Microplastics (MPs) in marine and terrestrial environments have been intensively studied, but the dynamics of airborne MPs remains limited. Existing studies on atmospheric MPs are mostly derived from collection of atmospheric deposition, whereas direct measurements of airborne MPs are scarce. However, the abundance of airborne MPs is more relevant for evaluating human inhalation exposure risk. Herein, airborne MPs in indoor and outdoor environments from urban and rural areas of a coastal city in eastern China were investigated. MP concentrations (mean±SD) in indoor air (1583 ± 1180 n/m 3 ) were an order of magnitude higher than outdoor air (189 ± 85 n/m 3 ), and airborne MP concentrations in urban areas (224 ± 70 n/m 3 ) were higher than rural areas (101 ± 47 n/m 3 ). MPs smaller than 100 µm dominated airborne MPs, and the predominant shape of airborne MPs was fragments, as opposed to fibers. The larger MP size fractions contained a higher proportion of fibers, whereas the smaller size fractions were nearly exclusively composed of fragments. The health risk caused by ubiquitous airborne MPs should not be discounted as the maximum annual outdoor exposure of airborne MPs can reach 1 million/year, while indoor exposure may be even higher due to higher indoor airborne MP concentrations.

18The occurrence of organophosphate ester (OPE)

Abstract. Turbulence observed during the Physics of Stratocumulus Top (POST) research campaign is analyzed. Using in-flight measurements of dynamic and thermodynamic variables at the interface between the stratocumulus cloud top and free troposphere, the cloud top region is classified into sublayers, and the thicknesses of these sublayers are estimated. The data are used to calculate turbulence characteristics, including the bulk Richardson number, mean-square velocity fluctuations, turbulence kinetic energy (TKE), TKE dissipation rate, and Corrsin, Ozmidov and Kolmogorov scales. A comparison of these properties among different sublayers indicates that the entrainment interfacial layer consists of two significantly different sublayers: the turbulent inversion sublayer (TISL) and the moist, yet hydrostatically stable, cloud top mixing sublayer (CTMSL). Both sublayers are marginally turbulent, i.e., the bulk Richardson number across the layers is critical. This means that turbulence is produced by shear and damped by buoyancy such that the sublayer thicknesses adapt to temperature and wind variations across them. Turbulence in both sublayers is anisotropic, with Corrsin and Ozmidov scales as small as ∼ 0.3 and ∼ 3 m in the TISL and CTMSL, respectively. These values are ∼ 60 and ∼ 15 times smaller than typical layer depths, indicating flattened large eddies and suggesting no direct mixing of cloud top and free-tropospheric air. Also, small scales of turbulence are different in sublayers as indicated by the corresponding values of Kolmogorov scales and buoyant and shear Reynolds numbers.

[1] Eighteen polycyclic aromatic hydrocarbons (PAHs) were simultaneously measured in surface seawater and boundary layer air from the North Pacific toward the Arctic Ocean during the Fourth Chinese National Arctic Research Expedition in the summer of 2010. Atmospheric Σ 18 PAH ranged from 910 to 7400 pg m À3 , with the highest concentrations observed in the coastal regions of East Asia. Correlations of PAHs' partial pressures versus inverse temperature were not significant, indicating the importance of ongoing primary sources on ambient PAH levels in the remote marine atmosphere. The relatively high atmospheric concentrations observed in the most northerly latitudes of the Arctic Ocean suggest the influence of regional sources. For example, higher levels of particle-bound PAHs were observed in the air of the Arctic Ocean than the North Pacific, indicating forest fire and/or within-Arctic sources. Concentrations of PAHs in surface seawater were within a range of 14-760 pg L À1 and generally decreased with increasing latitude. The observed air-sea gas exchange gradients strongly favored net deposition of PAHs along the entire cruise, with increasing deposition with increasing latitude, while the particle-bound dry deposition fluxes (particularly for the high molecular weight PAH) were highest at sample sites close to East Asia. Based on characteristic PAH ratios, atmospheric PAHs originated from the combustion of biomass or coal, while the ratios observed in seawater reflected a mixture of sources. Given the dominance of primary emissions to the atmosphere and the relatively fast removal of PAHs from the water column, then PAHs will continue to load into the surface waters of the remote marine environment via atmospheric deposition.

