Catchment erosion, channel erosion and sediment transport are connected processes within fluvial system forming a sediment cascade. Studies related to connectivity between a specific source and its multiple sinks within catchment, and rivers, and their multiple impacts have expanded in scope and sophistication during the last two decades, and were recently broadly presented at numerous international conferences and workshops. The International conference on transboundary catchment erosion and pollution problems was held in Belgrade, Serbia, in July 2023. The outcome of this conference as comprehensive literature review on the topic initiated this review which is aimed at classification the functional scheme of soil erosion, channel processes and sediment transport, and their impacts which include natural hazards, river pollution and hydrogeochemistry, catchment management, and hazards prevention, and technologies. We summarize established and emerging papers related to both regional studies on catchment erosion and management, as well as channel processes modelling and hydrogeochemical impact in streams and rivers. Finally, we discuss future directions and challenges to bridge scientific and management gaps by promoting a holistic understanding of river systems and catchment conditions.

The environmental component of Sustainable Development for large regions of the Earth can be assessed through the evaluation of the natural resource potential of the territory. The methodological challenge of such assessments is always determined by the type of operational-territorial unit within which the geodatabase is formed. This article details the possibilities of using the basin approach as such units. This approach is one of the most important in humid climate regions where a river network has been developed. Using the example of the Ob’ river basin in Northern Eurasia, the article illustrates the application of the basin approach to assess the environmental determinants of Sustainable Development. The studies were conducted in three stages: formation of an GIS database of basin geosystems of the Ob’ river basin; creation of a geospatial database on the natural resource potential in the small river basins; selection of criteria and assessment of anthropogenic load on the basin geosystems of the Ob’. A total of 30,738 small river basins were delineated automatically based on GMTED DEM, with a mean area of 66 km2. GIS integrated geoinformation represents the natural and anthropogenic characteristics of river basins. The assessment of the environmental state of the territory should considerthe types and strengths of anthropogenic loads. For this purpose, the integral indicators used, which directly or indirectly reflect anthropogenic impact: population density, road network density, and the percentage of arable land in the total area. The final indicator of anthropogenic load was calculated as a linear combination of specific variables and ranked into six categories. Thematic and complex maps were created, allowing us to identify the natural background in which the geosystems of small river basins are formed and function, as well as the types and strength of anthropogenic loads on the territory.

Torrential flood hazard assessment is always a challenge, especially if the aim is to do it on the level of the whole watershed. When there are no required data available, there are traces in nature, morphological indicators, that show the extent of previous floods, in period longer then instrumental period. Therefore, in this paper we deal with fluvial and slope both erosional and accumulation processes and landforms, which doubtlessly indicate torrential flood prone areas. We have selected eight indicators and grouped them into three segments: erosional process, morphometric characteristics of watershed, and accumulation processes and landforms. Selected indicators serve for fluvial processes determination and therefore could be used for proper water and flood risk management. The research was done in three middle-sized watersheds in Serbia which belong to the Velika Morava River basin, showing that integrative approach is necessary for rational watershed management, meaning for selection of measures for torrential flood hazard mitigation.

River discharge and its variations are often the subject of research from different aspects. This study aims to examine the discharge variability of selected rivers in central Serbia and the northern part of Montenegro, which belong to the Danube River basin (Black Sea Drainage basin). In general, all these rivers have uneven water regimes, a large share of evaporation in the water balance during the year, and very low values in discharges in the summer. In this regard, an analysis of mean annual and monthly discharge changes in ten hydrological stations from nine rivers in the 1961–2020 period was made. By using the t-test, a comparison of two 30-year periods (1961–1990 and 1991–2020) was made to examine if there were significant changes in the discharges. The obtained results indicate that in all rivers, annual discharge decreased in the second period compared to the earlier one, and a statistically significant decrease is recorded in 3 rivers, Lepenica, Lugomir and Lim. Changes in monthly discharges between the two 30-year periods are statistically very significant in the summer period in the selected rivers of Montenegro. In contrast they are not statistically significant in selected rivers of Serbia, with several exceptions in spring and autumn. The obtained results indicate mainly a statistically significant discharge decreasing in the second period, which is primarily correlated with a significant increase in air temperature. As discharge changes influence water resource management, the results obtained in this study are important for decision-makers.

