Phosphorus Content Research Articles

The Application of Resin Infiltration Combined with Nano-Hydroxyapatite in the Treatment of Post-Orthodontic White Spot Lesions

This study aims to investigate whether the combination of resin infiltration and nanohydroxyapatite (nHA) can provide a synergistic treatment for post-orthodontic white spot lesions (WSL), thus establishing an experimental basis for its treatment. For this study, a total of 60 bicuspid teeth that required extraction due to orthodontics were collected. Orthodontic models were established for each tooth sample, and demineralization staining was conducted using Coca-Cola. The dental samples were randomly divided into 4 groups: control group, nHA group, resin infiltration group, and resin infiltration+nHA group. The demineralized samples were remineralized with 10% nHA and Icon resin infiltration, respectively. The samples were subjected to color difference observation, microhardness test, energy-dispersive X-ray spectrum analysis, and surface roughness detection. The results showed that the tooth surface of the control group was rough and dull after demineralization. The area around the bracket exhibited a brown color, greatly contrasting with the color of the surrounding tooth enamel. After the remineralization treatment with nHA and resin infiltration, the color difference decreased significantly and the microhardness increased. A significant difference was observed between the nHA group and the resin infiltration group (P < 0.05). However, the combination of resin infiltration and nHA exhibited superior staining resistance and improved WSL microhardness value. Additionally, nHA was found to enhance the mass ratio and molar ratio of calcium to phosphorus in WSL samples, while also reducing the surface roughness Ra, demonstrating a greater effectiveness compared to resin infiltration. The use of nHA following resin infiltration led to a significant improvement in mineral deposition and a substantial reduction in surface roughness. In conclusion, both resin infiltration and nHA play a crucial role in promoting enamel remineralization, offering their respective advantages in reducing color difference, increasing microhardness and calcium and phosphorus content, and reducing surface roughness in WSL samples. Remarkably, the combined application of resin infiltration and nHA enables resin infiltration to improve the remineralization and anti-coloring ability in WSL, while preserving its aesthetic effects. This combination demonstrates a positive application outcome.

Metabolic response and clade variation in Accumulibacter under phosphorus deprivation stress

Two enhanced biological phosphorus removal systems (R1 and R2) fed with different carbon sources (acetic acid and propionic acid) were used to investigate the metabolic response of nitrite-type denitrifying phosphorus removal functional bacteria Accumulibacter to different phosphorus concentrations and the changes of its clade community structure. The results indicated that the systems almost lost the ability to release phosphorus after 15 d phosphorus deprivation, the contents of poly-P in the sludge of R1 and R2 decreased from 0.63 to 0.02 mgP/mgVSS and from 1.23 to 0.05 mgP/mgVSS, respectively. According to the analysis of stoichiometric parameters, the functional bacteria in both systems performed glycogen accumulating organism metabolism to survive under phosphorus-poor condition. Besides, the two systems exhibited a stronger EBPR ability even after 42 d phosphorus deprivation, and the maximum anoxic phosphorus uptake rate was 1.92 times and 2.29 times of those under phosphorus-rich conditions. Real-time quantitative Polymerase Chain Reaction detection indicated that the proportion of Accumulibacter in the two systems decreased from 16.45 % to 8.78 % and from 31.00 % to 8.43 %, respectively, as phosphorus was deprived. Clade IIC maintained its dominance in both systems, while clade IID was gradually washed out from propionic acid system, suggesting that clade IIC had a more flexible metabolic response to phosphorus deprivation stress.

Paleosurface studies of the remains of a building in the Mikhailovsky Cordon settlement

