Water Purification Function Research Articles

Ecological threshold effect mediates the long-term synergistic management of mega-city runoff nutrients in large-scale hybrid constructed wetlands

Constructed wetlands (CWs), as nature-based solutions for pollutant control, have been widely applied globally. The functionality of CW ecosystems begins to degrade when certain ecological thresholds are exceeded, where the ecosystem’s response and functions stay within a 'safe ecological limit'. However, the sustainability of these functions and their ecological thresholds have not yet been quantitatively assessed. This gap limits our understanding of the sustainability of CWs and the “safe operating space” for environmental management. Here, we evaluate whether and how the nitrogen and phosphorus removal functions in large-scale hybrid CWs (HCWs) of a mega-city change over time, as well as how they respond to changes in pollutant loads, stoichiometric characteristics, hydrology, and environmental conditions. Though it has been running stably for 6 years, the large HCWs achieved average total nitrogen (TN) and phosphorus (TP) removal efficiencies of 81.0 % and 55.8 % from 2017 to 2020, respectively, with widespread synergistic relationships. This indicates that CWs have a long-term effect of removing nitrogen and phosphorus pollutants for over 10 years. A decrease in the stoichiometric characteristic TN:TP from inflow to outflow was a signal for preferential nitrogen removal (35 vs. 6.8, mass based). Importantly, the TN and TP removal efficiencies and their synergistic relationship change over operation time, with threshold points occurring at 378 days, 259 days, 1040 days, and 647 days, respectively. TN and TP removal efficiencies and their synergistic relationship were controlled by the thresholds of nitrogen (9.6–12.1 mg/L) and phosphorus (0.6–0.8 mg/L) loads, TN:TP (7.59), water levels (25.5–25.6 m), water replenishment (0.14 m), dissolved oxygen (5.8–9.0 mg/L), temperature (9.3–13.9 °C), and pH (8.8–10.1) levels. The thresholds of cross-attribute driving factors significantly affect the sustainability of nutrient removal functions. Our findings provide new insights into the threshold effects of pollutant loads and their stoichiometric characteristics, hydrology, and environmental conditions on the water purification functions of CWs. This offers critical support for defining the safe operating space in the sustainable management of CWs in mega-cities.

Change and Prediction of Water Purification Function in the South Bank of Hangzhou Bay in the Past 20 Years

The investigation of regional water purification functionality and its influencing factors holds significant pragmatic implications in understanding the potential of regional water purification, guiding context-specific regional comprehensive planning schemes, and environmental conservation measures. The study site, situated along the southern coast of Hangzhou Bay, represents a prototypical region characterized by intricate land-sea interactions that bear substantial economic and ecological functions. By assimilating a meticulously collected topographical and land-use dataset, in conjunction with site-specific meteorological records, the water purification model embedded within the integrated valuation of ecosystem services and trade-offs (InVEST) framework was employed to scrutinize the spatiotemporal dynamics of nitrogen (N) and phosphorus (P) loads, discharges, and removals within the southern coast of Hangzhou Bay. The prime objective of this study was to unravel the differentials in water purification functionality under diverse developmental scenarios. The investigation unearthed distinct temporal discrepancies in N and P discharges and removals over two temporal dimensions. Relative to the benchmark year 2000, the total N load experienced a reduction of 276.72 t, whereas the N discharge and removals decreased by 140.86 and 137.86 t, respectively, in the year 2020. In contrast, the total P load observed an increase of 93.65 t, accompanied by a surge in P discharge and removals by 28.91 and 64.74 t, respectively. Spatially, the distribution pattern of N and P discharges exhibited a general inclination of elevated values in the northern region and subdued values in the southern region, with certain pockets in the southern region exhibiting pronounced peaks, intimately associated with land-use typologies. Simulation analyses conducted under distinct scenarios unveiled that under the natural development priority scenario, the N and P discharges within the study area amounted to 1 682.36 and 115.50 t, respectively. Conversely, under the scenario emphasizing economic development, the regional N and P discharges showed an approximate escalation of 83.02% and 79.93%, correspondingly. In contrast, under the scenario emphasizing environmental conservation, the regional N and P discharges exhibited a notable decline of approximately 79.96% and 56.44%, respectively. Hence, the scenario prioritizing the amalgamation of environmental conservation and development effectively reduced the N and P discharges within the region, bolstering the water purification functionality. The results derived from this study furnish a solid theoretical foundation for effectuating region-specific planning schemes fostering coordinated economic and ecological advancement within the study area.

