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  • Open access
  • 86 Reads
Spatio-temporal Dynamic Changes and Ecological Effects of Dish-shaped Lake in Poyang Lake

Poyang Lake is an internationally important wetland, the largest migratory bird habitat in Asia, and the largest freshwater lake in China. Its ecological environment has a wide range of international attention and influence. The dish-shaped lake is a seasonal sub-lake exposed on the beach during the dry season of Poyang Lake. Its special hydrological and geomorphic characteristics provide a good habitat for more than 80% of the lake’s wintering migratory birds. On the other hand, the widely distributed dish-shaped lakes with varying heights effectively alleviated the impact of drought and flood disasters on the Poyang Lake wetland ecosystem, and is of great significance to maintaining the stability of the Poyang Lake basin ecosystem and biodiversity. Compared with the breadth and depth of research on the water ecosystem of the main lake area of Poyang Lake, the dish-shaped lake has received less attention. This study takes Poyang Lake's dish-shaped lake as the research object, based on long time series remote sensing data, it analyzes the water area, water-sediment, and the spatio-temporal dynamic characteristics of vegetation from different time scales (month, quarter, and year); combined with nature and social economy Data analysis of the driving factors of its changes. On this basis, the ecological effects brought by the dynamic changes of the dish-shaped lake water area were discussed from the aspects of migratory bird habitat changes and agricultural production, in order to lay a foundation for the protection of wintering migratory birds and their habitats in the region, and to maintain the Poyang Lake ecosystem Provide guidance on safety and biodiversity.

  • Open access
  • 83 Reads
Changes in the intensity of human activities in the Erhai Lake Basin and its impact on the lake water environment
With the warming of the climate and the intensification of human activities, many lakes in the world are facing many problems such as deterioration of water quality and eutrophication. Erhai Lake is a national key protected water area in China, with various functions such as regulating regional climate, fisheries, and tourism. In recent years, the population around Erhai Lake has increased dramatically, and the rapid development of agriculture and tourism has caused the lake's water quality to face many problems and water ecological degradation is obvious, which seriously affects the sustainable utilization of the lake. The intensity of human activities in Erhai Lake Basin involves various aspects such as economy and society. At present, it is rare to use multi-source remote sensing data and a variety of social and economic data to establish an index system of human activity intensity, quantitatively evaluate the intensity of human activity and analyze its spatial and temporal distribution. This research uses Gaofen-2 satellite and Landsat imagery as the main data sources to extract land use information from 1986 to 2019 in the Erhai Lake Basin with high precision. Based on the concepts of human activity intensity and construction land equivalent, comprehensive consideration of ecology, economy, and society Sustainable development and other factors, establish a human activity intensity model to evaluate the human activity intensity of each administrative unit in the Erhai Lake Basin and its different sub-basins; On this basis, the temporal and spatial changes of human activity intensity in the basin and its impact on Erhai Lake environment are analyzed, which lays a foundation for further analysis of the changes of ecosystem in Erhai Lake, and provides reference for the study of the impact of human activities on lake water environment in other basins.
  • Open access
  • 151 Reads
A novel aggregate cyanobacterial biomass proportion index for estimating cyanobacteria succession in early eutrophic Lake Erhai, China

