Environ. Sci. Proc., 2021, ECWS-5 2021

The landscape dynamics of a wetland are critical for understanding lake ecosystem health and sustainability. This paper characterizes the spatiotemporal dynamics of the different wetland plant communities in the Poyang Lake during 2017–2018 to reveal the spatial distribution pattern of different wetland landscapes. Time-series Sentinel-2 images were used to investigate the spatial-temporal image features variation for different wetland plant communities in the growing season. NDVI, IRECI, backscattering coefficients, and scatter mechanisms were generated from the Sentinel-2 to study the spectral and structure information of the wetland plant communities. SVM and Random Forest were used to classify the time-series Sentinel-2 images. The results showed that NDVI and IRECI were the main factors to decide the accuracy of the map. Additionally, backscatter coefficients, VH polarization and spatial-temporal scatter mechanisms are a good supplement to improve the classification accuracy. Carex and miscanthus are the main plant communities in the Poyang Lake wetland. The landscape of the wetland vegetation partially changed during 2017–2018 because of the high dynamic hydrological changes. The Zizania community is increasing greatly with the decreasing water level. Furthermore, the water level decreasing plays an important role in the acceleration of the swampiness of the Lake wetland. Full article

Water is an important factor in human health and an essential ingredient of living organisms. The increase in population and living standards has led to increased water consumption, consequently causing an increase in wastewater, as well as greater quality impairment. Wastewater treatment of the public mixed drainage system of the city of Čakovec (Croatia) and surrounding suburban settlements is carried out by mechanical and biological procedures, with the final treatment of separated sludge. In this paper, we analyzed the input and output values of annual time series for chemical oxygen demand (COD) on the wastewater treatment plant in 2015 using the RAPS method (Rescaled Adjusted Partial Sums). The results showed that the input series contained more pronounced subseries with respect to their mean values and trends of increase and decrease, respectively. When comparing the input and output subseries, the output subseries does not oscillate to a large extent given that they express the output quality of wastewater. A significant reduction in the output values of the indicators determines the quality treatment of incoming wastewater. Full article

Production of electric energy from rivers by using mini- as well as micro-hydroelectric power plants is a possible solution, especially in rural and isolated areas. Numerous waterways in Croatia and their hydrological and hydrogeological diversity present an opportunity but also a challenge for the construction of hydroelectric power plants. Due to the complexity of the water course hydrology, as well as hydrogeological characteristics, it is very difficult to determine an appropriate flow pattern (amount), which will be used as an input value for the sizing of hydroelectric power plants. Such analysis will be provided for real case studies in Croatia with special regard to present geological media—media with intergranular porosity (river Bednja), karstmedia (river Gornja Dobra), and flysch media (river Mirna). Taking into account different geological media increases the possibility of using the presented methodology on other locations in Croatia, as well across the world. Full article

Green roofs performance is strongly impacted by climatic conditions, design parameters and aging. In particular, the evolution in time of physical and chemical properties may lead to substantial changes in their retention and detention capacity. The growth of the roots, above all, seems to affect the interpretation of the soil water content, a key parameter for GRs retention performance. Generally, Frequency Domain Reflectometry sensors are used in the assessment of the volumetric water content of the soil but they require a calibration procedure in order to obtain reliable measurements. In this study, changes in Frequency Domain Reflectometry sensors calibration caused by the presence of root system were investigated. For this purpose, two substrate soil samples have been collected from an experimental Green Roofs located within the University of Salerno: the first, mainly consisting of peat, during the construction phase and the second, consisting of peat with a developed root system, two years later. Frequency Domain Reflectometry sensor measurements were plotted against observed volumetric water content to obtain calibration curves. Results show that the sensors seem not to be able to predict the water adsorbed by the root system, confirming the hypothesis that Green Roofs evolution can have an important impact on substrate volumetric water content observation. Full article

This study aims to assess the impact of the 2010–2011 flash floods on the crop production of Sanghar—an eastern district of Sindh. The population of almost two million is mainly dependent on agriculture. Cotton, sugarcane, and wheat are the main cash crops of the district. In 2010–2011 Sanghar was hit by flash floods after heavy rainfall. These floods adversely affected the crops standing at that time. However, on the other hand, they increased the fertility of agricultural lands. Satellite images, precipitation data, and geographical information system (GIS) tools were used to quantify floods’ effects by mapping pre- and post-flood vegetation cover. Supervised classification was applied on Landsat images from 2009 to 2013 to extract vegetation area. The temporal analysis unveils a significant increase in the vegetation cover in the post-flood years. Furthermore, the comparison between pre-and post-flood crop production data collected from the Pakistan Bureau of Statistics also validated the study results by revealing an increase in crop production. Full article