The most recent climate change scenarios indicate an increase in extreme climate events (rainfall) and therefore an increase in soil loss. Strumica River is a tributary of river Struma/Strimon – a transboundary basin in North Macedonia (Strumica), Bulgaria and Greece that flows to the Aegean Sea. Most of the models incorporated in several software packages, use the USLE (Universal Soil Loss Equation). USLE-based models (RUSLE, MUSLE) are designed to model soil loss on gentler slopes and in agricultural areas. Furthermore, the model considers soil removal, but not the mass movement processes. On the other hand, the EPM (Erosion Potential Method by Gavrilovic), considers all soil particles (including rocks and mass movement) as well as all slope topography. The EPM considers the whole basin area. The aim of this research is to assess the differences between the two methods in the case study of the Strumica river basin. The results show differences in the quantities of the produced sediment. On the basin level, according to EPM, the quantity of annual produced sediment is 3.38 m3 ha year-1 while RUSLE depicted an annual soil loss at 1.59 t ha-1year-1. When observing just the agricultural land, according to EPM, the annual produced sediment is 4.22 m3 ha year-1 while according to RUSLE, the annual produced sediment is 2.84 t ha-1year-1. The EPM yields higher quantities because it takes into account the gully erosion and mass movement processes.

The catchments of the reservoirs Spilje and Globocica are positioned in the western part of North Macedonia. These catchments are situated in the higher part of the Drim/Drin catchment which is a transboundary catchment stretching in several countries. The two catchments were mapped for erosion according to the Erosion potential method by Gavrilovic. In order to assess the Erosion potential method, a bathymetric survey was also carried out. The two erosion maps created for the two reservoir catchments show very different results. The catchment of the reservoir Globocica is one of the most preserved catchments in the country from soil erosion point of view with average erosion coefficient of 0.21, specific annual production of erosive sediment is 394 m3 km-2 yr-1, the specific annual transport of erosive sediment is 247 m3 km-2 yr-1 and the annual transport of erosive sediment is 74,543 m3yr-1. On the other hand, the catchment of the reservoir Spilje is one of the most erosive areas in the country, with average erosion coefficient of 0.44, specific annual production of erosive sediment of 776 m3 km-2 yr-1, the specific annual transport of erosive sediment of 541 m3 km-2 yr-1 and annual transport of erosive sediment is 563,154 m3yr-1. The sedimentation of both of the reservoirs was measured only once in 2014 and 2015. The accumulated sediment in Spilje is 36.7 x106 m3 or mean annual intensity of sedimentation is 815,555 m3yr-1. On the other hand, the Globocica reservoir has much lower values for sedimentation, 3.3x106 m3 or mean annual intensity of sedimentation of 67,346 m3 yr-1.

Interdependency between river basin water retention capacity and different types of water erosion is well documented and recognized by researchers and practitioners. Erosion adverse effects on sustainable water and land management from local (catchment/ drainage scale) to river basin level are various and generated by natural and anthropogenic drivers. The solutions and measures to address these issues span across Multilateral Environmental Agreements, sectoral policies and legal framework. Consequently, the effective cooperation among different sectors, stakeholders and decision makers is required from local catchment to transboundary river basin level. Natural water retention measures (NWRM) multi-functionality in addressing water-related challenges by integrating different policy objectives at the river basin scale, increased their relevance identification in river basin management plans. Selected NWRM with medium to high benefits with respect to erosion reduction, sediment delivery, flood risk reduction, etc., are summarized. The main steps in flood risk management, “win-win” measures identification by Tisza countries and NWRM included in the Integrated Tisza River Basin Management Plan (2019) are presented. Well-structured data collection approach for different policies integration instead of underlying differences and discrepancies is a good starting point for the productive shared river basins management and governance. If the implementation of the NWRM have potential downstream cumulative effects on low flow water regime the mechanism for evaluation of potential consequences has to be established and defined.

In high mountain areas, glacial lake outbursts are often the cause of floods and extreme events. Investigation of these events is especially important in the context of ongoing intensive deglaciation and climate change. This study is focused on the monitoring of the Bashkara Glacier Lakes after their outburst on September 1st, 2017, which are located in the most glaciated and populated part of the Central Caucasus of Russia, in the Mt. Elbrus region. Following the incident, the lakes system has transformed into flow-through. However, the lakes system has undergone significant changes and remains unstable and potentially hazardous. In this research, we used remote sensing data and field observations to assess the condition of the Bashkara Lakes. The water level, area and volume of the lakes are unstable. Between 2018 and 2024, the area of Bashkara Lake increased by 32% and volume by 41%, with the level increasing by 3.2 meters. At the same time, Lapa Lake was rapidly shrinking. The area of Lapa Lake in 2018-2024 decreased by 51%, the volume by 66%, and the level decreased by 4.2 meters. In addition to the continuing rise of the water level, the possibility of future rockfalls cannot be excluded, which can trigger a re-outburst. Ephemeral glacier lakes were also discovered, their merging with the main lake can cause a dramatic increase in the lake volume. On the other hand, other factors, such as the decrease in water temperature of Bashkara lake and its flowage, indicate the stability of the lakes system.

