Multielement analysis in the fish hepatic cytosol as a screening tool in the monitoring of natural waters

The possibility of direct measurement of trace elements in hepatic cytosol of European chub (Squalius cephalus) by high-resolution inductively coupled plasma mass spectrometry (HR ICP-MS) after cytosol dilution with Milli-Q water and subsequent acidification was investigated. Due to low detection limits of this procedure, determination of 13 elements (As, Cd, Co, Cu, Fe, Mn, Mo, Pb, Sb, Sn, Sr, V and Zn) was possible in the chub hepatic cytosol, exhibiting excellent measurement repeatability in duplicates. Some of these elements were also measured by HR ICP-MS in acid digested cytosols (Cd, Co, Cu, Fe, Mn, Mo, Sr, V and Zn). Good agreement of the results obtained after sample dilution and sample digestion indicated that complex organic matrix of hepatic cytosol did not affect measurement reliability. Cytosolic concentrations of 13 trace elements in the chub liver were quantified in the following order: Fe, Zn>Cu>Mn>Mo>Sr, V, Cd>Co>As, Pb>Sn>Sb. Unlike Cd, Cu, Fe, Mn and Zn for which the cytosolic concentrations were previously reported after measurement by AAS, cytosolic concentrations of eight additional trace elements characteristic for the liver of chubs inhabiting the low contaminated river water were reported here for the first time (in nanogrammes per gramme)—Mo, 136.8–183.6; Sr, 32.7–63.0; V, 17.5–69.0; Co, 24.3–30.7; As, 9.9–29.5; Pb, 5.8–35.6; Sn, 5.5–12.4; and Sb, 0.9–2.6. The simultaneous measurement of large number of trace elements in the cytosolic fractions of fish tissues, which comprise potentially metal-sensitive sub-cellular pools, could be beneficial as a screening tool in the monitoring of natural waters, because it would enable timely recognition of increased fish exposure to metals.     

Noise tolerance of algorithms for estimating chlorophyll a concentration in turbid waters

The accuracy and noise tolerance of 13 global models and 5 Case II chlorophyll a (chl a) retrieval models were evaluated using three dataset. It was found that if 5 % input noise related to atmospheric correction is considered, then the uncertainty associated with noise tolerance varied from 5.5 % to 55.6 %, and these uncertainties generally accounts for 15.63 % to 24.75 % of the total uncertainty. This observation suggests that an optimal algorithm not only should have a strong chl a concentration prediction ability but also should possess high insensitivity to the noise of remote-sensing imagery. The accuracy evaluations of chl a models were based on comparisons of chl a predicted models with chl a concentration measured analytically for field measurements. The results indicate that none of the selected chl a estimation algorithms provide accurate retrievals of chl a in turbid waters. This may be attributed to the strong optical influence of organic and inorganic matter at the blue green range, and the non-negligible of non-organic matter absorption at the red and near-infrared ranges. In order to solve this problem, the chl a concentration retrieval models must be further optimized. After being optimized using the empirical optimized method constructed in this paper, a single parameterized NDCI (normalized difference chl a index) model produces accurate retrievals in the Yellow River Estuary, Taihu Lake and Chesapeake Bay. If 5 % input noise associated with residual uncertainty 0of atmospheric correction is taken into account, the model produces only 29.96 % uncertainty for the remote sensing of chl a concentration in these three turbid waters.     

Recent trends of plutonium fallout observed in Japan: plutonium as a proxy for desertification

Plutonium in monthly deposition samples collected in Tsukuba (the Meteorological Research Institute), Japan from 1990 to end of 2001 is reported, together with monthly plutonium deposition in Nagasaki and Yonaguni in 2000. The annual deposition of (239,240)Pu during the period from 1990 to 2001 shows no systematic interannual variation. However, monthly (239,240)Pu depositions show a typical seasonal variation with a maximum in spring season (March to April), which corresponds to seasonal cycle of soil dusts originating from the East Asian arid area. Plutonium isotopic ratios in the deposition samples suggest that significant amounts of the recent (239,240)Pu deposition observed in Japan are attributed to the resuspension of plutonium-bearing surface soil particles; resuspended plutonium originates from the East Asian arid areas. The recent increased tendency of (239,240)Pu content in residues in deposition samples may reflect desertification in the East Asian continent.     

