Atmospheric heavy metal deposition in Northern Vietnam: Hanoi and Thainguyen case study using the moss biomonitoring technique,INAA and AAS

Background, aim, and scope  

The moss technique is widely used to monitor atmospheric deposition of heavy metals in many countries in Europe, whereas this technique is scarcely used in Asia. To implement this international reliable and cheap methodology in the Asian countries, it is necessary to find proper moss types typical for the Asian environment and suitable for the biomonitoring purposes. Such a case study was undertaken in Vietnam for assessing the environmental situation in strongly contaminated areas using local species of moss Barbula indica.     

ELISA detection of multixenobiotic resistance transporter induction in indigenous freshwater Chironomidae larvae (Diptera): A biomarker calibration step for in situ monitoring of xenobiotic exposure

A new simple and sensitive method to distinguish chemically polluted from unpolluted situations in freshwater ecosystems is reported. For this purpose, Chironomus gr thumni larvae were collected from a polluted urban river downstream a sewage treatment plant. For the first time, ELISA assay was used to semi-quantify the multixenobiotic resistance transporters (MXR) in these small pertinent bioindicators. The use of samples immediately fixed in the field gives a delay to isolate larvae and allows multi-sampling along a longitudinal transect in a river at a given time. Results exhibit an induction of MXR proteins in larvae from the polluted river and a deinduction in larvae maintained 11days in unpolluted water. They show new evidences to use midge larvae in biomonitoring environmental programs. They answer to first biomarker calibration steps for the ongoing development of MXR transporters as a detection tool of xenobiotic impacts on bioindicator invertebrates in their freshwater habitats.     

Contamination of drinking water resources in the Mekong delta floodplains: arsenic and other trace metals pose serious health risks to population

This study presents a transnational groundwater survey of the 62,000 km(2) Mekong delta floodplain (Southern Vietnam and bordering Cambodia) and assesses human health risks associated with elevated concentrations of dissolved toxic elements. The lower Mekong delta generally features saline groundwater. However, where groundwater salinity is <1 g L(-)(1) Total Dissolved Solids (TDS), the rural population started exploiting shallow groundwater as drinking water in replacement of microbially contaminated surface water. In groundwater used as drinking water, arsenic concentrations ranged from 0.1-1340 microg L(-)(1), with 37% of the studied wells exceeding the WHO guidelines of 10 microg L(-)(1) arsenic. In addition, 50% exceeded the manganese WHO guideline of 0.4 mg L(-)(1), with concentrations being particularly high in Vietnam (range 1.0-34 mg L(-)(1)). Other elements of (minor) concern are Ba, Cd, Ni, Se, Pb and U. Our measurements imply that groundwater contamination is of geogenic origin and caused by natural anoxic conditions in the aquifers. Chronic arsenic poisoning is the most serious health risk for the ~2 million people drinking this groundwater without treatment, followed by malfunction in children's development through excessive manganese uptake. Government agencies, water specialists and scientists must get aware of the serious situation. Mitigation measures are urgently needed to protect the unaware people from such health problems.     

Response surface method for modeling the removal of carbon dioxide from a simulated gas using water absorption enhanced with a liquid-film-forming device

This paper presents the results from using a physical absorption process to absorb gaseous CO_2mixed with N_2using water by producing tiny bubbles via a liquid-film-forming device(LFFD)that improves the solubility of CO_2in water.The influence of various parameters—pressure,initial CO_2concentration,gas-to-liquid ratios,and temperature—on the CO_2removal efficiency and its absorption rate in water were investigated and estimated thoroughly by statistical polynomial models obtained by the utilization of the response surface method(RSM)with a central composite design(CCD).Based on the analysis,a high efficiency of CO_2capture can be reached in conditions such as low pressure,high CO_2concentration at the inlet,low gas/liquid ratio,and low temperature.For instance,the highest removal efficiency in the RSM–CCD experimental matrix of nearly 80%occurred for run number 20,which was conducted at 0.30 MPa,CO_2concentration of 35%,gas/liquid ratio of 0.71,and temperature of 15°C.Furthermore,the coefficients of determination,R~2,were 0.996 for the removal rate and 0.982 for the absorption rate,implying that the predicted values computed by the constructed models correlate strongly and fit well with the experimental values.The results obtained provide essential information for implementing this method properly and effectively and contribute a promising approach to the problem of CO_2capture in air pollution treatment.     

