Non-rainy Season Research Articles

Assessing the change in soil water deficit characteristics from grassland to forestland on the Loess Plateau

Soil moisture is an important factor that affects terrestrial ecosystems and biological growth and development, and water deficit is one of the major environmental factors threatening vegetation restoration on the Loess Plateau. The purpose was to identify the change in the soil water deficit characteristics from grassland to forestland on the Loess Plateau. In this study, we measured the soil water storage and deficit in abandoned grassland, shrubland, pioneer forestland and climax forestland along with vegetation succession in situ monitor. The results showed that the soil water content and the soil water storage with natural vegetation recovery from the abandoned grassland to shrubland and forestland showed a gradual declining trend. While on the contrary, the soil water deficit was increasing during succession, it was more severe in the deep soil than in the shallow soil layers. And the soil water deficit in July and September of the rainy season as well as that the vigorous growing period of plants was more serious than that in May and November, which are in the non-rainy season on the Chinese Loess Plateau. The vegetation types and soil depth were the key factors affecting the soil water deficiency status in the process of vegetation succession. Water-saving measures should be taken during the vigorous growing period of plants especially for those forest with natural restoration ages >50a on the Loess Plateau. The results could have great potential in the sustainable development of forestry and provide a theoretical basis for effective water management and reasonable vegetation restoration in semiarid loess regions.

Mangrove snail diversity as a tool for biomonitoring the mangrove based coastal habitats

Mangrove forests play a pivotal role in supporting mangrove associated snails by offering essential functions such as breeding grounds, nursery areas, food sources, and protection from predators. They play a particularly important role in nutrient cycling within mangrove ecosystems. Despite their significance, there has been a lack of studies conducted in Sri Lanka to explore the diversity of mangrove snails. Thus, the objective of this study was to assess the significance of snail species diversity in mangrove ecosystems on the western coast of Kandakuliya, Kalpitiya, Sri Lanka. Five sites were selected using purposive sampling technique at each location, and the sampling was conducted during low tide in daylight hours in both the non-rainy (February) and rainy (September) seasons of 2023. Transects (30 m) were established at each location, with six 1 m² quadrats placed along each transect at 5 m intervals as replicates. The study identified six snail species from three families, with Pirenella cingulata being the most widely distributed across all sites and exhibiting the highest abundance at site 3. Temporally, Pirenella cingulata displayed the highest number of individuals in both the rainy and dry seasons. Diversity indices indicated the highest values at site 1 for the Shannon-Wiener index (H´=1.14), site 5 for Pielou's evenness index (J=0.96), and site 1 for Simpson's diversity index (D=0.67). Pirenella cingulata recorded the highest total abundance at 85,840 individuals. Variations in these findings may be attributed to water quality factors such as temperature and dissolved oxygen, as well as mangrove dominance and climatic conditions. The study suggests that incorporation of environmental parameters could support to draw a more comprehensive understanding of the correlation of dynamics of environmental variables for mangrove snail population changes.

Evaluation of the Effect of Agricultural Return Flow on Water Quality, Water Quantity and Aquatic Ecology in Downstream Rivers

Agricultural water serves various functions, including public interest purposes, beyond its primary role in agricultural production. In order to evaluate the various public interest purposes of agricultural water, a quantified study of the effect of agricultural water on river flow, water quality, and aquatic ecosystems is needed. Therefore, this study quantified the impact of agricultural water on the environmental and ecological maintenance function of downstream rivers, taking into account the return flow of agricultural water in rural areas. To this end, first, the effect of agricultural return flow on river maintenance function was evaluated by comparing the return flow quantity calculated using the reservoir supply data with the simulated river flow rate through the SWAT model. Second, the effect of the agricultural return flow on the downstream river environmental ecological function was analyzed using the optimal flow rate results calculated through the PHABSIM model. The lastly, the effect of agricultural water by farming period on the water quality of downstream rivers was analyzed. As a result of the analysis, it was found that the return flow of agricultural water had a large effect on the river flow rate in the case of the non-rainy season, but the optimal ecological flow rate was not satisfied. In the case of river water quality, it was confirmed that the effect of agricultural water (mainly considered as a pollutant) was not significant, except for the drainage duration of rice paddies. Therefore, it can be understood that agricultural water is not only used for the purpose of production but can also have a positive impact on the aquatic ecology of downstream rivers.

