PERSISTENT ORGANOCHLORINE RESIDUES AND THEIR BIOACCUMULATION PROFILES IN RESIDENT AND MIGRATORY BIRDS FROM NORTH VIETNAM

Joint Research on Environmental Science and Technology for the Eart

Butyltin Contamination in Mussels from Vietnam and Other Asian Developing Countries

Joint Research on Environmental Science and Technology for the Eart

Bending and vibration analysis of multi-folding laminate composite plate using finite element method

This paper deals with the bending and vibration analysis of multi-folding laminate composite plate using finite element method based on the first order shear deformation theory (FSDT). The algorithm and Matlab code using eight nodded rectangular isoparametric plate element with five degrees of freedom per node were built for numerical simulations. In the numerical results, the effect of folding angle on deflections, natural frequencies and transient displacement response for different boundary conditions of the plate were investigated

FREQUENCY OPTIMIZATION AND TRANSIENT ANALYSES OF STIFFENED FOLDED LAMINATE COMPOSITE PLATE USING GENETIC ALGORITHM

In  this  study,  frequency  optimization  of  stiffened  folded  laminate  composite  plate  is investigated with  respect  to  fiber orientations by using genetic algorithm  (GA). The first order shear deformation theory was used for direct frequencies calculations. The Matlab programming using rectangular isoparametric plate element with five degrees of freedom per node was built to solve  the  problems. The modulus  of  selection,  crossover  and mutation were  used  as  standard sub-modulus.  The  effects  of  obtained  optimal  fiber  orientation  on  transient  response  of  the folded plate have been investigated with difference boundary conditions. A good agreement was found between the results of this technique and other published results available in the literature

POLLUTION BY PERSISTENT TOXIC SUBSTANCES IN VIETNAM : A REVIEW OF TWO DECADE MONITORING STUDIES

Joint Research on Environmental Science and Technology for the Eart

IDENTIFICATION OF A BACTERIOCIN PRODUCING BY LACTOCOCCUS LACTIS SUBSP. LACTIS PD14

The strain Lactococcus PD14 isolated from cow’s fresh milk was identified as Lactococcus lactis subsp. lactis. The bacteriocin produced by PD14  was isolated and purified by absorption-desorption method described and then this bacteriocin was purified by solid-phase extraction-SPE and HPLC method with column C18. The result of tricine- SDS-PAGE indicated the molecular weight of bacteriocin was about 3.5 kDa, the same as nisin. The prenisin encoding gene was cloned and sequenced successfully for PD14. The nis gene of the strain PD14 was 99 % homology with nisA and nisZ while 98 % with nisF, 97 % with nisQ. The deduced amino acid sequence of prenisin was determined, which had minor difference from published sequence of nisA in one amino acid. At the position aminoacid -18, prenisin of PD14 had valine while  the known prenisin A had phenylalanine. The matured nisin of PD14 was completely similar to the known amino acid sequence of nisA. Thus, the strain Lactococcus lactis subsp. lactis. PD14 produced a bacteriocin which was identified as nisin A

Widespread contamination by persistent toxic substances in Vietnam and their implications on environmental quality and human health

Vietnam is a developing country located in the central part of the Southeast Asian tropical region. The country comprises the Red River and Mekong River Delta, inhabiting more than 30 million people, which is one of the most populous areas in the world. These deltas have become one of the most productive agricultural regions in Southeast Asia. Agrochemicals have been used extensively in the past and until very recently for agricultural purposes and malaria eradication program. The present paper provides a comprehensive overview of the environmental distribution, patterns and trends of contamination of toxic substances including persistent organochlorines (OCs) and endocrine active compounds (EACs) in different environmental compartments from Vietnam. Monitoring data reported during the 1990s demonstrated widespread and elevated contamination of DDTs in air, water, sediments and soils from in Vietnam. Recent studies in frame of the Asia-Pacific Mussel Watch Program have also revealed that fish, mussels and resident birds from Vietnam contained higher concentrations of DDTs as compared to other countries in region, suggesting the role of Vietnamese environment as a significant emission source of DDT in the Southeast Asian region. Subsequent surveys on coastal lines from north and middle part of Vietnam likewise demonstrated that contamination of some endocrine active compounds such as alkylphenols and phthalates are ubiquitous. In particular, relatively high concentrations of bis-phenol A were found in some locations in Red River delta, comparable or higher than those reported for several locations in developed nations in Western Europe and North America. A case study on seasonal variation of alkylphenols and phthalates in surface water of river delta and estuary of north and central Vietnam indicated the differences in distribution of these compounds between dry and rainy seasons. Higher concentrations of alkylphenols and phthalates were found in dry season in estuary; while the contrasting pattern was observed in the river delta, showing elevated residues in rainy season. This result suggests the different behavior of alkylphenols and phthalates in river delta and in coastal environment. The temperature dependence in tropical ecosystem and the influence of the specific local sources may be reasons for the observed results in the seasonal variations. To our knowledge, this is the first extensive study on the widespread contamination of EACs in Vietnam. Regarding the trends of contamination by OCs, preliminary survey conducted in Read River delta water and sediments indicated a rapid decline trend in water and a slow decrease in sediments during 1995-2001. From ecotoxicological and human health perspectives, concentrations of bis-phenol A and di (2-ethylhexyl) phthalates in surface water from some locations in Vietnam exceeded the guideline values for Ecotoxicological Effects and the Environmental Risk Limit, respectively, suggesting potential for toxic implications on aquatic wildlife. Human exposure to persistent organic pollutants indicated that DDT residues levels in human breast milk from both Hanoi and Hochiminh city were among the highest values reported for Asian developing countries as well as developed nations. Daily intakes estimating based on the exposure through sea-foods indicates that intakes of DDTs by Vietnamese populations were among the highest rank in Asia-Pacific countries, suggesting potential risk for human exposure to elevated DDT pollution. Future studies should be focused on the time trends of POPs and EACs in biota of Vietnam with view of predicting the future trend of contamination and to reveal new clues for understanding possible toxic impacts on aquatic organisms

