This study reports a systematic assessment of treatment efficacy for 15 pilot-scale subsurface flow constructed wetlands of different designs for CBOD5, TSS, TOC, TN, NH4-N, NO3-N, NO2-N, and E. coli ...over the course of one year in an outdoor study to evaluate the effects of design and plants. The systems consisted of a range of designs: horizontal flow (HF) with 50 and 25 cm depth, unsaturated vertical flow (VF) with sand or fine gravel, and intensified systems (horizontal and saturated vertical flow with aeration, and reciprocating fill and drain). Each system was built in duplicate: one was planted with Phragmites and one was left unplanted (with the exception of the reciprocating system, of which there was only one and it was unplanted). All systems were fed with the same primary-treated domestic wastewater. Effluent concentrations, areal and volumetric mass removal rates, and percent mass removal for the 15 systems are discussed. HF wetlands removed CBOD5, TSS, TN, NH4-N and E. coli by 73–83%, 93–95%, 17–41%, 0–27% and 1.5 log units, respectively. Unsaturated VF and aerated VF wetlands removed CBOD5, TSS, TN, NH4-N and E. coli by 69–99%, 76–99%, 17–40%, 69–99% and 0.9–2.4 log units, respectively. The aerated HF and reciprocating systems removed CBOD5, TSS, TN, NH4-N and E. coli by 99%, 99%, 43–70%, 94–99% and 3.0–3.8 log units, respectively. The aerated HF and reciprocating systems achieved the highest TN removal rate of all of the designs. Design complexity clearly enhanced treatment efficacy (HF < VF < Intensified, p < 0.001) during the first two years of plant growth while the presence of plants had minor effects on TN and NH4-N removal in the shallow HF design only.
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•15 pilot-scale treatment wetlands were compared side-by-side in an outdoor study.•Pollutant removal rates increase with design complexity (HF < VF < Intensified).•Plants had only minor effects on removal rates over the first two growing seasons.•Volumetric mass removal rates should be used as an indicator of treatment efficacy.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Wetlands play an important role in reducing the impact of nitrogen pollution on natural aquatic environments. However, during the plant wilting period (winter) there will inevitably be a reduction in ...nitrogen removal from wetlands. Understanding optimum harvest time will allow the use of management practices to balance the trade-off between nitrogen removal and the sustainability of wetlands. In this study, we investigated wetland nitrogen removal and reed (Phragmites australis) nutrient responses for two years first year: influent total nitrogen (TN) 17.6–34.7 mg L−1; second year: influent TN 3.2–10.0 mg L−1 to identify the optimal harvest time: before wilting, mid-wilting, or late wilting. Harvesting decreased wetland nitrogen removal in both years, with later harvest time producing a smaller decrease in TN and ammonium-nitrogen (NH4+–N) removal. In addition to harvest before wilting, aboveground reed harvest at mid-wilting harvested more nutrients carbon (C) 7.9%, nitrogen (N) 46.6% and phosphorus (P) 43.6% in the first year, while harvest at late wilting harvested more nutrients (C 4.9%, N 7.8% and P 24.1%) in the second year, although this was not statistically significant. The late wilting harvest caused fewer disturbances to root stoichiometric homeostasis in the first year, while mid-wilting harvest promoted root nutrient availability in the second year. In addition, redundancy analysis (RDA) showed that root stoichiometry was interrelated with wetland nitrogen removal. Our results suggest that optimal harvest time was late wilting on the basis of wetland nitrogen removal, or either mid- or late wilting according to reed nutrient response to influent nitrogen concentration in some years. Our results provide crucial information for winter wetlands management.
•Later harvest times had less impact on wetland TN and NH4+–N removal.•Mid- or late-wilting harvest should be selected according to reed nutrient response.•Root stoichiometric characteristics were related to wetland nitrogen removal.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•Build an UAV-based reed aboveground biomass (AGB) model by introducing canopy height.•Propose a way to obtain ample reed AGB samples matched with satellite pixel.•Develop a reed AGB satellite-based ...model and map the AGB in Nandagang Wetland.