Microplastic contamination in urban aquatic environments: Occurrence characteristics in urban streams and stormwater runoff from urban surfaces

This study investigates microplastics in urban environments, focusing on their abundance, types, and relationships with hydrological parameters. Microplastic analyses encompassed two steps: (1) examining urban streams including discharges from a wastewater treatment plant (WWTP) during non-rainy seasons, and (2) analyzing stormwater runoff from urban surfaces for microplastic content during rainy seasons. In urban streams, WWTP discharge exhibited higher microplastic concentrations compared to other streams, indicating WWTP discharge is a dominant source of microplastic pollution. The most prevalent microplastics detected were polypropylene, polyethylene, and their copolymer, although a variety of other types were also found. Concentrations of microplastics were notably influenced by specific urban land uses, as evidenced by a strong correlation (0.95) between microplastic concentrations and areas characterized by industrial and transportation activities. During rainy seasons, microplastics followed the pattern of stormwater runoff, but the highest concentrations, significantly exceeding those in urban streams, were observed before the peak runoff. These maximum concentrations and their timing of occurrence were linked to antecedent dry days, rain intensity, and runoff rate, showing significant statistical correlations. Regardless of their sizes, a diverse range of microplastic types was identified in these conditions, with no consistent pattern across different rain events. This highlights the complex nature of urban microplastic pollution. This study reveals that aquatic ecosystems are significantly affected by two primary factors: (1) the consistent contribution of microplastics from WWTP discharges, and (2) the short-term, but severe, impacts of microplastic pollution associated with stormwater runoff. Furthermore, it suggests the development of alternative strategies to mitigate microplastic pollution in aquatic ecosystems, informed by the findings on the characteristics of microplastics in urban environments. This research underscores the urgent need for integrated urban environmental management strategies, paving the way for future studies to further explore and address the multifaceted challenges posed by microplastic pollution in aquatic ecosystems.

Evolution of water quality in rainwater harvesting systems during long-term storage in non-rainy seasons

The development of rainwater utilization strategies has relied on rainwater harvesting (RWH) systems for centuries to alleviate the pressure on water resources. However, there are still significant knowledge gaps regarding the changes in water quality in RWH systems during long-term storage in non-rainy seasons. This study evaluated the water quality processes in RWH systems through static rainwater storage experiments for approximately 60 days. The results revealed that nutrients in rainwater accumulated in sediment during storage. Disturbance and redox conditions at the rainwater-sediment interface contribute to the release of sedimentary facies materials. The rainwater showed distinct DO stratification, with the biochemical reactions of sedimentary facies being the primary factor driving oxygen consumption. ORP and turbidity showed positive correlations with COD (r = 0.582; 0.572), TOC (r = 0.678; 0.681), TN (r = 0.452; 0.439), and NH4+-N (r = 0.502; 0.553) (P < 0.05). The regulation of water quality and extension of the usage cycle were identified as critical factors influenced by DO. In addition, bacteria share similar ecological niche preferences. These findings provide scientific evidence for the high-quality reuse of rainwater in decentralized RWH systems during long-term storage in non-rainy seasons.

A global turbulence model shows excellent atmospheric optical turbulence conditions over the Ethiopian plateau during non-rainy season

ABSTRACT A worldwide search is currently being conducted to determine the most appropriate sites for the next generation of large optical and infrared telescopes. Here, we report a global map of atmospheric optical turbulence-associated parameter (atmospheric coherence length) based on the fifth generation of European Centre for Medium Range Weather Forecasts re-analysis data set and results for atmospheric coherence lengths at European Southern Observatory and Tibetan Plateau locations (all at mid-latitudes). These confirm the accuracy of the global atmospheric optical turbulence model, but also the simulation result reveals that an excellent atmospheric calm site exist at the Ethiopian Plateau (at a latitude of ∼10°N) outside of the rainy season. The Ethiopian Plateau is the highest plateau in Africa, known as the ‘Roof of Africa’, with an average elevation of over 2500 m, and thus potentially provides good opportunities for astronomy and astrophysics. The median atmospheric coherence length at the Ethiopian Plateau was 17.7 cm and approximately 75 per cent of the time above 15.6 cm for dry conditions, indicating a very calm atmosphere. Although favourable atmospheric turbulence conditions at the Ethiopian Plateau were found from the global turbulence model, due to the complete lack of infrastructure it has never been visited, meaning that additional validation experiments are required.

