Tạp chí Khoa học Đại học Huế: Khoa học Trái đất và Môi trường
Tạp chí của Đại học Huế
Development potential for rooftop solar photovoltaic: case studies in commercial and industrial sectors of Hue City
A growing interest in solar energy development to ensure national power security and slow the onset of the current climate crisis has spurred the deployment of rooftop solar photovoltaic (PV) in cities in Vietnam. This paper aims to examine the technical and financial potential for rooftop solar PV development of two enterprises in Hue City, namely Truong Tien Plaza Commercial Center and Huetronics Joint Stock Company. The Google Earth Pro, the Roof Pitch Factor, and the on-site survey were employed to determine the rooftop characteristics of the two facilities. The technical potentials of Huetronics Company and Truong Tien Plaza were estimated at 1,256 kWh/day and 1,437 kWh/day, respectively. The financial analysis with Cost-Benefit Analysis reveals that both reference cases proved to be financially viable: the Discounted Payback Period is 5.8 years in the case of Huetronics and five years for Truong Tien Plaza; the Net Present Values are greater than zero, and the Internal Rate of Return is higher than the Cost of Capital. Such results are expected to assist in making informed policy decisions on the commercial and industrial rooftop solar PV development in Hue City.
Hue University Journal of Science: Earth Science and Environment
Calculating the volume of Tan Mieu lake in Thanh Noi area, Hue City, for the urban stormwater drainage system
Detention lakes, which are effective means of flood control, are highly effective in sustainable drainage solutions. Numerous factors diminish the regulating reservoir's function for urban drainages, such as the lake's small volume, an inadequate drainage system, and restricted outflow from the lake. Therefore, this study applies the method of limited rainfall intensity to calculate the stormwater flow into the lake and determine the volume of the detention lakes according to TCVN 7957: 2008 [1] to the sub-basin of Tan Mieu. It is confirmed that the volume of the lake in the region and the level of outflow from the lake, which are essential factors in flood mitigation, is not suitable for the rainfall characteristics of the area. The results show that with the planned outflow of Qx = 1/3 × Qt, the lake's actual capacity is roughly a half of the required lake capacity. With the option Qx = 1/2 × Qt, the actual volume of the lake is 1.2 times smaller than the calculated capacity. Therefore, increasing the lake's volume and outflow volume from the lake minimizes local flooding.
Greenhouse gas emission inventory of Can Tho City using Bilan Carbone method
Greenhouse gas (GHG) emission inventory has always been considered a crucial first step towards any development of climate change mitigation plans and measures. In this paper, the Bilan Carbone (Carbon Balance) version 6, an easy-to-use Excel-based GHG inventory tool developed by the French Environment and Energy Management Agency, is used to make an inventory of GHG emissions generated within Can Tho City’s territory. The data used for the direct and indirect GHG emissions were collected from Can Tho City’s 2020 Statistical Yearbook, relevant businesses, and administrative units. Ten sectors, namely Energy Industry, Industrial Processes, Tertiary Sector, Residential Sector, Agriculture and Fishing, Transporting Goods, Travel by People, Construction and Highways, End-of-life Waste, and Food, were taken into account for the related analysis. Considering all GHGs cited in the Kyoto Protocol coupled with emission factors updated for Vietnam and the magnitude of emission sources, we found out that the total GHG emission of Can Tho City in 2020 is 4,311,952 tons of CO2 equivalent (CO2e) with an average of approximately 3.5 tons of CO2e per capita. Residential Sector, Industrial Processes, and Travel by People contribute the most to the total GHG footprint of the city, in which Residential Sector accounts for the largest share (743,346 tons of CO2e, making up 17.2% of the total GHG emission). Industrial Processes ranks second with 727,504 tons of CO2e (representing 16.9%), and Travel by People is third with 619,823 tons of CO2e, accounting for 14.4%. Some scientific and realistic interpretations of such sectorial findings are also provided to facilitate the next step of initiating and carrying out associated GHG mitigation measures for the city.
