Seasonal Variation of Terrigenous Polycyclic Aromatic Hydrocarbons

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Seasonal Variation of Terrigenous PAHs along the Marginal Seas of China: Input, Phase Partitioning, Ocean Current Transport Miao-Lei Ya, Xin-Hong Wang, Yu-Ling Wu, Yong-Yu Li, Jing-Ming Yan, Chao Fang, Yan-Yan Zhao, Ran-Ran Qian, and Xiao-Long Lin Environ. Sci. Technol., Just Accepted Manuscript • DOI: 10.1021/acs.est.7b02755 • Publication Date (Web): 20 Jul 2017 Downloaded from http://pubs.acs.org on July 23, 2017

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Environmental Science & Technology

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Seasonal Variation of Terrigenous PAHs along the Marginal Seas of China: Input,

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Phase Partitioning, Ocean Current Transport

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Miaolei Ya,†,‡ Xinhong Wang,*†,‡ Yuling Wu,†,‡ Yongyu Li,†,‡ Jingming Yan,†,‡ Chao

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Fang,†,‡ Yanyan Zhao,†,‡ Ranran Qian,†,‡ and Xiaolong Lin†,‡

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†

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361102, China.

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‡

State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen College of the Environment & Ecology, Xiamen University, Xiamen 361102, China.

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ABSTRACT： ：

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To study the spatial distributions and seasonal differences of concentrations, source

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identification, and phase partitioning of polycyclic aromatic hydrocarbons (PAHs) in the

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surface water, intensive sampling was carried out along the marginal seas of China in four

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seasons. In the northern South China Sea (SCS), the highest PAH levels occurred in

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summer (July to August) and autumn (October to November). In the East China Sea (ECS)

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and the Yellow Sea, the highest occurred in summer (August) and winter (December). In

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all areas, the lowest PAH levels were found in spring (May to June). The estimated mass

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inventory of PAHs in the surface water (0-5 m) of the northern SCS and ECS accounted

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for less than 8% of PAHs outflow into the offshore environment. That showed the

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consistent seasonal variation with PAHs levels. Land- and ocean-based emissions, surface

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runoff and the open sea water dilution were the most important environmental factors to

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influence the seasonal heterogeneity and the spatial distributions of PAH in the surface

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water. The decline of observed organic carbon normalized partition coefficients in four

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seasons was probably affected by the presence of submicrometer-sized soot particles

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accompanying the PAHs outflow from China.

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Keywords: Input, Seasonal Variation, Phase Partitioning, Ocean Currents, Polycyclic

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Aromatic Hydrocarbons (PAHs), Marginal Seas of China

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Table of Contents (TOC)

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Environmental Science & Technology

1. INTRODUCTION

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Polycyclic aromatic hydrocarbons (PAHs) are derived from the incomplete

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combustion and pyrolysis of fossil fuels or wood and the release of petroleum products.1-3

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China is one of the largest PAHs emitting countries in the world, that is associated with

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rapid economic and industrial growth.4,5 After PAHs and other anthropogenic organic

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pollutants are emitted into the terrestrial environment, surface runoff and atmospheric

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transport can dissipate them rapidly into the coastal ocean system.6,7 Once deposited,

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PAHs enter the oceanic carbon biogeochemical cycles, including the accumulation and

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trophic dilution in the marine food web,8 biotic and abiotic degradation, and settling of

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the more refractory PAHs in deep waters and sediments.9,10

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Marginal seas connect continents with open oceans and they represent a critical

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component of the global source-to-sink system of organic matters.11 As the highest

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cumulative impact area of human activities,12 the marginal seas of China (MC)

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synchronously shows the “sink” of the terrigenous PAHs and the “source” of PAHs in the

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Western Pacific. The sink-effects in water systems have been observed also in the

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Sognefjord in Norway.13 That is subject to both land- and ocean-based anthropogenic

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drivers.12 However, accompanying pollutants in the MC can transport to the Western

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Pacific under the combined actions of the ocean circulations,14 monsoon movement,15,16

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and deposition/volatilization processes.9-11

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Strong seasonal heterogeneity of the occurrence of PAHs was reported in the surface

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aquatic environment.17,18 That might be mainly attributed to the combined effects of a

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number of hydrological and meteorological factors,19 such as terrigenous PAHs emissions,

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the ability of surface runoff and atmospheric transport,20 and the self-cleaning ability

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through biotic and abiotic degradation.21 PAHs emission in China exhibited significantly

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seasonal variation, with larger emission in the winter.22 Therefore, if the seasonal

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variation of PAHs in the surface water of the MC are consistent with the seasonal PAHs

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emissions or directly controlled by the intensity of transport processes and hydrological

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conditions, that is worthy of study.

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PAHs are redistributed through the atmospheric transport and the ocean currents

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owing to their semivolatility.9,14 Ocean currents are the key driving factors influencing the

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transport and distribution of terrigenous PAH and other organic pollutants in the coastal

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ocean.14,23 Asia is the most significant monsoon region in the world,16,24 and ocean

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currents accordingly exhibit obvious seasonal features.11,25 Therefore, based on the

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statement above, intensive sampling was carried out along the MC (18-36° N and

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109-127° E) in four monsoon periods (spring, summer, autumn and winter) for the first

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time. The sampling areas contained the whole northern South China Sea (SCS), the whole

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East China Sea (ECS) and one section of the Yellow Sea (YS). We expected to provide a

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key basis for more in-depth study of the existence and land-ocean interaction of PAHs,

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and allow a better understanding of the global cycle of PAHs. The detail objectives of this

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study in the followings: (1) the seasonal differences of levels, mass inventories,

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compositions, sources and phase partitioning of PAHs; (2) the roles of the seasonal ocean

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currents on the spatial distributions and transports of PAHs; (3) the source identification

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and particle-water partitioning of PAHs and the possible influencing factors.

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2. MATERIALS AND METHODS

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2.1. Cruise and Sampling. During 2009–2011, a total of 94, 121, 79 and 87 sea

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surface water samples were taken from the R/V Dong Fang Hong 2 along the whole

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northern SCS, ECS and a section in the YS from 18° N to 36° N, in spring (May to June),

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summer (July to August), autumn (October and November) and winter (December to

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January), respectively (see Supporting Information Table S1, Figures 1 and S1, SI).

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Active water sampling procedures were described in our previous papers.26,27 In brief,

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less than 30 L of sea surface water (SSW, about 1 m depth) were pumped into a

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pre-cleaned sealed stainless-steel barrel. SSW samples were filtered by glass fiber filters

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(GF/F, Whatman, O. D. 142 mm, 0.75 µm, pre-burned at 450°C) using a vermicular

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system. After being pretreated by methanol followed by ultrapure water (18.25 MΩ·cm,

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Millipore Company, USA) and spiking with five deuterated PAHs as surrogate standards

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(including naphthalene-d8, acenaphthene-d10, phenanthrene-d10, chrysene-d12, and

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perylene-d12), double parallel solid-phase extraction (SPE, SUPELCLEAN ENVI-18 0.5

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g) cartridges were used to extract the dissolved organic matters (