Phosphorus Concentrations In Water Research Articles

Effect of Myriophyllum verticillatum on controlling phosphorus release from sediment for water environment purification

Eutrophication is one of the most common water pollution problems in the world. In this paper, the effects of Myriophyllum verticillatum on phosphorus content in water and sediment were studied. The results showed that Myriophyllum verticillatum had the strongest purification effect on water sample. Under the condition of sufficient light, suitable temperature and environmental factors not affected by the external environment, the phosphorus content in the overlying water increased first and then decreased. In addition to the external factors, the phosphorus content in the water decreased. The results show that the growth of Myriophyllum verticillatum depends on the change of phosphorus concentration in water. The increase of phosphorus concentration in water will increase the phosphorus concentration in plants and accelerate the growth of Myriophyllum verticillatum. However, the growth of Myriophyllum verticillatum will consume more phosphorus. Myriophyllum verticillatum in sufficient light, suitable temperature, environmental factors are not affected by the outside world. The contents of phosphorus in the sediments showed a downward trend. In addition to the external factors, the phosphorus content in the sediment was reduced by Myriophyllum verticillatum. The relationship between the growth of Myriophyllum verticillatum and the total phosphorus concentration in sediments is interdependent. The release of phosphorus in sediment will increase the phosphorus content in water, which will lead to the enrichment of phosphorus in plants and accelerate the growth of Myriophyllum verticillatum. The growth of Myriophyllum verticillatum will make Myriophyllum verticillatum need more phosphorus, which will accelerate the absorption of phosphorus in water and release more phosphorus from sediment. This is the reaction mechanism of phosphorus removal by Myriophyllum verticillatum; Under the conditions of sufficient light, warm climate and environmental factors not affected by the external environment, the total phosphorus content of Myriophyllum verticillatum was on the rise.

Data-driven interval credibility constrained quadratic programming model for water quality management under uncertainty

Although integrated simulation-optimization modeling can provide a comprehensive and reliable analysis for water quality management (WQM), it is usually not easy to implement in practice. This study proposed a new efficient simulation-optimization modeling approach by leveraging the power of data-driven modeling, to support WQM under various uncertainties. A water quality simulation model is integrated with the optimization model, and then substituted by a series of numerical surrogate models based on inexact linear regression. The transformation can significantly reduce the computational burden and make it possible to implement uncertainty quantification through hybrid inexact programming. The proposed model incorporates interval quadratic programming and credibility constrained programming to deal with nonlinearity and various uncertainties associated with the management system. The proposed approach is applied to a real case study of the Grand River watershed in Canada for controlling phosphorus concentration in river water. The Grand River Simulation Model (GRSM) is employed as the physical simulation model to estimate the total phosphorus concentration in the river. Interval solutions under different confidence levels of violating the effluent standards were obtained, which can be used to generate optimal phosphorus control strategies. The results indicate the proposed data-driven interval credibility constrained quadratic programming (DICCQP) model is able to provide reliable and robust solutions for WQM by considering nonlinearity and various uncertainties while maintaining a high computational efficiency. The proposed new framework can be extended and applied to the other watersheds. The high efficiency of the proposed model makes it possible to solve large-scale complex water quality management and planning problems.

High‐frequency monitoring of hydrological and biogeochemical fluxes in forested catchments of southern Chile

