Fate and removal of fluoroquinolone antibiotics in mesocosmic wetlands: Impact on wetland performance, resistance genes and microbial communities.

The fate of fluoroquinolone antibiotics norfloxacin and ofloxacin were investigated in mesocosmic wetlands, along with their effects on nutrients removal, antibiotic resistance genes (ARGs) and epiphytic microbial communities on Hydrilla verticillate using bionic plants as control groups. Approximately 99% of norfloxacin and ofloxacin were removed from overlaying water, and H. verticillate inhibited fluoroquinolones accumulation in surface sediments compared to bionic plants. Partial least squares path modeling showed that antibiotics significantly inhibited the nutrient removal capacity (0.55) but had no direct effect on plant physiology. Ofloxacin impaired wetland performance more strongly than norfloxacin and more impacted the primary microbial phyla, whereas substrates played the most decisive role on microbial diversities. High antibiotics concentration shifted the most dominant phyla from Proteobacteria to Bacteroidetes and inhibited the Xenobiotics biodegradation function, contributing to the aggravation in wetland performance. Dechloromonas and Pseudomonas were regarded as the key microorganisms for antibiotics degradation. Co-occurrence network analysis excavated that microorganisms degrade antibiotics mainly through co-metabolism, and more complexity and facilitation/reciprocity between microbes attached to submerged plants compared to bionic plants. Furthermore, environmental factors influenced ARGs mainly by altering the community dynamics of differential bacteria. This study offers new insights into antibiotic removal and regulation of ARGs accumulation in wetlands with submerged macrophyte.

Meta-analysis review for pilot and large-scale constructed wetlands: Design parameters, treatment performance, and influencing factors.

Despite their longstanding use in environmental remediation, constructed wetlands (CWs) are still topical due to their sustainable and nature-based approach. While research and review publications have grown annually by 7.5 % and 37.6 %, respectively, from 2018 to 2022, a quantitative meta-analysis employing advanced statistics and machine learning to assess CWs has not yet been conducted. Further, traditional statistics of mean ± standard deviation could not convey the extent of confidence or uncertainty in results from CW studies. This study employed a 95 % bootstrap-based confidence interval and out-of-bag Random Forest-based driver analysis on data from 55 studies, totaling 163 cases of pilot and full-scale CWs. The study recommends, with 95 % confidence, median surface hydraulic loading rates (HLR) of 0.14 [0.11, 0.17] m/d for vertical flow-CWs (VF) and 0.13 [0.07, 0.22] m/d for horizontal flow-CWs (HF), and hydraulic retention time (HRT) of 125.14 [48.0, 189.6] h for VF, 72.00 [42.00, 86.28] h for HF, as practical for new CW design. Permutation importance results indicate influent COD impacted primarily on COD removal rate at 21.58 %, followed by HLR (16.03 %), HRT (12.12 %), and substrate height (H) (10.90 %). For TN treatment, influent TN and COD were the most significant contributors at 12.89 % and 10.01 %, respectively, while H (9.76 %), HRT (9.72 %), and HLR (5.87 %) had lower impacts. Surprisingly, while HRT and H had a limited effect on COD removal, they substantially influenced TN. This study sheds light on CWs' performance, design, and control factors, guiding their operation and optimization.

Seasonal dynamics and typology of microplastic pollution in Huixian karst wetland groundwater: Implications for ecosystem health.

This study offers an insightful and detailed examination of microplastic pollution in the Huixian karst wetland's groundwater, providing novel insights into the complex interplay of microplastic characteristics and their seasonal dynamics. We meticulously quantified microplastic concentrations, observing significant seasonal variation with values ranging from 4.9 to 13.4 n·L-1 in the wet season and 0.53-49.4 n·L-1 in the dry season. Our analysis pinpoints human activities and atmospheric deposition as key contributors to this contamination. A critical finding of our research is the pronounced disparity in microplastic levels between open wells and covered artesian wells, highlighting the vulnerability of open wells to higher pollution levels. Through correlation analysis, we unearthed the crucial influence of the karst region's unique hydrogeological characteristics on microplastic migration, distinctively different from non-karst areas. The karst terrain, characterized by its caves and subterranean rivers, facilitates the downward movement of microplastics from surface to groundwater, exacerbating pollution levels. Our investigation identifies agricultural runoff and domestic wastewater as primary pollution sources. These findings not only underscore the urgent need for environmental stewardship in karst regions but also provide a crucial foundation for formulating effective strategies to mitigate microplastic pollution in karst groundwater. The implications of this study extend beyond the Huixian karst wetland, offering a template for addressing microplastic pollution in similar ecosystems globally.