Erhai Lake, located on the Yungui plateau in southwest China, has been considered to be in a transition period of ecological process, posing an urgent need for understanding its historical succession of cyanobacteria and further detecting the early signals of cyanobacteria accumulation for developing management strategies in advance. For this reason, an aggregate cyanobacterial biomass proportion index (ACBPI) was introduced as bio-indicator for reflecting increased accumulation of cyanobacteria, through targeting cyanobacteria-associated indexes derived from satellite remote sensing using principal component analysis. Thresholds for ranking the cyanobacteria abundance state were then determined through in situ phytoplankton composition data and the entire ACBPI time series. The results showed that the ACBPI correlated with cyanobacteria biomass proportion with an accuracy level of 66% and cyanobacteria biovolume proportion with coefficient of determination 80%. Dense bloom appeared primarily in northern regions, with 5.5% occurring in 2003, 9.1% in 2006, and 6.7% in 2008. The frequency of moderate bloom in northern lake made up a higher share (14.1±16.0%) across the whole periods, with 6.2±10.7% in central lake and 2.5±4.0% in southern lake. Apparent mitigation of cyanobacterial dominance condition was observed in 2016-2019 in contrast to 2003-2011 with obvious reduction occurring in 2018, probably resulting from series of strict protection initiatives implemented in recent years. However, moderate bloom in northern bays occurred again in 2019, indicating that strict nutrient reduction especially phosphorus pollution should be strengthened under global warming and wind speed decreasing scenario.

  • Open access
  • 124 Reads
New Assessment of the Analysis of Wastewater Quality from a Wastewater Treatment Plant Using the RAPS Method

Water is an important factor in human health and an essential ingredient of living organisms and necessary for the life of all living organisms. With the increase in the population and the increase of sliving standard, there was an increase in water consumption, which led to a large increase in the amount of wastewater. Prior to discharge into the environment, the wastewater must be treated with a wastewater treatment device. Wastewater treatment of the public mixed-drainage system of the city of Čakovec in Croatia and suburban settlements is carried out by mechanical and biological procedures, with the final treatment of the separated sludge. The paper will analyze the values of input and output time series of chemical oxygen demand (COD), biological oxygen demand (BOD5), and suspended solids (SS) on the wastewater treatment plant using the RAPS method (Rescaled Adjusted Partial Sums). The results showed that the input series contain more pronounced subseries with respect to their mean values and trends of increase and decrease, respectively. By comparing the input and output subseries, it can be seen that the output subseries do 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.

  • Open access
  • 204 Reads
AGRICULTURAL WATER BALANCE STUDY IN SINDH (PAKISTAN) USING SATELLITE-DERIVED ACTUAL EVAPOTRANSPIRATION

The rising water demand, coupled with mismanagement and misallocation of water, has caused water scarcity in the Sindh Province of Pakistan. The Sindh province almost entirely relies on the Indus River supply to meet its agricultural demand. The rising population will demand more food, but at the same time, agriculture water share will be under pressure due to the increasing demand of other competing users. Many studies have predicted a shortfall of water in the coming years, which will cause food security issues in the country. Since agriculture is the largest water user among all sectors, effective water management in this sector will have the most significant impact. A water balance study is presented in this paper to evaluate the current and future water supply and demands and develop sustainable agriculture water budgeting. Actual evapotranspiration (ET) or consumptive water in the entire irrigated region of Sindh comprising 14 canal command areas (CCAs) during the Rabi and Kharif seasons of 2017-2019 was studied. The study utilized Landsat satellite data product from the Earth Engine Evapotranspiration Flux (EEflux). Study results identified shortages during the Rabi seasons when flows are usually low, but consumptive water use is more than the available quantum from canal flows and rainwater. However, the Kharif season presented an opposite trend. Within CCAs, the supplies and demands showed variable trends that can be balanced by adjusting surplus and deficit supplies by recalculating canal allocations. Suggestions for balancing water in these CCAs were also presented in this study.

  • Open access
  • 74 Reads
Evaluation of the Impacts of Land Use on Water Quality: A Case Study in Erhai Lake Basin

