WATER ALLOCATION POLICY MODELING FOR THE DONG NAI RIVER BASIN: AN INTEGRATED PERSPECTIVE1

Abstract: Recent water sector reforms and increased scarcity and vulnerability of water resources, combined with declining public funding available for large scale infrastructure investment in the sector, have led to a greater awareness by the Government of Vietnam for the need to analyze water resource allocation and use in an integrated fashion, at the basin scale, and from a perspective of economic efficiency. In this study we focus on the development, application, and selected policy analyses using an integrated economic hydrologic river basin model for the Dong Nai River Basin in southern Vietnam. The model framework depicts the sectoral structure and location of water users (agriculture, industry, hydropower, domestic, and the environment) and the institutions for water allocation in the basin. Water benefit functions are developed for the major water uses subject to physical limitations and to constraints of system control and policy. Based on this modeling framework, we will analyze policies that can affect water allocation and use at the basin level, including both basin-specific and general macroeconomic policies.     

Optimal resource extraction contract with adverse selection

This paper studies the design of a mining concession contract as a multi-period adverse selection problem where production is the depletion of a non renewable resource. Compared with symmetric information, we show that overproduction is optimal in the terminal phase of the resource extraction program. Moreover, asymmetric information lengthens the contract duration but reduces the scarcity rent.     

内陆排污对杭州湾南岸滩涂湿地浮游桡足类群落结构的影响

2010年1月～2011年1月,在杭州湾南岸滩涂湿地5个断面(S1～S3为排水区,S4～S5为非排水区。)10个采样站进行桡足类群落结构的周年调查,分析了不同生态环境下桡足类群落的种类组成、密度、生物量和种类丰富度等时空变化特征。共发现桡足类19种,剑水蚤和猛水蚤各7种、哲水蚤5种,其中,8种为淡水种,11种为咸淡水种。根据种群的年平均密度和出现频度,淡水种类的优势种为汤匙华哲水蚤(Sinocalanus dorrii)、台湾温剑水蚤(Thermocyclops taihokuensis)和三角大吉猛水蚤(Tachidius triangularis),半咸淡水种类的优势种为中华哲水蚤(Calanus sinicus)和球状许水蚤(Schmackeria forbesi)。群落年平均密度变幅2.64～39.16/L,平均13.54/L;生物量0～2.078 mg/L,平均0.164 mg/L。哲水蚤的群落密度和生物量分别占总桡足类的29.32%和79.88%。密度季节变化以春季>秋季>夏季>冬季,水平变化以S3>S2>S1>S5>S4,S2断面中潮位比高潮位多67.00%。Margalef种类丰富度在1.20～6.20,平均3.35。污对中潮位桡足类群落的影响大于高潮位。     

Impact of hydroxylated and non-hydroxylated aliphatic glucosinolates in Arabidopsis thaliana crosses on plant resistance against a generalist and a specialist herbivore

Glucosinolates (GSs) are part of a two-component defence system, characteristic for the Brassicales, including the model species Arabidopsis thaliana (L.) Heynh. The defence activity of GSs is associated with different side chain structures. The AOP genes are central in side-chain modification. AOP2 mediates formation of alkenyl GS from a methylsulfinyl precursor, whereas AOP3 catalyzes production of hydroxy-alkyl GSs from the same precursor. Although several studies have assessed the role of GSs in plant defence, the function of specific aliphatic GSs in plant defence is still not clarified. Structural different GSs may influence insect herbivores differentially. We created a set of plant lines derived of a cross between two A. thaliana accessions, Gie-0 × Sap-0, which dominantly accumulate either 3-methylsulfinylpropyl GS or 3-hydroxypropyl GS. The generalist Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae) and the crucifer-specialist Pieris brassicae (L.) (Lepidoptera: Pieridae) were used as model insects, to study effects of individual aliphatic GSs on lepidopteran herbivores with a different feeding specialization. However, the experiments revealed that weight gain of S. exigua and P. brassicae third and fourth-larval instars was similar on both chemotypes. But leaf consumption of the generalist was higher on 3-methylsulfinylpropyl-producing lines with low GS levels (23.2 μmol g⁻¹) than on 3-hydroxypropyl-producing lines that contained a more than twofold higher amount of GSs (60 μmol g⁻¹). In contrast, no differential effects of non-hydroxylated and hydroxylated GSs were found on the specialist P. brassicae. Our study indicates that there is no simple relationship between GS content and insect responses.     