Contemporary distributed hydrological models are detailed and mathematically rigorous, but their calibration and testing can be still an issue. Often it is based on the quadratic measure of the calculated and observed hydrographs proximity at one outlet gauge station, typically on the Nash-Sutcliffe model efficiency coefficient (NSE). This approach seems insufficient to calibrate a model with hundreds of spatial elements. This paper presents using a multi-dimensional estimator of modeling quality, being a natural generalization of the traditional NSE but which would aggregate data from several hydrological stations using Principal Component Analysis (PCA). The method was tested on the ECOMAG model developed for a sub-basin (24,400 km2, with 15 gauges) of the Ussuri River in Russia. The results show that the presented version of the multi-dimensional NSE with PCA in calibration of spatially-distributed hydrological models has a number of advantages compared to other methods: the reduced dimensionality without loss of important information, straightforward data analysis and the automated calibration procedure; objective separation of the deterministic signal from the noise, calibration using the “informational kernel” of data, leading to more accurate parameters’ estimates. Additionally, the introduced notion of the “compact” dataset allow to interpret physical-geographical homogeneity of the basins in mathematic manner, which can be valuable for hydrological zoning of the basins, hydrological fields analysis, and structuring the models of large basins. There is no doubt that further development and testing of the proposed methodology is advisable in solving spatial hydrological problems based on distributed models, such as managing a cascade of reservoirs, creating hydrological reanalyses, etc.

The geometry of watercourses shows that they undergo continuous deformation towards a dynamic equilibrium state. Once this is reached, further changes in the bed can be observed, but they are not expected to cause significant deviations from the dynamic equilibrium state. The dynamic equilibrium state will likely change due to significant natural or artificial processes. The main question is what new riverbed geometry or flow conditions (peak water levels) can be expected. In our paper, we investigate the impact of past interventions on the dynamic equilibrium state of the Upper Danube in Hungary. We built a 1D morphodynamic model for the section under study. The model was improved by incorporating the mixed grain composition of the bed and bedload material and considering the backwater effect. The model was parameterised with data from the 19th century, i.e. the natural state. The model allowed us to perform a century-scale study. The model gave accurate results of 13 cm and 3 cm for the incorporation of the interventions and also predicted the backfilling in the studied section. Using the 1D approach, we obtained a model that can study a more extended section, such as a more than 100 km reach. The 1D model can provide a temporal estimate of the impact of each intervention, Such as the installation of wing dam fields and water dams and the elaboration of artificial cutoffs.

The Sefidroud River, the second largest river in Iran, is located in the north. Since the operation of the Sefidroud (Manjil) dam on the said river, about half of the storage volume of the dam has decreased as a result of the accumulation of sediments. The present research, using 516 suspended sediment data from four regional sediment monitoring stations, was conducted between 2013 and 2020 to check the accuracy of single-linear, bi-linear and middle-class sediment rating curves (SRCs) of four sediment monitoring stations as well as Landsat 8 images to estimate suspended sediment concentration (SSC). After drawing the SRCs based on 46 satellite images and SSC data, 70% of samples were used to prepare the regression models of spectral data versus suspended sediment discharge (Qs) and 30% of samples to evaluate the accuracy of SRC and Landsat 8 data. According to results, the middle-class SRCs had the highest coefficient of determination (R2, exponential). Four band ratios B4/B3, B4/B2, B6/B5 and B7/B5 had exponential and power correlation with Qs, with the highest value for the band ratio B4/B3 (R2 = 0.74, exponential). To conclude, the results of the current research showed that the B4/B3 band ratio was more efficient for Qs estimation.