Erhai Lake, the second largest freshwater lake in the Yunnan Province of China, has the flourishing tourist industry. Unfortunately, many problems such as deterioration of water quality and eutrophication were occurred in Erhai Lake, leading to numerous environmental problems. Chlorophyll-a (chl-a) and water transparency are critical ecological and environmental parameter for water quality, which play the important roles in the wetland environment and eutrophication of water. Human-induced land-use change can indicate the degree of the interference of anthropogenic activities on the regional ecological environment. Therefore, understanding the relationships between changes in land use and water quality is of great importance to improve water pollution control and for providing guidelines for land use planning. However, the effects of ongoing anthropogenic activities on water quality in Erhai Lake Basin are not well understood. Closing this knowledge gap first requires obtaining the accurate land use change information. A Random Forest classifier could be applied to spectral as well as textural features extracted from time-series of Landsat MSS/TM/ETM+/OLI imagery, ranging from 1973 to 2020, to increase the accuracy of land cover classification. The classification results show the spatiotemporal patterns and characteristics of land-use change in Erhai Lake Basin. Besides, the Landsat TM/ETM+/OLI, Medium Resolution Imaging Spectrometer (MERIS), MODIS (moderate resolution imaging spectroradiometer) and Sentinel-3 OLCI satellite data were used to estimate the chl-a concentration and water transparency in Erhai Lake from 1985 to 2020. Long-term water transparency and chl-a distributions of Erhai Lake revealed the changing trend of water quality. We use the geographically weighted regression (GWR) model to identify the impact of land-use change on chl-a concentration and water transparency. The land use change has a direct impact on water quality varied over nearly five decades; both positive and negative effects for certain land-use types were found in Erhai Lake Basin. These findings shed new light on the impact changes of land use on water quality and provide a scientific foundation for land use management and remediation plans.

  • Open access
  • 45 Reads
Mapping wetland characteristics using temporally dense Sentinel-1and Sentinel-2data in Poyang lake

Landscape dynamics of wetland are critical for understanding Lake ecosystem health and sustainability. The paper characterizes the spatiotemporal dynamics of the wetland landscape in the Poyang lake during 2017–2019 to reveal the spatially explicit influential indicators. Time-series Sentinel 2 and Sentinel 1 (C-band) images are used to investigate the spatial-temporal image characters variation for different wetland vegetation in growing season. NDVI, IRECI, Backscattering coefficients, scatter mechanisms will be selected from the Sentinel 2 and Sentinel 1 to study the spectral and structure information of the wetland vegetation. SVM and Random Forest are used to classify the time-series images. The results showed that NDVI and IRECI were the main factors to decide the accuracy of the map. And backscatter coefficients VH polarization and spatial-temporal scatter mechanisms are the good supplement to improve the classification accuracy. Carex and miscanthus are the main communities for Poyang lake wetland. The landscape of the wetland vegetation partially change during 2017-2019 since the high dynamic hydrological changes. The amount of Zizania community is increasing greatly with the water level decreasing. Furthermore, the water level decreasing played an important role to accelerate the swampiness of the Lake wetland.

  • Open access
  • 91 Reads
Evaluation of green-roofs evolution's impact on substrate soil water content by FDR sensors calibration

In the last decades, strategies involving the use of green infrastructures became necessary to mitigate environmental problems and hydrogeological risks associated with invasive urbanization dynamics. Green roofs (GRs) are considered, in this context, a promising solution able to help traditional drainage systems to manage urban runoff in a sustainable and effective manner retaining stormwater and reducing the peak flow.

However, the performance of these systems is strongly impacted by climatic conditions, design parameters and aging. In particular, the evolution of physical and chemical properties of the substrate and vegetation layers of green roofs may lead to substantial changes in their hydraulic parameters and in the overall hydrological behaviour. The growth of the roots in the substrate layer, above all, seems to affect the interpretation of the soil moisture content, which is considered one of the key parameters in the definition of GRs retention performance. Generally, FDR (Frequency Domain Reflectometry) sensors are widely used in the assessment of the volumetric water content (VWC) of the soil for their durability and reliability but a calibration procedure is essential to get accurate assessments.

