Determination of Chloroacetates in Atmospheric Particulate Matter


Chloroacetates (CAAs) are ubiquitous in the environment. This study presents chloroacetates level in atmospheric particulate matter (APM) collected at...
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Environ. Sci. Technol. 2003, 37, 2336-2339

Determination of Chloroacetates in Atmospheric Particulate Matter EVANGELOS B. BAKEAS, ATHINA G. ECONOMOU, AND PANAYOTIS A. SISKOS* Environmental Analysis Group - Analytical Chemistry Laboratory, Department of Chemistry, National and Kapodistrian University of Athens, Panepistimiopolis, 15771 Zografos, Athens, Greece HARTMUT FRANK Chair of Environmental Chemistry and Ecotoxicology, University of Bayreuth, D-95440 Bayreuth, Germany

meteors, and CAAs have been found in rainwater, snow, and cloudwater (3, 5-14, 16). Furthermore, they are also present in surface waters of rivers and lakes, in seawater, and in drinking and wastewaters treated with free chlorine for disinfection (5). TCA has also been found in soils suggested to be naturally formed (4, 5, 15, 17). Although there is much work on CAA levels in a variety of media, there are surprisingly few data on CAAs in air (1, 5). This work deals with CAAs in atmospheric particulate matter (APM). To the best of our knowledge, this is the first report on CAA levels in APM. Our aim was to investigate the occurrence of CAAs in APM, to determine their levels, and, through their correlation with pollution and meteorological data, to propose some ideas concerning their formation and fate in the atmosphere.

Materials and Methods Chloroacetates (CAAs) are ubiquitous in the environment. This study presents chloroacetates level in atmospheric particulate matter (APM) collected at Athens center. CAAs have been derivatized to their respective propyl esters and determined by gas chromatography (GC) with electron capture detection (ECD). Monochloroacetate (MCA) was the most abundant, followed by dichloroacetate (DCA) and trichloroacetate (TCA). Concentration values range from 3.0 to 8240 ng g-1 (0.6-2010 pg m-3). Correlations to meteorological and pollution parameters are discussed, indicating that car exhausts may be a direct or indirect source of MCA, but origin from natural marine sources may also be relevant.

Introduction Chloroacetates (monochloroacetate, MCA; dichloroacetate, DCA; trichloroacetate; TCA) are of considerable concern because of their widespread occurrence in the environment (1, 2). With respect to ecotoxicological considerations, chloroacetic acids (CAAs) are important because of their phytotoxicity. TCA and DCA have been used as herbicides until the late 1980s, and several anilides of MCA are still in use such as Alachlor and Metolachlor. CAA may arise from both anthropogenic and natural sources (3); the major ones that are currently under debate are (a) formation in the atmosphere by photochemical degradation of chlorinated solvents, (b) formation in the hydrosphere by reaction of active chlorine with dissolved organic matter, e.g. chlorination of drinking water, and (c) in soil by processes involving haloperoxidases (2, 4). However, the relative importance of these sources is not known, and the proposed mechanisms of formation are not fully proven. There are indications that fractions of 1,1,1-trichloroethane, trichloroethene, and tetrachloroethene released to the atmosphere may be degraded through reactions with radical species, such as hydroxyl (OH•) or chlorine (Cl•), to chloroacetaldehydes and chloroacetyl chlorides which can yield chloroacetic acids (3, 5). Since the pKa values of the acids are low, airborne chloroacetates are expected to be associated with atmospheric condensed liquid water (6). An important input pathway of CAAs into the biosphere is washout by hydro* Corresponding author phone: ++30 210 7274311; fax: ++30 210 7274750; e-mail: [email protected] 2336

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ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 37, NO. 11, 2003

