Spatial and temporal variability of trace metals in aerosol from the desert region of China and the Yellow Sea

Abstract

From spring to early summer of 1995 and 1996, about 180–190 aerosol samples were collected from three observatories at Northwest China desert region (i.e., Minqin), coastal suburb area (i.e., Qingdao), and an island in the Yellow Sea (i.e., Qianliyan), respectively. The samples were analyzed to determine the concentrations of trace metals (Al, Fe, Mn, Na, Cr, Zn, Cu, Co, Ni, Pb, V, Sr, and Cd). Data are examined to understand the distribution of trace metals in aerosols at an upwind desert region and downwind marine recipient under westerly flow. The result shows that trace metal composition of aerosols vary considerably in time and space. Trace metal levels display a drastic seasonal change at both Qingdao and Qianliyan, with concentrations generally 2–3 times higher in spring than summer. Daily variation of trace metal concentrations at Minqin is more significant than Qingdao and Qianliyan, however. The enrichment factors for the crustal source (EFcrust) at Minqin are relatively low and unimportant compared with those at Qingdao and Qianliyan. Some of the trace species like Pb, Zn, and Cd have relatively high contributions from the anthropogenic source (Rp), and >98% are found at Qingdao and Qianliyan, with EFcrust values 1–2 orders of magnitude higher than Minqin. Manganese is mainly from low‐temperature weathering products and the contribution from crustal source (Rc) is >70% at Qingdao and Qianliyan. The coastal atmosphere responds to the episodic dust storms in the desert region (i.e., Minqin) by an increase in aerosol level and a higher concentration of crust‐dominated materials. The percentage contributions from the crustal source (Rc) of trace metals, such as Pb, Cd, and Zn, could be increased considerably by 5–10 folds higher during the passage of cold fronts than during calm weather period over the Yellow Sea.