Open Water Ponds Research Articles

Vegetation Loss Following Vertical Drowning of Mississippi River Deltaic Wetlands Leads to Faster Microbial Decomposition and Decreases in Soil Carbon

AbstractWetland ecosystems hold nearly a third of the global soil carbon pool, but as wetlands rapidly disappear the fate of this stored soil carbon is unclear. The aim of this study was to quantify and then link potential rates of microbial decomposition after vertical drowning of vegetated tidal marshes in coastal Louisiana to known drivers of anaerobic decomposition altered by vegetation loss. Profiles of potential CH4 and CO2 production (surface to 60 cm deep) were measured during anaerobic incubations, organic matter chemistry was assessed with infrared spectroscopy, and soil porewater nutrients and redox potentials were measured in the field along a chronosequence of wetland loss. After vertical drowning, pond soils had lower redox potentials, higher pH values, lower soil carbon and nitrogen concentrations, lower lignin: polysaccharide ratios, more NH4+ and PO43−, and higher rates of potential CO2 release than vegetated marsh soils. Potential CH4 production was similar in vegetated marshes and open water ponds, with depth‐dependent decreases in CH4 production as soil carbon concentrations increased. In these anoxic soils, vegetation loss exerts a primary control on decomposition rates because flooding drives sustained increases in porewater nutrient availability (NH4+ and PO43, dissolved organic carbon) and decreases in redox potential (from −150 to −500 mV) that lead to higher potential CO2 fluxes within a few years. Without new carbon inputs following wetland loss, the sustained decomposition in open water ponds may lead to losses of stored soil carbon and could influence global carbon budgets.

Speciation and Risk of Heavy Metals in Surface Sediments of Different Types of Water Bodies in Baiyangdian Lake

The morphological characteristics of Cd, Cr, Cu, Ni, Pb, and Zn in sediments were analyzed using an improved BCR extraction method in four water types of Baiyangdian Lake:watercourse, trench, lake surface, and fish pond. The potential ecological risk index, secondary and primary phases, and risk assessment codes were used to systematically assess the pollution level and ecological risk of heavy metals in surface sediments. The results showed that:① the mean contents of heavy metals Cd, Cu, and Zn in the sediments were 0.37, 28.49, and 83.08 mg·kg-1, respectively, 94.91%, 73.91%, and 46.39% of which exceeded the soil background value. ② Cd was dominated by the non-residual fraction (F1+F2+F3) with a fraction ranging from 54% to 97%, whereas Cr was dominated by the residual fraction (F4) with a mass fraction ranging from 87% to 99%. Cu, Ni, Pb, and Zn were mainly in the fraction of residual fraction. In the non-residual fraction, Cu and Ni were mainly in the oxidizable fraction (F3) state, whereas Pb and Zn were mainly in the reducible fraction (F2) state. ③ The RAC risk assessment results showed that there were 68.97%, 39.89%, 54.84%, and 49.78% points in channel, trench, open water, and fish pond samples, respectively, of Cd at high risk. The Cu, Ni, and Pb were at low risk. In general, the overall heavy metal pollution level in Baiyangdian Lake was low, but Cd had ecological risk and high bioavailability in the Fuhe River of the Nanliuzhuang area and the Baigouyin River.

Characterization of vegetated and ponded wetlands with implications towards coastal wetland marsh collapse

