Suspended Phase Research Articles

Cycling of rare earth elements in the atmosphere in central Tokyo

Concentrations of 14 rare earth elements (REEs) in six size classes of airborne particulate matter (APM) (<0.43, 0.43-0.65, 0.65-1.1, 1.1-2.1, 2.1-11, and >11 μm) and in two different phases (suspended particulate and dissolved) in rainwater were determined by inductively coupled plasma mass spectrometry (ICP-MS). Positive Eu and Tb anomalies were observed in size-classified APM. These anomalies may be due to large emissions of Eu and Tb to the atmosphere resulting from the recent change in Japan from the use of cathode-ray tubes to plasma displays in television sets (Eu and Tb) and from the widespread use of magneto-optical disks (Tb). The light REEs were enriched in fine APM particles (diameter < 1.1 μm). Because compositions of La/Ce/Sm in fine APM (diameter < 1.1 μm) were similar to those in automobile catalyst, the light REE enrichment was attributed to automobile emissions. In contrast, the REE distribution pattern in the suspended particulate phase in rainwater was similar to that in coarse APM (diameter > 2.1 μm), and a positive Tb anomaly was observed, suggesting that coarse particles easily become trapped in rain droplets. A negative Eu anomaly was observed in the dissolved phase in rainwater, but not in APM or in the suspended particulate phase in rainwater. Unlike other REEs, Eu can exist as both bivalent and trivalent ions in nature, and Eu-selective dissolution from or adsorption onto the trapped particles of Eu might account for the negative anomaly. These results show that atmospheric REE cycling is affected by the physico-chemical properties of APM.

Liquid Chromatographic Determination of Scopolamine in Hair with Suspended Drop Liquid Phase Microextraction Technique

Hair analysis is used in some branches of alternative medicine as a method of investigation to assist diagnosis. It is very useful when a history of drug use is difficult or impossible to obtain. In this re-search suspended droplet liquid phase microextraction (SDLME) coupled with high-performance liquid chromatography and photodiode array detection (HPLC-DAD) was used for preconcentration and analysis of scopolamine in hair samples. Therefore scopolamine was extracted from 2.0 g hair sample incubated in methanol (5 h, 50°C) and adjusted to pH 7.4 with, Na2HPO4–H3PO4 buffer solution (donor phase, P1) into an organic phase (P2) 350 µl n-octanol and then back extracted into a micro drop of aqueous acceptor phase (P3), adjusted at pH 3, with HCL. The extraction time, T1 (from P1 to P2) was 2 min and T2 (from P2 to P3) was 30 min. Optimum instrumental conditions were included; A C18 reverse phase column with water-acetonitrile-methanol (80:10:10) as the mobile phase was used and wavelength for UV detec-tion was 205 nm. The linear range was 10 to 10000 ng●mL–1, enrichment factor, detec-tion limit and relative standard deviation were 77, 0.1 ng●mL–1 and 5.4 respectively.

Characterisation of plutonium species in alkaline liquors sampled from a UK legacy nuclear fuel storage pond

Within the UK there are a number of nuclear legacy fuel storage ponds and silos that contain substantial volumes of corroding spent Magnox fuel pieces. The fuel and wastes within these ponds, including highly radioactive sludges, must be retrieved and processed during decommissioning. Sludges and other intermediate level wastes will then be encapsulated in a wasteform suitable for storage and disposal, whilst residual activity must be removed from pond liquors and process effluents prior to any authorised discharges. Understanding the nature and behaviour of the radionuclides in the ponds, including any potential for activity transfer from solid to solution phases, is critical in the environmental clean up of these nuclear legacy facilities. Plutonium isotopes (with 241Am) dominate the α-activity within these ponds. Herein, the Pu species in samples taken from a UK legacy fuel storage pond and downstream Holding Tank on the Sellafield site are shown to be predominantly associated with suspended solid phases. Analyses of the residual soluble Pu concentrations indicate differences in Pu solubility between different areas of the pond, which speciation studies suggest are related to differing Pu oxidation state distributions. The implication is that Pu redox chemistry varies across the pond and this controls Pu solubilities and, by implication, Pu behaviour during waste processing. Simple treatment methods to suppress soluble Pu-α are also suggested.