AbstractThe variability of rainfall‐dependent streamflow at catchment scale modulates many ecosystem processes in wet temperate forests. Runoff in small mountain catchments is characterized by a quick response to rainfall pulses which affects biogeochemical fluxes to all downstream systems. In wet‐temperate climates, water erosion is the most important natural factor driving downstream soil and nutrient losses from upland ecosystems. Most hydrochemical studies have focused on water flux measurements at hourly scales, along with weekly or monthly samples for water chemistry. Here, we assessed how water and element flows from broad‐leaved, evergreen forested catchments in southwestern South America, are influenced by different successional stages, quantifying runoff, sediment transport and nutrient fluxes during hourly rainfall events of different intensities. Hydrograph comparisons among different successional stages indicated that forested catchments differed in their responses to high intensity rainfall, with greater runoff in areas covered by secondary forests (SF), compared to old‐growth forest cover (OG) and dense scrub vegetation (CH). Further, throughfall water was greatly nutrient enriched for all forest types. Suspended sediment loads varied between successional stages. SF catchments exported 455 kg of sediments per ha, followed by OG with 91 kg/ha and CH with 14 kg/ha, corresponding to 11 rainfall events measured from December 2013 to April 2014. Total nitrogen (TN) and phosphorus (TP) concentrations in stream water also varied with rainfall intensity. In seven rainfall events sampled during the study period, CH catchments exported less nutrients (46 kg/ha TN and 7 kg/ha TP) than SF catchments (718 kg/ha TN and 107 kg/ha TP), while OG catchments exported intermediate sediment loads (201 kg/ha TN and 23 kg/ha TP). Further, we found significant effects of successional stage attributes (vegetation structure and soil physical properties) and catchment morphometry on runoff and sediment concentrations, and greater nutrients retention in OG and CH catchments. We conclude that in these southern hemisphere, broad‐leaved evergreen temperate forests, hydrological processes are driven by multiple interacting phenomena, including climate, vegetation, soils, topography, and disturbance history.

Influence of surface geology on phosphorus export in coastal forested headwater catchments in Akita, Japan

ABSTRACT Surface geology is a key factor regulating the geographical patterns of P export; however, geographically extensive data on P export mechanisms from natural coastal mountain regions are lacking. We compared stream-water characteristics in forested headwater catchments with different types of surface geology (marine sedimentary rocks [MSRs] and igneous rocks [IRs]) and evaluated the factors regulating soluble reactive phosphorus (SRP) concentrations in stream water. Geographically extensive stratified sampling was conducted: stream-water and sediment samples were obtained from 66 MSR catchments and 55 adjacent IR catchments along the coastal forested mountain regions in Akita, Japan. SRP and major cations and anions in stream waters were analyzed. To evaluate the effect of ionic composition on SRP, sediments were extracted with NaCl and CaCl2 solutions and the SRP concentrations in the extracts were measured. Stream SRP was significantly higher in MSR catchments (median 23 µg L−1) than in IR catchments (median 8 µg L−1) (P < 0.001), and tended to be higher in MSR catchments with younger rocks. Dissolved inorganic nitrogen (DIN) did not differ between catchments with different geologies; therefore, DIN/SRP was significantly lower in MSR catchments (median 18), close to the Redfield ratio. On a Piper diagram, high-SRP stream waters were of the NaCl water type, and stream SRP was significantly correlated with Na+ (r = 0.642, P < 0.0001). In IR catchments, stream waters had relatively higher Ca2+ and Mg2+ concentrations. SRP in the sediment extracts was significantly higher in MSR catchments and samples obtained by NaCl extraction than in IR catchments and CaCl2-extracted samples. Exchangeable Na+ in sediments was significantly higher in MSR catchments, decreasing Ca2+ in the liquid phase by an ion-exchange reaction, which is likely also key in maintaining high SRP levels. We conclude that MSR catchments in coastal Akita are a significant P source for streams even in headwater forests, and that site-specific NaCl water types and higher exchangeable Na+ concentrations in sediments result in higher SRP concentrations in stream waters. These results have critical implications for P cycles in freshwater ecosystems influenced by Na+.

