Investigating the effect of hydraulic residence time, artificial aeration and plants presence on different constructed wetland designs treating oil industry effluent.

Constructed Wetlands (CW) have gained popularity over the last decades due to their cost-effectiveness, easy and simple operation and environmental compatibility in wastewater treatment. This ecological engineering technology appears particularly ideal for low-income regions. In this study, three widely used CW types (horizontal flow, vertical flow, and hybrid CW) were constructed and evaluated for their effectiveness in removing various pollution parameters (BOD5, COD, TSS, NH4-N, NO3-N, and TP) from an industrial effluent. Different configurations were tested such as CW type, hydraulic residence time, plants presence, and artificial aeration. Results showed that the hybrid CW configuration (i.e., vertical flow CW followed by horizontal subsurface flow CW) achieved the highest removal rates of all pollutants, i.e., more than 90% of BOD5, COD, TSS, and NH4-N. The single horizontal flow and vertical flow CW designs showed variations in the removal of NO3-N and TP (less than 30%), which were significantly improved (50% and 70%, respectively) by using the hybrid CW system. Artificial aeration significantly improves the performance of the CW system, especially for ammonia nitrogen and organic matter removal, while plants presence is also beneficial in the treatment performance. An 8-days HRT seems to be adequate for high removal rates in passive CW designs, though in aerated wetlands a lower HRT of 4 days seems sufficient. These findings suggest that the hybrid CW system could be a promising option for efficient wastewater treatment in developing regions.

Constructed wetlands and hyperaccumulators for the removal of heavy metal and metalloids: A review.

Water pollutions of heavy metal and metalloids (HMMs), typically including As, Cd, Cu, Cr, Mn, Ni, Pb, and Zn, are becoming a severe environmental problem to be controlled. Constructed wetlands (CWs) have been intensively investigated and applied for the removal of HMMs. By analyzing a mass of data from the existing literatures, this review found that the HMM removals in CWs varied from 12.35 % to 91.01 %, depending upon the HMM species and CW conditions. Nonetheless, 88.50 % of the influent HMMs were eventually immobilized in the CW sediments, while the common wetland plants are inefficient (i.e., accounting for 4.64 %) to uptake and accumulate the HMMs. It was also found that the concentrations of certain HMMs in the CW sediments have already exceeded up to 100 % of various environmental standards, indicating the urgency of introducing HMM hyperaccumulators in the systems. Through comparison, both the aboveground and belowground HMM accumulating capacities of reported hyperaccumulators were higher by magnitudes than common wetland plants. Following this, the efficacies and mechanisms of candidate hyperaccumulators were provided for the various scenarios of HMM control in CWs. Further, the selection principals, culture methods, and harvest strategies of hyperaccumulator in CWs were discussed. Finally, several perspectives were suggested for the future research. Overall, this review provided guiding information for the utilization of hyperaccumulators in CWs, which can improve the efficiency and sustainability of HMM removal in the CW systems.

A novel combination of wetland plants (Eichhornia crassipes) and biochar derived from palm kernel shells modified with melamine for the removal of paraquat from aqueous medium: a green and sustainable approach.

Herbicide contamination in aquatic systems has become a global concern due to their long- term persistence, accumulation and health risks to humans. Paraquat, a widely used and cost-effective nonselective herbicide, is frequently applied in agricultural fields for pest control. Consequently, the removal of paraquat from contaminated water is crucial. This research presents a sustainable and environmentally benign method for paraquat removal from aqueous system by integrating wetland plants (Eichhornia crassipes) with biochar derived from melamine-modified palm kernel shells. The prepared biochar was characterized by using various analytical techniques. The effectiveness of biochar in enhancing phytoremediation was evaluated through a series of experiments, showing significant paraquat removal efficiencies of 99.7, 98.3, and 82.8% at different paraquat concentrations 50, 100, and 150 mg L-1, respectively. Additionally, present study examined the impact of biochar on the growth of E. crassipes, highlighting its potential to reduce the toxic effects of paraquat even present at higher concentrations. The paraquat removal mechanism was elucidated, focusing on the synergistic role of biochar adsorption and phytoremediation capability of E. crassipes. This innovative approach is an effective, feasible, sustainable and eco-friendly technique that can contribute to the development of advanced and affordable water remediation processes for widespread application.

