Occurrence and Fate of Benzophenone-Type UV Filters in a Tropical

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Occurrence and fate of benzophenonetype UV filters in a tropical urban watershed Feijian Mao, Luhua You, Martin Reinhard, YiLiang He, and Karina Yew-Hoong Gin Environ. Sci. Technol., Just Accepted Manuscript • DOI: 10.1021/acs.est.7b05634 • Publication Date (Web): 05 Mar 2018 Downloaded from http://pubs.acs.org on March 7, 2018

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Environmental Science & Technology

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Occurrence and fate of benzophenone-type UV filters in a tropical urban watershed

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Feijian Mao 1, Luhua You 1, Martin Reinhard 2, Yiliang He 3, Karina Yew-Hoong Gin 1,4,*

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1 Engineering Drive 2, E1A 07-03, Singapore 117576, Singapore

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Department of Civil and Environmental Engineering, National University of Singapore,

Department of Civil and Environmental Engineering, Yang & Yamasaki Environment &

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Energy Building, 473 Via Ortega, Stanford University, Stanford, California 94305, USA

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Shanghai 200240, China

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Engineering Drive 1, #02-01, Singapore 117411, Singapore

School of Environmental Science and Engineering, Shanghai Jiao Tong University,

NUS Environmental Research Institute, National University of Singapore, 5A

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* Corresponding author. Tel.: +65 65168104; E-mail address: [email protected]

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ACS Paragon Plus Environment

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Table of Content

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Abstract: The study investigated the occurrence and fate of seven benzophenone-type

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UV filters (i.e., 2,4-dihydroxybenzophenone (2,4OH-BP), 2,2’,4,4’-

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tetrahydroxybenzophenone (2,2’,4,4’OH-BP), 2-hydroxy-4-methoxybenzophenone

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(2OH-4MeO-BP), 2,2’-Dihydroxy-4,4’-dimethoxybenzophenone (2,2’OH-4,4'MeO-BP),

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2,2’-Dihydroxy-4-methoxybenzophenone (2,2’OH-4MeO-BP), 4-hydroxybenzophenone

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(4OH-BP) and 4,4’-dihyroxybenzophenone (4DHB)) in a tropical urban watershed

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consisting of five major tributaries that discharge into a well-managed basin. Total

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benzophenone concentrations (∑ C ) varied from 19 to 230.8 ng L-1 in overlying bulk

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water, 48 to 115 ng L-1 in pore water, 295 to 5813 ng g-1 dry weight (d.w.) in suspended

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solids, and 6 to 37 ng g-1 d.w. in surficial sediments, respectively. The tributaries (∑ C :

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19-231 ng L-1) were the main source of benzophenone compounds entering the basin

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(∑ C : 20-81 ng L-1). In the water column, the vertical concentration profile in the

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aqueous phase was uniform while concentrations in the suspended solids decreased

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with depth. Different distribution profiles were also identified for benzophenones in

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suspended solids and sediments. A preliminary risk assessment suggested that the

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seven BPs were unlikely to pose ecotoxicological risks to local aquatic organisms

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except for 2OH-4MeO-BP in the case of an intermittent release.

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Keywords: Benzophenones; bulk water; suspended solids; Pore water; Sediments

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1 Introduction

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A variety of benzophenone compounds (BPs) have been used as ultraviolet (UV) light

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absorbers in personal care products (e.g. sunscreens, shampoos, body lotions and hair

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sprays) and synthetic products such as insecticides, plastic bags and paints that are

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exposed to sunlight.1–3 In Australia, Europe and China, 2-hyrdoxy-4-

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methoxybenzophenone (2OH-4MeO-BP) has been approved for use as an active

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ingredient in sunscreens at concentrations up to 10%.4 Other countries have permitted

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the use of 2,4-dihydroxybenzophenone (2,4OH-BP), 2,2’,4,4’-

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tetrahydroxybenzophenone (2,2’,4,4’OH-BP), 2,2’-Dihydroxy-4,4’-

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dimethoxybenzophenone (2,2’OH-4,4'MeO-BP), and 2,2’-dihydroxy-4-methoxy-