Pedoarchaeological study of the remains of a building on the territory of the Old Slavic site (the settlement of Mik-hailovsky Cordon — the Slavic Borshevo Culture of the late 1st mil. AD) in the Voronezh region were carried out in order to obtain new data on the layout of the settlement, the type of housing building, life sustainability, economy, and residen-tial use. The main purpose of soil research was the identification of the nature of the use of the building and the recon-struction of the economic activities in the adjacent territory. The determination of organic and mineral forms of phos-phates, urease activity, and the quantity of microorganisms of various trophic groups in the ‘natopt’ (trampled soil) at the bottom of the pit and in the soil outside of the building was carried out. It has been established that the most pro-nounced traces of economic activity have been preserved in the soils to the west of the building where the summer stove was located. In this area, the content of phosphates reached 2 mg P2O5/g soil. The soil to the northeast of the construction pit is characterized by the accumulation of organic matter, which is confirmed not only by a high content of organic phosphorus, but also by rather high quantity of saprotrophic bacteria, indicating organic contamination of the soil, which suggests the ingress of organic substrates into the soil (manure, feces, household waste). The values of many indicators of anthropogenic activity inside the building turned out to be unexpectedly low. As such, the low content of phosphates, saprotrophic bacteria and keratinophilic fungi in the analysed ‘natopt’ in the building at the bottom of the pit indicate a low intensity, or periodic use of the premises.

Ecological status of a retired mine lake in a protected dune ecosystem

ABSTRACT Ottawa Sands Lake is a retired mine lake located in a protected dune ecosystem adjacent to Lake Michigan in western Michigan, USA. Development activities are planned for the lake and surrounding land, potentially threatening the lake’s ecological health. We conducted a baseline study of water quality and macroinvertebrates, combined with exclusion cage experiments, to examine the role of predation. Our results indicated the lake’s littoral zone had good water quality with low phosphorus (mean soluble reactive phosphorus [SRP] < 5 µg/L; mean total phosphorus [TP] < 10 µg/L) and nitrogen (mean nitrate [NO3-N] = 38–190 µg/L; mean ammonia [NH3-N] = 8–19 µg/L, excluding deep hole) concentrations, high dissolved oxygen (>9.5 mg/L, excluding deep hole), and low chlorophyll a (<12 µg/L, except for 1 sampling date) concentrations. The macroinvertebrate community was dominated by 9 families, with Chironomidae the most abundant. Three environmental factors—specific conductivity, total dissolved solids, and ammonia—were significantly related, albeit weakly, to macroinvertebrate community structure. The exclusion cages did not result in a statistically significant difference in macroinvertebrate community structure, although high variance may have masked differences. Overall, Ottawa Sands Lake is a high-quality system, but development plans, including the installation of a paved trail around the lake and the implementation of a nonmotorized boating program, may result in changes. The baseline conditions outlined in this work will allow lake managers to assess the impact of development activity and add to the limited database regarding the limnology of retired mine lakes around the globe.

Functionalized Soybean Oil as a Bio-based Flame Retardant for Poly(lactic acid): Role of Phosphorus Content

Functionalized Soybean Oil as a Bio-based Flame Retardant for Poly(lactic acid): Role of Phosphorus Content

Analysis of microbial community composition and diversity in the rhizosphere of Salvia miltiorrhiza at different growth stages.

Salvia miltiorrhiza is a kind of medicinal plant with various pharmacological activities. Few studies on the composition and diversity of rhizosphere microbial communities at different growth stages have been conducted on Salvia miltiorrhiz; in particular, salviorrhiza grows in soil that has been continuously planted for 3 years. The purpose of this study was to understand the changes of soil physicochemical properties of Salvia miltiorrhiza at different growth stages, and to study the composition and diversity of rhizosphere microbial community at different growth stages. Illumina NovaSeq sequencing technology was used to analyze the bacterial 16S rRNA gene and the fungal ITS region in the rhizosphere soil of Salvia miltiorrhiza at different growth stages. The results showed that the dominant bacterial phyla in the Salvia miltiorrhiza rhizosphere were Proteobacteria, Bacteroidetes, Acidobacteria, Firmicutes, Actinobacteria, and Chloroflexi. The dominant fungal phyla were Ascomycota, Mortierellomycota, Basidiomycota, and Rozellomycota. During the growth of Salvia miltiorrhiza, the physical and chemical properties of soil changed. As the Salvia miltiorrhiza grew, the content of available phosphorus, available potassium, pH, nitrate nitrogen, and ammonium nitrogen significantly decreased. Ammonium nitrogen and nitrate nitrogen had a greater impact on the bacterial community structure in the rhizosphere than on the fungal community structure. The work was to reveal differences in the rhizosphere bacterial and fungal community structure during different growth stages of Salvia miltiorrhiza, further understand the changes of rhizosphere microbial ecological characteristics and soil physicochemical properties during the cultivation of Salvia miltiorrhiza.