Spatiotemporal Characteristics of Tropical Cyclone Precipitation in Guangdong Province, China, from 1961 to 2020

Tropical cyclones (TCs) are often accompanied by heavy precipitation, which may lead to natural disasters and a serious threat to life and property. However, they also provide indispensable water resources. Studying the temporal and spatial characteristics of TC precipitation is of great importance for TC precipitation forecasting, TC disaster mitigation, and water resource utilization. Guangdong is one of the most frequently and severely TC-affected provinces in China. Due to the different methods used to identify TC precipitation, the conclusions offered by the existing studies are often inconsistent. Moreover, their analyses of the spatiotemporal characteristics of TC precipitation in Guangdong are not sufficiently thorough. In this study, we first selected the historical TCs that affected Guangdong from 1961 to 2020, using an objective separation method for TC wind and rain, based on the observation data from 86 national meteorological stations in Guangdong Province. From these observations covering the past 60 years, the temporal and spatial variations in TC precipitation in Guangdong for four different periods, namely the first rainy season (FRS), the second rainy season (SRS), the non-rainy season (NRS), and over the whole year (WY), were then explored using statistical analysis and multiple cluster methods. The results show that TC frequencies in the four periods all showed a decreasing trend. TC precipitation also showed a decreasing trend in the SRS and NRS, as well as for the WY, but showed a slightly increasing trend in the FRS. Both TC frequency and TC precipitation showed an apparent inter-annual fluctuation and a quasi-periodic pattern. The spatial distribution of TC precipitation in the four periods all showed a decreasing trend from the coastal to the inland stations, but the western coastal areas had higher TC precipitation values than the eastern coastal areas for the SRS, NRS, and WY periods. The spatial variations of TC precipitation in Guangdong in the four periods of the last six decades were quite similar, exhibiting three primary spatial modes and six patterns. Among them, the spatial distribution of TC precipitation being less than normal across the whole province is the most common pattern. The 86 stations can be classified into six groups when using the spatial clustering method and into four groups when using the time-series clustering method. Stations with higher TC precipitation and large inter-annual fluctuations are often distributed in the coastal areas, while stations with less precipitation and small inter-annual fluctuations are distributed in inland areas. However, the primary areas that are affected by TCs may vary in the different periods.

Study of polycyclic aromatic hydrocarbons accumulation in bioretention facilities and its influence on microbial community structure.

Bioretention facilities are one of the most widely used measures for urban stormwater control and utilization. In this study, the accumulation characteristics of polycyclic aromatic hydrocarbons (PAHs) in bioretention facilities and the effects of PAHs on the structure of microbial communities were explored by combining on-site monitoring and water distribution simulation experiments. The correlation between pollutant accumulation and dominant microorganisms in the bioretention systems was also clarified. The results showed that all 16 priority PAHs were detected in the bioretention facilities in the sponge city pilot area. The PAH concentrations in the soil during the non-rainy season were higher than those in the rainy season and medium- and high-ring PAHs dominated. PAHs in the study area were mainly derived from coal and biomass combustion. The potential carcinogenic risk of PAHs accumulated in the bioretention facilities in the study area was low. The microbial diversity during the non-rainy season was greater than that during the rainy season. Firmicutes, Bacteroidetes, Bacteroides, and Massilia were strongly correlated with naphthalene (NAP), pyrene (PYR), fluoranthene (FLT), and benzo[a]pyrene (BaP). According to the results of the small-scale water distribution test, the addition of PAHs had little effect on the decline in water quantity, and there was no significant regularity in the reduction of water quality including TP, NH4+-N, NO3-N, and TN. The addition of PAHs had a significant effect on the microbial community structure and an inhibitory effect on enzyme activity.