The Impact of Plant Spatial Patterns on Nitrogen Removal in the Naolihe Wetlands of Northeast China

The impact of the spatial pattern of wetland plants on nitrogen removal is a hot research topic. Ten water samples were collected from separate sampling points in mid-August and at the end of October 2021, and the concentrations of TN, NH4-N, and NO3-N in the water were measured to calculate the removal rates for the three forms of nitrogen in Naolihe wetlands. The spatial indices were interpreted for various plants based on images from samples taken in August. Step-by-step eliminations and function fitting methods were performed to determine the relationships between the spatial index and the removal rates for three forms of nitrogen. The results show that both Deyeuxia angustifolia (DA) and Phragmites australis (PA) ranked first for the functions between the order of sampling points of spatial indices (areas and shapes) and the removal rates for the three forms of nitrogen during the elimination process, indicating that DA and PA were the main forces determining nitrogen removal, which was dependent on plants covering the largest areas (DA: 31.2% and PA: 24.3%), with some large patches (largest plants index: DA (0.26) and PA (0.21)) and strong connectivity (patch edge density: DA (16.79) and PA (15.70)). These results have value for studying the relationship between spatial patterns and water purification functions.

Characteristics and environmental significance of organic carbon deposition in Baiyangdian Lake, China, 1969–2020

Lake sediments provide a basis for ecological information that can reconstruct the history of a lake ecosystem and clarify the carbon sink process. We combined chronological information relating to sediment cores in Baiyangdian Lake with the history of human activities, to examine the influence of the natural environment and human activities on the humification of organic carbon. This analysis revealed the evolution of the ecological environment in the lake over the past 50 years. The results showed the average deposition rate of sediments to be 0.957 cm/a; with the total organic carbon and total nitrogen contents of sediments ranging from 14.32 to 333.19 g/kg and from 0.95 to 26.90 g/kg, respectively. The δ13C values ranged from −13.04 ‰ to −29.07 ‰, while the δ15N values ranged from −1.43 ‰ to 8.37 ‰. The fulvic acid carbon (FAC) content ranged from 0.52 g/kg to 14.21 g/kg, and the humic acid carbon (HAC) content ranged from 1.67 g/kg to 23.82 g/kg. The HAC/FAC value gradually increased as the sediment deepend. The results of each index in the sedimentary column, combined with the dating information, allowed us to conclude that, from 1969 to 1985, human activities had little effect on the lake, and the source of organic carbon and the humification process remained stable. During this period, the water purification function of the lake continued to improve. From 1985 to 2014, the surrounding economy developed rapidly, resulting in significant changes in the lake's ecological structure and the distribution of lake plants. Serious eutrophication occurred, leading to increased pollution Between 2014 and 2020, the lake protection measures implemented achieved initial positive results. During the period, the source of organic carbon and the humification process stabilized, eutrophication was alleviated, and the burial and fixation of organic carbon gradually reached a healthier state.

Multifunctional Solar Evaporator with Adjustable Island Structure Improves Performance and Salt Discharge Capacity of Desalination.