The development of a chemical 'fingerprint' to characterise dissolved organic matter in natural waters

A suite of twelve assays has been used to 'fingerprint' dissolved organic matter (DOM). The assays were applied directly to filtered natural water samples. Temperature, pH and conductivity accounted for the environmental conditions on-site. Bulk carbon characteristics were assayed by measuring UV absorbance at 200 and 240 nm, colour in grade Hazen, DOC (dissolved organic carbon), fluorescence (excitation 370 nm, emission 450 nm) and the complexation of phenol itself. Measuring hydroxybenzenes ('monophenolics'), polyhydroxybenzenes ('polyphenolics') and total phenolics with the Gibbs, Prussian Blue and Folin-Ciocalteau assays, respectively, determined the phenolics pool. The methodology was tested on six freshwater sites in North Wales chosen to provide differences in vegetation, land-use and water chemistry and sampled once during each season. A novel approach for the presentation of the data has been developed that combines all range normalised assay results for each site and each season within one polar plot, hence the term 'fingerprint'. The data was also analysed using principal component factor analysis. Assays characterised as determining the chemical properties of DOM contributed to Factor 1 and explained 59% of the variation in the data. Assays apparently determined by the water matrix, contributed to Factor 2 and explained 20% of the variation within the data. The factor scores obtained for each site showed more variation for assays relating to the chemical properties of DOM than to the surrounding water matrix. The methodology was found to detect chemical changes within DOM for each site throughout the year and different responses for different sites.     

Estimation of chlorophyll-a concentration using field spectral data: a case study in inland Case-II waters, North China

In the remote sensing of chlorophyll-a (Chla) in inland Case-II waters, the assumption that the optical parameter of Chla specific absorption coefficient a*ph remains constant usually restrains application of many models. In this paper, we presented a newly developed model [Rrs(-1)(lambda1) - Rrs(-1)(lambda2)] x Rrs(lambda3) x a*ph(-1)(lambda1) which was improved on a previous three-band model to isolate interferences from a*ph. In terms of the importance of water optical properties in the model development, spectral and absorption characteristics were analyzed for Shitoukoumen Reservoir and Songhua Lake in Northeast China, as typical examples of inland Case-II waters. Both waters showed overwhelming absorption sum of tripton and chromophoric dissolved organic matter (CDOM) owing to their relatively low Chla contents (1.53 to 19.35 microgl(-1)). According to the optical characteristics of waters studied, optimal positions for lambda (1), lambda (2) and lambda (3) were spectrally tuned to be at 664, 684 and 705 nm, respectively. The model allowed accurate Chla estimation with a determination coefficient (R (2)) close to 0.98 and a root mean square error (RMSE) of 0.87 microgl(-1). Comparison of different models further showed the stability of the improved model, implying its potential use in water color remote sensing. Although the findings underline the rationale behind the improved model, an extensive database containing data in different water conditions and water types is required to generalize its application.     

Beryllium natural background concentration and mobility: a reappraisal examining the case of high Be-bearing pyroclastic rocks

