Tạp chí của Tổng Cục Khí tượng Thủy văn
Applying a two-dimensional open-source hydrodynamic model to evaluate the riverbed change in the upstream of the Cuu Long River, An Giang Province
Riverbank erosion in the Mekong Delta, particularly along the Tien and Hau rivers and some primary and secondary tributaries, is undergoing highly complex and unpredictable changes, resulting in significant damage to the affected areas. The phenomenon of riverbank erosion here is caused by multiple factors, including intensified human activities such as sand mining, infrastructure development, and climate change. In recent years, the increasing activities of upstream Mekong River projects have led to a reduction in sediment deposition in the delta, which is considered one of the significant contributing factors to the increasing incidence of riverbank erosion. This paper will apply and build a two-dimensional open-source model (TELEMAC) to simulate in detail the sediment transport process during the 3-year period from 2017 to 2019 on the upstream section of the Tien and Hau rivers in An Giang province to evaluate and assess the sediment imbalance during this period and identify trends in riverbed erosion and deposition. As a result, in 3 years, the total silt deficit on the Tien River section is -36.6×106 m3, on the Hau River is -2.7×106 m3. At the same time, the erosion depth deepened by approximately 0.25-0.75 m (especially up to 1.0 m). This indicates an imbalance in sediment deposition and erosion, with a consistent trend of riverbed, banks, and shore erosion.
Longshore sediment transport rate at a pocket beach in Phu Quoc City, Kien Giang Province, Vietnam
This study conducts a critical examination of the Longshore Sediment Transport Rate (LSTR) along Cua Can Beach in Phu Quoc City, Kien Giang Province. This notable pocket beach is characterized by its natural beauty and burgeoning tourist developments. The escalating construction of tourist facilities and resorts in close proximity to the shoreline, without considering beach morphological changes, poses a significant threat to the coastal integrity and sustainable development of the region. In response to this concern, our research aims to estimate the LSTR on the west coast of Phu Quoc to advocate for informed coastal engineering management and sustainable development strategies. Employing an integrated methodology that combines remote sensing with a simplistic one-line model, this study provides a comprehensive assessment of sediment dynamics along Cua Can Beach. The findings reveal consistent annual sediment transport from south to north, with an estimated quantity ranging from 5,000 to 20,000 m³ per year.
Exploring the training results of machine learning models using different batch sizes and epochs: A case study with GNSS time series data
This study applies the GRU (Gated Recurrent Unit) model when selecting different values of batch-size, namely 16, 32, and 64, with varying epochs of 20, 50, 100, 150, and 200. The input data comprises observations collected by two GNSS CORS stations from the VNGEONET network, namely HYEN and CTHO, spanning from August 10, 2019, to March 18, 2022. Initially, GNSS CORS data is processed using Gamit/Globk software to obtain the Up-component, which serves as the input data for the GRU model. The research results indicate that the statistical performance metrics of the model, such as RMSE and MAE, decrease while the F-Score increases when the batch-size decreases and the epoch value increases. In cases where the Up-component exhibits irregular variations (seasonal fluctuations), the performance of the GRU model is subpar, with an F-Score of 0 observed when batch-size values are 32 and 64 and epoch value is 20. For data following the pattern of CTHO CORS station, the GRU model performs exceptionally well when batch-size is 16 and epoch is 200. However, the forecasting performance is low for data from HYEN CORS station, indicating the need for further investigation in the future.
Exploiting the results of running the GEOS-CF model to evaluate PM2.5 concentration in near real-time in Vietnam
Near real-time information about global atmospheric composition, including PM2.5 fine dust, is valuable because it helps forecast air quality and manage environmental disasters. Recently, NASA’s Global Modeling and Assimilation Office has released a set of near real-time Goddard Earth Observing System models that help analyze and forecast global air quality, named GEOS-CF (GEOS Composition Forecast). In particular, GEOS-CF can simulate the transport from the stratosphere to the troposphere (the stratosphere to troposphere transport) which is technically very difficult. In Vietnam’s challenging conditions, research and application of GEOS-CF output results must be made. In this study, the authors developed a tool named ENAR (Envim Nasa Analysis Result) to help interpret GEOS-CF results provided free of charge by NASA to form PM2.5 pollution maps for each area hourly across the entire territory of Vietnam. ENAR was applied to build pollution maps for the first three months 2024. The results were analyzed to clarify the range of pollution levels for each area, including the Hoang Sa and Truong Sa archipelagos, Vietnam. These results allow scientific agencies to obtain reliable information for studies predicting this type of pollution.