Phytoremediation Capacity of Water Hyacinth (Eichhornia crassipes) as a Nature-Based Solution for Contaminants and Physicochemical Characterization of Lake Water

Water hyacinth (Eichhornia crassipes) is a potential accumulator of water pollutants in aquatic ecosystems, and its presence in water systems can affect water quality. This study used different field measurements and laboratory tests of lake water to determine the impact of water hyacinth phytoremediation capacity. A total of eight sampling stations were used for the two lakes: Lake Koka and Lake Ziway, Ethiopia. Sampling stations were selected from sites infested with water hyacinth (low, medium, and high) and non-water hyacinth aquatic plants during wet or rainy and dry or non-rainy seasons to compare the effects of plants on water quality in the two lakes. All the sampled stations had various human interventions. The water samples were tested for the selected physico-chemical properties, namely, phosphate, nitrate, pH, electrical conductivity (EC), the five-day biological oxygen demand (BOD5), water temperature, and heavy metals (Chromium (Cr), Lead (Pb), Cadmium (Cd), Zinc (Zn), and Copper (Cu)). These water quality variables were compared by means of ANOVA. Despite the chemical oxygen demand (COD) of Lake Ziway, this study found no significant (p &gt; 0.05) variation in the concentrations of Cu, EC, pH and water temperature between wet and dry seasons in either lake. Variations in Zn concentration and other physico-chemical parameters (EC, BOD5, COD, nitrate, phosphate) between low, medium, and high levels of water hyacinth were significant in both lakes (p &lt; 0.05). Water hyacinth has shown significant phytoremediation nature during wet and dry seasons. The lowest average heavy metal, phosphate, and nitrate concentrations; and significant pH and temperature variations were observed in Lakes Koka and Lake Ziway, among water hyacinth and other grass-infested sites. These findings suggest water hyacinth plant as a promising nature-based solution for removing undesirable chemicals from contaminated water bodies.

Understanding Multiple Stressors Which Degrade Antisoiling Coatings: Combined Effect of Rain, Abrasion, and UV Radiation

Antisoiling coatings (ASCs) are nano or microlayer coatings which reduce the settlement of dust on the surface of the PV module and are extensively investigated as a dust mitigation strategy. Since the coating is applied on the outer surface of the PV module, they are exposed to various environmental stressors, and the durability of these coatings is essential. Various studies have reported the effect of individual stressors that degrade ASCs. However, there are very few reports on the impact of the combination of stressors relevant to outdoor field conditions. In this article, we investigate the impact of the combination of the following stressors that degrade ASCs: 1) the combination of the impact of raindrops and acidic water, 2) the combination of UV radiation, the impact of raindrops, and acidic water, and 3) the combination of abrasion, UV radiation, the impact of raindrops and acidic water. The key takeaways from this study are 1) coating life reduced by 21× (average of all coatings) when exposed to the rainy season compared with those exposed to the nonrainy season. 2) All coated samples show lower coating life varying from 10× to 48× when exposed to the impact of raindrops with pH 7 water than those exposed to water immersion/water contact test with pH 7 water. This indicates that, during a rain event, the impact of raindrops hitting the coated surface causes more significant damage than water contact. This study shows that coatings A, B, C, and D are unreliable for long-term use in warm and humid climate zones, considering 25-year module lifetime. However, other chemistries of hydrophobic and hydrophilic solutions could be effective if they exhibit long-term reliability.

Characterizing groundwater and surface water interaction using geological, environmental tracers (222Rn, EC, δ18O, and δ2H) and baseflow index methods for part of the Upper Awash and the adjacent Blue Nile Basin, Ethiopia

Characterization of groundwater-surface water interaction using a combined approach of geological, environmental tracers (222Rn, EC, δ18O, and δ2H) and baseflow index in a complex geological environment was carried out for part of the Upper Awash and adjacent Blue Nile Basins. In this work, total measurements of 59 water samples were used (52 from different reaches of main Rivers and tributaries, 4 from springs, and 3 from boreholes) for 222Rn analysis in dry and wet seasons, along with recent 8–20 years of daily stream flow records from 11-gauge stations. For sub-surface inference, regional geological structures and lineament density zones were determined using Kriging interpolation techniques. 222Rn values for the river and streams show 2.7–468 Bq/m3 during the rainy season and 17.1–1467 Bq/m3 for the non-rainy season. The credible justification related to moderate to high seasonal 222Rn values (100–400 Bq/m3) in the upstream parts of the two Basins, including areas falling along the surface water divide between the two adjacent Basins, shows a link between groundwater and surface water systems. In the same area, a very high mean annual baseflow index (BFI >0.5) is dominantly associated with high lineament density (0.9 < LD < 3.0), regional faults, and geologic units of highly permeable scoriaceous basalt, rift basalt, and fractured ignimbrite units. Relatively, low 222Rn (<100 Bq/m3) in both seasons and low baseflow index (BFI <0.35) values mainly in the central part of the Upper Awash basin are attributed to existing impervious superficial deposits (alluvial, tuff and ash). This, in turn, shows the poor connection between the groundwater and surface water systems in the central plain part of the Upper Awash Basin and, as also evidenced by the storage of floodwater for an extended time after the end of the rainy season, prove poor connectivity between groundwater and surface water systems. The very high 222Rn (400–1467 Bq/m3) with varied mean annual baseflow index (0.35 < BFI <0.5) at different stations in the extreme southern and southeastern parts of the Upper Awash Basin show Awash River is gaining from the aquifer system through highly fractured basalt and fractured ignimbrite geologic units. Evidence from analysis of measured electrical conductivity and stable isotopes (δ18O, δ2H) generally agree with the observed 222Rn value and baseflow analysis.

