New device and method for flux-proportional sampling of mobile solutes in soil and groundwater

Comparative field study on bioassay responses and micropollutant uptake of POCIS, Speedisk and SorbiCell polar passive samplers

Routine water quality monitoring is generally performed with chemical analyses of grab samples, which has major limitations. First, snapshot samples will not give a good representation of the water quality. Second, it is not sufficient to analyze only a limited number of (priority) pollutants. These limitations can be circumvented by an alternative environmental risk assessment that combines time-integrated passive sampling (PS) with effect-based methods. This study aimed to select which of three polar PS devices was best suited for effect-based monitoring strategies. In the first part of this study, Speedisk, SorbiCell and POCIS polar PS devices were compared by simultaneous deployment at five sites. Chemical analyses of 108 moderately polar compounds (-1.82 < log D < 6.28) revealed that highest number of compounds, with the widest range of log K_OW, log D and pKa, were detected in extracts of POCIS, followed by Speedisk. SorbiCell samplers accumulated the lowest numbers and concentrations of compounds, so they were not further investigated. In a follow-up study, bioassay responses were compared in extracts of POCIS and Speedisk devices deployed at eight sites. The passive sampler extracts were subjected to bioassays for non-specific toxicity, endocrine disruption, and antibiotics activities. More frequent and higher responses were induced by POCIS extracts, leading to more exceedances of effect-based trigger values for environmental risks. As POCIS outperformed Speedisk, it is better suited as PS device targeting polar compounds for semi-quantitative effect-based water quality monitoring.

Bioaccumulation of Fluorotelomer Sulfonates and Perfluoroalkyl Acids in Marine Organisms Living in Aqueous Film-Forming Foam Impacted Waters

The use of aqueous film-forming foams (AFFFs) has resulted in hot spots polluted with poly- and perfluorinated alkyl substances (PFASs). The phase out of long-chained perfluoroalkyl acids (PFAAs) from AFFFs resulted in the necessity for alternatives, and short-chained PFAAs and fluorotelomer-based surfactants have been used. Here, the distribution of PFAS contamination in the marine environment surrounding a military site in Norway was investigated. Up to 30 PFASs were analyzed in storm, leachate, and fjord water; marine sediments; marine invertebrates (snails, green shore crab, great spider crab, and edible crab); and teleost fish (Atlantic cod, European place, and Lemon sole). Perfluorooctanesulfonic acid (PFOS) was the most abundantly detected PFAS. Differences in PFAS accumulation levels were observed among species, likely reflecting different exposure routes among trophic levels and different capabilities for depuration and/or enzymatic degradation. In agreement with previous literature, almost no 6:2 fluorotelomer sulfonate (6:2 FTS) was detected in teleost fish. However, this study is one of the first to report considerable concentrations of 6:2 FTS in marine invertebrates, suggesting bioaccumulation. Biota monitoring and risk assessments of sites contaminated with fluorotelomer sulfonates (FTSs) and related compounds should not be limited to fish, but should also include invertebrates.

Methods for Sample Collection, Storage, and Analysis of Freshwater Phosphorus

Although phosphorus (P) is an essential nutrient for biological productivity, it can cause freshwater degradation when present at fairly low concentrations. Monitoring studies using continuous sampling is crucial for documenting P dynamics in freshwater ecosystems and to reduce the risk of eutrophication. Despite literature updates of developments of the analytical methods for measurement of P species in natural waters, there has been no comprehensive review addressing freshwater sample collection, sample preparation, and sample treatment to fractionate and characterize different forms of P. Therefore, this paper aims to elaborate the different techniques for freshwater sampling and to introduce alternative laboratory methods for sample preservation and P fractionation. The advantages and disadvantages of various sampling techniques, including the traditional manual and the recently developed automatic and passive methods, are presented to highlight the importance of collecting representative freshwater samples. Furthermore, we provide suggestions for sample pretreatment, including filtration, transportation, and storage steps to minimize microbial activity and to maximize the accuracy of measurement of various P fractions. Finally, the most common laboratory methods to measure dissolved and particulate as well as the organic and inorganic freshwater P fractions are efficiently provided. Using this guide, a comprehensive monitoring program of P dynamics in freshwater ecosystems can be developed and applied to improve water quality, particularly of P-rich freshwaters.