Petrography and geochemistry of the Ben Giang and Van Canh granitoid in Sa Thay area, Kontum province
The Ben Giang and Van Canh complexes in Sa Thay area, Kon Tum province, are exposed as small blocks. Their petrographical composition includes hornblende biotite diorite, biotite granodiorite (the Ben Giang complex), fine-grained to medium-grained biotite granite and fine-grained biotite granite (the Van Canh complex). The SiO2 content varies from 59.84 to 77.29 wt.% coupled with an enriched alumina content (12.53–17.26 wt.%). All samples show a relatively high total alkali content (4.71–8.36 wt.%). The K2O/Na2O ratio is greater than 1, and a narrow variation of the ASI index (1.41–1.68) indicates that the rocks belong to the calc-alkaline series. The rocks’ negative anomalies of Ta, Nb, and Ti are typical for a magma melt generated at the edge of an active subduction zone. The low content of Sr (76–549 ppm, 347 ppm on average), Zr (111–296 ppm, 167 ppm on average), and Nb (9–15 ppm, 11 ppm on average) together with noticeably high Rb content (171–309 ppm), etc. imply that the Ben Giang and the Van Canh magmatic rocks derived from a mantle source, contaminated with crustal materials.
Drought situation in period 2000–2019 in Le Thuy and Quang Ninh districts, Quang Binh province
The drought index calculated from the results of rainfall measurements, satellite evaporation, and monitoring stations is used to build a map of aridity zoning in Le Thuy district and Quang Ninh district, Quang Binh province, with GIS technology based on Circular 14/2012/TT-BTNMT on technical regulations concerning land degradation investigation. Then, we evaluate the drought in the period of 2000–2019. Every year, drought occurs 4–6 months, primarily from May to July. Heavy drought takes place in the mountainous and coastal sandy areas in the Summer-Autumn crop. The results enable the managers to identify dry areas with different degrees of dryness, thereby offering more rational and effective land-use solutions.
Effect of rice husk and bamboo biochar on CH4 and N2O emission from alluvial paddy soil under laboratory conditions
Using biochar is a potential solution to reduce greenhouse gas emissions. This study was conducted to evaluate and compare CH4 and N2O emissions from paddy soil supplemented with rice husk biochar and bamboo biochar under two conditions: continuous flooding and alternating drying and wetting with a moisture of 90%. Each experiment was set up with seven treatments consisting of rice husk biochar and bamboo biochar at a portion of 0.1, 0.2, 0.5%, and a control (without biochar). In continuous flooding soil, CH4 emission was the primary process, and in 90% moisture paddy soil, N2O was the main emission. When rice husk biochar was amended at the rate of 0.2 and 0.5%, the total CH4 emissions were reduced by 27.66–45.19% compared with the control treatment (p < 0.05). Using rice husk biochar reduced total N2O emissions by 5.9–9.6 times while applying bamboo biochar reduced 4.1–5.9 times compared with the control treatment (p < 0.05). The supplement of rice husk biochar at 0.5% provided the highest efficiency of greenhouse gas emission was reduced at 8.9 times lower than the control and 50.3% lower than bamboo biochar at the same rate.
Weather complexions causing diluvial rains in Thua Thien Hue province in 2020
Based on meteorological and hydrological data series analysis and general geographical analysis, we evaluated the impact and role of weather patterns in the formation of rain and flood in Thua Thien Hue province. The results show eight primary combinations of weather patterns that caused rain and flood from 1981 to 2020. Cold air combined with storms or tropical depressions caused rain and produced the most floods (20.7%), followed by storm formation or tropical depression (18.6%) and cold air combined with high easterly winds (14.5%). Most of the significant floods occurring in Thua Thien Hue province were mainly due to the combined weather patterns causing heavy rains on a large scale. In 2020, six weather patterns caused rain and floods. In particular, the historic flood peak on October 9 resulted from a phenomenon called "floods and more floods" when a combination of four weather patterns (intensified cold air, tropical convergence band, high-altitude easterly wind development, and storm rain bands) appeared simultaneously, causing continuous and prolonged heavy rains and hence the water level on rivers to rise rapidly and remain at a high level. The results of this study are the basis for warning flood risks, serving the planning and socio-economic development of the locality.
Correlation between degree of saturation and soil shear strength of eluvial deluvial soil slopes along National road 49, Thua Thien Hue province, Vietnam
Landslides are common in the mountainous regions of Thua Thien Hue province (Vietnam) during rainy seasons, especially along National Road 49. The shear strength of soil is an essential parameter for landslide susceptibility assessment. This study aims to investigate the relationship between the degree of saturation and the shear strength by using the unconfined compression test for the eluvial deluvial soil slopes in the weathering crusts of Long Dai formation, Ben Giang – Que Son complex and Dai Loc complex, along National Road 49. The soil shear strength in [five] areas where slope landslides occur varies from 0.56 to 0.17 kG/cm2 when the degree of saturation increases from 58.5 to 97.4%. At the same time, the results also show that the shear strength and the degree of saturation are correlated from strong to very strong degrees (R > 0.7). The results are a useful reference, helping to clarify the characteristics of the shear strength according to the degree of saturation and making the assessment of slope stability along the studied road better in future.
