Assessing relative vulnerability to sea-level rise in the western part of the Mekong River Delta in Vietnam

The Mekong River Delta in Vietnam plays a crucial role for the region in terms of food security and socioeconomic development; however, it is one of the most low-lying and densely populated areas in the world. It is vulnerable to seawater incursion, flood risk, and shoreline change, exacerbated as a consequence of sea-level rise (SLR) related to climate change. This study examined the Kien Giang coast in the western part of the delta, comprising seven coastal districts (namely Ha Tien, Kien Luong, Hon Dat, Rach Gia, Chau Thanh, An Bien, and An Minh), the economy of which is important in terms of agriculture and aquaculture. The analytical hierarchical process (AHP) method of multi-criteria decision making was integrated directly into geographic information systems (GIS) to derive a composite vulnerability index that indicated areas most likely to be vulnerable to SLR. The hierarchical structure comprised three key components: exposure (E), sensitivity (S), and adaptive capacity (A), at level 1. At the next level, 8 sub-components were mapped: seawater incursion, flood risk, shoreline change, population characteristics, land use/land cover, and socioeconomic, infrastructure, and technological capability, beyond which a further 22 variables (level 3) and 24 sub-variables (level 4) related to vulnerability were also mapped. Variables were assigned weights for incorporation into AHP pairwise comparisons after discussion with stakeholders. Maps were generated to visualise areas where the relative vulnerability was very low, low, moderate, high, and very high. Societal data were generally only available at district level; however, several regional patterns emerged. Relatively high exposure to flooding and inundation, salinity, and moderate loss of mangroves occurred along the coastal fringe of each district. This western section of the delta, which is low-lying and remote from the distributaries that carry sediment to the coast, appears to be particularly vulnerable. The most sensitive areas tended to be ethnic households engaged in rice cultivation and with moderate population density. The least adaptable areas consisted of high numbers of poor households, with low income, and moderate densities of transport, irrigation and drainage systems. Most coastal districts were determined to be moderately to relatively highly vulnerable, with scattered hotspots along the coast.     

Fatty acids composition of Caenorhabditis elegans using accurate mass GCMS-QTOF

The free living nematode Caenorhabditis elegans is a proven model organism for lipid metabolism research. Total lipids of C. elegans were extracted using chloroform and methanol in 2:1 ratio (v/v). Fatty acids composition of the extracted total lipids was converted to their corresponding fatty acids methyl esters (FAMEs) and analyzed by gas chromatography/accurate mass quadrupole time of flight mass spectrometry using both electron ionization and chemical ionization techniques. Twenty-eight fatty acids consisting of 12 to 22 carbon atoms were identified, 65% of them were unsaturated. Fatty acids containing 12 to17 carbons were mostly saturated with stearic acid (18:0) as the major constituent. Several branched-chain fatty acids were identified. Methyl-14-methylhexadecanoate (iso- 17:0) was the major identified branched fatty acid. This is the first report to detect the intact molecular parent ions of the identified fatty acids in C. elegans using chemical ionization compared to electron ionization which produced fragmentations of the FAMEs.     

Transition of human and livestock waste management in rural Hanoi: a material flow analysis of nitrogen and phosphorus during 1980–2010

Journal of Material Cycles and Waste Management - Human and livestock waste, i.e., excreta, were intensively used in crop cultivation in Asia over the years. However, rapid economic growth induced...     

Current and future solid waste management system in Northern Viet Nam with focus on Ha Noi: climate change effects and landfill management

The contribution investigates the solid waste management system in Ha Noi under consideration of the interrelation between climate change effects and landfill management by means of a cause-and-effect-analysis as well as water balances using the HELP 3.95 model and gas emission data, followed by a Strength, Weakness, Opportunities, Threats (SWOT) analysis. Even landfills are sources of methane (CH₄) emissions they are also impacted by climate change. The main effects on landfill sites are the change of climatic conditions, namely the regional water balance, extreme precipitation and storm events. The results of the water balance model results show that a geomembrane surface sealing can reduce the leachate formation significantly, a fact that is also valid for the climate change scenario with higher precipitation. The risk of flooding and erosion at the landfill sites increases, which will require a customized water management. In parallel landfill gas offers the opportunity for recovery of Greenhouse Gases (GHG) and the generation of renewable energy. Some further management options are wind turbines, photovoltaic systems or biomass for biogas conversion, which was grown on closed landfill sites. The inclusion of climate friendly management options of closed landfills in a “Good Landfill Aftercare Practice” is recommended.     

Recent levels of organochlorine pesticides and polychlorinated biphenyls in sediments of the sewer system in Hanoi, Vietnam

The occurrence, temporal trend, sources and toxicity of PCBs and organochlorine pesticides were investigated in sediment samples from the sewer system of Hanoi City, including the rivers Nhue, To Lich, Lu, Set, Kim Nguu and the Yen So Lake. In general, the concentrations of the pollutants followed the order DDTs > PCBs > HCHs (β-HCH) > HCB. However, the pollution pattern was different for the DDTs and PCBs when the sampling locations were individually evaluated. The concentrations of the DDTs, PCBs, HCHs, and HCB ranged from 4.4 to 1100, 1.3 to 384, <0.2 to 36 and <0.2 to 22 ng/g d.w., respectively. These levels are higher than at any other location in Vietnam. Compared to measurements from 1997, the DDTs, PCBs, β-HCH and HCB levels show an increasing trend with DDT/DDE ratios, indicating very recent inputs into the environment although these persistent compounds are banned in Vietnam since 1995.     