Toxicity Characteristics of Drilling Mud and Its Effect on Aquatic Fish Populations

Toxicity tests are important for assessing the effects of complex chemical mixtures, such as waste drilling mud, on aquatic ecosystems. When waste drilling mud is released into the marine environment, strong ocean currents perhaps separate the drilling mud into a solid phase (SP) and a suspended particulate phase (SPP). A comprehensive assessment of drilling mud and base oil was carried out in the laboratory for acute fish toxicity (freshwater fish, marine fish, and benthic organisms) and biodegradability. The results presented in this paper indicate that the LC50 96 h for fresh water, marine and benthic organisms was in the order of base oil > SP > SSP. The 28-day biodegradability of base oil was also more than that of drilling mud. The results also showed that nonaqueous drilling fluids (NADFs) are readily biodegradable. The Spearmen results clearly showed the effects on fish populations from the discharge of drilling mud into aquatic systems. The results showed that the use of NADFs instead of water-based fluids (WBFs) would have lesser adverse impact on the envi- ronment. DOI: 10.1061/(ASCE)HZ.2153-5515.0000092. © 2012 American Society of Civil Engineers. CE Database subject headings: Drilling; Toxicity; Mud; Fish management; Aquatic habitats; Ecosystems. Author keywords: Drilling fluids; Solid phase; Suspended particulate phase; Base oil; Biodegradability.

Diagnosis and Quantification of Glycerol Assimilating Denitrifying Bacteria in an Integrated Fixed-Film Activated Sludge Reactor via13C DNA Stable-Isotope Probing

Glycerol, a byproduct of biodiesel and oleo-chemical manufacturing operations, represents an attractive alternate to methanol as a carbon and electron donor for enhanced denitrification. However, unlike methanol, little is known about the diversity and activity of glycerol assimilating bacteria in activated sludge. In this study, the microbial ecology of glycerol assimilating denitrifying bacteria in a sequencing batch integrated fixed film activated sludge (SB-IFAS) reactor was investigated using (13)C-DNA stable isotope probing (SIP). During steady state SB-IFAS reactor operation, near complete nitrate removal (92.7 ± 5.8%) was achieved. Based on (13)C DNA clone libraries obtained after 360 days of SB-IFAS reactor operation, bacteria related to Comamonas spp. and Diaphorobacter spp. dominated in the suspended phase communities. (13)C assimilating members in the biofilm community were phylogenetically more diverse and were related to Comamonas spp., Bradyrhizobium spp., and Tessaracoccus spp. Possibly owing to greater substrate availability in the suspended phase, the glycerol-assimilating denitrifying populations (quantified by real-time PCR) were more abundant therein than in the biofilm phase. The biomass in the suspended phase also had a higher specific denitrification rate than the biofilm phase (p = 4.33e-4), and contributed to 69.7 ± 4.5% of the overall N-removal on a mass basis. The kinetics of glycerol based denitrification by suspended phase biomass were approximately 3 times higher than with methanol. Previously identified methanol assimilating denitrifying bacteria were not associated with glycerol assimilation, thereby suggesting limited cross-utilization of these two substrates for denitrification in the system tested.

Large Convective Heat Transfer Enhancement in Microchannels With a Train of Coflowing Immiscible or Colloidal Droplets

We show that heat transfer in microchannels can be considerably augmented by introducing droplets or slugs of an immiscible liquid into the main fluid flow. We numerically investigate the influence of differently shaped colloidal or simply pure immiscible droplets to the main liquid flow on the thermal transport in microchannels. Results of parametric studies on the influence of all major factors connected to microchannel heat transfer are presented. The effect of induced Marangoni flow at the liquid interfaces is also taken into account and quantified. The calculation of the multiphase, multispecies flow problem is performed, applying a front tracking method, extended to account for nanoparticle transport in the suspended phase when relevant. This study reveals that the use of a second suspended liquid (with or without nanoparticles) is an efficient way to significantly increase the thermal performance without unacceptably large pressure losses. In the case of slug-train coflow, the Nusselt number can be increased by as much as 400% compared with single liquid flow.

Fundamentals of migrating multi-block lattice Boltzmann model for immiscible mixtures in 2D geometries

This paper proposes an extension scheme for the application of the single phase multi-block lattice Boltzmann method (LBM) to the multiphase Gunstensen model, in which the grid is refined in a specific part of the domain where a fluid–fluid interface evolves, and the refined grid is free to migrate with the suspended phase in the flow direction. The method is applicable to single and multiphase flows, and it was demonstrated by simulating a benchmark single phase flow around a 2D asymmetrically placed cylinder in a channel and for investigating the shear lift of 2D neutrally buoyant drop in a parabolic flow.

