Branislav Vrana

A “toolbox” for biological and chemical monitoring requirements for the European Union's Water Framework Directive

Until now, water quality monitoring has relied heavily on spot sampling followed by instrumental analytical measurements to determine pollutant concentrations. Despite a number of advantages, this procedure has considerable limitations in terms of (i) temporal and spatial resolution that may be achieved at reasonable cost, and (ii) the information on bioavailability that may be obtained. Successful implementation of the Water Framework Directive (2000/60/EC) across EU member states will require the establishment and use of emerging and low-cost tools as part of monitoring programmes. These techniques may complement monitoring already in place by providing additional information with the aim to obtain a more representative picture of the quality of a water body. This article considers the limitations associated with current monitoring practice and presents, in the form of a review, emerging biological and chemical monitoring tools that may become part of a toolbox of techniques for use by those in charge of assessing water quality. Biological monitoring techniques include biomarkers, biosensors, biological early warning systems and whole-organism bioassays. Sampling and analytical tools developed for chemical assessment comprise biosensors, immunoassays, passive samplers, and sensors. Descriptions of these devices and a discussion of their suitability for different types of monitoring detailing advantages and limitations are presented. Finally, quality assurance and quality control or method validation issues are summarised.

Performance optimisation of a passive sampler for monitoring hydrophobic organic pollutants in water

The performance of an integrative passive sampler that consists of a C18 Empore disk sorbent receiving phase fitted with low density polyethylene membrane was optimised for the measurement of time-weighted average concentrations of hydrophobic micropollutants in water. A substantial improvement of sampling characteristics including the rate of sampling and the sampling precision was achieved by decreasing the internal sampler resistance to mass transfer of hydrophobic organic chemicals. This was achieved by adding a small volume of n-octanol, a solvent with high permeability (solubility [times] diffusivity) for target analytes, to the interstial space between the receiving sorbent phase and the polyethylene diffusion-limiting membrane.

Application of Chemcatcher passive sampler for monitoring levels of mercury in contaminated river water

A passive sampler (Chemcatcher) consisting of a 47 mm Emporetrade mark chelating disk (CHE) with iminodiacetic groups as the receiving phase overlaid with a diffusion membrane was developed and calibrated for the monitoring of Hg in water. Three different diffusion membranes including cellulose acetate (CA), polyethersulphone (PS) and cellulose dialysis membrane (D) were tested. The best performance was obtained with the CHE-PS tandem. The effective sampling rate of the device (R(s), L day(-1)) is defined as the equivalent volume of water extracted per unit time, and is analyte specific and can be determined experimentally in a flow-through tank. Effects of water temperature and turbulence on the uptake rate of Hg were assessed under controlled laboratory conditions. Sampling rates were in the range of 0.029-0.091 L day(-1). An increase in sampling rate with turbulence was demonstrated. The detection limit of the sampler obtained in flowing waters ranged between 2.2 and 2.9 ng L(-1)Hg. The performance of Chemcatcher was tested alongside spot water sampling in a 14-day field deployment at two locations on the Valdeazogues River, Almadén, Spain. In general, the Hg concentration estimated by the Chemcatcher was lower than that found in spot water samples collected over the same period. This may be explained by the behaviour of this sampler that measures only the labile fraction of Hg in water, and this will exclude some species. However, Chemcatcher preconcentrates Hg allowing its determination in some places where its concentration is below the detection limit of spot sampling.

Assessment of Chemcatcher passive sampler for the monitoring of inorganic mercury and organotin compounds in water

Several configurations of receiving disks and diffusion membranes were tested for monitoring mercury and organotin compounds (monobutyltin, dibutyltin, tributyltin, and triphenyltin) in water with a passive sampler. This passive sampler is based on the diffusion of these compounds through a specific diffusion-limiting membrane and their subsequent accumulation on a specific receiving phase, all materials being commercially available. The proposed sampler for inorganic mercury comprises a 47-mm Empore™ chelating disk as receiving phase and polyethersulfone as diffusion membrane. For monitoring organotins, the receiving phase is a 47-mm Empore™ C18 disk, and the diffusion membrane is cellulose acetate. ICP-MS and GC-ICPMS/GC-FPD were used for inorganic mercury and the organotins analysis, respectively. The effects of environmental variables such as pH and salinity that could influence accumulation of test substances in receiving phase were studied. Linear uptake for all compounds was observed for at least 14 days of exposure at a constant aqueous analyte concentration in a flow-through system under controlled conditions of temperature, turbulence, and analyte concentration. Compound-specific sampling rates at 11°C and simulated water turbulence of 40cms−1 varied between 0.018 and 0.137Ld−1. Compounds collected by the sampler exhibited detection limits ranging between 0.7 and 5.9ngL−1. The feasibility of using these samplers in the field was tested in a polluted commercial harbour. The behaviour of the samplers to monitor target compounds was compared with those obtained from spot samples of water taken throughout the field deployment period. Data from laboratory studies and field trial support the feasibility of these samplers to measure the freely dissolved fraction of these important target analytes in water.

Performance of semipermeable membrane devices for sampling of organic contaminants in groundwater

Lipid-filled semipermeable membrane devices (SPMDs) are receiving increasing attention as passive, in situ samplers for the assessment of environmental pollutant exposure. Although SPMDs have been successfully used in a variety of field studies in surface waters, only a few studies have addressed their characteristics as groundwater samplers. In this study, the performance of the SPMDs for monitoring organic contaminants in groundwater was evaluated in a pilot field application in an area severely contaminated by chemical waste, especially by chlorinated hydrocarbons. The spatial distribution of hydrophobic groundwater contaminants was assessed using a combination of passive sampling with SPMDs and non-target semiquantitative GC-MS analysis. More than 100 contaminants were identified and semiquantitatively determined in SPMD samples. Along the 6 field sites under investigation, a large concentration gradient was observed, which confirms a very limited mobility of hydrophobic substances in dissolved form in the aquifer. The in situ extraction potential of the SPMD is limited by groundwater flow, when the exchange volume of well water during an exposure is lower than the SPMD clearance volume for the analytes. This study demonstrates that SPMDs present a useful tool for sampling and analyzing of groundwater polluted with complex mixtures of hydrophobic chemicals and provides guidance for further development of passive sampling technology for groundwater.