Determination of carbon, phosphorus, nitrogen and silicon species in waters

Sediment microbial fuel cell coupled floating treatment wetland for enhancing non-reactive phosphorus removal

The presence of non-reactive phosphorus (NRP) in environmental waters presents a potential risk of eutrophication and poses challenges for the removal of all phosphorus (P) fractions. This study presents the first investigation on the removal performance and mechanism of three model NRP compounds, sodium tripolyphosphate (STPP), adenosine 5'-monophosphate (AMP) and 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTC), in the sediment microbial fuel cell-floating treatment wetland (SMFC-FTW). Coupling SMFC with plants proved to be effective at removing NRP via electrochemical oxidation and plant uptake, particularly the challenging-to-degrade phosphonates that contain C-P bonds. Compared with the control group, the removal efficiencies of the model NRP in SMFC were observed to increase by 11.9%-20.8%. SMFC promoted the conversion of NRP to soluble reactive phosphorus (sRP) and the transfer of P to sediment. Furthermore, the electrochemical process enhanced both plant growth and P uptake, and increased P assimilation by 72.6%. The presence of plants in the bioelectrochemical system influenced the occurrence and fate of P by efficiently assimilating sRP and supporting microbial transformation of NRP. Consequently, plants enhanced the removal efficiencies of all P fractions in the overlying water. This study demonstrated that SMFC-FTW is a promising technology to remove various NRP species in environmental waters.

Ion chromatograph with three-dimensional printed absorbance detector for indirect ultraviolet absorbance detection of phosphate in effluent and natural waters

An ion chromatography system employing a low-cost three-dimensional printed absorbance detector for indirect ultraviolet detection towards portable phosphate analysis of environmental and industrial waters has been developed. The optical detection cell was fabricated using stereolithography three-dimensional printing of nanocomposite material. Chromatographic analysis and detection of phosphate were carried out using a CS5A 4 × 250 mm analytical column with indirect ultraviolet detection using a 255 nm light-emitting diode. Isocratic elution using a 0.6 mM potassium phthalate eluent combined with 1.44 mM sodium bicarbonate was employed at a flow rate of 0.75 ml/min. A linear calibration range of 0.5 to 30 mg/L PO₄ ^3- applicable to environmental and wastewater analysis was achieved. For retention time and peak area repeatability, relative standard deviation values were 0.68% and 4.09%, respectively. Environmental and wastewater samples were analyzed with the optimized ion chromatography platform and the results were compared to values obtained by an accredited ion chromatograph. For the analysis of environmental samples, relative errors of <14 % were achieved. Recovery analysis was also carried out on both freshwater and wastewater samples and recovery results were within the acceptable range for water analysis using standard ion chromatography methods.

Status and advances in technologies for phosphorus species detection and characterization in natural environment- A comprehensive review

Poor recovery of phosphorus (P) across natural environment (water, soil, sediment, and biological sources) is causing rapid depletion of phosphate rocks and continuous accumulation of P in natural waters, resulting in deteriorated water quality and aquatic lives. Accurate detection and characterization of various P species using suitable analytical methods provide a comprehensive understanding of the biogeochemical cycle of P and thus help its proper management in the environment. This paper aims to provide a comprehensive review of the analytical methods used for P speciation in natural environment by dividing them into five broad categories (i.e., chemical, biological, molecular, staining microscopy, and sensors) and highlighting the suitability (i.e., targeted species, sample matrix), detection limit, advantages-limitations, and reference studies of all methods under each category. This can be useful in designing studies involving P detection and characterization across environmental matrices by providing insights about a wide range of analytical methods based on the end user application needs of individual studies.

Organic phosphorus removal using an integrated advanced oxidation-ultrafiltration process