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benzophenone (2,2’OH-4MeO-BP) in sunscreens.4,5 Due to extensive use, BP-type UV

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filters can enter water environments directly from recreational activities (e.g. bathing and

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swimming) and indirectly from sewage discharges (e.g. wastewater treatment plant

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effluent and domestic washing).2,6,7

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Various studies have demonstrated the estrogenic activity of BPs and thus they are

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currently regarded as potential endocrine disrupting chemicals.6,8,9 For example, studies

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have demonstrated the weak estrogenicity of 2OH-4MeO-BP, one of the most popular

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congeners.6 In addition, 2OH-4MeO-BP can form several metabolic byproducts with

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estrogenic activities, such as 2,2’OH-4MeO-BP and 2,4OH-BP.6 In addition, 2,4OH-BP

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is speculated to be associated with endometriosis, an estrogen-dependent disease.10

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Other benzophenone derivatives, such as 4-hydroxybenzophenone (4OH-BP) and


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2,2’,4,4’OH-BP, exhibited higher estrogenic activity than 2OH-4MeO-BP.11 Apart from

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endocrine disrupting properties, BPs can also cause coral bleaching and disrupt gene

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expression in zebrafish.12–14

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Given their wide ranging physicochemical properties, BPs can be accommodated in

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different environmental matrices (e.g. bulk water, suspended solids (SS), pore water

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and sediments) in aquatic ecosystems.15–18 Previous studies have detected the

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concentrations of BPs in surface water and sediments, with levels typically ranging from

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ng L-1 to low µg L-1 for water samples and in the low ng g-1 range for sediments (dry

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weight).2,7,19,20 In contrast, studies on the detection of BPs in SS and pore water are

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limited.15,17 BPs associated with SS are expected to influence both the quality of the

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water column (via sorption and desorption) and benthic sediments (via sedimentation

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and resuspension).17,21 Sediment-pore water partitioning and diffusion across the

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sediment-water column boundary are important processes that govern the transport,

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fate and toxicity of BPs in aquatic systems.22,23 Since the fate of BPs in a surface water

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body is linked to the fate and transport of particles (SS and sediments), it is essential to

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study their occurrence concurrently in all relevant environmental compartments: bulk

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water, SS, surficial benthic sediments and sediment pore water.

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Thus, the primary objectives of this investigation were to quantify the concentrations of

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seven targeted BP-type UV filters in a tropical urban watershed. BPs included were

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2,4OH-BP, 2,2’,4,4’OH-BP, 2OH-4MeO-BP, 2,2’OH-4,4’MeO-BP, 2,2’OH’4MeO-BP,

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4OH-BP and 4,4’-dihyroxybenzophenone (4DHB). BPs were quantified in the four


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environmental compartments (dissolved in bulk water and sorbed to SS in the water

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column and dissolved in pore water and sorbed to surficial sediments). The approach

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was to investigate the temporal and spatial variations of the target BPs and to evaluate

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the data with respect to sorption. Environmental risk assessment was performed to

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assess the ecotoxicological risks posed by these BP-type UV filters. Results are useful

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for assessing the environmental risk of BPs and elucidating their fate in aquatic

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environments.

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2 Materials and methods

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2.1 . Chemicals and reagents

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The seven targeted BPs (i.e., 2,4OH-BP, 2,2’,4,4’OH-BP, 2OH-4MeO-BP, 2,2’OH-

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4,4’MeO-BP, 2,2’OH’4MeO-BP, 4OH-BP and 4DHB) and benzophenone-d10 (BP-d10,

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internal standard) of high purity grade (>99.9%) were purchased from Sigma-Aldrich

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(Sigma-Aldrich, Singapore). Some environmentally important physicochemical

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properties are given in Supporting Information (SI) Table S1. Individual stock solutions

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(1000 mg L-1) were prepared in methanol from powder and stored in the dark at -20 ℃.

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A mixture of all analytes was obtained by combining aliquots of the stock solutions.

