The concentrations of total polycyclic aromatic hydrocarbons (Sigma PAHs) a
nd 15 individual PAH compounds in 20 surface sediments collected from four
mangrove swamps in Hong Kong were analysed. Sigma PAH concentrations ranged
from 356 to 11,098 ng g(-1) dry weight with mean and median values of 1992
and 114.2 ng g(-1), respectively. These values were significantly higher t
han those of marine bottom sediments of Hong Kong harbours, suggesting that
more PAHs were accumulated in mangrove surface sediments. The concentratio
ns of Sigma PAHs as well as individual PAH compound varied significantly am
ong mangrove swamps. The swamps heavily polluted by livestock and industria
l sewage, such as Ho Chung and Mai Po, had much higher concentrations of to
tal PAHs and individual PAH than the other swamps. The PAH profiles were si
milar among four mangrove swamps, and were dominated by naphthalene (two-ri
ng PAH), fluorene and phenanthrene (three-ring PAH). The mangrove sediments
had higher percentages of low-molecular-weight PAHs. These indicated that
PAHs in mangrove sediments might originate from oil or sewage contamination
(petrogenic input). Ratio values of specific PAH compounds such as phenant
hrene/anthracence and fluoranthene/ pyrene, were calculated to evaluate the
possible source of PAH contamination in mangrove sediments. These ratios v
aried among samples, suggesting that mangrove sediments might have a mixed
pattern of pyrolytic and petrogenic inputs of PAHs. Sediments collected fro
m Ho Chung mangrove swamp appeared to be more dominated by pyrolytic input
while those from Tolo showed strong petrogenic contamination. (C) 2001 Else
vier Science Ltd. All rights reserved.