Non-reactive phosphorus (nRP) contains condensed phosphates and organic phosphorus (OP) species that are recalcitrant in secondary wastewater treatment and tend to remain in final effluents. To meet ultra-low effluent P discharge limits, persistent nRP must be removed. The objective of this study was to evaluate the use of an advanced oxidation process (AOP) which couples TiO₂/UV photolysis with ultrafiltration to oxidize and remove nRP species. Initial tests utilized OP model compounds, adenosine triphosphate (ATP) and aminoethylphosphonate (AEP), in a binary mixture to evaluate AOP treatment and to elucidate possible mechanisms of phosphorus removal. The results were consistent with a model of preferential ATP binding to the TiO₂ surface compared to AEP. On UV light exposure, AEP was removed from solution due to the photooxidation of ATP freeing up binding sites for AEP adsorption and subsequent oxidation. Orthophosphate released during AOP treatment was retained on the TiO₂ solids. The AOP was applied to three municipal wastewaters and one automotive industry effluent for P removal. In all cases, phosphorus removal was found to occur through filtration, surface complexation and UV oxidation. Total phosphorus removal efficiencies between 90 and 97% were observed for the municipal wastewater effluents and 44% removal was observed in the industrial effluent after treatment using AOP.

Rapid Colorimetric Screening of Elevated Phosphate in Urine: A Charge-Transfer Interaction

A charge-transfer (CT) interaction between 1,3,5-trinitro-2,4-dimethylbenzene (TNX) and anionic phosphate is evaluated, yielding a high band electronic transfer interaction that can be observed as a distinct color change when phosphate is present in solution. The induced interaction was studied using ¹H NMR, UV-visible, and Fourier transform infrared spectroscopies. The stoichiometric determination of the interaction was divined by means of continuous variation, applying the Schaeppi-Treadwell method to calculate the binding constant (k). Furthermore, the effect of the polarity of solvents toward the generation of the CT interaction was examined, with multiple solvents considered. Complex deconstruction studies were undertaken, examining the effects of water on complex destruction and understanding the volumes needed to hinder the CT interaction potency. Specificity and selectivity of the CT interaction were also studied against other biologically relevant species (CH₃CH₂OH, Na⁺, K⁺, Ca²⁺, Cl^-, HCO₃ ^-, F^-, CH₃COO^-, and SO₄ ^2-), assessing the capabilities of the assay to differentiate anionic species and counter cations that could act as interferences. The role of TNX concentration in CT formation was also analyzed, aiming to optimize the phosphate-sensing assay and improve its limit of detection. The sensing platform was subsequently used to study phosphate concentrations in urine samples to further understand its potential application in biomedical research. To validate the developed technique, urine samples were analyzed for their phosphate content with both the developed sensor and a validated vanadate-molybdate reagent. The results indicate that the sensing method is capable of accurately reporting elevated phosphate levels in urine samples in a rapid and sensitive manner, illustrating that the colorimetric test could be used as a prescreening test for conditions such as hyperphosphatemia or chronic kidney disease.

Fast room temperature cloud point extraction procedure for spectrophotometric determination of phosphate in water samples

A novel fast room temperature cloud point extraction (RT-CPE) procedure for preconcentration and spectrophotometric determination of phosphate based on the heteropoly blue formation was developed. The proposed method includes the formation of yellow molybdoantymonatophosphoric heteropoly complex, its extraction into Triton X-100 micellar phase obtained at room temperature and reduction of heteropoly complex by ascorbic acid solution in ethanol and absorbance measurement of heteropoly blue at 790 nm. Under optimal conditions (1% (v/v) of Triton X-100 and 0.05 M of ammonium benzoate for initiating of RT-CPE; 0.13 M ethanolic solution of ascorbic acid for reduction of heteropoly complex and dilution of surfactant rich phase), the calibration graph is linear in the range of phosphate concentrations of 1.58-63 μg L^-1. The proposed RT-CPE procedure has been successfully applied to preconcentration phosphates and its spectrophotometric determination in water samples.

Do organic matter metrics included in lake surveillance monitoring in Europe provide a broad picture of brownification and enrichment with oxygen consuming substances?

Organic matter (OM) has numerous geochemical and ecological functions in inland waters and can affect water quality. Different parameters of aquatic OM are measured with various methods as no single analytical tool can provide definitive structural or functional information about it. In the present paper we review different OM metrics used in the European Union (EU) lake surveillance monitoring programmes and assess their suitability to provide sufficient data about the brownification and enrichment with oxygen consuming substances in European lakes. In the EU Water Framework Directive (WFD), metrics of OM are not mandatory physico-chemical parameters, but only recommended parameters to characterize water transparency, oxygenation conditions or acidification status. Our analysis shows that, as lake OM is monitored under the WFD in only 14 countries, no Europe-wide conclusions on the situation regarding brownification and organic enrichment can be drawn based on these data. Applied parameters in lake surveillance monitoring programmes are biochemical oxygen demand (BOD), chemical oxygen demand (COD), total organic carbon (TOC), dissolved organic carbon (DOC), water colour (WCol), and yellow substance. Different national OM metrics used avoid getting a broad picture of lake OM concentration changes in Europe over the last decades. Furthermore, our results demonstrate that the possibilities to convert different OM parameters to each other are limited because empirical relationships between them are region-specific. OM sensors for continuous measurements and remote sensing surveys could improve the effectiveness of lake OM monitoring, especially its temporal and spatial representativeness. It would be highly suggested to include in lake monitoring programmes also methods (e.g. absorbance or fluorescence spectroscopy) allowing to characterize the composition of OM as it influences strongly the biogeochemical role of OM in lakes.