A mild, clean, and simple synthesis of symmetrical carboxylic anhydrides from carboxylic acides using a polymer supported tosyl chloride

The use of polymeric reagents simplifies routine acylation of carboxylic acid because it eliminates the traditional purification. We describe the use of readily available cross-linked poly(4-vinylpyridine) supported tosyl chloride, [P4VP].TsCl, in the suspended solution phase synthesis of symmetrical anhydrides from carboxylic acids in the presence of K2CO3 in high yields and purity. The products can be obtained by filtration and evaporation of the solvent.

Spatial and temporal variation of polychlorinated biphenyls in the Houston Ship Channel

An on-going study in the Houston Ship Channel (HSC) characterized polychlorinated biphenyl (PCB) levels in sediment, water, and tissue in 2002–2003 and 2008. The observed PCB concentration ranges in all media were higher than those measured in other PCB-impacted water bodies in the world, with the highest concentrations occurring within the industrialized segments. Contrary to polychlorinated dibenzo-p-dioxins/polychlorinated dibenzofurans (PCDD/PCDF) observations, the PCB concentrations in the dissolved phase were greater than the suspended phase. Possible explanations include passage of colloids, competition for adsorption sites from other hydrophobic contaminants, and continuing current sources. The PCB homologue distributions were similar for suspended water, sediment and tissue with the profile normalized around penta-chlorobiphenyls, while the dissolved phase profile normalized around tri-chlorobiphenyls. PCB-209 was detected in the suspended water phase and in sediment (10%) prompting interest into its sources to the HSC since PCB-209 was present only in rare commercial mixtures and is a byproduct in very few manufacturing processes. Inter-media analyses showed a significant correlation and transfer of PCBs. Dioxin-like PCBs contributed significant toxicity to total equivalent in tissue (33%), while they were insignificant in water (<10%) and sediment (<5%). The PCB concentrations over time showed a significant decrease in suspended water, sediment and tissue, while dissolved water concentrations showed insignificant change. The homolog distribution, however, showed a significant change in dissolved water and fish, a minor change in sediment and insignificant change in suspended water. Furthermore, an analysis for six representative congeners showed that they were accurate in predicting the total PCB concentrations and could be thus used as indicator PCBs.

Estrogenic and AhR activities in dissolved phase and suspended solids from wastewater treatment plants

The distribution of estrogen receptor (ERα) and Aryl Hydrocarbon Receptor (AhR) activities between the dissolved phase and suspended solids were investigated during wastewater treatment. Three wastewater treatment plants with different treatment technologies (waste stabilization ponds (WSPs), trickling filters (TFs) and activated sludge supplemented with a biofilter system (ASB)) were sampled. Estrogenic and AhR activities were detected in both phases in influents and effluents. Estrogenic and AhR activities in wastewater influents ranged from 41.8 to 79 ng/L E 2 Eq. and from 37.9 to 115.5 ng/L TCDD Eq. in the dissolved phase and from 5.5 to 88.6 ng/g E 2 Eq. and from 15 to 700 ng/g TCDD Eq. in the suspended solids. For both activities, WSP showed greater or similar removal efficiency than ASB and both were much more efficient than TF which had the lowest removal efficiency. Moreover, our data indicate that the efficiency of removal of ER and AhR activities from the suspended solid phase was mainly due to removal of suspended solids. Indeed, ER and AhR activities were detected in the effluent suspended solid phase indicating that suspended solids, which are usually not considered in these types of studies, contribute to environmental contamination by endocrine disrupting compounds and should therefore be routinely assessed for a better estimation of the ER and AhR activities released in the environment.

Parallel performance of a lattice-Boltzmann/finite element cellular blood flow solver on the IBM Blue Gene/P architecture

We discuss the parallel implementation and scaling results of a hybrid lattice-Boltzmann/finite element code for suspension flow simulations. This code allows the direct numerical simulation of cellular blood flow, fully resolving the two-phase nature of blood and the deformation of the suspended phase. A brief introduction to the numerical methods employed is given followed by an outline of the code structure. Scaling results obtained on Argonne National Laboratories IBM Blue Gene/P ( BG/P) are presented. Details include performance characteristics on 512 to 65,536 processor cores.

