Physics and Chemistry of the Earth最新文献

{"title":"Mining overburden sand from lignite mines as a partial replacement for fine aggregates in concrete","authors":"B. Balakrishna Prasanna ,&nbsp;G.R. Senthil Kumar ,&nbsp;P. Gopinathan ,&nbsp;Amit Karmakar ,&nbsp;Md Mustaque Ansari ,&nbsp;T. Subramani","doi":"10.1016/j.pce.2025.104124","DOIUrl":"10.1016/j.pce.2025.104124","url":null,"abstract":"<div><div>Extensive opencast mining activities have resulted in massive generations of overburden dump materials which have become a significant global contributor to environmental pollution, land degradation and pose a threat to environmental sustainability. This study explores the potential of utilizing overburden material of the Neyveli lignite mine area as a sustainable alternative to natural river sand for construction application. The research involves a comprehensive physio-chemical and mechanical analysis of overburden sand extracted from the Neyveli mine site area, assessing its mineral contents, distribution of particle sizes and compressive strength. The result reveals that overburden sand is predominantly composed of quartz and alumina, meets IS standards for fine aggregates and demonstrates comparable performance to manufactured sand. Concrete specimens incorporating overburden sand exhibited satisfactory strength with a compressive strength of 58 MPa at 28 days, which is comparable to manufactured sand-based concrete 60 MPa at 28 days. Additionally, XRD, XRF, SEM and sieve analysis confirmed that overburden extracted sand possesses desirable properties for construction applications. The study highlights the dual benefits of repurposing overburden i.e., reducing environmental hazards and mitigating the depletion of natural sand resources in rivers. Overburden extracted sand proves to be a viable and eco-friendly substitute for fine aggregates. Further studies on long-term durability, large-scale implementation and economic feasibility are recommended to enhance its widespread adoption in sustainable construction.</div></div>","PeriodicalId":54616,"journal":{"name":"Physics and Chemistry of the Earth","volume":"141 ","pages":"Article 104124"},"PeriodicalIF":4.1,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145236142","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Trend analysis of hydro-meteorological variables using Mann-Kendall and Sen's Slope with Standardization (SSS): Case study of the Kızılırmak catchment, Türkiye","authors":"Ahmad Abu Arra ,&nbsp;Muhammed Zakir Keskin ,&nbsp;Eyüp Şişman","doi":"10.1016/j.pce.2025.104115","DOIUrl":"10.1016/j.pce.2025.104115","url":null,"abstract":"<div><div>In recent times, trend analysis has become a focal point and an essential tool across various disciplines, particularly in reaction to the impacts of climate change. As classical methods and regarding the literature, the Mann-Kendall test (MK) and Sen's Slope (SS) are the most widely-used trend methods and hold paramount significance in trend analysis, particularly when studying hydro-meteorological variables over time. MK determines the trend direction, whereas the trend slope is computed with SS. However, they are used without assessing their compatibility and agreement in detail. This research applies Sen's Slope to the Standardized data (SSS) to evaluate the compatibility and agreement between MK and SS methods. Also, this research aims to analyze the temperature and precipitation trends over the Kızılırmak catchment in Türkiye from 1970 to 2023 using MK, SS, and SSS, as well as presenting the trend maps, including the actual trend maps. The results showed that the SSS approach is closer and compatible with MK than the results obtained by the classical SS. For the whole time period, the most significant temperature increases are observed in the southern part of the catchment, particularly in Kayseri and Develi stations (2.5 <span><math><mrow><mo>°</mo></mrow></math></span> C/54 years). Based on a specified confidence level, 15 out of 20 stations across the Kızılırmak catchment showed an increasing trend in temperature. For precipitation data, 2 out of 8 stations (Kırşehir and Kırıkkale) showed a negative, insignificant slope of approximately 1.1 mm/54 years, while the remaining stations showed a positive, significant, and insignificant slope reaching up to 5.2 mm/54 years. Finally, the practical implications, future recommendations, and different adaptation strategies were proposed based on the obtained results.