Suppression of phosphorus release from eutrophic lake sediments by sediment microbial fuel cells

ABSTRACT Sediment microbial fuel cells (SMFCs) have served as an alternative technique to suppress phosphorus release from lake sediments to water bodies and thus mitigate eutrophication. However, the phosphorus regulation mechanism remains unclear. The purpose of this research was to understand the electrochemical influence of an SMFC on the phosphorus concentration in interstitial water. In this study, a lab-scale SMFC was applied to acetate-spiked sediments (ace+) and unspiked sediments (sed) with closed-circuit (CC)/open-circuit (OC) columns, and the circuitry was switched to investigate the relationship between electron transfer and phosphorus concentration. The dissolved total phosphorus (DTP) concentration in the sediment interstitial water in CC columns significantly decreased to below 0.1 mg/L, whereas the DTP in OC columns remained high for nine weeks. After switching the circuit, the DTP in OC→CC columns dropped but that in CC→OC columns increased within one week. At the end of the experimental period, the DTP concentrations in CC/sed, CC/ace+, OC/sed, and OC/ace+ columns were 0.10 ± 0.02, 0.03 ± 0.00, 0.82 ± 0.01, and 1.66 ± 0.12 mg/L, respectively. The respective estimated anode capacitances of those columns were 2.05 ± 0.49, 5.15 ± 0.14, 0.72 ± 0.19, and 0.71 ± 0.12 nF. We concluded that the phosphorus may have been electrochemically attracted and retained on the anode in the sediment because the adsorbed DTP contents and the increased anode capacitances were strongly correlated. Thus, SMFCs can be used for suppressing phosphorus release from eutrophic lake sediments.

A method for reconstructing past lake water phosphorus concentrations using\xa0sediment geochemical records

An existing steady state model of lake phosphorus (P) budgets has been adapted to allow reconstruction of long-term average historic lake water total phosphorus (TP) concentrations using lake sediment records of P burial. This model can be applied without site-specific parameterisation, thus potentially having universal application. In principle, it is applicable at any site where there is both a sediment P burial record and knowledge of the current water budget, although we advise caution applying it to problematic sediment records. Tested at six published case study sites, modelled lake water TP concentrations agree well with water-quality monitoring data, and limited testing finds good agreement with wholly independent diatom inferred lake water TP. Our findings, together with a review of the literature, suggest that well preserved lake sediments can usefully record a long-term average P burial rate from which the long-term mean lake water TP can be reliably estimated. These lake water TP reconstructions can provide meaningful site-specific reference values to support decision making in lake eutrophication management, including establishing targets for lake restoration.

Effects of zebra mussels (Dreissena polymorpha) on phytoplankton under eutrophic conditions

We conducted two mesocosm experiments (2014 and 2017) to determine how invasive zebra mussels affected abundance and structure of phytoplankton community. Algae reaction was different for the introduction of D. polymorpha in 2014 and 2017. There was no influence of zebra mussels on the phytoplankton total abundance; however, it changed the biomass of individual taxa. Cyanoprokaryota reaction as a result the zebra mussels introduction was influenced by the initial phytoplankton structure and initial nitrogen and phosphorus concentrations in water. The biomass of Сyanoprokaryotа decreased at low N:P ratios and increased at high N:P ratios. Dreissena increased the biomass of large green filamentous algae, which is a poor food resource for zooplankton.

Fluctuation of phosphorus concentration in Lake Taihu in the past 70 years and future control strategy