Widespread contamination by persistent toxic substances in Vietnam and their implications on environmental quality and human health

Vietnam is a developing country located in the central part of the Southeast Asian tropical region. The country comprises the Red River and Mekong River Delta, inhabiting more than 30 million people, which is one of the most populous areas in the world. These deltas have become one of the most productive agricultural regions in Southeast Asia. Agrochemicals have been used extensively in the past and until very recently for agricultural purposes and malaria eradication program. The present paper provides a comprehensive overview of the environmental distribution, patterns and trends of contamination of toxic substances including persistent organochlorines (OCs) and endocrine active compounds (EACs) in different environmental compartments from Vietnam. Monitoring data reported during the 1990s demonstrated widespread and elevated contamination of DDTs in air, water, sediments and soils from in Vietnam. Recent studies in frame of the Asia-Pacific Mussel Watch Program have also revealed that fish, mussels and resident birds from Vietnam contained higher concentrations of DDTs as compared to other countries in region, suggesting the role of Vietnamese environment as a significant emission source of DDT in the Southeast Asian region. Subsequent surveys on coastal lines from north and middle part of Vietnam likewise demonstrated that contamination of some endocrine active compounds such as alkylphenols and phthalates are ubiquitous. In particular, relatively high concentrations of bis-phenol A were found in some locations in Red River delta, comparable or higher than those reported for several locations in developed nations in Western Europe and North America. A case study on seasonal variation of alkylphenols and phthalates in surface water of river delta and estuary of north and central Vietnam indicated the differences in distribution of these compounds between dry and rainy seasons. Higher concentrations of alkylphenols and phthalates were found in dry season in estuary; while the contrasting pattern was observed in the river delta, showing elevated residues in rainy season. This result suggests the different behavior of alkylphenols and phthalates in river delta and in coastal environment. The temperature dependence in tropical ecosystem and the influence of the specific local sources may be reasons for the observed results in the seasonal variations. To our knowledge, this is the first extensive study on the widespread contamination of EACs in Vietnam. Regarding the trends of contamination by OCs, preliminary survey conducted in Read River delta water and sediments indicated a rapid decline trend in water and a slow decrease in sediments during 1995-2001. From ecotoxicological and human health perspectives, concentrations of bis-phenol A and di (2-ethylhexyl) phthalates in surface water from some locations in Vietnam exceeded the guideline values for Ecotoxicological Effects and the Environmental Risk Limit, respectively, suggesting potential for toxic implications on aquatic wildlife. Human exposure to persistent organic pollutants indicated that DDT residues levels in human breast milk from both Hanoi and Hochiminh city were among the highest values reported for Asian developing countries as well as developed nations. Daily intakes estimating based on the exposure through sea-foods indicates that intakes of DDTs by Vietnamese populations were among the highest rank in Asia-Pacific countries, suggesting potential risk for human exposure to elevated DDT pollution. Future studies should be focused on the time trends of POPs and EACs in biota of Vietnam with view of predicting the future trend of contamination and to reveal new clues for understanding possible toxic impacts on aquatic organisms

PERSISTENT ORGANOCHLORINE RESIDUES IN HUMAN BREAST MILK FROM VIETNAM : CONTAMINATION, ACCUMULATION KINETICS AND RISK ASSESSMENT

Joint Research on Environmental Science and Technology for the Eart

Contamination by PCDDs, PCDFs and coplanar PCBs in open dumping sites in Vietnam-levels, patterns and toxic implications

Joint Research on Environmental Science and Technology for the Eart