Tree root-mediated soil metabolome in agroforestry enhancing the growth and quality of Panax notoginseng

Abstract Purpose The ecological cultivation of Panax notoginseng under a forest canopy relies on the coupling of the P. notoginseng growth environment and the forest ecosystem Methods In this study, six tree species, such as Platycladus orientalis (L.) Franco, were chosen to research the effects of species interactions on the growth, quality, and disease occurrence under intercropping with P. notoginseng, with single P. notoginseng serving as the control. Results Intercropping P. notoginseng with PO (Platycladus orientalis, a coniferous tree species) or with SW (Schima wallichii Choisy, a broad-leaved tree species) promoted the accumulation of P. notoginseng biomass, reduced the occurrence of root rot, improved the contents of nitrogen, phosphorus and potassium in P. notoginseng, and increased the saponin concentration. Then, 43 differentially abundant metabolites were screened in the P. notoginseng-tree intercropping system by soil metabolism analysis and compared with those in the monocropped system. Indole-3-carboxaldehyde showed a significant negative relationship with the occurrence of root rot disease and inhibited Fusarium oxysporum. In addition, 2-naphthalenesulfonic acid was significantly positively correlated with biomass and increased the dry weight in the underground part of P. notoginseng in the pot experiments. Conclusions Thus, the coniferous tree species PO and the broad-leaved tree species SW are potentially good neighbours of P. notoginseng, and soil metabolic changes may be important mechanisms for the growth and disease resistance benefits observed in the understorey of P. notoginseng.

Effect of Different Planting Density in Cocoa (Theobroma cacao l.) on Leaf Macro and Micronutrient Levels Grown under Coconut Ecosystem

An experiment investigating the impact of different cocoa densities on leaf macro and micronutrient levels within a coconut ecosystem was conducted at the Coconut Farm of the Horticultural College and Research Institute, Tamil Nadu Agricultural University, Coimbatore. The study employed a Randomized Block Design (RBD) comprising eight treatments, each replicated three times. Notably, among the various spacing configurations, T1 (3m x 1.2m) exhibited the highest levels of leaf nitrogen (1.86%), phosphorus (0.084%), potassium (1.39%), and boron (91.33 ppm) content. This suggests that under Tamil Nadu conditions, high-density planting in the T1 treatment not only resulted in elevated nutrient levels but also correlated with a notable increase in revenue. These findings underscore the potential benefits of adopting high-density planting practices in cocoa cultivation within coconut ecosystems. Further research is warranted to explore the long-term implications of spacing configurations and nutrient interactions on crop productivity and profitability.

Physicochemical analysis of deterioration affecting the darkening of rock art in Maros-Pangkep, South Sulawesi, Indonesia

This study investigates the darkening processes affecting Maros-Pangkep rock art through a comprehensive multianalytical approach. We integrate in-situ color index measurements using Nix color Pro 2 with various physicochemical characterization techniques, including optical microscopy, XRF, SEM-EDS, Raman spectroscopy, and FTIR. By examining microbial, geochemical, and anthropogenic factors on rock art pigment samples, we establish a clear correlation between the formation of blackish-gray layers and reduced chromaticity values, indicating a significant darkening process. The shift in pigment color from vibrant red or purple to a prevailing blackish-gray hue is attributed to surface accumulation. Surface morphology analysis reveals distinct blackish deposits and delicate white fibrous structures on darkened rock art. Elemental composition analysis demonstrates heightened blackish deposit formation and increased phosphorus content in darkened samples. SEM-EDS characterization exposes gypsum morphology, with filament-like structures prevailing in heavily darkened samples, highlighting the role of both geochemical and microbial factors in deposit layer formation. FTIR spectra results confirm the presence of gypsum minerals, which are attributed to the substrate minerals and/or mineral weathering product, and unveil the existence of organic compounds, indicating microbial activity. Additionally, Raman spectroscopy reveals the anthropogenic contribution, notably soot deposition produced by human activities, to the darkening of rock art. This study underscores the need for a holistic preservation approach addressing natural, human, and microbial impacts on cultural heritage sites. Further research is also needed to conduct cross-sectional stratigraphical analysis to understand the accurate mechanism of the deterioration process on the rock art. Moreover, excavation measures regarding the possible relationship of soot deposition with human activities are also important to be carried out at the sites.