Assessment of household adaptive capacity to disasters: Two comparative case studies in Central Vietnam
This paper presents comparative case studies between an ancient town in Quang Nam province (QN town), and a commune in Da Nang city (DN commune) in order to quantitatively assess the adaptive capacity of households in response to natural disasters. An indicator-based assessment with a set of 13 indicators is applied in this study. The results of 85 interviewed households in two study areas revealed that despite the higher probabilities of disaster occurrence, the households in QN town demonstrated better adaptive capacity compared to those in DN commune. The quantitative assessment (on a 0–1 scale) of adaptive capacity in the QN town and DN commune showed the values of 0.61 and 0.55, respectively. QN town had higher adaptive capacity than DN commune due to higher income stability, better preparedness measures for disasters, higher percentages of households receiving disaster warning information, better accessibility to clean water, healthcare service, food, and financial support during and after disasters. Conversely, DN commune demonstrated higher insurance coverage, higher percentages of households participating in social organizations, and receiving social support during and after disasters. Drawing from the findings that influence the difference in adaptive capacity levels between households in QN town and DN commune, the study subsequently proposes the recommendations for policymakers and individuals in both areas to improve their long-term prevention and preparedness strategies, enabling them to effectively respond to natural disasters.
Application GIS and remote sensing methods to assess the change in land surface temperature in Ba Ria - Vung Tau province, Vietnam
Ba Ria-Vung Tau province is situated in the Southern main economic area with rapid urbanization, industry, and modernization. The expansion of impermeable land cover has grown significantly in response to climate change and global warming, which have resulted in higher surface temperatures in the province in recent years. This study provides an assessment of the impact of increased temperature in Ba Ria - Vung Tau province based on surface temperature values extracted from thermal infrared Landsat image data during the period 2010-2021. The variety of land cover tends to influence the properties of land surface temperature reported by satellite sensing sensors. The results show that the heat island activity is strong, with a decreasing trend from urban to peri-urban areas. The surface temperatures above 30-40oC accounted for just 5% of the study area in 2010, but the rate doubled by 2021. Typical areas with an increase in surface temperature due to the rapid urbanization include Vung Tau city, Ba Ria city, Long Dien district, and Phu My town. This demonstrates that the changes in land cover is a factor contributing to the increase in land surface temperature in the area.
Estimation of the virtual water trade of agricultural products between Vietnam and China
China not only serves as a significant trading partner for agricultural products with Vietnam but also holds a strategic position as an upstream neighbor in Vietnam's major river basins, thereby influencing the nation’s water security. This research initially examines the Vietnam-China relationship through the lens of virtual water trade in agricultural goods, analyzing the period from 2010 to 2021. Findings reveal Vietnam’s status as a virtual water deficit country vis-à-vis China, a trend that has been progressively worsening. Vietnam acted as a virtual water exporter during this period, exporting around 98 billion m3 to China while importing 10.96 billion m3. Both nations share similarities in virtual water structure due to similar climatic conditions and technical advancement levels. In terms of product structure, Vietnam emerges as a strategic partner, predominantly supplying China with agricultural products derived from plants. However, this structure lacks balance and is primarily centered around a select few products such as soybean oil (constituting 20.77% of virtual water imports) and manioc starch (constituting 33.48% of virtual water exports). The virtual water trade between Vietnam and China reflects a negative net import, with both countries possessing renewable internal water freshwater resources per capita lower than the global average. While Vietnam currently supports China in addressing water scarcity challenges, diversifying export markets and optimizing the import-export framework with China can enhance Vietnam’s resilience and contribute to long-term water sustainability. Consequently, prioritizing policies aligned with the virtual water perspective will empower Vietnam to effectively manage water scarcity, ensuring its future sustainability.