Assessment of plastic waste generation and its potential recycling of household solid waste in Can Tho City, Vietnam

Plastic solid waste has become a serious problem when considering the disposal alternatives following the sequential hierarchy of sound solid waste management. This study was undertaken to assess the quantity and composition of household solid waste, especially plastic waste to identify opportunities for waste recycling. A 1-month survey of 130 households was carried out in Can Tho City, the capital city of the Mekong Delta region in southern Vietnam. Household solid waste was collected from each household and classified into ten physical categories; especially plastic waste was sorted into 22 subcategories. The average household solid waste generation rate was 281.27 g/cap/day. The compostable and recyclable shares respectively accounted for high percentage as 80.74% and 11%. Regarding plastic waste, the average plastic waste generation rate was 17.24 g/cap/day; plastic packaging and plastic containers dominated with the high percentage, 95.64% of plastic waste. Plastic shopping bags were especially identified as the major component, accounting for 45.72% of total plastic waste. Relevant factors such as household income and household size were found to have an existing correlation to plastic waste generation in detailed composition. The household habits and behaviors of plastic waste discharge and the aspects of environmental impacts and resource consumption for plastic waste disposal alternatives were also evaluated.     

Indoor pesticide application practices and levels in homes of Bangkok Metropolitan Region

This study investigated the indoor application practices of pesticides in different homes located in urban, suburban, and rural areas of the Bangkok Metropolitan Region (BMR). A multi-stage stratified-judgmental sampling was applied to select 280 representative households in BMR for an in-depth questionnaire survey. We found about 71% of these households having mosquitoes as their main indoor nuisance. An inventory on the types and active ingredients was obtained through a shop-shelf survey. Among 22 available commercial products, 12 different active ingredients were observed with the pyrethroid containing pesticides are the most common. The stepwise regression analysis was conducted to reveal the statistical association between indoor levels of total pyrethriods (in the air and on the floor surface of homes) and the household application practices such as the overlap time period since the last application, application and storage locations, and frequency of applications, for instances.     

Health risk assessment of organochlorine pesticides with emphasis on DDTs and HCHs in abandoned agricultural soils

The aim of this study was to evaluate the consequence of changing land use from agriculture land to other use purposes with respect to OCPs non-cancer and cancer risk on human health, based on concentrations of DDTs and HCHs in soils collected from 55 locations representing 12 different land use types. There were no non-cancer risks of DDTs and γ-HCHs on adults and children, and there were very low cancer risks of DDD, o,p'-DDE, DDT, α-HCH, β-HCH, γ-HCH based on their total concentrations in all samples. Nonetheless, there were significant correlations of DDT to its metabolites (DDE and DDD) (r = 0.506 and r = 0.648) and DDE to DDD (r = 0.438) both at p < 0.01. OCP levels should be routinely monitored in different environmental media and food in order to verify whether there is fresh input. Their potential risks on human health should also be assessed.     

Community exposure to arsenic in the Mekong river delta, Southern Vietnam

We examined the daily inorganic arsenic (i-As) intake from drinking water and rice in 45 households (75 individuals) in the An Giang province, Southern Vietnam. The daily i-As intake ranged from 28-102 μg d(-1), equivalent to the daily dose of 0.6-1.9 μg d(-1) kg((body wt))(-1). Increased As concentrations were observed in human hair in the study location. Approximately 67% (n = 44), 42% (n = 28), and 15% (n = 10) of the hair samples had As levels exceeding 1, 3, and 10 μg g(-1), respectively. The total As concentrations in female and male hair correlated well with the total daily i-As intake. Measurement of As concentrations in the hair of people who were consuming or had previously consumed As from contaminated sources may help predict the onset of negative health effects. We suggested an application of the Bayes's theorem to calculate the probability that an individual in a population will acquire a negative health effect, given that the concentration of arsenic in the subject's hair has been determined.     

Concentrations,profiles, emission inventory,and risk assessment of chlorinated benzenes in bottom ash and fly ash of municipal and medical waste incinerators in northern Vietnam

Environmental Science and Pollution Research - Concentrations and congener profiles of seven di- to hexachlorinated benzenes (CBzs) were characterized in bottom ash and fly ash samples collected...