Relationship between Concentrations of Heavy Metals in Wet Precipitation and Atmospheric Pm10 Particles in Zanjan, Iran

In this article the heavy metal concentrations in atmospheric wet precipitation and its relationship with the particles (PM10) in the air of the city of Zanjan are reported. Two hundreds samples of rain water and snow were collected with 45 particle samples collected monthly. Heavy metals in wet and dry samples were determined by atomic absorption spectrophotometery. The use of enrichment factors and correlation coefficients allowed us to predict the major sources of these metals. The ranges of concentration of Pb, Zn, Cr and Cd in rain water (μg/L) were 5.8-22.2, 29.26-70, 1.4-4 and 0.25-1.2, respectively. The results showed that the concentrations of Pb, Zn, Cr and Cd in wet precipitation and PM10 in samples collected in southern parts of the city where the traffic load and industrial activities are very high (zone 4), were 22.2, 70, 1.2 and 4(μg/L) and 840, 16233, 32 and 54.8 (ng/m3), respectively. These values were higher than those measured in the other parts of the city. Most of the calculated enrichment factors higher than 10 were attributed to the traffic and industrial activities. The enrichment factor and correlation coefficient values showed that the heavy metals in the air of Zanjan originate from similar sources. The concentration of particulate matter in 30 air samples of total 45 samples were found to be higher than 50μg/ m3. The average concentrations of Pb and Cd in the city center and near the industrial complexes were higher than World Health Organization standards.