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Other chemical reagents and solvents, such as HPLC grade methanol, were of high

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purity grade. Ultra-pure water was produced by a Milli-Q system (Sartorius, Singapore).

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2.2 . Sampling campaign

113 114

The watershed and sampling sites have been described elsewhere and are presented

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in Figure S1.24–26 Briefly, the study area (about 10, 000 ha) is a tropical urban watershed

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located in Singapore, accounting for about one-sixth of Singapore’s land area. The

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watershed consists of a main water body (hereinafter “basin”), which receives the

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discharge of five major tributaries. Water samples were collected in 1-L amber water

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bottles at three sites (i.e., S1, S2 and S3) located in the basin: at 0.1 m (top), about 2.5

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m (middle) and about 5 m below the water surface (near the bottom). At the 5 tributaries

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(identified as SR, SC, RC, KR and GR), grab surface water samples were collected

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(one sample per tributary). Surficial benthic sediment samples were collected at the

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eight sampling sites from the top 10 cm with a stainless steel grabber. A total of 5

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quarterly sampling events were conducted starting from December 2014 to December

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2015. This was to capture the seasonal characteristics covering the northeast (NE)

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monsoon (December-early March), inter-monsoon (late March-May, October-November)

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and southwest (SW) monsoon (June-September) periods. All the samples were kept in

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an ice-packed container during transport to the laboratory. The samples were stored in

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a cold room (4 ℃) in the dark.

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2.3 . Sample pre-treatment and extraction

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BPs in the aqueous phases (i.e., bulk water and pore water) and solid matrices (i.e., SS

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and sediments) were analyzed using a combination of solid phase extraction (SPE),


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ultrasound-assisted extraction and high-performance liquid chromatography coupled

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with tandem mass spectrometry (HPLC-MS/MS). Detailed description about the

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analytical procedures and method validation are described in the SI.

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2.4 . Evaluation of distribution of benzophenones in dissolved and solid phases

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The fraction of BPs associated with SS and sediments (ΦSS and ΦSed, %) was

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calculated with the following equations:

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= /( + ) ∗ 100%

(1)

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= /( + ) ∗ 100%

(2)

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where, , , and are the mass (in ng) of BPs in SS, bulk water,

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sediments and pore water, respectively. Detailed derivations and calculation are

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provided in the SI.

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2.5 . Environmental risk assessment

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Risk quotients (RQs) of BP-type UV filters were quantified with the ratio between the

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measured environmental concentrations (MECs) in the dissolved phase (bulk water and

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pore water) and the predicted no-effect concentrations (PNECs) (Equation (3)). The RQ

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of a water sample (i.e., RQTotal) was defined as the sum of RQs of each BPs (RQi)

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following the rule of concentration addition (Equation (4)).27,28

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= /

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!"#

= ∑%$&' $ = ∑%$&' $ /$

(3) (4)

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MEC values of BP-type UV filters were obtained from the present study. PNEC values

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were derived from available ecotoxicological data with an assessment factor (Table S2).

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The assessment factors were employed to compensate for the uncertainties in inter-

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and intra-species variations, acute and chronic toxicity and the extrapolation of

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laboratory data to the field.3,29 They were calculated following the European

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Commission guidelines.30 To reflect the risk under the worst condition, the highest MEC

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and the lowest PNEC of each BPs were employed in the risk assessment.7,28,29 RQ

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based ranking criteria were applied to interpret the risk classification: “unlikely to pose

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risk” for QR < 0.01; “low risk” for 0.01 < RQ

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88%) and the basin samples (> 77.8%) (Table 1). In the tributaries, total BP

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concentrations (∑ C ) were significantly higher (19-230.8 ng L-1) than the basin (20.4-

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81 ng L-1) (Mann-Whitney test, p < 0.05), consistent with the tributaries being the main

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source of BPs. Concentrations of 2,2’,4,4’OH-BP (0.8-109.2 ng L-1) and 2OH-4MeO-BP

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(2.3-122.6 ng L-1) in tributaries varied the most. The high concentrations of the two BPs

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may be a result of their wide application in sunscreen products (Table S3). Another