The novelty of this study lies in the implementation of combined approach by phytoremediation with biochar modified with melamine. This study highlighted synergistic integration of two concurrent systems. The biochar generated from waste palm kernel shells played a pivotal role in facilitating the plants' survival and resilience against the paraquat toxicity, rather than succumbing to its deleterious effects. This research delineates a robust methodology for the elimination of emerging pollutants, offering researchers a platform to make pioneering advancements in this scientific field for sustainable future.

Unraveling phytoremediation mechanisms of the common reed (Phragmites australis) suspension cells towards ciprofloxacin: Xenobiotic transformation and metabolic reprogramming.

Phytoremediation is an effective solution to treat pollution with antibiotic compounds in aquatic environments; however, the underlying mechanisms for plants to cope with antibiotic pollutants are obscure. Here we used cell suspension culture to investigate the distribution and transformation of ciprofloxacin (CIP) in common reed (Phragmites australis) plants, as well as the accompanying phenotypic and metabolic responses of plants. By means of radioactive isotope labelling, we found that in total 68 % of CIP was transformed via intracellular Phase I transformation (reduction and methylation), Phase Ⅱ conjugation (glycosylation), and Phase Ⅲ compartmentalization (cell-bound residue formation mainly in cell walls, 23 %). The reduction and glycosylation products were secreted by the cells. To mitigate stress induced by CIP and its transformation products, the cells activated the defense system by up-regulating both intra- and extra-cellular antioxidant metabolites (e.g., catechin, l-cystine, and dehydroascorbic acid), anti-C/N metabolism disorder metabolites (e.g., succinic acid), secreting signaling (e.g., nicotinic acid), and anti-stress (e.g., allantoin) metabolites. Notably, the metabolic reprogramming could be involved in the CIP transformation process (e.g., glycosylation). Our findings reveal the strategy of wetland plants to cope with the stress from CIP by transforming the xenobiotic compound and reprogramming metabolism, and provide novel insights into the fate of antibiotics and plant defense mechanisms during phytoremediation.

Large-scale geographic patterns and environmental and anthropogenic drivers of wetland plant diversity in the Qinghai-Tibet Plateau.

BACKGROUND: The geographic patterns of plant diversity in the Qinghai-Tibet Plateau (QTP) have been widely studied, but few studies have focused on wetland plants. This study quantified the geographic patterns of wetland plant diversity in the QTP through a comprehensive analysis of taxonomic, phylogenetic and functional indices. METHODS: Based on a large number of floras, monographs, specimens and field survey data, we constructed a comprehensive dataset of 1,958 wetland plant species in the QTP. Species richness (SR), phylogenetic diversity (PD), functional diversity (FD), net relatedness index (NRI) and net functional relatedness index (NFRI) were used to assess the taxonomic, phylogenetic and functional diversity of wetland plants. We explored the relationships between the diversity indices and four categories of environmental variables (i.e. energy-water, climate seasonality, topography and human activities). We used four diversity indices, namely endemic species richness, weighted endemism, phylogenetic endemism and functional endemism, together with the categorical analysis of neo- and paleo-endemism (CANAPE), to identify the endemic centers of wetland plants in the QTP. RESULTS: SR, PD and FD were highly consistent and showed a decreasing trend from southeast to northwest, decreasing with increasing elevation. The phylogenetic structure of wetland plant assemblages in most parts of the plateau is mainly clustered. The functional structure of wetland plant assemblages in the southeast of the plateau is overdispersed, while the functional structure of wetland plant assemblages in other areas is clustered. Energy-water and climate seasonality were the two most important categories of variables affecting wetland plant diversity. Environmental variables had a greater effect on the functional structure of wetland plants than on the phylogenetic structure. This study identified seven endemic centres, mainly in the Himalayas and Hengduan Mountains. CONCLUSIONS: Climate and topography are the main factors determining the geographic distribution of wetland plant diversity at large scales. The majority of grid cells in the QTP with significant phylogenetic endemism were mixed and super-endemism. At large scales, compared to climate and topography, human activities may not have a negative impact on wetland plant diversity in the QTP.

Superoxide Photoproduction from Wetland Plant-Derived Dissolved Organic Matter: Implications for Biogeochemical Impacts of Plant Invasion.

