic carbon to nitrogen) ratios showed rather normal ranges from -25.5 per thousand to -19.0 per thousand and from 6.0 to 11.3, respectively. There were three major types of particulate organic matter (POM) in the estuary: natural terrigenous materials consisting mainly of soils and bedrock-derived sediments, anthropogenic wastes and autochthonous materials from the aquatic system. During the typhoon induced flood period in August 2000, the flux-weighted mean of delta(13)C(POC) values was -24.4 per thousand, that of delta(15)N(PN) values was +2.3 per thousand and that of C/N ratio was 9.3. During non-typhoon periods, the concentration-weighted mean was -23.6 per thousand for delta(13)C(POC), -2.6 per thousand for delta(15)N(PN) and 8.0 for C/N ratio. From the distribution of delta(15)N(PN) values of highly polluted estuarine waters, we identified the waste-dominated samples and calculated their mean properties: delta(13)C(POC) value of -23.6+/-0.7 per thousand, delta(15)N(PN) value of -3.0+/-0.1 per thousand and C/N ratio of 8.0+/-1.4. Using a three end-member mixing model based on delta(15)N(PN) values and C/N ratios, we calculated contributions of the three major allochthonous sources of POC, namely, wastes, soils and bedrock-derived sediments, to the estuary. Their contributions were, respectively, 83%, 12% and 5% under non-typhoon conditions, and 9%, 63% and 28% under typhoon conditions. The autochthonous POM had the most varied isotopic compositions, encompassing the full ranges of delta(13)C(POC) (-25.5 to -19.1 per thousand), delta(15)N(PN) (-16.4-3.8 per thousand) and C/N ratio (6.0-11.3). The heavy end of the carbon isotopic composition reflected the typical marine condition and the lower end the estuarine condition, which probably had elevated concentrations of dissolved inorganic carbon with low delta(13)C values due to input from decomposition of organic matter. The lack of isotopically heavy PN, as found in larger estuaries, was attributed to isotopically light starting materials, namely, anthropogenic wastes, the slow phytoplankton growth within the estuary and the rather short residence time; the latter two factors made (15)N enrichment during ammonia consumption very limited. The most isotopically light PN likely originated from phytoplankton incorporating (15)N-depleted nitrate near the river mouth, where ammonia inhibition of nitrate uptake probably stopped.     

Transport and sources of metal contaminants over the course of tidal cycle in the turbidity maximum zone of the Hudson River estuary

Transport and source of metal contaminants (Ag, Cd, Cu, Pb and Zn) in the turbidity maximum zone of the Hudson River estuary were studied over the course of a tidal cycle in November 1994 and August 1995. This study showed that the metal/Fe ratios in suspended particles varied more widely than those in the local sediments, implying that sources of metal contaminants to the water column are not only from local sediment resuspension but also from lateral advection. Although the metal/Fe ratios oscillate with time at the anchor stations, a general increasing trend with salinity was found over the course of a tidal cycle, suggesting that the lower estuary could be a source of metal contaminants to the upper estuary regions. These results support that sediment resuspension and lateral advection are important factors responsible for transporting the lower estuary contaminants up river and redistributing metal contaminants in the estuary.     

Effects of sedimentation on removal of faecal coliform bacteria from effluents in estuarine water

Faecal coliform deposition rates with estuary type suspended solids have been examined in laboratory experiments. Faecal coliform deposition rates in estuary water increased proportionately with suspended solids concentration, whereas faecal coliform deposition rates in effluent/seawater mixture showed no correlation with suspended solids concentration.

Deposition of estuary water suspended solids showed correlation with time, whereas deposition of effluent suspended solids showed no correlation with time. The adsorption efficiency experiments suggested immediate adsorption of some of the faecal coliforms onto both types of suspended solids and no difference in adsorption potential.

Therefore, it appears that the contrasting effects on faecal coliform deposition can be attributed to the different deposition potential of each type of suspended solids and not to the adsorption process.     

The effects of pH and suspended solids in the removal of organics from waters and wastewaters by the activated carbon adsorption process

The effects of pH, inorganic suspended solids and organic suspended solids on the adsorption of organics by activated carbon were investigated using sewage effluents and selected organic compounds of varying size, structure, molecular weight and properties in model solutions. It was found that suspended solids, and in particular organic suspended solids, could interfere with the adsorption process, both in terms of adsorption capacity and adsorption rate; the effect of the solids diminished as the size of the adsorbate increased. The effect of pH variation became more significant as the acidity or basicity of the adsorbate in solution increased. Adsorption of organics from biologically treated sewage effluents was somewhat more effective in the acid and alkaline pH regions than in the neutral pH region.     

