Atmospheric wet and dry deposition of trace elements at 10 sites in Northern China

Abstract

Abstract. Atmospheric deposition is considered to be a major process that removes pollutants from the atmosphere and an important source of nutrients and contaminants for ecosystems. Trace elements (TEs), especially toxic metals deposited on plants and into soil or water, can cause substantial damage to the environment and human health due to their transfer and accumulation in food chains. Despite public concerns, quantitative knowledge of metal deposition from the atmosphere to ecosystems remains scarce. To advance our understanding of the spatiotemporal variations in the magnitudes, pathways, compositions and impacts of atmospherically deposited TEs, precipitation (rain and snow) and dry-deposited particles were collected simultaneously at 10 sites in Northern China from December 2007 to November 2010. The measurements showed that the wet and dry depositions of TEs in the target areas were orders of magnitude higher than previous observations within and outside China, generating great concern over the potential risks. The spatial distribution of the total (wet plus dry) deposition flux was consistent with that of the dry deposition, with a significant decrease from industrial and urban areas to suburban, agricultural and rural sites, while the wet deposition exhibited less spatial variation. In addition, the seasonal variation of wet deposition was also different from that of dry deposition, although they were both governed by the precipitation and emission patterns. For the majority of TEs that exist as coarse particles, dry deposition dominated the total flux at each site. This was not the case for potassium, nickel, arsenic, lead, zinc, cadmium, selenium, silver and thallium, for which the relative importance between wet and dry deposition fluxes varied by site. Whether wet deposition is the major atmospheric cleansing mechanism for the TEs depends on the size distribution of the particles. We found that atmospheric inputs of copper, lead, zinc, cadmium, arsenic and selenium were of the same magnitude as their increases in the topsoil of agricultural systems. At a background forest site in Northern China, the total deposition flux of lead observed in this study (14.1 mg m−2 yr−1) was twice that of the critical load calculated for temperate forest ecosystems in Europe. These findings provide baseline data needed for future targeting policies to protect various ecosystems from long-term heavy metal input via atmospheric deposition.

Size-resolved source apportionment of particulate matter in urban Beijing during haze and non-haze episodes

“…gans, 2014; Pan et al, 2013). Due to rapid industrialization and urbanization in recent decades, China has become one of the most significant source regions for anthropogenic atmospheric emissions in the world (Guo et al, 2014).…”

Wet Deposition of Trace Metals at a Typical Urban Site in Southwestern China: Fluxes, Sources and Contributions to Aquatic Environments

“…However, the rate slowed down and was even negative in the 2000s, although the level of TMs in the atmosphere was still high. Pan et al found that AWD fluxes of TMs in North China were orders of magnitude higher than those in other regions, e.g., Hong Kong and the Yellow Sea in China, and the TM inputs to agricultural soils by atmospheric deposition were 10-78% of the anthropogenic input [4]. Recently, Xing et al reported that in Jiaozhou Bay, eastern China, the average contribution of AWD to surface water concentrations of TMs was between 1.1% and 12.3%, and heavy rain greatly increased TM concentrations in the surface water [18].…”

“…Atmospheric TM deposition is a key process in the biogeochemical cycles of these elements [3]. Their deposition rates are usually low in clean natural environments, which are infrequently affected by human activities, whereas rapid urbanization and industrialization have accelerated deposition rates in suburban and urban regions [4,5]. Atmospheric deposition is an essential source of TMs in terrestrial and aquatic ecosystems; however, excessive inputs lead to their accumulation, with potential harm to human health [6].…”

A 15-year record (2001–2015) of the ratio of nitrate to non-seasalt sulfate in precipitation over East Asia

“…1). It has been recognized that anthropogenic emissions centered over this region (Kurokawa et al, 2013;Li et al, 2017), related atmospheric concentration, and depositions were severe in China (e.g., Pan et al, 2015). To overcome this limitation and advance our knowledge of precipitation chemistry over the whole of China, we added the following dataset for the chemical 10 concentration of precipitation over China.…”

“…The ground-based observation network in East Asia does not cover the northern China region, which is characterized by a large urban population and related anthropogenic emissions, and therefore atmospheric concentration and depositions were centered (e.g., Pan et al, 2015). The approach taken here will further promote our understanding of precipitation chemistry 15 for all of China.…”