Interfacial solar steam generation (ISSG) is the main method to get fresh water from seawater or wastewater. The balance between evaporation rate and salt resistance is still a major challenge for ISSG. Herein, a wood aerogel island solar evaporator (WAISE) with tunable surface structure and wettability by synthesizing poly(n-isopropylacrylamide)-modified multi-walled carbon nanotube photothermal layers. Compared to dense surface structure evaporators, interfacial moisture transport, thermal localization, and surface water vapor diffusion of WAISE are greatly promoted, and the evaporation rate of WAISE increased by 87.64%. WAISE allows for record performance of 200h continuous operation in 20% NaCl solution without salt accumulation. In addition, the photo-thermal-electric device is developed based on WAISE with continuous water purification, power generation, and irrigation functions. This work provides a new direction for the development of multifunctional water purification systems.

Exploring an Integrated System for Urban Stormwater Management: A Systematic Literature Review of Solutions at Building and District Scales

Climate change has aggravated the frequency and severity of extreme weather events, particularly in flood-related hazards. Cities nowadays face significant challenges in stormwater management from frequent heavy rainfalls. Traditional urban drainage systems can no longer cope with large amounts of surface runoff; cities are searching for new ways to deal with urban stormwater. Green roofs and other nature-based solutions have been widely used for stormwater management by combining water purification and retention functions but have not yet fully solved the flood problems. This article aims to (1) explore the different aspects of urban water management, particularly the urban stormwater topic, and (2) identify the existing solutions and discuss the potential and barriers to integrated solutions implementation. By introducing the concept of four domains and finding the overlapping area to investigate, we analyzed different solutions to reduce rainwater runoff from the roof and ground level, aiming at building and district scales. This paper proves that further research direction could constitute an integrated system to work together for urban stormwater management.

CoS2를 이용한 6가 크롬 폐수 처리에서 pH 및 온도의 영향

The effective treatment of wastewater containing toxic substances produced by human activity continues to be a pressing issue, particularly given the increasingly serious water shortages that occur globally due to development pressure and climate change. In particular, Cr(VI) has been identified by many governments worldwide as a priority pollutant for treatment due to its wide distribution and toxic effects. Thus, there is a need to develop efficient removal methods for this pollutant, including the design of materials with water purification functions. In this study, cobalt sulfide (CoS₂) was used to remove Cr(VI) from water. After 120 min at room temperature (25℃), 30 mg of CoS₂ removed 4.24, 2.68, 2.44, 1.28, and 1.80 mg/L Cr(VI) at a pH of 2, 4, 6.5, 9, and 11, respectively. At pH 2, the Cr(VI) removal efficiency of CoS₂ increased with a higher reaction temperature (19.91 mg/L after 90 min at 55℃), while an increase in the initial concentration of Cr(VI) facilitated the greater removal of Cr(VI) by CoS₂ at pH 11. The results of total chromium testing indicated that there were two mechanisms for the removal of Cr(VI) by CoS₂ at pH 2 and pH 11. At pH 2-9, HCrO₄ ^- ions attract electrons on the surface of CoS₂ and react with hydrogen ions to form water-soluble Cr(III) cations and water. At pH 11, Co³⁺ on the CoS₂ surface reacts with hydroxide ions to generate Co(OH)₃ flocs that adsorb Cr(VI) ions from the solution. The results of this study collectively demonstrate that CoS₂ is effective in the treatment of Cr(VI) at pH 2 and pH 11 and has broad potential for use in a range of applications.

Coupled impacts of climate and land use changes on regional ecosystem services

Ecosystem services (ES) are key to maintaining sustainable regional development. Climate change and land cover and land use change (LULC) are one of the main factors leading to changes in regional ecosystem services. Existing studies have simulated regional ES changes under different future scenarios, providing valuable guidance for regional sustainable management. However, most studies focus on the effects of individual factors (LULC or climate change) on ES, paying insufficient attention to the coupled effects of the two elements. Yunnan Province is a biodiversity hotspot facing challenges in ES in the context of future climate change and rapid socio-economic development. In order to achieve sustainable management, policies must be developed in advance to address possible future ecological risks. In this study, we simulated the coupled effects of climate change and LULC on six types of ES using the SD, FLUS, and InVEST models. The scenario framework of shared socioeconomic pathways SSP245 and SSP585 was combined with LULC scenario dynamics to assess the changes of ES in 2030 and 2050, identifying sensitive areas and providing a scientific basis for local ecosystem management. In 2020, the eastern part of Yunnan Province was the coldspot area for all ES. Under the future scenarios, Yunnan Province's ES show different loss rates and distinct spatial heterogeneity. Future climate change and LULC changes have a more significant negative impact on water conservation and water quality purification. About 66% of its counties will become sensitive areas for water production services, and 37% of counties will endure reduced water purification functions by more than 50%. According to the analytical results, we then proposed several suggestions to improve regional ES management.

