Tạp chí Khoa học Trái Đất và Môi trường Đại học Quốc gia Thành phố Hồ Chí Minh

Currently, Vietnam has 80% unsanitary landfills, so it is very necessary and urgent to renovate, treat and restore the environment at these landfills after they are closed. However, at present, most of the unsanitary landfills do not have statistics on the amount of solid waste discharged, as well as data on monitoring the environmental status - This is necessary information for managers to come up with feasible options for environmental treatment and restoration at landfills. This paper presents a case study at Suoi Rao unsanitary landfill in Chau Duc district, Ba Ria - Vung Tau province with the following objectives: Determine the amount of solid waste to be buried; Evaluation of composition and characteristics of solid waste at the landfill, the research results show that: there are 6,387 tons of solid waste buried at Suoi Rao landfill, 12 times lower than the forecast of the Department of Natural Resources and Environment (76,295 tons); Most of the waste has been decomposed with easily biodegradable organic components accounting for 1.85% and non-biodegradable components accounting for 27.28%, the rest after classification (soil, sand, humus) accounts for 69%; The content of heavy metals in the soil of solid wastes buried at Suoi Rao landfill are all within the permissible standards, therefore, the impact of heavy metal content in the soil of Suoi Rao landfill to the surrounding environment is low. The research results have important implications for management levels in Chau Duc district to come up with feasible plans in line with reality to treat, renovate and restore the environment of Suoi Rao landfill in the future.

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.

Plastic debris was separated from Saigon river sediment using a microplastic sediment separator (MPSS) for the first time. A separation fluid of ZnCl2 solution (1.6 kg/L) was used to separate lower density materials (floating on the top) from higher density materials (sinking in the bottom). Plastic and plastic-like materials were collected and analyzed by a FTIR spectrometer to determine plastic composition. The results show that a total of 350 items (0.0485 g) of plastic debris were extracted from 1,500.00 g dry sediment, including 11 items (0.0130 g) of macroplastics (> 5 mm) and 339 items (0.0355 g) of microplastics (0.3–5 mm). Polyethylene (PE), polypropylene (PP), and PE-PP mixture were the most major plastic types with 225, 85, and 21 items, respectively. Others, including polystyrene (PS), polyurethane (PU), silicon, rubber, and nylon were also found in the sediment sample. Fragments were the major shape with 300 items while other shapes of sheets, fibers and beads were also recorded. The advantages of MPSS are high capacity, high separation efficiency, and low-cost operation. The disadvantages of this apparatus are high pollution due to using ZnCl2, bottom stirrer is easily stuck, and uncertain efficiency with small microplastic particles (< 0.3 mm). A significant high number of microplastics in sediment environment indicates that microplastics could be a potential risk for benthic organisms and aquatic food web. Various types and shapes of plastics also suggests that macroplastics and microplastics in sediment could originate from various sources. It is said that, for the first time in Vietnam, plastic debris, particular with microplastics, can be efficiently extracted from a large amount of sediment sample (up to 1.5 kg dry sediment). These findings could be an interesting reference for researchers who may want to obtain a large amount of microplastics for further investigation of microplastic toxicology.

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.

This paper assesses the risk of acidification of the organic shrimp model certified by Naturland at Tam Giang commune, Nam Can district, Camau province. Pond water and sediment was sampled in 8 ponds in March, July and November 2015, dike soil and mangrove soils were sampled in March 2015. Pond sediment and mangrove soils are highly reduced (Eh of top sediment and soils to 60 cm depth range respectively from -299 – -1mV and -321 – -52mV). Pond water ranges from neutral to slightly alkaline (pH of pond water 7.01-8.82) and sediment from slightly acidic to slightly alkaline (pH of fresh sediment 6.05-7.64, pHH2O 6.63-7.78, pHKCl 6.35-7.43). Mangrove soils show a large pH range with very low minimums (pHH2O 3.72, pHKCl 3.05), reconfirming the presence of pyrite mineral in the soil profile. Mangrove soils deposited on the dikes (partly oxidized) are very acidic (pHH2O 2.51±0.72, pHKCl 1.81-2.14, exchange acidity 11.56±2.69 meq/100g). At the start of the wet season, pH of pond water reduces sharply as a result of reception of acidic components from the oxidized pyritic material (FeS2) on the dikes. The exchange acidity in pond sediment and mangrove soils are negatively correlated with organic matter, indicating that the decomposition of organic matter under reduced conditions contributes to exchange acidity in pond environment. Risk of acidification of the organic shrimp model is high due to managerial activities (mostly channel digging and disposal of pyrite-containing mangrove soils on the dikes).

