Environ. Sci. Technol. 2005, 39, 3555-3562
Traffic as a Source of Organophosphorus Flame Retardants and Plasticizers in Snow ANNELI MARKLUND,* BARBRO ANDERSSON, AND PETER HAGLUND Department of Chemistry, Environmental Chemistry, Umea˚ University, SE-901 87 Umea˚, Sweden
Snow samples collected in northern Sweden at a road intersection and an airport indicated that traffic is a source of organophosphorus flame retardants and plasticizers (OPs) in the outdoor environment. Analysis of snow samples taken at distances of 2, 100, and 250 m from the road intersection showed that the total amount of OPs declined as distance increased. Of the 11 analyzed substances, tris(2-chloroisopropyl) phosphate (TCPP) dominated in the snow samples from the intersection, with levels of 170, 130, and 110 ng/kg snow at distances of 2, 100, and 250 m. Similar amounts of TCPP were found at the airport (100220 ng/kg). These levels are approximately twice as high as the level found in the reference snow sample from a remote area (70 ng/kg). A possible explanation for the higher levels of TCPP found close to the road intersection is that it may be emitted from the interior of cars via their ventilation systems. Triphenyl phosphate (TPP) was identified in lubricants and in waste oil from vehicles, and thus, leakage of transmission and motor oils is a probable source of TPP found at the sampled sites. Ten OPs were detected in the three samples from the airport, of which tributyl phosphate (TBP) was the most abundant, at levels 3 orders of magnitude higher than in the reference sample, that is, 25 000 compared to 19 ng/kg. The main source of TBP at the airport was traced to aircraft hydraulic fluid. Analysis of background air and deposition samples indicated that some OPs are subject to long-range air transportation.
Introduction Organophosphorus compounds (OPs) are frequently utilized as flame retardants and plasticizers, but they are also used as antifoaming agents and additives in products such as lubricants and hydraulic fluids. In recent years, global consumption of OPs has increased sharply. For example, in the year 2001, West European consumption was estimated to amount to 83 000 tons, compared to 58 000 tons in 1998, distributed evenly between chlorinated and nonchlorinated OPs (1, 2). TCPP, TDCPP, TEHP, TPP, TBEP, TBP, and TCEP (Table 1) dominated Swedish imports of OPs in 1999, with imported quantities ranging from 30 to 200 tons (3). Furthermore, TCEP is included in the European Commission second priority list (4), while TCPP and TDCPP are included in the fourth priority list (5). They are also listed as EU High * Corresponding author phone: +46(0) 90 7869125; fax: +46(0) 90 128133; e-mail:
[email protected]. 10.1021/es0482177 CCC: $30.25 Published on Web 04/12/2005
2005 American Chemical Society
Production Volume Chemicals (HPV) together with TPP, TBEP, and TBP (6). The broad application range of OPs and the fact that they are utilized as additives may result in them spreading diffusively into the environment by volatilization, leaching, and abrasion. Some OPs, for example, TBP and TPP, are utilized as extreme pressure additives or antiwear agents in hydraulic fluids, lubricants, and transmission and motor oils to prevent surface damage (7). The amount of the additive varies between products, and TBP is one of the main ingredients (65-79%) in several commercial hydraulic fluids for aircraft, for example, Skydrol 500B-4 and Skydrol LD-4 supplied by Solutia, and HyJet IV-A+ supplied by Chevron. TPP is also reported to be an ingredient (up to 36%) in some hydraulic fluids for aircraft. For example, the content of TPP is 1-5% (w/w) in HyJet IV-A+, according to the product specifications (8). Apart from being a base stock in the formulation of fireresistant hydraulic fluids for aircraft, TBP is also used as a solvent for natural gums (9) and as an