Spatial and temporal changes in shorebird habitats under different land use scenarios along the Yellow and Bohai Sea coasts in China.

The effect of coastal wetland loss on shorebird habitat in recent years has been widely reported in previous studies. Various coastal wetland conservation and restoration measures have been implemented or will soon be implemented in China. The extent to which these measures will affect the area and structure of coastal wetland habitat in the future remains unclear. Here, we predicted changes in habitat area and structure for 39 common shorebird species along the coasts of the Yellow and Bohai Seas using a cellular automata-Markov (CA-Markov) land use scenario model and a maximum entropy species distribution model, along with terrain factors (slope, aspect, and digital evaluation model) and climate factors (temperature and precipitation) from the Data Centre for Resources and Environmental Sciences at the Chinese Academy of Sciences, land cover maps interpreted using the human-computer interactive method, and citizen science data of shorebird occurrences derived from eBird, Global Biodiversity Information Facility, and Bird Report. We found that shorebird habitat was most abundant along the coasts of Bohai Bay, Laizhou Bay, and Yancheng. The area of habitat decreased and became increasingly fragmented between 2000 and 2020 for more than half of the 39 species. Under the future business-as-usual scenario, the area of shorebird habitat decreased from 2020 to 2050, and the remaining habitat became increasingly fragmented. Under the ecological protection (EP) scenario, habitat loss was mitigated, and habitat connectivity was improved. The area of habitat was lower in 2050 under the EP scenario than in 2000 for most species, especially threatened species, suggesting that the area of habitat will not return to year-2000 levels under the EP scenario. These results emphasize the need to protect remaining shorebird habitats and implement ecological conservation measures to ensure the long-term preservation of coastal wetlands.

Waterbird Species Are Highly Sensitive to Wetland Traits: Simulation-Based Conservation Strategies for the Birds of the Sicilian Wetlands (Italy).

In this study, we (a) formulated a general hypothesis about how wetland (functional and structural) traits influence avian diversity, (b) turned this hypothesis into a non-parametric Bayesian network, (c) disentangled the direct and indirect effects of the variables influencing waterbird species, and (d) simulated the changes expected to the levels of avian diversity as a result of numerous counterfactual and management scenarios. We applied our framework to the Sicilian wetlands as a whole; then, we downscaled simulations locally to a wetland of particular interest (Pantano Bruno). We found that (1) waterbird species are highly sensitive to wetland traits; (2) wetland traits have both direct and indirect effects upon alpha avian diversity; (3) the direct and indirect effects of wetland traits can be contrasting; (4) water level fluctuations (benefit), diversions (cost), and salinity (cost) are key factors for waterbird conservation; (5) these wetlands have the potential for hosting a level of alpha avian diversity that is double the baseline (from 19 to 38 species); (6) these wetlands are prone to ecological collapse if all traits deteriorate (from 19 to 6 species per wetland); and (7) the ecological information gained at the regional scale can be properly downscaled to the local scale to make inferences on single wetlands.

Impacts of Invasive Plants on Native Vegetation Communities in Wetland and Stream Mitigation.

We sampled vegetation communities across plant invasion gradients at multiple wetland and stream mitigation sites in the Coastal Plain and Piedmont physiographic provinces of Virginia, USA. Impacts of invasion were evaluated by tracking changes in species composition and native vegetation community properties along the abundance gradients of multiple plant invaders. We found that native species richness, diversity, and floristic quality were consistently highest at moderate levels of invasion (ca. 5-10% relative abundance of invader), regardless of the identity of the invasive species or the type of mitigation (wetland or stream). Likewise, native species composition was similar between uninvaded and moderately invaded areas, and only diminished when invaders were present at higher abundance values. Currently, low thresholds for invasive species performance standards (e.g., below 5% relative abundance of invader) compel mitigation managers to use non-selective control methods such as herbicides to reduce invasive plant cover. Our results suggest that this could cause indiscriminate mortality of desirable native species at much higher levels of richness, diversity, and floristic quality than previously thought. From our data, we recommend an invasive species performance standard of 10% relative invader(s) abundance on wetland and stream mitigation sites, in combination with vigilant invasive plant mapping strategies. Based on our results, this slightly higher standard would strike a balance between proactive management and unnecessary loss of plant community functions at the hands of compulsory invasive species management.