Coastal wetlands provide numerous ecosystem services; yet these ecosystems are increasingly vulnerable to climate change stressors, especially excessive flooding from sea-level rise and storm events. This study highlights the important contribution of vegetation belowground biomass to marsh stability and identifies loss of vegetation as a critical driver of marsh collapse. We investigated the shear strength of salt marshes and unvegetated interior ponds using a modified cone penetrometer along a chronosequence of wetland marsh collapse (0 to 21 + years following pond formation) to characterize changes in the structural integrity of the marsh soil. Following conversion from vegetated marsh to open water pond, the surficial soils experienced a dramatic loss in shear strength resulting from the loss of vegetation and compaction of soil pore space. The Cone Penetrometer Testing (CPT) data indicate that higher shear strength in the surficial layers of the vegetated marsh sites were never recovered, up to 21 + years following marsh collapse. Coupled with significant elevation loss from marsh collapse, additional sea-level rise, deep subsidence, and reduced sedimentation may contribute to conditions that can exceed critical flooding thresholds, making recovery from marsh collapse difficult or impossible. Therefore, characterizing mechanisms and thresholds of marsh collapse are critical for identifying those coastal marshes that are vulnerable to collapse before conversion from vegetated marsh to open water occurs.

A Model of the Spatiotemporal Dynamics of Soil Carbon Following Coastal Wetland Loss Applied to a Louisiana Salt Marsh in the Mississippi River Deltaic Plain

AbstractThe potential for carbon sequestration in coastal wetlands is high due to protection of carbon (C) in flooded soils. However, excessive flooding can result in the conversion of the vegetated wetland to open water. This transition results in the loss of wetland habitat in addition to the potential loss of soil carbon. Thus, in areas experiencing rapid wetland submergence, such as the Mississippi River Delta, coastal wetlands could become a significant source of carbon emissions if land loss is not mitigated. To accurately assess the capacity of wetlands to store (or emit) carbon in dynamic environments, it is critical to understand the fate of soil carbon following the transition from vegetated wetland to open water. We developed a simple soil carbon model representing soil depths to 1 m using the data collected from a Louisiana coastal salt marsh in the Mississippi River Deltaic Plain to predict soil carbon density and stock following the transition from a vegetated salt marsh to an open water pond. While immediate effects of ponding on the distribution of carbon within the 1‐m soil profile were apparent, there were no effects of ponding on the overall, integrated, carbon stocks 14 years, following wetland submergence. Rather, the model predicts that soil carbon losses in the first meter will be realized over long periods of time (∼200 years) due to changes in the source of carbon (biomass vs. mineral sediment) with minimal losses through mineralization.

Historical variations of sedimentary organic matter sources and their relationships with human socio-economic activities in multiple habitats of a shallow lake

Understanding the source and historical variation of sedimentary organic matter (OM) and their relationships with human socio-economic activities is of great significance to water resource management. In this work, sediment cores from five different habitats were collected in Baiyangdian Lake, China. A Bayesian model (stable isotope analysis in R, SIAR) was utilized to apportion the historical changes of the proportional contributions of potential sources in sediments based on carbon and nitrogen stable isotopes (δ13C and δ15N) and C/N ratios. The impacts of human socio-economic activity factors (GDP, population) on the historical variations of sedimentary OM source have been evaluated by the generalized additive models (GAMs). The results showed that autochthonous OM (phytoplankton) was the dominant sediment OM source in river course (13%–48%), lotus pond (16%–48%) and open water (16%–47%), and the contributions began to increase after 1944, 1950 and 1962, respectively. Phytoplankton (37%–53%) was also the main source of OM in sediments of fish pond, but its contribution had remained high throughout. Allochthonous OM (soil OM: 29%–42%) was the main source of sedimentary OM in reed marshes, and it showed a slow increasing trend after 1995. The GAMs results showed that population was the dominant contributor to the variations of OM sources in sediments of lotus pond, open water and fish pond and GDP was the dominant contributor to that in sediments of reed marshes, with the interpretation rates of 70%–99%. Both GDP and population were dominant influence factors on sedimentary OM sources of river course, which account for 52%–98%. It is proved that human socio-economic activities have significant impact on the historical variations of sedimentary OM sources.

Permafrost thaw driven changes in hydrology and vegetation cover increase trace gas emissions and climate forcing in Stordalen Mire from 1970 to 2014.