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possibility may be due to their different application characteristics in commercial

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products. For example, 2,2’,4,4’OH-BP, a congener commonly found in products more

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related with daily life (e.g. nail polish, fragrance and shampoo), may have a higher

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possibility of anthropogenic release (via sewage) than 2,4OH-BP, a congener which is

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more related with products for beauty purposes (e.g. nail polish, nail treatment and

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polish remover).31,32 In contrast to 2,2’,4,4’OH-BP and 2OH-4MeO-BP, concentration

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levels of the other BP congeners (i.e., 2,4OH-BP, 2,2’OH-4MeO-BP, 4OH-BP and

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4DHB) were relatively uniform as the highest detected concentration was less than 30

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ng L-1. The discrepancy in concentration range was a result of peak values for selected

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congeners for certain sampling events (Figure S2). Similar release events were

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observed previously for some compounds (e.g. caffeine, bisphenol A and

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perfluorononanoic acid) within this study area.26,33 These peak releases indicate that the

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tributaries are subjected to variable contamination sources. As Singapore’s river-

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reservoir systems are isolated from sewer systems, higher concentrations of BPs in

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tributaries could possibly originate from other sources, such as leaking sewer pipelines


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and runoff from uncontrolled surface sites.7,20,25,26,34 These variable sources could

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partially explain the wide concentration ranges observed in the tributaries.

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Compared to the tributaries, the concentration ranges of the total BPs (20.4-81 ng L-1) in

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the basin were smaller, likely due to mixing and dilution and the absence of point

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sources that impact the basin. For individual compounds, only 2OH-4MeO-BP had a

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relatively wide concentration range (4.5-56.1 ng L-1) while the remaining six BPs were

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characterized by a smaller range, with a maximum level of 12.3 ng L-1 in the case of

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2,2’,4,4’OH-BP. For each compound, the median levels in bulk waters from the basin

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were 9.1-57.8% lower than that from the tributaries. In the basin water column,

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concentration differences at the three layers were statistically insignificant (Figure 1A,

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Mann-Whitney test, p > 0.05), indicating that the water in the basin was generally well

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mixed.25,33

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For a better comparison, the worldwide occurrence of various BP-type UV filters in fresh

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surface water is summarized in Table S4 along with our results. Among all the members

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of the BP family, 2OH-4MeO-BP is the most intensively studied congener worldwide

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(Table S4). The measured 2OH-4MeO-BP concentrations in the present study were

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generally lower than a previous study in the same study area.26 In addition, higher levels

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(127-166 ng L-1) were also reported for 2OH-4MeO-BP in Bangkok, Thailand.7 The high

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contamination levels may be correlated with high usage patterns of 2OH-4MeO-BP

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containing products, such as sunscreens since our study area and Bangkok are both

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located in tropical regions that prompt the use of sun-protecting lotions.4,35


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Total BPs concentration in pore water were 1.2 times higher than overlying water in

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terms of median levels (Table 1, Table 2). The total BP concentration ranged from 48.3

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to 115.1 ng L-1 with a median concentration of 63.5 ng L-1 (Table 2). The highest

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concentrations (up to 40 ng L-1) were observed for 2,2’OH-4,4’MeO-BP and 4OH-BP,

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while the lowest was for 4DHB (3.8 ng L-1). Based on median concentrations, the

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predominant BPs were 4OH-BP (median concentration: 16.0 ng L-1), 2OH-4MeO-BP

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(10.7 ng L-1) and 2,2’OH-4MeO-BP (10.5 ng L-1).

