Comment on “Global Aquatic Passive Sampling (AQUA-GAPS): Using Passive Samplers to Monitor POPs in the Waters of the World” Recently Lohmann and Muir (1) expressed the viewpoint that persistent organic pollutants (POPs) pertinent to the Stockholm Convention in global waters should be monitored, preferably with the use of passive sampling techniques using polyethylene (PE) as the sorption medium. The authors argued that thick PE sheets, which are cheap and firm and can be tailored to various detection sensitivities with various volumes, are suitable for assessing almost all POPs. The authors further recommended using a combination of kinetic and equilibrium sampling modes and deploying the passive samplers in background and remote sites far away from known point sources of pollution. Needless to say, the authors’ views are extremely important and timely as the global community strives to combat the potentially adverse effects of POPs on humans and wildlife. While we readily echo the authors’ viewpoint, we nevertheless want to present three suggestions with the hope to enhance the use of PE-based passive samplers in global aquatic monitoring of POPs. First, sediment porewater, an important link to the bioavailability of POPs, should be monitored along with surface waters. Contaminated sediment is a known source of POPs (2, 3), and concentrations of POPs in sediment porewater and biota have been shown to linearly correlate with each other (4). Consequently, characterization of POPs in sediment porewater is a crucial step toward better assessment of the ecological risk of POPs in aquatic environments. Technically, several previous studies have utilized
(This is contribution No. IS-1194 from GIGCAS). 10.1021/es1008467
various passive samplers for sensing POPs in sediment porewater (5-8), which can form the foundation for monitoring sediment porewater POPs within a global network. Second, if the AQUA-GAPS network is established, we favor including locations impacted by human activities, in addition to remote and background sites. The main reason is that identifying and quantifying anthropogenic impacts on the environment should be a key component of any monitoring program. This is, of course, not to undermine the importance of monitoring pristine sites to understand the buffering capacity of oceans in recycling of POPs. Rather, these two types of monitoring sites can be complementary to each other, better serving the mandates of the Stockholm Convention. Third, the authors suggested the use of bare PE films in field deployment (Figure 1 of ref 1). The authors further suggested using performance reference compounds to avert potential biofouling. On the other hand, we strongly advocate the utility of protective shields (preferably a combination of copper and glass fiber filter) in field deployment of passive samplers. This is particularly necessary if moderately to heavily impacted sites are indeed included in the AQUA-GAPS network. Furthermore, use of performance reference compounds can be considerably costly and labor intensive if a large number of target analytes are monitored. By using copper and glass fiber filter as the protective shield, a PE passive sampler can be field-deployed for an extended period of time without the concern of biofouling and high cost of performance reference compounds. Finally, it is worthwhile to note that reference 45 in ref 1 was published in Water Research rather than Chemosphere. LIAN-JUN BAO State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, China,
2010 American Chemical Society
Published on Web 05/10/2010
and Graduate School, Chinese Academy of Sciences, Beijing EDDY Y. ZENG* State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, China
[email protected] (1) Lohmann, R.; Muir, D. Global aquatic passive sampling (AQUAGAPS): Using passive samplers to monitor POPs in the waters of the world. Environ. Sci. Technol. 2010, 44, 860–864. (2) Achman, D. R.; Brownawell, B. J.; Zhang, L. Exchange of polychlorinated biphenyls between sediment and water in the Hudson River estuary. Estuaries 1996, 19, 950–965. (3) Zeng, E. Y.; Venkatesan, M. I. Dispersion of sediment DDTs in the coastal ocean off southern California. Sci. Total Environ. 1999, 229, 195–208. (4) Kraaij, R.; Mayer, P.; Busser, F. M.; Van Het Bolscher, M.; Seinen, W.; Tolls, J. Measured pore-water concentrations make equilibrium partitioning worksA data analysis. Environ. Sci. Technol. 2003, 37, 268–274. (5) Van Der Heijden, S.; Jonker, M. T. O. PAH bioavailability in field sediments: Comparing different methods for predicting in situ bioaccumulation. Environ. Sci. Technol. 2009, 43, 3757–3763. (6) Mayer, P.; Vaes, W. H. J.; Wijnker, F.; Legierse, K. H. M.; Kraaij, R. H.; Tolls, J.; Hermens, J. M. Sensing dissolved sediment porewater concentrations of persistent and bioaccumulative pollutants using disposable solid-phase microextraction fibers. Environ. Sci. Technol. 2000, 34, 5177–5183. (7) Fernandez, L. A.; Macfarlane, J. K.; Tcaciuc, A. P.; Gschwend, P. M. Measurement of freely dissolved PAH concentrations in sediment beds using passive sampling with low-density polyethylene strips. Environ. Sci. Technol. 2009, 43, 1430– 1436. (8) Maruya, K. A.; Zeng, E. Y.; Tsukada, D.; Bay, S. M. A passive sampler based on solid phase microextraction (SPME) for quantifying dissolved HOCs in sediment interstitial water. Environ. Toxicol. Chem. 2009, 28, 733–740. Environmental Science & Technology edits all Letters for length, punctuation, and clarification of references. Authors approve of changes prior to publication.
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June 15, 2010 / ENVIRONMENTAL SCIENCE & TECHNOLOGY 9 4385
