Authors:
Tan-Duc Nguyen
, Thi-My-Chi Vo
, Cong-Thanh Dao
, Xuan-Quang Ngo
, Thanh-Son Dao |
Abstract:
This study evaluated the chronic toxicity of wastewater from Nhon Trach Industrial Zone, in
Southern Vietnam, to life history traits of Daphnia magna. Wastewater samples were collected at
the out let of the industrial zone for heavy metal and toxicity bioassay. The animals were
exposed to the wastewater at different concentrations 0, 10%, 50% and 100% (v/v) for 21 days
under laboratory conditions. Survival, maturation, reproduction and negative appearance of D.
magna were recorded daily while dry weight of the animal was measured by the end of
experiments. The inductively coupled plasma/mass spectrometry analysis characterized many
heavy metals with their concentrations within the guideline values of Vietnam water quality
(QCVN) for discharge into nature. Results of toxicity tests showed that the wastewater quickly
increased mortality, significantly delayed maturation and caused strong reduction on
reproduction of D. magna. Dead embryos and neonates in the Daphnia's shell were found in the
wastewater exposures. Seriously, the phenomenon of D. magna's organ disappeared after
reproducing was recorded in wastewater incubation. To our knowledge, this is the first study on
the toxicity of industrial wastewater to D. magna. Further investigations should be conducted for
revising the QCVN to protect sensitive organisms in the aquatic ecosystem. |