Extending grazing time during the warm season can reduce P limitation and increase the N cycling rate in arid desert steppes

Ecological stoichiometry serves as a valuable tool for comprehending biogeochemical cycles within grassland ecosystems. The impact of grazing time on the concentration and stoichiometric characteristics of carbon (C), nitrogen (N), and phosphorus (P) in desert steppe ecosystems remains ambiguous. This research was carried out in a desert grassland utilizing a completely randomized experimental design. Four distinct grazing time treatments were implemented: fenced grassland (FG, control), delay to start and early to end grazing grassland (DEG), delay to start grazing grassland (DG), and traditional grazing grassland (TG). The patterns of C, N, and P concentrations and their stoichiometry in various components of the ecosystem, as well as their driving factors under different grazing times were examined. The results showed that grazing time positively influenced C and N concentrations in leaves, while negatively affecting N concentrations in roots. TG had a significant positive effect on soil P concentrations but a negative effect on soil C:P and N:P ratios. Plant C:N, C:P, and N: P ratios were mainly influenced by N and P. The soil C:N ratio was primarily influenced by soil N, the soil C:P ratio was affected by both soil C and P, and the soil N:P ratio was influenced by both soil N and P. The growth of plants in desert steppes is mainly limited by P; however, as grazing time increased, P limitation gradually decreased and the N cycling rate increased. C-N, C-P, and N-P in various plant organs and soils demonstrated significant anisotropic growth relationships at different grazing times. Soil organic carbon, pH, and soil total phosphorus were the main driving factors that affected changes in ecological C:N:P stoichiometry. These results will help improve grassland management and anticipate the response of grassland systems to external disturbances with greater accuracy.

A novel integrated approach employing Desertifilum tharense BERC-3 for efficient wastewater valorization and recycling for developing peri-urban algae farming system

Peri-urban environments are significant reservoirs of wastewater, and releasing this untreated wastewater from these resources poses severe environmental and ecological threats. Wastewater mitigation through sustainable approaches is an emerging area of interest. Algae offers a promising strategy for carbon-neutral valorization and recycling of urban wastewater. Aiming to provide a proof-of-concept for complete valorization and recycling of urban wastewater in a peri-urban environment in a closed loop system, a newly isolated biocrust-forming cyanobacterium Desertifilum tharense BERC-3 was evaluated. Here, the highest growth and lipids productivity were achieved in urban wastewater compared to BG11 and synthetic wastewater. D. tharense BERC-3 showed 60–95% resource recovery efficiency and decreased total dissolved solids, chemical oxygen demand, biological oxygen demand, nitrate nitrogen, ammonia nitrogen and total phosphorus contents of the water by 60.37%, 81.11%, 82.75%, 87.91%, 85.13%, 85.41%, 95.87%, respectively, making it fit for agriculture as per WHO's safety limits. Soil supplementation with 2% wastewater-cultivated algae as a soil amender, along with its irrigation with post-treated wastewater, improved the nitrogen content and microbial activity of the soil by 0.3–2.0-fold and 0.5-fold, respectively. Besides, the availability of phosphorus was also improved by 1.66-fold. The complete bioprocessing pipeline offered a complete biomass utilization. This study demonstrated the first proof-of-concept of integrating resource recovery and resource recycling using cyanobacteria to develop a peri-urban algae farming system. This can lead to establishing wastewater-driven algae cultivation systems as novel enterprises for rural migrants moving to urban areas.

A preliminary study on calcifying nanoparticles in dental plaque: Isolation, characterization, and potential mineralization mechanism.

