Environment and Natural Resources Journal

Spatio-Temporal Analysis of PM2.5 Concentrations through Integration of Aerosol Optical Depth and Sentinel-5P Data Using Google Earth Engine

Fri, 01 May 2026 00:00:00 +0700

Air pollution in Northern Thailand is a persistent environmental issue, particularly during the dry season, posing significant health risks. This study used multiple remote-sensing data sources to explore spatio-temporal PM2.5 variations in Chiang Mai Province from 2020 to 2024. Ground-based PM2.5 measurements were merged with Terra-Aqua aerosol optical depth (AOD) and Sentinel-5P carbon monoxide (CO) and nitrogen dioxide (NO₂) data within the Google Earth Engine platform. Multiple linear regression models were employed to estimate ground-level PM2.5 concentrations and generate spatial distribution maps. Central lowland and northern areas of Chiang Mai consistently exhibited higher PM2.5 levels, particularly in March and April. The model achieved an R² of 0.77 and a root mean square error (RMSE) of 14.60 μg/m³, with an overall correlation of 0.88 between satellite-derived and ground-based measurements. Seasonal analysis revealed enhanced model performance during the burning period (January-April; R²=0.72, RMSE=17.31 μg/m³), compared with the non-burning period (May-December; R²=0.26, RMSE=8.32 μg/m³). During the 2020-2024 burning periods, average PM2.5 concentrations were 51.33, 45.62, 25.18, 49.81, and 41.11 μg/m³, respectively, peaking at 79.18±16.90 μg/m³ in March 2023. Integrating AOD with Sentinel-5P CO and NO₂ data improved estimation accuracy and hotspot identification, highlighting the potential of cloud-based geospatial platforms for comprehensive air quality monitoring.

Assessing Eutrophication in a Small Polluted Reservoir Through Landsat 8 Band-Ratio Models: The Case of Xuan Khanh Reservoir, Hanoi, Vietnam

Tue, 31 Mar 2026 00:00:00 +0700

This study develops an integrated framework for monitoring eutrophication in Xuan Khanh Reservoir (XKR), Hanoi, Vietnam, by combining in-situ observations with Landsat 8 (L8) reflectance data. A total of 66 field measurements collected during four surveys (October 2024-July 2025) were used to calibrate an empirical model for estimating the Trophic State Index (TSI) from L8-derived reflectance. The near-infrared to red ratio (B5/B4) achieved the best performance (R²=0.81; RMSE=2.4). Nineteen cloud-free L8 images acquired between July 2021 and July 2025 were then applied to map spatiotemporal TSI variations. Results show that XKR consistently remained in a highly eutrophic to hypereutrophic state, with TSI values ranging from 64 to 82. Spatial patterns revealed persistent hotspots in shallow northern zones and inlet-connected areas, driven by external nutrient inputs and surrounding land-use pressures. These findings demonstrate the value of L8 as a cost-effective monitoring tool for small, polluted reservoirs, offering evidence to guide nutrient reduction, wastewater management, and land-use regulation. The proposed approach provides transferable insights for long-term trophic state assessment and can support policy decisions aimed at safeguarding freshwater resources in data-limited regions.

The Phytoremediation Potential of Lemna minor L. on Heavy Metal Accumulation, Biochemical Responses, and Growth Tolerance

Thu, 04 Jun 2026 00:00:00 +0700

Duckweed (Lemna minor L.) is an efficient aquatic plant that accumulates heavy metals. This study aimed to investigate the ability of duckweed. To accumulate selected heavy metals (Ni, Cu, Zn, Fe, Ba, Mn, and Co) at 5 mg/L concentrations of each metal, and to study the effects of metals on plant growth and biochemical changes in the plant. This study was conducted for 14 days to control the environmental conditions. The accumulation of metal inside the plant tissue, bioconcentration factor (BCF), and relative growth rate (RGR) were measured at the end of the experiments, while plant fresh and dry weight, total chlorophyll, and protein and proline contents were measured at the beginning and end of the experiments. The results showed that the highest metal accumulation in plant tissue and BCF were 4.112 and 0.822, respectively, in the iron treatment, while the lowest values were 2.334 and 0.466, respectively, in the Ba treatment. The highest reduction in fresh weight and growth percentage was in the Ba treatment, the highest reduction in chlorophyll content was in the Ba treatment, and the lowest protein content was in the Cu treatment. Therefore, the results indicate that Duckweed can tolerate selected heavy metals and can be used in phytoremediation technology.