Persistent organochlorine residues in human breast milk from Hanoi and Hochiminh City, Vietnam: contamination, accumulation kinetics and risk assessment for infants

Despite the ban on persistent organochlorines (OCs) in most of the developed nations, their usage continued until recently in many Asian developing countries including Vietnam, for agricultural purposes and vector-borne disease eradication programs. In this study, we collected human breast milk samples from the two big cities in Vietnam: Hanoi (n=42) and Hochiminh (n=44) and determined the concentrations of persistent OCs such as PCBs, DDT and its metabolites (DDTs), hexachlorocyclohexanes (HCHs), hexachlorobenzene (HCB), chlordane compounds (CHLs) and tris-4-chlorophenyl-methane (TCPMe). The contamination pattern of OCs was in the order of DDTs > PCBs > HCHs > CHLs approximately HCB approximately TCPMe. Compilation of available data indicated that DDT residue levels in human breast milk from Vietnam were among the highest values reported for Asian developing countries as well as developed nations. This result suggests recent usage of DDTs in both north and south Vietnam. Interestingly, in both cities, the p,p'-DDT portion was higher in multiparas than those in primiparas. Considering the fact that the interval between the first and the second child of a mother in Vietnam is usually short, this result probably indicates continuous intake of DDTs in the population. Analysis of infant exposure to DDTs via breast milk suggested that the daily intake rates for number of individuals are close to or above the threshold for adverse effects which may raise concern on children health.     

Daphne gnidium, a possible native host plant of the European grapevine moth Lobesia botrana, stimulates its oviposition. Is a host shift relevant?

Summary. We tested the hypothesis that Daphne gnidium is an ancestral host plant of Lobesia botrana. To this end, we studied the oviposition response of this moth to various aerial organs of this plant. Our results show that females prefer to lay eggs on daphne berries rather than on grapes (cv. chasselas) and that polar surface extracts of daphne berries and leaves strongly stimulate oviposition in a dosedependant way, whereas flower extracts are weakly stimulant and branch extracts are inactive or deterrent for oviposition. Furthermore, a total extract of daphne berries stimulates oviposition in semi-natural conditions when applied onto fresh grapes. Oviposition stimulants from berries were isolated by HPLC coupled with a dual-choice oviposition bioassay. The ecological value of D. gnidium for L. botrana is discussed and the possible use of oviposition stimulants from daphne, contrasting with the oviposition signal of the cultivated host plant, is proposed in the perspective of developing behavioural manipulation methods such as stimulo-deterrent diversionary strategies compatible with IPM programs.     

Proximate composition of household waste and applicability of waste management technologies by source separation in Hanoi,Vietnam

The organic fraction of municipal solid wastes in Southeast Asia, which has a high moisture content, accounts for a large proportion of total waste. Local governments need to pay adequate attention to the composition of wastes to determine alternative waste management technologies. This study proposed the use of a triangle diagram to describe changes in proximate composition and rates of successful source separation of municipal solid waste and to identify technical challenges about alternative waste management technologies such as incineration, composting, and refuse-derived fuel production based on physical and proximate composition analysis of household waste sampled in Hanoi, Vietnam, as a case study. The analysis indicated the effectiveness of different types of source separation as well as different levels of successful achievement of source separation as an adjustment mechanism for the proximate composition of waste. Proper categorization of wastes for source separation is necessary for the appropriate use of alternative waste management technologies. The results showed that, at a source separation rate of just greater than 0.52 in a three-way separation scheme, the waste separated as combustible waste would be suitable for incineration with energy recovery. Based on well-designed schemes of source separation, alternative waste management technologies can be applied.