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Since this is the first study reporting the concentration of BPs in pore water, no literature

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data are available for comparison. We focused on the concentration differences

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between overlying water and pore water, in order to understand the dynamic

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interactions between the water column and the benthic layer. The median

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concentrations of five BPs (i.e., 2,2’,4,4’OH-BP, 2OH-4MeO-BP, 2,2’OH-4,4’MeO-BP,

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2,2’OH-4MeO-BP and 4OH-BP) were higher in pore water than in overlying water

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(Figure 1A). This behavior is consistent with the hypothesis that SS have a higher

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sorption capacity than bottom sediments, perhaps because of a higher surface area-to-

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volume ratio in suspended particles when compared to sedimentary particles. Higher

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levels of BPs in pore water may partially due to the hydrophobicity of these compounds,

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coinciding with the fact that pore water in sediments is an organic-rich matrix.36–38 It

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should be pointed out that a number of studies have suggested that pore water could be

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a secondary contamination source for the overlying water column.39–41 Contrary to these

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five BPs, the median concentration of 4DHB was higher in the overlying water than pore


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water (Figure 1A), suggesting that this chemical may be transported from overlying

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water to pore water via diffusion. Similar observations have been reported elsewhere

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(Table S5). Thus, it is difficult to ascertain the role of pore water in influencing the

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overall environmental behavior of organic contaminants in water environments and

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more effort is needed to further characterize the nature of sediments and the role

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organic carbon may play in influencing contaminant flux.

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3.2 . BPs in suspended solids and sediments

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The total BP concentrations in SS ranged from 294.5 to 5813 ng g-1 d.w. in the

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tributaries and more narrowly from 756.2 to 1834 ng g-1 d.w. in the basin (Table 1). The

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detection frequencies in the SS of the tributaries ranged from 40% (2,4OH-BP) to 100%

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for 2OH-4MeO-BP, 2,2’OH-4,4’MeO-BP, 4OH-BP and 4DHB. Concentrations of specific

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BPs in SS ranged more widely in the in the tributaries than in the basin (Table 1). This

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could be due to highly variable BP input and variable SS concentrations and

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composition in the tributaries and attenuation due to dilution and mixing in the basin.

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The total and median BP loads carried by the SS of the tributaries were significantly

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lower than in the basin (Table 1, Mann-Whitney test, p < 0.05). This trend agrees with

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the reduced BP concentrations in the bulk water samples, perhaps due to the stronger

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sorption capacity of the basins SS (Table 1). This is possible because tributary flows

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contain a higher content of poorly sorbing gravel and sand particles and a smaller

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amount of phytoplankton (as indicated by chlorophyll, Table S6, Figure S5) when

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compared to the basin.

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Sediments are often regarded as the final repository for hydrophobic organic

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contaminants. In the benthic sediment samples, the concentration range (5.8-37 ng g-1

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d.w.) and median level (13.7 ng g-1 d.w.) of total BPs were much lower when compared

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to SS (Table 1, Table 2). The highest concentrations were measured for 4OH-BP (9.3

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ng g-1 d.w.) and 4DHB (9.1 ng g-1 d.w.). Some of the congeners, such as 2,4OH-BP,

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2OH-4MeO-BP and 2,2’OH-4,4’MeO-BP, were measured to be less than 4 ng g-1 d.w.

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The concentrations of the seven BPs in the tributary sediments were comparable to that

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in the basin sediments (Mann-Whitney test, p > 0.05). Compared to bulk water, less

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attention has been paid to BPs in sediments and 2OH-4MeO-BP again was the most

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commonly studied congener in the BP family (Table S7). 2OH-4MeO-BP levels in the

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present study were comparable to levels found in China (0.16-1.07 ng g-1 d.w.), USA

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(0.73-4.66 ng g-1 d.w.) and Chile (n.d.-2.96 ng g-1 d.w.). In contrast, sediments in some

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other countries (i.e., South Korea, Japan and Germany) were less contaminated by

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2OH-4MeO-BP compared to our study. Aside from 2OH-4MeO-BP, other BP derivatives

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were also detected in sediments (Table S7), with relatively higher concentrations

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detected in the present study potentially due to the high local usage of sunscreens.

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Like BPs in dissolved phase, concentrations of BPs in SS collected from three different

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layers and benthic sediments are shown in Figure 1B. Unlike overlying water, the

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deeper particles in the water column tended to have less BPs than surface particles and

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the contamination levels of BPs in sediments were minimal when compared to SS. This

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may imply that the SS release the loaded BPs as they settle. Reduced sorption capacity

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could be one possible explanation for the reduction in BPs loading. It is generally


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accepted that particles with bigger size tend to reside lower in the water column.42,43 As

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particles further reach the benthic sediment layer, they may also tend to aggregate to

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form bigger particles such as larger sand and gravel. Thus, the surface area-to-volume

300

ratio of the particles will tend to decrease vertically, leading to a lower sorption capacity.