Permafrost thaw increases active layer thickness, changes landscape hydrology and influences vegetation species composition. These changes alter belowground microbial and geochemical processes, affecting production, consumption and net emission rates of climate forcing trace gases. Net carbon dioxide (CO2) and methane (CH4) fluxes determine the radiative forcing contribution from these climate-sensitive ecosystems. Permafrost peatlands may be a mosaic of dry frozen hummocks, semi-thawed or perched sphagnum dominated areas, wet permafrost-free sedge dominated sites and open water ponds. We revisited estimates of climate forcing made for 1970 and 2000 for Stordalen Mire in northern Sweden and found the trend of increasing forcing continued into 2014. The Mire continued to transition from dry permafrost to sedge and open water areas, increasing by 100% and 35%, respectively, over the 45-year period, causing the net radiative forcing of Stordalen Mire to shift from negative to positive. This trend is driven by transitioning vegetation community composition, improved estimates of annual CO2 and CH4 exchange and a 22% increase in the IPCC's 100-year global warming potential (GWP_100) value for CH4. These results indicate that discontinuous permafrost ecosystems, while still remaining a net overall sink of C, can become a positive feedback to climate change on decadal timescales.This article is part of a discussion meeting issue ‘Rising methane: is warming feeding warming? (part 2)’.

Bioaccumulation of 137Cs and 60Co in freshwater plants

Contamination of the aquatic environment by the heavy metals and radionuclides has become a serious concern in the world. In our study, gamma-spectrometry of freshwater plants Bacopa monnieri and Egeria densa growing in cultivation media spiked with 137CsCl and 60CoCl2 was used for quantitative determination of bioaccumulation kinetic and distribution Cs+ and Co2+ ions in plant tissues. We found, that bioaccumulation of Cs and Co by fully immersed B. monnieri in Hoagland media (HM) was dependent on ion concentration in medium. Approx. 5-times lower Cs uptake 2.9 nmol/g (d.w.) was obtained in plants cultivated in 20% HM than from deionized water. The maximal Co uptake was 4-times higher than cesium uptake at the same conditions. Both Cs and Co were localized mainly in roots. The highest immobilization from roots to shoots was found in the case of Co uptake from deionized water with concentration ratio [Co]leaves : [Co]stem : [Co]root = 1.00 : 5.33 : 56.8. Cesium uptake by submerged plant E. densa was also strongly dependent on nutrients concentration in medium. However, in the case of cobalt uptake this dependence was less pronounced. Nutrients concentration also had a significant influence on distribution of Cs between stems and leaves of E. densa. Cesium was localized in leaves, however with increasing of nutrients concentration in cultivation media Cs was localized for account of stem. On the other hand, cobalt was immobilized mainly in leaves in whole range of nutrients concentration. Obtained data can serve as a models for understanding of phytoaccumulation of radionuclides from open water ponds and water channels in the vicinity of nuclear power plants and monovalent and bivalent metals from industrial sources of contamination.

Supplementing Remote Sensing of Ice: Deep Learning-Based Image Segmentation System for Automatic Detection and Localization of Sea-ice Formations From Close-Range Optical Images

This paper presents a three-stage approach for the automated analysis of close-range optical images containing ice objects. The proposed system is based on an ensemble of deep learning models and conditional random field postprocessing. The following surface ice formations were considered: Icebergs, Deformed ice, Level ice, Broken ice, Ice floes, Floebergs, Floebits, Pancake ice, and Brash ice. Additionally, five non-surface ice categories were considered: Sky, Open water, Shore, Underwater ice, and Melt ponds. To find input parameters for the approach, the performance of 12 different neural network architectures was explored and evaluated using a 5-fold cross-validation scheme. The best performance was achieved using an ensemble of models having pyramid pooling layers (PSPNet, PSPDenseNet, DeepLabV3+, and UPerNet) and convolutional conditional random field postprocessing with a mean intersection over union score of 0.799, and this outperformed the best single-model approach. The results of this study show that when per-class performance was considered, the Sky was the easiest class to predict, followed by Deformed ice and Open water. Melt pond was the most challenging class to predict. Furthermore, we have extensively explored the strengths and weaknesses of our approach and, in the process, discovered the types of scenes that pose a more significant challenge to the underlying neural networks. When coupled with optical sensors and AIS, the proposed approach can serve as a supplementary source of large-scale `ground truth' data for validation of satellite-based sea-ice products. We have provided an implementation of the approach at https://github.com/panchinabil/sea_ice_segmentation.

