Distribution and variability of total mercury in snow cover-a case study from a semi-urban site in Poznań, Poland

Chemical characteristics, distribution patterns, and source apportionment of particulate elements and inorganic ions in snowpack in Harbin, China

Snowpack, which serves as a natural archive of atmospheric deposition of multiple pollutants, is a practical environmental media that can be used for assessing atmospheric records and input of the pollutants to the surface environments and ecosystems. A total of 29 snowpack samples were collected at 20 sampling sites covering three different functional areas of a major city (Harbin) in Northeast China. Two samples at the "snow layer" and one or two samples at the "particulate layer" were collected at each sampling site in the industrial areas characterized by multi-layer snowpack, and only one sample at the "snow layer" was collected at each sampling site in the cultural and recreational as well as agricultural areas. The snow contents of 31 elements (Na, Mg, Al, K, Ca, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Y, Cd, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Pb) and six major water-soluble inorganic ions (WSIIs, NH4+, K+, Ca2+, NO2-, NO3-, and SO42-) were analyzed. The total mass of the measured elements is dominated (95.8%-99.2%) by crustal elements. Heavy metals only account for 0.77%-4.07% of the total mass of the elements, but are occasionally close to or even above the standard limit in the "Environmental Quality Standards for Surface Water" of China (GB3838-2002). SO42- and Ca2+ are the main anion and cation, accounting for 34.9%-81.1% and 1.43%-29.9%, respectively, of the measured total ions. Total atmospheric deposition of crustal elements and heavy metals is dominated by wet deposition in areas near the petrochemical plant and by dry deposition in areas near the cement plant. Coal combustion, industrial emissions, and traffic-related activities lead to the enrichment of heavy metals in the snowpacks of urban and suburban areas, while coal combustion and biomass burning contribute to pollution in rural areas. The cities and regions situated in the western, northwestern, northern, and northeastern directions from Harbin are potential source regions of these pollutant species.

Elemental composition of dust aerosols near cement plants based on the study of samples of the solid phase of the snow cover

This study is focused on the quantification of dust load on snow cover and chemical elements content in the solid phase of snow cover in the impacted areas of cement plants (the south of Western Siberia). Applying the instrumental neutron activation analysis, we identified chemical composition in the samples of the solid phase of snow cover. The results demonstrated that the dust load corresponded to the permissible pollution levels in the living zones. Dust pollution level varied from moderately hazardous to highly hazardous in the north-western impacted zone of the cement plants and raw material open pits. It was found that the predominant chemical element is Ca, as well as a group of rare-earth (Yb, Tb, Sm, La, Ce, etc.) elements in the solid phase of snow cover from the impacted zone of the cement plants.

Seasonal variability of trace elements in fine particulate matter (PM2.5) in a coastal city of northern Poland - profile analysis and source identification

A large group of trace elements (Al, As, Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, Ti, V, and Zn) was measured for the first time in 226 air samples collected at a coastal monitoring station in Gdynia (northern Poland), in the period from January 12th to August 30th, 2019. The 24 h measurements included fine particle (PM_2.5) concentrations, meteorological parameters and backward air mass trajectory analyses. The monthly mean PM_2.5 mass concentration ranged from 17.3 μg m^-3 to 55.0 μg m^-3, and the peak value of 167 μg m^-3 was found in February. Overall, considerable differences in the trace element concentrations were observed. However, their seasonal distributions were not similar. In particular, elements such as Cd, Cu, Mo, Ni, V and Zn showed significantly higher concentrations (p < 0.05) in winter compared to spring or summer. The winter peak of trace element concentrations in PM_2.5 indicated that local power plants and fossil fuel/coal combustion in the residential sector were the major anthropogenic sources of air pollutants. Based on multivariate analysis (PCA) of the standardized database (14 elements and PM_2.5), a significant contribution of different sources and processes was identified, i.e. local traffic emission, local/regional coal/oil burning in power plants and domestic heating units, industrial activities, petrochemical industry and maritime transport. The Cu/Fe ratios revealed that both local traffic and brake-wear emission considerably influenced the chemical composition of PM_2.5. In addition, the results of the V/Ni ratio suggested local mixed industrial sources (petrochemical refinery and industrial plants) with possible contributions from the port area and shipping activities to the total PM_2.5 loadings. The local ship emission was more pronounced during the summer period.

Influence of urban surface roughness on build-up and wash-off dynamics of road-deposited sediment

An in-depth understanding of the impacts of surface roughness on road-deposited sediment (RDS) build-up and wash-off is essential for the estimation of surface runoff loads and design of RDS control measures. In this study, RDS build-up and wash-off dynamic processes were investigated on paired asphalt and concrete road surfaces with 35 days of continuous sampling during different natural rainfall events. Our results showed that RDS build-up loads and grain size composition were affected by surface roughness, while the impact of surface roughness on the length of the dynamic equilibrium period was not notable. Selective wash-off of RDS with different effects according to grain size are more likely to occur on asphalt road surfaces during rainfall-runoff, but the RDS wash-off percentage is not affected by surface roughness during snowmelt-runoff. Both total apparent depression depth and micro-depression structures influence RDS build-up and wash-off dynamics. These results imply that surface roughness has combined effects on RDS build-up and wash-off dynamics during the generation and control of urban diffuse pollution.

Comparison between snowmelt-runoff and rainfall-runoff nonpoint source pollution in a typical urban catchment in Beijing, China

As a climate-driven event, nonpoint source (NPS) pollution is caused by rainfall- or snowmelt-runoff processes; however, few studies have compared the characteristics and mechanisms of these two kinds of NPS processes. In this study, three factors relating to urban NPS, including surface dust, snowmelt, and rainfall-runoff processes, were analyzed comprehensively by both field sampling and laboratory experiments. The seasonal variation and leaching characteristics of pollutants in surface dust were explored, and the runoff quality of snowmelt NPS and rainfall NPS were compared. The results indicated that dusts are the main sources of urban NPS and more pollutants are deposited in dust samples during winter and spring. However, pollutants in surface dust showed a low leaching ratio, which indicated most NPS pollutants would be carried as particulate forms. Compared to surface layer, underlying snow contained higher chemical oxygen demand, total suspended solids (TSS), Cu, Fe, Mn, and Pb concentrations, while the event mean concentration of most pollutants in snowmelt tended to be higher in roads. Moreover, the TSS and heavy metal content of snowmelt NPS was always higher than those of rainfall NPS, which indicated the importance of controlling snowmelt pollution for effective water quality management.