分析湖泊中磷浓度的变化特征，揭示其变化的驱动机制，是有效实施湖泊水体磷浓度控制的前提.本文整理分析了太湖70年来（1949—2020年）水体磷浓度监测历史资料，对比了太湖不同湖区、不同时间尺度水体磷浓度的差异性及波动性，发现影响太湖磷浓度变化的原因既有人为的因素，也有自然的因素.无论是污染较轻的1950年，还是污染负荷相对较重的近30年，太湖水体磷浓度一直存在较大时空差异性.暴雨引发入湖河流携带磷污染的扩散、风浪扰动引起的内源释放及蓝藻水华期间藻类生物量的大幅时空变化，都加剧了太湖水体磷浓度的不稳定性.近20年的太湖水污染治理对磷浓度的时空分布影响明显，1998年的太湖水污染治理“零点行动”，2007年以来的水利调度等系列水污染治理工程，以及2017年以来的藻情变化等，都对太湖水体磷浓度的时空格局产生了影响.然而，高强度治理投入下太湖水体磷浓度依然偏高，其原因与流域建设用地比例增加、人口增加、耕地种植结构变化等外源负荷因素发生变化有关，也与湖体沉水植被退化、出入流结构发生变化、气候变化引发的蓝藻水华扩张等内源强度及水体表观磷浓度决定因素的生态环境变化有关.近70年来太湖水体磷浓度的变化过程对类似大型浅水湖泊的磷控制策略具有启示意义：大型浅水湖泊存在磷浓度较大波动的自然属性，在水环境保护目标考核中应充分考虑其不确定性，制定切实可行的控制目标；在控制策略上应将外源负荷控制放在首位，在流域污水处理厂深度除磷及流域土地利用调整等方面采取措施，实现入湖磷负荷的大幅削减，同时实施湖体生态修复与食物链调控措施，才能逐步实现湖泊水体磷浓度的控制目标.;Understanding the changing mechanism of phosphorus concentration in lakes is the precondition of strategic decision for lake restoration. Based on the 70 years (1949-2020) phosphorus concentration monitoring data at Lake Taihu, a large shallow lake, it is found that the phosphorus concentration was highly fluctuated temporally and spatially, owing to both human pollution and natural limnological changes. Phosphorus concentrations was largely different both in the relatively clean 1950 and in the relatively polluted recent 30 years. Heavy rain storm discharge plenty of external phosphorus into the lake, causing large spatial difference of water phosphorus concentration. Strong wind causing lots of phosphorus released from lake sediment, causing large temporal fluctuation of phosphorus concentration. And algal bloom materials re- distribution by wind driving also bring about large uncertainty of phosphorus concentrations. In the recent 20 years, pollution abatement projects have significantly changed the spatial-temporal change of phosphorus concentration in Lake Taihu. Zero Action of water pollution control in Taihu catchment since 1998, water resource diversion engineering since 2007, and the bloom situation aggravate since 2017 have significantly influenced the fluctuation intensity, spatial distribution and mean value of phosphorus in Lake Taihu. However, phosphorus concentrations in the whole Lake Taihu still keep high level even plenty of pollution treatment investigation. Its reasons are owing to both external loading factors, such as largely increase of construction land use ratios, population increases, and crop planting structure change in farmlands, and internal loading factors, such as submerged vegetation degradations, hydrological structure changes, and algal bloom aggravates under climatic change. The seventy years variation characteristic of phosphorus concentration in Lake Taihu should provide lessons for large shallow lakes management. Relatively large fluctuation of phosphorus concentration in lake water is the nature of large shallow lakes. Decision-maker should consider the natural characteristic when they formulate the protection target of large shallow lakes. External loading abatement should give priority, such as land use adjustment in Lake Taihu basin and deeply phosphorus removal in tail-water of urban sewage treatment plants. At the same time, internal loading control measures, such as submerged vegetation restoration and top-down food-web control of algal biomass by bio-manipulation of fishery should be undertaken to make sure the highly fluctuation of phosphorus being largely controlled.

Groundwater-surface water interactions and agricultural nutrient transport in a Great Lakes clay plain system

Nutrient export from agricultural land to surface waters is a significant environmental concern within the Great Lakes Basin (GLB). A field-based watershed-scale study was completed to investigate spatial and temporal variations of phosphorus and nitrate to assess nutrient transport pathways and groundwater-surface water interactions in an agriculturally dominated clay plain system. This was conducted in the 127 km2 Upper Parkhill Watershed, near Lake Huron in southwestern Ontario, Canada. Data collection occurred from June 2018 to May 2019 via continuous sensor deployment and discrete sampling of stream water, groundwater, hyporheic zone, and tile drainage water. Samples were analyzed for various nutrient species (total, total dissolved, soluble reactive, and particulate phosphorus, and nitrate-N) to examine the hydrological dynamics of principal transport pathways of agriculturally-derived nutrients. Total phosphorus and nitrate concentrations in stream water ranged from 0.007 to 0.324 mg/L and 0.32 to 13.13 mg NO3−-N/L, respectively. Tile drainage water total phosphorous concentrations varied from 0.006 to 0.066 mg/L. Groundwater total dissolved phosphorus concentrations ranged from <0.003 to 0.085 mg/L. Transport of phosphorus through tile drainage was observed to be greater than through groundwater over the study period. No distinct relationship was observed between nutrient concentrations in the hyporheic zone and the vertical hydraulic gradient within this zone in the studied stream reach. Preliminary correlations were discerned between water quality observations and recognized land management practices. Given the elevated stream nutrient concentrations, these results are consequential for the continual improvement of strategies and programs devised to conserve water resources within the GLB.