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In addition, similar to the observation from tributaries and the basin, the differences in

302

particle compositions in different layers may also lead to varying sorption capacities. To

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be specific, particles in the upper layer generally contain more phytoplankton

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(chlorophyll concentration in Table S6, Figure S5), which is lipid-rich in nature, resulting

305

in a higher sorption capacity.44 The second possibility is that BPs in the sediment phase

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may undergo biodegradation processes which result in the lower concentration of BPs

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in sediments than that in SS. For example, 2OH-4MeO-BP was proven to be

308

enzymatically transformed to 2,4OH-BP and 2,2’OH-4MeO-BP.45 In addition, the

309

biodegradation of 2OH-4MeO-BP is more favorable under anoxic conditions (half-life:

310

4.2 d) than oxic conditions (half-life: 10.7 d), where the former is more likely to occur at

311

lower depths.46

312 313

3.3 . Temporal pattern

314 315

The seasonal influence of Singapore’s tropical rainforest climate (NE and SW monsoon

316

separated by inter-monsoon seasons) on the occurrence of BPs in the watershed was

317

examined in Table S8, where the median concentrations and the ranges of the seven

318

BPs are presented. The distribution of the seven BPs in the four phases was highly

319

variable, indicating that the seasonal effect (especially rainfall) on the occurrence of this


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group of chemicals is negligible. This agrees with a previous report that Singapore’s

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tropical climate (e.g. uniform temperatures and abundant rainfall) did not affect the

322

occurrence of selected personal care products (PPCPs). However, seasonal differences

323

were reported for UV filters elsewhere, typically those with significant seasonal

324

temperature variations (e.g. Korea).47,48 In these studies, the observed seasonal

325

variations may manifest the anthropogenic sources of these chemicals, such as the use

326

of sunscreens and other personal care products during the summer period. It is noted

327

that Singapore is a tropical country and therefore, application of sunscreen would likely

328

be year-round.

329 330

3.4 . Solid-solution distribution of BPs in the water column and sediments

331 332

To further understand the behavior of BPs in the water column and bottom sediment,

333

the distribution of individual BPs between dissolved and particulate phases both in the

334

water column and bottom sediment phase was calculated based on paired

335

concentrations over the entire sampling period (Figure 2). In the water column, 2,4OH-

336

BP and 4DHB were predominately detected in bulk water, accounting for 74.8% and 89%

337

of the total mass, respectively. The remaining five BPs distributed almost uniformly (45-

338

59%) in the two phases in the water column (bulk water and SS). However, the

339

distribution pattern was different in the sediment layer where a major proportion of the

340

target BPs (> 58%) was detected in pore water. The obtained percentages agreed with

341

a previous observation that PPCPs can be predominantly detected whether in dissolved

342

phase or solid phase.49 Hence, routine monitoring campaigns may underestimate the


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actual contamination levels in water samples (with filtration) and overestimate sediment-

344

bound contaminant levels (without pore water separation).

345 346

3.5 . Environmental risk assessment

347 348

A preliminary environmental risk assessment was conducted to identify the

349

ecotoxicological potential of BPs to the aquatic organisms in the worst-case scenario,

350

i.e., highest detected concentrations (Table 3). In bulk water, 2OH-4MeO-BP posed a

351

medium risk to the organisms and 2,2’,4,4’OH-BP posed a low risk. The remaining BPs

352

were unlikely to pose risk to organisms reside in the water column. It is noteworthy that

353

the obtained RQs of 2OH-4MeO-BP and 2,2’,4,4’OH-BP were a result of intermittent

354

peak values (Figure S2). These peaks values greatly dedicated the overall medium risk

355

caused by the seven BPs in the bulk water (RQTotal = 0.52). Similarly, with an RQTotal of

356

0.11, BPs posed a medium risk to benthic organisms, which is mainly contributed by

357

2OH-4MeO-BP (RQ = 0.09, low risk). The remaining six BPs in pore water were unlikely

358

to trigger risk to benthic organisms.