additive in antifreeze solutions to reduce foaming (10). TBEP and TEHP are used as softeners in synthetic rubber and PVC to impart lowtemperature flexibility and flame retardation (11). It has previously been suggested that OPs are subject to long-range air transportation (12-14). In support of this suggestion, TBP and other alkyl phosphate esters have been detected in air samples collected in Antarctica (13). It has also been suggested that TCEP (1950 ng/g), TCPP (763 ng/g), and TDCPP (1320 ng/g) found in pine needles in the Sierra Nevada Mountains, United States, originated from long-range air transportation (12). The occurrence of OPs in precipitation in remote areas has been reported by Laniewski et al., who found TCEP and TCPP in concentrations ranging from 1 to 21 ng/L and 1-4.5 ng/L, respectively, in samples of rainwater from Ireland and in snow from Poland and Sweden (14). TBP, TCEP, and TBEP have been detected in rainwater collected in Germany at concentrations of 911, 121, and 394 ng/L, respectively (15). OPs used in both commercial and military hydraulic fluids have been proven to contaminate the surroundings by leakage, for example, TPP has been found at levels of 2-6 µg/g in soil samples from U.S. Air Force bases (16). OPs have also been reported in exhaust gases from motorcycles and cars, with motor oil identified as the main source for tricresyl phosphate isomers present in the atmosphere (17). Data concerning concentrations of OPs in outdoor environments are very sparse, and risk assessments of some of these compounds are currently underway in the European Union, increasing the importance of monitoring these compounds in the environment and identifying significant sources. In this study, 11 OPs (Table 1), primarily based on the amounts imported into Sweden, were analyzed in snow samples from urban areas of northern Sweden. Their distribution patterns and possible sources were also investigated. To verify whether the OPs originated from longrange transportation or more local sources, high-volume air sampling was performed in a remote area in northern Finland. In an attempt to trace possible sources of the individual OPs, hydraulic fluids, motor oils, and deicing products from the airport and waste oils from vehicles were analyzed.
Materials and Methods Chemicals. All solvents used were of analytical grade. Dichloromethane (DCM), acetone, and hexane were purchased from B&J, Fluka Chemie (Buchs, Switzerland); ethanol (99.5%) from Kemetyl (Haninge, Sweden); dichloroethane (DCE) from BDH (Poole, U.K.); Florisil (60-100 mesh) from VOL. 39, NO. 10, 2005 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
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TABLE 1. Recoveries of Organophosphorus Compounds after Method Tests of Liquid-Liquid Extraction (LLE) and Cleanup Using a Florisil Column recovery (%) compound
abbreviation
tripentyl phosphate (internal standard) trimethyl phosphate tripropyl phosphate tributyl phosphate tris(chloropropyl) phosphatea tris(2-chloroethyl) phosphate tris(1,3-dichloro-2-propyl) phosphate triphenyl phosphate tris(2-butoxyethyl) phosphate tris(2-ethylhexyl) phosphate di-n-octylphenyl phosphate tetraethyl ethylenediphosphonateb tris(2-chloroethyl) phosphiteb tricresyl phosphatec
TPeP TMP TPrP TBP TCPP TCEP TDCPP TPP TBEP TEHP DOPP TEEdP CLP1 TCP
CAS Registry No. 2528-38-3 512-56-1 513-08-6 126-73-8 13674-84-5 115-96-8 13674-87-8 115-86-6 78-51-3 78-42-2 6161-81-5 995-32-4 140-08-9 1330-78-5
LLE (n ) 3)
Florisil (n ) 2)
93 47 81 99 96 95 95 99 100 89 92 75 18 n.a
97 120 130 93 93 87 98 97 48 97 92 0 0 n.a
a The commercial mixture of TCPP contains four isomers, of which tris(2-chloroisopropyl) phosphate is the most abundant. b TEEdP and CLP1 were excluded from the study because of low recoveries. c TCP was not included in the standard mixture and was not analyzed in the recovery test.