Increasing Hydroperiod in a Karst-depression Wetland Based on 165 Years of Simulated Daily Water Levels

The hydrology of seasonally inundated depression wetlands can be highly sensitive to climatic fluctuations. Hydroperiod—the number of days per year that a wetland is inundated—is often of primary ecological importance in these systems and can vary interannually depending on climate conditions. In this study we re-examined an existing hydrologic model to simulate daily water levels in Sinking Pond, a 35-hectare seasonally inundated karst-depression wetland in Tennessee, USA. We recalibrated the model using 22 years of climate and water-level observations and used the recalibrated model to reconstruct (hindcast) daily water levels over a 165-year period from 1855 to 2019. A trend analysis of the climatic data and reconstructed water levels over the hindcasting period indicated substantial increases in pond hydroperiod over time, apparently related to increasing regional precipitation. Wetland hydroperiod increased on average by 5.9 days per decade between 1920 and 2019, with a breakpoint around the year 1970. Hydroperiod changes of this magnitude may have profound consequences for wetland ecology, such as a transition from a forested wetland to a mostly open-water pond at the Sinking Pond site. More broadly, this study illustrates the needs for robust hydrologic models of depression wetlands and for consideration of model transferability in time (i.e., hindcasting and forecasting) under non-stationary hydroclimatic conditions. As climate change is expected to influence water cycles, hydrologic processes, and wetland ecohydrology in the coming decades, hydrologic model projections may become increasingly important to detect, anticipate, and potentially mitigate ecological impacts in depression wetland ecosystems.

Floating PV; an assessment of water quality and evaporation reduction in semi-arid regions

Abstract This work addresses the potential impact on water quality and quantifies the benefit of the low carbon power source of floating solar panels in evaporation reduction when using them on an open water body, such as an agricultural irrigation pond in semi-arid regions. By utilizing agricultural ponds for low carbon energy conversion, and saving precious water through evaporation reduction, the highly vulnerable agricultural sector will be empowered. A pilot size setup is prepared, key water quality parameters were monitored and evaporation quantities in a PV-covered pond are compared to those from an adjacent open water pond used as a control. Several inclination angles for the panels were tested. Results showed no adverse impact on the water quality; on the contrary, there is evidence of improvement particularly in nitrate and chlorophyll concentrations. Moreover, a reduction of ~60% in evaporation was observed; power generation from the floating panels, on the other hand, was statistically similar to that from ground-mounted panels.

The importance of capturing late melt season sea ice conditions for modeling the western Arctic ocean boundary layer

To better understand the response of the western Arctic upper ocean to late summer ice-ocean interactions, a range of surface, interior, and basal sea ice conditions were simulated in a 1-D turbulent boundary layer model. In-ice and under-ice autonomous observations from the 2014 Marginal Ice Zone Experiment provided a complete characterization of the late melt-season sea ice and were used to set initial conditions, update boundary conditions, and conduct model validation studies. Results show that underestimates of open water and melt pond fraction at the sea ice surface had the largest influence on ocean-to-ice turbulent heat fluxes reducing basal melt rates by as much as 32%. This substantial reduction in latent heat loss was attributed to underestimates of open water areas and the exclusion of melt ponds by low-resolution synthetic aperture radar imagery. However, the greatest overall effect on the ice-ocean boundary layer came from mischaracterizations of basal roughness, with smooth ice scenarios resulting in 7 m of summer halocline shoaling and preservation of the near-surface temperature maximum. Rough ice conditions showed a 23% deepening of the mixed layer and erosion of heat storage above 40 m. Adjustments of conductive heat fluxes had little effect on the near-interface heat budget due to small internal thermal gradients within the late summer sea ice. Results from the 1-D boundary layer simulations highlight the most influential components of sea ice structure during late summer conditions and provide the magnitude of errors expected when ice conditions are mischaracterized.

