Numerical simulation of wet scavenging of air pollutants—II. Modeling of rain composition at the ground

Characteristics of Air Pollution and Their Relationship with Meteorological Parameters: Northern Versus Southern Cities of China

Air pollution shows a generally decreasing trend from the north to the south in China since 2013 (GB3095-2012, the current standard for monitoring). However, an opposite observation was recorded in 2017, especially in winter. In this study, we collected monitoring data of six air pollutants in 2016 and 2017, from a northern city (Beijing) and a southern city (Nanjing) for comparison. As air pollution was highly dependent upon meteorological conditions, we further analyzed their relationships to explain this abnormal phenomenon. Seasonal averaged PM2.5, PM10, SO2, CO, and NO2 were negatively correlated with wind scale (WS) while 8-h O3 exhibited an opposite relationship. Relative humidity (RH) has opposite effects on the concentrations of different pollutants in Beijing and Nanjing. The 8-h O3 showed the closest positive correlation with temperature (T), which is due to its formation mechanism. In Beijing, decreased RH, together with more wind from northwest in winter, resulted in an improved air quality in 2017. In Nanjing, WS, RH, T, and wind direction fluctuated within a narrow range in each season, leading to relatively stable pollutant concentrations. These results suggest that meteorological conditions are important factors to evaluate the air quality and implement control measures.

Wet and dry deposition fluxes of inorganic chemical species at a rural site in northern Jordan

Wet and dry deposition samples were collected in a rural region in northern Jordan during the period of December 1998 to April 2000. Concentrations of 20 chemical species (Na, K, Ca, H(+), Mg, NH(4)(+), Cl(-), NO(3)(-), SO(4)(2-), Pb, Cd, Zn, Cu, Al, Fe, Mn, Mo, Ni, Sb, and V) were determined in collected samples. Most of the Al, Fe, Mn, Mo, Sb, and V were not soluble, whereas major ions (Na, K, Ca, H(+), Mg, NH(4)(+), Cl(-), NO(3)(-), and SO(4)(2-) ) and some trace elements (Cd, Cu, and Zn) were wet deposited mostly in the soluble form. Concentration of the soil-related elements and/or highly soluble species were washed out at the early stages of a precipitation event, and their concentrations were mostly controlled by dilution, whereas concentrations of anthropogenic species were controlled by other factors. Annual fluxes of the soil-related elements and ions were significantly higher than the primarily anthropogenic elements. This was attributed to the arid nature of the region and to the frequent input of the Saharan dust pulses.

Single particle and inorganic characterization of rainwater collected above the North Sea

Suspended matter and the dissolved fraction of rainwater collected above the North Sea were characterized using electron probe X-ray microanalysis (EPXMA), inductively coupled plasma-optical emission spectrometry (ICP-OES) and ion chromatography (IC), respectively. Suspended particulate matter was dominated by aluminosilicates and organic particles. Fifteen particle types describe the composition of the North Sea rainwater suspended matter. Factor analysis, particle size distributions and manual EPXMA measurements illustrated the complex genesis of different particle types: terrigenous; biogenic (both marine and continental); and anthropogenic. It was demonstrated that at the beginning of a shower of rain the coarse particles that are present in the air under the cloud are washed out, while during the second phase rainout particles, formed in the cloud, become more important due to the absence of new coarse particles under the cloud. Above the sea, the total amount of suspended matter (TSM) is much smaller and more variable than above the land and also the decrease in particle diameter is less visible. Approximately 10% of the studied particles contained trace heavy metals. The dissolved compounds in the North Sea rainwater were also variable in time and space. In general, over a short period of time, the concentrations of all dissolved compounds seem to decrease during a shower, but this decrease is much larger above land than above sea. The concentrations of dissolved trace metals present in rainwater above the southern North Sea has decreased over the last 15 years.