Size-segregated characteristics of water-soluble oxidative potential in urban Xiamen: Potential driving factors and implications for human health.

Oxidative potential (OP), defined as the ability of particulate matter (PM) to generate reactive oxygen species (ROS), has been considered as a potential health-related metric for PM. Particles with different sizes have different OP and deposition efficiencies in the respiratory tract and pose different health risks. In this study, size-segregated PM samples were collected at a coastal urban site in Xiamen, a port city in southeastern China, between August 2020 and September 2021. The water-soluble constituents, including inorganic ions, elements and organic carbon, were determined. Total volume-normalized OP based on the dithiothreitol assay was highest in spring (0.241 ± 0.033 nmol min-1 m-3) and lowest in summer (0.073 ± 0.006 nmol min-1 m-3). OP had a biomodal distribution with peaks at 0.25-0.44 µm and 1.0-1.4 µm in spring, summer, and winter and a unimodal pattern with peak at 0.25-0.44 µm in fall, which were different from the patterns of redox-active species. Variations in the seasonality of fine and coarse mode OP and their correlations with water-soluble constituents showed that the size distribution patterns of OP could be attributed to the combined effects of the size distributions of transition metals and redox-active organics and the interactions between them which varied with emissions, meteorological conditions and atmospheric processes. Respiratory tract deposition model indicated that the deposited OP and the toxic elements accounted for 47.9 % and 36.8 % of their measured concentrations, respectively. The highest OP doses and the excess lifetime carcinogenic risk (ELCR) were found in the head airway (>70 %). However, the size distributions of OP deposition and ELCR in the respiratory tract were different, with 63.9 % and 49.4 % of deposited ELCR and OP, respectively, coming from PM2.5. Therefore, attention must be paid to coarse particles from non-exhaust emissions and road dust resuspension.

[Atmospheric NH3 Emission Inventory and Its Tempo-spatial Changes in Xiamen-Zhangzhou-Quanzhou Region from 2015 to 2020].

Based on the district and county activity level data of different types of atmospheric ammonia (NH3) emission sources in the Xiamen-Zhangzhou-Quanzhou (XZQ) Region and the modified emission factors, an ammonia emission inventory with a spatial resolution of 1 km×1 km in 2017 was established. In addition, the annual variations in NH3 emission from 2015 to 2020 in this region were analyzed. The results showed that the emission of NH3 in the XZQ Region in 2017 was 27.40 kt with livestock and poultry breeding, farmland ecosystem, human emission, fuel combustion, and waste treatment accounting for 42.48%, 22.04%, 14.71%, 7.08%, and 5.69% of the total emission, respectively. The order of emission density of NH3 was Xiamen (1.94 t·km-2)>Quanzhou (1.07 t·km-2)>Zhangzhou (0.95 t·km-2). High values of emission density were mainly concentrated in the coastal urban areas with a concentrated population and the inland township areas with developed livestock and poultry breeding and planting industries. The monthly variation in NH3 emissions was consistent with the pattern of temperature change, with high values in summer. Due to the different economic structure and development level in different cities, NH3 emissions in Quanzhou City showed a decline from 2015 to 2020, whereas there were fluctuations in the trends of ammonia emissions in Xiamen and Zhangzhou cities. The relationship between NH3 emission intensity and per capita GDP was significantly negative.

[Distribution of Different Phosphorus Species in Water and Sediments from Gaocun to Lijin Reaches of the Yellow River].

The Yellow River is the second longest river in China, which plays a very important role in the transportation of nutrients at the regional and even global scale. Water and sediment samples were collected at five sites located at the Gaocun to Lijin reaches along the Yellow River and the distribution characteristics of different phosphorus species were analyzed. The concentration of suspended particulate matter (SPM) in water ranged from 1.89 to 2.67 g·L-1 with an average of 2.26 g·L-1 in May and from 0.43 to 1.79 g·L-1 with an average of 1.21 g·L-1 in September. It almost had the same variation rule as the water flux, which reflects the influence of water flux on SPM transportation. The concentration of total phosphorus (TP) in water ranged from 0.05 to 2.31 mg·L-1 in May and from 0.03 to 0.1 mg·L-1 in September. Particulate phosphorus (PP) was the dominant TP species in both months, and TP and PP were significantly correlated (P<0.01), which implied that phosphorus loss in soil from Gaocun to Lijin reaches is still serious. Water runoff was positively correlated with TP and PP (P<0.05), but negatively correlated with total dissolved phosphorus (TDP) and dissolved inorganic phosphorus (DIP) (P<0.05, P<0.01, respectively). Increasing water runoff obviously increased the dilution of TDP and DIP. The concentration of SPM was negatively correlated with DIP (P<0.01), the adsorption of SPM on phosphorus was mainly the adsorption of DIP. The permanganate index in water was higher in fall suggesting more serious organic pollution and it was positively correlated with DIP (P<0.01). The phosphorus content in sediments was quite low in both months; the total phosphorus (TP) content in sediments ranged from 284.23 to 569.58 mg·kg-1 in May and from 287.97 to 355.39 mg·kg-1 in September. Calcium-bound phosphate (Ca-P) was the dominant species of inorganic phosphorus (IP). The labile organic phosphorus (L-OP) content was significantly correlated with runoff, SPM concentration, and permanganate index (P<0.01,P<0.05,P<0.01, respectively). The organic phosphorus (OP) content was significantly higher at the Lijin site in May, likely caused by the rainfall-runoff from the mining area around Lijin. The energy-based production activities from the Gaocun to Lijin reaches should also be further investigated.