P.
H. Viet, T. T. Lieu, H. M. Dung, T.T.Tham, B.T.Ha, T.B.Hanh and T.T.T.Mai
Center
for Environmental Technology and Sustainable Development
This study reports monitoring data
of persistent organic pollutants (POPs) such as HCB, heptachlor, aldrin, cis-chlordane,
trans-chlordane, dieldrin, endrin, and p,p’- DDT in surface water and sediments
collected from various rivers in the northern of Vietnam including Day river
(Ninhbinh province), Ma - Chu river system (Thanhhoa province) and Lam river
(Hatinh province). In water samples, endrin was predominant compound with
the average concentration from Day river station of 131 ng/L, which was twice
higher than that at Cuahoi estuary and four times higher than that in two
remaining locations. However, there were small variations between two sampling
seasons. The concentrations were slightly higher in the rainy season compared
to those in the dry season. It was also recognized that the presence of p,p’-DDT
at this location was higher than other ones, except that at Cuahoi estuary,
the lower stream of Ma-Chu river system.
As for sediment samples, p,p’-DDT
and endrin were found with the highest concentrations as compared to other
compounds. The concentration of p,p’-DDT and endrin in sediments collected from
Cuahoi estuary was highest with mean concentration of 9.74 ng/g dry wt and
17.42ng/g dry wt., respectively. Similar to the freshwater samples,
cis-chlordane, trans-chlordane were not detected in almost sediment samples
analyzed. Other compounds such as HCB, heptachlor, aldrin, dieldrin, endrin and
p,p’-DDT were identified with low concentrations (the level ranged from 1 – 10
ng/g dry wt.). Contrary to the results from water samples, measured data in
sediment samples showed the trend of seasonal variation with the concentrations
in dry season higher than that in rainy season. The presence of analyzed POPs
in freshwater and sediment samples showed its use at survey areas. p,p’-DDT was
detected in both seasons, impling the widespread use of this the north and
middle part of Vietnam. The differences in seasonal changes of POP
concentrations in freshwater and sediment suggest the possible influence of the
flowing of the investigated rivers in rainy and dry seasons. The fate and
behavior of semivolatile POPs might be different from rivers and closed
environment such as lakes which were investigated over the last 2 years.
Further studies on the spatial distribution, trend and behavior of POPs in
different water bodies in Vietnam are needed in the future.