Phragmites australis (common reed) is a widely distributed emergent aquatic vegetation species in many wetland ecosystems, and its aboveground biomass (AGB) is an important parameter for evaluating the carbon–nitrogen cycle in wetlands. Satellite remote sensing (RS) is a powerful tool used to monitor the spatio-temporal distribution of AGB within reedbeds over a large area. However, when building AGB models based on satellite data, especially medium resolution satellites, it is difficult to obtain ample and properly measured AGB samples which can be matched with image pixels due to the inaccessibility of the wetlands. In this study, we proposed a solution based on the unmanned aerial vehicle (UAV) and Sentinel-2 data, which allowed us to estimate and successfully map the AGB of Phragmites australis in the Nan Da Gang Wetland Reserve (NDG) in China’s Hebei Province close to the Bohai sea. First, in an experimental area (EA) of NDG, an AGB model (R2 = 0.74, RMSE = 174 g/m2) was built based on NDVI(534, 734) and canopy height derived from UAV data, and an AGB map was obtained of the EA. Second, the AGB map was resampled to the pixel of the Sentinel-2 image, and an AGB sample set was matched with the acquired spatial resolution of the Sentinel-2 image. Finally, based on the sample set, an AGB model (R2 = 0.59, RMSE = 194 g/m2) was built using RVI derived from the Sentinel-2 image, which allowed us to map the Phragmites australis AGB in the NDG wetland reedbed. The study illustrated well that a UAV can be proficient in obtaining enough AGB samples matched with satellite pixels to build satellite-based AGB estimation models.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Soil salinization is one of the most severe environmental problems restricting biodiversity maintenance and ecosystem functioning in a coastal wetland. Recent studies have well documented how ...salinization affects soil microbial communities along vegetation succession of coastal wetlands. However, the salinity effect is rarely assessed in the context of plant intraspecific variation. Here, we analyzed the soil bacterial and fungal communities of Phragmites australis wetland using amplicon high-throughput sequencing at a fine scale (within 1000 m) in the Yellow River Delta. Our results revealed that microbial diversity is significantly correlated to soil salinity (assessed as electrical conductivity, EC) but not to soil nutrients (N and P content) or plant intraspecific traits (leaf length, shoot height, and neutral genetic variation). Specifically, the microbial diversity tended to decrease with increased EC, and the bacterial community was more sensitive to EC change than the fungal community. The dominant bacterial phyla were Proteobacteria, Actinobacteria, and Chloroflexi, and the dominant fungal phyla were Ascomycota, Basidiomycota, and Mortierellomycota. The relative abundance of Actinobacteria was significantly negatively correlated to EC, while Proteobacteria were positively correlated to EC. In high salinity (> 1 mS/cm), the role of the stochastic processes became more important in community assembly according to habitat niche breadth estimation, neutral community model, C-score metric, and normalized stochasticity ratio. Additional common garden and microcosm experiments provided evidence that the genotype effect of P. australis on soil microbiome might only occur between lineages from different regions but not from the same region like the Yellow River Delta. Our findings provide new insights into soil microbial community assembly processes with the intraspecific variation of host plants in the wetland ecosystem and offer a scientific reference for salinity mitigation and vegetation management of coastal wetlands under future global changes.
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•Salinity selection, not dispersal limitation, shapes soil microbial diversity.•Soil bacteria are more sensitive to salinity than fungi across a small space.•Soil microbiome is correlated to plant genetic variation among regions but not within regions.•Deterministic processes dominate microbial community assembly in a low-salinity range.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•Amount of heavy metals in plant tissue in constructed wetlands is highly variable.•Heavy metals in aboveground plant tissue may represent up to 60% of the inflow load.•Heavy metals in plant tissue ...may represent a large part of the removed elements.•The highest accumulation in aboveground plant tissues was observed for zinc.
Wastewater treatment in constructed wetlands is a biotechnological process which has been used for more than five decades for wastewater treatment. It is generally agreed that plants are important part of the treatment system, however, the direct role of plants is usually restricted to plant uptake of nutrients and heavy metals. The purpose of this study was to evaluate the amount of heavy metals sequestered in the aboveground biomass of Phragmites australis and thus, available for harvest and removal. The survey revealed that the amount of heavy metals accumulated in the aboveground plant biomass (aboveground standing stock) represents often only small fraction of the inflow annual load but in some studies, this fraction is quite high, especially for zinc (up to 59%), more rarely for cadmium (55%) and chromium (38%). The amount of heavy metals sequestered in the plant shoots as a fraction of total removed heavy metal in the constructed wetland is variable with values as high as 71% for cadmium, 55% for chromium or 49% for zinc in some studies. However, there is still a large gap in our knowledge on heavy metal accumulation in aboveground tissues, namely the conditions that would promote heavy metal uptake and subsequent translocation to aboveground biomass.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Biochar addition can enhance plant growth and change soil physicochemical properties in saline soil. However, it is unclear whether the positioning of biochar additions (e.g., rhizosphere addition ...and surface addition) alters such impacts and whether such positioning effects interact with salinity levels. In the Yellow River Delta, China, we carried out a field experiment in which biochar was not added (control) or was added to the soil surface (surface addition) or to the soil at the rhizosphere position (rhizosphere addition) of Phragmites australis in three sites with different salt levels (1‰ - low, 5‰ - medium and 10‰ - high). Rhizosphere addition of biochar significantly improved the growth of P. australis, especially its fine root mass. Both rhizosphere addition and surface addition of biochar significantly decreased nitrate nitrogen content and electrical conductivity, and the inhibitory effects were more effective at the sites with medium and high salt levels in 2018. Structural equation modeling showed that biochar addition could directly increase the fine root mass of P. australis by decreasing the soil electrical conductivity, further improving the total mass of P. australis. Overall, rhizosphere addition of biochar is a better choice for improving the productivity of P. australis in saline soil and is beneficial to P. australis wetland restoration in the Yellow River Delta. Long-term field research is needed to better understand the effect and mechanism of biochar application.