Indigo Carmine-Cu complex probe exhibiting dual colorimetric/fluorimetric sensing for selective determination of mono hydrogen phosphate ion and its logic behavior

A new selective probe based on copper complex of Indigo Carmine (IC-Cu₂) for colorimetric, naked-eye, and fluorimetric recognition of mono hydrogen phosphate (MHP) ion in H₂O/DMSO (4:1v/v, 1.0mmolL^-1 HEPES buffer solution pH7.5) was developed. Detection limit of HPO₄^2- determination, achieved by fluorimetric and ₃lorimetric method, are 0.071 and 1.46μmolL^-1, respectively. Potential, therefore is clearly available in IC-Cu₂ complex to detect HPO₄^2- in micromolar range via dual visible color change and fluorescence response. Present method shows high selectivity toward HPO₄^2- over other phosphate species and other anions and was successfully utilized for analysis of P₂O₅ content of a fertilizer sample. The results obtained by proposed chemosensor presented good agreement with those obtained the colorimetric reference method. INHIBIT and IMPLICATION logic gates operating at molecular level have been achieved using Cu²⁺and HPO₄^2- as chemical inputs and UV-Vis absorbance signal as output.

Effects of polyacrylamide on soil erosion and nutrient losses from substrate material in steep rocky slope stabilization projects

Erosion of denuded steep rocky slopes causes increasing losses of nitrogen and phosphorus, which is a severe problem in rocky slope protection. Thus, it is important to determine the appropriate materials that can reduce the erodibility and losses of nitrogen and phosphorus of the soil. In this paper, twenty-seven simulated rainfall events were carried out in a greenhouse, in which the substrate material was artificial soil; nine types of anionic polyacrylamide (PAM) were studied, which consisted of three molecular weight (6, 12, and 18 Mg mol(-1)) and three charge density (10, 20, and 30%) formulations in a 3 by 3 factorial design. The results showed that: (1) Polyacrylamide application reduced total nitrogen losses by 35.3% to 50.0% and total phosphorus losses by 34.9% to 48.0% relative to the control group. (2) The losses of total nitrogen and total phosphorus had significant correlation with the molecular weight. Besides, the losses of total phosphorus, particulate-bound phosphorus and inorganic nitrogen (NH4-N) were significantly correlated with their molecular weight and charge density. However, the losses of dissolved organic nitrogen, inorganic nitrogen (NO3-N), dissolved organic phosphorus, inorganic phosphorus (PO4-P) were non-significantly correlated with molecular weight and charge density. (3) Particulate-bound nitrogen and phosphorus were responsible for the losses of nitrogen and phosphorus during runoff events, where particulate-bound nitrogen made up 71.7% to 73.2% of total nitrogen losses, and particulate-bound phosphorus made up 82.3% to 85.2% of total phosphorus losses. (4) Polyacrylamide treatments increased water-stable aggregates content by 32.3% to 59.1%, total porosity by 11.3% to 49.0%, final infiltrative rate by 41.3% to 72.5%, and reduced soil erosion by 18.9% to 39.8% compared with the control group. Overall, the results of this study indicated that polyacrylamide application in the steep rocky slope stabilization projects could significantly reduce nutrient losses and soil erosion of substrate material.

Determination of phosphorus in natural waters: A historical review

The aim of this paper is to introduce a virtual special issue that reviews the development of analytical approaches to the determination of phosphorus species in natural waters. The focus is on sampling and sample treatment, analytical methods and quality assurance of the data. The export of phosphorus from anthropogenic activities (from diffuse and point sources) can result in increased primary production and eutrophication, and potentially the seasonal development of toxic algal blooms, which can significantly impact on water quality. Therefore the quantification of phosphorus species in natural waters provides important baseline data for studying aquatic phosphorus biogeochemistry, assessing ecosystem health and monitoring compliance with legislation.