Monte Carlo Study of UAV-Measurable Albedo over Arctic Sea Ice

AbstractIn anticipation that unmanned aerial vehicles (UAVs) will have a useful role in atmospheric energy budget studies over sea ice, a Monte Carlo model is used to investigate three-dimensional radiative transfer over a highly inhomogeneous surface albedo involving open water, sea ice, and melt ponds. The model simulates the spatial variability in 550-nm downwelling irradiance and albedo that a UAV would measure above this surface and underneath an optically thick, horizontally homogeneous cloud. At flight altitudes higher than 100 m above the surface, an airborne radiometer will sample irradiances that are greatly smoothed horizontally as a result of photon multiple reflection. If one is interested in sampling the local energy budget contrasts between specific surface types, then the UAV must fly at a low altitude, typically within 20 m of the surface. Spatial upwelling irradiance variability in larger open water features, on the order of 1000 m wide, will remain apparent as high as 500 m above the surface. To fully investigate the impact of surface feature variability on the energy budget of the lower troposphere ice–ocean system, a UAV needs to fly at a variety of altitudes to determine how individual features contribute to the area-average albedo.

Study on integrated farming systems model development

Study on Integrated Farming Systems Model Development was conducted by the Livelihood Improvement of Farming Community in Haor area through System approach Project of the Department of Agronomy, Bangladesh Agricultral University, Mymensigh worked in Purbo Tethulia village of Moahjganj upazilla, Netrakona district from April 2010 to June 2013 with the financial assistance from the National Agricultural Technology Project, SPGR subproject, Bangladesh Agricultural Council with the following objectives i. Increase productivity of field crops, vegetables, livestock and fishes in a household through the use of appropriate technogies and techniques devised/developed/ designed/refined by the farmers for ensuring household food security and nutritional upliftment and raising income ii. Diversify enterprises, mobilize resources and intensify farming and non farming activities for in situ employment generation iii. Conserve farm environment through efficient mobilization and management of natural resource for sustainable production sysyems iv. Develop human resoures for capacity building of the participants and improve their livelihood through system approach. Research programme was finalized in the Bench Mark Survey Workshop. Farmer selection for different research acivities was done as per plan for defferent five components. The crop and agroforestry component conducted experiments both in the homestead land and crop land. In the homestead area, year round vegetables were intervened through community trial for three years. Production of timber trees like mahogany, lambu and fruit trees like mango, guave, jujube, litchi, lemon papaya and jackfruit was also practiced. Timber trees are now at growing stage and among the fruit trees some like papaya, jujube and lemon are at bearing stage. African dhaincha was introduced around homestead fallow/waste land to protect homestead area from wave thrust and to produce biomass fuel. Field trials on rice, vegetables, spices and oil crops were conducted to intensify and diversify the cropping pattern and as well as to utilize the fallow/ waste land of the research site. Under livestock component, experiments were conducted on rearing of egg producing hen, duck, fattening of animals, milching cow, artificial insemination and chemical evaluation of available feedstuffs. A continuous vaccination programme against common diseases of poultry was maintained throughout the study period. Farmers’ response was very positive towards the experimental results. In the fisheries component, experiment on cage culture in open water, perennial and seasonal pond culture, dry fish and pickle were conducted/done. Among the experiments cage culture in open water proved to be a promising technology and fish pickle was highly appreciated in panel test. For the rural hydrology and mechanization component four studies were conducted. The physico-chemical properties of farm land and homestead soils were determined. Additional application of sulphur and zinc fertilizers were found not required. Both the surface and groundwater characteristics were studied. The maximum flood water depth was found around 3.0 m at farm land. Irrigation facilities developed by installing a shallow tubewell (STW) resulted higher crop production and motivated farmers to install four new STWs by their own capital. All the households (462) of Purbo Tethulia were intervened from the project. The interventions were crop, vegetable, livestock, poultry and fish farming. It was observed that as the number of enterprises increased in the farming systems, the income also increased. The evidence also showed that the training of the beneficiaries increased their knowledge and skill.J. Bangladesh Agril. Univ. 12(2): 325-336, December 2014