Spatiotemporal analysis of land surface temperature owing to NDVI: A case study of Vadodara District, Gujarat

The expeditious extension of LULC in the name of development is the root cause of global warming. Replacement of natural resources due to the expansion of manmade erections is accountable for the increase in LST of Earth’s topography. The impression of change in LULC is reflected in LST. To seize the rising temperature, the lamentation of a new plan of action for urbanization is of utmost requisite. This paper examines the change in LULC and its spatiotemporal impact on LST in Vadodara, which is situated on the bank of river Vishmamitri river. Vadodara an arid region has three main seasons and these are summer, monsoon, and winter. The climate is characterized by hot summer and dryness in the non-rainy seasons. May is the hottest month while January is the coldest month. The annual rainfall of the district is 475.2 mm. Hence, to analyze we used multi-spectral and multi thermal Landsat TM and ETM+ satellite images to monitor the evaluation of LULC and its impact on LST from 2001(pre-monsoon) to 2021(pre- monsoon). The study explores to what extent observed LST can be examined by vegetation cover measured through NDVI from2001 to 2021. To achieve this an analysis of co-relation is performed between LULC and LST and by using spectral indices comprising NDVI with the help of software like ArcGIS 10.2 and Erdas Imagine 2014. It had been observed that a considerable increase in LST in Vadodara was 58.338°C (Max) and 21.9014°C (Min) in 2001(pre-monsoon) to 60.844 °C (Max) and 24.6784 °C (Min) in 2021(pre-monsoon) which is just about 2°C increase in Max and 3 degrees increase in Min for LST in past 20 years. It was also observed that there is an inverse relationship between LST and NDVI. The value of NDVI is observed that change from 0.380711(H) and -0.59322(L) in 2001 to 0.551(H) to -0.351193(L)in 2021. Moreover, SMI places a vital role to investigate and verify the relation between LST and NDVI. Henceforth, to verify SMI was also calculated and it was noticed that places with high LST value and low NDVI value contained less soil moisture and places with less LST value and high NDVI values contained more soil moisture. Thus, it can be concluded that, if urban planners and decision-makers implement suitable land-use strategies then Earth’s topography can be protected from adverse effects of urban heat by planting adequate and appropriate trees in bare soil and beside the impervious areas, thus the expansion of UHI can also be controlled. Moreover, with the help of SMI values, it will also be beneficial for the agricultural sector.

Refined Zoning of Landslide Susceptibility: A Case Study in Enshi County, Hubei, China

At present, landslide susceptibility assessment (LSA) based on the characteristics of landslides in different areas is an effective prevention measure for landslide management. In Enshi County, China, the landslides are mainly triggered by high-intensity rainfall, which causes a large number of casualties and economic losses every year. In order to effectively control the landslide occurrence in Enshi County and mitigate the damages caused by the landslide. In this study, eight indicators were selected as assessment indicators for LSA in Enshi County. The analytic hierarchy process (AHP) model, information value (IV) model and analytic hierarchy process-information value (AHP-IV) model were, respectively, applied to assess the landslide distribution of landslides in the rainy season (RS) and non-rainy season (NRS). Based on the three models, the study area was classified into five levels of landslide susceptibility, including very high susceptibility, high susceptibility, medium susceptibility, low susceptibility, and very low susceptibility. The receiver operating characteristic (ROC) curve was applied to verify the model accuracy. The results showed that the AHP-IV model (ROC = 0.7716) was more suitable in RS, and the IV model (ROC = 0.8237) was the most appropriate model in NRS. Finally, combined with the results of landslide susceptibility in RS and NRS, an integrated landslide susceptibility map was proposed, involving year-round high susceptibility, RS high susceptibility, NRS high susceptibility and year-round low susceptibility. The integrated landslide susceptibility results provide a more detailed division in terms of the different time periods in a year, which is beneficial for the government to efficiently allocate landslide management funds and propose effective landslide management strategies. Additionally, the focused arrangement of monitoring works in landslide-prone areas enable collect landslide information efficiently, which is helpful for the subsequent landslide preventive management.