</div></div>","PeriodicalId":54616,"journal":{"name":"Physics and Chemistry of the Earth","volume":"141 ","pages":"Article 104115"},"PeriodicalIF":4.1,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145267134","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Modeling of gravity drainage and molecular diffusion mechanisms during miscible gas injection in naturally fractured reservoirs","authors":"Mustafa Abdullah ,&nbsp;Zaid Ajzan Alsalami ,&nbsp;Deepak J ,&nbsp;Johar Mgm ,&nbsp;Anupama Routray ,&nbsp;Karthikeyan A ,&nbsp;Harjot Singh Gill ,&nbsp;Amanpreet Sandhu ,&nbsp;Hojjat Abbasi","doi":"10.1016/j.pce.2025.104133","DOIUrl":"10.1016/j.pce.2025.104133","url":null,"abstract":"<div><div>Gas injection in naturally fractured reservoirs helps maintain reservoir pressure and improve oil recovery. While gravity drainage has been extensively researched, particularly in immiscible gas injection scenarios, the combined effects of gravity drainage and molecular diffusion during miscible gas injection with CO₂ have not been as widely studied. This lack of a comprehensive understanding of these coupled mechanisms represents a significant research gap, which is critical for optimizing Enhanced Oil Recovery (EOR) strategies in these complex reservoirs. This study aims to address this gap by implementing a hybrid simulation and modeling approach using Eclipse-300 and COMSOL to accurately capture fluid flow and mass transfer phenomena during miscible CO₂ injection. We utilize single-block and multi-block models to investigate the mechanisms of gravity drainage and molecular diffusion. The simulation results, which were validated against available experimental data, show good agreement. Our findings highlight that molecular diffusion plays a significant role in oil recovery, especially for matrix blocks with small heights and very low permeability. For instance, a representative simulation showed a total methane recovery of 35.99 % after 15 h. The results also underscore the importance of using appropriate oil-gas saturation functions for accurate recovery predictions.</div></div>","PeriodicalId":54616,"journal":{"name":"Physics and Chemistry of the Earth","volume":"141 ","pages":"Article 104133"},"PeriodicalIF":4.1,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145227353","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Climate change impacts on the small-scale hydropower potential for the Pungwe B hydropower scheme in Zimbabwe using a multi-model climate ensemble","authors":"M. Muzava ,&nbsp;A. Mhizha ,&nbsp;D.T. Rwasoka ,&nbsp;W. Gumindoga","doi":"10.1016/j.pce.2025.104118","DOIUrl":"10.1016/j.pce.2025.104118","url":null,"abstract":"<div><div>Climate change is anticipated to significantly impact hydropower generation in Southern Africa, especially for small-scale producers. This study investigated climate change impacts on the hydropower potential (Pt) of the Pungwe B hydropower scheme in Zimbabwe. The methodology combined hydro-meteorological data, 15 CMIP6 GCMs, statistical analyses, and HEC-HMS hydrological modelling to simulate streamflow. The impacts of climate change on Pt were determined using trends analysis and Power Potential Duration Curves (PPDC). The Hydrological model performed satisfactorily with a Nash-Sutcliffe Efficiency (NSE) of 0.67 and an R2 of 0.66. The results of Pt revealed a general decrease in future trends, categorized into Mid-Century Future (MCF) and Late-Century Future (LCF). The results indicated that the sustainability pathway (SSP1-2.6) forecasts a steady decline in Pt, with 53 % and 67 % of models showing a decrease during the MCF and LCF periods, respectively. The unsustainable pathways (SSP2-4.5 and SSP5-8.5) have more variable results. In the LCF period, 73 % of the models for SSP2-4.5 and 80 % for SSP5-8.5 predicted a long-term reduction. This highlights that extreme weather events and increased variability may lead to short-term fluctuations in hydropower potential rather than a genuine upward trend. Overall, the findings highlight a projected general decrease in hydropower potential for Pungwe B, with specific decreases ranging from 79.6 MW to 100.3 MW depending on the scenario and time-period. The study concludes that these results underscore the critical need for flexible adaptation plans and infrastructure investments to manage increased climate variability and ensure the long-term resilience and sustainability of the project.