Characteristics of weathering crust developing on Ben Giang – Que Son granodiorite in Nam Dong, Thua Thien Hue
Based on field surveys and indoor analyses, we present major characteristics of weathering crust developing on the Que Son granodiorite in the Nam Dong area, Thua Thien Hue (Central Vietnam), including zonation, chemical and mineral compositions, particle-size distribution and physicomechanical properties. The results show that the granodiorite is highly weathered, generating an 8–10 m thick weathering crust with clear zonation. Chemically, the weathering crust is classified into the SiAlFe type with a high concentration of aluminum (Al2O3: 24,5 wt.%) coupled with an extremely low concentration of calcium and sodium (CaO: 0,1 wt.%, Na2O: 0,1 wt.%); the chemical index of alteration is very high at 91,9. Weathering products are predominantly composed of clay and sandy clay. The weathering products consist of clay and silt with a fraction of clay and dust in the completely weathered zone at 65,7–87,8 wt.%, and this fraction decreases with depth. The clay minerals include kaolinite, illite and allophane/ imogolite. The particle-size composition and physicomechanical properties of the soils (moisture, volumetric soil density, saturated index) tend to gradually decrease in deeper zones. These parameters tend to increase in the rainy season, particularly during and/or after long-time heavy rain, making soils saturated, increasing volume and stability lost, which generates landslide masses in the talus slopes, notably along Road 14B and other minor roads in the area.
Potential of water resources in Chang Riec area, Tay Ninh province and solutions for exploiting and using water economically
The residential area in Chang Riec hamlet, Tan Lap commune, Tan Bien district, Tay Ninh province, was built near the border with Cambodia. Located in the border area and 30 km from the centre of Tan Lap commune, Chang Riec hamlet badly needs underground water for daily consumption. Various field methods, such as routing, exploratory drilling, geophysical measurements, and balance and hydrodynamic method calculations, were carried out to assess the potential of water resources. The results of the investigation and calculation show that the surface water flow is insignificant. The water level is low, and water often dries up in the dry season. The total underground water potential in the studied area is estimated at 224,151 m3/day, and the exploitable reserve of underground water in the area is 67,245 m3/day. However, to ensure a long-term operation and suitable exploitation efficiency of the drilling holes, we suggest the maximum exploitation flow at 75% of the forecasted exploitation flow of the boreholes.
Landscape use efficiency for agro-forestry in River Bung basin, Quang Nam province
The River Bung basin is divided into 92 landscape types with seven use-type groups, three types of which are used for agro-forestry. The landscape-use types chosen to evaluate are upland rice, maize, and cassava; banana, pineapple, and Dangshen (Codonopsis sp.); and production forests. The methods used in this study include cost-benefit analysis combined with the assessment method by the marking scale from low to high, namely 1, 2, and 3. After evaluating the components, we assessed landscape use efficiency by product averaging. The assessment shows that the landscape-use effectiveness for planting dangshen exhibits a high level (2.87 marks); bananas and pineapples, and afforestation have a medium level at 2.22 and 2.08 marks; production forests and annual crops (upland rice, maize, cassava) are in a low level (from 1.26 to 1.54 marks). These results are one of the scientific bases for selecting the most appropriate land-use type among the existing ones for the rational use of sustainable agro-forestry.
Oxidation of ammonia with three bacterial strains belonging to genus Bacillus isolated from pig-farm wastewater after biogas tanks
The biological removal of ammonia plays an essential role in the wastewater treatment technology. The oxidation of ammonia is the first step converting ammonia to nitrite, which is then transformed to nitrate as an intermediate substance and finally biotransforming to free nitrogen. A variety of bacterial strains with the ability to oxidation of ammonia were published. In this study, three ammonia-oxidizing bacterial strains were isolated from wastewater after biogas tanks of industrial pig farms in Ha Tinh province, named Bacillus megaterium HT1, Bacillus licheniformis HT1, and Bacillus subtilis HT1. The biotransformation of ammonia was monitored by the spectrum analysis method. The optimal pH and temperature for the three isolates’ growth are 7–7.5 and 30–37 °C. They can oxidize ammonia with a concentration of up to 750 mg/L within five days of incubation, and their ammonia-oxidizing rate is proportional to the concentrations of ammonia tested. The bacteria work well in the medium containing NaCl at a concentration of 3%. Besides, the low level of DO (0.1 mg/L) does not significantly affect their growth and ammonia-oxidizing activity. The results of this study can contribute to the diversity of ammonia-oxidizing bacteria and bring great potential to apply them to treat ammonia in wastewater.
