Assessment of Coastal Surface Water Quality in Southern Vietnam

Abstract

The study was carried out to assess the water quality in estuaries and
coastal waters in the South of Vietnam. Water samples were collected
at 12 locations denoted from S1 to S12, in which locations from S1 to
S6 belong to the estuary while positions from S7 to S12 belong to the
sea. Samples were collected 6 times from April to September.
Temperature, pH, DO, EC, TSS, N-NH4
+
, P-PO4
3- and Fe were used
for water quality assessment by comparing with National technical
regulation on marine water quality (QCVN 10-MT:2015/BTNMT).
Cluster and principal component analyses were used to identify
frequency, potential polluting sources, and key variables influencing
coastal water quality. The results show that estuary water was
polluted mainly by TSS and Fe. DO, N-NH4
+
, P-PO4
3- at some
locations exceeded the allowed standards. For water quality in
coastal estuaries, N-NH4
+
, Fe, TSS, DO at several locations exceeded
the allowable limits. Low DO indicated that the coastal water was
organically polluted. P-PO4
3- was still within the allowable limit. TSS,
N-NH4
+
, EC were subjected to seasonal variation. PC1, PC3, and PC3
explained 86.5% variation, were the main sources of water quality
variation. PCA also showed that temperature, pH, DO, EC, TSS, NNH4
+
, P-PO4
3- and Fe were key variable influencing on water quality
and need to be further monitored. CA showed that water quality
monitoring in coastal areas can be reduced from 6 sampling times to
3 times, saving 50% of the monitoring costs.