Land Use and Land Cover Dynamics of Small Inhabited Islands in South Bangka, Bangka Belitung, Indonesia (2004-2024)

Henri Henri, Luchman Hakim, Catur Retnaningdyah, Brian Rahardi — Thu, 30 Apr 2026 00:00:00 +0700

Anthropogenic land use and cover changes pose a significant threat to small island ecosystems, yet systematic monitoring remains limited. This study analyzes LULC dynamics over 20 years (2004-2024) on three inhabited islands in South Bangka, Bangka Belitung, Indonesia. The objectives were to assess LULC changes, evaluate their impacts on biodiversity, and examine the effectiveness of existing policies using multi-temporal Landsat and Sentinel-2 imagery. The supervised classification achieved an overall accuracy of 85.3-91.2% with Kappa coefficients of 0.82-0.89, indicating substantial to nearly perfect agreement. The results revealed distinct transformation patterns across the islands. Tinggi Island demonstrated resilience through the recovery of secondary dryland forests (from 68.52 ha to 113.48 ha), despite the presence of illegal tin mining activities that created artificial wetland systems. In contrast, Kelapan Island faced severe degradation, with extensive forest loss and habitat fragmentation. This resulted in a 29.5% decline in mean patch size and a critical loss of connectivity. Conversely, Pongok Island showcased successful conservation efforts, significantly expanding its mangrove ecosystem, which enhanced its blue carbon capacity, even amid agricultural intensification. The assessment of biodiversity impacts confirmed that maintaining patch sizes above 20 hectares and ensuring high connectivity are essential thresholds for species conservation. However, current LULC management policies demonstrate limited effectiveness due to regulatory gaps between marine and terrestrial governance frameworks. The study concludes that integrated conservation strategies, including adaptive management and corridor restoration, are urgently needed to balance development pressures with the preservation of ecosystem integrity.

Modeling Land-Use Transitions under Conflicting Conservation and Land Tax Policies in Bang Kachao, Thailand

Thu, 30 Apr 2026 00:00:00 +0700

Bang Kachao Subdistrict faces a policy conflict between the 2019 conservation zoning regulation, which mandates at least 25% green cover, and the Land and Buildings Tax Act in 2019, which progressively increases idle land tax rates from 0.5% to 3% within three years. The rising tax burden has accelerated land conversion from vacant and forested plots to monoculture farms, threatening local ecosystem integrity. Using high-resolution drone imagery and high-resolution satellite imagery obtained from Google Earth Pro for the year 2005 and 2015, six land-use classes were mapped and projected to 2045. The model achieved an overall accuracy of 89.7% (Kappa = 0.86), forecasting a 14.1% decline in forest area (-0.144 km²), 15.9% agricultural net increase (+0.185 km²), and an increase in idle land from 0.031 km² to 0.094 km² over the 40-year period. Field surveys confirmed that landowners replaced nipa palm wetlands with eucalyptus plantations to qualify for tax exemptions. These results indicate that progressive taxation can undermine conservation policies. It is recommended that subdistrict governors establish Memoranda of Understanding (MOUs) with landowners to support nipa palm and native forest restoration through capped tax rates and integrated land-use zoning.