Inactivation of Vibrio spp. in water using micro-nano-bubbles, ultrasound, and hydrogen peroxide
Recently, the development of water disinfection technology that does not generate chemical residues or by-products has attracted much research interest. This study presents the results of Vibrio spp. disinfection using a combination treatment of micro-nano-bubbles (MNBs), ultrasound (US), and hydrogen peroxide (H2O2). The bactericidal performance of the combined treatment was conducted at various H2O2 dosages and airflow rates. The results show that with H2O2 added at ~30% of a normal dose (required for sufficient disinfection by H2O2 alone), disinfection efficiency of the combined MNBs/US/H2O2 treatment was greatly enhanced and was higher than that of individual treatments (US or H2O2). Specifically, under treatment conditions (initial bacterial density of 105-106 CFU/mL and salinity of 20‰), the combined treatment of MNBs (1.5 L/min)/US (28 kHz)/H2O2 (0.9 mg/L) achieved a synergy value of 3.3 log and completely inactivation (5.4 log reduction) of Vibrio spp. within 60 min. Meanwhile, disinfection with H2O2 (0.9 mg/L) led to only 1.7 log reduction, and disinfection with US (28 kHz, 100 W) reduced only 0.5 log within 60 min. These results promise an alternative method for brackish water disinfection applications such as aquaculture water treatment.
Life cycle assessment for solid waste management: a case study of Hue City
Life cycle assessment (LCA) is a decision support tool used worldwide, and currently, it is also applied to solid waste management. In this research, we built four SWM scenarios for Hue City. The scenario life-cycle impacts were assessed by using the IMPACT 2000+ method and implemented on the OpenLCA software to decide the most environmentally friendly solid waste management solution for Hue City. The results indicate that the S4 scenario – Waste to energy (–2,1 point impact) is the most environment-friendly. The S1 scenario – Landfill (0,218 point impact) is the worst scenario related to the environmental effects aspect. Landfill gas collection (landfill gas to energy) and recycling have reduced the adverse effects on the environment.
CULTIVATION OF AEROBIC GRANULAR SLUDGE WITH INDUSTRIAL WASTEWATER IN SEQUENTIAL BACTH REACTOR
Cultivation of aerobic granular sludge from activated sludge was carried out in 02 lab-scale Sequential Batch Reactors (SBRs) named R1 and R2. During the experimental period, both reactors were operated in similar condition with 240 minutes of cycle time and an airflow rate of 6L/min. R1 was fed with industrial wastewater collected from Phu Bai Industrial Zone, Thua Thien Hue Province, meanwhile, R2 has used a mixture of industrial and prepared synthetic wastewater with stepwise feeding of different volumetric fraction including 1:3; 1:1, and 3:1. After 7 weeks of operation, tiny granular size less than 1mm was observed, sludge biomass reached 5,8 g/L but filamentous sludge still appeared in R1. Meanwhile, in R2, granular sludge size of 1mm was dominant and biomass reached 6,8 g/L which was higher than its concentration in R1. Granules sludge in both reactors has good settling properties with a low SVI of 30-32 mL/gTSS. The removal efficiencies of organics (COD), ammonium (NH4-N), and phosphorus (P-PO4) in steady-state operation of R1 and R2 were stabled at 92-94%, 93-96%, and 65-71%, respectively. The rate of conversion NH4-N to NOx-N increased from 7-12% to 43-52% at the end of the experimental period. It was indicated that the nitrification of sludge was leveled up with the appearance of granular sludge and the development of biomass. Furthermore, in 43-52% rate of conversion NH4-N to NOx-N, the percentage of NH4-N converted to NO3-N accounting for about 40-47%, this result demonstrated that the nitrification process was nearly completed in both reactors.