Although the impacts of exotic wetland plant invasions on native biodiversity, landscape features, and carbon-nitrogen cycles are well appreciated, biogeochemical consequences posed by ecological competition, such as the heterogeneity of dissolved organic matter (DOM) from plant detritus and its impact on the formation of reactive oxygen species, are poorly understood. Thus, this study delves into O2•- photogeneration potential of DOM derived from three different parts (stem, leaf, and panicle) of invasive Spartina alterniflora (SA) and native Phragmites australis (PA). It is found that DOM from the leaves of SA and the panicles of PA has a superior ability to produce O2•-. With more stable aromatic structures and a higher proportion of sulfur-containing organic compounds, SA-derived DOM generally yields more O2•- than that derived from PA. UVA exposure enhances the leaching of diverse DOM molecules from plant detritus. Based on the reported monitoring data and our findings, the invasion of SA is estimated to approximately double the concentration of O2•- in the surrounding water bodies. This study can help to predict the underlying biogeochemical impacts from the perspective of aquatic photochemistry in future scenarios of plant invasion, seawater intrusion, wetland degradation, and elevated solar UV radiation.

Root and shoot phenology, architecture, and organ properties: an integrated trait network among 44 herbaceous wetland species.

Integrating traits across above- and belowground organs offers comprehensive insights into plant ecology, but their various functions also increase model complexity. This study aimed to illuminate the interspecific pattern of whole-plant trait correlations through a network lens, including a detailed analysis of the root system. Using a network algorithm that allows individual traits to belong to multiple modules, we characterize interrelations among 19 traits, spanning both shoot and root phenology, architecture, morphology, and tissue properties of 44 species, mostly herbaceous monocots from Northern Ontario wetlands, grown in a common garden. The resulting trait network shows three distinct yet partially overlapping modules. Two major trait modules indicate constraints of plant size and form, and resource economics, respectively. These modules highlight the interdependence between shoot size, root architecture and porosity, and a shoot-root coordination in phenology and dry-matter content. A third module depicts leaf biomechanical adaptations specific to wetland graminoids. All three modules overlap on shoot height, suggesting multifaceted constraints of plant stature. In the network, individual-level traits showed significantly higher centrality than tissue-level traits do, demonstrating a hierarchical trait integration. The presented whole-plant, integrated network suggests that trait covariation is essentially function-driven rather than organ-specific.

The uptake, transportation, and chemical speciation of Sb(III) and Sb(V) by wetland plants Arundinoideae (Phragmites australis) and Potamogetonaceae (Potamogeton crispus).

Antimony (Sb) is increasingly released and poses a risk to the environment and human health. Antimonite (Sb(III)) oxidation can decrease Sb toxicity, but the current knowledge regarding the effects of Sb(III) and antimonate (Sb(V)) exposure is limited to wetland plants, especially the Sb speciation in plants. In this study, Phragmites australis and Potamogeton crispus were exposed to 10 and 30 mg/L Sb(III) or Sb(V) for 20 days. The total concentration, subcellular distribution, and concentration in the iron plaque of Sb were determined. The Sb speciation in plants was analyzed by HPLC-ICP-MS. It illustrated that Sb(III) exposure led to more Sb accumulation in plants than Sb(V) treatments, with the highest Sb concentration of 405.35 and 3218 mg/kg in Phragmites australis and Potamogeton crispus, respectively. In the subcellular distribution of Sb, accumulation of Sb mainly occurred in cell walls and cell cytosol. In Phragmites australis, the transport factor in the Sb(V) treatments was about 3 times higher than the Sb(III) treatments, however, it was lower in the Sb(V) treatments than Sb(III) treatments for Potamogeton crispus. Sb(V) was detected in the plants of Sb(III) treatments with different Sb(V)-total Sb vitro (Phragmites australis: 34 % and, Potamogeton crispus: 15 %), moreover, Sb(V) was also detected in the nutrient solution of Sb(III) treatments. Antimony exposure caused a reduction of the iron plaque formation, at the same time, the root aerenchyma formation was disrupted, and this phenomenon is more pronounced in the Sb(III) treatments. Moreover, the iron plaque has a higher sorption potential to Sb under Sb(III) exposure than that under Sb(V) exposure. The results can fill the gap for antinomy speciation in wetland plants and expand the current knowledge regarding the Sb translocation in wetland systems.

Plant-mediated CH4 exchange in wetlands: A review of mechanisms and measurement methods with implications for modelling.