Transformation Path of Ecological Product Value and Efficiency Evaluation: The Case of the Qilihai Wetland in Tianjin.

In order to protect wetland resources, China has developed wetland conservation policies and has made significant conservation investments, but there is still a lack of pathways for the conversion to economic value, making it difficult to meet the demand for continuous investment. We have explored a sustainable ecological conservation mechanism using the Seven Mile Sea as a case study, so that ecological conservation costs can be transformed into economic development behaviors and ecological benefits and socio-economic development can be integrated. This paper assesses the ecological product value of the Qilihai Wetland based on the ecosystem service function value assessment method, which designs the realization path of ecological product value and predicts the value transformation efficiency. The results show the following: (1) The total value of ecological products in the study area is CNY 569.06 million (USD 78.36 million), and the main sources of value are plant products in the supply service and water purification functions in the regulation service, accounting for 54.05% and 26.10% of the total, respectively. (2) The predicted value realization of ecological products, ideally, is CNY 689.65 million (USD 94.96 million), with a value realization rate of 111.60%. Considering the management policy restrictions in different areas of the Qilihai Wetland, the actual value realization volume is CNY 391.94 million (USD 53.97 million), with a value realization rate of 63.42%. (3) Owing to the restriction of the development policy of supply services and cultural services, the value realization path mainly contains two types: one is to drive the development of supply services and cultural services in the surrounding areas, along with product premiums, to realize value transformation. This path is mainly aimed at the supply of local characteristic products and the development of tourism. The second is to realize the value of regulating services through ecological compensation and ecological equity trading. This path is mainly for the adjustment and support services in the core area and buffer area. According to the pre-accounting results, the contribution rates of the two paths are 62.25% and 37.75%, respectively. The second path should be further effectively developed to improve the contribution rate. This study helps assess the ecological value and important ecological elements of the Qilihai Wetland to ensure effective protection and development of important ecological resources and to achieve the sustainable development of wetland resources. It provides a reference for exploring feasible paths to realize the value of ecological goods.

Substance accumulation of a wetland plant, Leersia japonica, during senescence in the Yihe and Shuhe River Basin, North China.

Leersia japonica is a perennial Gramineae grass that is dominant in shallow wetlands of the Yihe and Shuhe River Basin, North China. Previous studies have shown that L. japonica recovers early (March), tillers strongly, and has an excellent ability to purify sewage in spring. This early revival might play a vital role in water purification function; however, whether the plant benefits from the physiological activities during senescence remains unclear. Therefore, in this study, an experiment was conducted during the winter of 2016 and in the following spring. Morphology (height, biomass, root morphology), physiology (root vitality, malondialdehyde [MDA], superoxide dismutase [SOD]), substance contents (soluble sugar, soluble protein) and substance transportation (activity of enzymes for transportation and energy supply) were determined during weeks 0, 2, 4, 6, and 8 of the senescence stage (October 11, 2016); as well as substance contents and bud increments during days 0,7, 14, 21, 31 and 41 of the revival period (February 22, 2017). The results revealed that (1) the root biomass of L. japonica increased significantly during senescence, even after the leaves withered. (2) The root diameter of L. japonica decreased significantly, while root weight per volume and root superficial area per volume increased significantly during senescence. The root vitality was relatively stable in winter, especially for root absorption area per volume. (3) No significant difference was observed in membrane stability of stems, rhizomes and roots of L. japonica in winter, with the MDA content remaining stable and SOD activity increasing significantly during senescence. (4) The soluble sugar content of all tissues of L. japonica increased sharply during senescence; while it decreased significantly in spring, especially for buds. (5) The enzymes for substance metabolism responded differently, with activities of H+-ATPase and pyruvate decarboxylase (PDC) decreasing, and alcohol dehydrogenase (ADH) increasing. Therefore, L. japonica has active morphological adaptation of roots, physiological regulation, and massive substance accumulation during senescence stage. The special life-history trait ensures L. japonica survival in winter and revival in early spring, which makes it being an excellent plant for purifying sewage in spring.