Towards a novel high-spatial-resolution satellite rainfall product from C-band SAR Sentinel-1 over Central South Korea based on a bottom-up approach

ABSTRACT Finer spatial resolution (roughly 1 km) of terrestrial rainfall is necessary for urban hydrology and microscale agriculture demands but still limited in various ‘top-down’ satellite rainfall products (SRPs). This study aims to evaluate the potential application of an emerged ‘bottom-up’ approach, the parameterized SM2RAIN model, to the C-band Synthetic Aperture Radar Sentinel-1 (S1) satellites for a high-spatial-resolution SRP (SM2RAIN-S1, 0.01º/6-day) over Central South Korea. By comparing its performance with the Integrated Multi-satellitE Retrieval for Global Precipitation Measurement (IMERG) Early Run product at a similar resolution against a common reanalysis rainfall product and rain gauges network during a 1-year period, we explore whether this novel bottom-up SRP can add improvements to the conventional top-down SRP regarding differences in climate areas (coast and inland), vegetation covers (cropland and mixed forest), and seasonality (rainy and non-rainy seasons). The SM2RAIN-S1 demonstrates its feasibility in capturing general spatiotemporal rainfall patterns in the study area compared to other rainfall products; however, noises associated with the S1 images still occurred. For the comparison over climate-vegetation areas, the extended triple collocation revealed that the SM2RAIN-S1 is relatively superior to the IMERG mainly over inland and forest regions, suggesting the suitability of 6-day SM2RAIN-S1 data to the stable and lower temporal rainfall variation in such regions, where the IMERG data are limited. The comparison against rain gauge data over rainfall seasons indicated that the SM2RAIN-S1 generally outperformed IMERG for bias and Root-Mean-Square Error, particularly during the rainy season. Moreover, the SM2RAIN-S1 shows its feasibility for moderate and heavy rain detection, while it is less effective in detecting light rain events compared to the IMERG. This study encourages the potential use of the bottom-up SM2RAIN-S1 rainfall product to complement, downscale, and correct the biases in top-down SRPs; together with supporting their integration for improving high spatio-temporal resolution rainfall products.

Machine learning-based assessment of long-term climate variability of Kerala.

Studies on historical patterns of climate variables and climate indices have attained significant importance because of the increasing frequency and severity of extreme events worldwide. While the recent events in the tropical state of Kerala (India) have drawn attention to the catastrophic impacts of extreme rainfall events leading to landslides and loss of human lives, a comprehensive and long-term spatiotemporal assessment of climate variables is still lacking. This study investigates the long-term trend analysis (119years) of climate variables at 5% significance level over the state using gridded datasets of daily rainfall (0.25° × 0.25° spatial resolution) and temperature (1° × 1° spatial resolution) at annual and seasonal scales (south-west monsoon, north-east monsoon, winter and summer). Five trend analysis techniques including the Mann-Kendall test (MK), three modified Mann-Kendall tests and innovative trend analysis (ITA) test were performed in the study. It is evident from the trend analysis results that more than 83% of grid points were showing negative trends in annual and south-west monsoon season rainfall series (at a mean rate of 39.70mm and 28.30mm per decade respectively). All the trend analysis tests identified statistically significant increasing trends in mean and maximum temperature at annual and seasonal scales (0.10 to 0.20°C/decade) for all grids. The K-means clustering algorithm delineated 59 grid points into five clusters for annual rainfall, illustrating a clear geographical pattern over the study area. There is a clear gradient in rainfall distribution and concentration inside the state at annual as well as seasonal scales. The majority of annual rainfall is concentrated in a few months of the year. That may lead the state vulnerable to water scarcity in non-rainy seasons.

