Present and long-term pollution status of airborne copper in major urban environments

- The pollution status of metals from anthropogenic sources has been worsened over the past decades.
- There is a strong imbalance in the amount of quantitative data between different airborne metal species.
- Although Cu data are abundant in soil media, its direct measurement data are scant in ambient air.
- This work aims to elucidate the factors underlying the spatiotemporal distribution of airborne Cu.

The concentrations of many harmful metals in air have been continuously decreasing around the world especially in North America and Western Europe, although deviations from such trend have been observed elsewhere such as East Asia. To help understand spatiotemporal factors governing the environmental behavior of hazardous metals, the concentrations of copper (Cu) in total suspended particulate (TSP) fractions were analyzed in the seven major cities in South Korea over a two decadal period (1991 through 2012). Unlike other metal species, there was no distinctive seasonal trend (e.g., spring/winter maximum and summer minimum) in the Cu levels in most South Korean cities. The long-term trend of Cu, if assessed by its annual mean values, recorded two contrasting trends for each decade: the earlier period (from 1991 to early 2000) is characterized by high variabilities with a maximum concentration of 243 ng m−3 (in 2003), while the later period showed an appreciable (several-fold) reduction to the latest (2012) available concentration level of 35.7 ng m−3. As such, the present Cu levels in Korea should approach those commonly seen in moderately clean urban environments elsewhere. The overall results suggest that South Korean regulatory efforts to control particulate matter (PM) emissions have greatly influenced the present Cu levels consistent with the observed temporal trends of airborne PM.