Chemicals. Sodium bicarbonate, sodium chloride (all analytical grade, p.a.), and sulfuric acid (95%) were obtained from Merck (Darmstadt, Germany). 1-Propanol and pentane (99%, gc grade) were from Fluka (Switzerland). Monochloroacetic acid (MCA), dichloroacetic acid (DCA), trichloroacetic acid (TCA), and 2,2-dichloropropionic acid (DCPA) were from Acros (Belgium). Water was deionized and purified by means of a Millipore Q System (USA). Sampling. The sampling site was on the roof of the building of the Ministry of the Environment (25 m height) at Patission Street, located near the center of Athens. Patission Street has a heavy traffic load with about 60 000 vehicles passing per day. The traffic consists mainly of light-duty gasoline-engined motor vehicles. Sampling was carried out with a high-volume sampler (General Metal Works) equipped with a holder for glass-fiber filters (25 cm × 20 cm, Whatman, UK). Sampling volume was 1000 m3, collected within 24 h (0.7 m3 min-1). After sampling, glass-fiber filters were stored in glass containers at -40 °C until analysis, not more than a week. To account for contamination effects, blank field filters were handled identically. Sample Preparation. Before extraction, the filter samples were allowed to warm to room temperature (20 °C). The filters were cut in half, and each of the halves was further cut into small pieces (nearly 0.5 cm × 0.5 cm). The pieces of each half were extracted with 15 mL of deionized water in a sonicator bath for 2 h; this time length was selected according to recovery experiments with extraction times of 0.5, 1, and 2 h. The extraction efficiencies for MCA, DCA, and TCA were found to be 89 ( 7%, 112 ( 8%, and 92 ( 5% (n ) 12), respectively, by spiking clean filters in the concentration range from 0.5 to 1000 ng mL-1. The extracts were combined, and the water was evaporated in the presence of base. The dry CAAs were derivatized as described by Reimann et al. (3) by esterification with propanol/sulfuric acid. GC Determination. GC analyses were performed on a gas chromatograph (model 3300, Varian Instruments, U.S.A.) equipped with on-column injector and ECD (Model 02-179201); helium was used as carrier gas. Aliquots of 5 µL of the derivatized samples in pentane were injected onto a deactivated fused-silica retention gap (8.0 m × 0.32 mm). Gas chromatographic separation was carried out on a fused-silica column coated with cyano (7%)-phenyl (7%)-methylsilicone (007-1701, 50 m × 0.32 mm, film thickness 1.0 µm; Quadrex, UK). The initial oven temperature was 45 °C (6 min) followed by a temperature program of 3 °C min-1 to 116 °C, 20 °C min-1 to 200 °C, 2 min isothermal. Chloroacetates were identified based upon the relative retention time in reference 10.1021/es020167n CCC: $25.00

 2003 American Chemical Society Published on Web 04/18/2003

TABLE 1. CAAs Concentrations in Atmospheric Particulate Matter Samples sampling date 04.12.2000 07.25.2000 07.26.2000 07.29.2000 08.02.2000 12.20.2000 01.02.2001 01.19.2001 02.24.2001 06.07.2001 07.03.2001 07.04.2001 07.09.2001 07.11.2001 08.10.2001

sampling volume, m3

mass APM, g

950 950 905 922 930 940 932 1805 912 950 925 918 937 940 922 median range

0.1648 0.1995 0.1834 0.1906 0.2004 0.1837 0.1644 0.3442 0.1798 0.1542 0.1281 0.1549 0.2405 0.1562 0.194

MCA

DCA

TCA

ng g-1

pg m-3

ng g-1

pg m-3

ng g-1

pg m-3

8235 6260 844 1035 715 400 91 260 523 4320 1760 587 45.0 480 2790 715 45.0-8235

2010 1315 170 214 154 78 16 50 103 701 244 99 11.5 79 589 154 11.5-2010

2660 1150 39 2.9 142 10.7 15.9 6.3 3.0 245 53.1 4.7 23.8 3.6 137 23.8 2.9-2660

460 240 7.9 0.6 30.7 2.1 2.8 1.2 0.6 39.8 7.3 0.8 6.1 0.6 29 6.1 0.6-460

270 595 19 7.3 10.2 4.6 12