Influence of DOM and microbes on Fe biogeochemistry at a riverbank filtration site

Riverbank filtration (RBF) constitutes an important part of the water cycle, which involves active natural filtration leading to pollution of river water being intercepted and retained. The RBF has the function of water purification, but retention of exogenous pollutants in the RBF system complicates biogeochemical processes due to the presence of primary active components. In this study, we verified the essential role of microbial mediation during the interactions between primary Fe minerals in the RBF system and dissolved organic matter (DOM) in river water based on lab-scale experiments. The results demonstrated that DOM from infiltration of river water increased the amount of iron (Fe) released from the sediment in RBF, leading to an increase in Fe concentration in groundwater by higher than one order of magnitude. In particular, the existence of Fe bacteria even made this effect more thorough and more complex. Abiotic reduction was shown to play a more significant role in increasing Fe release than microbe-mediated reduction. Increasing the amount of Fe released could change the distribution of Fe minerals at the sediment surface, thereby affecting the structure of the microbial community in the RBF system and decreasing the DOM concentration in the groundwater. Moreover, As and Mn were found to behave in a similar manner as Fe due to their close biochemical properties when interacting with primary minerals in sediment. This study not only provides mechanistic insight into the higher Fe concentrations encountered in the groundwater of nearby rivers but also has important practical implications for developing nature-based technologies for water pollution control and environmental remediation.

Peculiarities of formation of the forest litter of the water protection pine plantations in the Ukrainian interflue of the Dnipro and Desna rivers

The effective performance of ameliorative functions by water protection plantations is largely determined by the development of the forest litter, its structure, capacity, quality composition, and degree of mineralization. Therefore, the aim of the study was to identify the features of the formation of the forest litter of pine plantations of the Ukrainian interfluves of the Dnipro and Desna. The study of forest litter was carried out on the accounting sites in all age groups of plantations, in which 22 test plots were laid. Litter samples were taken in between rows and directly in rows of forest plantations. During the analysis of the qualitative composition of the forest litter of young plantations, the dominance of the upper horizon of the inactive fraction, which consisted mainly of needles and branches, was revealed. Here, the share of inactive litter in the conditions of moist poor pine site and moist relatively poor pine site was 8.13 t/ha or 85.1% and 12.54 t/ha or 92.1%, respectively. A large amount of dust, which forms the active fraction, was recorded in the lower horizon. Its stocks were 5.3-5.6 times higher than the reserves of inactive litter. In general, in young pine forests in the conditions of moist poor pine site, the stock of inactive litter is 15.10 t/ha (28.1%), while its presence in of moist poor pine site is 17.91 t/ha, 36.5%. In middle-aged pine forests, the share of the active litter fraction increases, which is a consequence of the active action of its decomposition processes. The share of active litter is 79.3% or 155.29 t/ha in mature stands of the conditions of moist poor pine site. This is evidence of the intensification of the processes of mineralization and activation of the circulation of substances. Three horizons are clearly distinguished in the litter of plantations of older age groups, with a strong connection between them. The lower layer of the forest litter of water conservation plantations is permeated with physiologically active roots, which forms its dense type of structure. Under such conditions, during the separation of the lower layer of litter from the upper one, it does not fall apart and its structure remains dense. The presence of strongly intertwined physiologically active roots in the third horizon of the litter is evidence of the activation of microbiological processes, which are also accelerated by the interception of moisture and the accumulation of humus particles of the soil by the lower layers of the forest litter. To prevent the development of flood processes, the effective performance of water regulation and water purification functions, it is recommended to create water conservation plantations with the formation of the identified type of forest litter