Beryllium is widely distributed in soils at low levels, but it can also occur naturally in higher concentrations in a variety of materials exploited for many industrial applications. Beryllium is also one of the most toxic natural elements and is known to be a human carcinogen. A concise account of the literature data on baseline concentrations of Be in soils illustrates the possibility of worldwide presence of areas with a high natural background concentration of Be (up to 300 mg/kg), the crustal abundance of which is generally estimated to be in the range 2–6 mg/kg. Nevertheless, the number of available data is rather limited in comparison with those about other toxic elements such as Pb, Cd and Cr. This has probably caused the choice of low values of concentration level as the reference for the definition of soil contamination: these values are not always realistic and are not applicable to large areas. As a case study, we report and analyse a diffuse, unusually high (up to 80 mg/kg, average approximately 20 mg/kg), natural occurrence of beryllium in loose and poorly consolidated pyroclastic layers related to the Pleistocene activity of the Vico volcano. Additionally, the analysis of Be leachability has been carried out, providing evidence of a not negligible mobility in contrast with the scarce data presented in the literature that usually indicate beryllium as an element with low mobility in oxidising surface environmental conditions. This research marks the beginning of a possible reappraisal of beryllium geochemical behaviour and background levels, providing more realistic reference values for risk assessment and land management.     

Ultracentrifugation as a direct method to concentrate viruses in environmental waters: virus-like particle enumeration as a new approach to determine the efficiency of recovery

Some health important enteric viruses are considered to be emerging waterborne pathogens and so the improvement of detection of these viruses in the aquatic environment is one of the most important steps in dealing with these pathogens. Since these viruses may be present in low numbers in water, it is necessary to concentrate water samples before viral detection. Although there are several methods to concentrate viruses in environmental waters, all present some drawbacks and consequently the method should be chosen that, despite its limitations, is adequate to achieve the aim of each study. As the effectiveness of the concentration methods is evaluated by determining the efficiency of viral recovery after concentration, it is important to use a simple and effective approach to evaluate their recovery efficiency. In this work ultracentrifugation, usually used as a secondary step for virus concentration, was evaluated as the main method to concentrate directly viruses in environmental water samples, using the microscopic enumeration of virus-like particles (VLP) as a new approach to estimate the efficiency of recovery. As the flocculation method is currently employed to concentrate viruses in environmental waters, it was also used in this study to assess the efficiency of the ultracentrifugation as the main viral concentration method in environmental waters. The results of this study indicate that ultracentrifugation is an adequate approach to concentrate viruses directly from environmental waters (recovery percentages between 66 and 72% in wastewaters and between 66 and 76% in recreational waters) and that the determination of VLP by epifluorescence microscopy is a simple, fast and cheap alternative approach to determine the recovery efficiency of the viral concentration methods.     

Characterization of dissolved organic carbon at low levels in environmental waters by microfluidic-chip-based capillary gel electrophoresis with a laser-induced fluorescence detector

A microfluidic analytical system for characterization of dissolved organic carbon (DOC) in environmental waters, based on a capillary gel electrophoresis (CGE) device with a laser-induced fluorescence (LEF) detector, was developed. The applied voltage and the running buffer were investigated to control the simple floating injection and CGE separation for convenient cross-type microchips made from polymethylmethacylate. We obtained reproducible peaks for standard organic solutions and the determination time is less than 70 s. The values of the relative standard deviation (RSD) were 0.17–2.01% for repetitive injection (n?=?12). We demonstrated high-throughput characterization of DOC in environmental water from the Biwa Lake and the Hino River using microfluidic chip and determined that the content of DOC in the Biwa Lake changed with the seasons.     

Iron-rich Oklahoma clays as a natural source of chromium in monitoring wells

Water samples, drawn from groundwater monitoring wells located southeast of Oklahoma City, OK, were found to contain elevated concentrations of total chromium with an apparent source localized to the area surrounding each well. Since these monitoring wells are located in areas with no historic chromium usage, industrial sources of chromium were ruled out. Water testing was performed on twelve monitoring wells in the area that historically had elevated total chromium concentrations ranging from 10-4900 micrograms per litre. Filtered water samples were found to be free of chromium contamination, indicating that the source of the chromium is the suspended solids. Analysis of these solids by acid digestion and a sequential extraction technique revealed that the chromium was primarily associated with iron-containing solids. X-ray diffraction identified goethite, an iron oxide hydroxide, as the dominant iron-containing phase in the suspended solids. The mineralogy in this region is dominated by interbedded red-bed sandstone and mudstone whose mineral content includes mixed-layer illite-smectite, hematite, goethite, gypsum and dolomite. Elemental analysis of soil samples collected as a function of depth in the locale of the monitoring wells indicated that the iron rich clays contain a natural source of chromium. The elevated levels of total chromium are most likely due to the dissolution of silica and alumina from the chromium containing iron clays in the basic well water, resulting in the release of fine suspended solids that naturally have high chromium concentrations. These results should be applicable to other areas containing iron-rich clays.     

