VNUHCM Journal of Earth Science and Environment

Characteristics and Trends of Meteorological and Hydrological Drought in the Srepok River Basin

Lam Van Nguyen — 2026-01-09

Srepok is an important river basin in the Central Highlands region. In recent years, droughts have occurred more frequently, threatening the sustainable development of this region. Therefore, studying the characteristics and trends of droughts is extremely necessary to propose appropriate response solutions. In this study, data from 9 rainfall stations and 1 hydrological station during the period of 1982 - 2022 were used to assess the fluctuations of droughts over time scales. The Mann-Kendall non-parametric test method and Sen slope estimation were applied to analyze the trends. The results show that droughts start from August to November every year, about 2.5 times higher than the remaining months. The duration of droughts ranges from 5 to 15 months, with a median of 7 months. The SPI7 index recorded more severe droughts at a very severe level than SPI3 and SPI5, the most severe drought occurring in 1994. The SSI index also fluctuated strongly, especially in 2014 with SSI5 reaching 37.7. The strongest drought intensity was in 2004 and 2015 with SSI5 reaching 1.7. The SPI tended to increase in the dry season and decrease slightly in the rainy season. Although the period 1982 - 2002 had many droughts at a mild and severe level, the very severe drought tended to increase in the later period. The study shows that combining SPI and SSI to assess drought trends is effective, contributing to optimizing short-term and long-term drought response measures.

An Integrated Framework for Air Quality Management in Vietnam: Combining Emission Inventory, GIS, Modeling, and Multi-Criteria Decision Analysis

Nguyen Viet Vu — 2026-01-09

Air pollution is currently one of the most serious challenges to public health and sustainable development. In Vietnam, although there have been positive improvements in managing air quality recently, many local programs still lack a strong scientific basis and effective techniques to identify which air quality management (AQM) solutions should be prioritized. Because of this, efforts to reduce air pollution are often scattered, unfocused, and not as effective as they could be. This study presents an integrated AQM framework tailored to Vietnam context. The framework combines four key approaches: emission inventory, geographic information systems (GIS), air pollution dispersion modeling and multi-criteria decision analysis, especially the combined AHP–TOPSIS method. It outlines six clear steps designed to provide a thorough way to manage air quality and help decide which solutions should come first. Within this framework, ten criteria have been developed to evaluate and prioritize these solutions. This approach can be applied widely across different provinces and cities in Vietnam, covering all major sources of air pollution such as industrial points, traffic, area-wide sources, and natural biological sources. Not only does this method ensure a systematic and practical way to manage air quality, but it also helps build a solid scientific basis for policy - making, ultimately improving how effectively Vietnam controls air pollution

Investigation and optimization of the analytical procedure for total mercury in particulate matter using chemical digestion with BrCl

Huong Thi Dieu Pham — 2026-01-16

Mercury (Hg) is a highly toxic heavy metal with a complex biogeochemical cycle, especially atmospheric Hg, as it can exist in both particulate and gaseous phases. Although US-EPA Method IO-5 has been widely applied for atmospheric Hg monitoring, it only provides recommendation and lacks details on procedural steps. Therefore, this study aimed to investigate and optimize the PBM analysis protocol using chemical digestion based on the IO-5 guideline, utilizing a WA-5F instrument (NIC, Japan). The results showed that the method detection limit (MDL) reached 0.22 pg/m³, which is sensitive enough for PBM analysis under various environmental conditions. Blank sample analyses indicated low and precise controlled background contamination. The repeatability of the procedure showed a coefficient of variation (CV) mostly below 20%, conforming to the requirements according to reference values from major global Hg monitoring networks. Recovery rates ranged from 84.6-101.6% (average 92.2 ± 6.8%) for spiked samples and 99.8% for certified reference materials, demonstrating the reliability of the procedure. Furthermore, the BrCl oxidizing agent was capable of extracting almost all Hg in a single sample treatment. A comparison with the direct thermal decomposition method using the MA-3 Solo instrument showed a high correlation (R² = 0.96), confirming the accuracy and practical applicability of the developed method. The research results contribute to establishing an effective analytical procedure for Hg monitoring in the atmosphere and provide crucial scientific data for assessing health risks from PBM exposure in the context of increasing urban pollution.