Temporal and Spatial Characteristics of Total Phosphorus in the Middle and Lower Yangtze River Mainstem Under New Water and Sediment Conditions

After the completion of the Three Gorges Reservoir and the upstream reservoir group of the Yangtze River, new water and sediment conditions appeared in the middle and lower reaches of the Yangtze River, and its influence on the phosphorus concentrations in water has attracted much attention. Therefore, the spatial and temporal distributions of total phosphorus (TP) concentrations in the middle and lower reaches of the mainstem under the new water and sediment conditions were studied. The results show that:① after the construction of the Three Gorges Reservoir, the concentrations of TCP (samples were allowed to settle for 30 min) in the middle and lower reaches of the Yangtze River fluctuates between 0.10 and 0.15 mg·L-1, and generally increased during 2004-2010 and then decreased during 2014-2019, and increases along the flow direction. The concentrations of dissolved total phosphorus (TDP) have slowly increased with time. ② The settleable solids influence the phosphorus content to varying degrees. The median values of TCP/TP ratio in Nanjinguan, Hankou, and 23 km below Wusongkou, are 0.900, 0.720, and 0.609, respectively, which decreases successively from upstream to downstream. The proportion of TPP (total particulate phosphorus)/TP shows an increasing trend along the flow direction. The median values of TPP/TP ratios in Nanjinguan, Hankou, and 23 km below Wusongkou were 0.439, 0.567, and 0.738, respectively. ③ According to the "Environmental quality standard for surface water GB 3838-2002", the water quality was assessed using TCP concentrations, and the assessment results showed that the water quality of the middle and lower reaches of the Yangtze River was generally good. However, considering the influence of settleable solids, the water quality categories assessed based on TP concentrations would be worse, especially near estuaries. ④ In the middle and lower reaches of Yangtze River, there is little difference in the phosphorus concentration of different monitoring sites in the upper section of main stream; however, the difference is obvious near the estuary. ⑤ The concentration of TCP in the coastal waters of the urban river section of the middle and lower reaches of the Yangtze River is significantly higher than that of the main channel, and there are obvious coastal pollution zones in the coastal waters of the urban river section.

Pulp and paper mill sludges decrease soil erodibility.

Declining carbon (C) content in agricultural soils threatens soil fertility and makes soil prone to erosion, which could be rectified with organic soil amendments. In a 4‐yr field trial, we made a single application of three different organic sludges from the pulp and paper industry and studied their effects on cereal yield, soil C content, and fungal and bacterial composition. In laboratory rainfall simulations, we also studied the effects of the soil amendments on susceptibility to erosion and nutrient mobilization of a clay‐textured soil by measuring the quality of percolation water passing through 40‐cm intact soil monoliths during 2‐d rainfall simulations over four consecutive years after application. A nutrient‐poor fiber sludge reduced wheat yield in the first growing season, but there were no other significant effects on cereal yield or grain quality. An input of ∼8 Mg ha−1 C with the soil amendments had only minor effects on soil C content after 4 yr, likely because of fast microbe‐mediated turnover. The amendments clearly changed the fungal and bacterial community composition. All amendments significantly reduced suspended solids (SS) and total phosphorus (TP) concentrations in percolation water. The effect declined with time, but the reduction in SS and TP was still >25% 4 yr after application. We attributed the lower tendency for particle detachment in rain simulations to direct interactions of soil minerals with the added particulate organic matter and microbe‐derived compounds that stabilize soil aggregates. In soils with low organic matter content, pulp and paper industry by‐products can be a viable measure for erosion mitigation.

