Article pubs.acs.org/est
Distribution, Partitioning and Bioaccumulation of Substituted Diphenylamine Antioxidants and Benzotriazole UV Stabilizers in an Urban Creek in Canada Zhe Lu,† Amila O. De Silva,*,† Thomas E. Peart,† Cyril J. Cook,† Gerald R. Tetreault,† Mark R. Servos,‡ and Derek C.G. Muir†
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Aquatic Contaminants Research Division, Water Science Technology Directorate, Environment and Climate Change Canada, 867 Lakeshore Road, Burlington, Ontario L7S 1A1 Canada ‡ Department of Biology, University of Waterloo, Waterloo, Ontario N2L 3G1 Canada S Supporting Information *
ABSTRACT: Substituted diphenylamine antioxidants (SDPAs) and benzotriazole UV stabilizers (BZT-UVs), previously under reported classes of organic contaminants, were determined in sediment, water, and freshwater biota in an urban creek in Canada. SDPAs and BZT-UVs were frequently detected in all matrices including upstream of the urban area in a rural agricultural/woodlot region, suggesting a ubiquitous presence and bioaccumulation of these emerging contaminants. Spatial comparisons were characterized by higher levels of SDPAs downstream compared with the upstream, implying a possible influence of the urban activities on the antioxidant contamination in the sampling area. In sediment, 4,4′-bis(α,αdimethylbenzyl)-diphenylamine (diAMS), dioctyl-diphenylamine (C8C8), and dinonyl-diphenylamine (C9C9) were the most dominant congeners of SDPAs, with concentrations up to 191 ng/g (dry weight, d.w.). Benthic invertebrates Crayfish (Orcoescties spp.) had larger body burdens of SDPAs and BZT-UVs compared to pelagic fish (hornyhead chub (Nocomis biguttatus) and common shiner (Luxilus cornutus)) in the creek and partitioning coefficients demonstrated that sediment was the major reservoir of these contaminants. This is the first report of bioaccumulation and partitioning behaviors of SDPAs and BZT-UVs in freshwater environments.
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exist predominately in their neutral forms in environment.5,6 The estimated log Kow of the target BZT-UVs in the present study are in the range of 5.6−7.8.5,6 SDPAs and BZT-UVs are chemicals with high production and consumption volumes.7,8 The publically available production volumes from the USEPA and REACH for U.S. and Europe are shown in the Supporting Information (SI) (Table S1). All of the SDPAs in this research are part of the USEPA’s High Production Volume (HPV) Challenge Program (USEPA Docket 201−14700A Substituted Diphenylamines Category Justification and Testing Rationale 2003). The high production and wide use of SDPAs and BZT-UVs has triggered an increasing environmental concern on their potential persistence, bioaccumulation and toxicity properties. BZT-UVs have been measured in many environmental samples9 such as surface water,5,6,10wastewater,6,10−14 sewage sludge,15,16 sediments,3,16 soil,17 indoor dust,18,19 mussels,20 marine mammals,21 fish,3,4,22 and bird samples,4 but very few of
INTRODUCTION Substituted diphenylamine antioxidants (SDPAs) are a group of chemicals which present a basic diphenylamine structure with substitutions of alkyl and/or phenyl groups on the benzene rings. SDPAs are widely used in a range of materials, including rubbers, lubricants, fuels, and plastics and other polymers to prevent materials from oxidative degradation.1,2 Usage levels for most applications are typically under 30% by weight.1 These compounds are very weak bases and exist primarily in the neutral form in environment. The experimentally based and relevant environmental physical−chemical properties of these chemicals are still poorly understood. According to Estimation Program Interface (EPI) Suite (V4.11) modeling, the estimated log octanol−water partition coefficients (log Kow) for the target SDPAs in this study range from 5.3 for a butyl substitution to 12.2 for a dinonyl substitution. Benzotriazole UV stabilizers (BZT-UVs) usually share a common 2-hydroxyphenyl benzotriazole structure with alkyl substitutions on the phenol ring. These chemicals absorb full spectrum ultraviolet radiation and are thus used as additives in commodities (including some personal care products) and industrial products to prevent products from light-induced yellowing and degradation.3,4 BZT-UVs are very weak acids with pKa around 7−10 and © 2016 American Chemical Society
Received: Revised: Accepted: Published: 9089
April 11, 2016 July 14, 2016 July 31, 2016 August 1, 2016 DOI: 10.1021/acs.est.6b01796 Environ. Sci. Technol. 2016, 50, 9089−9097
Article