Clay mineral and heavy metal distributions in the lower estuary of Huelva and adjacent Atlantic shelf,SW Spain

The Huelva estuary, on the south-western Spanish Atlantic coast, is an environment strongly polluted by acid mine drainage and industrial effluents. Clay mineralogy, heavy metal and particle-size distribution in estuarine and adjacent shelf sediments have been analyzed in order to identify the sources and transport pathways of the contaminated sediments. The estuarine sediments consist of detrital terrigenous minerals (illite, kaolinite, quartz, feldspars, dolomite and heavy minerals) derived from river catchments and coastal erosion, with biogenic components (calcite and aragonite) and minor authigenic minerals (pyrite and possibly gypsum). Mineral distribution pattern in the estuary-shelf system is controlled by grain-size sediment, physico-chemical conditions of waters and hydrodynamic factors. Important proportions of fine-grained sediments highly enriched in sulphide-associated heavy metals are supplied by the Tinto-Odiel river system. Most of these sediments are trapped when river waters reach the estuary because of flocculation processes during estuarine mixing, thus the estuary acts as a storage basin for metallic pollutants. In terms of public health, this estuary is well above recommended safety guidelines for most metals. Although the shelf sediments show metal concentration levels close to background values, eventually, a metallic plume emerges from the estuary to ocean, and consequently elevated metal concentrations can be locally detected on the inner shelf.     

The cycling of mercury through the environment

This paper reviews what is now known about the mercury cycle in the aquatic environment and indicates where the gaps in our knowledge lie. It describes the aquatic chemistry of mercury in the presence of chloride ions and the sulfate-sulfide system, the affinity of mercury for the sulfhydryl group in proteinaceous matter, the formation of methylated mercury compounds by microbial mediation, and the tendency for mercury in solution to adsorb on suspended solids. The paper then describes how mercury behaves in a typical local aquatic system based on facts known from its chemistry. It presents, finally, an estimate of the global cycle of mercury, and concludes that although man has created serious local problems by his indiscriminate discharge of mercury into the environment, he has had but negligible effect on a global scale.     

Study of river pollution caused by micropollutants

Of the polluting substances present in surface waters greatest importance is attributed to the micropollutants. Concerning the water quality of the Danube river, among the micropollutants, special attention should be devoted to the petroleum and phenol derivatives, further to some heavy metals (mercury, zinc, etc.). Phenolic compounds in the low concentrations encountered are readily soluble in water, so that they are present in small quantities only in the suspended solids and in the bottom sediment. Petroleum derivatives and fats are of great importance in this respect together with some heavy metals, which tend to adsorb to the suspended solids, respectively to form precipitates and thus to settle to the bottom.The investigations on quality variations were carried out over a Danube section upstream of Budapest. This section offers a model opportunity for studying changes in the pollutants tending to separate and form precipitates in water, the settling thereof as a function of flow conditions and time, etc.These investigations have offered an explanation for the “disappearance” of the persistent substances, which has been observed during the regular water analyses. The results of analyses performed on the water as well as on the bottom sediment are discussed in the paper.     

Effects of climate change on the wash-off of volatile organic compounds from urban roads

The predicted changes in rainfall characteristics due to climate change could adversely affect stormwater quality in highly urbanised coastal areas throughout the world. This in turn will exert a significant influence on the discharge of pollutants to estuarine and marine waters. Hence, an in-depth analysis of the effects of such changes on the wash-off of volatile organic compounds (VOCs) from urban roads in the Gold Coast region in Australia was undertaken. The rainfall characteristics were simulated using a rainfall simulator. Principal Component Analysis (PCA) and Multicriteria Decision tools such as PROMETHEE and GAIA were employed to understand the VOC wash-off under climate change. It was found that low, low to moderate and high rain events due to climate change will affect the wash-off of toluene, ethylbenzene, meta-xylene, para-xylene and ortho-xylene from urban roads in Gold Coast. Total organic carbon (TOC) was identified as predominant carrier of toluene, meta-xylene and para-xylene in < 1 μm to 150 μm fractions and for ethylbenzene in 150 μm to > 300 μm fractions under such dominant rain events due to climate change. However, ortho-xylene did not show such affinity towards either TOC or TSS (total suspended solids) under the simulated climatic conditions.     

Mercury removal from petrochemical wastes

The precipitation of mercury as mercury-starch-xanthate is studied. The process is studied in terms of optimum mercury-xanthate molar ratio, of influence of flocculation sedimentation times and of interferences (aluminum, iron, silica, chloride, organic substances and suspended solids).The studied reaction is advantageously applied to mercury removal from petrochemical wastes. The optimized process is applied both to a simulated and to a real wastewater, coming from a petrochemical industry (ANIC-Ravenna, Italy).     

