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

Abstract

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.

Dissolved and Suspended Forms of Metals and Metalloids in Snow Cover of Megacity: Partitioning and Deposition Rates in Western Moscow

“…The A comparative analysis of the chemical composition of atmospheric dust, snowmelt-runoff, and rainfall-runoff in Beijing showed the leading role of dust in the formation of precipitation composition. Its presence in the snow cover results in the predominance of suspended forms of pollutants [12]. High proportions of many MMs in the suspension along with the dissolved forms of Na, K, Ca, Sr, and Sb were also identified in snow cover on the windward slope of the Salt Lake Valley (central Wasatch Mountains), Utah, USA [111].…”

“…Concentrations of dissolved forms of MMs in snow cover depend on the intensity of transport impact; they are also associated with different amounts of DISs applied on different roads. For example, the concentrations of Na in snow of Novi Sad (Serbia), those of Cu, Fe, Zn, and Pb in snow of Beijing (China), and those of Al, Co, Cr, Cu, Mn, and Ni in snow of Lahti (Finland) increase with larger road size, while the concentrations of Zn in Novi Sad and Clin Beijing decrease [4,12,55].…”

“…To assess geochemical impact on the components of urban landscapes during the snow occurrence period, it is necessary to determine the accumulated supplies of MMs released during snow melting. The content of particulate matter and MMs in snow meltwater of urban areas is greater than in rainfall-runoff, indicating the crucial role of snow melting for the formation of chemical composition of river runoff [12,15]. Snow-covered areas near different types of roads, in the yards, and in the background territory are quite different, because the city territory is severely fragmented by the road network and buildings.…”

“…The thickness of snow cover in WAO differed only slightly from the long-term mean values (35-45 cm) [51,54] and averaged 42-50 cm near roads, increasing to 55-65 cm (averaged 61 cm) within the background areas. It is known that MMs concentrations in the surface layer of snow cover are usually lower than in the underlying layers [12]. To avoid underestimation of snow cover pollution, snow samples were taken along the full depth of undisturbed snow cover.…”

A Location Intelligence System for the Assessment of Pluvial Flooding Risk and the Identification of Storm Water Pollutant Sources from Roads in Suburbanised Areas

“…Road dust deposit is one of the main sources of urban pollutants. Because of low leaching ratios, these pollutants are mainly transported in particulate forms [22]. Sealed surfaces provide a sink for road sediments, which tend to accumulate during dry periods.…”