Feasibility of developing a passive sampler for sampling heavy metals in BMPs for stormwater runoff management

Structural Best Management Practices (BMPs) have been used for stormwater treatment and management for several decades. How to monitor these BMPs performance reliably and economically is a challenge. This paper reports the feasibility of developing a flow through passive sampler (PS) based on Amberlite IRC748 ion exchange resin operated in kinetic regime for sampling heavy metals in BMPs (infiltration systems) for stormwater treatment and management. Tests were conducted using batch reactors and laboratory-scale BMPs. Batch reactor results indicate that PSs performed desirably with consistent and rapid metal uptake, and thus, the resin-based PS is feasible to be used for stormwater sampling. In lab-scale BMPs tests, the resin PSs were employed for sampling influent and effluent of BMPs loaded with synthetic stormwater for storm durations of 0.5, 3, and 12 hours. The removal efficiency of heavy metals in the BMPs as predicted by PSs was very similar to the actual treatment efficiencies obtained from control BMPs, with errors ranging from -5% to 2%, indicating that the PSs can be used for sampling stormwater and monitoring BMPs. The next step for this sampler will be to develop a method for evaluating the volume of water passing the PS during the sampling period.

TIMFIE Sampler-A New Time-Integrating, Active, Low-Tech Sampling Device for Quantitative Monitoring of Pesticides in Whole Water

The need for inexpensive, time-averaged, quantitative determination of pesticides and other organic pollutants in whole water is not matched by the field sampling procedures available. Our new Time-Integrating, MicroFlow, In-line Extraction (TIMFIE) sampler comprises a low-tech syringe pump driven by a rubber band and connected to a flow restrictor enabling low microliter per minute water flow through a solid phase extraction (SPE) cartridge. This allows target compounds to be continuously extracted in the field over 1 week. The extracted water ends up in the syringe, where sample volume is accurately determined. TIMFIE followed by online SPE-LC-MS/MS determination was validated for 72 selected pesticides, and, except for three compounds, detection limit was 0.1-1 ng/L. In a field study, concentrations in TIMFIE samples and in grab samples were compared. Following TIMFIE sampling, on average 19 pesticides per sample were quantified, compared with nine pesticides per sample with grab sampling, as a result of the extra in-field concentration step. Duplicate TIMFIE sampling showed Pearson's correlation coefficient r = 0.998. Comparing concentrations from TIMFIE sampling to grab sampling resulted in ratios between 0.05 and 16.5 (mean 1.7; r = 0.532), demonstrating a discrepancy between the two sampling strategies and possible underestimation of chronic exposure by grab sampling.

Expanded Application of the Passive Flux Meter: In-Situ Measurements of 1,4-Dioxane, Sulfate, Cr(VI) and RDX

Passive flux meters (PFMs) have become invaluable tools for site characterization and evaluation of remediation performance at groundwater contaminated sites. To date, PFMs technology has been demonstrated in the field to measure midrange hydrophobic contaminants (e.g., chlorinated ethenes, fuel hydrocarbons, perchlorate) and inorganic ions (e.g., uranium and nitrate). However, flux measurements of low partitioning contaminants (e.g., 1,4-dioxane, hexahydro-1,3,5-trinitro-s-triazine (RDX)) and reactive ions-species (e.g., sulfate (SO42−), Chromium(VI) (Cr(VI)) are still challenging because of their low retardation during transport and quick transformation under highly reducing conditions, respectively. This study is the first application of PFMs for in-situ mass flux measurements of 1,4-dioxane, RDX, Cr(VI) and SO42− reduction rates. Laboratory experiments were performed to model kinetic uptake rates and extraction efficiency for sorbent selections. Silver impregnated granular activated carbon (GAC) was selected for the capture of 1,4-dioxane and RDX, whereas Purolite 300A (Bala Cynwyd, PA, USA) was selected for Cr(VI) and SO42−. PFM field demonstrations measured 1,4-dioxane fluxes ranging from 13.3 to 55.9 mg/m2/day, an RDX flux of 4.9 mg/m2/day, Cr(VI) fluxes ranging from 2.3 to 2.8 mg/m2/day and SO42− consumption rates ranging from 20 to 100 mg/L/day. This data suggests other low-partitioning contaminates and reactive ion-species could be monitored using the PFM.

