Science & Technology Development Journal - Science of The Earth & Environment

Chronic effects of domestic and single used plastic leachates on the microcrustacea Daphnia magna

Van-Tai Nguyen — 2021-08-06

Plastic pollution has become one of the most serious environmental issues worldwide. Plastics can contain high amount of additives (e.g., phthalate, bisphenol A, trace metals), and they could be leached out of plastics, enter the aquatic environment and cause toxic effects to aquatic organisms (including microcrustacean). In this study, we investigated chronic effects of plastic leachates from two popular plastic materials (garbage bag and disposable raincoat) on the survival, maturation and reproduction of the microcrustcean Daphnia magna. The results showed that, the plastic leachates from the two materials at the concentration up to 1000 mg/l did not cause negative effect on survival of D. magna. However, exposed to the leachates from the garbage bag (at the concentrations of 10, 100 and 1000 mg/l) and from the disposable raincoat (at the concentration of 10 mg/l), the animals delayed their maturity ages compared to the control. Besides, the two kinds of leachates at the concentration of 1000 mg/l stimulated the reproduction of D. magna, resulting the increase of 17 – 37% of total offspring compared to the control, during 21 days of experiment. The results of this study contribute to the understanding on the toxicity of popular plastic materials to the microcrustacean, D. magna. Additionally, the plastic usage and emission into the environment should be paid more attention to protect the aquatic ecosystems and human health.

Correlation between soil moisture content and reflection value of VV polarization, VH polarization of Sentinel-1 satellite: Study case of dragon fruit farm, Binh Thuan province

Trang Nguyen Dang Khoa — 2021-08-15

Binh Thuan province is one of the driest provinces in the South Central region in particular and Vietnam in general. The scarcity of water for agriculture in this area in the dry season is very serious. Surface moisture is one of the parameters included in the assessment of aridity. In this study, the authors establish the correlation between VV reflectance value, VH reflectance value extracted from Sentinel-1 satellite image and surface soil moisture collected in the study area. Moisture samples in the field will be taken at a depth of 5cm from the surface in at the same time the Sentinel-1 observation through study area. Samples were taken at 4 different days, each day taking 22 samples and 2 samples for calibrated. Reflectance value VV, reflectance value VH at different times are adjusted according to 2 fixed points corresponding to the place where water is saturated and the surface is the driest in the cultivation area of dragon fruit. Besides, the soil moisture value correlated with the reflectance value of VV and reflectance value of VH in research was compared and compared with similar studies in the world in order to increase the reliability of the data. The results of analysis of moisture samples in the field with humidity values ranging from 13.13% to 61.06%, are correlated with the reflectance value of Sentinel-1 image with R2= 0.926 of VV polarization and R2= 0.956 with VH polarization.

Optimizing Electro-Fenton process for removal of atrazine from aqueous solutions using Taguchi method

Loan Huynh Ngoc — 2021-08-18

The purpose of this study is centered on the removal of atrazine, one of the popular organochlorines in Vietnam, from an aqueous solution, using an electro Fenton process with iron and carbon plated steel electrodes at a batch electro reactor. This study had applied the Taguchi method, one of the most uncomplicated cases of design of experiments involving the minimum number of experiments to be performed within the permissible limit of factors and levels through the Signal to Noise ratio. This study design was conducted with five independent factors: initial pH, current density, Fe²⁺ concentration, sodium sulfate and reaction time, at a fixed atrazine concentration of 10 mg/L to find the best condition to eliminate atrazine from the solution. The Signal to Noise ratio results illustrates that the initial pH is the most important factor, followed by the reaction time and Fe²⁺ concentration, while sodium sulfate and current density seem neglectable to the removal of atrazine using electro Fenton process. The optimal Taguchi condition shows that the electro Fenton process reached the best efficiency, approximately 76% atrazine eliminated after 180 min of reaction time at initial pH 3.5, sodium sulfate of 990 mg/L, Fe²⁺ concentration of 2 mM and current density of 2.22 mA/cm². Three confirm experiments at optimal test conditions also indicated good agreement with predicted results with small error variation (1.21 - 3.54%). Thus, the relationship between the removal efficiency and operating parameters could be understood. These obtained results highlight the potential of using the electro Fenton process to eradicate or reduce pesticide contaminants. Electron beam also could be one of the pre-treatment techniques to eliminate persistent organic pollutants before biological treatment systems.

