查看更多>>摘要：Phosphorus uptake by common and ornamental plants was studied in pilot-scale horizontal subsurface flow (HSSF) constructed wetlands (CWs) with monocultures and polycultures. Three HSSF CWs were planted with monocultures of Phragmites australis (HSSF-Phr), Schoenoplectw califomicus (HSSF-Sch) and Cyperus papyrus (HSSF-Cyp), and one polyculture was planted with C. papyrus and Zantedeschia aethiopica (HSSF-Cyp/Zant). During the experimental period, removal efficiency, growth characteristics, biomass production and phosphorus uptake were evaluated in the cold season (fall/winter) and warm season (spring/summer). In general, the cold season showed better performance with an order of HSSF-Cyp/Zant > HSSF-Cyp > HSSF-Sch > HSSF-Phr in the evaluated parameters. The removal efficiencies were 33%, 27%, 23% and 12%, respectively. The biomass production and density of the HSSF treatments ranged from 1.5 to 5.4 kg dry weight (DW)/m~2, and 435 to 1298 individuals/m~2 with higher values for HSSF-Sch. The tissue phosphorus content was 5 to 20% higher below-ground in all plants, including ornamentals. Phosphorus uptake was higher for polyculture (HSSF-Cyp/Zant) and monoculture (HSSF-Cyp) planted with ornamentals, with a mean of 30 g P/m~2. Also, the polyculture was not affected by the seasons, reaching up to 27% phosphorus uptake by the plants. According to our results, the ornamental species of the polyculture contribute to the phosphorus uptake.
查看更多>>摘要：A field experimentation conducted in a wooded degraded area and contaminated by metals, aimed to compare the effectiveness of four types of organic mulches: Ramial Chipped Wood (RCW), crushed Miscantlius, dead leaves and wheat straw regarding the ecosystem's functionality. We likewise tested the plastic sheeting regularly used to forestall weed development in green spaces as well as a negative control which consisted in soil without mulch. For this purpose, microbial activities (Fluorescein diacetate hydrolyzing activity, Laccases and Urease) and abiotic factors (moisture, temperature, metal concentrations, C/N rate and organic carbon content) were monitored in the organo-mineral horizon of soil surface for 13 months. The degradation rate of the different mulches has also been taken into account. The results revealed that the organic mulching technique could provide habitats for many organisms and micro-organisms of soil with favorable microclimate and/or alternative food source (fungi) in peri-urban and planted area, not only in agricultural areas. In the current context of climate change, the mulching technique could limit desiccation stress in terrestrial ecosystems by offering more favorable temperature conditions (≈2 ℃ lower on average than a surface soil without mulching) and this from the very first cm of the soil. In view of the indicators followed (high temperatures, low microbial activity and low biodiversity), the plastic sheeting present the most hostile reception conditions to the soil organisms. Every one of the organic mulch examined has its advantages and limitations and the decision of the kind of mulch to be utilized requires thinking as indicated by the fixed goals. However, Misccmthus seemed to be the most suitable compromise obtaining the higher score according to our evaluation criteria: it degraded slowly, it has low metal content and fungi were very active which is favorable to functionality of the ecosystem and to the soil organisms.
查看更多>>摘要：The aim of this study was to showcase derivation of numerical ranges of important environmental variables (hydraulics, water quality and habitat quality) for a predefined reference state of canals in an area where ecological rehabilitation is sought. The reference state was defined based on pollution tolerance index (PTI) of macroinvertebrates. From data collected for two years from three canals with varying levels of pollution for different seasons, dettended correspondence and redundancy analysis ordination plots revealed moderate to weak spatiotemporal gradients. Relationships were built via multiple linear regression (MLR) and by linear or quadratic bivariate models. MLR models managed to explain over 70% of the PTI variation and was significant at P < 0.1. Solving single parameter models with co-efficient of determination >0.3 and P < 0.1 with a targeted PTI of 11, gave season dependent feasible solutions and were mostly hydraulic and habitat quality variables. Out of 24 environmental variables, dry and wet seasons gave 15 and eight feasible solutions, respectively. This study validated the importance of certain environmental variables that are debatable in the context of a healthy stream (e.g., mesoscale physical habitats), showed instances where hydraulics became the defining factor of stream health, and also provided pros and cons of a widely discussed method in ecological rehabilitation.