Identification of ecological security patterns of alpine wetland grasslands based on landscape ecological risks: A study in Zoigê County.

Climate change and human activities have increased ecological risks and degraded ecosystem functions in alpine wetland grassland regions, where ecological security remains largely unexplored. The construction of ecological security patterns (ESP) can help to synchronize regional ecological security and sustainable development and provide ideas to address these challenges. This article determines the current ESP of Zoigê County, China, by analyzing the spatial and temporal characteristics of landscape ecological risk (LER) and generating an ecological network by combining the InVEST model, the landscape connectivity index, and the circuit theory model. Management zoning and targeted conservation recommendations are proposed. The results indicate that the region has significant spatial heterogeneity in IER. Ecological risk exposure is increasing, with high values mainly concentrated in the central part of the region. Meanwhile, ecological protection areas were identified, which included 2578.44 km2 of ecological sources, 71 key ecological corridors, 25 potential ecological corridors, 4 river ecological corridors, 66 pinch points, and 58 barriers. This study provides a valuable reference for the ecological development of Zoigê County, as well as insights into the formation of ESP in other alpine wetland grassland regions.

Nitrogen dynamics of alpine swamp meadows are less responsive to climate warming than that of alpine meadows.

The freeze-thaw cycle mediates permafrost soil hydrothermal status, nitrogen (N) mineralization, and loss. Furthermore, it affects root development and competition among nitrophilic and other species, shaping the pattern of N distribution in alpine ecosystems. However, the specific N dynamics during the growing season and N loss during the non-growing season in response to climate warming under low- and high-moisture conditions are not well documented. Therefore, we added 15N tracers to trace the fate of N in warmed and ambient alpine meadows and alpine swamp meadows in the permafrost region of the Qinghai-Tibet Plateau. During the growing season, warming increased 15N recovery (15Nrec) in shoots of K. humilis, litters, 0-5 and 5-20 cm roots in the alpine meadow by 149.94 % ± 52.87 %, 114.58 % ± 24.43 %, 61.11 % ± 32.27 %, and 97.12 % ± 42.92 %, respectively, while increased 15Nrec of litters by 151.55 % ± 27.06 % in the alpine swamp meadow. During the non-growing season, warming reduced 15N stored in roots by 486.77 % ± 57.90 %, though increased the 15N recovery in 5-20 cm soil depth by 76.68 % ± 39.42 % in the alpine meadow, whereas it did not affect N loss during the non-growing season in the alpine swamp meadow. Overall, warming promoted N utilization by increasing the plant N pool during the growing season, and enhanced root N loss and downward migration during the non-growing season due to the freeze-thaw process, which may result in fine root turnover and cell destruction releasing N in the alpine meadow. Conversely, the N dynamics of alpine swamp meadows were less responsive to climate warming.

New insights into substrates shaped nutrients removal, species interactions and community assembly mechanisms in tidal flow constructed wetlands treating low carbon-to-nitrogen rural wastewater.

A limited understanding of microbial interactions and community assembly mechanisms in constructed wetlands (CWs), particularly with different substrates, has hampered the establishment of ecological connections between micro-level interactions and macro-level wetland performance. In this study, CWs with distinct substrates (zeolite, CW_A; manganese ore, CW_B) were constructed to investigate the nutrient removal efficiency, microbial interactions, metabolic mechanisms, and ecological assembly for treating rural sewage with a low carbon-to-nitrogen ratio. CW_B showed higher removal of ammonia nitrogen and total nitrogen by about 1.75-6.75 % and 3.42-5.18 %, respectively, compared to CW_A. Candidatus_Competibacter (denitrifying glycogen-accumulating bacteria) was the dominant microbial genus in CW_A, whereas unclassified_f_Blastocatellaceae (involved in carbon and nitrogen transformation) dominated in CW_B. The null model revealed that stochastic processes (drift) dominated community assembly in both CWs; however, deterministic selection accounted for a higher proportion in CW_B. Compared to those in CW_A, the interactions between microbes in CW_B were more complex, with more key microbes involved in carbon, nitrogen, and phosphorus conversion; the synergistic cooperation of functional bacteria facilitated simultaneous nitrification-denitrification. Manganese ores favour biofilm formation, increase the activity of the electron transport system, and enhance ammonia oxidation and nitrate reduction. These results elucidated the ecological patterns exhibited by microbes under different substrate conditions thereby contributing to our understanding of how substrates shape distinct microcosms in CW systems. This study provides valuable insights for guiding the future construction and management of CWs.