Calcifying nanoparticles (CNPs), referred to as nanobacteria (NB), are recognized to be associated with ectopic calcification. This study aims to isolate and culture CNPs from the dental plaque of patients with periodontal disease and investigate their possible role in unravelling the aetiology of periodontal disease. Supragingival and subgingival plaques were sampled from 30 periodontitis patients for CNPs isolation and culture. Alkaline phosphatase (ALP) content changes were tracked over time. Positive samples underwent thorough morphological identification via hematoxylin and eosin (HE) staining, Alizarin red S (ARS), and transmission electron microscopy (TEM). The chemical composition of CNPs analysis involved calcium (Ca) and phosphorus (P) content determination, Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). The subgingival plaque dental group exhibited a higher CNPs isolation rate at 36.67% (11/30) compared to the supragingival dental plaque group at 66.67% (20/30). ALP activity varied among the positive, negative and control groups. Morphological observation characterized the CNPs as round, oval, and ellipsoid particles with Ca deposits. Chemical analysis revealed the Ca/P ratio was 0.6753. Hydroxyl, methyl, carbonate, phosphate, hydrogen phosphate, and dihydrogen phosphate were detected by FTIR; the main chemical components detected by XRD were hydroxyapatite and tricalcium phosphate. CNPs were found in periodontitis-related dental plaque and exhibited the potential to develop calcified structures resembling dental calculus. However, the potential involvement of ALP in CNPs formation requires deeper exploration, as does the precise nature of its role and the interrelation with periodontitis demand a further comprehensive investigation.

Connecting past, present, and future trends of hydraulic and phosphorus loading in the Bay of Quinte tributaries, Ontario, Canada

Study regionThe Bay of Quinte watershed, located on the northeastern shore of Lake Ontario, Canada. Special focus is placed on the Napanee River and Wilton Creek catchments, where the presence of a subterranean network of conduits that facilitate groundwater-surface water interactions is conducive to an increase in the delivery of nutrients during storm events and can exacerbate the risk of eutrophication. Study focusDevelopment of a rigorous modelling framework that can advance our understanding of past and present trends of streamflow and tributary phosphorus (P) concentration and loads. We also analyze future streamflow rates and P export trends in order to guide the long-term watershed management in the area. Our analysis is carried out through a comprehensive combination of data-driven and process-based models. Novel hydrological insights for the regionRetrospective analysis provides evidence of a recent increase in the impact of nonpoint-source P pollution. General Circulation Models suggest a future increase in both temperature minima and maxima relative to present conditions (2002–2018). Precipitation projections are indicative of increased frequency of occurrence of high extreme precipitation events during the summer and mid-fall, when the Bay of Quinte is more susceptible to undesirable ecological shifts. Our study predicts a seasonality shift in the streamflow, with the spring freshet occurring earlier in the year accompanied by higher flow rates in the local creeks for the winter and early spring. We also examined the relationship between precipitation and streamflow across varying levels of flow regulation. Our analysis indicates that our predictive capacity declines with increased flow regulation as well as when streamflow rates are predicted by contemporaneous precipitation values.

Well-designed flame retardants for epoxy resin composites that simultaneously improve heat resistance, mechanical properties and fire safety

Epoxy resin (EP) flammability severely limits its application in some industrial fields, while flame retardant epoxy resin (FREP) often suffers from the problem of not being able to balance flame retardant properties with mechanical properties. To solve the problem, in this work, HDP, a reactive flame retardant was succeeded in synthesizing by the one-pot method using protocatechuic aldehyde (PH), 2,4-diamino-6-phenyl-1,3,5-triazine (DPT), and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) as reactive monomers, was used to improve the flame retardancy of EP. And evaluated the effect of HDP on the curing reaction, heat resistance and mechanical property of EP. The introduced of four phenolic hydroxyl groups and two secondary amine groups enhanced the compatibility of the flame retardant HDP in EP and improved process performance. The apparent activation energy (Ec) was reduced by 8.1 %, facilitating the curing of EP/DDM. When 5 wt% of HDP (with only 0.36 wt% phosphorus content) was added to EP, the flexural strength and modulus of FREP increased by 21.0 % and 14.9 %, respectively, and the Tg increased by 9.0 % compared to EP. Cone calorimeter test (CCT) data showed that compared to EP, samples of EP/HDP-5 showed a 14.5 % and 21.6 % reduction in total heat release (THR) and total smoke production (TSP), respectively, and a 13.7 % increase in coke yield (CY). EP/HDP-5 has a high limited oxygen index (32.5 %) and passes the UL-94 V-0 classification. The excellent char formation and flame retardancy was owed to the dual role of the condensed and gas phases of FREP in the combustion process.