Management Model for Rungan Watershed, Central Kalimantan, Indonesia: A Comprehensive Approach to Achieving Conservation and Community Development Goals

Endy Endy, I Nyoman Sudyana, Herwin Sutrisno, Raden Mas Sukarna — Fri, 10 Jul 2026 00:00:00 +0700

The Rungan Watershed is facing an alarming rate of environmental degradation yet continuing to support the livelihoods of local communities. Therefore, this study is essential for addressing these issues and formulating adaptive management model. This research aims to assess environmental conditions and social economic aspects to formulate management model that is expected to serve as a framework for sustainable development in Palangka Raya City. By applying both qualitative and quantitative approaches, the study collects ecological, economic, and socio-cultural data to inform the development of management strategies. Land cover, land use, and vegetation density are assessed using remote sensing imagery and land cover maps. The analysis of forest vegetation density classes is conducted through the Normalized Difference Vegetation Index (NDVI), utilizing data from Landsat imagery. Socio-cultural information is gathered through interviews and observations. The study identifies various land cover condition, information on social economic condition that serve as a basis for developing a zoning based management model that categorizes the Rungan Watershed into conservation, buffer, and general utilization zones. This model accommodates the diverse interests of multiple stakeholders within a sustainable development framework. The study concludes that the zonation management of the sub-basin must align with the biophysical ecological conditions of the area, address existing challenges, and promote community welfare.

Influence of Environmental Factors and Heat Island Intensity on Outdoor Thermal Comfort Among Residents in Section 7, Shah Alam, Selangor, Malaysia

Fri, 29 May 2026 00:00:00 +0700

The aim of this study was to investigate the influence of meteorological factors and urban heat island intensity (UHII) on outdoor thermal stress among residents in Section 7, Shah Alam, Selangor. Meteorological data, including temperature, relative humidity, and wind speed, were collected for Shah Alam from April to September 2024. The UHII was determined by subtracting the surrounding rural temperature from the urban temperature. The physiological equivalent temperature (PET) was calculated using RayMan software, and statistical analyses were conducted using the Statistical Package for the Social Sciences version 28. The UHII in Shah Alam ranged from 0°C to 3.7°C, with a mean of 0.743±0.687°C. The PET analysis indicated that 57.9% of the respondents reported warm perception of their environment (moderate heat stress), with PET values among respondents ranging from 25.90 to 32.00 and a mean of 29.121±1.235. A strong positive correlation was observed between temperature and PET (r=0.835, p=<0.001), as well as a moderate positive correlation between UHII and PET (r=0.404, p=<0.001), while a negative relationship was found between relative humidity and PET (r=-0.579, p=<0.001). Temperature (B=1.160, p=<0.001) and wind speed (B=-0.911, p=<0.001) were significant predictors of PET among residents in Shah Alam. In conclusion, temperature and wind speed significantly influence outdoor thermal comfort in Section 7, Shah Alam. Local authorities should implement mitigation measures such as integrated urban planning, expanded green spaces and infrastructure, and sustainable land use, which can be effective solutions to reduce UHII and air temperature while enhancing wind flow and outdoor thermal comfort in urban areas.

Process Optimization of Glycerol-to-Triacetin Conversion in Clean Technology Applications: In Situ Water Removal for Enhanced Reaction Performance in Sustainable Biodiesel Byproduct Valorization

Nuryoto Nuryoto, Nasywa Hanifah, Najiha Hariani, Rafiif Nur Tahta Bagaskara — Fri, 19 Jun 2026 00:00:00 +0700

Increasing biodiesel production generates excess glycerol, which has a declining economic value. Converting glycerol into triacetin, a value-added fuel additive, offers a promising solution. However, the reversible nature of the esterification reaction and the formation of water reduce selectivity. Therefore, this study was conducted to evaluate the effect of in situ water removal on reaction performance in terms of acetic acid conversion and the resulting triacetin product. Experiments were conducted in a batch reactor through three clearly defined stages. In Stage 1, the optimal glycerol-acetic acid molar ratio (1:3-1:5) was determined at 100°C and 700 rpm, using a 5% natural zeolite catalyst (based on acetic acid mass), and a reaction time of 4 h with in situ water removal. In Stage 2, residual water was removed by fractional distillation at 105°C until bubbling ceased. Stage 3 comprised the main reaction, where the distillate containing monoacetin, diacetin, triacetin, and glycerol was reacted with fresh acetic acid at the optimal ratio, while in situ water removal continued to enhance triacetin formation. Acetic acid conversion was analyzed by acid-base titration using 0.5 N NaOH, and triacetin was identified by GC-MS. This innovation showed excellent results, achieving 94.00% conversion of acetic acid with 85.58% selectivity for triacetin at 110°C and a 1:5 glycerol-to-acetic acid molar ratio. These results showed that in situ water removal intensified esterification by shifting the equilibrium, enhancing triacetin conversion and selectivity. This strategy advances glycerol valorization and supports the production of sustainable fuel additives within integrated biorefinery systems.