Study of the treatment of leachate after biodigestion using Electro-fenton method

Pham Kieu Tuyet Tran — 2021-08-23

Leachate contains many non-biodegradable organic compounds and nutrients with high concentrations, especially from urban waste landfills with long operating times (> 10 years), which affects the human health and environmental quality. Electro-Fenton is one of the advanced oxidation processes (AOPs) that has been recently studied for the treatment of many persistent organic compounds in water. In this study, post-biological leachate (continuous flow biological tank) was treated using Electro-Fenton method with heterogeneous catalysts as Iron (II) Sulfide and Iron Oxide on two electrodes Ti/IrO₂-Ta₂O₅ and Ti/RuO₂. The effect of different pH conditions on the pollutant removal efficiency in landfill leachate was studied. The results show that Ti/IrO2-Ta2O5 electrode and Iron (II) Sulfide catalyst obtain better leachate treatment performance than the others under the same experimental conditions. The heterogeneous Electro-Fenton process was capable of removing 71% of chemical oxygen demand (COD), 88% of total organic carbon (TOC), 89% of total nitrogen (TN), 93% of ammonium nitrogen N-NH4 + and 99% color at Ti/IrO₂-Ta₂O₅ electrode and Iron (II) Sulfide catalyst at a pH 3, current density 333 mA/cm² after 90 minutes of electrolysis. The results showed that the Electro-Fenton method capable effective treatment of pollutants in the post-biological leachate in the future.

Nutrients recovery from urine through struvite formation using lab-scale fluidized-bed homogeneous crystallization reactor

Dang Bich Phuong — 2021-09-24

Phosphorus (P) is considered the most important micro-element needed for every living thing. Even though they have limited amount, P and nitrogen (N) are responsible for eutrophication in water bodies. This paper aimed to give an insight into the removal efficiency of nutrients and struvite crystallization of slowly soluble fertilizer MgNH4PO4.6H2O, which is also called NH4+-struvite. Besides, using fluidized bed homogeneous crystallization (FBHC) system can reduce impurities in granular struvite generated during the reaction as the advantage function itself. The results showed the changes in pH, magnesium (Mg2+), phosphate (PO43--P), ammonium (NH4+-N), and appearance of spontaneous struvite precipitation over time. Using synthesis urine sample with adjusted pH and Mg2+ concentration to determine the optimal conditions for granular NH4+-struvite recovery to maintain Mg and P removal efficiency up to 99% in steady state. In this study, the removal efficiency of N was about 80 – 85% maximum. The initial results indicated the feasibility of simultaneous crystallizing NH4+-struvite which is mentioned above. It could easily form at pH around 8 – 9. On the other hand, urea hydrolysis makes a pH increase in urine from 6.5 to less than 9.0 at room temperature. This might cause a heavy impact on the NH4+-N crystallization during the formation of granular struvite if there has no suitable NH4+-N pretreatment options. For Mg recovery, the concentration of Mg is detrimental in the creation of struvite. This will bring better removal efficiency if there is an available Mg source in nature which can be reused directly in an environmentally eco-friendly way. The total mass of struvite precipitate obtained in the form of nuclei corresponds to 200 g/m3 of urine during 24 days operation.

Site nutrient suitability mapping for potential Pepper cultivation with the application of spatial fuzzy multi‑criteria decision analysis and GIS

Truc Thanh Nguyen — 2021-11-07

Increasing demand of agricultural production will occur in the next decades but the available nutrients such as nitrogen, phosphorus and potassium (NPK) are major limiting factors since they are non-renewable. Sustainable cultivation methods require optimal use of resources while achieving high yields at the same time. Crop production planning must therefore take into account the different regional availability and spatial distribution of these nutrients. It also considers the nutritional needs of plants at each stage of their growth. However, high precision predictions in agricultural planning are not feasible because of uncertainties in data and the complexity of the processes, farmers tend to apply chemical fertilizer based on experience. Decision support systems based on fuzzy methods are therefore a convenient approach to deal with uncertainties in crop planning and resources management. In this paper, maps for the yield potential of pepper are generated in dependence on growth stage specific demands for nutrients. The maps are developed based on the combination of multicriteria analysis and Fuzzy Logic algorithm and GIS method for visualization. GIS soil nutrients data were used as the inputs into the system. The resulting maps constitute a sound basis for regional and site specific production planning of pepper.