Analytical methods used in microplastics identification: A review
Microplastic research plays a crucial role in identifying microplastic polymers. Scientists use different methods such as Flame tests, Differential thermal scanning, Thermogravimetric analysis, and Infrared spectroscopy to accomplish this. The objective of this study incluce: (i) Firstly, it aims to summarize recent research trends on techniques for determining polymer types in various environments. It provides an overview of each technique and compares their strengths and limitations. (ii) Secondly, it determines the types of microplastics in surface water samples in the Saigon - Dong Nai River basin, during the period 2023. The Fourier transform infrared spectroscopy (FTIR) technique is applied according to the total attenuation method (ATR-FTIR). The study shows that it is possible to quantify and classify microplastics by manual observation or through observation or microscopy. However, determining the type of polymer is almost impossible. To overcome this limitation, scientists use a combination of physical (e.g., light microscopy, magnifying microscopy), chemical (e.g., spectroscopy), and thermal analysis techniques. The study results reveal that there are more than 60 types of microplastics present in the main water supply for daily drinking and drinking purposes of the people of Ho Chi Minh City and neighboring provinces. It provides a foundation for river basin water resource managers to propose appropriate water resource management measures and programs during the process of water exploitation and use in the area.
Application of MNDWI index for flood damage area calculation in Lam river basin using google earth engine platform
Floods, as natural occurrences, often result in significant impacts on human life. The construction of flood maps plays a crucial role in devising appropriate strategies to mitigate the adverse effects of floods. In recent decades, there has been notable attention towards flood mapping methods utilizing remote sensing images. This paper introduces a methodology for generating an inundation map for rainy season and river network. To achieve this objective, we investigated the use of the recently developed Modified Normalized Difference Water Index (MNDWI) within the Google Earth Engine platform for extracting surface water. The study yielded flood maps extracted with considerable precision, facilitating the calculation and analysis of flood extents within the study area.
Evaluate the correct and the skill of the IFS model for minimum temperature, average temperature, maximum temperature forecasting in short term (24 hours) at 09 regions in Vietnam
Conceptually, forecast verification is simple, you just need to compare the forecast factors and observed factors. The accuracy of a forecast is a measure of how close to the actual weather the forecast was. The reliability of a forecast is the average agreement between the forecast values and the observed values. The skill of a forecast is performed based on some benchmark forecast, usually by comparing the accuracy of the forecast with the accuracy of the benchmark. The benchmark forecast can be a climatic value. Meanwhile, the correct forecast is bias between the forecast value and the observed value within the allowable range. This study evaluates the correct and forecasting skill of the IFS model (by European Centre for Medium-Range Weather Forecasts) for minimum temperature (Tm), average temperature (Tave), maximum temperature (Tx) forecasting in 24 hours at 09 regions in Viet Nam. The results show that within 24 hours, the IFS model predicts a high bias for the Tm (from 0.2 to 0.9oC) and a low bias for the Tave (from -0.2 to -0.9oC) and Tx (from -1.0 to -2.0oC). The correct in the southern region is higher than in the northern region (average about 10 to 15%). The skill of IFS model is higher than the benchmark (skill for the Tm has exceeded the Benchmark value by 0.4 to 0.6; skill for the Tave has exceeded the Benchmark value by 0.5 to 08), in there, the skill of Tm and Tave is higher than skill of Tx at the most regions, except in the Southern region, the skill of IFS model is lower than the benchmark for Tave and Tx.
A study on the application of computational models as support tools in urban flood management along the Cai Nai river in Can Tho city
Urbanization processes often lead to flooding issues, hindering the development of cities in Vietnam. For cities undergoing planning, initial solutions are crucial. To avoid replicating old urban structures, lacking green spaces, and missing water retention systems, this paper applies Low Impact Development (LID) solutions within the Storm Water Management Model (SWMM) framework for flood management in the new urban area along the Cai Nai River, located in the new residential area of Hung Thanh Ward, Cai Rang District, Can Tho City. The integration of SWMM with LID serves as a useful tool towards sustainable urban development, aiming for a more modern and intelligent city. This tool helps managers and investors save costs and time in selecting suitable solutions tailored to the planning characteristics of the study area, ensuring effectiveness during implementation. The paper proposes constructing two scenarios: current status and planned; comparing flow rates before and after urbanization for a major rainfall event on April 2, 2023. Subsequently, LID solutions are introduced and evaluated for effectiveness through each calculated scenario.