359 360

Various studies have evaluated the ecotoxicological risks of BPs using the RQ method.

361

However, risk data pertaining to tropical regions was limited. Compared to our results,

362

Fent et al (2010a) reported a lower RQ of 0.07 (low risk) for 2OH-4MeO-BP based on

363

ecotoxicological data on chronic effects in fish, as well as acute effects in Daphnia

364

magna. Similarly, 2OH-4MeO-BP was reported to have a small potential to pose

365

adverse effects in Spain.51 However, this compound may pose significant risks as


17


Page 18 of 32

366

indicated previously 52. As for other types of BPs, 2,4OH-BP was previously reported to

367

be unlikely to pose any risk, agreeing with our results.53 The same study revealed that

368

2,2’,4,4’OH-BP posed no risk.53

369 370

To the best of our knowledge, this is one of first studies conducting the risk assessment

371

for four types of BPs (i.e., 2,2’OH-4,4’MeO-BP, 2,2’OH-4MeO-BP, 4OH-BP and 4DHB).

372

In addition, we reported the accumulative risk (RQTotal) of several types of BPs for the

373

first time. The RQTotal was calculated assuming additive interaction.50 The evaluation of

374

the total risk posed by various BP-type UV filters is practically important as these

375

chemicals generally occur in mixtures. However, it is worth mentioning that the risk

376

assessment here was conducted based on limited ecotoxicological data (e.g. only one

377

datum for 2,2’,4,4’OH-BP, 2,2’OH-4,4’MeO-BP, 2,2’OH-4MeO-BP and 4DHB).

378

Therefore, more studies regarding the toxicity of single and mixture BP-type UV filters

379

are needed for a better understanding of the actual risk of BP-type UV filters.

380 381

Supporting information

382 383

This supporting information contains additional information on sampling map, sample

384

process, instrumental analysis, quality assurance and quality control, detailed derivation

385

and calculation, structure and physicochemical properties of BP-type UV filters, reported

386

ecotoxicological data on BP-type UV filters, literature data on occurrence of various

387

organic contaminants, concentrations of BP-type UV filters, water quality data, and SS


18

Page 19 of 32


388

on filters in the present study. It is available free of charge on the ACS Publication at

389

http: //pubs.acs.org.

390 391

Author information

392 393

Corresponding Author: *Tel.: +65 65168104; E-mail address: [email protected] (K.

394

Y-H. Gin)

395 396

Note

397 398

The authors declare no competing financial interest.

399 400

Acknowledgments

401 402

This research/project is supported by the National Research Foundation, Prime

403

Minister’s Office, Singapore under its Campus for Research Excellence and

404

Technological Enterprise (CREATE) programme and the Singapore Ministry Education

405

Academic Research Fund R-302-000-088-750. Financial support was also provided by

406

the China Scholarship Council (CSC) and National University of Singapore (NUS). We

407

are grateful to PUB, Singapore's national water agency for providing logistical support in

408

this study.

409


19


410

Page 20 of 32

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Table 1. Detection frequency, median and range of BP concentrations in bulk water and suspended solids from the tributaries and the basin Compounds Tributary Basin Ratiob DF (%) Range Median DF (%) Range Median -1 Bulk water (ng L ) Total BPsa 19.0-230.8 45.2 20.4-81.0 28.7 1.57 2,4OH-BP 100.0% 1.0-18.2 5.4 100.0% 1.4-5.2 3.2 1.69 2,2’,4,4’OH-BP 100.0% 0.8-109.2 7.9 100.0% 1.6-12.3 3.3 2.39 2OH-4MeO-BP 100.0% 2.3-122.6 8.4 100.0% 4.5-56.1 6.9 1.22 2,2’OH-4,4’MeO-BP 96.0%

Occurrence and Fate of Benzophenone-Type UV Filters in a Tropical

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