Natural forest regrowth as a proxy variable for agricultural land abandonment in the Swiss mountains: a spatial statistical model based on geophysical and socio-economic variables

In many European mountain regions, natural forest regrowth on abandoned agricultural land and the related consequences for the environment are issues of increasing concern. We developed a spatial statistical model based on multiple geophysical and socio-economic variables to investigate the pattern of natural forest regrowth in the Swiss mountain area between the 1980s and 1990s. Results show that forest regrowth occurred primarily in areas with low temperature sum, intermediate steepness and soil stoniness as well as close to forest edges and relatively close to roads. Model results suggest that regions with weak labor markets are favored in terms of land abandonment and forest regrowth. We could not find an effect of population change on land abandonment and forest regrowth. Therefore, we conclude that decision makers should consider non-linearities in the pattern of forest regrowth and the fact that labor markets have an effect on land abandonment and forest regrowth when designing measures to prevent agricultural land abandonment and natural forest regrowth in the Swiss mountains.     

On-line solid phase extraction with polyurethane foam: trace level spectrophotometric determination of iron in natural waters and biological materials

This paper reports the development of a simple and accurate on-line procedure for preconcentration and determination of dissolved iron in waters and biological materials using unloaded polyether-type polyurethane foam as solid extractor. In the developed flow injection system, the analyte was preconcentrated from acidic aqueous medium as iron-thiocyanate complex with post-elution with ascorbic acid solution and spectrophotometric measurement with 1,10-phenanthroline as colorimetric reagent. In order to improve the performance of the system several chemical and flow variables were investigated as well as the effect caused by the presence of possible interferents. The method was validated by the analysis of two certified reference materials. Application of the methodology was carried out by the determination of dissolved iron content in eight natural water samples with different characteristics. The results were compared with those obtained by electrothermal atomic absorption spectrometry (ETAAS) and no statistical difference was observed. The detection limit was 0.75 microgram l-1 and the RSD was 1.2% for 2 min preconcentration time. At this condition, a productivity of 20 samples h-1 was achieved. Increasing the preconcentration time up to 3 min, a detection limit of 0.45 microgram l-1, an RSD of 1.5% and an analytical throughput of 15 h-1 were verified.     

FIA-coupled spectrophotometric method for determination of Cr (VI) traces in natural waters: application of in-line dissolution of 1,5-diphenylcarbazide after heat treatment and activated alumina as adsorbent for preconcentration

This work proposes the quantification of Cr (VI) ions in natural waters in trace level, using activated alumina (Al₂O₃) as preconcentration support, controlled in-line dissolution of the solidified chromophore diphenylcarbazide after heat treatment and spectrophotometric detection. The manifold ensures high sensitivity of analytical response, good repeatability, and stability. In this work, optimization of experimental conditions of a flow injection system was chosen as the parameters for greater sensitivity and better selectivity. The selected optimized conditions were 0.30 mol L^?1 for H₂SO₄ concentration, system flow rate as 0.40 mL min^?1, sample injection volume of 192.50 μL, 2 min for preconcentration time, and 0.10 mol L^?1 for eluent concentration. The analytical curves obtained for real sample analysis show linear range from 0.192 to 0.961 μM, linear correlation coefficient R?=?0.9997 and LOD?=?0.024 μM. The preconcentration factor of about four times was obtained through the passage of 800 μL of a standard solution containing 0.961 μM of Cr (VI) through mini-column of preconcentration followed by elution at 192.5 μL of NH₄OH 0.1 mol L^?1 solution. The solid chromogenic reagent presented high durability (weeks in daily use with mass of 0.0993 g) and good reproducibility in analytical signal. The reactivation of the mini-column of alumina should be executed after ten injections of eluent, using 800 μL of HCl 0.02 mol L^?1 solution in flow through the same. Each cycle of injection and elution of the sample takes about 5 min on the proposed terms. Despite the length of each cycle still be high, low concentrations can be detected using a technique of relatively low cost. This is due in part, the association dissolution of the chromogenic reagent directly in the line and the preconcentration step. Another important factor is the economy of reagent chromogenic, low generation of reject contributing to better quality of the environment, and the high potential for applications to work in field.     