The St. Johns River, located in northeast Florida, USA, is a large watershed characterized by relatively flat topography, porous soils, and increasing urbanization. The city of Jacksonville, Florida is located near the downstream terminus of the river near the Atlantic Ocean. The lower portion of the watershed located downstream of Lake George is subjected to tidal exchange and storm surge from tropical storms and hurricanes as well as extra-tropical winter storms. Extreme flood events in the Lower St. Johns River can be caused by rain-driven runoff, high tide, storm surge or any combination of the three. This study examines the range of potential extreme flood discharges caused by rain-driven runoff within six larger sub-basins located in the Lower St. Johns River with special emphasis on the Pablo Creek sub-basin. The study uses multiple methods including published flood insurance data, two statistical hydrology methods, and model simulations to estimate an array of flood discharges at varying return frequencies. The study also examines the potential effects on flood discharges from future land use changes and the temporal distribution of rainfall. The rain-driven flood discharge estimates are then fit to a normal distribution to convey the overall risk and uncertainty associated with the flood estimates. Overall, the study revealed that a wide range of reasonable rainfall-driven flood estimates are possible using the same data sets. The wide range of estimates will help inform future resiliency projects planned in the study area by providing a more realistic set of bounds with which planning can proceed. The estimates derived herein for the Pablo Creek sub-basin can be combined with the independent or dependent effects of tide and storm surge in order to characterize the total flood resiliency risk of the region. Full article

Litter decomposition in intermittent streams is driven by the biotic compartment and uniquely shaped by abiotic conditions such as flow variability. In this study, we compared microbial-mediated decomposition of three temperate native leaf species (alder, chestnut, and oak) in the channel and riparian area of an intermittent stream. The stream channel presented a total of 8, 49, and 35 days of flow, isolated pools, and dry conditions, respectively, while the riparian area remained emersed. Independently of the species, decomposition rates after 3 months incubation were higher in the stream channel than in the riparian area. Alder and chestnut’s different quality was not translated into distinct fungal biomass, which seems to be related with an earlier fungal colonization and faster decomposition of the former. Leaves incubated in-channel presented higher fungal biomass than in the riparian area. During autumn, even in the absence of water flow, a higher moisture in the stream channel and the presence of isolated pools yielded significantly faster decomposition rates and fungal biomass accrual than in the riparian area. We may expect that, along with the resumption of surface flow, the reestablishment of hydrological connectivity will lead to the lateral and longitudinal transport of dissolved nutrients and organic matter of more (channel) or less (riparia) increased quality, fueling local and downstream communities. Full article

Hydrological variations hold a significant influence over the water chemistry in the karst systems within the critical zone. In this context, the Baget Catchment (BC) was monitored at high-resolution over 2 hydrological years. The high-frequency survey at the outlet of BC displayed multiple hydrochemical patterns in response to hydrological variations, mixing water sources, and biogeochemical processes. Among the major elements, sulfate exhibited the widest relative variation during flooding and showed a significant dilution, whereas calcium and bicarbonate revealed a chemostatic behavior as a result of carbonate dissolution in the karst. Hysteretic analysis evidenced the control of different hydrological reservoirs over the stream transport processes of dissolved elements. The concentration of dissolved organic carbon increased during the hydrograph rising limb and was controlled by surface runoff. The relationships between Ca²⁺ and HCO₃⁻ concentrations and stream discharge exhibited hysteresis patterns with counterclockwise loops, unlike all other elements, due to the carbonate weathering by biogenic CO₂-rich water. Finally, high-frequency sampling during storm events improved the understanding of the factors controlling the hydrochemical dynamic of the Baget stream water. The relative contributions of the karst and epikarst zones, of rainwater, as well as the role of different biogeochemical processes and the hydrological conditions were highlighted. Full article

Due to increasing anthropogenic activities, trace metals (TM) remain a major concern particularly in semi-arid countries with limited water resources. In this context, the present study aims to understand the geochemistry of trace metals in bottom sediments from the Sebou basin, representing 1/3 of the surface water resources of Morocco. Total concentrations of trace metals (As, Cd, Co, Cr, Cu, Ni, Pb, Zn) and some physicochemical parameters were measured in the fraction < 63 µm. The order of abundance of the elements was Zn > Cr > Cu > Ni > Pb > Co > As > Cd. The enrichment factor calculation showed that 70% of the samples were naturally concentrated in trace metals, especially As and Ni, as well as Cd and Pb, except at some stations. On the contrary, the most enriched elements were Cr, Zn, and Cu. Chromium presented an enrichment higher than 5 and toxicity risks at some stations, such as the downstream Fez city known for its important tannery activities. A multivariate analysis of the data evidenced the strong link between the identified natural elements (As, Co, Ni) with clays and Fe and Al oxides, whereas elements (Cd, Cu, Cr, Pb, Zn) mainly derived from anthropogenic activities (industrial and domestic waste, agricultural inputs) were linked to phosphorus and, to a lesser extent, particulate organic carbon. Full article