The trend of erosion and accretion of the western coast of the Mekong Delta, the section from Ca Mau Cape to Kien Giang
Natural processes and human-caused activities, including coastal erosion, constantly threaten coastal areas. This phenomenon is dangerous because the permanent loss of land leads to the transformation of the coast. In recent years, coastal erosion has become increasingly complicated in the Mekong Delta, especially in the western coastal area of Cape Ca Mau. This study aims to provide updated results of the changing trend of accretion/erosion of the coastline from Cape Ca Mau to Kien Giang in 2021-2023. Specifically, the rate and area of erosion/accretion considered. Remote sensing and GIS tools are used. As a result, in Ngoc Hien district, Ca Mau, the erosion rate is 55.66 m/year, and the erosion area is 47.21 hectares, ranking highest compared to other districts in the same study area. The results also show that the Kien Giang coastal area has a more moderate erosion process than the accretion process. In contrast, on the coast of the Ca Mau Cape area, the erosion and accretion process are complexly interwoven, especially in the Dat Alluvial Plains area Cape - Ngoc Hien (Ca Mau).
Risk of groundwater pollution and proposals for sustainable development in Binh Thuan province, Vietnam
Groundwater serves as one of the important sources of water supply for Binh Thuan province, Vietnam during dry seasons. This water source is concentrated in Quaternary sediments with two aquifers qh and qp. Geophysical methods have been applied, performing geological drilling, observing and monitoring boreholes. Determine the characteristics of the qh and qp aquifers, located along the coast of Binh Thuan province. Our research has shown that these reservoirs are contaminated. Water sources are at high risk of being contaminated with mineral oil, radioactive, organic, bacterial and saline contamination. The article warned about water resource risks in Binh Thuan province and proposed remedial measures to ensure water resources for Binh Thuan province.
Determine greenhouse gas emissions from landfills and suggest a household solid waste classification system in Dong Hoi, Quang Binh province
The distribution network model is one of the sophisticated strategies being used in research to assess the state of household solid waste (HSW) management and calculate the quantity of greenhouse gas emissions from landfills in Nghia Ninh and Bao Ninh communes. Traditional and modern techniques are also being used in this study. The results have assessed the existing state of household solid waste (HSW) management for home sizes ranging from four to six people. The daily average for garbage per person is 0.31 kilogram. The corresponding CO2 emissions from the two communes are 0.42 kg/person/day (Bao Ninh) and 0.47 kg/person/day (Nghia Ninh); study and survey data from these two districts show that the average cost for households to collect HSW is 27,000 VND/family/month. 2698.72 kg CO2 equivalent per ton of garbage, the same amount of emissions from solid waste. Nghia Ninh and Bao Ninh communes, as well as the Dong Hoi city government in general, rely on it to limit the amount of waste that families emit into the environment while encouraging improved information exchange and sharing. Share responsibility for waste management and encourage waste separation at the source.
Evaluation of the Can Gio Vegetation Index changes using the Sentinel-2 Datasets from 2015 to 2023
Can Gio Mangrove Biosphere Reserve provide many ecosystem services, such as provisioning, regulating, cultural, and supporting services for the urban areas as well as wildlife of suburban areas in Ho Chi Minh City and the nearby ecosystems. Therefore, it is important to monitor and evaluate the changing of mangrove forest cover in the long term. In this study, the Normalized Difference Vegetation Index - NDVI at 10 m resolution from 2015 to 2023 of Can Gio was obtained from the Copernicus Sentinel-2 database using Google Earth Engine - GEE. Subsequently, NDVIs statistic were computed by R to assess the slope of NDVI changing with p-value significance in Can Gio. The results indicated that NDVI values typically range from -0.4 to +0.8 and vary annually. It is evident that NDVIs values from 2015 to 2020 are marginally higher than those recorded between 2021 and 2023. The degradation in average NDVI from 2015 to 2023 was rationally deducible either from the downsizing of mangrove forest areas or the degradation of the mangrove forest. However, the annual NDVI statistic revealed there were areas with an acceleration of NDVI in comparison with the destruction of NDVI areas from 2015 to 2023. Linear regression effectively models continuous processes like deposition or erosion. However, to evaluate other factors such as discrete human-made or sporadic impacts, alternative statistical models should be considered
Experimental optimization to enhance oil removal efficiency from water using carbonized rambutan peel
In this study, the objective was to employ experimental design in order to optimize the efficiency of diesel oil removal from water using activated carbon sourced from rambutan peel. A central composite design was utilized to investigate the impact of contact time, adsorbent dosage, initial oil concentration, and pH on both the removal efficiency and oil adsorption capacity across 30 different experimental designs. The analysis of activated carbon properties derived from rambutan peel revealed a BET surface area of 786.014 m2/g, a BJH adsorption cumulative pore volume of 0.054 cm3/g, and an average BJH adsorption pore diameter of 55.243 nm. The quadratic model was employed to estimate the mathematical relationship between the removal efficiency and adsorption capacity of diesel oil in relation to the four key independent variables. The ANOVA analysis demonstrates F-values of 12.36 and 39.92 for the respective models, both exhibiting ρ-values < 0.05. The predicted values closely align with experimental results, showcasing R2 values of 92.02% for removal efficiency and 97.39% for adsorption capacity. The investigation anticipates that, based on the analysis of 87 solutions, optimal conditions of 70.60 minutes of contact time, 0.25 g/g adsorbent dosage, 0.97% v/v initial oil concentration, and a pH of 6.20 will yield a maximum removal efficiency of 72.12% and a maximum adsorption capacity of 5.3570 g/g. This combination of factors achieves a desirability rating of 0.741.