Probabilistic risk assessment of insecticide concentrations in agricultural surface waters: a critical appraisal

Due to the specific modes of action and application patterns of agricultural insecticides, the insecticide exposure of agricultural surface waters is characterized by infrequent and short-term insecticide concentration peaks of high ecotoxicological relevance with implications for both monitoring and risk assessment. Here, we apply several fixed-interval strategies and an event-based sampling strategy to two generalized and two realistic insecticide exposure patterns for typical agricultural streams derived from FOCUS exposure modeling using Monte Carlo simulations. Sampling based on regular intervals was found to be inadequate for the detection of transient insecticide concentrations, whereas event-triggered sampling successfully detected all exposure incidences at substantially lower analytical costs. Our study proves that probabilistic risk assessment (PRA) concepts in their present forms are not appropriate for a thorough evaluation of insecticide exposure. Despite claims that the PRA approach uses all available data to assess exposure and enhances risk assessment realism, we demonstrate that this concept is severely biased by the amount of insecticide concentrations below detection limits and therefore by the sampling designs. Moreover, actual insecticide exposure is of almost no relevance for PRA threshold level exceedance frequencies and consequential risk assessment outcomes. Therefore, we propose a concept that features a field-relevant ecological risk analysis of agricultural insecticide surface water exposure. Our study quantifies for the first time the environmental and economic consequences of inappropriate monitoring and risk assessment concepts used for the evaluation of short-term peak surface water pollutants such as insecticides.     

Macroalgae and DGT as indicators of available trace metals in marine coastal waters near a lead–zinc smelter

The levels of Cd, Cu, Pb, and Zn were determined in the commonest species of green, red, and brown algae collected from five coastal sites in south-western Sardinia (Italy), an area with a long history of mining and smelting. The usefulness of employing Enteromorpha sp. and Padina pavonica (L.) Thivy to monitor metal pollution was evaluated, while diffusive gradients in thin films (DGT) devices were used to measure dissolved metals in seawater. Levels of Cd and Pb were high enough to be of environmental concern in the whole study area. A significant relationship was found between the content of Pb in P. pavonica and DGT-labile Pb in seawater, suggesting that gross elemental concentrations of nonessential metals such as Pb in algal tissues are apparently controlled by the abundance of dissolved metal species in the ambient seawater. The results pointed out the usefulness of using both DGT and algal methods for a better understanding of trace metal availability in coastal waters.     

Characteristics of nutrients in natural wetland in winter: a case study

The transformation, composition, and distribution characteristics of nutrients in natural wetlands are significantly affected by human activities, such as large-scale water conservancy projects and agricultural activities. It is necessary to reveal the composing and distribution characteristics of nutrients for elucidating its complex removal and retention mechanisms in natural wetlands. In this study, the composition and the spatial distribution characteristics of nitrogen in a natural wetland in central China were illustrated and analyzed. The self-organizing map (SOM) model was used in this study to assess the water quality dataset of the wetland. The relationships between nitrogen and other water quality parameters were revealed by the visualization function of the SOM model with the pre-processed data; the modeling result was in agreement with the linear correlation analysis. The results indicated that the SOM model was suitable for the assessment of field-scale date of natural wetlands, and finally a potential approach for predicting the nutrients concentrations in natural wetlands was also found.     