CHARACTERISTICS OF LANDSCAPE IN KON RIVER BASIN, BINH DINH PROVINCE
Abstract: Kon River basin has diverse and original of natural conditions and natural resources. The results of the study on the natural division of the territory and forming the landscape map of the Kon river basin, the scale of 1/100.000 show that: Kon river basin is divided into 184 categories in the landscape classification system of the territory, including seven levels: landscape systems, landscape sub-systems, landscape types, landscape classes, landscape sub-classes, landscape species and landscape kind. These results are scientific (and practical) basis for establishing some eco-economic models of the Kon river basin, Binh Dinh province. Key word: Landscape classification, landscape map, river basin landscape
THE CURRENT SITUATION OF GEOLOGICAL ENVIRONMENTAL HAZARDS IN THE MINING AREAS OF NATURAL BUILDING MATERIALS IN PHU LOC DISTRICT, THUA THIEN PROVINCE.
The article introduces some research results on the current status of geological environmental hazards in the mining areas of natural building materials in Phu Loc district, Thua Thien Hue province. On the basis of sampling for analysis phase 1 (9/2019), surface water and groundwater are polluted with some parameters such as pH, COD, BOD5 and Pb. It is alarming that the Pb content in surface water exceeds the permitted limit of 45 - 1380 times and in the underground water is 190 - 710 times, both at extremely serious pollution levels. The reason for this increase may be due to the regional geological environment that already contains high levels of this element and mining activities can also contribute significantly to the dispersion of Pb into the environment. However, the results of sampling for analysis phase 2 (11/2020) showed that except for pH, all other analytical parameters were within the allowable limits. These results have different values ​​compared to the analysis results of phase 1. The reason is that this sampling was carried out after the historic flood (10 – 11/2020), the water sources were diluted. because rain water leads to lower analytical indicators. Besides surface water and groundwater samples, soil samples (surface sediments) taken in phase 1 (9/ 2019) also have much higher values ​​of analytical criteria than those taken in phase 2 (11/2020). The cause is also due to the historic flood (10 – 11/2020) that washed away surface sediments. On the other hand, mining activities are also one of the causes of the decrease in forest cover due to the reduction of forest cover and loss of vegetation cover, leading to biodiversity loss, changing the nature landscape, changing topography - geomorphology of many points in the area.
KINETICS OF NO3- ADSORPTION ONTO BIOCHAR FROM MIMOSA PIGRA L.
USE OF WATER QUALITY INDICES FOR EVALUATION OF THE SAIGON RIVER WATER QUALITY FOR SPECIFIC PURPOSES
The Saigon river is one of the most important surface water sources in Binh Duong province. River water is used for many different purposes in the province. This study aimed to assess the water quality of the Saigon river and its suitability for specific uses. Based on water quality data obtained monthly from December 2019 to November 2020, water quality indices were applied to evaluate the water quality of the river for purposes such as public water supply, agriculture, industry, and aquatic life protection. Inverse distance weighted (IDW) interpolation in geographic information system (GIS) was used to produce visualized zoning maps for river water quality. The results showed that the WQIs varied from 10 to 65 for public water supply, 67 to 100 for agriculture, 26 to 100 for industry, and 3 to 83 for aquatic life protection. The river water could be used for the purposes of agriculture and industry, but was not suitable for public water supply and aquatic life protection. The findings provide useful information for water resource management and water pollution control of the river.