Impacts of soil use and management on water quality in agricultural watersheds in Southern Brazil

AbstractWorldwide, agriculture is considered one of the main activities that influence water quality. The objective of this work was to evaluate the influence of soil use and management on water quality at the small watershed scale, in Southern Brazil. One watershed is characterized by production of annual crop seeds under no‐tillage (zero tillage), with crop rotation and with terraces (Sarandi watershed—SW), while the other is characterized by production of grains in the summer and pasture with grazing in the winter, under no‐tillage, without crop rotation and without terraces (Coxilha watershed—CW). Flow and climatic data were measured during 2 years. Water samples were manually taken at precipitation events and base flow over 1 year for laboratory analysis. During events of high volume, most of the rainfall was converted to base flow in SW, while in CW, most of the rainfall was transformed into overland flow. Overall, higher concentrations and losses of sediments and nutrients occurred in the CW, mainly during precipitation events in the winter crops season. Of the total nitrogen concentration in water, approximately 3% was ammonium‐N and 58% was nitrate‐N, on average, in both watersheds. For total phosphorus concentration in water, more than 75% was particulate in both watersheds, however, the bioavailable phosphorus accounted for 70% of the total phosphorus in the SW and for 35% in the CW. The higher concentration of bioavailable phosphorus in the SW indicates a short‐term pollution potential, but in both watersheds, the water quality was impaired by the high concentrations of total phosphorus. In general, even with no‐tillage, the results highlight the importance of best management practices as terracing, riparian vegetation, crop rotation, better crop systems and fertilizer management to avoid degradation of water resources.

Establishing an empirical equation for the relationship between total suspended solids and total phosphorus concentrations in the downstream Red river water

Recently, the Asian rivers have faced the strong reduction of riverine total suspended solids (TSS) flux due to numerous dam/reservoir impoundment. The Red river system is a typical example of the Southeast Asian rivers that has been strongly impacted by reservoir impoundment in both China and Vietnam, especially in the recent period. It is known that the reduction in total suspended solids may lead to the decrease of some associated elements, including nutrients (N, P, Si) which may affect coastal ecosystems. In this paper, we establish the empirical relationship between total suspended solids and total phosphorus concentrations in water environment of the Red river in its downstream section from Hanoi city to the Ba Lat estuary based on the sampling campaigns conducted in the dry and wet seasons in 2017, 2018 and 2019. The results show a clear relationship with significant coefficient between total suspended solids and total phosphorus in the downstream Red river. It is expressed by a simple equation y = 0.0226x0.3867 where x and y stand for total suspended solids and total phosphorus concentrations (mg/l) respectively with the r2 value of 0.757. This equation enables a reasonable prediction of total phosphorus concentrations of the downstream Red river when the observed data of total suspended solids concentrations are available. Thus, this work opens up the way for further studies on the calculation of the total phosphorus over longer timescales using daily available total suspended solids values.

Object-Based Modeling of Marine Phytoplankton and Seaweeds

The aim of this work is to simulate the dissolved oxygen deficiency in the coastal zone that sometimes occurs during the summer water stagnation. We consider the main components of the marine ecosystem that play a major role in such processes—concentrations of nitrogen, phosphorus and sulfur compounds in water, dissolved and particular organic matter, oxygen, biomass of phytoplankton and macroalgae. We use the object-based modeling technique to simulate the spatio-temporal variability of the ecosystem in a 2D domain. In comparison with the traditional approach, it gives several advantages: more precise parametrizations of the biological components’ functionality; higher spatial resolution; possibility to account for the individual variability of hydrobionts; easy inclusion of an arbitrary number of species in the model. Our model included three species of phytoplankton and seven macroalgae. Individual-based modules control their functionality. Species of phytoplankton and seaweeds chosen for simulations are typical for the coastal zone of Crimea. In the simulations, we study the contribution of micro- and macroalgae to the processes of self-purification of a semi-enclosed basin in case of a sharp increase in nutrient concentration in water.