Partition of polychlorinated dibenzo-p-dioxins and dibenzofurans distribution in water in both suspended solid and dissolved phases

The contents of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) were measured in soil and water impacted by a chemical factory (chloralkali and pentachlorophenol) and both the PCDD/F contents in soil (14.4 μ g I-TEQ kg−1) and water (11.97 pg I-TEQ L−1) were heavily contaminated. Additionally, the PCDD/F distributions in the aquatic environment (suspended solid and dissolved phases) were investigated by performing a water tank experiment with 30 g of soil and 20 L of water. Moreover, the effects of PCDD/F distributions in water were estimated base on three soil sizes (26, 180 and 250 μ m). Analytical results indicated that the PCDD/F content in the suspended solid and dissolved phases was 2.19 μ g I-TEQ kg−1 and 2.34 pg I-TEQ L−1, respectively, or 85.11% and 14.89%, respectively. The PCDD/F distribution in the suspended solid phase was dominant, while its distribution was independent of soil size. Additionally, placing soil with a high PCDD/F content in water increased the PCDD/F content in suspended solid phase. Moreover, the equation developed in this study can accurately predict the PCDD/F partition between the suspended solid and dissolved phases.

Shelter From The Storm: Integrated Fixed Film Activated Sludge Protects Nitrifiers From Toxic Upsets

Shelter From The Storm: Integrated Fixed Film Activated Sludge Protects Nitrifiers From Toxic UpsetsThe potential benefits of integrated fixed film activated sludge (IFAS) with respect to protecting against chemical inhibitors of nitrification were evaluated in a pilot-scale study. Parallel IFAS and non-IFAS (Control) trains in A2O configurations were fed primary effluent from a full scale system. Chemical inhibition was evaluated in batch tests of both suspended phase (activated sludge) and...Author(s)Hyun-su KimClaudia GunschJ. GellnerJ. BoltzRobert G. FreudenbergAndrew J. SchulerSourceProceedings of the Water Environment FederationSubjectSession 18: Nitrogen Removal & BiofilmsDocument typeConference PaperPublisherWater Environment FederationPrint publication date Jan, 2010ISSN1938-6478SICI1938-6478(20100101)2010:17L.679;1-DOI10.2175/193864710798158085Volume / Issue2010 / 17Content sourceWEFTECFirst / last page(s)679 - 685Copyright2010Word count162Subject keywordsIntegrated fixed film activated sludgenitrificationinhibitiontoxic chemicalsprocess stabilityammonianitrate

The impact of mining activities on the hypersaline Mar Menor lagoon

Mar Menor lagoon is one of the largest hypersaline coastal lagoons in the Mediterranean Sea. The lagoon is threatened by environmental degradation due to the urban growth around it, the intensive agriculture in its watershed and the remains of mining activities in the nearby Cartagena-La Unio´n area. The present study aims at estimating the levels of zinc and lead in the water column, sediments and marine flora and fauna of Mar Menor lagoon. The ranges of the total concentrations in the water column were 9.36–28.7 &b.mu;g/L for Zn, 1.61–12.6 &b.mu;g/L for Pb and 3.01–29.70 &b.mu;g/L for Mn. Zinc was mostly found in the dissolved phase (70%) whereas lead and manganese in the suspended phase (63–76%). Highest values were measured at stations closer to streams flowing trough drainage basins including agricultural zone and the mining remains. Concerning sediments, the values were very high especially at the southern part, indicating transport of suspended matter from currents. The metal content in the sediments is higher than the content in particulate matter and there is an increased bioavailability of Zn and Pb. Zinc and lead were measured in the thallus of four marine flora species. Maximum zinc concentration was measured in Cymodosea nodosa (132 &b.mu;g/g) and maximum lead in Acetabularia acetabulum (93.5 &b.mu;g/g) in samples from the southern lagoon. From the two benthic fauna species studied, it was observed that heavy metals accumulate mostly in the animal flesh. The highest concentration of Zn and Pd was measured in the flesh of the mollusk Ostrea edullis with values of 1,856 and 51.0 &b.mu;g/g respectively. These values reveal the effect of heavy metal pollution in the lagoon ecosystem.