Plant-mediated CH4 transport (PMT) is the dominant pathway through which soil-produced CH4 can escape into the atmosphere and thus plays an important role in controlling ecosystem CH4 emission. PMT is affected by abiotic and biotic factors simultaneously, and the effects of biotic factors, such as the dominant plant species and their traits, can override the effects of abiotic factors. Increasing evidence shows that plant-mediated CH4 fluxes include not only PMT, but also within-plant CH4 production and oxidation due to the detection of methanogens and methanotrophs attached to the shoots. Despite the inter-species and seasonal differences, and the probable contribution of within-plant microbes to total plant-mediated CH4 exchange (PME), current process-based ecosystem models only estimate PMT based on the bulk biomass or leaf area index of aerenchymatous plants. We highlight five knowledge gaps to which more research efforts should be devoted. First, large between-species variation, even within the same family, complicates general estimation of PMT, and calls for further work on the key dominant species in different types of wetlands. Second, the interface (rhizosphere-root, root-shoot, or leaf-atmosphere) and plant traits controlling PMT remain poorly documented, but would be required for generalizations from species to relevant functional groups. Third, the main environmental controls of PMT across species remain uncertain. Fourth, the role of within-plant CH4 production and oxidation is poorly quantified. Fifth, the simplistic description of PMT in current process models results in uncertainty and potentially high errors in predictions of the ecosystem CH4 flux. Our review suggest that flux measurements should be conducted over multiple growing seasons and be paired with trait assessment and microbial analysis, and that trait-based models should be developed. Only then we are capable to accurately estimate plant-mediated CH4 emissions, and eventually ecosystem total CH4 emissions at both regional and global scales.

First report of Puccinia recondita rust on native jewelweed (Impatiens capensis) in Pennsylvania.

Jewelweed (Impatiens spp., Balsaminaceae) is a common native annual plant within Pennsylvania wetland ecosystems, many of which are under threat from invasive non-native plants, and is an important wetland indicator plant (code FACW; facultative wetland). In May 2014, rust disease symptoms on native jewelweed (Impatiens capensis Meerb.) were observed within a small (0.1 ha) wet area in York County, southeastern Pennsylvania (39.9080648oN, -77.2472024oW). Rust symptoms were noted on most jewelweed plants within the wet area. Foliar symptoms included chlorosis and premature defoliation; infected stems were distorted. Infected leaves and stems contained orange, erumpent aecia with white fragmented peridia (Fig. 1). Symptomatic leaves and stem sections were collected from five infected plants within one small (5 X 5 m) plot in the center of the wet area and taken to the laboratory for microscopic observations and morphological measurements. Mean aecia diameter was 299.2 ± 55.0 µm (n = 60). Aeciospores were single-celled, orange, and generally globose (Fig. 2) with a mean diameter of 24.4 ± 1.4 µm, (n = 60). Disease symptomology and aecia morphology were consistent with Puccinia recondita Dietel & Holw. DNA extraction (from infected stem material), polymerase chain reactions, and DNA sequencing of the 28S region of the nuclear ribosomal DNA repeat was conducted following protocols in Aime (2006) and Aime et al. (2018). The sequence shares 99.34% identity (903 / 909 bp) with P. recondita (BPI 910319) collected in California (KY798399). A voucher specimen has been deposited in the Arthur Fungarium at Purdue University (PUR N24229) with corresponding 28S sequence (GenBank accession OR648406). P. recondita has been reported on native I. capensis in Indiana (Koslow and Clay 2010) and North Carolina (Grand 1985), but not in Pennsylvania to the best of our knowledge (Farr and Rossman 2022). If this rust disease becomes severe on native jewelweeds in Pennsylvania, it may adversely affect our ability to accurately classify native wetlands in the state. In addition, P. recondita is a heteroecious rust that is a major pathogen of grain crops of economic importance (i.e., wheat, barley, oats), which are grown in southeastern Pennsylvania near the infested area. Further research is warranted to understand if native, annual jewelweed can serve as a secondary or alternate host to cause rust disease in major cereal crops.

Beyond a 'just add water' perspective: environmental water management for vegetation outcomes.