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•Rhizosphere addition of biochar increased biomass of Phragmites australis.•Rhizosphere addition and surface addition of biochar decreased soil NO3−-N and EC.•The inhibition effects were more effective in medium and high salt levels in 2018.•Biochar addition could increase biomass of P. australis via decreasing soil EC.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
In recent years, ecologists have experienced an increased awareness of the importance of plant-environment interactions. Studies have demonstrated that spatial ecosystem heterogeneity and ...availability of resources influence plant growth. Understanding the ecological response characteristics of plants and environmental laws influencing arid land vegetation in different water-salt environments should be quite valuable to scientists. To better understand the ecological characteristics of plants and factors that potentially control them such as water availability and salinity in arid regions, we conducted a study in Phragmites australis in dry habitats of the Yutian Oasis along the Kenya River, in the southern marginal zones of the Tarim Basin, Xinjiang, China. The redundancy analysis can effectively reveal relationships between ecological characteristics of plants and water-salt indicators. The characteristics of Phragmites australis deserve more research, especially research related to the microscopic physiolog
Constructed wetlands serve as an eco-friendly solution for treating landfill leachate, leading to reduced energy use, economic savings, and less environmental harm. A novel study in the cold climate ...of western Iran has examined the effectiveness of Phragmites australis, also known as common reed, in a pilot-scale project. The study focused on the reed's capacity to bioaccumulate and translocate heavy metals within a horizontal subsurface flow constructed wetland. The findings revealed significant removal rates for heavy metals such as Fe, Mn, Cd, Cr, Ni, and Pb, with efficiencies of 81.23 %, 76.02 %, 26.92 %, 44.73 %, 20.13 %, and 28.24 % respectively. The bioaccumulation factor for these metals was above 1.0, signifying effective uptake by the plant. However, the translocation factor for all metals, except for Mn, did not exceed 1.0. This indicates that although Phragmites australis is an effective phytostabilizer, effectively sequestering heavy metals in its root system, it is not adept at moving these metals to its aboveground tissues. Rather, it tends to concentrate them within its roots and rhizomes.
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•Constructed wetlands to treat landfill leachate reduce energy consumption and economic costs.•The bioaccumulation factor of Phragmites australis for heavy metals (Fe, Mn, Cd, Cr, Ni, and Pb) exceeded 1.0.•The translocation factor of Phragmites australis for Fe, Cd, Cr, Ni, and Pb was <1.0, and for Mn was >1.0.•Phragmites australis can be a relatively suitable phytostabilizer for heavy metals (Fe, Mn, Cd, Cr, Ni, and Pb).
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Both biochar and arbuscular mycorrhizal fungi (AMF) can affect plant growth, but little is known about how the interaction between biochar and AMF affects greenhouse gas emissions from plant-soil ...systems. We tested the hypotheses that biochar and AMF can interact to affect greenhouse gas emissions due to promoted plant biomass and changed soil N availability. We assembled microcosms, each initially grown with three ramets (vegetative individuals) of a clonal, wetland plant Phragmites australis, with or without AMF in soil and with or without biochar addition to soil. Biochar addition alone and AMF presence alone both significantly enhanced biomass of P. australis, but such effects became weaker when they were present simultaneously. The presence of AMF significantly decreased concentrations of chlorophyll and nitrogen (N) in P. australis and concentrations of NH4+-N, NO3−-N, inorganic N and total N in soil, but such effects became weaker when biochar was added to soil than when it was not. Biochar addition significantly increased concentrations of chlorophyll and N in P. australis when AMF were present, but had little impact when AMF were absent. The presence of AMF increased CO2 emission and CO2 equivalent independent of biochar addition. The presence of AMF also increased N2O emission when biochar was added, but decreased it when biochar was not added. We conclude that biochar addition and AMF presence can interact to affect plant growth and N uptake, soil N availability and greenhouse gas emissions from plant-soil ecosystems.
•Biochar and AMF interactively affect plant growth, soil N and N2O emission.•Biochar and AMF significantly enhanced biomass of P. australis.•AMF significantly decreased soil inorganic N, especially when biochar addition.•AMF increased CO2 emission and CO2 equivalent independent of biochar addition.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
