Nutrient Fractions Research Articles

Effect of 67-years of manuring, fertilization and amendments on fractions of soil organic carbon, nutrient dynamics and yield sustainability in an acidic Alfisol

Amending a problem soil in addition to nutrient input is crucial for maintaining a healthy and productive soil in the long run. The study aimed at evaluating the long-term impact of manuring and fertilization with or without liming on different soil attributes and crop yield in an acidic Alfisol. Surface soil samples (0–15 cm) were collected from selected 7 treatments, viz. Control; N; FYM; ½(N+FYM)+PX/2+KY/2; NPK; NPK+L; and P(A-X)K(B-Y)+FYM+L of the Permanent Manurial Trial (PMT) of Birsa Agricultural University, Ranchi, after the harvesting of rainy (kharif) maize (Zea mays L.) at the 67th crop cycle (2023 and 2024) and assessed for various fractions of soil organic carbon (SOC), available nutrients and yield attributes. The experiment was laid out in a randomized block design (RBD) and replicated thrice. The treatments which received manures either alone or in combination with chemical fertilizers recorded significantly higher amount of all the fractions of SOC, available nitrogen and lower bulk density as compare to the unfertilized plot or treatment with inorganic alone. The study also revealed that, addition of lime helped maintaining an optimum pH level, enhanced microbial activities and nutrient availability in the soil leading to a higher crop yield. Therefore, integrated use of manures and fertilizers in addition to lime for a prolonged period would have significant positive impact on soil health and sustaining its productivity.

Divergent Effects of Grazing Intensity on Soil Nutrient Fractions in Alpine Meadows

ABSTRACTLarge herbivore grazing plays a key role in regulating ecosystem functioning and nutrient cycling in terrestrial ecosystems. However, the effects and mechanisms of large herbivore grazing intensity on soil nutrient fractions remain largely unclear in alpine grasslands. Here, we determine 20 indicator variables associated with soil nutrient fractions (e.g., particulate organic carbon, POC; mineral‐associated organic carbon, MAOC) to investigate how grazing intensity on labile fractions through a well‐controlled grazing experiment in an alpine meadow on the eastern Tibetan Plateau. Our results show that microbial biomass carbon, dissolved organic carbon, light fraction organic carbon, microbial biomass nitrogen and phosphorus, total potassium, and available potassium significantly decrease with increased grazing intensity, whereas other fractions (e.g., POC, MAOC, dissolved organic nitrogen, ammonium nitrogen, nitrate nitrogen, available nitrogen, etc.) have marginal or non‐significant responses to grazing intensity. Further analysis reveals that above‐and below‐ground biomass, soil moisture, and soil pH jointly determine the grazing effects on soil nutrient fractions, without the impact of species richness. Moreover, correlation analyses indicate that grazing intensity decouples carbon and nitrogen from phosphorus and potassium in alpine meadows. Collectively, our results emphasize the importance of grazing intensity effects on nutrient cycling in alpine grasslands and incorporate the impacts of grazing intensity into terrestrial ecosystem models may help accurately predict carbon sequestration potential in grazinglands.

Intra‐annual dynamics of soil and microbial C, N, and P pools in a Central Amazon Terra Firme forest

AbstractBackgroundTropical ecosystem functioning is influenced by seasonal fluctuations in precipitation, but the impact on soil nutrient cycling and microbial stoichiometry is not fully understood.AimThis study investigates the magnitude of intra‐annual fluctuations in nutrient availability and microbial biomass in a tropical forest soil by examining carbon (C), nitrogen (N), and phosphorus (P) pools.MethodsWe analyzed the total, extractable, and microbial C, N, and P contents and their stoichiometry in Terra Firme Ferralsols, representative for the central Amazon basin.ResultsWe observed intra‐annual variations in resource availability, particularly between wet and dry seasons. Despite relatively stable total C, N, and P stocks throughout the year, we observed a decrease in extractable organic C and available (Olsen) P and an increase in extractable N in the dry season compared to the wet season. Microbial biomass pools and stoichiometry also varied across sampling dates and soil depths: relative to microbial‐C and ‐N, microbial‐P decreased in both wet and dry season and increased in the transition from wet to dry season.ConclusionsOur research highlights intra‐annual variation in nutrient pools, particularly dynamic microbial carbon and nutrient fractions, in weathered tropical forest soils.