Characterization of sewage solid-associated viruses and behavior in natural waters

The association of bacteriophages and animal viruses with solids has been demonstrated to have a protective effect, resulting in enhanced survival in natural waters and resistance to inactivation by chlorine. In this study, attempts were made to differentiate solid-associated viruses and freely suspended viruses in secondarily treated sewage by the retention of sewage solids on membrane filters treated with fetal calf serum to prevent adsorption of freely suspended virus. Solid-associated viruses collected on membrane filters were eluted with pH 11.5, 0.05 M glycine buffer. The percentage of the total coliphage and animal virus associated with solids in secondarily treated sewage discharges ranged from < 1.0 to 24% and 3 to 100%, respectively. The largest quantity of solid-associated coliphage was attached to particles greater than 8.0 μm and less than 0.65 μm in size. Tapwater, lake water and estuarine water were all capable of eluting solid-associated coliphages. Elution of coliphages in marine water appeared to be related to the salinity of the water. Coliphages eluted from sewage solids in seawater could readsorb to naturally occurring marine sediment.     

Behaviour of Hg species in a microtidal deltaic system: the Isonzo River mouth (northern Adriatic Sea)

Mercury species in the highly stratified water column of the Isonzo River mouth (northern Adriatic Sea) were investigated in February, May and August 2002 (low-normal fluvial discharge). Total, dissolved and particulate mercury (Hg) and methylmercury (MeHg) were measured and their concentrations were related to physico-chemical parameters in terms of temperature, salinity, turbidity, O(2) concentrations and total suspended matter (TSM) as well as particulate organic carbon (POC) content. Particulate Hg and MeHg are well correlated to medium-fine silty suspended sediment and organic matter, respectively. Desorption of Hg from particles in the brackish layer was observed. Due to the presence of a saltwedge, the lower river course seems to be a trap for Hg carried by fluvial waters. MeHg normally decreases approaching the sea but the local increase in the inner zone of the saltwedge could be related to methylation processes in the bottom water layer. Hg export is effective only during medium and high riverine flows acting as an important source of Hg into the northern Adriatic and the adjacent lagoon system.     

Mercury emission from a temperate lake during autumn turnover

Lakes in temperate regions stratify during summer and winter months, creating distinct layers of water differentiated by their physical and chemical characteristics. When lakes mix in autumn and spring, mercury cycling may be affected by the chemical changes that occur during mixing. Sampling was conducted in Lake Lacawac, Eastern Pennsylvania, USA, throughout the autumn of 2007 to characterize changes in emission of gaseous elemental mercury (Hg⁰) from the lake surface and dissolved mercury profiles in the water column during mixing. Water chemistry and weather parameters were also measured, including dissolved organic carbon (DOC), iron, and solar radiation which have been shown to interact with mercury species. Results indicate that emission of Hg⁰ from the lake to the atmosphere during turnover was controlled both by solar radiation and by surface water mercury concentration. As autumn turnover progressed through the months of October and November, higher mercury concentration water from the hypolimnion mixed with epilimnetic water, increasing mercury concentration in epilimnetic waters. Dissolved absorbance was significantly correlated with mercury concentrations and with iron, but DOC concentrations were essentially constant throughout the study period and did not exhibit a relationship with either dissolved mercury concentrations or emission rates. Positive correlations between dissolved mercury and iron and manganese also suggest a role for these elements in mercury transport within the lake, but iron and manganese did not demonstrate a relationship with emission rates. This research indicates that consideration of seasonal processes in lakes is important when evaluating mercury cycling in aquatic systems.     

Behaviour of persistent organochlorine micropollutants during primary sedimentation of waste water

The removal of polychlorinated biphenyls and the organochlorine insecticides gamma-HCH, aldrin, dieldrin and endrin during primary sedimentation of raw sewage has been studied using a pilot plant facility. A matrix of sixteen experiments was performed, where the pilot plant was operated at four different hydraulic loadings with four different influent suspended solids loadings. Significant removals of micropollutants into the primary sludge were observed, although no particular relationship with the removal of suspended solids was evident. It is concluded that a proportion of the organic microcontaminants present in raw sewage were associated with non-settleable solids and were also in the dissolved form. The significance of the behaviour of organochlorine micropollutants in waste water treatment processes and the hydrological cycle are discussed in the context of water re-use operations.     

Vanadium in particles and sediments of the northern Saronikos Gulf, Greece

This study provides data for total and non-residual vanadium distributions in the northern Saronikos Gulf and shows that close to the Athens sewage outfall (ASO), the combined domestic and industrial wastes have resulted in a considerable increase in concentrations of vanadium in sediments and suspended solids. This appears to be the main vanadium source in the area; a second major source is a fertilizer plant (FP) near the entrance of Piraeus Harbour (PH), the impact of which is also important. Atmospheric inputs from the Piraeus industrial site and frequent crude oil spillages from ships and land-based sources seem to contribute significantly to the observed vanadium distribution, which is clearly affected by the prevailing circulation of surface waters and winds. The high percentage of the 0.5 NHCl-leachable vanadium fraction in the most polluted sediments, together with positive correlation with organic carbon and certain other trace metals (i.e. Ag, Co, Cr, Fe, Zn) and negative correlation coefficients with Al and Sc, indicate that a considerable portion of the vanadium is of "anthropogenic" origin not related to lithogenous particles. It enters the system in association with relatively large organic aggregates, either authigenic or derived from sewage.