Characteristics of seawater intrusion in Soc Trang province, Vietnam
Seawater intrusion poses many severe issues in many coastal areas around the world, including the Mekong Delta, Vietnam. For sustainable water management in such regions requires, it is crucial to understand the characteristics of salinization. This study aims to investigate the characteristics of the salinization phenomenon in water systems and its controlling factors based on hydrogeochemical analysis, seawater-freshwater mixing model and End Members Mixing Analysis. The results revealed that seawater intrusion negatively affects strongly on surface water quality with different magnitudes, depending on seasonal variation and tidal regime. It was estimated that surface water mixed with approximately 29.5% and 4.12% of seawater in the dry season and rainy season, respectively. However, it was found that the salinity in groundwater showed less seasonal variation and was distributed heterogeneously following the depth of screened wells and distance to the sea. The mixing ratio between seawater and groundwater varied widely, ranging from less than 10% in deep groundwater up to a maximum of 38% in shallow groundwater. Surface water salinization in the study area is controlled by upstream discharge, tidal regime, and operation of sluice gates. Meanwhile, groundwater salinization might be governed by geological characteristics, original recharge sources, human intervention, and natural variation, especially excessive groundwater exploitation in the Mekong Delta. Therefore, integrated sustainable groundwater and surface water use and management strategies in the Mekong Delta are needed in the context of human-nature intervention.
Application of EnHEBIS tool to assess economic impact due to health effects from PM2.5 pollution – A case study at Long An province, Vietnam
Assessment of the effects of short-term PM2.5 exposure on human health is one of the problems that need to be addressed within the framework of sustainable development. The goal of this study is to quantify the health-economic impacts of PM2.5 pollution for a specific province - Long An province in Vietnam using the EnHEBIS (Environment, Public Health, and Economic Benefit Management Support Integrated System) software package. The study outcomes showed that significant health and economic effects could occur in areas with high PM2.5 concentrations and dense population concentrations. Prominent results presented that acute exposure to PM2.5 pollution from May to December 2018 caused 265 (95% CI: -12; 422) premature deaths, which approximately 60% of all early deaths due to all-caused respiratory diseases (RDs) with 155 (95% CI: 23; 170) cases. Corresponding to the health impacts, the economic values of Long An province also suffered a loss of around 1.15% of the total value of the gross regional product (GRDP) with about 1,270 (95% CI: -57; 2,021) billion VND, equivalent to roughly 170 million USD, along with a significant decline in the working time for the adult group. Although uncertainties have remained in this study, these results have shown the extent of economic, health, and environmental damage when PM2.5 pollution occurs. The highlights are the basis for proposing measures to control and improve the local ambient air quality.
Assessing the level of air pollution at some small-scale household waste incinerators in Hai Hau district, Nam Dinh province
In this study, sixteen air samples from two small-scale household waste incinerators in Hai Hau district, Nam Dinh province, Vietnam, were collected and investigated for some pollutants such as SO2, NO2, CO, H2S, and BTEX. The results showed that the concentration of SO2, NO2, CO, and H2S were correspondingly in the range of 351.1 -450.0, 30300-36600, 200.7-212.0, and 78.9-100.1 µg/m3. In addition, the BETX concentration ranged from 5.16 to 20.7 µg/m3 for Benzen, from 21.63 to 120.66 µg/m3 for Toluen, from 3.13 to 12.57 µg/m3 for (m, p)-Xylene, and from 1.58 to 7.73 µg/m3 for o-xylene. All the values of SO2, NO2, CO, and H2S concentration were higher than standard concentrations in QCVN 05: 2013/BTNMT, however, the BETX concentration was lower than the standards in QCVN 06:2009/BTNMT.