Occurrence and behaviour of dissolved, nano-particulate and micro-particulate iron in waste waters and treatment systems: new insights from electrochemical analysis

Cyclic-, Differential Pulse- and Steady-state Microdisc Voltammetry (CV, DPV, SMV) techniques have been used to quantify the occurrence and fate of dissolved Fe(ii)/Fe(iii), nano-particulate and micro-particulate iron over a 12 month period in a series of net-acidic and net-alkaline coal mine drainages and passive treatment systems. Total iron in the mine waters is typically 10-100 mg L(-1), with values up to 2100 mg L(-1). Between 30 and 80% of the total iron occurs as solid phase, of which 20 to 80% is nano-particulate. Nano-particulate iron comprises 20 to 70% of the nominally "dissolved" (i.e. <0.45 μm) iron. Since coagulation and sedimentation are the only processes required to remove solid phase iron, these data have important implications for the generation or consumption of acidity during water treatment. In most waters, the majority of truly dissolved iron occurs as Fe(ii) (average 64 ± 22%). Activities of Fe(ii) do not correlate with pH and geochemical modelling shows that no Fe(ii) mineral is supersaturated. Removal of Fe(ii) must proceed via oxidation and hydrolysis. Except in waters with pH < 4.4, activities of Fe(iii) are strongly and negatively correlated with pH. Geochemical modelling suggests that the activity of Fe(iii) is controlled by the solubility of hydrous ferric oxides and oxyhydroxysulfates, supported by scanning and transmission electron microscopic analysis of solids. Nevertheless, the waters are generally supersaturated with respect to ferrihydrite and schwertmannite, and are not at redox equilibrium, indicating the key role of oxidation and hydrolysis kinetics on water treatment. Typically 70-100% of iron is retained in the treatment systems. Oxidation, hydrolysis, precipitation, coagulation and sedimentation occur in all treatment systems and - independent of water chemistry and the type of treatment system - hydroxides and oxyhydroxysulfates are the main iron sinks. The electrochemical data thus reveal the rationale for incomplete iron retention in individual systems and can thus inform future design criteria. The successful application of this low cost and rapid electrochemical method demonstrates its significant potential for real-time, on-site monitoring of iron-enriched waters and may in future substitute traditional analytical methods.     

Enteromorpha flexuosa (Wulfen) J. Agardh (Chlorophyta: Ulvales)--evaluation as an indicator of heavy metal contamination in a tropical estuary

The use of bioindicators for contaminant monitoring ispopular in all sectors of the environment but quite oftenbioindicators are utilised without rigorous evaluation oftheir viability as an indicator. We report field andlaboratory investigations into the value of a commonlyfound macroalga, Enteromorpha flexuosa (Wulfen) J.Agardh (Chlorophyta: Ulvales) as an indicator of copper,zinc and lead contamination in a tropical estuary inFiji. In the laboratory, metal content of E.flexuosa after 60 days of growth in seawater containingincreasing concentrations of the metals showed almostperfect correlation with metal concentrations in waterfor all three metals, and concentration factors obtainedwere generally higher than values reported for otherspecies of Enteromorpha. Performance in the fieldwas evaluated by a one-year monitoring of metals in E. flexuosa, water and sediments from a contaminatedestuary. Metal concentrations in water were always belowdetection limits and field concentration factors couldnot be determined but the concentration of lead in E. flexuosa showed a high correlation with the leadcontent of sediments. Lack of such correlation forcopper and zinc in the field suggests that otherenvironmental factors besides metal load in the physicalenvironment could be controlling the bioaccumulation ofthese two metals. Whilst demonstrating E. flexuosato be a viable bioindicator for lead, these results alsohighlight the need for proper assessment before anorganism is considered for environmental monitoring.