Practitioners of environmental water management (EWM) operate within complex social-ecological systems. We sought to better understand this complexity by investigating the management of environmental water for vegetation outcomes. We conducted an online survey to determine practitioners' perspectives on EWM for non-woody vegetation (NWV) in the Murray-Darling Basin, Australia with regards to: i) desirable outcomes and benefits; ii) influencing factors and risks; iii) challenges of monitoring and evaluation, and iv) improving outcomes. Survey participants indicated that EWM aims to achieve outcomes by improving or maintaining vegetation attributes and the functions and values these provide. Our study reveals that EWM practitioners perceive NWV management in a holistic and highly interconnected way. Numerous influencing factors as well as risks and challenges to achieving outcomes were identified by participants, including many unrelated to water. Survey responses highlighted six areas to improve EWM for NWV outcomes: (1) flow regimes, (2) vegetation attributes, (3) non-flow drivers, (4) management-governance considerations, (5) functions and values, and (6) monitoring, evaluation and research. These suggest a need for more than 'just water' when it comes to the restoration and management of NWV. Our findings indicate more integrated land-water governance and management is urgently required to address the impacts of non-flow drivers such as pest species, land-use change and climate change. The results also indicate that inherent complexity in EWM for ecological outcomes has been poorly addressed, with a need to tackle social-ecological constraints to improve EWM outcomes.

Arbuscular Mycorrhizal Fungi Alter Arsenic Translocation Characteristics of Iris tectorum Maxim.

Arsenic (As) pollution in wetlands, mainly as As(III) and As(V), has threatened wetland plant growth. It has been well documented that arbuscular mycorrhizal (AM) fungi can alleviate As stress in terrestrial plants. However, whether AM fungi can protect natural wetland plants from As stress remains largely unknown. Therefore, three hydroponic experiments were conducted in which Iris tectorum Maxim. (I. tectorum) plants were exposed to As(III) or As(V) stresses, to investigate the effects of mycorrhizal inoculation on As uptake, efflux, and accumulation. The results suggested that short-term kinetics of As influx in I. tectorum followed the Michaelis-Menten function. Mycorrhizal inoculation decreased the maximum uptake rate (Vmax) and Michaelis constant (Km) of plants for As(III) influx, while yielding no significant difference in As(V) influx. Generally, mycorrhizal plants released more As into environments after 72 h efflux, especially under As(V) exposure. Moreover, mycorrhizal plants exhibited potential higher As accumulation capacity, probably due to more active As reduction, which was one of the mechanisms through which AM fungi mitigate As phytotoxicity. Our study has revealed the role of aerobic microorganism AM fungi in regulating As translocation in wetland plants and supports the involvement of AM fungi in alleviating plant As stress in anaerobic wetlands.

Release of dissolved organic matter from wetland plants and its interaction with polycyclic aromatic hydrocarbons.

Dissolved organic matter (DOM) derived from wetland plants played a critical role in CWs pollutant migration. This study investigated the character and release pattern of DOM derived from two wetland plants, Phragmites australis and Cladophora sp., and the interaction between DOM with phenanthrene (PHE), benzo(a)pyrene (Bap), and benzo [k]fluoranthene (BkF) under different physical conditions were also studied using spectroscopic techniques. DOM release was related to plant species and withering stage. Humic acid (HA)-like fractions (C3 and C5) were dominated in P. australis (52%) and completely withered Cladophora sp. groups (55%), while protein-like fractions (C1 and C2) dominated in early withered Cladophora sp. groups (52%). Due to the cell and tissue structure difference among plants and their withering stage, DOM derived from early withered P. australis revealed a two-stage slow-fast phase, while other groups were linearly released (R2 0.87207-0.97091). A strong correlation existed between HA-like fractions and water quality index, reflecting the critical influence of plant decay in CWs operation performance. The analysis with Stern-Volmer equation indicated that plant-based DOM interacted with PAHs to form ground state complexes with possible involvement of π-π interaction, hydrogen bonding and cation bridging effect. Aromatic, molecular weight, and hydrophilicity of both DOM and PAHs affected their binding with the interaction capability in the order of BKF > Bap > PHE and C3 > C5 > C2 > C1 > C4. Besides, alkaline environment and high DO condition was highly unsuitable for the combination. Scientific management and appropriate operating condition were important in optimizing operation performance and controlling pollutant migration in CWs.

Helophytes adapt to water and N-enrichment stresses by adjusting and coordinating stoichiometry characteristics in main organs.