Evaluating drained water quality in a pilot worm-sludge treatment reed bed planted with Arundo donnas in the Mediterranean climate.

This study evaluated the impact of incorporating earthworms (Eisenia fetida) on the drained water quality from a sludge treatment reed bed. The experiment encompassed four setups of treatment beds in two replicates: planted with Arundo donax and addition of earthworms, planted without earthworms, unplanted with earthworms, and treatment bed without plants nor earthworms as control. The units were fed every two weeks with mixed sewage sludge, a blend of primary and secondary sludge over 24 cycles. The mixed sewage sludge had mean dry and volatile solid contents of 24.71 g.DS.L-1 (± 13.67) and 19.14 g.VS.L-1 (± 10.29) resulting a sludge loading rate of 43.59 kg.DS.m-2.year-1 (± 14.49). The inclusion of earthworms in the planted unit reduced release masses of total suspended solids, chemical oxygen demand, nitrate and phosphorous by 43, 45, 75 and 45 % compared to the planted unit. Plant biomass production increased by 43 % with the earthworm presence. The removal efficiency of the units improved after a ramp-up phase (after six months feeding) of which the concentration of TSS, COD and Escherichia coli met limits for water reuse while nitrogen components and phosphorous surpassed the limits. The planted unit with earthworms removed 99 and 99 % of TSS and COD, respectively. Overall, water loss namely through evapotranspiration and earthworm hydration need, positively correlated with pollutant concentration, and earthworm-planted unit had 46 % higher water loss compared to control unit.

Assessing the Combined Effects of Host and Parasite Exposure to Forever Chemicals in an Amphibian-Echinostome System.

Per- and polyfluoroalkyl substances (PFAS) are environmental contaminants of growing concern due to their potential negative effects on wildlife and human health. Per- and polyfluoroalkyl substances have been shown to alter immune function in various taxa, which could influence the outcomes of host-parasite interactions. To date, studies have focused on the effects of PFAS on host susceptibility to parasites, but no studies have addressed the effects of PFAS on parasites. To address this knowledge gap, we independently manipulated exposure of larval northern leopard frogs (Rana pipiens) and parasites (flatworms) via their snail intermediate host to environmentally relevant PFAS concentrations and then conducted trials to assess host susceptibility to infection, parasite infectivity, and parasite longevity after emergence from the host. We found that PFAS exposure to only the host led to no significant change in parasite load, whereas exposure of parasites to a 10-µg/L mixture of PFAS led to a significant reduction in parasite load in hosts that were not exposed to PFAS. We found that when both host and parasite were exposed to PFAS there was no difference in parasite load. In addition, we found significant differences in parasite longevity post emergence following exposure to PFAS. Although some PFAS-exposed parasites had greater longevity, this did not necessarily translate into increased infection success, possibly because of impaired movement of the parasite. Our results indicate that exposure to PFAS can potentially impact host-parasite interactions. Environ Toxicol Chem 2024;00:1-10. © 2024 SETAC.

Quantifying the bioaccumulation and trophic transfer processes of heavy metals based on the food web: A case study from freshwater wetland in northeast China.

The contamination of wetlands by heavy metals, exacerbated by agricultural activities, presents a threat to both organisms and humans. Heavy metals may undergo trophic transfer through the food web. However, the methods for quantifying the bioaccumulation and trophic transfer processes of heavy metals based on the food web remains unclear. In this study, we employed stable isotope technology to construct a quantitative oriental white stork's typical food web model under a more accurate scaled Δ15N framework. On this basis, the concentrations for heavy metal (Cu, Zn, Hg, Pb) were analyzed, we innovatively visualized the trophic transfer process of heavy metals across 13 nodes and 45 links and quantified the transfer flux based on the diet proportions and heavy metal concentrations of species, taking into account biomagnification effects and potential risks. Our findings revealed that as for Cu and Pb, the transfer flux level was consistent with diet proportion across most links. While Hg and Zn transfer flux level exceeded the corresponding diet proportion in the majority of links. In summary, Hg exhibited a significant biomagnification, whereas Cu, Zn, Pb experienced biodilution. The fish dietary health risk assessment for fish consumers showed that Hg, Pb posed certain risks. This research marks a significant step forward in the quantitative assessment of multi-link networks involving heavy metals within the food web.