</div></div>","PeriodicalId":54616,"journal":{"name":"Physics and Chemistry of the Earth","volume":"141 ","pages":"Article 104118"},"PeriodicalIF":4.1,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145236107","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Paleoenvironmental and organic facies analysis of potential hydrocarbon source rocks in Surghar Range, Kohat Plateau","authors":"Arif Nazir ,&nbsp;Fraz Khalid ,&nbsp;Saeed Abbas ,&nbsp;Muhammad Deen ,&nbsp;Munawar Iqbal ,&nbsp;Umer Younas ,&nbsp;Muhammad Iftikhar Khan ,&nbsp;Rab Nawaz","doi":"10.1016/j.pce.2025.104130","DOIUrl":"10.1016/j.pce.2025.104130","url":null,"abstract":"<div><div>The source, lithology and depositional environment of the organic matter (OM) were determined by analyzing sediment samples from the Surghar Range, Kohat Plateau, Upper Indus Basin, using diagnostic biomarkers. These samples from the M-3, C-2, and N-2 wells were classified as belonging to a mixed kind of OM that was dumped in aquatic sediments under oxygen-starved circumstances based on their aliphatic and aromatic structural components. The origin of OM is supported by the samples' positioning using graphical representation of Pr/nC₁₇ vs. Ph/nC₁₈, the steranes ternary diagram, and the Pristane/Phytane (Pr/Ph) ratio. The OM in Patala, Hangu, Samanasuk, and Shinawari formations exhibit a mature distribution of OEP (0.88–1.04 and 0.88–1.92), CPI, and the ratios of ββ/ββ + αα steranes. With certain biomarker ratios identifying the type of kerogen present, mostly type-II/III, the results indicate that the sediments have significant hydrocarbon potential. This study highlights the need for future research to evaluate the Kohat Basin's hydrocarbon potential more thoroughly while also providing insightful information about the region's geological past and petroleum system.</div></div>","PeriodicalId":54616,"journal":{"name":"Physics and Chemistry of the Earth","volume":"141 ","pages":"Article 104130"},"PeriodicalIF":4.1,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145227472","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Enhancing aridity index assessment in Pakistan's dryland ecosystems: A machine learning approach integrating remote sensing and seasonal lag effects","authors":"Nausheen Mazhar ,&nbsp;Asad K. Ghalib ,&nbsp;Issam Malki ,&nbsp;Noreena ,&nbsp;Sana Arshad","doi":"10.1016/j.pce.2025.104135","DOIUrl":"10.1016/j.pce.2025.104135","url":null,"abstract":"<div><div>Dryland ecosystems are highly vulnerable to increased aridity, thus exacerbating the drought stress. From this perspective, our study aimed to evaluate the aridity index (AI) and Standardized Precipitation Index at a three-month scale (SPI-3) across three arid stations of Pakistan from 1990 to 2023. Seven remote sensing indices were used as covariates with SPI-3 and mean temperature for enhanced prediction. Four well-optimized machine learning models were employed on seasonally decomposed time series. Mann-Kendall and Sen's slope analysis revealed a significant (p &lt; 0.001) increasing trend of AI and SPI-3 values, indicating a comparatively lower aridity in recent years. It was consistent with the increasing trend of NDVI with Sen's slope range from 0.0002 to 0.003. Cross correlation showed a seasonal effect of biophysical indicators on AI with a positive correlation of r = 0.4 with NDVI and r = 0.6 with NDWI at lag 0, indicating a late lag effect. Furthermore, machine learning prediction of AI with a three-month lag size revealed an outperformance of Gradient Boosting Regression with R² = 0.806 and RMSE = 0.076, followed by Random Forest with R² = 0.732 and RMSE = 0.089. The Dry Barren Soil Index (DBSI), NDWI, and SPI-3 gained high feature importance in the highly performed model. Our study highlights the significance of temporal and seasonal relationships of aridity and biophysical indicators in dryland ecosystems, informing region-specific land and water resource management policies to mitigate hydroclimatic extremes.</div></div>","PeriodicalId":54616,"journal":{"name":"Physics and Chemistry of the Earth","volume":"141 ","pages":"Article 104135"},"PeriodicalIF":4.1,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145227486","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Application of machine learning techniques with empirical wavelet transform and variational mode decomposition for sediment concentration estimation","authors":"Hatice Citakoglu ,&nbsp;Oguz Simsek ,&nbsp;Pınar Spor ,&nbsp;Yunus Emre Gun","doi":"10.1016/j.pce.2025.104136","DOIUrl":"10.1016/j.pce.2025.104136","url":null,"abstract":"<div><div>This study compares the performances of Least-Square Support Vector Regression (LS-SVM), Generalized Additive Model (GAM), Multivariate Adaptive Regression Splines (MARS), Gaussian Process Regression (GPR) methods supported by Empirical Wavelet Transform (EWT) and Variational Mode Decomposition (VMD) preprocessing techniques for estimating sediment concentration at river stations in the Euphrates Basin. In the study, the best performing models are the VMD-GPR (R² = 0.994, RRMSE = 12.70; NSE = 0.993) for 2102 (Murat River-Palu); 2115 (Göksu River-Malpınar) for VMD-MARS (R² = 