Assessment of the influence of urban flood in Thu Duc City in the period of planning
Ho Chi Minh City is a low-elevation coastal city with and rapidly increasing population. Thu Duc, the city in Ho Chi Minh City, is the first city in Vietnam that belongs to the type of city administrative unit directly under the central city. This area is greatly affected by flooding, classified into three groups: heavy precipitation, tidal current, and combined tidal current and heavy precipitation. In this study, the flooding situation caused by the groups in the planning period (from 2010 to 2020) will be assessed and mapped by using GIS. The results show that, in the period from 2016 to 2021, flooding by heavy precipitation was more serious than that by tidal current. Compared to the drainage planning map in District 2, District 9, and Thu Duc District by 2020, some flooded locations due to no drainage system, lack of drainage systems, and unresponsive drainage systems have not yet been planned. In District 2 and District 9, some locations experienced flooding attributed to heavy precipitation, yet there is currently no drainage plan in place until 2020. In Thu Duc district, the majority of flooding incidents caused by precipitation can be attributed to the degradation of the existing drainage system, compounded by the absence of a sewer system. Furthermore, there were more points of re-flooding and more severe flooding compared to the same time in the previous period. This research is the scientific basis for flood
Evaluation of the effects of surfactants in the water of Kim Nguu River, Hanoi
Surfactants are one of the new pollutants of current concern worldwide. Many studies show the toxicity of surfactants to human health and microorganisms. Kim Nguu River is one of Hanoi’s wastewater drainage rivers, and the number of residents in the river area is quite dense. In addition, around the river area, there are many hospitals, factories, and industrial parks in operation. Especially the 8/3 textile factory where a lot of detergents are produced due to the bleaching and dyeing processes in the river. In this study, the author conducted sampling and analyzed the concentration of pollutants in the Kim Nguu River according to the method of Kadokami. This is a comprehensive analysis method that is both qualitative and quantitative According to analysis, there are currently two substances belonging to the group of surfactants: Nonylphenol and 4-tert-Octyphenol with concentrations measured in 2018 and 2019 of 4.1-12.45 μg/L, 11.4 to 29.56 μg/ L and 2.02-3.21 μg/L and 3.95-6.7 μg/L. The concentration of surfactants in the Kim Nguu River tends to increase sharply over time, and the level of impact of the concentration of surfactants in the Kim Nguu River on the ecosystem is at a high level. Kim Ngu River is just one of Hanoi’s wastewater drainage rivers. Further research is needed on other wastewater drainage rivers to have clearer conclusions about the appearance of surfactants. in rivers draining wastewater.
Assessment of heavy metal pollution and ecological risk in the sediment of Cua Luc Bay, Quang Ninh Province
Heavy metals have big impacts on environmental quality and ecological risk. In this research, the Igeo accumulation index and ecological risk index (ERI) were used to assess the heavy metal pollution and ecological risk in the sediment of Cua Luc Bay, Quang Ninh Province. The results indicated that heavy metal concentrations in the study were almost lower than QCVN 43:2017/BTNMT. Only 3 monitored points, S1 (172.87 mg/kg), S3 (147.12 mg/kg), and S4 (115.54 mg/kg), have a light pollution level of Cu (108 mg/kg). The Igeo heavy metal accumulation index indicates that As (1.85), Cu (2.34), and Sb (1.42) are at a moderate level. While Se (3.65), Ag (3.58), and Sn (3.09) are at a high heavy metal level. As and Cu are two major factors posing ecological risk in the region (66.5%). However, the average ERI of all monitored points is 138, indicating that the ecological risk for heavy metals in the region is low. Despite having a low ecological risk for heavy metals in the region, it is necessary to strictly monitor
Landslide susceptibility mapping based on the Weights of Evidence model for mountainous areas of Quang Nam province, Vietnam
This study shows the results of landslide susceptibility mapping for the southwest region of Quang Nam province using the Weights of Evidence (WoE) model. The input data consists of a landslide inventory and ten influencing factors, i.e., geology, distance to fault, elevation, relief amplitude, slope, aspect, rainfall, soil type, land use, and distance to road. The landslide inventory was constructed from three principal sources: fieldwork survey, legacy data from previous studies, and additional analytical data from high-resolution Google Earth satellite imagery. The landslide locations were randomly categorized into two parts in the ratio 70/30: 70% (811 landslides) for modeling and 30% (348 landslides) for verification. All input data are normalized and constructed into the GIS landslide database. The results of the multicollinearity test show that no collinearity existed between ten input variables. The computation of the weights for classes of influencing factors from 70% of the landslide data using the WoE model has allowed the establishment of the landslide susceptibility map. The model performance was evaluated by using the receiver operating characteristic (ROC) analysis. The area under the curve (AUC) was computed for the success rate curve (using 70% landslide data) and the prediction rate curve (using 30% landslide data) at 0.855 and 0.844, respectively. Thus, it can be confirmed that the landslide susceptibility mapping based on the WoE model was very reliable in the study area.