STREAM_2D software package was applied for retrospective and predictive simulations of the Lena River hydraulic and channel changes during ice-free period near the city of Yakutsk. The modelling results indicate significant correspondence of simulated water discharges distribution and water levels with observed one, the model also has captured main erosion and accumulation zones, according to the 2009–2016 years observations. Runoff hydrographs of the ECOMAG runoff model simulations based on the global climate model MIROC-ESM-CHEM data were used as input for the hydrodynamic model with daily time step for two climate scenarios RCP2.6 and RCP8.5.
Comparison of scenario, based on modern hydrographs, and two scenarios, based on climate projections, have shown the changes in the range of channel-forming discharges and their duration. According to the results of 20-year simulation of channel evolution for three scenarios, the position of the main areas of erosion and deposition under scenario RCP2.6 and RCP8.5 retained the same as under actual scenario, but some additional new local areas of erosion can be formed during peak flows near the banks. Erosion can increase by up to 1 - 2 meters and even more in some areas, but the shifting of some large erosion-accumulative forms is slower than according to the scenario, based on the modern hydrographs, due to the reduced duration of channel-forming flood discharges.

The study aimed to determine the levels, spatial and temporal variability of the concentrations, and forms of migration of metals and metalloids in the Pur River basin, which is one of the most important oil and gas producing areas in the north of Western Siberia. The study is based on the results of hydrological and geochemical studies conducted in 2021-2023 during the summer low water and spring flood periods. We found generally low content of dissolved metals and metalloids in water of the Pur River and its tributaries, not exceeding the world average values, except for Fe and Zn. Levels of metals and metalloids in the suspended matter were also lower than the global averages, except for Fe and Mn. Changes in the content of dissolved and suspended forms of metals caused by hydroclimatic factors and anthropogenic impact were determined. Near cities, the maximum concentrations of Zn, Cd, Cu and other metals in suspended matter are 3-5 and more times higher than the baseline values. Analysis of EF values for median contents allowed to identify the association of elements with considerable and high enrichment in suspended matter: Fe, Mn, Sb, As, Cd and Zn. The maximum EF values ranged from 25 to 45, which corresponds to very high degree of enrichment. Three groups of chemical elements were identified on the basis of D,S-analysis.

The selection of a location for the disposal of radioactive waste, used sources and spent nuclear fuel in the Republic of Croatia began to be considered as early as 1988. However, in the last 10 years, intensive activities have been undertaken regarding the selection of this location. One possible location is Čerkezovac in the Trgovska Gora area, which is located in the Una River basin and less than 1 km away from the border with Bosnia and Herzegovina. It is planned to establish a Radioactive Waste Management Center in Čerkezovac, where all spent radioactive sources located at two sites in Croatia, all institutional waste owned by Croatia, as well as low and intermediate level radioactive waste from the Krško Nuclear Power Plant, would be accommodated. According to the ESPOO Convention (Art. 1, paragraph VIII), transboundary impact implies any impact, not exclusively of a global nature, within the jurisdiction of the signatory state caused by a planned activity, whose physical origin is wholly or partially within the jurisdiction of another signatory state. The majority of the influential surface area of the radioactive waste disposal site (assuming a distance of 5 km from the Čerkezovac site in the Trgovska Gora area) is located within the territory of Bosnia and Herzegovina. This influence could have negative implications on the natural values and protected areas in the Una River valley in Bosnia and Herzegovina, as well as the life of the population.
In this paper, based on the analytical-synthetic research approach, the basic physical-geographical characteristics of the Una River basin have been determined. During the analysis, it was concluded that the connection of physical-geographic components within the Una River basin created a series of natural values that formed the basis for the designation of protected areas. This refers to the fluvial and karst landforms that dominate this area, as well as phytogeographic formations, which stand out for their uniqueness and irreplaceability, morphography and morphometry, and the degree of preservation of physical-geographic phenomena and processes. The results of the research can contribute to a better understanding of the potamological characteristics of the Una, its hydrological significance, as well as the need for environmental protection in the context of the possibility of nuclear waste disposal in the border zone of the Una basin. The processing of all parameters relevant to the study and cartographic representation in this paper were performed in the ArcGIS software package.

The disadvantage of the traditional approach to territorial planning of the past years is associated with an underestimation of the essence and multifaceted social brownfields and their importance in the sustainable development of urban areas in post-industrial society. The prospects for the development of the inner space of the city and the quality of life of people largely depend on the presence of brownfields since most of the brownfields can have a negative impact on the environment. This is especially noticeable in large cities and agglomerations. In this paper, we analyze the spatial distribution of brownfields in the largest agglomeration of Russia, comparing their prospects for redevelopment with the analysis of 10 dominant criteria of local priority affecting the transformation of the urban area. The article discusses in detail the reasons for making decisions about the nature of the impact of brownfields and the priority tasks of their elimination: the environmental situation and the economic interests of stakeholders. The study shows that the practice of making decisions on the liquidation of brownfields largely depends on their inclusion in the state register of objects of accumulated environmental damage, which makes it possible to accumulate environmental damage in the near future. However, the entry of accumulated environmental damage into the state register of objects is (1) a practiced procedure because it implies co-financing of the brownfield liquidation project by the federal authorities and (2) an insufficiently objective procedure for assessing the impact (lack of local priority criteria). Based on the conducted research, we believe that the elimination or urbanization of brownfields should be based on the analysis of local priorities in the transformation of urban areas (different from the criteria of modern practice of introducing the state register of brownfields), including the features of the territorial organization of public space, ecological and geographical environment, and public opinion.