Exploring the Trends in Sediment and Phosphorus Concentrations and Loads in Part of the Canadian Great Lakes Basin

Exploring the Trends in Sediment and Phosphorus Concentrations and Loads in Part of the Canadian Great Lakes Basin

Comparative analysis of foliar galls and ungalled leaves of Alstonia scholaris with a focus on tissue ultrastructure and phytochemistry

Plant-insect interactions where the insect changes the course of host-plant growth by building a new structure called as a “gall” to protect and nourish the growing insect continue to fascinate scientists. Alstonia scholaris, a medicinal plant extensively used in Indian Traditional Medicine has shown to have such interactions with insect Pauropsylla tuberculata Crawford producing numerous galls on the plant leaves. This intricate and poorly understood natural relationship demands further investigation to unravel the distinctions between gall tissue and unaffected leaves. We examined the tissue ultrastructure by scanning electron microscope (SEM) and phytochemistry by thin layer chromatography and liquid chromatography - high resolution mass spectrometry to understand variations between the gall tissues and ungalled leaves of A. scholaris. The data showed dense population of sclereids in the gall tissues in addition to parenchyma cells. The concentration of aluminium, phosphorus and carbon were found to be reduced in the galls while cobalt and oxygen were increased. The SEM images gives insight into the ecological relationship between these species. The phytochemical analysis indicated not only enrichment of alkaloids and terpenoids in the gall tissues but also observed several novel peaks with unreported masses indicating a potential reservoir of bioactive phytochemicals.

Predicting the chemical composition of pet food with hyperspectral imaging

Performing fast analyses to control the nutritional quality of pet food products is of great interest in the pet food industry. The purpose of this study was to test the efficacy of near-infrared hyperspectral imaging (HSI) in determining chemical composition content of cat and dog food, and evaluate the influence of mixed model and characteristic wavelength on the performance of the quantitative model. Seventy cat food and thirty-six dog food samples were characterised using reference methods for moisture, crude protein (CP), crude fat (CF), crude fibre (CFe), crude ash (CA), calcium (Ca) and total phosphorus (TP) content. The Partial Least Squares regression (PLSR) was used to establish the quantitative models that involved the cat food model and mixed model. The characteristic wavelength was selected using a competitive adaptive reweighted-sampling (CARS) algorithm. Results showed that, except for CFe, the performance of the cat food model was similar to the mixed model. When using feature band, the prediction results of the mixed models for CP, CF, moisture, and CFe were optimized with R2p between 0.73 and 0.96 and RPD in the range 2.22–5.20, but the prediction results of TP, CA, and Ca did not meet the actual demand. Optimal quantitative models were used to visualise the sample chemical composition distributions. The results of this study provide theoretical and technical support for the rapid online quality control of pet food.

Potential of artificial soil preparation for vegetation restoration using red mud and phosphogypsum

Red mud and phosphogypsum have long been a focus and challenge in global industrial waste management, and their low-cost and large-scale utilization technology has always been an urgent need. This study is based on the strong acid-base neutralization reaction between red mud and phosphogypsum, which contain an elemental composition similar to that of natural soil, red mud itself has characteristic of clay minerals, and other auxiliary materials (i.e. rice husk powder, bentonite, fly ash, polyacrylamide flocculant and microbial suspension) were added, so as to explore the potential of synergistically prepared artificial soil for vegetation restoration. The results showed that the artificial soils exhibited physicochemical characteristics (e.g., pH, moisture content, cation exchange capacity) similar to those of natural soil, along with abundant organic matter, nitrogen, phosphorus, and potassium contents, meeting the growth requirements of plants. The artificial soils were able to support favorable growth of suitable plants (e.g., sunflower, wheat, rye grass), accumulating high levels of diverse enzymatic activities, comparable to those in natural soils (e.g., catalase, urease, phosphatase), or even surpassing natural soils (e.g., sucrase), and rich microorganism communities, such as Cyanobacteria, Proteobacteria, Actinobacteria in the bacteria domain, and Ascomycota in the fungi domain, were initially developed. It's suggested that preparing 1 ton of artificial soil entails synergistic consumption of 613.7 kg of red mud and 244.6 kg of phosphogypsum, accounting for mass proportions of 61.4 % and 24.5 %, respectively. In future, more evaluations on the leaching loss of nutrients and alkalinity and the environmental risks of heavy metals should be conducted to more references for the artificial soil application. In summary, the preparation of artificial soil is a very simple, efficient, scalable and low-cost collaborative resource utilization scheme of red mud and phosphogypsum, which has great potential for vegetation restoration in some places such as tailings field and soil-deficient depression.