Continuous 'Passive' flow-proportional monitoring of drainage using a new modified Sutro weir (MSW) unit

In view of their crucial role in water and solute transport, enhanced monitoring of agricultural subsurface drain tile systems is important for adequate water quality management. However, existing monitoring techniques for flow and contaminant loads from tile drains are expensive and labour intensive. The aim of this study was to develop a cost-effective and simple method for monitoring loads from tile drains. The Flowcap is a modified Sutro weir (MSW) unit that can be attached to the outlet of tile drains. It is capable of registering total flow, contaminant loads and flow-averaged concentrations. The MSW builds on a modern passive sampling technique that responds to hydraulic pressure and measures average concentrations over time (days to months) for various substances. Mounting the samplers in the MSW allowed a flow-proportional part of the drainage to be sampled. Laboratory testing yielded high linear correlation between the accumulated sampler flow, q total, and accumulated drainage flow, Q total (r (2) > 0.96). The slope of these correlations was used to calculate the total drainage discharge from the sampled volume, and therefore contaminant load. A calibration of the MSW under controlled laboratory condition was needed before interpretation of the monitoring results was possible. The MSW does not require a shed, electricity, or maintenance. This enables large-scale monitoring of contaminant loads via tile drains, which can improve contaminant transport models and yield valuable information for the selection and evaluation of mitigation options to improve water quality. Results from this type of monitoring can provide data for the evaluation and optimisation of best management practices in agriculture in order to produce the highest yield without water quality and recipient surface waters being compromised.

New device for time-averaged measurement of volatile organic compounds (VOCs)

Contamination by volatile organic compounds (VOCs) in the environment is an increasing concern since these compounds are harmful to ecosystems and even to human health. Actually, many of them are considered toxic and/or carcinogenic. The main sources of pollution come from very diffuse focal points such as industrial discharges, urban water and accidental spills as these compounds may be present in many products and processes (i.e., paints, fuels, petroleum products, raw materials, solvents, etc.) making their control difficult. The presence of these compounds in groundwater, influenced by discharges, leachate or effluents of WWTPs is especially problematic. In recent years, law has been increasingly restrictive with the emissions of these compounds. From an environmental point of view, the European Water Framework Directive (2000/60/EC) sets out some VOCs as priority substances. This binding directive sets guidelines to control compounds such as benzene, chloroform, and carbon tetrachloride to be at a very low level of concentration and with a very high frequency of analysis. The presence of VOCs in the various effluents is often highly variable and discontinuous since it depends on the variability of the sources of contamination. Therefore, in order to have complete information of the presence of these contaminants and to effectively take preventive measures, it is important to continuously control, requiring the development of new devices which obtain average concentrations over time. As of today, due to technical limitations, there are no devices on the market that allow continuous sampling of these compounds in an efficient way and to facilitate sufficient detection limits to meet the legal requirements which are capable of detecting very sporadic and of short duration discharges. LABAQUA has developed a device which consists of a small peristaltic pump controlled by an electronic board that governs its operation by pre-programming. A constant flow passes through a glass cell containing adsorbent material where the VOCs are retained. The adsorbent used, made in LABAQUA, is a mixture of alginic acid and activated carbon. Due to its high permeability it allows the passage and retention of THMs in a suitable way, thus solving many of the problems of other common adsorbents. Also, to avoid degradation of the adsorbent, it is wrapped in a low density polyethylene (LDPE) membrane. After a sampling period of between 1 and 14 days, the adsorbent is collected and analyzed in the laboratory to quantify the VOC average concentration. This device resolves some of the limitations of the classical sampling system (spot samples), since we will take into account the fluctuations in the concentration of VOCs by averaging the same over time. This study presents the results obtained by the device for quantifying the VOCs legislated in the Directive 2000/60/EC. We present the validation of linearity over time and the limits of quantification, as well as the results of sample rate (Rs) obtained for each compound. The results demonstrate the high robustness and high sensitivity of the device. In addition the system has been validated in real waste water samples, comparing the results obtained with this device with the values of classical spot sampling, obtaining excellent results.

