The partitioning behavior of PAHs between settled dust and its extracted water phase: Coefficients and effects of the fluorescent organic matter.

The occurrence and distribution of polycyclic aromatic hydrocarbons (PAHs) in a city of Central China were determined in the settled dust and its extracted water phase from different land use types and bus stops in Nanchang City. The physicochemical properties of its water extracted dissolved organic matter (WEOM) were characterized to investigate the effect of fluorescence organic matter on the dust-water partitioning coefficients (Kd) using three-dimensional excitation-emission matrix fluorescence spectroscopy combined parallel factor analysis. Results showed that the range of ∑PAHs in settled dust and the extracted water phase was 0.05-15.92 µg·g-1 and 2-211 ng·L-1, respectively. These PAHs mostly came from the combustion of biomass. The risk assessment showed that PAHs in dust had no obvious health risk (less than the magnitude of 10-6). Additionally, the high molecular weight (HMW) PAHs and the low molecular weight (LMW) PAHs were preferentially adsorbed by dust and the dissolved portion, respectively. It was confirmed by the relatively high logKd values of 4.23 for the HMW-PAHs. Pearson correlation analysis suggested that the higher concentration of dissolved organic carbon and humic-like substance were in favor of PAHs in dust released into waters. This study can provide information on pollution control when considering the impact of fluorescent organic matter on the fate and transport of PAHs.

Relationship between the characterization of natural colloids and metal elements in surface waters.

Natural colloids (NCs) are ubiquities in aquatic environments, which play an important role in the fate and transport of metal elements. Combined with a multi-method analytical approach, this study investigates the spectral characteristics and the contamination of metals of NCs from the five tributaries of Poyang Lake and the lakes in Nanchang City. Results showed that NCs in river samples were characteristic by the smaller molecular weight, lower chromophoric dissolved organic matter (CDOM) concentration, higher aromaticity, and higher CDOM contribution to the organic carbon than those in lake samples. Based on the parallel factor analysis model, three fluorophores were identified, including two humic-like components (C1 and C2) and a protein-like component (C3). NCs in river and lake waters were dominant by the humic-like substance (C1) and the protein-like substance (C3), respectively, with the relatively high fluorescence intensity for all the fluorophores in lake samples. Furthermore, NCs from the river samples were primarily terrestrial NCs with a high degree of humification. The average detection frequency of metal elements was nearly 50% for both river and lake samples, whereas the concentrations of the metal elements were higher in lake samples. Principal component analysis (PCA) results showed that the contamination of the detected metals could divide into three categories, with relatively high concentrations of Ba, Pb, Zn, Al, Sr, and Fe in lake samples. Moreover, PCA results showed that NCs in lakes with higher values of the absorbance and fluorescence parameters were associated with the higher concentration of metal elements, revealing that the spectral characteristic could be the proxy indicator of the contamination of metal elements of NCs.

Fluorescence characterization of fractionated dissolved organic matter in the five tributaries of Poyang Lake, China.

Characterization of natural colloids is the key to understand pollutant fate and transport in the environment. The present study investigates the relationship between size and fluorescence properties of colloidal organic matter (COM) from five tributaries of Poyang Lake. Colloids were size-fractionated using cross-flow ultrafiltration and their fluorescence properties were measured by three-dimensional excitation-emission matrix fluorescence spectroscopy (3D-EEM). Parallel factor analysis (PARAFAC) and/or Self-organizing map (SOM) were applied to assess fluorescence properties as proxy indicators for the different size of colloids. PARAFAC analysis identified four fluorescence components including three humic-like components (C1-C3) and a protein-like component (C4). These four fluorescence components, and in particular the protein-like component, are primarily present in <1 kDa phase. For the colloidal fractions (1-10 kDa, 10-100 kDa, and 100 kDa-0.7 µm), the majority of fluorophores are associated with the smallest size fraction. SOM analysis demonstrated that relatively high fluorescence intensity and aromaticity occur primarily in <1 kDa phase, followed by 1-10 kDa colloids. Coupling PARAFAC and SOM facilitate the visualization and interpretation of the relationship between colloidal size and fluorescence properties with fewer input variables, shorter running time, higher reliability, and nondestructive results. Fluorescence indices analysis reveals that the smallest colloidal fraction (1-10 kDa) was dominated by higher humified and less autochthonous COM.