[1] Surface seawater and boundary layer air samples were collected on the icebreaker Xuelong (Snow Dragon) during the Fourth Chinese Arctic Research Expedition (CHINARE2010) cruise in the North Pacific and Arctic Oceans during 2010. Samples were analyzed for organochlorine pesticides (OCPs), including three isomers of hexachlorocyclohexane (HCH), hexachlorobenzene (HCB), and two isomers of heptachlor epoxide. The gaseous total HCH (SHCHs) concentrations were approximately four times lower (average 12.0 pg m À3 ) than those measured during CHINARE2008 (average 51.4 pg m À3 ), but were comparable to those measured during CHINARE2003 (average 13.4 pg m À3 ) in the same study area. These changes are consistent with the evident retreat of sea ice coverage from 2003 to 2008 and increase of sea ice coverage from 2008 to 2009 and 2010. Gaseous b-HCH concentrations in the atmosphere were typically below the method detection limit, consistent with the expectation that ocean currents provide the main transport pathway for b-HCH into the Arctic. The concentrations of all dissolved HCH isomers in seawater increase with increasing latitude, and levels of dissolved HCB also increase (from 5.7 to 7.1 pg L À1 ) at high latitudes (above 73 N). These results illustrate the role of cold condensation processes in the transport of OCPs. The observed air-sea gas exchange gradients in the Arctic Ocean mainly favored net deposition of OCPs, with the exception of those for b-HCH, which favored volatilization.

Eighteen polycyclic aromatic hydrocarbons (PAHs) were measured in surficial sediments along a marine transect from the North Pacific into the Arctic Ocean. The highest average Σ 18 PAHs concentrations were observed along the continental slope of the Canada Basin in the Arctic (68.3 ± 8.5 ng g-1 dw), followed by sediments in the Chukchi Sea shelf (49.7 ± 21.2 ng g-1 dw) and Bering Sea (39.5 ± 11.3 ng g-1 dw), while the Bering Strait (16.8 ± 7.1 ng g-1 dw) and Central Arctic Ocean sediments (13.1 ± 9.6 ng g-1 dw) had relatively lower average concentrations. The use of principal components analysis with multiple linear regression (PCA/MLR) indicated that on average oil related or petrogenic sources contributed ~42% of the measured PAHs in the sediments and marked by higher concentrations of two methylnaphthalenes over the non-alkylated parent PAH, naphthalene. Wood and coal combustion contributed ~32%, and high temperature pyrogenic sources contributing ~26%. Petrogenic sources, such as oil seeps, allochthonous coal and coastally eroded material such as terrigenous sediments particularly affected the Chukchi Sea shelf and slope of the Canada Basin, while biomass and coal combustion sources appeared to have greater influence in the central Arctic Ocean, possibly due to the effects of episodic summertime forest fires.

Spatial distributions of perfluoroalkyl substances (PFASs) were investigated in surface waters in Shanghai, Jiangsu and Zhejiang Provinces of eastern China during 2011. A total of 39 samples of surface waters, including 29 rivers, 6 lakes and 4 reservoirs were collected. High performance liquid chromatography/negative electrospray ionization-tandem mass spectrometry (HPLC/(-)ESI-MS/MS) was used to identify and quantify PFASs. Concentrations of PFAS were greater in Shanghai than that in Zhejiang Province. Concentrations of the sum of PFASs (∑PFASs) in Shanghai and Kunshan ranged from 39 to 212 ng L(-1), while in Zhejiang Province, concentrations of ∑PFASs ranged from 0.68 to 146 ng L(-1). Perfluorooctanoic acid (PFOA) was the prevalent PFAS in Shanghai. In contrast, PFOA and perfluorohexanoic acid (PFHxA) were the prevalent PFASs in Zhejiang Province. Concentrations of perfluorooctane sulfonate (PFOS) ranged from <0.07 to 9.7 ng L(-1). Annual mass of ∑PFASs transported by rivers that flow into the East China Sea were calculated to be more than 4000 kg PFASs. Correlation analyses between concentrations of individual PFASs showed the correlation between PFHxA and PFOA was positive, while the correlation between PFHxA and perfluorooctane sulfonamide (FOSA) was negative in Shanghai, which indicated that PFHxA and PFOA have common sources. Principal component analysis (PCA) was employed to identify important components or factors that explain different compounds, and results showed that PFHxA and FOSA dominated factor loadings.

As emerging pollutants, microplastics have attracted the attention of scholars from all over the world. However, there is a lack of research on freshwater areas, even in densely populated urban areas. This study investigated eight urban lakes in Changsha, China. It was found that microplastic concentrations ranged from 2425 ± 247.5 items/m3 to 7050 ± 1060.66 items/m3 in the surface water of research areas and the maximum concentration was found in Yuejin Lake, a tourist spot in the center of the city. Anthropogenic factors are an important reason for microplastic abundance in urban lakes. The major shape of microplastics was linear and most of the microplastics were transparent. More than 89.5% of the microplastics had a size of less than 2 mm. Polypropylene was the dominant type in the studied waters. This study can provide a valuable reference for a better understanding of microplastic pollution in urban areas of China.