Effects of integrated fixed film activated sludge media on activated sludge settling in biological nutrient removal systems

Integrated fixed film activated sludge (IFAS) is an increasingly popular modification of conventional activated sludge, consisting of the addition of solid media to bioreactors to create hybrid attached/suspended growth systems. While the benefits of this technology for improvement of nitrification and other functions are well-demonstrated, little is known about its effects on biomass settleability. These effects were evaluated in parallel, independent wastewater treatment trains, with and without IFAS media, both at the pilot (at two solids residence times) and full scales. While all samples demonstrated good settleability, the Control (non-IFAS) systems consistently demonstrated small but significant ( p < 0.05) improvements in settleability relative to the IFAS trains. Differences in biomass densities were identified as likely contributing factors, with Control suspended phase density > IFAS suspended phase density > IFAS attached phase (biofilm) density. Polyphosphate content (as non-soluble phosphorus) was well-correlated with density. This suggested that the attached phases had relatively low densities because of their lack of anaerobic/aerobic cycling and consequent low content of polyphosphate-accumulating organisms, and that differences in enhanced biological phosphorus removal performance between the IFAS and non-IFAS systems were likely related to the observed differences in density and settleability for the suspended phases. Decreases in solids retention times from 8 to 4 days resulted in improved settleability and increased density in all suspended phases, which was related to increased phosphorus content in the biomass, while no significant changes in density and phosphorus content were observed in attached phases.

Evaluation of the autonomic response in healthy subjects during treadmill training with assistance of a robot-driven gait orthosis

Body weight supported treadmill training assisted with a robotic driven gait orthosis is an emerging clinical tool helpful to restore gait in individuals with loss of motor skills. However, the autonomic response during this rehabilitation protocol is not known. The aim of the study was to evaluate the autonomic response during a routine protocol of motor rehabilitation through spectral and symbolic analyses of short-term heart rate variability in a group of 20 healthy subjects (11 men, mean age 25 ± 3.8 years). The protocol included the following phases: (1) sitting position; (2) standing position; (3) suspension during subject instrumentation; (4 and 5) robotic-assisted treadmill locomotion at 1.5 km/h and 2.5 km/h respectively with partial body weight support; (6) standing recovery after exercise. Results showed a significant tachycardia associated with the reduction in variance during the suspended phase of the protocol compared to the sitting position. Spectral analysis did not demonstrate any significant autonomic response during the entire protocol, while symbolic analysis detected an increase in sympathetic modulation during body suspension and an increase of vagal modulation during walking. These results could be used to improve understanding of the cardiovascular effects of rehabilitation in subjects undergoing robotic driven gait orthosis treadmill training.

How Does IFAS Affect Distributions of AOB and NOB Communities? Population Measurements and Modeling of Pilot Scale Systems

Integrated fixed film activated sludge (IFAS) affects on performance and microbial populations of nitrifying bacteria were investigated in pilot scale systems with a non-IFAS control. Biomass from the suspended phase in the control system, the suspended phase in the IFAS system, and the attached phases from two aerobic reactors in series were analyzed through batch testing to determine rates of nitrification and populations structures in using quantitative PCR (qPCR). Suspended phases from IFAS and non-IFAS systems yielded similar rates of ammonia removal, which were higher than the attached biomass rates in the first aerobic reactor, while the second aerobic reactor attached growth provided the highest rates of nitrification. Nitrifier populations monitored by qPCR demonstrated the presence of the AOB Nitrosomonas oligotropha and the NOBs Nitrospira and Nitrobacter. Results from mathematical modeling calibrated to process performance was in agreement with qPCR measurements in terms of the relative quantities of AOBs and NOBs in the different phases.

Evaluation of Nitrification Kinetics for a 2.0 MGD IFAS Process Demonstration

The James River Treatment Plant (JRTP) operated a 2 MGD Integrated Fixed Film Activated Sludge (IFAS) demonstration process from November 2007 to April 2009 to explore IFAS performance and investigate IFAS technology as an option for a full scale plant upgrade in response to stricter nutrient discharge limits in the James River Basin. During the study, nitrification kinetics for both ammonia and nitrite oxidizing bacteria and plastic biofilm carrier biomass content were monitored on a near-weekly basis comparing the IFAS media, the IFAS process mixed liquor, and mixed liquor from the full-scale activated sludge process. Carrier biomass content is variable with respect to temperature and process SRT and relates to the localization of nitrification activity in the IFAS basin. Similar to trends observed for carrier biomass content (Regmi, 2008), ammonia oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB) activity also shifted from the fixed film to the suspended phase as water temperatures increased and vice versa as the temperature decreased. The data suggest that AOB activity occurs on the surface of the biofilm carriers, while NOB activity remains deeper in the biofilm. During the highest temperatures observed in the IFAS tank, AOB activity on the media contributed as little as 30% of the total nitrification activity in the basin, and after temperatures dropped below 20 °C, AOB activity in the fixed film phase made up 75% of the total activity in the IFAS basin. During the warmest period of the summer, the media still retained more than 60% of the total NOB activity, and more than 90% of the total NOB activity during the period of coldest water temperature. This trend also points out that some AOB and NOB activity remained in the mixed liquor, even during the coldest periods. The retention of nitrification activity in the

