Journal of Tropical Science and Engineering

CHARACTERIZING AEROSOL PARTICULATE MATTER IN BIEN HOA CITY, DONG NAI PROVINCE: MASS CONCENTRATION LEVELS, RATIOS, AND LONG-RANGE TRANSPORT BY HYSPLIT MODEL

2025-09-11T06:43:30+00:00

Bien Hoa City, Dong Nai province, is showing signs of increasing pollution. In this study, aerosol particulate matter - PM samples (including TSP, PM10, PM2.5) were collected uniformly (same time, same location, same 24-hour period) on specialized sampling paper using high volume air samplers (HVAS, Tisch Environment, Inc.) for the first time. PM samples were quantified using a Mettler Toledo XS205 weight scale and source apportionment was traced using the backward trajectory analysis model HYSPLIT. The results showed that the mass concentrations of TSP, PM10, PM2.5 during the dry season (2023) were 97.4 ± 11.4 µg/m³, 64.4 ± 7.9 µg/m³, 49.89 ± 7.2 µg/m³ respectively; and during the wet season (2023) were 71.5 ± 10.3 µg/m³, 51.4 ± 8.7 µg/m³, 36.8 ± 7.5 µg/m³ respectively. The concentrations of PM10 and PM2.5 exceeded the recommended values of the World Health Organization (WHO), especially PM2.5 which exceeded both the WHO guidelines and the national limit of QCVN 05:2023/BTNMT. The distribution of fine particulate matter PM₂.₅ shows a significant dominance in the overall particulate composition, accounting for approximately 52-78% depending on the season. The HYSPLIT backward trajectory analysis suggests that distant sources may influence air quality in the study area; however, this observation requires further verification due to the limited sample size.

PROTECTIVE PERFORMANCE OF THE MIGRATING CORROSION INHIBITOR MCI-VN FOR STEEL REINFORCEMENT IN CONCRETE PORE SOLUTION

2025-05-15T04:09:20+00:00

A blended corrosion inhibitor (MCI-VN) based on a synergistic combination of inorganic and organic salts with a nonionic surfactant is proposed to protect steel reinforcement in concrete under chloride exposure. The composition is suitable for use as an admixture in the production of new reinforced concrete structures or repair mortars, as well as for surface application to existing structures (migrating corrosion inhibitor). This study evaluates the anti-corrosion properties of the inhibitor in the concrete pore solution. The assessment was performed using electrochemical methods (potentiodynamic polarization and impedance spectroscopy) and gravimetric analysis. As the inhibitor concentration (Cinh) increased in the 0.25-5.0 wt.% range, the inhibition efficiency rose to 92-97%, depending on the evaluation method. During 30-day gravimetric experiments, complete suppression of corrosion was observed at Cinh ≥ 2.0 wt.%. Comparison with the commercial inhibitor IFKhAN-80 showed comparable or superior protective performance under equivalent conditions. Therefore, MCI-VN can be considered an effective solution for improving the corrosion resistance of reinforced concrete structures in chloride-containing environments.

SYNTHESIS AND APPLICATION OF Ag/CuO/Fe₃O₄/ACB DERIVED FROM BRUCEA JAVANICA FOR PHOTOCATALYTIC FENTON DEGRADATION OF CRYSTAL VIOLET DYE

2025-06-14T08:27:35+00:00

The relentless release of organic dyes into water bodies has raised critical environmental concerns, demanding the development of efficient, sustainable, and reusable catalytic systems for wastewater treatment. In this study, we report the synthesis of a multifunctional Ag/CuO/Fe₃O₄/activated carbon beads (ACB) composite derived from natural Brucea javanica seeds through a one-step carbonization method. The resulting composite combines the magnetic properties of Fe₃O₄, the visible-light-responsive nature of CuO, and the surface plasmon resonance of Ag, creating a robust catalyst capable of highly efficient heterogeneous heterogeneous photo-Fenton-like-like degradation of crystal violet (CV) dye under visible light. Under optimized conditions (pH 7, H₂O₂ 0.05 M, catalyst dosage 2 g/L, and Fe³⁺:Cu²⁺:Ag⁺ ratio of 2:1:0.5), the Ag/CuO/Fe₃O₄/ACB composite achieved a remarkable CV removal efficiency of 98% within 90 min. Even after five consecutive reuse cycles, the composite retained a high degradation efficiency of 83%, demonstrating excellent stability and reusability. Comprehensive structural analyses by XRD, FTIR, SEM, TEM, and VSM confirmed the successful formation and stability of the composite. This work not only offers a simple, eco-friendly approach to producing high-performance photocatalysts but also highlights the potential of using agricultural by-products for sustainable environmental remediation. The Ag/CuO/Fe₃O₄/ACB composite is a promising candidate for large-scale wastewater treatment and provides a strategic solution to combat organic dye pollution.