Dynamic silver speciation as studied with fluorous-phase ion-selective electrodes: Effect of natural organic matter on the toxicity and speciation of silver

The widespread application of silver in consumer products and the resulting contamination of natural environments with silver raise questions about the toxicity of Ag(+) in the ecosystem. Natural organic matter, NOM, which is abundant in water supplies, soil, and sediments, can form stable complexes with Ag(+), altering its bioavailability and toxicity. Herein, the extent and kinetics of Ag(+) binding to NOM, matrix effects on Ag(+) binding to NOM, and the effect of NOM on Ag(+) toxicity to Shewanella oneidensis MR-1 (assessed by the BacLight viability assay) were quantitatively studied with fluorous-phase Ag(+) ion-selective electrodes (ISEs). Our findings show fast kinetics of Ag(+) and NOM binding, weak Ag(+) binding for Suwannee River humic acid, fulvic acid, and aquatic NOM, and stronger Ag(+) binding for Pony Lake fulvic acid and Pahokee Peat humic acid. We quantified the effects of matrix components and pH on Ag(+) binding to NOM, showing that the extent of binding greatly depends on the environmental conditions. The effect of NOM on the toxicity of Ag(+) does not correlate with the extent of Ag(+) binding to NOM, and other forms of silver, such as Ag(+) reduced by NOM, are critical for understanding the effect of NOM on Ag(+) toxicity. This work also shows that fluorous-phase Ag(+) ISEs are effective tools for studying Ag(+) binding to NOM because they can be used in a time-resolved manner to monitor the activity of Ag(+) in situ with high selectivity and without the need for extensive sample preparation.

Assessment of the nutrient removal effectiveness of floating treatment wetlands applied to urban retention ponds

The application of floating treatment wetlands (FTWs) in point and non-point source pollution control has received much attention recently. Although the potential of this emerging technology is supported by various studies, quantifying FTW performance in urban retention ponds remains elusive due to significant research gaps. Actual urban retention pond water was utilized in this mesocosm study to evaluate phosphorus and nitrogen removal efficiency of FTWs. Multiple treatments were used to investigate the contribution of each component in the FTW system with a seven-day retention time. The four treatments included a control, floating mat, pickerelweed (Pontederia cordata L.), and softstem bulrush (Schoenoplectus tabernaemontani). The water samples collected on Day 0 (initial) and 7 were analyzed for total phosphorus (TP), total particulate phosphorus, orthophosphate, total nitrogen (TN), organic nitrogen, ammonia nitrogen, nitrate-nitrite nitrogen, and chlorophyll-a. Statistical tests were used to evaluate the differences between the four treatments. The effects of temperature on TP and TN removal rates of the FTWs were described by the modified Arrhenius equation. Our results indicated that all three FTW designs, planted and unplanted floating mats, could significantly improve phosphorus and nitrogen removal efficiency (%, E-TP and E-TN) compared to the control treatment during the growing season, i.e., May through August. The E-TP and E-TN was enhanced by 8.2% and 18.2% in the FTW treatments planted with the pickerelweed and softstem bulrush, respectively. Organic matter decomposition was likely to be the primary contributor of nutrient removal by FTWs in urban retention ponds. Such a mechanism is fostered by microbes within the attached biofilms on the floating mats and plant root surfaces. Among the results of the four treatments, the FTWs planted with pickerelweed had the highest E-TP, and behaved similarly with the other two FTW treatments for nitrogen removal during the growth period. The temperature effects described by the modified Arrhenius equation revealed that pickerelweed is sensitive to temperature and provides considerable phosphorus removal when water temperature is greater than 25 °C. However, the nutrient removal effectiveness of this plant species may be negligible for water temperatures below 15 °C. The study also assessed potential effects of shading from the FTW mats on water temperature, DO, pH, and attached-to-substrate periphyton/vegetation.