0.968, RRMSE = 45.99, NSE = 0.961); 2119 (Euphrates River-Kemah Strait) for EWT-MARS method (R² = 0.998, RRMSE = 6.16, NSE = 0.998); 2133 (Munzur Stream-Melekbahçe) for VMD-GPR (R² = 0.976, RRMSE = 28.67, NSE = 0.973); 2164 (Göynük Stream-Çayağzı) for VMD-GPR (R² = 0.982, RRMSE = 25.86, NSE = 0.980); For 2166 (Peri Suyu-Loğmar) EWT-MARS (R² = 0.993, RRMSE = 13.83, NSE = 0.993), for 2176 (Tacik Deresi-Mutu) EWT-GPR (R² = 0.990, RRMSE = 17.48). According to performance criteria, VMD and EWT were more compatible with GPR and MARS machine learning methods. These results reveal that machine learning and artificial intelligence techniques offer a strong alternative for sediment transport estimation. It was observed that the VMD-GPR (three stations) and EWT-MARS models stood out with their low error rates and high accuracy levels. This study's findings provide critical data regarding dam management, hydraulic structures engineering, and basin-based erosion analyses, and they significantly contribute to environmental and hydrological modelling studies.</div></div>","PeriodicalId":54616,"journal":{"name":"Physics and Chemistry of the Earth","volume":"141 ","pages":"Article 104136"},"PeriodicalIF":4.1,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145267137","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Variability and trend analysis in the extreme climatic conditions in Beas River Sub-Basin of the Western Himalayas: A geo-statistical and geospatial approach","authors":"Intejar Ansari ,&nbsp;Mohd Waseem Naikoo ,&nbsp;Md Rejaul Islam ,&nbsp;Mohd Rihan ,&nbsp;Shahfahad ,&nbsp;Swapan Talukdar ,&nbsp;Atiqur Rahman","doi":"10.1016/j.pce.2025.104112","DOIUrl":"10.1016/j.pce.2025.104112","url":null,"abstract":"<div><div>Global warming has triggered environmental and socio-economic impacts, particularly affecting climate-sensitive regions such as Beas River Sub-Basin (BRSB). Limited studies have been done on extreme climatic events (ECE) in BRSB; in such situation detailed analysis of these events is need of the hour. Therefore, 18 climatic extreme indices have been used to assess climate change over the BRSB during 1964–2023. The Pruned Exact Linear Time algorithm has been used to identify change point and to divide the entire period into two period as P1 (1964–1993) and P2 (1994–2023). Trend analysis is assessed using Modified Mann-Kendall test and Theil-Sen's slope estimator. Result shows a decreasing trend of −0.32 mm/year in mean annual precipitation (MAP) and an increasing trend of 0.022 °C/year in Tmax, 0.028 in Tmin and 0.026 in average temperature during 1964–2023. The MAP shows an increasing trend of 8.40 mm/year during P1 and a decreasing trend of −0.93 during P2. Result shows a significant increasing trend of 0.154 days/year in number of consecutive dry days, 0.145 mm/day in Rx1day, and 3.7 days/decade in R10mm during 1964–2023. Also, a significant increasing trend of 0.046 °C/year in TXx and an increasing trend of 0.031 °C/year in TNn during 1964–2023 in BRSB. The increasing atmospheric warming may accelerate extreme events like cloudburst and flash-floods which in turn may trigger other natural hazards such as landslides, droughts and soil erosion and may reduce agricultural productivity. These findings highlight increasing climatic variability in BRSB, emphasizing the need for climate resilience strategies to mitigate the impacts of ECE.</div></div>","PeriodicalId":54616,"journal":{"name":"Physics and Chemistry of the Earth","volume":"141 ","pages":"Article 104112"},"PeriodicalIF":4.1,"publicationDate":"2025-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145105132","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Tectonically-subsidized shallow-marine Cretaceous gas-bearing stratigraphic traps, shelf-slope basin, NW-Arabian Sea: Seismic attributes and broadband porosity-constrained seismic acoustic impedance variability dynamical reservoir simulations","authors":"Muhammad Tayyab Naseer","doi":"10.1016/j.pce.2025.104109","DOIUrl":"10.1016/j.pce.2025.104109","url":null,"abstract":"&lt;div&gt;&lt;div&gt;Quantitative inverted reservoir simulations-based seismic reservoir characterizations facilitate accurate imaging of stratigraphic traps, e.g., incised-valleys infills (IVFs) of Lowstands systems tract (LST). These systems are sourced by fluvial channel sandstone bodies (CH) and meandering point bars (PBARS), which are developed during sea-level standstill along the parallel (P) and divergent (D) seismic reflection configurations (SRF). From the well control points, poor frequency seismic and well logs create hurdles to quantifying the seismic stratigraphic and sedimentological constraints. These constraints are comprised of