Development of an ensemble dynamic-probabilistic prediction model for tropical storm genesis in the Vietnam East Sea using the Logistic Regression approach
In this study, a logistic regression model is developed to forecast tropical storm (TS) genesis in the Vietnam East Sea from 2012 to 2019. The model incorporates seven potential predictors including dynamic and thermodynamic parameters at formation time retrieved from the WRF-LETKF outputs. After rigorous testing, six predictors are selected, excluding minimum sea-level pressure. In a broader context, the logistic regression model performs promisingly, generating forecast probabilities that enhance the accuracy of TS genesis predictions, particularly in early forecast cycles. The model’s regression coefficients and forecast outcomes align well with test dataset results, affirming its stability and validity. As a result, the forecast probability from this model can be effectively employed as a probabilistic forecast value for predicting TS genesis status.
Efficient oil removal from water using carbonized rambutan peel: Isotherm and kinetic studies
The study aims to assess the diesel oil adsorption capacity of activated carbon derived from rambutan peel, a prevalent agricultural by-product in Vietnam. The adsorption process will be investigated using various adsorption isotherms (Langmuir, Freundlich, Temkin, Dubin-Radushkevich), adsorption kinetics (pseudo-first order and pseudo-second order). The characterization analysis of RPAC revealed the following values: BET surface area of 786.0143 m2/g, BJH adsorption cumulative volume of pores at 0.05392 cm3/g, and BJH adsorption average pore diameter of 55.2432 nm. Individual assessments of factors influencing oil removal efficiency and adsorption capacity identified the optimal initial oil concentration at 1% volume/volume, an optimum contact time of 60 minutes, and an equilibrium adsorption time of 80 minutes. The optimal adsorbent dosage was 250 mg, and the ideal pH was 6. The adsorption process adhered to the Langmuir isotherm with an R² value of 0.9993, yielding a maximum adsorption capacity of 5,712.0 mg/g. The pseudo-second-order model provided a better fit for RPAC’s oil adsorption process with an R² value of 0.9969.
Assessment of current water quality status in clam areas in Thai Binh Province and proposal for measures to improve efficiency
This paper presents the results of water quality assessment of clam farming areas for 3 monitoring points in Tien Hai district, Thai Binh province. Using monitoring parameters including: Temperature, pH, Salinity, Alkalinity, N-NO2-, N-NH4+, H2S, Coliform, Total Vibrio to assess water quality in clam culture area by using methods: The method of calculating the pollutant load due to domestic wastewater, the method of assessing the current state of the water environment based on national standards and the assessment method according to the water quality index (WQI). The results show that the monitoring points in the clam farming area of Thai Binh province: Temperature, pH and H2S- in the water are within the limits according to QCVN 10:2023/BTNMT; QCVN 02-19:2014/BNNPTNT and QCVN QCVN 08:2023/BTNMT. Salinity and alkalinity fluctuate greatly, the proportion of samples outside the permissible limits is 54.17% and 12.5%, respectively. N-NH4+, N-NO2-, have a high percentage of samples with values exceeding the permissible limit, ranging from 41.65 to 62.50% of the monitored samples. Coliform exceeded the limit from 2 to 256 times. The total Vibrio density was 20.83% of samples above the limit. The average water quality indicator on 3 monitoring locations has a percentage rating of Excellent: 20.83%, Good: 12.5%, Medium 12.5%, Bad: 37.5% and very bad: 16.67%. From the results of the assessment, this study suggests management measures, including improving water quality index used to zoning water quality, thus better managing clam areas; and technical measure which improves farming techniques to protect the aquatic environment of farmers.