Changes in the Dissolved Organic Matter Characteristics Released from Sediment According to Precipitation in the Namhan River with Weirs: A Laboratory Experiment.

In this study, changes in the properties of dissolved organic matter (DOM) released from sediments into water layers were investigated. To analyze the spatial and temporal variation in dissolved organic carbon (DOC), sediment and bottom water samples were collected upstream of the Gangcheon, Yeoju, and Ipo weirs of the Namhan River during the rainy and non-rainy seasons. The initial DOC was correlated with precipitation (R2 = 0.295, p = 0.034) and residence time (R2 = 0.275, p = 0.040). The change in the bottom water DOC concentration resulted from the DOC released from the sediments, which may cause water quality issues in the bottom water. The fluorescence analysis revealed that the DOM contained higher levels of hydrophilic and low-molecular-weight (LMW) organic matter in the non-rainy season and higher levels of hydrophobic and high-molecular-weight (HMW) organic matter in the rainy season. Since the Namhan River is the main resource of drinking water for the Seoul metropolitan area, our results can help to optimize the drinking water treatment process by reflecting the DOM characteristics that vary with the seasons. Furthermore, the statistical analysis confirmed that the nutrient content of pore-water and sediment can be used to estimate the DOM release rate from the sediment to the water layer. The results of this study provide a better understanding of DOM movement in aquatic ecosystems and the influences of rainfall on the water quality of the surface waterbody.

Spatial Distribution and Influential Factors of Nutrients in Rivers of a Typical Mountainous City: A Case Study of the Qingshuixi River in Chongqing

Surface water pollution seriously restricts the development of the city and results in the citizens yearning for a better life. Mountainous cities have their own characteristics in surface water environment and pollution compared with those of plain cities due to their unique topography. In August and October 2019, surface water and sediments were collected in a typical river (Qingshuixi River) in the main urban area of Chongqing. These samples were analyzed for nutrients such as carbon, nitrogen, and phosphorus as well as other basic physicochemical indicators. The results showed that the surface water of the Qingshuixi River was inferior to Category V at present, and it was also at a serious pollution level according to the comprehensive pollution index evaluation system. Among all the water quality indices, NH4+ and TP showed the most serious pollution. The tributaries of the Qingshuixi River exhibited higher surface water quality than that of the main stream, and the water quality during the rainfall season was better than that during the non-rainy season. Pollution sources, tailwater/tributary inflow, and river self-purification capacity determined the spatial distribution of nutrients in the surface water of the mainstream of the Qingshuixi River. Point sources such as the direct discharge of source sewage and pollution overflow in the middle and lower reaches were the most important sources of surface water pollution in the mainstream of the Qingshuixi River. Non-point source pollution had a limited impact on water quality. The "sink" or "source" role transformation of river sediments would occur under different water volume conditions in the river, reflecting the complexity of endogenous pollution. Surface water quality of the main stream showed a gradual improvement tendency along the downstream due to the dilution of the tail water/tributary inflow and the increased self-purification capability of the surface water in the mountainous rivers due to the increased DO content. To summarize, this study suggests that the water environment of the Qingshuixi River should be improved in comprehensive ways, which might be reducing the input of point source pollution by the deployment of the municipal pipe network in key areas, upgrading the sewage treatment plants to decrease pollutant concentrations or fluxes or channel dredging at the reaches with low DO content, etc.

Performance comparison of mono and polycrystalline silicon solar photovoltaic modules under tropical wet and dry climatic conditions in east-central India

Abstract This work focuses on the performance comparison of monocrystalline and polycrystalline Si solar photovoltaic (SPV) modules under tropical wet and dry climatic conditions in east-central India (21.16° N 81.65° E, Raipur, Chhattisgarh). This study would help to select the SPV module for system installation in the east-central part of the country. For comparative analysis, we used performance ratio (PR) and efficiency as figures of merit. The plane-of-array (POA) irradiance was used to determine the efficiency of the modules. The decomposition and transposition models calculated the POA values from the measured global horizontal irradiance. The data were analysed systematically for 6 months in the non-rainy season, from October 2020 to March 2021. Special attention was given to solar irradiance, ambient temperature and module temperature—the parameters that affect the performance of PV modules. The month of October showed the highest variation in irradiance and temperature. The highest average module temperatures (51–52°C) were observed in October–November, while the lowest average module temperatures (34°C for mono-Si and 36°C for poly-Si) were observed in December. The highest value of average monthly POA irradiance (568 W/m2) was observed in February and the lowest (483 W/m2) in December. The results showed that the monocrystalline SPV module performed better than the polycrystalline module under all weather conditions. The maximum observed values of mono-Si and poly-Si panel PRs were 0.89 and 0.86, respectively, in December. Thermal losses were higher with higher module temperatures in October and November, and lower in December due to lower temperatures. The energy yield was calculated from the measured data and compared with PVSyst simulations.