Retrieval of Melt Ponds on Arctic Multiyear Sea Ice in Summer from TerraSAR-X Dual-Polarization Data Using Machine Learning Approaches: A Case Study in the Chukchi Sea with Mid-Incidence Angle Data

Melt ponds, a common feature on Arctic sea ice, absorb most of the incoming solar radiation and have a large effect on the melting rate of sea ice, which significantly influences climate change. Therefore, it is very important to monitor melt ponds in order to better understand the sea ice-climate interaction. In this study, melt pond retrieval models were developed using the TerraSAR-X dual-polarization synthetic aperture radar (SAR) data with mid-incidence angle obtained in a summer multiyear sea ice area in the Chukchi Sea, the Western Arctic, based on two rule-based machine learning approaches—decision trees (DT) and random forest (RF)—in order to derive melt pond statistics at high spatial resolution and to identify key polarimetric parameters for melt pond detection. Melt ponds, sea ice and open water were delineated from the airborne SAR images (0.3-m resolution), which were used as a reference dataset. A total of eight polarimetric parameters (HH and VV backscattering coefficients, co-polarization ratio, co-polarization phase difference, co-polarization correlation coefficient, alpha angle, entropy and anisotropy) were derived from the TerraSAR-X dual-polarization data and then used as input variables for the machine learning models. The DT and RF models could not effectively discriminate melt ponds from open water when using only the polarimetric parameters. This is because melt ponds showed similar polarimetric signatures to open water. The average and standard deviation of the polarimetric parameters based on a 15 × 15 pixel window were supplemented to the input variables in order to consider the difference between the spatial texture of melt ponds and open water. Both the DT and RF models using the polarimetric parameters and their texture features produced improved performance for the retrieval of melt ponds, and RF was superior to DT. The HH backscattering coefficient was identified as the variable contributing the most, and its spatial standard deviation was the next most contributing one to the classification of open water, sea ice and melt ponds in the RF model. The average of the co-polarization phase difference and the alpha angle in a mid-incidence angle were also identified as the important variables in the RF model. The melt pond fraction and sea ice concentration retrieved from the RF-derived melt pond map showed root mean square deviations of 2.4% and 4.9%, respectively, compared to those from the reference melt pond maps. This indicates that there is potential to accurately monitor melt ponds on multiyear sea ice in the summer season at a local scale using high-resolution dual-polarization SAR data.

Enhancement and monitoring of pollutant removal in a constructed wetland by microbial electrochemical technology

A bench-scale constructed wetland combined with microbial electrochemical technology (MET-CW) was run for 400days with groundwater contaminated with benzene, methyl-tert-butyl ether (MTBE), and ammonium (NH4+). Four vertically stacked anode modules were embedded into a sand bed and connected with a stainless steel cathode placed in an open water pond. In the zone of presence of anode modules, significantly more benzene and MTBE were removed in the MET-CW compared to the control CW without MET in the first 150 operation days. Benzene was identified as primary electron donor at the anode. Benzene removal and current densities were linearly correlated, implying the potential of the system for electrochemically monitoring benzene biodegradation. Compound-specific isotope analysis (CSIA) indicated that benzene was initially activated by monohydroxylation forming intermediates which were subsequently oxidized accompanied by extracellular electron transfer, leading to current production. NH4+ removal was not stimulated by MET.

