Dry and wet deposition processes as a source of organophosphate flame retardants (OFR) in soils

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Title: Dry and wet deposition processes as a source of organophosphate flame retardants (OFR) in soils
Authors: Mihajlović, Ivana
Thesis advisor: Prof.Dr. Elke Fries
Thesis referee: Prof.Dr. Mirjana Vojinović Miloradov
Abstract: Flame retardants are substances, which addition in various materials (furniture, plastics, electronics equipment, textiles, etc) could save a lot of lives and injuries caused by fires. On the other side, the migration of flame retardants from products during their whole life cycle results in their ubiquitous presence in the environment and reflects negative effects on ecosystems and human health. Global consumption of organophosphate flame retardants (OFR) as alternative substitutes of polybrominated diphenyl ethers has increased sharply in recent years. Studies on the presence and sources of OFR in surface water, ground water, sediments, snow, rainwater, indoor and outdoor air and analyses of OFR in these compartments have also increased in the last decade. In this doctoral thesis an analytical method was developed to determine six OFR (tris(2-chloroethyl) phosphate (TCEP), tris(2-chlorisopropyl) phosphate (TCPP), tris(1,3-dichloro-2-propyl) phosphate (TDCP), tris(2-butoxyethyl) phosphate (TBEP), tri(n-butyl) phosphate (TnBP) and triphenyl phosphate (TPP)) in soil. The method consists of a combination of Twisselmann extraction and solid-phase microextraction (SPME), followed by gas chromatography-mass spectrometry (GC-MS). To develop the method, spiked soils were extracted using a Twisselmann extractor after freeze-drying. The extracts were evaporated to dryness, redissolved, and filtered. A volume of 7 mL was then analysed by SPME, followed by GC-MS. The effects of different parameters on analyte recoveries during sample preparation e.g. solvent for Twisselmann extraction, solvent for redissolving the extract, addition of copper, and filtration of the extract were systematically investigated. Under optimum conditions, 10 g of soil were extracted using toluene, and the extract was redissolved in methanol/water (1:14) and filtered. It was not necessary to add copper. For TnBP, TBEP, TCPP, and TCEP, recoveries ranged from 77.0 % to 89.6 %. Those for TPP and TDCP were much lower, at 31.5 % and 42.0 %, respectively (addition level 22.9-45.8 ng/g). The variability of recoveries under these conditions was between 0.3 and 16.2 % (n = 3). Limits of detection (LOD) were 0.002-3 ng/g. When ultrasonication was used instead of Twisselmann extraction in the developed method, recoveries were three to four times lower (27.4 % to 30.6 %), but the variability of recoveries was below 3 % (n = 3). The method was applied to quantify OFR in soils collected from different sampling locations (urban, semi-urban and rural) in Germany. The results indicated for the first time that atmospheric deposition leads to soil contamination by OFR. Since it has been shown in animal experiments (F344/N rats and B6C3F1 mice) that chlorinated OFR were carcinogen and also have negative effects on human health (Matthews et al., 1991, 1993, Johnson, 1999), the further studies were focused on sources of chlorinated OFR. Therefore, the influence of dry and wet deposition processes as a source of chlorinated OFR in soils was systematically investigated. Soil samples were collected in 2010/11 during a period of snow falling to snow melting, a period of rainfall and a dry period. Snow and rainwater samples were also collected from the soil sampling site. Concentrations of TCEP were between 236 and 353 ng/L in snow and 78 and 234 ng/L in rain. TCPP concentrations were between 226 and 284 ng/L in snow and 371 and 385 ng/L in rain. In soil samples, concentrations ranged from 5.07 to 23.48 ng/g dry weight (dwt) for TCEP and 5.66 to 19.82 ng/g dwt for TCPP. Concentrations of TDCP in rainwater and snow samples were rather low (46 and 100 ng/L, respectively); concentrations of TDCP were below the limit of detection in soil samples. Snow melting caused enhanced soil concentrations of TCEP and TCPP. However a greater effect of snow melting was observed for TCEP than for TCPP. No significant correlation between precipitation amounts and soil concentrations was observed for both compounds. The influence of wet deposition to the soil contents of TCEP and TCPP may be covered by volatilisation or by the migration of both compounds to deeper soil zones with seepage water, based on their volatility and high water solubility, respectively. Snow was found to be even a more efficient source of chlorinated OFR in soil than rainwater. During dry weather, the soil concentrations of both compounds seemed to be driven mainly by concentrations in air, which are driven by source emission strengths and photochemical degradation in the atmosphere. Rainwater concentrations of OFR were used to assess air concentrations from the scavenging ratios at equilibrium conditions and the potential for the accumulation of OFR in soil based on the air-soil exchange was estimated. Calculated values of median air concentrations were 0.0034 ng/m3 for TCEP and 0.99 ng/m3 for TCPP. Total OFR specific loads were 3756 ng m-2 day-1 within the first 24 hours and 3028 ng m-2 day-1 within the next 24 h. Fugacity calculations (0.011 to 0.103 for TCPP and 0.005 to 0.073 for TCEP) indicated net deposition from air to soil for both compounds.
URL: https://repositorium.ub.uni-osnabrueck.de/handle/urn:nbn:de:gbv:700-2012070610196
Subject Keywords: TCEP; TCPP; rain; snow; organophosphate esters
Issue Date: 6-Jul-2012
Type of publication: Dissertation oder Habilitation [doctoralThesis]
Appears in Collections:FB06 - E-Dissertationen

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