Decadal Rainfall Distribution Shift in Northern Coastal Java: Histogram-Based Clustering Using Observations and CHIRPS

Thu, 04 Jun 2026 00:00:00 +0700

Coastal lowlands are highly vulnerable to seasonal changes and rainfall variability, which affect the risk of floods and droughts. Therefore, this study aimed to analyze decadal changes in the monthly rainfall distribution along the northern coast of Central Java (Pantura), using data from 51 stations of the Meteorology, Climatology, and Geophysics Agency (BMKG) and the Climate Hazards Group InfraRed Precipitation with Station data (CHIRPS) v2.0. A smoothed histogram was used to calculate the probability density of rainfall for each decade. Subsequently, the distribution between decades was compared using 6 metrics to assess distribution displacement, divergence, overlap, and shift in peak, centroid, and width. The level of uncertainty was measured using the bootstrap method at confidence levels of 5%, 10%, and 25%. The six metrics were normalized and combined into a single composite index called the Total Normalized Index (TNI). K-means clustering was then applied to map changes according to the same rainfall patterns. Analysis of both sources showed a gradient pattern from west to east. Rainfall was concentrated in the west, with moderate changes in structure in the central area, and a more dispersed rainfall pattern with high variability in the east, particularly from 2011 to 2020. CHIRPS data recorded the regional trends but tended to cloud out local fluctuations. This study contributed to new investigations since the implementation of histogram-based rainfall distribution analysis into a composite index. The application of this method as part of a spatial clustering model was proposed to map alterations in rainfall distribution each decade. The method also helped in evaluating coastal climate risk and adaptation planning.

Sustainable Valorization of Domestic Onion Waste: Comprehensive Characterization for Nutrient Recovery and Waste Volume Reduction

Anila Zahid, Renu Khedkar, Shashi Sharma, Sanjay Rajput — Thu, 25 Jun 2026 00:00:00 +0700

Allium cepa L., commonly known as onion, is one of the most widely cultivated vegetables worldwide, valued for its characteristic flavor, aroma, and pungency. It is extremely concerning that around one million tonne of onion waste is produced throughout distribution, processing, and consumption. Characterization of onion waste is essential for its valorization. The study’s goal was to identify the nutritional and nonstructural carbohydrate content, antioxidant, antimicrobial activity and phytochemical elements present in the waste. The onion waste was cleaned and dried at 60°C in an air-circulating tray dryer, and ground into a fine powder. It was found to contain moisture (3.67%), protein (8.56%), carbohydrate (70.47%), fat (0.64%), crude fibre (4.49%), dietary fibre (69.06%), and insoluble dietary fibre (63.64%) and provides 321.88 kcal of energy per 100 g. The non-structural carbohydrates in the onion waste were glucose (4.40%), fructose (1.75%) and sucrose (1.10%). The ethanolic onion waste extract was found to contain phytochemicals anthraquinones, anthocyanins, phenols, flavonoids, glycosides, terpenoids, flavonoids, and tannins. Using DPPH and hydroxyl radical scavenging activity, the antioxidant activity of ethanolic onion waste extract was revealed to be strong at various concentrations. These values ranged from 42.34% to 70.50%, 65.8 to 60.5%, respectively. The ethanol extract of onion waste was found to have the strongest anti-microbial effects on Escherichia coli and Staphylococcus aureus. Onion waste characterization provides valuable insights into its potential as a source of bioactive compounds facilitating its utilization in nutraceuticals and functional foods. This approach promotes sustainable waste management and resource utilization while unlocking the hidden potential of onion waste.