Electron beam induced degradation of atrazine in solution using Taguchi approach

Tan Van Luu — 2021-11-07

This study investigated the removal of atrazine from an aqueous solution upon electron beam irradiation from an electron accelerator. Electron beam irradiation could be considered an advanced oxidation process (AOP); these techniques have been recently applied to remove a lot of contaminants in wastewater streams. Atrazine concentrations in aqueous solutions ranging from 2 mg/L to 6 mg/L were eliminated using electron beam irradiation (2-6 kGy) at pH levels ranging from 5 to 9. The coupled electron beam and hydrogen peroxide (from 1 to 5 mM) were also investigated. This study was conducted by the Taguchi method with four variables: initial pH, atrazine concentration, H2O2 dosage, and absorbed dose to mitigate atrazine in solutions. The Taguchi process was evaluated using a Signal to Noise (S/N) ratio to find the optimal condition with the simplest design. The obtained results indicate that the absorbed dose is the most important factor, followed by the atrazine concentration and initial pH, while H2O2 seems negligible to the removal efficiency. The optimal Taguchi condition shows that the electron beam process reached the best efficiency. The best predicted atrazine eradiation was obtained 100.1% at initial pH₅, H₂O₂ of 3 mM, atrazine concentration of 2 mg/L and absorbed dose of 6 kGy. Two confirmed experiments at optimal test conditions also performed 99.5% atrazine removal and were well fit with predicted results. Moreover, the operation cost at the optimal condition was determined approximately 3.032 $/m³, which was much cheaper than conventional treatment techniques. These obtained results highlight the potential of using the electron beam process to degrade atrazine contaminants.

Orientation the agricultural land under the climate change condition in Ea Sup district, Dak Lak province

Quyen Thi Ngoc Nguyen — 2021-11-30

Land suitability assessment play an important role in agricultural land use planning. The aim of the study was to assess the natural adaptation of land to orient agricultural land use in 2030 in Ea Sup district, Dak Lak province. By integrating the result of drought zoning with the natural land assessment process according to FAO (1976) in the environment of open source software QGIS, the study has built Land Mapping Units and compared to land use requirements of 8 main land-use types for classification of adaptation following 4 levels: very Highly Suitable (S1); Moderately Suitable (S2); Marginally Suitable (S3) and Not suitable (N). As a result, the proposed map in 2020 and the orientation map in 2030 about land use disposition has been built on the basis of climate change scenarios. Accordingly, by 2030, the difference in the number of drought months among the three climate change scenarios will change the area of annual crop which depend on rainwater in cultivation. The general trend showed that the area of sweet potatoes will be reduced, the area of cotton, green beans, corn will be increased. Meanwhile, rubber tree tends to replace cashew because of inefficient productivity. The study is expected to be a reference document for the restructuring of the agricultural sector in the study area.

Assessing of topographic changes in the Fairy Stream, Phan Thiet by 3D topographic mapping method

Quan Minh Chung — 2021-12-14

Currently, the Fairy Stream is a breathtaking tourist destination for domestic and foreign tourists due to the natural unspoiled beauty of the area. However, this landscape is vulnerable to human impacts such as littering, carving words on sand walls, climbing on sand walls causing slips and falls. Therefore, the requirements for management and monitoring of topographic changes are essential to preserving the beauty of this place. Unmanned aerial vehicle (UAV) technology is being widely applied in the world with much researches on applications in the fields of agriculture, mining, construction, etc. Thanks to the development of the "Structure from Motion" (SfM) method to generate a digital surface model (DSM) from UAV images and orthomosaic, which helps to accurately and quickly assess the topographic changes of the area. The author uses UAVs in landscape assessment, researches topographic changes in the Fairy Stream, Binh Thuan tourist, and 3D models at three different times about every 4 months. DEM of Difference (DoD) method is applied to analyze the change in elevation of the area and the Digital Shoreline Analysis System (DSAS) method to calculate the accretion and erosion interval over time. Flow velocity and material composition analysis demonstrate that the flow velocity exceeds the maximum erosion resistance velocities of fine and medium grain materials. Calculation by DSAS shows that erosion rate is 1.95m/8 months and accretion rate is 1.33m/8 months. After assessing, the author concludes that the fluctuation mechanism of the Fairy Stream is affected by the Northeast and Southwest monsoons, combined with the tourist factor. The study has demonstrated the potential of using UAVs in terrain change assessment to supports authorities in decision-making, provide better management measures such as zoning sensitive areas, placing signs, restricting visitors, etc.

Research on environmental risk assessment in coastal areas: Overview of methodology

CUONG TAN LE — 2021-11-07

Coastal areas always contain numerous environmental risks due to the effects of climate change and the development process. To estimate the level of risk for the environment for each coastal area to implement solutions reducing risks and pressure for sustainable development is being increasingly concerned by researchers. This study performs an overview of the papers that have been published in reputable journals related to risk assessment in the coastal environment and has found that there are 1,720 studies related to coastal environmental risk assessment in the period 2010 - 2020, of which 61 studies assess risks in the coastal environment based on composition factors: hazard, exposure, sensitivity, and adaptability. The study also analyzes and synthesizes commonly key variables and methods used to determine the component factors and framework of coastal environmental risk evaluation. The results of this study may strongly support further studies related to risk assessment in the coastal environment resulted from negative impacts and may contribute to sustainable development in coastal regions in Vietnam in the future.