Velocity dependent passive sampling for monitoring of micropollutants in dynamic stormwater discharges

Micropollutant monitoring in stormwater discharges is challenging because of the diversity of sources and thus large number of pollutants found in stormwater. This is further complicated by the dynamics in runoff flows and the large number of discharge points. Most passive samplers are nonideal for sampling such systems because they sample in a time-integrative manner. This paper reports test of a flow-through passive sampler, deployed in stormwater runoff at the outlet of a residential-industrial catchment. Momentum from the water velocity during runoff events created flow through the sampler resulting in velocity dependent sampling. This approach enables the integrative sampling of stormwater runoff during periods of weeks to months while weighting actual runoff events higher than no flow periods. Results were comparable to results from volume-proportional samples and results obtained from using a dynamic stormwater quality model (DSQM). The paper illustrates how velocity-dependent flow-through passive sampling may revolutionize the way stormwater discharges are monitored. It also opens the possibility to monitor a larger range of discharge sites over longer time periods instead of focusing on single sites and single events, and it shows how this may be combined with DSQMs to interpret results and estimate loads over extended time periods.

Field and laboratory tests of flow-proportional passive samplers for determining average phosphorus and nitrogen concentration in rivers

Flow responsive passive samplers offer considerable potential in nutrient monitoring in catchments; bridging the gap between the intermittency of grab sampling and the high cost of automated monitoring systems. A commercially available passive sampler was evaluated in a number of river systems encapsulating a gradient in storm response, combinations of diffuse and point source pressures, and levels of phosphorus and nitrogen concentrations. Phosphorus and nitrogen are sequestered to a resin matrix in a permeable cartridge positioned in line with streamflow. A salt tracer dissolves in proportion to advective flow through the cartridge. Multiple deployments of different cartridge types were undertaken and the recovery of P and N compared with the flow-weighted mean concentration (FWMC) from high-resolution bank-side analysers at each site. Results from the passive samplers were variable and largely underestimated the FWMC derived from the bank-side analysers. Laboratory tests using ambient river samples indicated good replication of advective throughflow using pumped water, although this appeared not to be a good analogue of river conditions where flow divergence was possible. Laboratory tests also showed good nutrient retention but not elution and these issues appeared to combine to limit the utility in ambient river systems at the small catchment scale.

Bottom sediment as a source of organic contaminants in Lake Mead, Nevada, USA

Treated wastewater effluent from Las Vegas, Nevada and surrounding communities' flow through Las Vegas Wash (LVW) into the Lake Mead National Recreational Area at Las Vegas Bay (LVB). Lake sediment is a likely sink for many hydrophobic synthetic organic compounds (SOCs); however, partitioning between the sediment and the overlying water could result in the sediment acting as a secondary contaminant source. Locating the chemical plumes may be important to understanding possible chemical stressors to aquatic organisms. Passive sampling devices (SPMDs and POCIS) were suspended in LVB at depths of 3.0, 4.7, and 6.7 (lake bottom) meters in June of 2008 to determine the vertical distribution of SOCs in the water column. A custom sediment probe was used to also bury the samplers in the sediment at depths of 0-10, 10-20, and 20-30cm. The greatest number of detections in samplers buried in the sediment was at the 0-10cm depth. Concentrations of many hydrophobic SOCs were twice as high at the sediment-water interface than in the mid and upper water column. Many SOCs related to wastewater effluents, including fragrances, insect repellants, sun block agents, and phosphate flame retardants, were found at highest concentrations in the middle and upper water column. There was evidence to suggest that the water infiltrated into the sediment had a different chemical composition than the rest of the water column and could be a potential risk exposure to bottom-dwelling aquatic organisms.