The purpose of this research is to model the condition of seawater quality based on Government Regulation No. 22/2021 about «Implementation of Protection and Environmental Management», the results of which can later be used as a basis for reference for the concept of environmental conservation. The research was conducted at the MV Boelongan Nederland shipwreck site, focusing on seawater quality measurements including physical, chemical, and pollutant parameters. Sampling was performed at various locations near the shipwreck and nearby estuaries using purposive sampling. Parameters such as pH, temperature, turbidity, dissolved oxygen (DO), biological oxygen demand (BOD), salinity, and concentrations of pollutants like phenol, polyaromatic hydrocarbons (PAH), and pesticides were measured and analyzed using geographic information system (GIS) tools. Data analysis revealed that despite some variations, seawater quality parameters generally met regulatory standards, supporting marine life and tourism activities. However, localized pollution was observed, particularly near estuary areas, emphasizing the need for targeted conservation efforts. The research results indicate that the estuarine areas experience light pollution due to land-based runoff, which could affect the long-term sustainability of the shipwreck site. However, the overall seawater quality at the shipwreck location remains favorablefor marine tourism and conservation. The findings suggest that a zoning system could be beneficial for managing underwater heritage sites, thereby supporting both environmental preservation and the economic development of the region. Furthermore, the research emphasizesthe potential of shipwrecks as tourism assets, suggesting their role as artificial reefs and underwater museums thatcontributeto visitors’ recreational and educational experiences.

Assessment of urban green infrastructure is a task of strategic planning and tactical implementation of decisions taken in the context of sustainable development of urban territories. One of the directions of such an assessment is to identify instances of land misuse within cities’ public green areas. It reflects the legal fairness of the use of urban green spaces, but currently has a weak scientific justification. Therefore, it is pertinent to develop a methodology for evaluating urban green infrastructure in order to pinpoint areas with inappropriate usage Critical analysis and synthesis allowed us to justify the assessment of the misuse of land within urban green zones as an equal element of the urban green infrastructure assessment system. A geospatial database was created to assess public green spaces. Using the results of remote sensing of territories, as well as the «boxplot» method in combination with the Python programming, the NDVI was calculated, and a classification of vegetation elements and artificial objects located within public green spaces in cities was carried out. Based on the obtained classification categories, a mechanism for identifying «green» areas with misuse of land was proposed, and a list of public green areas with similar violations in St. Petersburg was determined. The practical results of the study include: technology for assessing urban green infrastructure to identify public green spaces with misuse; geospatial databases of public green spaces for St. Petersburg; identified public green spaces with obvious violations of their use, including unauthorized parking, littering, sand dumps, unauthorized placement of industrial, warehouse, retail, transport, or other non-recreational facilities within the boundaries of PGS, vehicle collisions with «green» areas; erroneous inclusion of residential buildings and adjacent courtyards, non-residential facilities, as well as organized parking spaces within PGS’s boundaries.

Environmentally unsafe agricultural use of soil and land resources is caused by the high share of reclaimed land in the Pripyat Polesye region and global climate change. The research aims to evaluate the long-term vulnerability of the soil cover, utilizing the example of a large agricultural enterprise spanning over 9,200 hectares in a zone of hydro-technically drained peat-bog and alluvial soils in the central and terraced floodplain of the Pripyat River (Belarus). The assessment of the degree of vulnerability is expressed on the basis of the genetic characteristics of soils in accordance with the soil-hydrological constants: the moisture content of the capillary fringe rupture and the limiting field capacity. The dynamics of spatial and temporal changes in soils by groups of vulnerability to wind erosion is controlled in geoinformation software based on specialized spectral brightness indices according to satellite data for plant vegetative season. Dependences of the degree of vulnerability on heterogeneity of soil cover structure and intensity of agricultural use of soils by types of land have been established. The obtained patterns can be used to develop adaptive landscape farming systems in the Polesye region and to forecast degradation processes of agricultural lands.