MORPHOMETRIC RELATIONSHIPS BETWEEN SAGITTAL OTOLITH SHAPE AND BODY SIZE IN FIVE MARINE FISH SPECIES FROM LANG CO - HAI VAN, VIETNAM

2025-07-29T03:48:01+00:00

This study examines the relationship between sagittal otolith morphology and body size in five common marine fish species-Selaroides leptolepis, Sardinella gibbosa, Gerres filamentosus, Lutjanus russellii, and Selar crumenophthalmus-from the Lang Co - Hai Van coastal area of Vietnam. A total of 210 specimens were analyzed using Basic Dimension Parameters (BDPs: otolith length, width, area, and perimeter), Shape Indices (ShIs), and somatic traits (total length and body weight). MANOVA and Linear Discriminant Analysis (LDA) results revealed significant interspecific differences in otolith shape, with high classification accuracy (84.78-100%) and perfect discrimination for Lutjanus russellii. Regression analyses demonstrated strong linear correlations between otolith dimensions and body size, especially with otolith height and area (R² up to 0.962). Additionally, length-weight relationships (LWRs) showed species-specific allometric growth patterns: positive allometry in Gerres filamentosus and Selaroides leptolepis, and negative allometry in Lutjanus russellii, Sardinella gibbosa, and Selar crumenophthalmus, suggesting ecological and physiological variability across taxa. These findings support the use of otolith morphometrics for species identification and fish size estimation, with practical applications in fisheries biology, dietary analysis, and historical ecology.

ASSESSMENT OF COASTAL WATER QUALITY IN BAI TU LONG NATIONAL PARK, QUANG NINH PROVINCE

2025-07-28T14:38:08+00:00

Coastal seawater quality plays an important role in protecting the organisms and life of marine ecosystems. This study evaluates the quality of coastal seawater in Bai Tu Long National Park through field measurements and laboratory analyses. The assessment is based on physical, chemical, and biological parameters, and the results are compared to the standards outlined in QCVN 10:2023/BTNMT. The research team surveyed the research area and selected 25 sampling locations along the coast, encompassing both large and small islands in the Bai Tu Long National Park. According to the measurement and analysis results, the average temperature and salinity of coastal seawater are 27.03 ± 0.46°C and 25.69 ± 1.69‰, respectively; the average values of pH, TSS, and DO are all within the permissible limits. The coastal seawater environment is of high quality to protect the underwater habitat through the pH, DO, and TSS parameters. When compared to the standard, the Fe and P parameters are significantly lower than the permissible limit, safeguarding human health and the marine ecosystem. However, the 8% proportion of low DO readings (<5 mg/L) indicates localized hypoxic conditions, necessitating ongoing site-specific monitoring. The total coliform density in seawater exceeded the allowable limit, with an average density of 1414 ± 266 MPN/100 mL. The primary source of biological pollution in this area is the waste from aquaculture, particularly from fish and mollusk cages. During the sampling, it was observed that the fish in the cages were infected with fungal diseases. It is crucial to take timely measures to address pollution and implement effective solutions for managing the discharge of aquaculture waste in the Bai Tu Long National Park area.

AN ECONOMIC EFFICIENCY ANALYSIS OF AQUACULTURE FARMS IN BAI TU LONG BAY IN A 20 - YEAR CYLCLE

2025-07-30T08:48:30+00:00

Aquaculture is one of the main commodity production industries, playing an important role in a coastal country like Vietnam. The objective of this study is to evaluate the economic efficiency of aquaculture farms using cost-benefit analysis (CBA) and sociological survey interviews in Bai Tu Long area. A total of 51 household and aquaculture cooperative questionnaires were used to evaluate the economic efficiency of 4 typical aquaculture farms over a 20-year period. The results showed that the grouper farm had the highest investment capital but the lowest efficiency (B/C = 1.05; Pnpv = 0.01). In contrast, clam, snail and oyster farms have lower investment capital than fish farms but higher efficiency, especially clam farms (B/C = 1.82; Pnpv = 0.47), followed by snail farms (B/C = 1.43; Pnpv = 0.27) and oyster farms (B/C = 1.37 AND Pnpv = 0.19). The analysis results are an important information base providing aquaculture farmers with appropriate adjustments to maximize the benefits of the farms, and policy managers can also make reasonable decisions and recommendations to ensure the sustainable development of the aquaculture industry in the future.

BIOLOGICAL CHARACTERISTICS OF SOME FILAMENTOUS FUNGAL STRAINS ISOLATED FROM RUBBER SURFACE AT THE DAM BAY MARINE CLIMATIC TESTING STATION, NHA TRANG

2025-07-29T03:54:32+00:00

Fungal strains can readily colonize and thrive on the surface of rubber materials, particularly in tropical coastal or monsoon climates where high humidity, temperature, and salinity create favorable growth conditions. This study aimed to isolate and characterize filamentous fungal strains inhabiting the surface of rubber materials exposed to coastal climatic conditions at the Dam Bay Marine climatic testing station, Nha Trang, Vietnam. Three rubber samples were collected and assessed for microbial coverage following ASTM G21-15 (2015). High-resolution images were analyzed using ImageJ software, revealing fungal colonization levels ranging from 48.23 ± 3.7% to 68.23 ± 4.1%. Based on morphological characteristics, five isolates were obtained and classified into four genera: Fusarium, Aspergillus, Penicillium, and Nigrospora. All isolates exhibited optimal growth on PDA medium and demonstrated salt tolerance up to 4% (w/v) NaCl, indicating physiological adaptation to saline environments. Screening for extracellular laccase activity showed that DB.F05 was the only strain producing laccase, with a lysis zone diameter of 6 ± 0.5 mm. The identity of DB.F05 was confirmed by combining morphological observations with ITS region sequencing, showing 100% similarity to Nigrospora lacticolonia CGMCC 3.18123 (GenBank accession PV942108). These findings provide the first record of N. lacticolonia isolated from rubber surfaces in a tropical marine environment and reveal its potential enzymatic capability relevant to polymer modification or degradation. These are the results of a preliminary study to record the presence and biological characteristics of filamentous fungi on rubber surfaces in tropical coastal environments, providing a foundation for future studies on biodegradation mechanisms and antifungal preservation strategies.