The performance of passive flow monitors and phosphate accumulating passive samplers when exposed to pulses in external water flow rate and/or external phosphate concentrations

Passive samplers are typically calibrated under constant flow and concentration conditions. This study assessed whether concentration and/or flow pulses could be integrated using a phosphate passive sampler (P-sampler). Assessment involved three 21-day experiments featuring a pulse in flow rate, a pulse of filterable reactive phosphate (FRP) concentration and a simultaneous concentration and flow pulse. FRP concentrations were also determined by parallel grab sampling and the P-sampler calibrated with passive flow monitors (PFMs) and direct measurement of flow rates. The mass lost from the PFM over the deployment periods predicted water velocity to within 5.1, 0.48 and 7.1% when exposed to a flow rate pulse (7.5-50 cm s(-1)), concentration pulse (5-100 μg P L(-1)), or both simultaneously. For the P-sampler, good agreement was observed between the grab and passive measurements of FRP concentration when exposed to a pulse in flow (6% overestimation) or concentration (2% underestimation).

Method for the in situ calibration of a passive phosphate sampler in estuarine and marine waters

Passive samplers for phosphate were calibrated in the laboratory over a range of flow velocities (0-27 cm s(-1)) and ionic strengths (0-0.62 mol kg(-1)). The observed sampling rates were between 0.006 and 0.20 L d(-1). An empirical model allowed the estimation of these sampling rates with a precision of 8.5%. Passive flow monitors (PFMs), based on gypsum dissolution rates, were calibrated for the same range of flow velocities and ionic strength. Mass loss rates of the PFMs increased with increasing ionic strength. We demonstrate that this increase is quantitatively accounted for by the increased gypsum solubility at higher ionic strengths. We provide a calculation scheme for these solubilities for an environmentally relevant range of temperatures and salinities. The results imply that co-deployed PFMs can be used for estimating the flow effect on the in situ sampling rates of the phosphate samplers, and we expect that the same may hold for other passive samplers.

Model stream channel testing of a UV-transparent polymer-based passive sampler for ultra-low-cost water screening applications

Passive samplers are increasingly being considered for analyses of waters for screening applications, to monitor for the presence of unwanted chemical compounds. Passive samplers typically work by accumulating and concentrating chemicals from the surrounding water over time, allowing analyses to identify temporally short concentration surges that might be missed by water grab samples, and potentially reducing analysis and sample handling costs, allowing a greater number of sites to be monitored. The work described here tests a recently-developed passive sampling device which was designed to provide an ultra-low-cost screening method for organic chemicals in waters. The device was originally designed for detection of endocrine disrupting chemicals, but has the advantage that it is capable of simultaneously detecting a wide range of other aqueous organic contaminants as well. The device is based on a UV-transparent polymer which is used both to concentrate dissolved chemicals, and as an optical cell for absorbance detection and full-spectrum deconvolution to identify compounds. This paper describes the results of a test of the device conducted at the US EPA Experimental Stream Facility in Milford, Ohio. The test examined detection of triclosan and 4-nonylphenol in model stream channels using two different deployment methods. Results indicate that deployment method can significantly impact measured results due to differences in mass transfer. Passive samplers deployed in vials with permeable membrane septa showed no detection of either compound, likely due to lack of water motion in the vials. In contrast, passive samplers deployed directly in the flow were able to track concentrations of both compounds, and respond to temporal changes in concentration. The results of the work highlight the importance of using internal spiking standards (performance reference compounds) to avoid false non-detection results in passive sampler applications.

Application and evaluation of a new passive sampler for measuring average solute concentrations in a catchment scale water quality monitoring study

We present a field based testing, optimization, and evaluation study of the SorbiCell sampler (SC-sampler); a new passive sampling technique that measures average concentrations over longer periods of time (days to months) for various substances. We tested the SC-sampler within a catchment-scale monitoring study of NO(3) and P concentrations in surface water and tile drain effluent. Based on our field experiences, we optimized the flow velocity control and the sample volume capacity of the SC-samplers. The SC-samplers were capable of reproducing the NO(3) concentration levels and the seasonal patterns that were observed with weekly conventional grab sampling and continuous water quality measurements. Furthermore, we demonstrated that average measurements produce more consistent load estimates than "snapshot" concentrations from grab sampling. Therefore, when the purpose of a monitoring program is to estimate reliable (trends in) average concentrations or loads, the SC-samplers are a cost-effective alternative for grab sampling.