Using beaver works to estimate colony activity in boreal landscapes

ABSTRACTBeaver ponds and beaver‐impounded vegetation are indicators of past or present beaver activity that can be detected from aerial photography. A method to quantitatively relate these beaver works with the density of active beaver colonies could benefit beaver management, particularly in areas lacking beaver population data. We compared historical maps (1961–2006) of beaver works at Voyageurs National Park, Minnesota, USA with concurrent aerial surveys of beaver colonies. We tested 2 landscape‐scale models of beaver colony density previously developed for a period of beaver population expansion (1940–1986), but they failed to predict colony density after 1986, a period of declining beaver population. We developed a new landscape‐scale regression, calculating that 2.15% of the landscape would be flooded by every 100 additional beaver colonies (R2 = 0.53, P = 0.027). Classification tree analysis of individual pond sites showed that open water pond and impounded marsh area were the primary predictors of beaver colony presence or absence, but that the classification trees were far better at identifying inactive sites (>93% correct) than active sites (35–38% correct). The area of open water in beaver ponds is a good but not perfect indicator of beaver activity that can be used by wildlife managers as a landscape‐scale indicator of beaver colony density. Published 2015. This article is a U.S. Government work and is in the public domain in the USA.

Tidal day organic and inorganic material flux of ponds in the Liberty Island freshwater tidal wetland.

The loss of inorganic and organic material export and habitat produced by freshwater tidal wetlands is hypothesized to be an important contributing factor to the long-term decline in fishery production in San Francisco Estuary. However, due to the absence of freshwater tidal wetlands in the estuary, there is little information on the export of inorganic and organic carbon, nutrient or phytoplankton community biomass and the associated mechanisms. A single-day study was conducted to assess the potential contribution of two small vegetated ponds and one large open-water pond to the inorganic and organic material flux within the freshwater tidal wetland Liberty Island in San Francisco Estuary. The study consisted of an intensive tidal day (25.5 h) sampling program that measured the flux of inorganic and organic material at three ponds using continuous monitoring of flow, chlorophyll a, turbidity and salt combined with discrete measurements of phytoplankton community carbon, total and dissolved organic carbon and nutrient concentration at 1.5 h intervals. Vegetated ponds had greater material concentrations than the open water pond and, despite their small area, contributed up to 81% of the organic and 61% of the inorganic material flux of the wetland. Exchange between ponds was important to wetland flux. The small vegetated pond in the interior of the wetland contributed as much as 72–87% of the total organic carbon and chlorophyll a and 10% of the diatom flux of the wetland. Export of inorganic and organic material from the small vegetated ponds was facilitated by small-scale topography and tidal asymmetry that produced a 40% greater material export on ebb tide. The small vegetated ponds contrasted with the large open water pond, which imported 29–96% of the inorganic and 4–81% of the organic material into the wetland from the adjacent river. This study identified small vegetated ponds as an important source of inorganic and organic material to the wetland and the importance of small scale physical processes within ponds to material flux of the wetland.

Development of a Natural Treatment System for Stream Water Purification: Mechanisms and Environmental Impacts Evaluation

AbstractA constructed wetland type natural treatment system was built in southern Taiwan for stream water purification and natural habitat creation. The system influent (influent rate = 1,170 m3/d) was from the local stream containing secondary wastewater from hog farms. The system included a fully vegetated free-water surface basin, followed by an open-water pond, a second fully vegetated free water surface basin, and an eco-pond with isolated islands for natural habitat creation. The hydraulic loading rate, hydraulic retention time, water depth, and total volume of the wetland system were 0.27 m/d, 7.5 d, 0.64 m, and 7,800 m3, respectively. In this study, surface water, sediment, and groundwater samples were collected and analyzed quarterly for each basin during the two-year investigation period. The results show that the overall removal efficiencies for biochemical oxygen demand, total nitrogen, total phosphorus, and total coliform were 71, 85, 82, and 75%, respectively. The calculated first-order d...