EVALUATION OF THE COAL RESERVE RELIABILITY IN THE CAO SON MINE, QUANG NINH PROVINCE BY USING GEOMATHERMATIC MODELS
Abstract. The Cao Son mine is located in the southern part of the Quang Ninh province. It belongs to the Hon Gai coal zone, where many coal resources have been estimated in Vietnam. Based on synthesizing and processing data of the mining geological parameters by using stable random function and statistical methods, results show that the coal reserve reliability depends on some elements such as geological conditions, system and the grid exploration density, and methods of interpolated geological documents, and estimating of mineral resources methods. The stable random function for calculating the affected range indicates that most of the exploration works satisfy the appropriate pattern grid exploration for reserve level 122 in the Cao Sơn mine. The statistic models based on the confidence probability of 0.90 are applied in this paper to estimate coal reserve reliability in the study area, resulting in ± 15.36 ÷ ± 17.36% of coal reserve errors. It indicates that calculating coal resources during the exploration process is good enough for the exploited design. Results also provide an overview of the affected elements of coal resource reliability, serving as a basis for determining the errors of coal resources in the Cao Son mine. These can be applied to other deposits occurring in similar geological settings. Keywords: coal reserves, geomathermatic models, Cao Son mine, Quang Ninh province
CONSOLIDATION CHARACTERISTICS OF A SILTY CLAY: CONCERNING THE EFFECT OF SOIL DISTURBANCE
In this paper, undisturbed specimen of a silty clay constituting of Phu Bai formation (ambQ21-2 pb) was collected from boreholes in Hue city and surrounding areas. The soil, under both undisturbed and disturbed conditions, was then subjected to standard one-dimensional consolidation tests with 7 loading increments. It is shown from the experimental results that the time to the end of primary consolidation (EOP), determined by Log Time method (tLT) and 3-t method (t3T), decreases with the load increment and under the same vertical stress, the primary consolidation of disturbed silty clay finish at a shorter time than those of the undisturbed one. The coefficient of secondary consolidation (Cα) increases with the vertical stress and reaches the maximum values before decreasing. The obtained values of Cα = 0.005 - 0.020 suggest a relatively low secondary compressibility of the silty clay constituting of Phu Bai formation.
DEVELOPMENT OF BIOFILM ON POLYURETHANE FOAM AND ITS APPLICATION IN A BIO-TRICKLING FILTER FOR TREATMENT OF ODOR FROM DOMESTIC SOLID WASTE
This study investigates the ability of a self-fabricated bio-trickling filter using commercial polyurethane foam as bio-media for treatment of odor-causing gases (e.g., ammonia, hydrogen sulfide, and mercaptans) under different nitrogen loadings in gas and liquid phases. The experimental results showed that the biological filter operating with a gas flow rate of 11.44 m3/h and an empty bed residential time of 19.67 s could treat the multi-components emitted from domestic solid waste. Ammonia treatment efficiency was achieved in the range of 87.3 to 99.7% with the highest ammonia input concentration of l47.3 mg/m3. The efficiency of mercaptans treatment was from 60.2 to 72.8% with an input concentration of about 8 mg/m3 while the low input and output concentrations of hydrogen sulfide were found (≤ 0.002 mg/m3). Besides, there was a significant difference between elimination capacity of NH3-N (gas phase) and accumulated capacity of NH4+-N and NO3--N (liquid phase) although the ammonia treatment efficiency was very high, which could be attributed to the denitrification process. The results from this study hence suggest using bio-trickling filter for effective treatment of NH3 and other odor in gas generated from domestic solid waste.
APPROACHING DASYMETRIC TECHNIQUE IN MAPPING POPULATION DENSITY - A CASE STUDY OF THUA THIEN HUE PROVINCE
The Dasymetric mapping technique approach accurately reflects the population distribution by territory, serving as the basis for urban and living space planning, socio-economic development, and infrastructure. This paper focuses on approaching Dasymetric mapping techniques to create a population density map for Thua Thien Hue Province. By integrating Dasymetric mapping techniques and geographic information system (GIS), component maps have been developed to establish the population density map such as weighted RA, total population N/ward, E-coefficient, AT total pixel/ward. The initial results show that the population distribution according to the Dasymetric mapping technique accurately reflects the people living in an administrative unit. Besides, the paper also developed a population density map by traditional density techniques of Choropleth, then compared the results obtained with Dasymetric mapping techniques. From the comparison between the two methods, it reveals that, with the Dasymetric method, the population density of Thua Thien Hue province in 2020 is reality distributed with the highest at 29,26 people/900 m2 (0,033 people/km2) and the lowest is 0 (in places where the water surface). Meanwhile, the Choropleth method shows that the most significant population density is 0,01 people/m2 (9 people/900 m2), the lowest is 0,02 people/900 m2 and is homogeneous for the whole commune/ward territory. Thereby, further confirmed the accuracy, visual representation of population distribution according to the population statistics space of the Dasymetric method. Keywords: The Dasymectric mapping technique, population density, GIS, Thua Thien Hue
IMPROVING THE STABILITY OF BENTONITE SLURRY USING GELLAN GUM BIOPOLYMER
The distinctive properties of bentonite such as hydration, swelling, water absorption, ion adsorption, high viscosity, and thixotropy make it a valuable material for many applications in geotechnical engineering such as hydraulic barriers, drilling slurry, and landfill liners. Many additives such as cement, hay fiber, and polymer have been used to enhance the engineering performance of bentonite slurry, which are proved in respected research. This study introduces gellan gum as a friendly environmental additive that improves bentonite slurry stability when bentonite is used for hydraulic barriers/walls. The bentonite was treated with different gellan gum concentration as 0% (untreated); 2%; 3%; 4%, 5%, 6% and 7% to the mass of distilled water. A series of unconfined compression tests were conducted on gellan gum – bentonite mixture. The test results show the effect of gellan gum on the unconfined compressive strength of bentonite slurry in initial and thermal curing conditions.