查看更多>>摘要：This study evaluates the effect of deforestation on wetlands by hydrodynamic modeling. CAESAR-LISFLOOD is used in this study for the hydrodynamic modeling, which adopts the finite element method to solve the Saint-Venant equation and Manning's equation for kinematic wave flow. This study focuses on Jilmoe-neup wetland, a Ramsar wetland, in Korea. Although Jilmoe-neup wetland was once located in a thick forest, most trees were removed in the 1970s to expand the pasture. The simulation result shows that a reservoir effect is crucial to form the wetland, which is mainly due to the narrow and deep drainage channel at the outlet of the wetland. On the other hand, deforestation is found to have significantly changed the hydrodynamic characteristics of Jilmoe-neup wetland. In particular, increased flow velocity is found to induce hillslope erosion and sedimentation in the wetland area. More sand is likely to flow into the wetland, which must also hinder the formation of peat layers. Finally, with a moderate restoration of forest, it seems possible to recover and maintain Jilmoe-neup wetland along with the current peat layer.
查看更多>>摘要：Hydrological prediction is essential for managing and preserving headwater, wetland, and rural basins, yet it is difficult due to a lack of data. The Long Short-Term Memory (LSTM) network is a promising deep learning approach and has demonstrated excellent performance in streamflow prediction. However, due to the characteristics that require abundant and high-quality observations, most LSTM applications focus on investigating performance for data-rich basins. To investigate the applicability of LSTM in ungauged basins without hydro-logical observations, we introduce and test an approach to predict streamflow in ungauged basins using the LSTM network that has learned the integration of data from multiple gauged basins. Four learning strategies are constructed using various datasets such as ground-observed meteorological data, satellite data, and hydro-geomorphological characteristics. As a result, the LSTM network that learned the meteorological data in multiple gauged basins satisfactorily predicted streamflow in ungauged basins. The LSTM network that learned the satellite data further showed affirmative results. On the other hand, the LSTM, which additionally learned the hydro-geomorphological characteristics of the basins, exposed the need for improvement, such as securing additional various types of training data. In addition, it was recognized that additional efforts were needed to solve overfitting and out-of-distribution prediction problems. However, this approach achieved model performance deriving metrics above threshold values. These results show the potential of LSTM for streamflow prediction in ungauged basins including wetlands.
Gabriela Cristina SanchezHernan Ricardo HadadMaria Alejandra Maine
7页
查看更多>>摘要：A hybrid wetland (HW) consisting of a free-water surface flow wetland (FWSW) followed by a horizontal subsurface flow wetland (HSSFW) was constructed for the final treatment of wastewater from a pet-care center. Typha domingensis was planted in both wetlands. During the first year of operation, wastewater was separated from solid pet waste (first period). Then, that solid waste and liquid wastewater were treated together, causing a significant increase in the concentration of the pollutants (N, P, and organic matter) in the effluent treated in the HW (second period). The objectives of this work were to evaluate the performance of the system and compare its efficiency between periods. The HW was efficient in both periods, except for nitrate removal. Total mean removals were: 66.9 and 82.8% for COD, 74.9 and 88.3% for BOD, 61.9 and 83.0% for ammonium, 67.7 and 83.8% for TKN, 5.65 and 20.37% for nitrate, and 56.9 and 62.1% for TP in the first and second period, respectively. In the second period, mean removal efficiency percentages increased and the contaminant concentrations in the outlet were not significantly different from those of the first period. In the second period, the highest pollutant removal occurred in the FWSW mainly for COD, BOD and TKN. TP and TKN concentrations in plant tissues of the inlet area of FWSW were significantly higher than those in plants from the HSSFW. The study showed that this HW is a low cost, efficient and sustainable solution for the pet-care center wastewater treatment.
查看更多>>摘要：Northern peatlands are an important global climate regulator storing approximately one-third of the global carbon pool, however the degradation of these ecosystems from land-use change can switch peatlands to persistent and long-term sources of atmospheric carbon dioxide. Active restoration is often required to return degraded peatlands to a net carbon sink. The peat-block restoration technique, where intact peat blocks are extracted from a donor peatland and transferred to restore peatlands where the remnant peat is non-existent, contaminated, and/or undergoes seasonal flooding is increasingly being adopted as a peatland restoration technique given the carbon sequestration that can occur immediately post-restoration. However, donor peat blocks often need to be temporarily stockpiled during the restoration process due to logistical constraints. The dewatering of the peat blocks during this stockpiling period may alter hydrophysical peat properties that sustain critical peatland ecohydrological functionality and ultimately affect peatland restoration success. Yet, the hydrophysical evolution of stockpiled peat blocks remains unknown. Here, we examine how peat block stockpiling time (3, 7, 11, and 14 months and a reference site) impacts peat hydrophysical properties and sphagnum moss photosynthesis, both of which are critical for peatland restoration success. Stockpiling peat differentially impacted the hydrophysical properties between the shallower and deeper peats, where little to no impact from stockpiling was observed in the shallower peats, regardless of stockpiling time. Rather, as stockpiling time increased, there was a marked decrease in macroporosity (pores >75 μm) and mobile porosity (drainable porosity at approximately -100 hpa) at depths below 20 cm but the water conducting matrix porosity (defined as mobile porosity minus macroporosity) was not significantly different than the reference samples. However, stockpiling created inhospitable conditions for sphagnum mosses., as chlorophyll fluorescence ratio was below 0.3, indicating little to no photosynthesis of the stockpiled peat during summertime drought conditions. Taken together, we suggest limiting stockpiling time as much as possible would be advantageous for using the stockpiled peat blocks for the peat-block restoration technique or other restoration efforts, such as floating mat creation.