Environmental Science & Technology those studies are from North America.20,23 The half-life of 2tert-butyl-6-(5-chloro-2H-benzotriazol-2-yl)-4-methylphenol (UV326), 2,4-ditert-butyl-6-(5-chloro-2H-benzotriazol-2-yl) phenol (UV327), 2-(2H-benzotriazol-2-yl)-4,6-di-tert-pentylphenol (UV328) and 2-(2H-benzotriazol-2-yl)-4-(1,1,3,3tetramethylbutyl)phenol (UV329) in biosolid-amended soils ranged from 98 to 218 days,17 indicating the persistence of BZT-UVs in environment. This is in agreement with the EPI Suite estimated half-life in soils (120 days). The estimated halflife (EPI Suite) of the target BZT-UVs in the present study is 60 days and 542 days in water and sediment, respectively; but the half-life of BZT-UVs in air would be very short (about 8− 20 h, EPI Suite) due to OH radicals related oxidation. Aquatic organisms may accumulate BZT-UVs from water, sediments and diet. The bioconcentration factor (BCF) of UV328 and UV326 was reported in the range of 54−36 000, depending on the exposure conditions and specific species.3,21 Sediment is estimated as a major exposure source of BZT-UVs to organisms, but the field-based partition coefficients have not been reported thus far. The bioaccumulation of BZT-UVs in a marine aquatic food web in Asia was reported previously3,4,20−22 and each BZT-UV showed different accumulation behavior in the food web.4 These observations implied that the accumulation and metabolic elimination pathways of BZT-UVs are compound- and species-specific. However, the bioaccumulation of these emerging contaminants in freshwater ecosystems is still poorly understood. In addition, BZT-UVs may bind with human serum albumin via hydrogen bonds or electrostatic interactions,24 indicating possibly unique mechanisms for bioaccumulation in hepatic tissues in addition to hydrophobicity-driven partitioning into lipid-rich tissues. BZT-UVs have relatively low acute toxicities,6,9,25−27 but their chronic toxicities have been reported.6,26−28 For example, sex-specific chronic toxicities of 2-(2H-benzotriazol-2-yl)-4,6di-tert-pentylphenol (UV320) in the liver, kidney, spleen and thyroid were observed in rats after 28 days exposure.26 For UV328, adverse effects were observed in the liver, kidney, spleen and thyroid in rats during 3 months daily based repeated-dose of UV328 via diet.27 Liver toxicities (e.g., liver weight increase and hypertrophy of hepatocytes) of 2-(2Hbenzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol (UV234) were observed in rat after repeated-dose via food exposure and the no observable adverse effect level (NOAEL) was set at 50 mg/kg.15,28 These observations indicated potential for endocrine disruption and liver toxicities by BZT-UVs. In contrast, the knowledge of fate processes, partitioning behaviors and impacts of SDPAs in environment is limited. To our knowledge, only a few published studies have detected SDPAs in environmental samples. Galgani et al.29 detected dioctyl-(C8C8) SDPA contamination in natural beach sand in the Mediterranean Sea. Moreover, Thompson et al.30 found that dibutyl- (C4C4) SDPA was recalcitrant to biodegradation in marine sediment, suggesting environmental persistence of SDPAs. The estimated half-lives (EPI Suite) of the target SDPAs are in the range of 1.2−1.3 h, 15−38 days, and 135− 338 days in air, water and sediment, respectively. Some of these substances are currently being assessed under various initiatives of Canada’s Chemicals Management Plan (CMP). However, the environmental occurrence, distribution, bioaccumulation and field-based partitioning data such as sediment−water distribution coefficients (Kd), bioaccumulation factors (BAFs) and biota−sediment accumulation factors (BSAFs) of these chemicals in North America does not exist.
The influence of wastewater treatment plants (WWTP), which are likely a major source of SDPAs, on the distribution of these contaminants is also poorly understood. To these ends, a thorough investigation of the distribution, partitioning, bioaccumulation of SDPAs and BZT-UVs in a typical fresh water system from North America was conducted in the present study. The research objectives were to determine the contamination levels, spatial variations and partitioning coefficients of SDPAs and BZT-UVs in surface water, sediment, fish and benthic invertebrates in an urban creek. The influence of WWTP and urban activities on the contamination of SDPAs and BZT-UVs in the creek was also examined.
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MATERIALS AND METHODS Materials. Chemical information is presented in SI Table S2. The target SDPAs included monobutyl- (C4), C4C4, monooctyl- (C8), monobutyl monooctyl- (C4C8), C8C8, monononyl- (C9), dinonyl-(C9C9), monostyryl- (MS, two isomers), monostyryl octyl- (C8-MS, three isomers) and monostyryl dioctyl-(C8C8-MS) diphenylamines. The target BZT-UVs were UV234 (CAS# 70321−86−7), UV326 (CAS# 3896−11−5), UV327 (CAS# 3864−99−1), UV328 (CAS# 25973−55−1), UV329 (CAS# 3147−75−9), and 2-(2HBenzotriazol-2-yl)-4-(tert-butyl)-6-(sec-butyl) phenol (UV350; CAS# 36437−37−3). The internal standard was 2-allyl-6benzotriazol-2-yl-4-methyl-phenol (ABZTMP; CAS# 2170− 39−0). Please see SI for details. Study Area and Sample Collection. The study area was located in southern Ontario (Canada) within a watershed of 19 km and a drainage area of 143 km2. Approximately 80% of the land within the watershed is productive agricultural land and 10% is woodlot. The creek runs through a small township consisting of 6 km2 and a population of 10 000 people. Though it is primarily an agricultural township, there are several manufacturers in the city, including at least two chemical companies. Six sites along the creek were selected around the city. The reference sites were 4.4 and 2.0 km upstream of the city. A third site (urban site) was immediately downstream of the city’s wastewater treatment plant which provides tertiary treatment of wastewater and an average daily flow capacity of