Temporal variability in nutrient concentrations and loads in the River Tamar and its catchment (SW England) between 1974 and 2004

This study reports the results from the analyses of a 30-year (1974-2004) river water quality monitoring dataset for NO x -N (NO₃-N + NO2-N), NH₄-N, PO₄-P and SiO₂-Si at the tidal limit of the River Tamar (SW England), an agriculturally dominated and sparsely populated catchment. Annual mean concentrations of NH4-N, PO₄-P and SiO₂-Si were similar to other rural UK rivers, while annual mean concentrations of NO x -N were clearly lower. Estimated values for the 1940s were much lower than for those of post-1974, at least for NO₃-N and PO₄-P. Flow-weighted mean concentrations of PO₄-P decreased by approximately 60 % between 1974 and 2004, although this change cannot be unequivocally ascribed to either PO₄-P stripping from sewage treatment work effluents or reductions in phosphate fertiliser applications. Lower-resolution sampling (to once per month) in the late 1990s may also have led to the apparent decline; a similar trend was also seen for NH4-N. There were no temporal trends in the mean concentrations of NO x -N, emphasising the continuing difficulty in controlling diffuse pollution from agriculture. Concentrations of SiO₂-Si and NO x -N were significantly and positively correlated with river flows ≤15 m(3) s(-1), showing that diffuse inputs from the catchment were important, particularly during the wet winter periods. In contrast, concentrations of PO₄-P and NH4-N did not correlate across any flow window, despite the apparent importance of diffuse inputs for these constituents. This observation, coupled with the absence of a seasonal (monthly) cycle for these nutrients, indicates that, for PO₄-P and NH4-N, there were no dominant sources and/or both undergo extensive within-catchment processing. Analyses of nutrient fluxes reveal net losses for NO₃-N and SiO₂-Si during the non-winter months; for NO3-N, this may be due to denitrification. Areal fluxes of NO x -N from the catchment were towards the higher end of the range for the UK, while NH₄-N and PO₄-P were closer to the lower end of the ranges for these nutrients. These data, taken together with information on sestonic chlorophyll a, suggest that water quality in the lower River Tamar is satisfactory with respect to nutrients. Analyses of these monitoring data, which were collected at considerable logistical and monetary cost, have revealed unique insights into the environmental behaviour of key nutrients within the Tamar catchment over a 30-year period.

Detection of geothermal phosphite using high-performance liquid chromatography

Little is known about the prebiotic mechanisms that initiated the bioavailability of phosphorus, an element essential to life. A better understanding of phosphorus speciation in modern earth environments representative of early earth may help to elucidate the origins of bioavailable phosphorus. This paper presents the first quantitative measurements of phosphite in a pristine geothermal pool representative of early earth. Phosphite and phosphate were initially identified and quantified in geothermal pool and stream samples at Hot Creek Gorge near Mammoth Lakes, California, using suppressed conductivity ion chromatography. Results confirmed the presence of 0.06 +/- 0.02 microM of phosphite and 0.05 +/- 0.01 microM of phosphate in a geothermal pool. In the stream, phosphite concentrations were below detection limit (0.04 microM) and phosphate was measured at 1.06 +/- 0.36 microM. The presence of phosphite in the geothermal pool was confirmed using both chemical oxidation and ion chromatography/mass spectrometry.

Potentiometric evaluation of calix[4]arene anion receptors in membrane electrodes: Phosphate detection

Ion-selective membrane electrodes doped with the urea- or thiourea-functionalised calix[4]arenes, 5,11,17,23-tetra-tert-butyl-25,27-bis[[4-N'-(phenylureido)butyl]oxy]-26,28-dipropoxy calix[4]arene (I) and 5,11,17,23-tetra-tert-butyl-25,27-bis[[4-(N'-phenylthioureido)-butyl]oxy]-26,28-dipropoxy calix[4]arene (II), were evaluated for anion sensing. Potentiometric results show that these calixarene ionophore-based membrane electrodes exhibit a good sensitivity to aqueous solutions of the monohydrogen orthophosphate species HPO(4)(2-) in the concentration range 5.0 x 10(-5) to 1.0 x 10(-1)M, with near-Nernstian response slopes of -33.0 and -28.0 mV dec(-1) for ionophores I and II, respectively. Selectivity coefficient values for monohydrogen orthophosphate over a range of common anions were determined by the fixed interference and matched potential methods and indicated that these membrane electrodes exhibit a good selectivity for HPO(4)(2-) with respect to the other anions, including sulfate and nitrate.