Polyfluorinated telomers in precipitation and surface water in an urban area of Japan

Although fluorotelomer alcohols (FTOHs) have been detected in various environmental matrices worldwide, no studies have been conducted to evaluate their concentrations in surface water or precipitation. Therefore, we developed a sensitive and reliable method to analyze various environmental aqueous samples for the presence of trace levels of 6:2 FTOH, 8:2 FTOH, 10:2 FTOH, 8:2 FTOAcr and 8:2 FTOMethacr FTOlefin using gas-chromatography/mass-spectrometry. The recoveries obtained using this method ranged from 57.8% to 78.2% and the detection limits were 0.5, 0.2, 0.2, 0.05 and 0.1 ng L −1 for 6:2 FTOH, 8:2 FTOH, 10:2 FTOH, 8:2 FTOAcr and 8:2 FTOMethacr, respectively. Liquid and suspended phases of the examined samples were analyzed. The analysis revealed presence of telomer alcohols from the liquid phase only. Of the FTOHs evaluated, 6:2 FTOH and 8:2 FTOMethacr FTOlefin were not found in any of the environmental samples. The average concentrations of 8:2 FTOH, 10:2 FTOH and 8:2 FTOAcr of the precipitation samples were 1.97, 0.82 and 0.21 ng L −1, respectively. In surface water samples, the highest concentrations of 8:2 FTOH, 10:2 FTOH and 8:2 FTOAcr were 3.38, 4.06 and 0.16 ng L −1, which were observed in samples from the Daini-Neyagawa, Yamato and Kanzaki rivers, respectively. The total concentration of FTOHs in wastewater treatment plant effluents (23.2 ng L −1) was much higher than that of surface water (10.8 ng L −1). Taken together, the results of this study indicate that FTOHs released into the air contaminate rain and that those released from water disposal sites contaminate surface water.

Chemical speciation in mining affected waters: the case study of Asarel-Medet mine

The inorganic chemical species in Maresh and Luda Yana rivers affected by the Cu- Mo Asarel-Medet mine, Bulgaria were determined during a low-flow and a high-flow period. The mining activities, the weathering and the oxidation processes strongly influenced the physicochemical processes in the whole water system. The main pollution source was a small lake receiving the acid effluents of the mining activities. High levels of SO4(2-), Cu, Mg, Al, Mn and Fe were determined at the mining polluted and affected stations. Cu(2+) and CuCO3(0) species (1:1) were present in the reference waters and Cu(2+) and CuSO4(0) species (1:1) in the polluted and affected waters; Cu(2+) species was dominating downstream. Me(2+) followed by MeSO4(0) (Me = Mn, Zn, Cd and Pb), PbCO3(0) and PbHCO3(+) species as well as Fe(OH)2(+), Al(OH)4(-), Al(OH)2(+), Al(OH)3(0) were prevailing in the system. MeSO4(+) and Me(SO4)2(-) (Me = Fe, Al), Me(SO4)2(2-) (Me = Zn, Cd and Pb), Me(SO4)3(4-) (Me = Zn, Cd) and Cd(SO4)4(6-) species polluted and affected waters. The major elements K and Na were mainly Me(+) species, whereas Ca and Mg were Me(2+) and MeSO4(0) species in different ratios. The concentration of concentration of NO2(-), NO3(-) and NO4(+) species as well as complex phosphorous species such as H2PO4(-), FeHPO4(+), HPO4(2-), CaPO4(-), CaHPO4(0) and MgHPO4(0) were also calculated. The trace element concentrations decreased downstream due to dilution, sorption processes and precipitation, but the percentage of free metal species, which are more toxic, increased. An exception was iron and aluminum of which the dominant hydroxy colloidal and sulphate species were easily incorporated into the suspended phase.