COMPARE INFLUENCES OF HORIZONTAL AND VERTICAL MSE WALL DIMENSIONS WITH GEOCOMPOSITE BACK DRAINAGE SYSTEM TO MAXIMUM STEADY STATE PHREATIC LEVEL
Nowadays, with serious risks to the mechanically stabilized earth (MSE) instability especially for soil mass behind the wall face caused by heavy rainfall. Come from high drainage ability, geocomposite is regarded as an appropriate material for drainage purposes in many geotechnical structures, including MSE walls. However, there are insufficient researches investigated MSE wall geometry design especially with wall dimension oriented follow 2D dimension as horizontal and vertical. This paper presents a series of PLAXIS numerical simulations to investigate the influences of MSE wall dimensions and drainage capacity on seepage responses inside the protected zone of the wall. The research results indicated that the distance from the upstream water source to the drainage face (L) influences most to the maximum steady state phreatic level (ho) variation inside the protected zone. In total comparison that shown the horizontal wall dimensions have more affects on ho drops than vertical wall dimensions.
IMPACT OF FLOOD ON WATER QUALITY: A CASE STUDY IN A FLOOD-PRONE AREA OF THUA THIEN HUE PROVINCE
People living in flood-prone areas are vulnerable to damages caused by annual floods, including changes in water quality. Seasonal flooding alters water quality in many aspects by introducing silt, nutrients, organic compounds, and sometimes bacteria. In this study, 50 household interviews in Quang Thanh commune - Quang Dien district, the flood-prone area in Thua Thien Hue province, were conducted to identify the flood characteristics. A total of 36 water samples, including surface- and pipe water, were collected and analyzed the basic parameters in December 2019 and June 2020 to preliminarily demonstrate the main impacts of the flood on water quality. In general, in some aspects, flood helped reduce the organic contaminants (based on DO, BOD, and COD values assessment) and salinity, and somehow increase the total coliform and E. coli at most of the sampling stations. Unpredictable weather and hydropower plant from upstream were believed to be the main causes of flood volume reduction in recent years, which also contributed to changes in water quality.
APPLICABILITY OF NAM O WHITE MARINE SAND AS AN ALTERNATIVE FINE AGGREGATE FOR CONCRETE IN QUANG NAM
Nowadays, the making of engineering concrete from appropriate local material becomes a more important concern. This paper aims to use the different methodological systems to evaluate the potential reserves of Nam O white marine sand in Quang Nam province, this sand type is used for mixing with other local materials as concrete fine aggregate which includes fine crushed stone and Thu Bon river sand. This white marine sand is a high potential for replacing partly traditional river sand being run out. Research results indicate that study white sand has a wide distribution area, favorable exploitation conditions, and potential mining reserves reach up to 8017 mil. m3. The technological properties of white marinesand and mechanical properties of concrete, as well as these design mixing ratios, meet the technical requirements for concrete fine aggregates with compressive strength from 250 - 260 daN/cm2. This concrete compressive strength (Rc) and flexural strength (Rf), extracted from nondestructive methods, follow a logarithmic correlation like typical concretes. Especially, Rc and Rf rises considerably and rapidly in the first period from 3 to 28 days and drops slowly after 28 days.