Microbial community diversity of an integrated constructed wetland used for treatment of sewage.

The microbial community diversity in Constructed Wetland System (CWS) plays a key role in the removal of pollutants from waste water. An integrated functional CWS developed at Neela Hauz Biodiversity Park, Delhi was selected to assess the diversity in composition and structure of microbial community diversity of sludge and sediment of CWS, based on metagenomic approach using 16S rRNA genes. The sediment showed higher diversity than sludge and both formed distinct clusters. The taxonomic structure of the microbial community of CWS is represented by 6,731 OTUs distributed among 2 kingdoms, 103 phyla, 227 classes, 337 orders, 320 families, 295 identified genera, and 84 identified species. The relative abundance of top 5 dominant phyla of sludge and sediment varied from 3.77% (Acidobacteria) to 35.33% (Proteobacteria) and 4.07% (Firmicutes) to 28.20% (Proteobacteria), respectively. The range of variation in relative abundance of top 5 dominant genera of sludge and sediment was 2.58% (Hyphomicrobium) to 6.61% (Planctomyces) and 2.47% (Clostridium) to 4.22% (Syntrophobacter), respectively. The rich microbial diversity of CWS makes it perform better in pollutants removal (59.91-95.76%) than other CWs. Based on the abundance values of taxa, the taxa are grouped under four frequency distribution classes-abundant (>20), common (10-19), rare (5-9), and very rare (1-4). The unique structure of microbial communities of integrated CWS is that the number of abundant taxa decreases in descending order of taxonomic hierarchy, while the number of rare and very rare taxa increases. For example, the number of abundant phyla was 14 and 21 in sludge and sediment, respectively and both communities have only 3 abundant genera each. This is in contrast to 4 and 17 very rare phyla in sludge and sediment, respectively and both the communities have 114 and 91 very rare genera, respectively. The outcomes of the study is that the integrated CWS has much higher microbial community diversity than the diversity reported for other CWs, and the rich diversity can be used for optimizing the performance efficiency of CWS in the removal of pollutants from waste water. Such structural diversity might be an adaptation to heterogeneous environment of CWS.

Comparative analysis of the gut bacteria and fungi in migratory demoiselle cranes (Grus virgo) and common cranes (Grus grus) in the Yellow River Wetland, China.

Introduction: Gut microbiota are closely related to the nutrition, immunity, and metabolism of the host and play important roles in maintaining the normal physiological activities of animals. Cranes are important protected avian species in China, and they are sensitive to changes in the ecological environment and are thus good environmental indicators. There have been no reports examining gut fungi or the correlation between bacteria and fungi in wild Demoiselle cranes (Grus virgo) and Common cranes (Grus grus). Related research can provide a foundation for the protection of rare wild animals. Methods: 16S rRNA and ITS high-throughput sequencing techniques were used to analyze the gut bacterial and fungal diversity of Common and Demoiselle cranes migrating to the Yellow River wetland in Inner Mongolia. Results: The results revealed that for gut bacteria α diversity, Chao1 index in Demoiselle cranes was remarkably higher than that in Common cranes (411.07 ± 79.54 vs. 294.92 ± 22.38), while other index had no remarkably differences. There was no remarkable difference in fungal diversity. There were marked differences in the gut microbial composition between the two crane species. At the phylum level, the highest abundance of bacteria in the Common crane and Demoiselle crane samples was Firmicutes, accounting for 87.84% and 74.29%, respectively. The highest abundance of fungi in the guts of the Common and Demoiselle cranes was Ascomycota, accounting for 69.42% and 57.63%, respectively. At the genus level, the most abundant bacterial genus in the Common crane sample was Turicibacter (38.60%), and the most abundant bacterial genus in the Demoiselle crane sample was Catelicoccus (39.18%). The most abundant fungi in the Common crane sample was Penicillium (6.97%), and the most abundant fungi in the Demoiselle crane sample was Saccharomyces (8.59%). Correlation analysis indicated that there was a significant correlation between gut bacteria and fungi. Discussion: This study provided a research basis for the protection of cranes. Indeed, a better understanding of the gut microbiota is very important for the conservation and management of wild birds, as it not only helps us to understand their life history and related mechanisms, but also can hinder the spread of pathogenic microorganisms.