Long-Term Dynamics of Nitrogen and Phosphorus Concentrations in Subsoil Water in Ivankovo Reservoir Drainage Basin

The article presents the results of summer dry-season areal surveys of subsoil water chemistry in the drainage basin of the Ivankovo Reservoir in the Volga segment from Tver City to Dubna City over period 1981–2019. The zone of subsoil water pollution by nutrients has shifted from the anthropogenic landscapes of agricultural fields to residential areas: horticultural and cottage settlements. Local zones of subsoil water pollution by nutrients still persist under fertilized fields and large cattle farms. The long-term dynamics of the major diffuse pollution sources and the regime of nutrients in the Ivankovo Reservoir are discussed.

Perspectives on Microalgal Biofilm Systems with Respect to Integration into Wastewater Treatment Technologies and Phosphorus Scarcity

Phosphorus is one of the non-renewable natural resources. High concentration of phosphorus in surface water leads to undesirable eutrophication of the water ecosystem. It is therefore necessary to develop new technologies not only for capturing phosphorus from wastewater but also for phosphorus recovery. The aim of the study was to propose three different integration scenarios for a microalgal biofilm system for phosphorus removal in medium and small wastewater treatment plants, including a comparison of area requirements, a crucial factor in practical application of microalgal biofilm systems. The area requirements of a microalgal biofilm system range from 2.3 to 3.2 m2 per person equivalent. The total phosphorus uptake seems to be feasible for construction and integration of microalgal biofilm systems into small wastewater treatment plants. Application of a microalgal biofilm for phosphorus recovery can be considered one of the more promising technologies related to capturing CO2 and releasing of O2 into the atmosphere.

Role of rhizospheric microorganisms in mitigating the adverse effect of salinity stress in Plantago ovata growth, biochemical and photosynthetic traits

ABSTRACT This pot experiment was carried out to investigate the efficiency of plant rhizospheric microorganisms (PRMs) to counteract salinity stress in Plantago ovata. The treatments included soil salinity (2.5 (as control), 5 and 10 dS m−1), arbuscular mycorrhizal fungi (Control, Glomus mosseae, Rhizophagus intraradices and Funneliformis mosseae) and phosphate solubilizing bacteria (Control and Pseudomonas fluorescens). The highest amount of growth and yield parameters, relative water content (RWC), potassium (K+) and phosphorus (P) concentration, photosynthetic traits (chlorophyll a and b, carotenoid, maximal efficiency of PSII (fv/fm), variable fluorescence to initial fluorescence (fv/f0) and stomatal conductance (gs)), antioxidant enzymes and the lowest sodium (Na+) concentration, malondialdehyde (MDA) and electrolyte leakage were observed in the plants treated with mixture of Rhizophagus intraradices and Pseudomonas fluorescens under all salinity levels. Although all previously mentioned traits significantly and severely decreased under salinity stress, mucilage percentage, electrolyte leakage and Na+ concentration were increased under salinity levels. In conclusion, the results suggested that inoculation of AMF (particularly Rhizophagus intraradices) in combination with Pseudomonas fluorescens by the accumulation of proline along with decreased electrolyte leakage, maintenance of relative water content in leaves and selective uptake of K+ ions could overcome detrimental effects of salinity stress in isabgol. Abbreviations AMF: arbuscular mycorrhizal fungi; APX: ascorbate peroxidase; CAT: catalase; Chl: chlorophyll; CAR: carotenoids; ECe: electrical conductivity of soil saturation extract; EL: Electrolyte leakage; Fv/Fm: maximal efficiency of PSII; gs: stomatal conductance; Fv/F0: variable fluorescence to initial fluorescence; K+: potassium; MDA: malondialdehyde; Na+: Sodium; PGPR: plant growth-promoting rhizobacteria; P: phosphorus; PRM: plant rhizospheric microorganisms; PSB: phosphate solubilizing bacteria; RWC: relative water content; SOD: superoxide dismutase