Valuing water purification services of forests: a production function approach using panel data from China's Sichuan province

AbstractThe water purification functions of forests represent one of the most frequently invoked examples of nonmarket ecosystem services that are economically valuable. This study quantifies the monetary value of forests' water purification services in the form of the ensuing cost savings of municipal drinking water treatment, using a rich panel dataset from China's Sichuan province. Moreover, this study has undertaken a novel spatial piecewise approach to investigate the spatial patterns of such cost savings delivered by forests at different distances from the water intake point. The estimation results find that forests within a 2 km radius upstream from the water intake point have the most sizeable and statistically significant cost saving effect. For forests within a 3 km radius, this effect becomes somewhat smaller but remains statistically significant. Beyond a 4 km radius, this effect becomes notably smaller and statistically equal to zero. Our analysis facilitates the optimal spatial targeting of forest conservation.

Storage tank as a pretreatment unit for rainwater cleaner production: Role of biofilm bacterial communities and functional genera in water quality improvement

This study investigated the water purification function and mechanism of biofilm in storage tank, with a view to using it as a pretreatment unit for rainwater cleaner production. Shortening the hydraulic retention time (HRT) of storage tank from 12 to 4 h improved the pollutants removal performance and reduced the suspended bacteria counts. The accumulation of abundant taxa and succession of rare taxa were observed with biofilm development. Positive correlations within and across different bacterial taxa were dominant in the network, and some rare genera (Ralstonia and Micropruina) were identified as hub bacteria. Candidatus Nitrospira nitrosa and Nitrospira sp. ENR4 were two identified complete ammonia oxidizers. Denitrifying bacteria tended to enrich and formed more complex interactions over time. The main nitrogen metabolism pathways may be ammonia assimilatory, complete denitrification and dissimilatory/assimilatory nitrate reduction. HRT was negatively correlated with most dominant genera, and contributed 20.35% to the variation of functional taxa. This study highlights the self-purification function and micro-ecology of storage tank, and provides a new insight for its role in rainwater cleaner production process.

Effect of the Influent Substrate Concentration on Nitrogen Removal from Summer to Winter in Field Pilot-Scale Multistage Constructed Wetland–Pond Systems for Treating Low-C/N River Water

The quality of micropolluted water is unstable and its substrate concentration fluctuates greatly. The goal is to predict the concentration effect on the treatment of nitrogen in a river with an actual low C/N ratio for the proposed full-scale Xiaoyi River estuary wetland, so that the wetland project can operate stably and perform the water purification function effectively in the long term. Two pilot-scale multistage constructed wetland–pond (MCWP) systems (S1 and S2, respectively) based on actual engineering with the same “front ecological oxidation ponds, two-stage horizontal subsurface flow constructed wetlands and surface flow constructed wetlands (SFCWs) as the core and postsubmerged plant ponds” as the planned process were constructed to investigate the effect of different influent permanganate indexes (CODMn) and total nitrogen (TN) contents on nitrogen removal from micropolluted river water with a fixed C/N ratio from summer to winter in the field. The results indicate that the TN removal rate in the S1 and S2 systems was significant (19.56% and 34.84%, respectively). During the process of treating this micropolluted water with a fixed C/N ratio, the influent of S2 with a higher CODMn concentration was conducive to the removal of TN. The TN removal rate in S2 was significantly affected by the daily highest temperature. There was significant nitrogen removal efficiency in the SFCWs. The C/N ratio was a major determinant influencing the nitrogen removal rate in the SFCWs. The organic matter release phenomenon in SFCWs with high-density planting played an essential role in alleviating the lack of carbon sources in the influent. This research strongly supports the rule that there is seasonal nitrogen removal in the MCWPs under different influent substrate concentrations, which is of guiding significance for practical engineering.