CLOUD ATTENUATION AT Ka, Q AND W BANDS BASED ON RADIOSOUNDINGS DURING RAINY AND NON-RAINY SEASONS IN CENTRAL ANDES: A STUDY IN EL ALTO, BOLIVIA

Cloud attenuation in satellite communication systems becomes a relevant issue as the frequency increases, and thus, it has to be taken into account when link availability is being calculated. This atmospheric impairment is a variable atmospheric phenomenon whose characterization has to be done not only on a yearly-basis but also on a seasonal and monthly basis. In the present paper, cloud attenuation statistics are reported at 20 GHz, 40 GHz and 75 GHz during rainy and non-rainy seasons in El Alto, Bolivia, at 4065 m of altitude, using 3 years of radiosoundings (2016-2019). Cloud detection models have been used for the calculations, including Salonen, Salonen08, Decker and CldMod models, and results obtained are compared to those given by the global model of the ITU-R Rec. P.840. The results lead to conclude that zenith cloud attenuation during rainy season can reach maximum values between 0.15 and 0.45 dB (20 GHz), 0.55 and 1.5 dB (40 GHz), and 1.3 and 3.9 dB (75 GHz) depending on the model to be used. In comparison, during non-rainy season these values vary between 0.08 and 0.33 dB (20 GHz), 0.26 and 1.1 dB (40 GHz), and 0.62 and 2.6 dB (75 GHz). On the other hand, statistics based on CldMod model and, in a less extent, Decker model are close to the ones obtained using the ITU-R global model. These observations could open the possibility of further studies assessing the reliability of meteorological parameters in digital maps at high altitude sites, because these data are used in global propagation models.

Active Landslides Detection in Zhouqu County, Gansu Province Using InSAR Technology

Objectives Zhouqu County in Gansu Province is highly prone to landslides. On July 12, 2018, a landslide blocked the Bailong River near the county, posing a serious threat to the life and property of local residents and the safety of infrastructure. The early identification of potential landslides around this area is of great significance to protect the life and property of local residents and the security of its infrastructure. Methods Firstly, small baseline subset interferometry technology (SBAS-InSAR) was adopted to identify the potential active landslides in the surrounding area of Zhouqu County, with the Sentinel-1A satellite ascending and descending images from October 2017 to December 2018. Then, a combination of optical remote sensing image interpretation and field investigation is used to determine and identify potential landslides. The visual interpretation method can be used to identify landslides that have occurred or are occurring on the optical images. The field investigation was used to verify the landslide results identified by InSAR and optical imagery to increase the effectiveness and accuracy of landslide detection. Results A total of 23 active landslides were detected in the study area, with 16 active landslides detected on the ascending images and 11 on the descending images, with 4 active landslides having valid deformation information detected on both the ascending and descending images. Combined with the visual interpretation of optical remote sensing images and field investigation, the deformation characteristics of 4 typical landslides, including Jiangdingya, Mentouping, Suoertou, and Xieliupo Landslides, were analyzed. It was found that the deformation rates of Jiangdingya, Mentouping, and Xieliupo Landslides were significantly higher during the rainy season than during the non-rainy season, and the Suoertou Landslide did not show a significant increase in the deformation rate during the rainy season but showed fluctuations in the deformation rate during the rainy season. Conclusions The use of single-orbit radar satellite data for landslide detection can easily lead to the missed detection of landslide hazards, and the combined use of ascending and descending radar images can improve the accuracy of landslide detection in steep mountainous terrain. The deformation rates of active landslides in the study area have a good correlation with rainfall. The results can provide supports for the geohazard mitigation and prevention in Zhouqu County. The strategy which combines optical imagery, field investigation, and time-series InSAR can efficiently and accurately detect and monitor landslides over a wide area.