Polycyclic aromatic hydrocarbons (PAHs) belong to the group of persistent organic pollutants (POPs), which are major environmental pollutants associated with the environment. In this study (preliminary), the concentrations of eighteen (18) PAHs in soil, sediment, and fish sample (Clarias anguillaris) of Owan River and agricultural soil samples around the river in Edo State were studied using standard analytical methods. Gas chromatograph equipped with flame ionization detector (GC-FID) was used for the determination of PAHs. The study revealed the presence of the 18 determined PAHs in the soil, sediment, and fish (Clarias anguillaris) samples in varying concentrations. The concentrations of PAHs in the soil samples ranged between 0.0000–0.0463 (µg/kg) with total concentrations of ∑0.2390 (µg/kg) for soil sample 1 and 0.0000–0.0506 (µg/kg) with total concentration of ∑0.2700 (µg/kg) for the soil sample from location 2. The concentrations of the PAHs components in the sediments samples ranged between 0.00332–0.0319 (µg/kg) with total concentration of ∑0.150592 (µg/kg) for the sediment sample 1 and 0.002092–0.05866 (µg/kg) with total concentration of ∑0.0312183 (µg/kg) for the sediment sample 2. The concentration of PAHs components in the fish sample ranged between 0.0000–0.0746 (µg/kg) with total concentration of ∑0.300 (µg/kg). The concentrations of PAHs were higher in the soil samples than in the sediment samples. Concentrations of the PAHs residues detected in the fish samples were higher than those in the soil and sediment samples. In furtherance of this study, the number of sampling stations shall be increase to cover other communities while data generated will be subjected to more ecological risk assessments. Full article

Raw and thermally pretreated zeolite, denoted zeolite-T, was examined as a catalyst in the heterogeneous catalytic ozonation process. The catalytic activity was evaluated by the degradation of p-chlorobenzoic acid (p-CBA) at an initial concentration 4 μM, a typical biorefractory organic model compound. The results showed that the thermally pretreated zeolite presented higher catalytic activity than the raw material. Rates of 99.3%, 98%, and 94.5% degradation of p-CBA were achieved within 3 min of reaction/oxidation time, by applying the zeolite-T/O₃, zeolite/O₃, and single ozonation (O₃) procedures, respectively, under comparable experimental conditions. After 15 min treatment time, the concentration of p-CBA was found to be below the respective detection limit (0.025 μM) of the used analytical method (HPLC) for both catalytic processes, while the application of single ozonation ed to a 0.16 μM residual concentration of p-CBA. The removal of p-CBA was also examined for different initial pH values commonly found in natural waters, as well as for different oxidation reaction temperatures. Optimum conditions were defined as a pH value of 8 and 25 °C, during which the production of hydroxyl radicals in the aqueous phase was found to be increased. Furthermore, the degradation of two other common micropollutants (i.e., benzotriazole and carbamazepine), which present different reaction rate constants with ozone (i.e., 20 M⁻¹·s⁻¹ and 3 × 10⁵ M⁻¹·s⁻¹, respectively) was additionally evaluated. It was found that all these micropollutants can be sufficiently removed by the catalytic ozonation system in the presence of zeolite-T. However, it is worth noting that carbamazepine can also be easily removed by the application of even simple ozonation, and that the presence of catalyst simply decreased the necessary oxidation time for sufficient removal. On the other hand, benzotriazole presented a lower ozone degradation rate than the other micropollutants, and, during the early stage (i.e., after the third minute) of the oxidation reaction, it was found to be removed by 96.5%. Full article

Currently, pesticides are massively used in agricultural areas end up in watercourses, as they are usually final receptacles of organic contamination. A large number of wetlands such as ponds occurred in agricultural catchments. They are dynamic and complex systems which contains different compartments like the water column, sediments and biota. The sediment compartment can store contaminants according to their physicochemical properties, but this process is continuously challenged because of settling and resuspension mechanisms. The role of the sediments regarding pesticides behavior and their fate is still poorly investigated. Our study aimed to fill this gap, particularly considering the Bassioué pond, which is located in the carbonated agricultural upper sub-catchment of the Auradé critical zone observatory (Gers, France), with a wheat/sunflower crop rotation and a steep slope enhancing erosion phenomenon. We focused on pesticide storage in the sediments which represent the main compartment due to the environmental conditions. Our current objective was to understand (i) how and where pesticides are stored in the sediments, and (ii) the relationship with the characteristics of sediments, supposed to be highly involved in the storage and degradation of pesticides. Two field campaigns were carried out to collect sediment samples within a regular quadrat from the inlet to the outlet of the pond in autumn 2019 and summer 2020 at different depth. A set of three pesticide was quantified as well as sediment texture. The results highlighted that sediment particle size distribution varied between upstream and downstream of the pond: from the finest to the coarsest; as did the spatial distribution of pesticides. This reveled that pesticides were partly controlled by their physicochemical properties: most hydrophilic pesticides had greater affinity with the finest fractions of the sediments. A difference in pesticide storage according to the depth has been observed, especially for boscalid (logK_OW = 3) which was found in greater quantities in the deepest samples, with increasing coarse silt content. Finally, a seasonal effect was also observed on pesticide levels, as their presence was highly driven by firstly their uses in the catchment and secondly by the soil erosion occurring during intense spring flood events. This work provides new knowledge on the role of ponds in pesticide storage, dissipation and transfer downstream, which can·be used for agricultural landscape management. Full article