NEW PASSIVE SAMPLING SYSTEMS FOR MONITORING ORGANIC MICROPOLLUTANTS AND HEAVY METALS IN SHKODRA LAKE Anila Neziri¹, Pranvera Lazo², Janine Brümmer3 Albrecht Paschke4 ¹Dept. of Biochemistry, Faculty of Natural Sciences, University of Shkodra, Albania ²Dept. of Chemistry, Faculty of Natural Sciences, University of Tirana, Albania 3 School of Biological Sciences, University of Portsmouth, UK 4 Dept. of Ecological Chemistry, UFZ Centre for Environmental Research Leipzig, Germany Corresponding author:
[email protected] ABSTRACT The determination of organic micropollutants and heavy metals in surface water is of ecotoxicological relevance due to their high toxic potential, their persistence and their tendency to bioaccumulate. New passive sampling devices for time-integrative monitoring of the dissolved and thus bioavailable fraction of these trace contaminants were tested in lake Shkodra. The membrane-enclosed silicone collector (MESCO II), applicable for more hydrophobic organic pollutants were deployed at three different stations of lake Shkodra. After retrieval of the samplers, the silicone rods (collecting phase) were analysed by thermodesorption–GC/MS. The time-weighted average (TWA) water concentrations of organic micropollutants were calculated using laboratory-derived sampling rates (Rs). The inorganic variant of the Chemcatcher® passive sampler was used to monitor heavy metal pollution at three different sites of Shkodra Lake. The extracts from the receiving phase of the exposed samplers were analysed for heavy metals using a AAS/ETA and ICP/MS methods. The water concentrations of Cd and Cu were calculated using the element-specific uptakes rates estimated for the prevailing field conditions.
Keywords: Silicone, MESCO, polycyclic aromatic hydrocarbons
Chemcatcher®, heavy metals,
AIMS AND BACKGROUND Water-quality monitoring generally still relies on spot sampling followed by instrumental analysis in order to quantify “total” concentrations of pollutants. This procedure gives only a snapshot of
the situation at the time of sampling. The pollutants can be present in natural water both freely dissolved and particle-bound and were usually not measured separately. Hence, the bioavailable fraction, which corresponds to the freely dissolved fraction and is very important for ecological risk assessment, is not easily accessible. Passive sampling techniques can solve this problem and can provide a cost-efficient biomimetic (time-integrative) water monitoring. Passive samplers developed since the 1990s are becoming increasingly popular in environmental monitoring (1, 2, 4). This is due to the fact that they are simple in design and require no power supply, which makes them suitable for remote sampling locations and larger networks of measurement points. These new sampling systems can be easily standardized and modified if necessary. In addition, the results are often more reproducible than those from biological samples. The passive uptake of elements/coumponds in a collecting phase (e.g. an organic solution or a polymer material) is caused by a gradient of the chemical potential existing between this phase and the environmental medium. Depending on the design of the sampler, the mass-transfer limiting step is either considered as molecular diffusion through capillaries and pores or the permeation through a non-porous membrane. The amounts of the chemical species/compounds accumulating in the sampler are related to their concentrations in the environmental medium being studied and the duration of exposure of the passive sampler. The ambient temperature and flow conditions also affect the substance enrichment in the collector. The use of passive samplers is usually limited to their linear uptake phase in order to obtain time-weighted average concentration in the monitored water (normally over a few days to weeks). For a number of passive sampler types, uptake rates are already available from laboratory calibrations for a wide spectrum of aqueous micropollutants. With non-polar organic compounds it is possible to adjust uptake rates from laboratory experiments to actual field conditions or to carry out calibration in situ by spiking the sampling phase before use with reference substances either labeled with stable isotopes (e.g. 2H or 13C) or not present in the environment and then determine their elimination
over the exposure period of the sampler. Moreover, since 2006 a guidance document is available14 on the regular use of passive sampling in water monitoring. Meanwhile this document is developed further into a new ISO standard15. Some years ago, the semipermeable membrane devices (SPMDs) were applied in Shkodra Lake as biomimetic sampling technology for persistent organic micropollutants (chlorinated hydrocarbons, polycyclic aromatics, etc.) in lake water. The combination of SPMDbased sampling with appropriate bioassays and chemical analysis provided a useful tool for the identification of main waterborne organic pollutants in Lake Shkodra.9 But the SPMDs are expensive and their processing is very time- and solvent-consuming. The membraneenclosed silicone collector (MESCO II) which consists in a silicone rod enclosed in an air-filled low-density polyethylene membrane bag is developed for monitoring non-polar persistent organic pollutants (POPs).13 This sampler is inexpensive and simple to process. Therefore we used this sampler type in the actual study. Although a recent study showed that the concentrations of heavy metals in both the water and the sediments of Lake Shkodra are, in general, still within the permissible limits of the EU standards4, we applied a Chemcatcher variant for heavy metals to verify these findings. The TWA sampling process of the heavy metal ions in this device is based on their diffusion through a porous cellulose acetate (CA) membrane to a receiving phase, where they are sequestered by chelating Empore™ disk8. A Chemcatcher variant sampler for heavy metals was deployed in Lake Shkodra. AAS method using graphite furnace as atomizer and ICP-MS method was used analysing heavy metals. EXPERIMENTAL Sampling site. Shkodra Lake is located on the border between Montenegro and Albania at 40º 10' North latitude, 19 º 15’ East longitudes. The lake water level also varies seasonally from 4.7 to 9.8 m above sea level.