Effects of returning paddy field to wetland on composition and stability of soil aggregates in the Yellow River Delta.

The composition and stability of soil aggregates are important indicators for measuring soil quality, which would be affected by land use changes. Taking wetlands with different returning years (2 and 15 years) in the Yellow River Delta as the research object, paddy fields and natural wetlands as control, we analyzed the changes in soil physicochemical properties and soil aggregate composition. The results showed that soil water content, total organic carbon, dissolved organic carbon and total phosphorus of the returning soil (0-40 cm) showed an overall increasing trend with returning period, while soil pH and bulk density was in adverse. There was no significant change in clay content, electrical conductivity, and total nitrogen content. The contents of macro-aggregates and micro-aggregates showed overall increasing and decreasing trend with returning period, respectively. The stability of aggregates in the topsoil (0-10 cm) increased with returning years. Geometric mean diameter and mean weight diameter increased by 8.9% and 40.4% in the 15th year of returning, respectively, while the mass proportion of >2.5 mm fraction decreased by 10.5%. There was no effect of returning on aggregates in subsoil (10-40 cm). Our results indicated that returning paddy field to wetland in the Yellow River Delta would play a positive role in improving soil structure and aggregate stability.

Wetland technology for the treatment of HCH-contaminated water - Case study at Hajek site.

Hexachlorocyclohexanes (HCH) isomers and their transformation products, such as chlorobenzenes (ClB), generate severe and persistent environmental problems at many sites worldwide. The Wetland technology employing oxidation-reduction, biosorption, biodegradation and phytoremediation methods can sufficiently treat HCH-contaminated water. The treatment process is inherently natural and requires no supplementary chemicals or energy. The prototype with a capacity of 3 L/s was installed at Hajek quarry spoil heap (CZ), to optimize the technology on a full scale. The system is fed by drainage water with an average concentration of HCH 129 µg/L, ClB 640 µg/L and chlorophenols (ClPh) of 16 µg/L. The system was tested in two years of operation, regularly monitored for HCH, ClB and ClPh, and maintained to improve its efficiency. The assessment was not only for environmental effects but also for socio and economic indicators. During the operation, the removal efficiency of HCH ranged from 53.5 % to 96.9 % (83.9 % on average) depending on the flow rate. Removal efficiency was not uniform for individual HCH isomers but exhibited the trend: α = γ = δ > ß = ε. The improved water quality was reflected in a biodiversity increase expressed by a number of phytobenthos (diatoms) species, a common biomarker of aquatic environment quality. The Wetland outranked the conventional WWTP in 10 out of the 15 general categories, and it is the most relevant scenario from the socio, environmental, and economic aspects.

Removal and reduction mechanism of Cr (VI) in Leersia hexandra Swartz constructed wetland-microbial fuel cell coupling system.

Cr (VI) is extremely harmful to both the environment and human health, and it can linger in the environment for a very long period. In this research, the Leersia hexandra Swartz constructed wetland-microbial fuel cell (CW-MFC) system was constructed to purify Cr (VI) wastewater. By comparing with the constructed wetland (CW) system, the system electricity generation, pollutants removal, Cr enrichment, and morphological transformation of the system were discussed. The results demonstrated that the L. hexandra CW-MFC system promoted removal of pollutants and production of electricity of the system. The maximum voltage of the system was 499 mV, the COD and Cr (VI) removal efficiency was 93.73% and 97.00%. At the same time, it enhanced the substrate and L. hexandra ability to absorb Cr and change it morphologically transformation. Additionally, the results of XPS and XANES showed that the majority of the Cr in the L. hexandra and substrate was present as Cr (III). In the L. hexandra CW-MFC system, Geobacter also functioned as the primary metal catabolic reducing and electrogenic bacteria. As a result, L. hexandra CW-MFC system possesses the added benefit of removing Cr (VI) while producing energy compared to the traditional CW system.

Centennial loss of lake wetlands in the Yangtze Plain, China: Impacts of land use changes accompanied by hydrological connectivity loss.