In this study, changes in FDR sensor's calibration caused by the presence of root systems were investigated. For this purpose, two substrate soil samples have been collected from an experimental green roof located within the University of Salerno campus (Italy). A first sample was collected during the construction phase and a second sample was collected two years later. In the first case, the sample totally consisted of peat whereas in the second case a well developed root system was detected. FDR readings were plotted against actual volumetric water content, calculated by multiplying the gravimetric water content by the bulk density of the peat, to obtain calibration curves. Results indicate that for soil water content lower than the soil water holding capacity (about 30%), and for the same gravimetric water content, FDR measurements provided lower values of VWC for the soil sample with the developed root system. This would indicate how water adsorbed by the root system cannot be sensed by FDR sensors. As a consequence the green roof substrate and vegetation evolution can have an important impact on substrate soil water content observation which should be acknowledged in planning monitoring campaign.

  • Open access
  • 98 Reads
The influence of environmental variables on diversity of spring zooplankton in the artificial Bydgoszcz Channel: a case study.

The Bydgoszcz Channel is an important artificial channel connecting two of the largest rivers and their catchments in Poland and in central Europe, the Vistula and Odra. It is also the main vector connecting the Noteć River from the East and near the mouth to Brda river from the West. Except for hydrography the Bydgoszcz Channel is also an interesting artificial river from the ecological point of view. In the present study we identified and compared the zooplankton community along with physicochemical and biological properties. Water samples were collected on Bydgoszcz Channel and Notecki Channel monthly during the spring (April 2019 to June 2019). We investigated how the flow of the channel and its tributary affected the various physicochemical and biological conditions (including water temperature, water transparency, dissolved oxygen, saturation, conductivity, pH, nitrate, phosphate and Chl-a concentration). These analysed parameters in turn affected the seasonal variations of zooplankton diversity (T) and density (N). The zooplankton community was dominated by rotifers and crustaceans. During May we recorded the highest rotifer density (N Rot) 2090 ind/L in Bydgoszcz Channel with an average 1256 ind/L and highest rotifer diversity (T Rot) of 20 species. The most dominant were Keratella cochlearis, Keratella quadrata, Polyarthra dolichoptera. The highest crustacean density (N Crust) was recorded during June on Bydgoszcz Channel 1420 ind/L with an average of 564.5 ind/L and diversity (T Crust) of 8 species recorded from Notecki Channel. The most dominant species among crustaceans was the cladoceran Bosmina longirostris. We assume that the crustacean diversity, density and biomass increased due to increasing temperature. On the contrary, the rotifers species decreased. It follows that adult copepods and their larval stages copepodites could eat small rotifers causing a decline in the number of rotifers. It is also possible that the decline in rotifer numbers could have been caused by competition for food with the Cladocera.

  • Open access
  • 126 Reads
Thermal treated zeolite as catalyst in heterogeneous catalytic ozonation – optimization of experimental conditions and micropollutants degradation

Raw and thermally pre-treated zeolites, denoted as zeolite-T, were examined as catalysts in the heterogeneous catalytic ozonation process. Their catalytic activity was evaluated by the degradation of p-chlorobenzoic acid (p-CBA) (initial concentration 4 μΜ), a typical biorefractory organic model compound. The results showed that the thermally pre-treated 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, applying the zeolite T/O3, the zeolite/O3 and the single ozonation (O3) procedures, respectively. After 15 min treatment time the concentration of p-CBA was found to be below the detection limit (0.025 μΜ) of the analytical method used (HPLC) for both catalytic systems, while the application of single ozonation reached 96% for the removal 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. The optimum conditions were defined at the pH value 8 and 25o C, during which the production of hydroxyl radicals in the aqueous phase were found to be increased. Furthermore, the degradation of two other common micropollutants (i.e. benzotriazole and carbamazepine), presented higher pKa values (i.e. 9.04 and 16, respectively) than the p-CBA, as well as different reaction rate constants with ozone (i.e. 20 M-1s-1 and 3*105 M-1s-1) 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 be also easily removed by the application of even simple ozonation and that the presence of catalyst just decreased the respective oxidation time. On the other hand, benzotriazole presented a lower ozone degradation rate than the other micro-pollutants and during the early stage (i.e. after the 3rd min) of the oxidation reaction it was found to be removed by 96.5%.

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