Exploring the adaptation strategies of plants under stressful environments from an ecological stoichiometry perspective is a critical but underexplored research topic, and multi-organ collaborative research for multi-species can provide a comprehensive understanding. In this study, helophytes were selected as the subjects, and water depth and water N-enrichment were set as the stressors. A simulation experiment including three water depths (drought stress, control and flooding stress) and four water N-enrichment levels (control, low, medium and high N-enrichment stresses) for six helophyte species was carried out. Overall, C concentrations in all plant organs remained stable under water (drought-flooding stress) and N-enrichment stress. N concentrations increased under both flooding and drought stresses, while P concentrations and the N:P ratio showed an increase and decrease under only flooding stress, respectively. N concentration and N:P ratio increased with water N-enrichment level. The interaction only promoted the accumulation of N concentrations in aboveground organs. Especially, several species also changed organ C concentrations to adapt to water stress and adjusted root N concentrations for the combined stresses of flooding or drought and high N. Leaf and stem were strongly synergistic in N element, and leaf and root were mainly synergistic in P element. Water N-enrichment determined organ element concentrations more than water depth, and species identity dictated organ C:N:P ratios. Our results reveal that the allocation and synergy of nutrients among organs are important adaptive strategies for plants in stressful environments. Meanwhile, increasing water N-enrichment can be an unignored stressor, and species identity should be paid attention as a countermeasure.

Phytotoxic Effects of Tetracycline and its Removal Using Canna indica in a Hydroponic System.

Wetland plants are gaining interest as potential agents for removing emerging contaminants. However, there have been limited studies examining the ability of these plant species to remove antibiotics and their tolerance to stress. This study aimed to investigate the potential of Canna indica, an indigenous wetland plant species in India, for tetracycline-induced oxidative stress, antioxidant activity, and removal of antibiotics from nutrient media and domestic wastewater. Canna indica exhibited a removal rate of approximately 91.05 ± 0.18% for tetracycline in antibiotic containing nutrient media and 87.97 ± 0.39% in domestic wastewater. Notably, the exposure to the drug during the 30 d reaction period led to the accumulation of reactive oxygen species in the plant tissues. Consequently, there was a decline in chlorophyll content, alongside an increase in antioxidant activity, membrane permeability, and K + ion leakage. These findings emphasize the importance of monitoring tolerance levels induced by antibiotics in plant species. Thus, monitoring the antibiotic-induced-tolerance levels in plant species is crucial for maintaining plant health and effectively managing abiotic stress, ensuring efficient recovery and facilitating an effective wetland treatment system.

Effects of plants and soil microorganisms on organic carbon and the relationship between carbon and nitrogen in constructed wetlands.

Constructed wetland is an ideal place for studying the effects of plants and microorganisms on the nutrient cycling and carbon-nitrogen coupling in wetland for their clear background. This study examined both bare plots and others with plants (Phragmites australis or Typha angustifolia) in constructed wetlands and vegetation and soil samples were collected to investigate the effects of plants and soil microorganisms on carbon and nitrogen content. Results showed that the soil organic carbon content was high in plots with high plant biomass, and the increase of soil organic carbon driven by plant biomass was mainly from light fraction organic carbon (LFOC). Correlation analysis and redundancy analysis (RDA) suggested that plants play an important role in the cycle of carbon and nitrogen elements in constructed wetland soils, and that plant nitrogen components were key factors influencing wetland soil carbon and nitrogen. In addition, this study found that most of the main microbial taxa were significantly correlated with dissolved organic carbon (DOC), ammonium nitrogen (NH4+), and nitrate and nitrite nitrogen (NOx-) indicating that microorganisms might play an important role in regulating soil element cycles in constructed wetlands by affecting the metabolism of activated carbon and reactive nitrogen. This study has implications for increasing the carbon sink of constructed wetlands to mitigate the effects of global warming.

Salinity and temperature influence removal levels of heavy metals and chloride from water by wetland plants.

Stormwater with low temperatures and elevated salinity, common in areas where deicing salt is used, might affect the removal of heavy metals by plants in stormwater treatment systems such as floating treatment wetlands. This short-term study evaluated the effects of combinations of temperature (5, 15, and 25 °C) and salinity (0, 100, and 1000 mg NaCl L-1) on the removal of Cd, Cu, Pb, and Zn (1.2, 68.5, 78.4, and 559 µg L-1) and Cl- (0, 60, and 600 mg Cl- L-1) by Carex pseudocyperus, C. riparia, and Phalaris arundinacea. These species had previously been identified as suitable candidates for floating treatment wetland applications. The study found high removal capacity in all treatment combinations, especially for Pb and Cu. However, low temperatures decreased the removal of all heavy metals, and increased salinity decreased the removal of Cd and Pb but had no effect on the removal of Zn or Cu. No interactions were found between the effects of salinity and of temperature. Carex pseudocyperus best removed Cu and Pb, whereas P. arundinacea best removed Cd, Zu, and Cl-. The removal efficacy for metals was generally high, with elevated salinity and low temperatures having small impacts. The findings indicate that efficient heavy metal removal can also be expected in cold saline waters if the right plant species are used.