Residual and ecological risk assessment of Chlorpyrifos in coffee growing soil areas: A case study in Lam Ha district, Lam Dong province
This study was conducted to investigate the residual of Chlorpyrifos (CPF) in coffee growing soil at Lam Ha district, Lam Dong province. Fifteen soil samples were collected from coffee intensive gardens in the Phi To, Nam Ha, Me Linh and Dong Thanh communes of Lam Ha district during the February 2023. The physico-chemical properties of the samples were analyzed such as pH, organic carbon, moisture content and mechanical composition of the soil while CPF was analyzed by gas chromatography-mass spectrometry. Soil samples with pH ranged from 3.48-4.45, moisture content 28.2-33.8% and OC 2.3-3.4%. Chlorpyrifos concentration of soil samples ranged from not detected to 954 µg/kg. The ecological risk of chlorpyrifos residual in soil was evaluated by using the risk quotient (RQ). The results of this study will be used to propose solutions to reduce pollution.
Application of 2D hydro-dynamic model to simulate the suspended sediment on the Tien river, Cao Lanh district, Dong Thap province
This study was carried out to analyze and evaluate the change in the amount of suspended sediment on the Tien River in the Mekong Delta. Evaluating the sediment transport regime is a very important task to effectively serve the assessment of the level of evolution (erosion/accumulation) on the riverbed. This study applied the Mike 21FM hydrodynamic model to simulate the sediment transport regime on the section flowing through Cao Lanh district, Dong Thap province - where the erosion process is very complicated recently. The simulation results show that the largest number of displaced sediments appears on the right bank, the maximum amount of sludge transported ranges from 0.91 kg/m3 to 2.7 kg/m3. During the simulation period, the total amount of sediment that has moved downstream is about -218.7×106 m3, the depth is -233 cm, the average rate of erosion is -77.6 cm/year, where the deepest erosion can be up to -10.0 m.
Flood risk assessment from high tide based on principal component analysis (PCA) of Sentinel-1 satellite images sequence for Ho Chi Minh City
Using Sentinel-1 image series with 10m resolution from the past to present by Principal Component Analysis (PCA) method for Ho Chi Minh City area, helping to assess flood risk due to canal leveling, slitting in some complicated times, narrows the space for water regulation. In addition, Climate change causes sea level rise, thereby increasing the existing water level along with that in large rivers and also causing storm surge, which coincides with the time of flood discharge at Dau Tieng and Tri An reservoirs. The situation of groundwater exploitation, subsidence of the existing ground is continuous and increasing. With the accumulated settlement estimated to date about 100 cm, the current settlement rate is about 2-5 cm per year. Particularly in concentrated areas such as commercial works, the subsidence rate is about 7-8 cm per year. The rate of land subsidence is about twice as high as sea level rise. Therefore, Ho Chi Minh City is one of the cities affected by flooding due to high tide, especially in the current climate change conditions. According to the statistics of flood-prone areas due to high tides from 2014 to 2022, Can Gio district has the highest risk of flooding, with a flooded area of up to 3.713.236 hectares. The districts with an extremely high risk of flooding after Can Gio district are Cu Chi district, Binh Chanh district, and Nha Be district, with 1,764,564 ha, and 1,296,246 ha, and 1,012,550 hectares.
Evaluation of the current status of wastewater management and treatment from super-intensive whiteleg (Penaeus vannamei) shrimp ponds in Ben Tre Province
Ben Tre province in Viet Nam must contend with the fact that the farming environment is deteriorating beccause of poor disease management practices, pond wastewater discharge, and bottom muck. The current state of extremely intense shrimp farming in Ben Tre province is depicted in this study. In addition, this study also evaluates the state of Ben Tre province's wastewater treatment and super-intensive shrimp farming practices. Shrimp pond wastewater is often held in settling ponds in super-intensive shrimp farming households in three districts of Binh Dai, Ba Tri, and Thanh Phu of Ben Tre province, however, some households will continue to discharge wastewater through treatment ponds. According to the analysis’s findings, treated shrimp ponds have considerably superior water quality than untreated shrimp ponds. However, the concentration of COD, BOD5, H2S, and NH3 in treated ponds remained higher than the standard of QCVN 02-19:2014/BNNPTNT, although having dropped in comparison to untreated ponds. As a result of the aforementioned fact, it is imperative to conduct research and develop an environmentally friendly and highly effective wastewater treatment process to conserve and circulate water for extremely intensive shrimp ponds in the Ben Tre Province area.