Environ. Sci. Technol. 2008, 42, 3538–3542
Perfluorinated Surfactants in Surface, Subsurface Water and Microlayer from Dalian Coastal Waters in China X I A O D O N G J U , †,‡ Y I H E J I N , * ,†,§ KAZUAKI SASAKI,| AND NORIMITSU SAITO| School of Environmental and Biological Science and Technology, Dalian University of Technology, 116023, Liaoning, China, Eastern Liaoning University, 118000, Liaoning, China, School of Public Health, China Medical University, 110001, Liaoning, China, and Research Institute for Environmental Sciences and Public Health of Iwate Prefecture, 0200852, Morioka Iwate, Japan
Received December 02, 2007. Revised manuscript received February 25, 2008. Accepted February 26, 2008.
Two predominant perfluorinated compounds (PFCs), Perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA), in surface water (SW, 0–20 cm), subsurface water (SSW, >30 cm depth), and sea surface microlayer (SML, 50 µm thickness) were measured from Dalian Coastal waters in China. The SML samples were collected using glass-plate dipping method. Analysis of the PFCs was conducted through solid-phase extraction, followed by LC/MS-SIM. The PFC’s concentrations in SW samples were consistent with previously reported data in this region. Significantly higher concentrations of PFCs were found in SML samples than corresponding SSW samples. The enrichment factors (EF ) CSML/CSSW) for PFOS wereashighas24–109atthreenear-shoresites.Theconcentration in SW was also generally higher than corresponding SSW samples, giving CSW/CSSW mean ratios of 1.5 and 1.4 for PFOS and PFOA, respectively. This apparent enrichment of PFCs in surface water, especially in the microlayer, has implications for designing measurement techniques, understanding their distributions, and sea spray-mediated transport in the environment.
Introduction Perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA) are among the perfluorinated compounds (PFCs) that have received a great deal of attention in recent years. Because of their chemical characteristics, including extraordinary stability, hydrophobicity, oleophobicity, and excellent surfactant performance, many PFCs have been broadly applied to industrial and domestic production in the past half-century (1, 2). Industrial production and widespread commercial usage have led to their ubiquitous presence in the global ecosystem. They have been found in the body of creatures across the globe, both in indoor and outdoor air * Corresponding author phone: (86)411-84708084; fax: (86)41184708084; e-mail:
[email protected]. † Dalian University of Technology. ‡ Eastern Liaoning University. § China Medical University. | Research Institute for Environmental Sciences and Public Health of Iwate Prefecture. 3538
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ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 42, NO. 10, 2008
and water (3–7). The stability of the CsF bond makes them resistant to metabolism and degradation in the environment. This leads to high trophic magnification factors and the potential for accumulation in various species in the food web (8). Recent studies on animals have revealed some of their toxicological properties, such as neonatal mortality and carcinogenicity (9, 10). These scientific results suggest that their sustaining accumulation in the environment has threatened human health and ecosystem. Given their physicochemical properties of high solubility and negligible vapor pressure when dissolved in water, most of these pollutants can accumulate in aquatic systems and are readily transported by typical hydrological processes (2, 9). At present, relatively little is known about their distribution and transportation in the environment, and the study on their presence in aquatic systems will undoubtedly improve our understanding. A few reports have indicated that the concentrations of PFOA, perfluorononanoate (PFNA) and PFOS in remote ocean waters are around pg/L levels (7, 11). Higher concentrations were observed in near surface than the deep sea samples (11). Most coastal and continental freshwater have indicated PFCs concentrations around the ng/L levels (11–14). The highest concentration of PFOS monitored to date were found as high as several thousands µg/L in Etobicoke Creek, Ontario, Canada (15), where use of PFCs containing fire fighting foam led to the contamination. As for their long-range global transport, there are two major hypotheses that have been proposed at present. The one suggests that the dispersion of volatile precursor compounds, such as fluorotelomer alcohols and sulfamido alcohols, and their subsequent environmental oxidation gives rise to the formation of the perfluorinated carboxylic acids and sulfonates in remote regions (16). The other suggests that oceanic transport of PFCs can account for their presence in the remote regions such as the Arctic Ocean (2, 17). Many PFCs are excellent surfactants, which suggest that these chemicals may accumulate on the air/water interface found in the sea microlayer (SML). The knowledge of their distribution in SML may help us to design best sampling strategies and devices so that we can accurately measure the actual distribution in the water. It is possible that different sampling methods could result in different results depending on the proportion of the enriched microlayer to the corresponding underlying water (subsurface water, SSW) collected. The surface enrichment might be important to sea creatures which spend a great deal of time at the air/water interface (e.g., seabirds, otters, pinnapeds, dolphins), particularly to fish eggs and larvae in SML which serves as an important habitat for them. Studies of the toxicity of fish eggs and larvae exposed to other SML contaminants have shown that the SML in polluted areas leads to significantly higher rates of mortality and abnormality of fish embryos and larvae (18). SML is a very important compartment of oceanic environmental system and plays an important role in the fate of persistent organic pollutants (19). It is thought that the PFCs enriched in SML could be transported into the atmosphere as organic-rich particles via wave and wind interactions as other organic pollutants (2, 20). Given the vast surface area of the sea, even relatively low concentrations in an SML could be significant on a global scale. To our knowledge, however, there have been no direct systematic investigations on the PFCs in SML to date. The goal of this work is to determine if the enrichment phenomena exist significantly in SML in coastal waters. 10.1021/es703006d CCC: $40.75
2008 American Chemical Society
Published on Web 04/11/2008
FIGURE 1. Sampling sites in Dalian coastal waters in China.
Experimental Procedures Standards and Reagents. Perfluorooctanoic acid (98% purity) was obtained from Aldrich (Milwaukee, WI), and Potassium salt of PFOS (98% purity) was purchased from Fluka (Milwaukee, WI). HPLC grade methanol and acetonitrile were purchased from Wako Pure Chemicals (Osaka, Japan). Presep-C Agri cartridges that contained styrene divinybenzene polymethacrylate 220 mg on a polyethylene housing were also purchased from Wako Pure Chemicals (Osaka, Japan). Deionized water was used only after filtration through a Presep-C Agri cartridge to remove residual PFOS and PFOA (dePFOS water). Water Sampling. Water samples were collected at 29 sites from Dalian coastal waters under calm sea conditions in October 2006, as depicted in Figure 1. Sixteen sites collected only SW, eight sites collected both SW and SSW, and five sites collected both SSW and SML. During the sampling period, the wind blew predominantly to the northwest, and the days with wind speed