Advances in studies on the plant rhizosphere microorganisms in wetlands: A visualization analysis based on CiteSpace.

Rhizosphere microorganisms and their interactions with plants in wetlands have recently attracted much attention due to their importance in enhancing plant environmental adaptation, removing wetland pollutants, and alleviating climate change. However, the fluctuating hydrological environment of wetlands leads to more complex dynamics in the rhizosphere environment. Research progress and hotspots concerning plant-rhizosphere microorganisms under special wetland environments are still kept unclear. To better understand the current research status, hotspots and trends of rhizosphere microorganisms in wetlands, we used CiteSpace bibliometric software to visualize and analyze 231 English-language publications from the Web of Science core collection database. Here, we reviewed the role played by various countries, institutions, and scholars in the studies of plant rhizosphere microorganisms in wetlands based on cooperation network analysis. We discussed the shift from bioremediation and nutrient removal to rhizosphere microbial community composition as a research hotspot for plant rhizosphere microorganisms in wetlands according to keyword co-occurrence and clustering analysis. Finally, we highlighted that more attention should be paid to the ecological functions of rhizosphere microorganisms in different wetland ecosystems, and the plant‒microbe microinterface processes and interaction patterns should be explored in depth to provide new indicators for the evaluation of wetland ecosystem functions.

Characterization of copper binding to biochar-derived dissolved organic matter: Effects of pyrolysis temperature and natural wetland plants.

Characterization of the biochar-derived dissolved organic matter (BDOM) is essential to understanding the environmental efficacy of biochar and the behavior of heavy metals. In this study, the binding properties of BDOM derived from different pyrolysis temperatures, wetland plants, and plant organs with Cu was investigated based on a multi-analytical approach. In general, the pyrolysis temperature exhibited a more significant impact on both the spectral characteristics of BDOM and Cu binding behavior than those of the feedstocks. With the pyrolysis temperature increased, the dissolved organic carbon, aromaticity, and fluorescence substance of BDOM decreased and the structure became more condensed. Humic-and tryptophan-like substance was more susceptible to the addition of Cu for BDOM pyrolyzed at 300 â„ƒ and 500 â„ƒ, respectively. In addition, the more tyrosine-like substance is involved in Cu binding at higher pyrolysis temperature (500 â„ƒ). However, the fluvic-like substance occurred preferentially with Cu than the other fluorophores. Moreover, the higher binding capacity for Cu was exhibited by the humic-like substance and by BDOM derived from the higher pyrolysis temperature and the lower elevation plants with the corresponding average stability constants (log KM) of 5.58, 5.36, and 5.16.

Copper, zinc, and chromium accumulation in aquatic macrophytes from a highly polluted river of Argentina.

The aims of this study were to assess Cu, Zn, and Cr pollution in a highly polluted river in Argentina (Matanza-Riachuelo) and to evaluate tolerance strategies and toxic effects in aquatic macrophytes. Chemical techniques were used to assess the bioavailability of these metals and to evaluate their uptake and translocation by plants. The ultrastructure of the roots of a free-floating plant (Eichhornia crassipes) and the leaves of an emergent macrophyte (Sagittaria montevidensis) was examined using transmission electron microscopy. In the lower basin of the river, the highest concentrations of total heavy metals were detected in water (179 µgZn/g; 54 µgCu/g; 240 µgCr/g) and sediments (1499 µgZn/g; 393 µgCu/g; 4886 µgCr/g). In the upper basin of the river, low percentages of Zn and Cu (8 to 25%) were extracted with DTPA and EDTA, probably due to the lithogenic origin of these metals. Higher extraction percentages (24 to 66%) were obtained in the lower basin, in accordance with anthropogenic pollution. For Cr, extraction percentages were low in the upper basin of the river (< 4.5%) and extremely low in the lower basin (< 0.03%). In S. montevidensis, the BCF (bioconcentration factor) and TF (translocation factor) indexes were compatible with heavy metal exclusion mechanisms in sediments, whereas in the E. crassipes, root compartmentalization could be the main tolerance strategy. The leaves of S. montevidensis showed no evidence of damage, whereas ultrastructural alterations (plasmolyzed cells, disorganized membranes) were observed in E. crassipes.