Influence of temporally variable groundwater flow conditions on point measurements and contaminant mass flux estimations

Monitoring of contaminant concentrations, e.g., for the estimation of mass discharge or contaminant degradation rates, often is based on point measurements at observation wells. In addition to the problem, that point measurements may not be spatially representative, a further complication may arise due to the temporal dynamics of groundwater flow, which may cause a concentration measurement to be not temporally representative. This paper presents results from a numerical modeling study focusing on temporal variations of the groundwater flow direction. "Measurements" are obtained from point information representing observation wells installed along control planes using different well frequencies and configurations. Results of the scenario simulations show that temporally variable flow conditions can lead to significant temporal fluctuations of the concentration and thus are a substantial source of uncertainty for point measurements. Temporal variation of point concentration measurements may be as high as the average concentration determined, especially near the plume fringe, even when assuming a homogeneous distribution of the hydraulic conductivity. If a heterogeneous hydraulic conductivity field is present, the concentration variability due to a fluctuating groundwater flow direction varies significantly within the control plane and between the different realizations. Determination of contaminant mass fluxes is also influenced by the temporal variability of the concentration measurement, especially for large spacings of the observation wells. Passive dosimeter sampling is found to be appropriate for evaluating the stationarity of contaminant plumes as well as for estimating average concentrations over time when the plume has fully developed. Representative sampling has to be performed over several periods of groundwater flow fluctuation. For the determination of mass fluxes at heterogeneous sites, however, local fluxes, which may vary considerably along a control plane, have to be accounted for. Here, dosimeter sampling in combination with time integrated local water flux measurements can improve mass flux estimates under dynamic flow conditions.

A UV-transparent passive concentrator/spectrum deconvolution method for simultaneous detection of endocrine disrupting chemicals (EDCs) and related contaminants in natural waters

Suspected endocrine disrupting chemicals (EDCs) have been widely detected in the environment, and are a source of increasing concern. One of the major challenges in assessing the risk associated with EDCs in the environment is that their environmental concentrations are typically extremely low - on the order of ngL(-1) to microgL(-1) - making them difficult to quantify without extensive pre-concentration procedures. Further complicating their detection is the fact that they are present in mixtures, sometimes with tens to hundreds of other compounds (pharmaceuticals, personal care products, detergents, natural organic matter). The objective of the work described here was to develop a method for rapid monitoring and detection of EDCs at trace concentrations in natural waters. The method makes use of a UV-transparent polymer-based concentrator to be used as a passive sampling device. The UV-transparent polymer-based concentrator serves both as a solid phase extraction medium to concentrate EDCs for analysis and exclude many compounds likely to interfere with detection (fines, macromolecules such as organic matter, ionic surfactants), and as an analytical optical cell, allowing rapid EDC quantification without labor-intensive pre-concentration procedures. A full-spectrum deconvolution technique is used to determine EDC concentrations from measured UV absorbance spectra in the polymer. Experiments were conducted to measure partitioning rate behavior and partition coefficients between the selected polymer (a functional polydimethylsiloxane) and water for seven compounds known or suspected of being endocrine disruptors: estrone, progesterone, estradiol, 2,6-di-tert-butyl-1,4-benzoquinone, phenanthrene, triclosan, and 4-nonylphenol. The method was tested for its ability to detect and quantify individual compounds in mixtures containing up to six components. Results show the method to have selectivity suitable for rapid screening applications at many sites where multiple compounds are present.

The groundwater contribution to surface water contamination in a region with intensive agricultural land use (Noord-Brabant, The Netherlands)

Traditionally, monitoring of soil, groundwater and surface water quality is coordinated by different authorities in the Netherlands. Nowadays, the European Water Framework Directive (EU, 2,000) stimulates an integrated approach of the complete soil-groundwater-surface water system. Based on water quality data from several test catchments, we propose a conceptual model stating that stream water quality at different discharges is the result of different mixing ratios of groundwater from different depths. This concept is used for a regional study of the groundwater contribution to surface water contamination in the Dutch province of Noord-Brabant, using the large amount of available data from the regional monitoring networks. The results show that groundwater is a dominant source of surface water contamination. The poor chemical condition of upper and shallow groundwater leads to exceedance of the quality standards in receiving surface waters, especially during quick flow periods.