In agricultural mountain regions, changes in weather patterns force people to look for new agricultural activities, shift from agriculture to tourism services, or even leave the mountains. This study discusses the role of Dagestan’s agricultural terraces as a potential resource for mountain people to adapt agricultural activities to climate change, thereby demonstrating the community resilience grounded on local traditional practices. We selected eight mountainous administrative districts of Dagestan as a case study area and tracked the changes of average annual, summer, and winter temperatures and precipitation for different altitudes in 2011–2020 compared to 2000–2010. We also conducted 30 informal exploratory interviews with local farmers and officials (purposive sampling) aiming at revealing common local narratives regarding climate change and its impact on agricultural activities, including the use of terraces. According to our results, respondents perceive the warming and drying of the Dagestan mountains as a growing water scarcity due to decreased precipitation and reduced snow cover, and as an opportunity to expand agricultural activities to higher altitudes. Agricultural terraces are seen as a prime land resource, preventing erosion and conserving soil moisture. Including terraces as a tourist attraction could increase interest in the local landscape and its history and may also indirectly serve to strengthen the resilience of local communities. While climate change may make it difficult to farm in the mountains, tourism becomes an additional source of income for farmers and supports agriculture.

The paper presents the first data on the ratio of gamma-emitting isotopes (137Cs, 152Eu, 154Eu, 60Co) speciation in the floodplain soil and rhizosphere of floodplain plants in the Balchugovskaya channel. This channel is located in the near impact zone of the Krasnoyarsk Mining and Chemical Combine alongside the Yenisei River. The formation of a temporary stream during high floods affects the spatial distribution of isotope specific activities in the soil and rhizosphere of this area. The gross specific activities of isotopes vary in a very wide range. The highest ones are recorded in the lower outlet of the temporary stream (up to 800 Bq kg-1). The procedure of sequential extraction was applied to obtain data on isotope speciation. The hydrological regime characterized by high floods in this section of the Yenisei River, as well as the biological activity of plants, exerts a noticeable influence on the spatial distribution of isotope specific activities and their speciation ratios. Lower percentages or the absence of mobile forms of isotopes in the plant rhizosphere, as compared to the bulk soil, provide evidence for this. In general, isotopes in the soil and rhizosphere tend to accumulate in the organic and residual fractions. There are noticeably different distributions of isotope speciation in central areas and sides of the temporary stream entrance and outlets. The most diverse speciation patterns were observed for 152Eu and 154Eu isotopes, but under different hydrological conditions.

This work studies the variations in daily and seasonal concentrations of surface ozone (O3), and nitrogen oxides (NO and NO 2) as its precursors in Chelyabinsk, a large industrial city in Russia. A monitoring station located outside the zone of influence of large industrial and transport local sources of air pollution was chosen for the research. The research was carried out during 2019, which can also be considered as a “background” period, because in 2020, during the COVID-19 lockdown, there was a decrease in concentrations of precursors. However, in 2022–2024 concentrations of precursors increased due to increased production capacity. Daily O3 variations are characterized by three peaks that correlate with changes in concentrations of nitrogen oxides (NOx) determined by peak loads and emission intensity of thermal power stations. There are two seasonal peaks of surface O3 concentrations. The spring peak in March is caused by natural processes. In March 2019, an advection of an air mass with different properties and gas composition was observed from areas with powerful sources of precursor gases or saturated with O3 from the south (areas in Kazakhstan). During episodes of high O3 levels, Chelyabinsk was located on the crest of a cyclone, in the warm sector, where low-level jets formed. The summer maximum of surface O3 in June was caused by photochemical reactions during anticyclones and prolonged inversions.

Global Geopotential Model (GGM) is a mathematical representation of the Earth’s gravity field and geoid, which is developed to provide accurate information about the variations in the Earth’s gravitational potential across the entire globe. Recently numerous organizations and research centres have developed multi GGMs derived from several types of available gravity and height datasets to estimate orthometric heights from GNSS measurements. In this study, we present an accuracy evaluation and assessment of the nineteen recent and popular GGMS using actual GNSS/levelling points, and gravity anomaly points. The goal of this research is to find the optimum model for the study area which is located in the East Malaysia for further determination of geoid modelling in the regional scale. The selection of these areas basically is due to their renowned for uncontrolled topography and various datums. The results indicate that for geoid undulation, the XGM2019e_2159 with value of 0.195 model is the best fit GGM for the estimation model for East Malaysia. For gravity anomalies, the most reliable GGM for the study area is GO_CONS_GCF_2_DIR_R5 with RMSE of 32.456