The process of developing industrial parks (IPs) is facing many challenges in terms of environmental pollution due to various types of waste, wastewater and especially greenhouse gas emissions. To evaluate the impacts of greenhouse gas emissions from industrial park development, this requires an effective tool to identify, analyze and assess carbon emissions from industrial zones is needed. The low cacbon industrial park index ((I¬LCIP) is the general measure to reflect the activities of the industrial park in the ways to conform with the purpose of the low cacbon economy, the national strategy on climate change and green growth. This paper chooses the Min – Max normalization method to standardize the collected data on the range of common values from 1 to 100. Based on the I¬LCIP assessment index applied to industrial park, we can classify industrial park according to 5 levels: very high carbon emission industrial zone, high carbon emission industrial zone, medium carbon emission industrial zone, low carbon emission industrial zones and the industrial park has very low carbon emissions. The low carbon industrial park index was applyied to assess and classify Trang Bang industrial park, Tay ninh province. The result showed that, the low carbon industrial park index of Trang Bang industrial park is in the range of 27,99 – 62,14 in the period 2016 – 2020. The Trang Bang industrial park is classified with 03 levels: medium carbon emission industrial zone, high carbon emission industrial zone and very high carbon emission industrial zone.

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.

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.

The alkaline volcanic rocks were distributed in the SokLu mountains, in the territory of Quang Trung commune, Thong Nhat district, Dong Nai province, and considered Soklu Formation, exposed as a truncated cone-shaped dome with an area of more than 12.65km2, located close to the National Highway 20 from Dau Giay to Da Lat, 3km north of Dau Giay junction, with an altitude of 408.3m, prominent in basalt cover, the formation consists mainly of trachyandesite nearly homogeneous in the whole massif. The rock is ashen-grey, light grey colored, porphyritic texture with the microcrystal groundmass of needle-shaped plagioclase arranged parallel to each other (trachytic texture), directive structure (flow structure). The phenocrysts mineral composition accounts for about 10÷15%, scattered, sometimes concentrated in clusters to form a phenocrysts clump texture, including plagioclase (40÷60%), pyroxene (20÷25%), olivine (15÷20%), the groundmass mineral composition accounts for about 85÷90%, including main glass (45-55%) and the rest are needle-shaped plagioclase microcrystals arranged directive in clusters (15÷20%), pyroxene (10÷15%), ore (>5%). The results of research on lithogeochemical characteristics and isotopic compositions of Sr, Nb, Pb show that SokLu alkaline volcanic is characterized by high SiO2 content (56.08-57.58wt%), a high total of alkaline (Na2O+K2O) vary from 9.90-10.87wt%, low Na2O/K2O ratio (1.09-1.36), it is typical of the alkaline sodium and total iron Fe2O3t accounts for 5.74-3.37wt%, low iron content F=FeO/MgO (1.62-2.55) and K2O/MgO ratio of 1.33-2.00. Soklu alkaline volcanic has high Sr content (1244.30-1298.33ppm), the total content of light rare earth elements is mainly ∑LREE (321.57-339.13ppm), but high rare earth elements occupy the secondary ∑HREE (21.04-21.47ppm), Rb/Sr ratio of 0.08-0.09. The primitive isotope 87Sr/86Sr ratio of 0.704792-0.704807, 143Nd/144Nd ratio of 0.512716-0.512722, 206Pb/204Pb ratio of 18.2282-18.24, 207Pb/204Pb ratio of 15.5839-15.59, 208Pb/204Pb ratio of 38.4560-38.50, reflecting the mantle origin. The analysis result of Ar-Ar isotopic age of Soklu alkaline volcanic for 0.33±0.17Ma, corresponding to Middle Pleistocene.

Studying the characteristics and fluctuate of oceanic factors have very important role in fisheries oceanography, help us to have a more general view about the hydrodynamic - hydrological regime in the research region sea, have great significance in the zoning sea region serving the exploitation and protection resources and marine environment. Based on oceanographic data collected from 02 survey trips in the coastal waters of Ben Tre in November 2020 (Northeast monsoon season) and May-June 2021 (Southwest monsoon season) from 30 stations, some oceanic factors such as: temperature, salinity and chlorophyll - a were analyzed. Statistical analysis results show that some oceanic factors in coastal waters of Ben Tre have strong fluctuations in the coastal area, at the sea surface layer according to the monsoon seasons of the year. In the southwest monsoon, appeared two region has thermocline: region distance to coastline less 15 nautical at a depth of 2-5m and region distance to coastline 30 - 45 nautical at a depth of 13 - 25m. In Northeast monsoon, the appearance of salinity isovalue line 33,0‰ moving from offshore to coastal waters, this salinity isoline will weaked and gradually disappear when the southwest monsoon returns. The average of chlorophyll a in the entire water blocks is approx 1,3µg/l, fluctuated strongly at the depth from 0 to 15m, the maximum value of chlorophyll - a is scattered at different depths with different values in each wind season.