Humans have played a fundamental role in altering lake wetland ecosystems, necessitating the use of diverse data types to accurately quantify long-term changes, identify potential drivers, and establish a baseline status. We complied high-resolution historical topographic maps and Landsat imagery to assess the dynamics of the lake wetlands in the Yangtze Plain over the past century, with special attention to land use and hydrological connectivity changes. Results showed an overall loss of 45.6 % (∼11,859.5 km2) of the lake wetlands over the past century. The number of lakes larger than 10 km2 decreased from 149 to 100 due to lake dispersion, vanishing, and shrinkage. The extent of lake wetland loss was 3.8 times larger during the 1930s-1970s than that in the 1970s-1990s. Thereafter, the lake wetland area remained relatively stable, and a net increase was observed during the 2010s-2020s in the Yangtze Plain. The significant loss of lake wetland was predominately driven by agricultural activities and urban land expansion, accounting for 81.1 % and 4.9 % of the total losses, respectively. In addition, the changes in longitudinal and lateral hydrological connectivity further exacerbated the lake wetland changes across the Yangtze Plain through isolation between lakes and the Yangtze River and within the lakes. A total of 130 lakes have been isolated from the Yangtze River due to the construction of sluices and dykes throughout the Yangtze Plain, resulting in the decrease in the proportion of floodplain marsh from 28.3 % in the 1930s to 8.0 % in the 2020s. Furthermore, over 260 sub-lakes larger than 1 km2 (with a total area of 1276.4 km2) are experiencing a loss of connectivity with their parent lakes currently. This study could provide an improved historical baseline of lake wetland changes to guide the conservation planning to wetland protection and prioritization area in the Yangtze Plain.

Identification and scoring of conservation gaps in wetlands of China's coastal provinces: Implications for extending protected areas.

Wetlands in China's coastal provinces are strategically positioned along migratory flyways for waterbirds, serving as essential habitats and stopover sites due to the expansive land area and abundant wetland resources they offer. This study aimed to introduce a simplified index system to enable rapid assessment and prioritization of unprotected areas for wetlands in China's coastal provinces. A spatial analysis was conducted, combining wetland distribution and existing protected areas data and spatial extent of wetlands extracted by remote sensing data. Results indicate substantial gaps in coverage, covering an area of 108.33 × 104 ha, with 76% being natural wetlands. Over half of these gaps are identified as high-value wetlands with significant ecological functions. The uneven distribution of unprotected wetlands reflects a tension between economic development and wetland conservation. Our findings support the expansion of the existing coastal wetland protected areas' coverage, as well as protecting critical habitats in conservation gaps, and establishing of a network-based waterbird protection system. This research contributes to informed decision-making and policy in wetlands' conservation planning.

Molecular transformation of dissolved organic matter in manganese ore-mediated constructed wetlands for fresh leachate treatment.

The organic matter (OM) and nitrogen in Fresh leachate (FL) from waste compression sites pose environmental and health risks. Even though the constructed wetland (CW) can efficiently remove these pollutants, the molecular-level transformations of dissolved OM (DOM) in FL remain uncertain. This study reports the molecular dynamics of DOM and nitrogen removal during FL treatment in CWs. Two lab-scale vertical-flow CW systems were employed: one using only sand as substrates (act as a control, CW-C) and the other employing an equal mixture of manganese ore powder and sand (experimental, CW-M). Over 488 days of operation, CW-M exhibited significantly higher removal rates for chemical oxygen demand (COD), ammonia nitrogen (NH4+-N), and dissolved organic matter (represented by dissolved organic carbon, DOC) at 98.2 ± 2.5%, 99.2 ± 1.4%, and 97.9 ± 1.9%, respectively, in contrast to CW-C (92.8 ± 6.8%, 77.1 ± 28.1%, and 74.7 ± 9.5%). The three-dimensional fluorescence excitation-emission matrix (3D-EEM) and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) analyses unveiled that the influent DOM was predominantly composed of readily biodegradable protein-like substances with high carbon content and low unsaturation. Throughout treatment, it led to the degradation of low O/C and high H/C compounds, resulting in the formation of DOM with higher unsaturation and aromaticity, resembling humic-like substances. CW-M showcased a distinct DOM composition, characterized by lower carbon content yet higher unsaturation and aromaticity than CW-C. The study also identified the presence of Gammaproteobacteria, reported as Mn-oxidizing bacteria with significantly higher abundance in the upper and middle layers of CW-M, facilitating manganese cycling and improving DOM removal. Key pathways contributing to DOM removal encompassed adsorption, catalytic oxidation by manganese oxides, and microbial degradation. This study offers novel insights into DOM transformation and removal from FL during CW treatment, which will facilitate better design and enhanced performance.