Suitable plant combinations for ecological floating beds in eutrophic subtropical coastal wetlands under different salinities: experimental evidences

The ecological restoration of coastal wetlands to remediate eutrophication has attracted attention worldwide. Although ecological floating beds have been widely used in freshwater ecosystems, selecting suitable plant combinations in coastal ecosystems where salinity changes dramatically remains a challenge. In this study, a controlled experiment was conducted to explore suitable plant species combinations with high purification efficiency and landscape aesthetics for ecological floating beds under different salinities. A total of seven plant combinations were planted in ecological floating beds in artificial eutrophic water with either freshwater or saline water (about 15 psu). After 6 weeks of growth, the concentration of nitrogen and phosphorus in water decreased significantly. Based on water purification efficiency, plant growth performance and landscape aesthetics, the combination with two freshwater plant species (Lythrum salicaria + Phragmites australis) and one mangrove species (Kandelia obovata) was identified as the optimal choice for low-salinity wetland habitats, whereas the combination with two mangrove species (Kandelia obovate + Bruguiera gymnorhiza) and one freshwater plant species (Canna indica) was the best for brackish wetland environments. With the proper designs, the ecological floating beds containing these plant combinations can be applied to the wetland restoration projects for both purification and beautification of coastal wetlands under the frequent influence of eutrophic and tidal water.

Forms of Nitrogen and Phosphorus in Suspended Solids: A Case Study of Lihu Lake, China

Suspended solids are an important part of lake ecosystems, and their nitrogen and phosphorus contents have a significant effect on water quality. However, information on nitrogen and phosphorus forms in suspended solids remains limited. Therefore, a case study was conducted in Lihu Lake (China), a lake with characteristically high amounts of suspended solids. Nitrogen and phosphorus speciation in suspended solids was analyzed through a sequential extraction method. We also evaluated the sources of various forms of nitrogen and phosphorus and their different effects on eutrophication. The total nitrogen (TN) content was 758.9–3098.1 mg/kg. Moreover, the proportions of various N forms in the suspended solids of the study areas were ranked as follows: Hydrolyzable nitrogen (HN) &gt; residual nitrogen (RN) &gt; exchangeable nitrogen (EN). Total phosphorus (TP) ranged from 294.8 to 1066.4 mg/kg, and 58.6% of this TP was inorganic phosphorus (IP). In turn, calcium (Ca)-bound inorganic phosphorus (Ca-Pi) was the main component of IP. The correlation between various nitrogen and phosphorus forms showed that there were different sources of suspended nitrogen and phosphorus throughout Lihu Lake. Correlation analysis of water quality indices and comparative analysis with surface sediments showed that in Lihu Lake, the dissolved nitrogen and phosphorus contents in water were influenced by sediment through diffusion, while particle phosphorus content in water was influenced by suspended solids through adsorption; however, due to the higher phosphorus contents in suspended solids, we should pay more attention to the impact of suspended solids.

Hedonic Price Estimates of Lake Water Quality: Valued Attribute, Instrumental Variables, and Ecological-Economic Benefits

We estimate the effect of lake water quality on residential housing prices using cross-sectional data on water clarity from 113 lakes across the United States. An instrumental-variables approach is developed to address potential endogeneity bias in the water-clarity variable. Three lake-based physical variables serve as instrumental variables: total nitrogen concentration in lake water, total phosphorus concentration in lake water, and water temperature near the lake surface. The econometric results include three methodological findings: the instruments are valid and strong; the ordinary-least-squares estimate of the coefficient on the water-clarity variable is unbiased; and water clarity is the attribute of water quality valued in the housing market. The estimated water-clarity effect shows that a one-tenth of a meter change in water clarity leads to a one-percent change in housing price, or an elasticity of 0.20 at mean clarity. Coupling this effect with estimates of an ecological production function, a lake-specific benefit index is developed that shows the effect on housing values of bringing lakes into compliance with the US Environmental Protection Agency's regional recommendations for phosphorous concentration in lake waters.