Kebo Lab (Spånga, Sweden); and dried diethyl ether, methanol (MeOH), potassium hydroxide, and sodium sulfate from Merck (Darmstadt, Germany). The OPs were of technical grade unless otherwise stated. Ethyl-parathion (98.5%) from Dr. Ehrenstorfer (Augsburg, Germany), tributyl phosphate (p.a.), triphenyl phosphate (99%), and tris(2-chloroethyl) phosphate (97%) were purchased from Labora (Sollentuna, Sweden) and tris(2-butoxyethyl) phosphate (94%), tris(2ethylhexyl) phosphate (97%), and tris(2-chloroethyl) phosphite were purchased from Sigma Aldrich (St. Louis, MO). Trimethyl phosphate, triethyl phosphate, tripropyl phosphate, tripentyl phosphate, tetraethyl ethylenediphosphonate, and di-n-octylphenyl phosphate were obtained from Stockholm University (Sweden). The European Flame Retardants Association (EFRA) kindly donated tris(chloropropyl) phosphate and tris(1,3-dichloro-2-propyl) phosphate through Safe Pharm laboratories (Derby, U.K.). Cleaning Procedures. To prevent contamination by OPs from the surroundings, all laboratory equipment has to be cleaned extensively (18). In the present study, all glassware used was soaked overnight in 5% (w/w) potassium hydroxide in ethanol and was rinsed with deionized water and then with ethanol. Filter papers (Munktell filter paper, 20-cm diameter, coarseness 3), used for the snow samples, were rinsed with acetone and the glass wool was washed in a Soxhlet apparatus with DCM prior to use. The polyurethane foam plugs (PUFs) used for air and deposition sampling were cleaned for 5 h by boiling in Milli-Q water and were Soxhletextracted in toluene for 60 h and then in DCM for another 60 h. After the PUFs were dried, they were carefully wrapped in aluminum foil. The glass fiber filters were baked in an oven for 2 h at 200 °C before being enclosed in aluminum foil. Snow Samples. Six snow samples, each weighing approximately 10 kg, were collected from a municipal airport and from the vicinity of a major road intersection (E4 and Kolba¨cksva¨gen, 6 km N of Umeå Centre; traffic intensity: 16 000 vehicles per day) at the end of March 2003. From the airport, two of the samples were collected at the side of the runway (Airp R1 and Airp R2) and one at the side of the aircraft parking place (Airp P). The samples from the road intersection were taken at distances of 2 (E4-1), 100 (E4-2), and 250 m (E4-3), along a line that approximately bisected the angle between the two roads. A reference sample (Ref) of 16 kg of snow was collected in a forested area situated 15 km west of Umeå, approximately 3 km from the nearest road, to ensure that the influence of local traffic on the OP content 3556
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FIGURE 1. Maps describing the location of the sampling sites in Umeå (a and b). In the schematic maps below, “X” denotes the collection points at the airport (c) and at the road intersection (d). was minimal. Schematic maps describing the sampling sites are given in Figure 1. For each sample, the top layer of snow (10-15 cm) within an area of 0.4 m2 was sampled by an aluminum spade and was put in a plastic container. The samples were stored in a freezer (-20 °C) prior to extraction to prevent possible microbial degradation. The samples were stored for 7 months before analysis. Air and Deposition Samples. During 1 week in July 2004 (12.07-19.07), a background air sample of 3200 m3 and a corresponding dry and wet deposition sample were collected in Pallas, northern Finland (coordinates; 67°97′N, 24°12′E) by the Swedish Environmental Research Institute. The samplers were located in an open field with the air sampler at a height of 4 m and the deposition sampler at 1.5 m above the ground. The air sample was collected using a high-volume sampler (20 m3/h) fitted with a glass fiber filter (Grycksbo Munktell 160 MG, 70 mesh pores, Ø 142 mm) in front of three PUFs (110 × 50 mm, density 25 kg/m3) in series (19). The dry and wet deposition sample was collected in an open Teflon-coated sampler, sloping downward to a central opening where three PUFs (55 × 100 mm) in series were attached as adsorbents (20). To incorporate particles deposited on the surface of the collector with the precipitation sample, the collection surface was rinsed with ethanol and
TABLE 2. Content of OPs (µg/g) in Product Samplesa product sample
TPP
TEHP
TBP
TCPb
waste oil from cars waste oil from lorries waste oil from road-making machines waste oil from tractors TurboSuper 10W-30 (engine oil) Agrol Mendo 46 Bio (hydraulic fluid) BP 2380 Turbo oil (airport) BP Turbo oil 2197 engine and accessory oil (airport) Mobile Jet Oil II Synthetic jet engine oil (airport) Kilfrost DF PLUS (80) (deicing fluid, airport) Skydrol 500B4 (hydraulic fluid, airport) Kilfrost ABC-2000 (deicing fluid, airport) Binol Vegocool (hydroelectric power station) Mobil DTE heavy medium oil (hydroelectric power station)
1.0 0.8 1.9