lithology-impedance contrasts for paleo-erosional and depositional sediments, paleo-dense fracture networks, inclination of stratigraphic traps, and lateral changes in thicknesses of thin-bedded prograding parasequence sets (PPS) and aggrading parasequence sets (APS). Accurate prediction of these constraints may lead to locating direct hydrocarbon indicators (DHI). During the development of IVFs, there are also varieties of SRFs, which serve as the key constituents for developing petroleum. These SRFs are not resolvable at the full-spectrum seismic due to sub-seismic deficiency of poor seismic frequency resolution. These full-spectrum seismic provide poor indicators for sources of sedimentary influxes, which are restricted to predicting source-reservoir and basins' configurations. These implications are not feasible to predict using full-spectrum seismic and well-log data due to the poor resolution of subsurface systems. Consequently, this study utilizes state-of-the-art 29 Hz average energy waveforms and broadband porosity-constrained seismic acoustic impedance variability dynamical reservoir simulations to quantify the Cretaceous system of Northwest Onshore, Arabian Sea. The 29 Hz waveform could image 15–18 m thick sandstone-filled channels inside IVFs. However, this attribute failed to predict the pore spaces due to tuning effects. Average energy-based dynamical simulations at (R) 2 = 0.73 have simulated 24–62 m thick depositional and 17–18 m thick erosional facies from 25 % seismic-based porosities (Ps). ∼ 45 m thick en-echelon architecture was also resolved and simulated by dynamical simulations at 10 % Ps inside the IVFs. Yet, the 29 Hz waveform-based dynamical simulations show unique seismic stratigraphic and sedimentological expressions of IVFs. This simulation has also simulated lateral changes in the lithology-impedance contrasts from PPS-APS, which indicates that P was a key component for gas generation at the continental shelf of the basin. A 39 m thick P gas-bearing thin-bed trapped CH lens was simulated at 25 % Ps. 25 % Ps also simulated a 21 m thick erosional zone D along the shelf-to-slope location. A continuous shoreline trajectory was simulated along this trapped lens inside dense-fractured networks. This trajectory has generated strong lateral lithology-impedance contrasts for APS-to-PPS along the","PeriodicalId":54616,"journal":{"name":"Physics and Chemistry of the Earth","volume":"141 ","pages":"Article 104109"},"PeriodicalIF":4.1,"publicationDate":"2025-09-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145227357","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Application of Gon's algorithm to monitor productivity using Sentinel-2 Multi-spectral Instrument in Lake Kyoga, Uganda","authors":"John Peter Obubu ,&nbsp;Yoshihiko Inagaki ,&nbsp;Rodgers Makwinja ,&nbsp;Tatsuyuki Sagawa ,&nbsp;Rebecca Walugembe Nambi","doi":"10.1016/j.pce.2025.104070","DOIUrl":"10.1016/j.pce.2025.104070","url":null,"abstract":"<div><div>Lake Kyoga is vulnerable to anthropogenic activities and climatic drivers. It requires regular monitoring due to the potential threat of algal bloom and cyanobacteria. Chlorophyll-a is a proxy parameter that shows the lake's trophic state, hence primary productivity. The objective of this study was to compare Gon's method and ocean color algorithms and select suitable remote sensing techniques to monitor chl-a concentration in water bodies. Google Earth Engine along with Sentinel-2 Multi-Spectral Instrument (MSI) imagery were used to retrieve satellite data. <em>In situ</em>, chl-a data for model calibration and validation was collected from 29 sampling locations in the lake according to the seasons. We calibrated Gon's algorithm and then used Sentinel-2 MSI imagery to produce chl-a maps. We noticed a major difference between the suitability of ocean color and Gons algorithms in estimating chl-a in Lake Kyoga. Ocean color was less accurate because it assumes that the blue-green band ratio linearly responded to chl-a abundance, and this made it suitable for relatively clear waters such as oceans or oligotrophic lakes, not Lake Kyoga. The Gons algorithm was more applicable in turbid productive waters such as Lake Kyoga and estimated chl-a accurately. These results are very important for real-time monitoring of climate-sensitive lakes such as Lake Kyoga, which are also subjected to severe catchment degradation.</div></div>","PeriodicalId":54616,"journal":{"name":"Physics and Chemistry of the Earth","volume":"141 ","pages":"Article 104070"},"PeriodicalIF":4.1,"publicationDate":"2025-09-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145158119","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}