查看更多>>摘要：This paper investigates the hydraulic performance and solute transport processes in waste stabilization ponds (WSPs). A numerical model comprised of Reynolds-averaged Navier-Stokes (RANS) flow hydrodynamic model with the standard k - ε turbulence closure coupled with the advection-diffusion solute transport model, is developed in a three-dimensional Cartesian coordinate system. The proposed numerical model is successfully validated against laboratory-scale physical modelling measurements of flow hydrodynamics and solute characteristics across trapezoidal pond geometry. The developed numerical model is adopted to run series of scenario-based simulations to investigate the effects of WSPs geometrical features and implementation of an island retrofitting on the hydraulic performance and treatment efficiency of the WSPs. Fifteen pond configurations with varying side-walls slope and island configurations are simulated. Vertical and horizontal structures of flow hydrodynamics across the pond are investigated. Solute transport processes are studied through determining residence time distribution (RTDs) curves based on numerical tracer simulations. Two deflector island configurations (parallel and rotated) are simulated to investigate their influence on enhancing the hydraulic performance of the WSP. The analysis of the numerical results indicates an overall positive impact of deflector island retrofitting on the hydraulic performance of the WSP. The side-walls slope are shown to play a key role in determining the overall performance of the WSP. For the cases with side-walls slope of 1:1, 0.5:1 and 0:1, the hydraulic efficiency of the WSP was enhanced by adding both parallel and rotated islands. However, for the cases with side-walls slope of 2:1 and 1.5:1, addition of island deflector is shown to have negative impacts on the hydraulic performance of the waste stabilization pond.
查看更多>>摘要：Bacteria serve as important components of a constructed wetland (CW) system. Various bacterial communities aid in pollutant removal; however, environmental conditions and other external variables can greatly affect their performance and diversity. In this study, four constructed wetlands treating secondary livestock wastewater (LCW), agricultural runoff (ACW1 and ACW2) and urban stormwater (HCW) were investigated to evaluate the relationship between the inflow pollutants and the bacterial community. Based on the findings, the 20 dominant bacterial species in water samples collected from the livestock area (LCW) constituted 98.5% to 99.7% the total bacterial population. In the case of agricultural areas (ACW1 and ACW2), the 20 most abundant bacterial species constituted 99.7% to 99.8% of the total bacterial population. Similarly, the 20 dominant bacterial species found in the soil samples from livestock and agricultural areas made up 97.2% to 98.7% and 99.1% to 99.6% of the total bacterial population, respectively. Generally, the diversity of bacteria in soil was higher compared to water. It is important to establish a target bacterial habitat when creating CW for optimized ecological functions.
查看更多>>摘要：Basin-scale runoff changes reflect the comprehensive impact of various environmental variables including climate and vegetation. Among them, vegetation plays an important role in the process of runoff generation and is one of the key Units affecting the hydrological cycle. However, the contribution of vegetation to runoff changes is still unclear. In order to analyze the main driving factors of runoff changes in the Yanhe River Basin, this research builds a BPG model based on the Budyko framework, Porporato model, and Guswa model to evaluate the sensitivity coefficient of runoff to vegetation change, and quantitatively reveals the contribution of vegetation to runoff change. The results showed that, the runoff in the Yanhe River Basin decreased significantly from 1982 to 2018, and a mutation point occurred in 1999. After that, the runoff decreased by 29.88% and the NDVI increased by 15.30%. In terms of the sensitivity to runoff changes, runoff is more sensitive to changes in basin characteristics including vegetation than the climate change. According to the concepts of relative contribution and absolute contribution proposed in this research, the relative contribution rate and absolute contribution rate of climate change and basin characteristic changes were - 18.13%, 117.67% and 43.22%, 56.78%, respectively. Changes in basin characteristics such as vegetation, terraces and check dams caused by human activities are the main causes for runoff changes. The relative contribution rate and absolute contribution rate of vegetation change to runoff change were 34.98% and 16.88%, respectively, which is one of the dominant factors for basin characteristics change. And basin characteristic factors such as artificial water withdrawal, terraces and silt dams are the other main contributors to runoff changes. The research results can provide a theoretical basis for guiding future ecological restoration projects and water resources planning in the basin.
NSTL