LAND USE TYPES AND SOIL CHARACTERISTICTS: A CASE STUDY IN HUONG VINH COMMUNE, HUONG TRA TOWN, THUA THIEN HUE PROVINCE
This research carried out in Huong Vinh commune, Huong Tra town, Thua Thien Hue province aimed to identify types of land use and soil characteristics. Results showed that five crops are found in Huong Vinh commune including rice, peanut, sweet potato, cassava and vegetable. There are two major soil orders with four soil suborders classified by FAO in Huong Vinh commune including Fluvisols (Dystric Fluvisols, Gleyic Fluvisols and Cambic Fluvisols) and Arenosols (Haplic Arenosols). The results from soil analysis showed that three soil suborders including Dystric Fluvisols, Gleyic Fluvisols and Cambic Fluvisols belonging to Fluvisols were clay loam in texture, low pH, low in OC, total N, total P2O5 and total K2O. Meanwhile, the Haplic Arenosols was loamy sand in texture, poor capacity to hold OC, total N, total P2O5 and total K2O
Journal of Earth Science and Environment
VULNERABILITY TO FLOODING AND COPING BEHAVIOR FOUND IN HOUSING CONDITION: A CASE STUDY IN VAN QUAT DONG VILLAGE, TAM GIANG LAGOON AREA, CENTRAL VIETNAM
Vietnam is a country that is suffered from frequent natural disasters. The most common types of natural disasters experienced are typhoon and flood. From 1951 to 2010, there were 166 typhoons come to Vietnam, of which 67 % hit the central region, 25 % to the north and 8 % to the south of the country. Typhoons bring heavy rains and high tides which accelerate floods, particularly in the coastal and lagoon areas of Central Vietnam. Identification of vulnerability to flooding and coping behavior of local people is required in the efforts to strengthen local capacity related to livelihood security in the study area. This study aims at characterizing the vulnerability of housing condition to flooding and the coping behaviors of local people after experienced big floods in Tam Giang lagoon area, Central Vietnam. Measurement of house’s foundation, observation of types of housing, interview to collect information about the water level during the events of big floods, year of construction and change of people’s behavior after the 1999’s flood were conducted with 427 households in Van Quat Dong village where four big flooding occurred in 1983, 1999, 2007 and 2009 during the last 30 years. The study shows that the 1999’s flood was the biggest flood with water height reached to 148.7 ± 23.9 cmfrom house floor and 222.6 ± 15.4 cmfrom ground level. The households located in the eastern part of the village are recognized more vulnerable to flood due to the lower altitude. The temporary and semi-permanent houses, which share 77.0 % to the entire houses, are considered to be relatively vulnerable to flooding due to weak housing materials and low height of foundation. The houses which categorized to permanent and semi-permanent types constructed after the 1999’s flood have higher foundation than the other houses constructed before the 1999’s flood. The raising of foundation height of permanent and semi-permanent houses, as well as an increase in numbers of two-storey houses, are recognized to be a behavior of local people to cope with flooding. The study also shows the relationship between the poverty level and the coping behaviors of households. Some of poor households in the village are still not in good preparedness to flooding. It suggests that poverty level of household concerns to the vulnerability to flooding and, therefore, rural development assistance to improve household economy for poverty alleviation is required in the efforts to strengthen local capacity related to livelihood security.
Characteristics of phosphate phase (fluorapatite and monazite) in the South Nam Xe carbonatites, Northwest Vietnam
This paper presents characteristics of appearance and mineral chemistry of phosphate phase, including fluorapatite and monazite in the South Nam Xe carbonatite dykes in Northwest Vietnam. These minerals occur in both calcio- and ferrocarbonatites in various modes. Most of the fluorapatites in the calciocarbonatites are oblong to elongated, and have sharp contacts with calcite, aegirine and phlogopite suggesting their primary origin; whereas those in the ferrocarbonatites are commonly present in forms of stubby to perfect hexagonal prismatic crystals, which partly replaced by the monazite. The monazites in the ferrocarbonatites also occur as hundreds micro isolated crystals, which associated with ankerite, feldspar, magnetite and phlogopite. Contents of fluor and rare earth elements (REE) are relatively high (F up to 4.26 wt.%; REE up to 5.19 wt.%) indicating a F- and REE-enriched precipitation for the carbonatites. The enrichment in light REEs in the fluorapatite is paired with an enrichment in Na, varying from 0.25 wt.% to 0.89 wt.%. The replacement of REE and Na for Ca in the fluorapatites, which leads to change in CaO/P2O5 ratios might show an open system where Ca and P are added to areas of the fluorapatite depleted in light REE (LREE). REE contents in the monazite show a very limited variation, and are mainly composed of La, Ce and Nd (La2O3 = 21.09-22.72 wt.%, Ce2O3 = 32.82-33.35 wt.%, Nd2O3 = 6.96-8.20 wt.% in calciocarbonatite; La2O3 = 16.61-17.39 wt.%, Ce2O3 = 32.07-33.52 wt.%, Nd2O3 = 8.92-10.94 wt.% in ferrocarbonatite).