The largest inflow is the Moraca River (Montenegro), which provides more then 62% of the lake water and the outflow is Buna River. During the last decades the anthropogenic pollution is going to be significant in this area. The Moraca River, the main tributary of the lake, brings most pollutants into the lake from Aluminum Company (KAP), agricultural plantations complex Podgorica landfill, the city drainage collector etc.5 The industrial activity in Albania decreased since 1990, but the residues (in the form of dumps of ex-mining or chemical industry) of them in environment posed a risk for the human health.6 The sampling points with MESCO II and Chemcatcher (Inorganic version) which are (S1) Zogaj, (S2) Peshkimi, (S3) Zues, are represented in Figure 1.
Figure1. Map of sampling points in lake Shkodra MESCO II passive sampler. The MESCO II strip consists of 1.5 cm silicone rods enclosed in low density polyethylene membrane (segmented by heat-sealing). The samplers were prepeared in the UFZ Centre in Leipzig, Germany as is described elsewhere(10, 13) and were shipped to Albania alongside with transportation/trip blanks (additional MESCO strips) necessary to fulfill the requirements of quality control14. They were exposured for three weeks in lake Shkodra water during May 2006. The silicon rods for both samplers were processed in a thermodesorption unit TDU – GC/MS as is described in ref. 10 Chemcatcher (inorganic version). The Chemcatcher® (2nd generation, disposable prototype) consits of a polycarbonate body which holds an Empore disk covered by porous cellulose acetate membrane3. The chelating disks were precleaned with
30 mL 2N HNO3 and deployed for 2 weeks during September 2007. The retrieved samplers were dismantled and the Empore disks were extracted with 30 mL 2N HNO3. The extracts were analyzed by using AAS/ETA and ICP/MS. Data processing In accordance with the passive sampling theory for the MESCO II device 4 and Chemcatcher 3, it was used the formula (1) for calculating the time weighted average concentrations (TWA) in the water. The sampling rates or Rs values were taken from Paschke et al 10, table 1 for MESCO II, and from Runeberg et al 12 for Chemcatcher. (1) where: Cw Time weighted average concentration Rs - Sampling rate [ml/h] Mo- Mass of analyte found in the blank Ms(t)- Mass of analyte accumulated Table 1. The sampling rates or Rs values for MESCO II sampler for some PAHs taken from Paschke A 10 . Rs (mL/h) Compound Phenanthrene Anthracene Fluoranthene Pyrene
Paschke et al 10 0.72 0.83 0.26 0.23
RESULTS AND DISCUSSIONS The following compounds were identified (and partly quantified) in the MESCO II samplers after field exposure: Naphthalene, 1Methylnaphthalene, 2-Methylnaphthalene, 2,6-Dimethylnaphthalene, 1,4,6-Trimethylnaphthalene, Acenaphthene, Fluorene, Phenanthrene.
Anthracene, Fluoranthene, Pyrene, Chrysene, Benzo[b]fluoranthene, Benzo[a]pyrene. Form Table 2 it can be seen the TWA concentrations calculated for Phenanthrene. Anthracene, Fluoranthene and Pyrene. The TWA concentrations calculated from MESCO II field trial of analyzed compounds are lower than EU, Environmental Quality Standards for Priority Substances, 2007, C 102 E/103 in both sampling stations. Table 2. The TWA concentrations of PAHs in (ng/L) ), (N=3) calculated from lab-derived sampling rates (Rs) for MESCO II, ( Rs values from Paschke et al 10) Stations Substance S1(Zogaj) S2(Zus) S3(Peshkimi) 0.588 0.191 0.141 Fluoranthene 1.777 0.809 0.722 Phenanthrene 0.286
