Abstract: Rainfall partitioning has great effects on chemical elements transport. We examined the effects of rainfall partitioning on the deposition of heavy metals (Zn, Fe, Cu, Ni, Pb, As, Cd and Hg) for three typical urban tree species (Roystonea regia, Ficus microcarpa and Lagerstroemiaspeciosa) in Guangzhou from October 2018 to September 2019. Results showed that the rate of throughfall to precipitation for R. regia, F. microcarpa and L. speciosawas 62.68%, 58.79% and 67.95%, respectively, while the stemflow rate was 6.34%, 2.08% and 1.02%, respectively. These results suggest different rainfall partitioning among three urban tree species. Except that Cd leaching coefficient of F. microcarpa stemflow was less than 1, the leaching coefficients of heavy metals for throughfall and stemflow of three species were greater than 1, indicating positive leaching. The total inputs of heavy metals for three urban trees were 1.11, 1.80 and 1.99 times of that from precipitation, indicating that the contents of heavy metals were increased after precipitation. The enrichment rate of heavy metals for stemflow ranged from 2.06 to 118.22, suggesting that stemflow could enrich heavy metals in urban trees. The results have important implications for the selection of urban tree species and the prevention of regional pollution.

Key words: throughfall, stemflow, canopy leaching, heavy metal deposition, urban tree species.