Detection of phosphorus oxyanions in synthetic geothermal water using ion chromatography-mass spectrometry techniques

Recent developments in microbiology suggest that reduced inorganic phosphorus oxyanions, including hypophosphite and phosphite, may be present in nature. These studies have inspired the development of specific and sensitive methods that detect phosphorus oxyanions in natural water. This paper will discuss a new technique that couples suppressed conductivity ion chromatography (Dionex AS17 analytical column and potassium hydroxide eluent) with electrospray mass spectrometry (IC/MS) with limits of detection nearly 200 times lower than those reported using suppressed conductivity detection. The technique was optimized for the detection of hypophosphite, phosphite, and phosphate in a synthetic geothermal water matrix. Samples were pre-treated with silver and sulfonic acid cartridges, and injection loop sizes as large as 800microl were employed to enhance instrument sensitivity. All peaks were clearly resolved, and calibrations were linear with estimated 3sigma limits of detection of 0.011, 0.0020, and 0.029microM for hypophosphite, phosphite, and phosphate, respectively.

Analytical approaches to the determination of simple biophenols in forest trees such as Acer(maple), Betula(birch), Coniferus, Eucalyptus, Juniperus(cedar), Picea(spruce) and Quercus(oak)

Analytical methods are reviewed for the determination of simple biophenols in forest trees such as Acer (maple), Betula (birch), Coniferus, Eucalyptus, Juniperus (cedar), Picea (spruce) and Quercus (oak). Data are limited but nevertheless clearly establish the critical importance of sample preparation and pre-treatment in the analysis. For example, drying methods invariably reduce the recovery of biophenols and this is illustrated by data for birch leaves where flavonoid glycosides were determined as 12.3 +/- 0.44 mg g(-1) in fresh leaves but 9.7 +/- 0.35 mg g(-1) in air-dried samples (data expressed as dry weight). Diverse sample handling procedures have been employed for recovery of biophenols. The range of biophenols and diversity of sample types precludes general procedural recommendations. Caution is necessary in selecting appropriate procedures as the high reactivity of these compounds complicates their analysis. Moreover, our experience suggests that their reactivity is very dependent on the matrix. The actual measurement is less contentious and high performance separation methods particularly liquid chromatography dominate analyses whilst coupled techniques involving electrospray ionization are becoming routine particularly for qualitative applications. Quantitative data are still the exception and are summarized for representative species that dominate the forest canopy of various habitats. Reported concentrations for simple phenols range from trace level (<0.1 microg g(-1)) to in excess of 500 microg g(-1) depending on a range of factors. Plant tissue is one of these variables but various biotic and abiotic processes such as stress are also important considerations.

Detection of hypophosphite, phosphite, and orthophosphate in natural geothermal water by ion chromatography

Current doctrine states that phosphorus is incorporated into cells in the pentavalent(V) oxidation state as orthophosphate. However, recent studies show that microorganisms contain enzymes used to metabolize reduced forms of phosphorous, including phosphite(III) and hypophosphite(I), which suggests that there is a natural source for these chemical species. This paper will discuss suppressed conductivity ion chromatography methods developed to detect hypophosphite, phosphite, and orthophosphate in a geothermal water matrix containing fluoride, chloride, bromide, nitrate, hydrogen carbonate and sulfate. All peaks were clearly resolved, and calibrations were linear with estimated 3sigma detection limits of 0.83, 0.39, and 0.35 microM for hypophosphite, phosphite, and orthophosphate, respectively.

A system for the direct determination of the nonvolatile organic carbon, dissolved organic carbon, and inorganic carbon in water samples through inductively coupled plasma atomic emission spectrometry