Fate of pharmaceuticals in a subsurface flow constructed wetland and two ponds

Removal and fate of 18 pharmaceuticals of different compound classes and 11 human metabolites were investigated in a subsurface flow constructed wetland (SSF), a pond and a pond with floating plants. Equal in surface area and flow rate, they functioned as the advanced treatment stage following conventional biological wastewater treatment in a municipal wastewater treatment plant equipped for nutrient removal. The influent and the effluents of the three treatment wetlands were measured in two studies during summer and one study during winter. The influence of the treatment design and the inherent environmental conditions (redox potential and irradiation) on the range of compounds removed as well as on the removal efficiency was investigated. This field-site study was accompanied by an in situ degradation experiment to assess the influence of photodegradation and biodegradation on the overall removal of pharmaceuticals.In total, 13 compounds (diclofenac, 3-hydroxycarbamazepine (3-OH-CBZ), venlafaxine (VLX), O-desmethylvenlafaxine (O-DM-VLX), tramadol (TMD), trimethoprim, erythromycin, clarithromycin, metoprolol, atenolol, bezafibrate, acyclovir and codeine) were consistently removed in quantities more than 70% in at least one of the treatment systems during summer. In the open water pond, photodegradation was found to be an important process for the removal of diclofenac, O-desmethyltramadol (O-DM-TMD), O-DM-VLX as well as 2-hydroxycarbamazepine (2-OH-CBZ) and 3-OH-CBZ. In contrast to the field-site study, no removal of target compounds by biodegradation was observed in the in situ degradation experiments without sediment additions except for metoprolol. This suggests that biodegradation of most substances is improved by the presence of microbially active surfaces such as those provided by the sediment in the pond and, to a higher extent, by the filter passage in the SSF.Low redox conditions (absence of nitrate) within the SSF and the pond with floating plants in summer were favourable for the anaerobic degradation of some compounds that are aerobically quite persistent, such as sulfamethoxazole (SMX) and diatrizoate. During winter, the increase of redox conditions (presence of oxygen) in the SSF consistently led to an enhanced removal of aerobically degradable compounds such as iopromide. In contrast, the removal of the target pharmaceuticals in the open water pond was generally lower during winter. This could be attributed to a decrease of photodegradation and biodegradation due to the lower global radiation and microbial activity, respectively.Based on the conclusion drawn from the influence of constructed wetland design and season on the compound specific removal, a hybrid constructed wetland is suggested. The combination of an inundated SSF followed by a shallow open water pond would steadily remove a wide range of aerobically degradable pharmaceuticals throughout the year. Additionally during summer, the open water pond would allow for photodegradation and the SSF for partial degradation of anaerobically degradable pharmaceuticals.

Autonomous observations of solar energy partitioning in first-year sea ice in the Arctic Basin

A Spectral Radiation Buoy (SRB) was developed to autonomously measure the spectral incident, reflected, and transmitted spectral solar radiation (350-800 nm) above and below sea ice. The SRB was deployed on drifting first-year sea ice near the North Pole in mid-April 2012, together with velocity and ice mass balance buoys. The buoys drifted southward and reached Fram Strait after approximately 7 months, covering a complete melt season. At the SRB site, snowmelt started on 10 June, and had completely disappeared by 14 July. Surface albedo was above 0.85 until snowmelt onset and decreased rapidly with the progression of snowmelt. Albedo was lowest on 14 July, when the observed surface was likely a mixture of bare ice and melt pond(s). The transmitted irradiance measured under the ice was largest in July, with a monthly average of 20 W m(-2), compared to <0.3 W m(-2) premelt. Under-ice irradiance peaked on 19-20 July, with a daily average around 35 W m(-2). From mid-April to mid-September, the solar energy transmitted through the ice into the ocean contributed about two-thirds of the energy required for the observed bottom melt (0.49 m). The energy absorbed by the ice after snowmelt was enough to melt an additional 0.1 m of ice. Solar energy incident on open water and melt ponds provided significant additional heating, indicating solar heating could explain all of the observed bottom melt in this region in summer 2012.