Environmental indicators of lake ecosystem health in Aotearoa New Zealand: current state and trends

Assessments of lake ecosystem health, based on indicators of physical–chemical water quality, ecological conditions, and human health risks, are needed to apprise the public and facilitate lake management. While unrefereed lake water quality reports exist, this is the first peer-reviewed study to report data processing and analysis methods and results for current state and recent trends in multiple environmental indicators in monitored lakes across Aotearoa New Zealand. Lake grading based on national criteria indicated that many lakes are failing to achieve statutory bottom lines for phytoplankton chlorophyll a, total nitrogen, and total phosphorus concentrations. In contrast, most monitored lakes had high grades for two human health risk indicators, E. coli and cyanobacteria concentrations, and for potential toxicity of ammonia for biological communities. We included 166 lakes and considered indicator state and trends for two lake classifications based on geomorphology and land cover. Elevated scores for an indicator of trophic state (the trophic level index; TLI) in most shoreline, riverine, peat, landslide, dam, and aeolian lakes indicated eutrophic conditions or worse. Lower TLI scores were indicative of oligotrophic conditions in most glacial lakes. Nutrient, E. coli and suspended sediment concentrations and TLI scores were positively correlated, and Secchi depths negatively correlated, with high-intensity agricultural land cover. Ten-year trend analyses indicated that lakes with increasing Secchi disk depth, chlorophyll a, dissolved reactive phosphorus, E. coli, ammoniacal nitrogen, TLI, total nitrogen, and total suspended solids trends outnumbered those with decreasing trends. Twenty-year trend analyses indicated that the numbers of lakes with increasing and decreasing trends in most of the indicators we assessed were comparable, but lakes with increasing 20-year trends in total nitrogen outnumbered those with decreasing trends, and lakes with decreasing 20-year trends in ammoniacal nitrogen, dissolved reactive phosphorus, total phosphorus, and nitrate nitrogen outnumbered those with increasing trends. This study presents clear data processing steps and trend analysis methods as applied to a nationwide dataset for Aotearoa New Zealand, while acknowledging data limitations. For example, the choice of trend periods is challenging and can greatly affect conclusions. The results of this empirical study and the collective results of preceding studies of lake ecosystem health indicate that eutrophication poses a threat to the ecological health of many if not most lakes in Aotearoa New Zealand. Recommendations include monitoring network expansion especially for the indicators bottom dissolved oxygen and cyanobacteria (toxic and total cyanobacteria biovolumes) and judicious selection of trend periods in lake-specific trend analyses to determine causes for increasing or decreasing trends in environmental indicators.

Perspectives on total phosphorus response in rivers: Examining the influence of rainfall extremes and post-dry rainfall

Eutrophication is a significant environmental problem caused by nutrient loads from both point and non-point sources. Weather variables, particularly precipitation, affect the concentration of nutrients in water bodies, particularly those from non-point sources, in two contrasting ways. Heavy precipitation causes surface runoff which transports pollutants to rivers and increases nutrient concentration. Conversely, increased river flow can dilute the concentration, lowering it. This study investigates the impact of extreme precipitation, prolonged precipitation, and precipitation after a dry period on the total phosphorus concentration in the Moehne and Erft rivers in Germany, given the projected increase in frequency of extreme precipitation events and long drought periods due to climate change. The study comprises two parts: selecting extreme weather days from 2001 to 2021 and comparing observed Total Phosphorus concentrations with estimated concentrations derived from Generalized Additive Models and linear regression based on the discharge-concentration relationship. Changes in river TP concentration in response to continuous precipitation and precipitation after a dry period were also studied. Our results showed that during wet extreme and post-dry period rainfall events, TP concentration consistently surpassed expected values, underscoring the profound influence of intense rainfall on nutrient mobilization. However, we observed the impact of continuous rainfall to be non-unidirectional. Our work is distinguished by three key innovations: 1) addressing limitations in studying the effects of extreme weather on water quality due to limited temporal resolution, 2) incorporating both linear and non-linear modeling approaches for discharge-concentration relationships, and 3) performing a comprehensive analysis of temporal and spatial patterns of Total Phosphorus concentrations in response to varying rainfall patterns.