Spatial Pattern of Dissolved Nitrogen in the Water on Receiving Agricultural Drainage in the Sanhuanpao Wetland in China

The total nitrogen (TN) increases and the water quality deteriorates when a large amount of nitrogen-containing water is discharged from farmlands into wetlands. This research on the relationship between the TN, ammonia nitrogen (NH4-N), and nitrate nitrogen (NO3-N) concentrations in water has a certain reference significance for understanding the spatial pattern of nitrogen removal in wetlands. Taking the Sanhuanpao wetland in northeast China as the research object, 24 sampling plots in the study area were sampled in the spring and summer of 2017 to test the concentrations of TN, NH4-N, and NO3-N. Based on the calculations of the change rates of the TN, NH4-N, and NO3-N in spring and summer, a step-by-step elimination analysis was carried out and the spatial pattern of the TN, NH4-N, and NO3-N removals were revealed by gradual buffer extrapolations, combined with stepwise fitting functions. The results show that the removal capacity of NH4-N is strong within the range of 14.55 km–20 km and 26.93 km–35.96 km from the wetland inlet, and the removal capacity of NO3-N is relatively strong within the range of 26.93 km–35.96 km. The strong NH4-N and NO3-N removal areas in the wetland are not in the geometric center of the wetland, but in separate narrow areas around the center. The TN removal along water channel direction is only 0.25 times higher than that direction perpendicular to the channel, indicating that regardless of whether wetlands are expanded along the water channel or perpendicular to the water channel, the difference to the TN removal is small. Effectively monitoring and managing the reception of agricultural drainage is extremely important for maintaining the water-purification function of wetlands. The aim of the research is to reveal a spatial law of nitrogen removal in wetland water, and provide a framework for studying the mechanism of spatial difference of nitrogen.

Constructed Wetlands in South Korea: Current Status and Performance Assessment

The efficiency of nature-based facilities is mostly evaluated in terms of their pollutant removal capabilities; however, apart from water purification functions, constructed wetlands also perform ecological, cultural, and environmental education functions. A multi-criteria performance index was developed in this study to evaluate the overall efficiency of constructed wetlands. A total of 54 constructed wetlands installed across South Korea were monitored to evaluate the pollutant removal performance of the facilities. A comparison between the conventional pollutant removal-based evaluation and the developed multi-criteria index was also performed to determine the key changes in the results of evaluation when different methods are employed. Among the different types of wetlands studied, hybrid systems were found to be the most effective in terms of pollutant removal due to their complex configurations and functions. Newly constructed treatment wetlands have unstable performance and thus, a stabilization period ranging from two to five years is required to assess the facility’s pollutant removal capabilities. As compared to the conventional pollutant removal-based efficiency evaluation, the comprehensive evaluation method provided a more strategic tool for identifying the facilities’ strengths and weaknesses. Generally, the multi-criteria performance index developed in this inquiry can be utilized as a general tool for evaluating the sustainability of similar nature-based facilities.

The role of soils in regulation of freshwater and coastal water quality.

Water quality regulation is an important ecosystem service function of soil. In this study, the mechanism by which soil regulates water quality was reviewed, and the effects of soil management on water quality were explored. A scientometrics analysis was also conducted to explore the research fields and hotspots of water quality regulation of soil in the past 5 years. This review found that the pollutants entering the soil can be mitigated by precipitation, adsorption and desorption, ion exchange, redox and metabolic decomposition. As an optimal substrate, soil in constructed wetlands has perfect performance in the adsorption and passivation of pollutants such as nitrogen, phosphorus and heavy metals in water, and degradation of pesticides and emerging contaminants. Mangrove wetlands play an important role in coastal zone protection and coastal water quality restoration. However, the excessive application of agricultural chemicals causes soil overload, which leads to the occurrence of agricultural non-point source pollution. Under the dual pressures of climate change and food insecurity in the future, developing environmentally friendly and economically feasible sustainable soil management measures is crucial for maintaining the water purification function of soil by relying on the accurate quantification of soil function based on big data and modelling. This article is part of the theme issue 'The role of soils in delivering Nature's Contributions to People'.