A new system has been developed for the determination of total organic carbon (TOC) and inorganic carbon (IC) or total inorganic carbon (TIC) in waters. Only nonvolatile organic compounds can be detected through the present method. The system presented in this work is based on the measurement of the carbon atomic emission intensity in inductively coupled plasma atomic emission spectrometry (ICP-AES). This way, the organic matter does not undergo any preoxidation step. A semiautomatic accessory connected to the spectrometer separates the different carbon fractions (i.e., organic and inorganic). Because most of the solutions used in the present work did not contain suspended solid particles, the actual parameter that was determined was the dissolved organic carbon (DOC). The present system exhibits good sensitivities compared to those provided by conventional TOC and IC determination methods. The limits of detection obtained in the present work have been 0.07 and 0.0007 mg/L C in terms of TOC and IC, respectively. Furthermore, the system is able to handle high-salt-content solutions. This fact suggests that it would be possible to analyze seawater samples, avoiding some of the problems encountered with conventional methods, such as system blocking or interferences. The TOC and IC values found for natural samples are very close to those measured using conventional methods. The ICP-AES method has been successfully used in two interesting applications: (i) monitoring the efficiency of a water treatment plant and (ii) determining the contents of dissolved carbon dioxide, on one hand, and that of carbonate and bicarbonate, on the other, in the same sample.

The role of colloidal particles in the speciation and analysis of "dissolved" phosphorus

Colloidal-sized particles (1-1,000 nm) and high molecular mass material play an important, yet poorly understood role in the aqueous speciation of P. This study assessed the size distribution of P in 0.45-microm filtered soil solutions and soil-water extracts from three sandy soils (grassland, arable field and forest) using gel filtration chromatography (GFC) and membrane filtration (0.22- and 0.025-microm pore-size) and evaluated the impact of P speciation on colorimetric and ion-chromatographic methods for orthophosphate analysis. Between 40% and 58% of molybdate reactive P (MRP) and > 85% of molybdate unreactive P in the soil solution from the agricultural soils (pH 5.9-6.3) were associated with high molecular mass material (apparent size > 0.025 microm, or > 600 kDa on Superdex). In solutions from the forest soil (pH 3.2), high molecular mass P (HMMP) compounds were of minor importance (<8% of TP). The GFC elution profiles, composition and spectral characteristics of HMMP-containing solutions as well as the small relevance of HMMP at low pH were all indicative for associations between humic substances, Fe and/or Al, and P. Both MRP and ion chromatographic P measurements overestimated the free orthophosphate concentration (up to 2.3- and 1.4-fold, respectively) in 0.45-microm filtered HMMP-containing solutions. In 0.025-microm filtrates, free orthophosphate was the only MRP species present.

Electrospray ionization fourier transform ion cyclotron resonance mass spectrometry of dissolved organic phosphorus species in a treatment wetland after selective isolation and concentration

A method for the selective concentration of dissolved organic phosphorus (DOP) from complex surface water samples for the first time allows mass spectral characterization of individual DOP compounds in phosphorus-limited ecosystems. The entire dissolved organic matter (DOM) pool is first separated according to molecular weight by tangential cross-flow ultrafiltration (CFF). DOP is selectively isolated and concentrated from CFF fractions by a barium precipitation procedure. The DOP precipitate is then reconstituted in distilled water and excess barium, and other cations are removed with an ion-exchange resin. The DOP isolation/concentration step can provide up to 15-fold concentration and 300-fold concentration of high molecular weight DOP when combined with the inherent concentration provided by CFF. The procedure also removes cations and most of the background DOM, leaving DOP in a matrix suitable for electrospray ionization and mass spectral characterization. Model organic phosphate standards representative of DOP species expected in aquatic environments were used to evaluate the technique. It was then applied to a series of high molecular weight (>1000) CFF retentates isolated from sites within the Everglades Nutrient Removal (ENR) treatment wetland. The elemental compositions of several individual DOP compounds observed at different sites within the ENR were determined by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry.

Determination of phosphorus based on the formation of a reduced keggin-type 12-molybdophosphate complex in an aqueous-organic solution

A very simple, easy and sensitive spectrophotometric manual determination method of phosphorus for the P04(3-) ion, based on the formation of the reduced 12-molybdophosphate complex, was developed. The effect of the kind of water-miscible organic solvent and the concentration of organic solvent, ascorbic acid and HCl on the formation of the complex was investigated. The optimum determination condition was confirmed based on these results. In an aqueous-CH3CN solution, a P-PO4(3-) of 0.01-20 mg l(-1) could thus be determined. It was noted that the determination range of this study was wider than that of the phosphoantimonylmolybdenum blue method (0.032-1 mg l(-1)). The effect of foreign ions on the absorbance was examined. The P-PO4(3-) in river water and seawater sampled in Kochi was determined by this method. The results were also compared with those of the phosphoantimonylmolybdenum blue method and capillary electrophoresis with an indirect detection method using K2CrO4.