Household solid waste generation and characteristic in a Mekong Delta city,Vietnam

This study was undertaken to evaluate the quantity and composition of household solid waste to identify opportunities for waste recycling in Can Tho city, the capital city of the Mekong Delta region in southern Vietnam. Two-stage survey of 100 households was conducted for dry season and rainy season in 2009. Household solid waste was collected from each household and classified into 10 physical categories and 83 subcategories. The average household solid waste generation rate was 285.28 g per capita per day. The compostable and recyclable shares respectively accounted for 80.02% and 11.73%. The authors also analyzed the relations between some socioeconomic factors and household solid waste generation rates by physical categories and subcategories. The household solid waste generation rate per capita per day was positively correlated with the population density and urbanization level, although it was negatively correlated with the household size. The authors also developed mathematical models of correlations between the waste generation rates of main physical categories and relevant factors, such as household size and household income. The models were proposed by linear models with three variables to predict household solid waste generation of total waste, food waste, and plastic waste. It was shown that these correlations were weak and a relationship among variables existed. Comparisons of waste generation by physical compositions associated with different factors, such as seasonal and daily variation were conducted. Results presented that the significant average differences were found by the different seasons and by the different days in a week; although these correlations were weak. The greenhouse gas baseline emission was also calculated as 292.25 g (CO₂ eq.) per capita per day from biodegradable components.     

Esterification of sugarcane bagasse by citric acid for Pb2+ adsorption: effect of different chemical pretreatment methods

In this study, different pretreatment strategies of sugarcane bagasse prior to citric acid modification were investigated in terms of Pb²⁺ adsorption capacity. Pretreatment strategies included the use of NaOH, HCl, and C₂H₅OH in various concentrations. In order to fundamentally understand how these pretreatment methods affect the modification of sugarcane bagasse by citric acid as well as the Pb²⁺ adsorption capacity of sugarcane bagasse, three main components of sugarcane bagasse namely cellulose, hemicellulose, and lignin were isolated and esterified by citric acid under the same conditions. ATR-FTIR, XPS, SEM, and an analysis of the number of carboxylic acid groups were used to investigate the physicochemical and chemical properties of the materials. These three components were proved to participate in adsorption and induce the esterification with citric acid. Hence, pretreatment with ethanol and 0.01 M NaOH which could retain cellulose, hemicellulose, and lignin in sugarcane bagasse achieved a high Pb²⁺ adsorption capacity, i.e., 122.4 and 97 mg/g after the esterification with citric acid. In contrast, pretreatment with 0.5 M NaOH and 0.1 M HCl removed lignin and hemicellulose, leading to the lowest value of approximately 45 mg/g for citric acid esterified-pretreated sugarcane bagasse. XPS analysis and number of carboxylic group measurement confirmed the esterification between bagasse and citric acid. To understand the adsorption mechanism of adsorbent, two kinetic models including pseudo-first-order model and pseudo-second-order model were applied. The experimental data were well described by the pseudo-second-order model. The adsorption isotherm data were fitted Langmuir and Freundlich.

     

Sorbent-based devices for the removal of spilled oil from water: a review

Environmental Science and Pollution Research - Always, oil spills do cause serious and dire consequences for the environment, nature, and society that it consumes much time and socio-economic...     

Status of water use and potential of rainwater harvesting for replacing centralized supply system in remote mountainous areas: a case study

Environmental Science and Pollution Research - The failure of the centralized water supply system forced XY community to become more dependent on uncertain and unstable water sources. The results...     

Comparative mammalian cell cytotoxicity of wastewater with elevated bromide and iodide after chlorination, chloramination, or ozonation

Recycling wastewater is becoming more common as communities around the world try to better control their water resources against an increased frequency of either prolonged droughts or intense flooding. For communities in coastal areas, wastewaters may contain elevated levels of bromide(Br~-) and iodide(I~-) from seawater intrusion or high mineral content of source waters. Disinfection of such wastewater is mandatory to prevent the spread of pathogens, however little is known about the toxicity of wastewater after disinfection in the presence of Br~-and I~-. In this study we compared the induction of chronic cytotoxicity in mammalian cells in samples of municipal secondary wastewater effluent amended with elevated levels of Br~-/I~-after disinfection by chlorine, chloramines or ozone to identify which disinfection process generated wastewater with the lowest level of adverse biological response. Chlorination increased mammalian cell cytotoxicity by 5times as compared to non-disinfected controls. Chloramination produced disinfected wastewater that expressed 6.3 times more cytotoxicity than the non-disinfected controls and was 1.3 times more cytotoxic than the chlorinated samples. Ozonation produced wastewater with cytotoxicity comparable to the non-disinfected controls and was at least 4times less cytotoxic than the chlorine disinfected wastewaters. These results indicate that compared to chlorination and chloramination, ozonation of wastewater with high Br~-/Ilevels yielded the lowest mammalian cell cytotoxicity, suggesting its potential as a more favorable method to disinfect wastewater with minimizing the biological toxicity in mind.