System of financial sustainability management of forestry enterprises of southern Ukraine

The article considers the possibility of more efficient use of forest resources of the steppe zone of Ukraine, including by improving the level of financial stability of forestry enterprises in the South of Ukraine. For this purpose, on the basis of well-known principles of process algorithmization, a conceptual model of formation of the financial stability management system of forestry enterprises of the South of Ukraine is proposed. The presented model is based on the economic, social and environmental components (subsystems) of forestry enterprises and in each of them the necessary directions (possible effects) for improving the financial condition of economic entities are identified. The main reasons of normative and organizational nature, which make it impossible to increase the economic potential of forestry enterprises in the South of Ukraine, are highlighted. The directions of cooperation of forestry enterprises with local self-government bodies are offered, in particular: conclusion of commercial agreements on reconstruction of existing and creation of new parks and squares, construction of sanatoriums, cultural and entertaining, development of water purification and water-preserving functions of forest plantations. The mechanism of realization of the system of management of financial stability of the forestry enterprises which is based on realization by the forestry enterprises of a complex of the corresponding organizational and technical and administrative actions is presented. which consists in the implementation of the relevant stages of the enterprise, in particular: capitalization of own assets, identification of sources of funding and diversification of activities. It is substantiated as one of the directions of diversification of forestry enterprises, creation of energy crops on forest lands that cannot be used for other needs, and production of pellets from them for further sale. In particular, based on the calculations, it is proved that the proposed direction of diversification of forest enterprises in the South of Ukraine will not only improve their financial condition, but also attract low-value lands that are unsuitable for growing forests and crops, eventually improving their structure and content.

Impact of future climate scenarios on peatland and constructed wetland water quality: A mesocosm experiment within climate chambers

Water purification is one of the most essential services provided by wetlands. A lot of concerns regarding wetlands subjected to climate change relate to their susceptibility to hydrological change and the increase in temperature as a result of global warming. A warmer condition may accelerate the rate of decomposition and release of nutrients, which can be exported downstream and cause serious ecological challenges; e.g., eutrophication and acidification. The aim of this study is to investigate the effect of climate change on water quality in peatland and constructed wetland ecosystems subject to water level management. For this purpose, the authors simulated the current climate scenario base on the database from Malmö station (Scania, Sweden) for 2016 and 2017 as well as the future climate scenarios for the last 30 years of the century based on the Representative Concentration Pathway (RCP) and different regional climate models (RCM) for a region wider than Scania County. For future climate change, the authors simulated low (RCP 2.6), moderate (RCP 4.5) and extreme (RCP 8.5) climate scenarios. All simulations were conducted within climate chambers for experimental peatland and constructed wetland mesocosms. Our results demonstrate that the effect of climate scenario is significantly different for peatlands and constructed wetlands (interactive effect) for the combined chemical variables. The warmest climate scenario RCP 8.5 is linked to a higher water purification function for constructed wetlands, but to a lower water purification function and a subsequent deterioration of peatland water qualities, even if subjected to water level management. The explanation for the different response of constructed wetlands and peatlands to climate change could be due to the fact that the substrate in the constructed wetland mesocosms and peatlands was different in terms of the organic matter quality and quantity. The utilization of nutrients by the plants and microbial community readily exceed the mineralization under a limited nutrient content (as we had in constructed wetland) when the temperature rises. However, concerning the extreme scenario RCP 8.5, the peatlands have shown a tendency to have reverse processes.