Impact of copper sulphate treatment on cyanobacterial blooms and subsequent water quality risks

Control of algal blooms and associated biologically-induced water quality risks in drinking reservoirs is problematic. Copper sulphate (CuSO4) treatment is one intervention that has been utilised for >100 years. Evidence indicates a favourable short-term reduction in Cyanobacterial biomass (e.g. bloom termination), but here we indicate that it may also increase longer-term water quality risk. In 2022, we investigated the impacts of CuSO4 spraying on Cyanobacterial communities and nutrient levels within a drinking water supply reservoir using environmental DNA (eDNA) to assess community shifts, alongside monitoring nutrient fractions, orthophosphate (OP) and total phosphate (TP), post-treatment. CuSO4 application successfully reduced Cyanobacterial abundance, however elimination of Cyanobacteria resulted in a shift in bacterial dominance favouring Planctomycetota throughout the summer and a combination of Actinobacteriota and Verrucomicrobiota, throughout autumn. As Cyanobacterial abundance recovered post-treatment, Cyanobacterial genera demonstrated greater diversity compared to only three Cyanobacterial genera present across samples pre-treatment, and included taxa associated with water quality risk (e.g. taste and odour (T&O) metabolite and toxin producers). The increase in Cyanobacteria post-treatment was attributed to an increase in biologically available nutrients, primarily a significant increase in OP. Overall, findings suggest that the significant shift in biodiversity likely induces a less stable ecosystem with greater plasticity of response to changing environmental and biogeochemical variables. Legacy implications of CuSO4 spraying, in terms of shifts in ecosystem and nutrient balance over time, may have implications for drinking water quality, but importantly also for reservoir management options. As such, the effects of CuSO4 spraying should be considered carefully before consideration as a contender for in-reservoir biological control.

Effect of Different Fertilizer Types on Quality of Foxtail Millet under Low Nitrogen Conditions.

In order to clarify the effect of different fertilizers on foxtail millet quality under low nitrogen conditions, we used JGNo.21 and LZGNo.2 as experimental materials and set up five treatments, including non-fertilization, nitrogen, phosphorus, compound, and organic fertilizers, to study the regulation of different fertilizer types on agronomic traits, nutrient fractions, and pasting characteristics of foxtail millet under low nitrogen conditions. Compared with the control, all of the fertilizers improved the agronomic traits of JGNo.21 to a certain extent. Nitrogen and compound fertilizer treatments reduced the starch content of JGNo.21; the starch content was reduced by 0.55% and 0.07% under nitrogen and compound fertilizers treatments. Phosphorus and organic fertilizers increased starch content, and starch content increased by 0.50% and 0.56% under phosphorus and organic fertilizer treatments. The effect of each fertilizer treatment on protein content was completely opposite to that of starch; different fertilizer treatments reduced the fat content of JGNo.21 and increased the fiber content. Among them, nitrogen and phosphorus fertilizers increased the yellow pigment content; the yellow pigment content increased by 1.21% and 2.64% under nitrogen and phosphorus fertilizer treatments. Organic and compound fertilizers reduced the content of yellow pigment; the yellow pigment content was reduced by 3.36% and 2.79% under organic and compound fertilizer treatments. Nitrogen and organic fertilizers increased the fat content of LZGNo.2; the fat content increased by 2.62% and 1.98% under nitrogen, organic fertilizer treatment. Compound and phosphorus fertilizer decreased the fat content; the fat content decreased by 2.16% and 2.90% under compound and phosphorus fertilizer treatment. Different fertilizer treatments reduced the cellulose and yellow pigment content of LZGNo.2. The content of essential, non-essential, and total amino acids of JGNo.21 was increased under compound and nitrogen fertilizer treatments and decreased under organic and phosphorus fertilizer treatments. The content of essential, non-essential, and total amino acids of LZGNo.2 was significantly higher under compound, nitrogen, and organic fertilizer treatments compared with control and significantly decreased under phosphorus fertilizer treatments. Nitrogen and compound fertilizer treatments significantly reduced the values of peak viscosity, trough viscosity, breakdown viscosity, final viscosity, setback viscosity, and pasting time of each index of JGNo.21; phosphorus and organic fertilizer treatments improved the values of each index. In contrast, the pasting viscosity of LZGNo.2 increased under phosphorus fertilizer treatment and decreased under nitrogen fertilizer treatment. Reasonable fertilization can improve the quality of foxtail millet, which provides a scientific theoretical basis for improving the quality of foxtail millet.

Effects of probiotic on growth and production of brown midrib sorghum mutant line (Sorghum bicolor L. Moench) in ultisol

This study aims to observe the efficiency of probiotic inoculants on growth, soil fertility, and production of brown midrib (BMR) sorghum mutant lines. The experimental using a Randomized Block Design of four treatments and four blocks, P0: manure + (N, K, 0% P) + probiotic; P1: manure + (N, K, 50% P) + probiotic; P2: manure + (N, K, 75% P) + probiotic; P3: manure + (N, K, 100% P) without a probiotic (control). The dose of cow manure fertilizer is 10 tons/ha, and the doses of N, P, and K fertilizers are 120 kg/ha, 90 kg/ha, and 60 kg/ha, respectively, from urea, triple superphosphate (TSP), and potassium chloride (KCl). Parameters observed were plant morphology, biomass production, nutrient and fiber fraction content, and soil fertility. The treatment had no significant effect (P>0.05) on stem diameter, leaf length, and width, soil pH, fresh and DM production, the number of leaves, plant height, stem:leaf: panicle ratio, colony PSB, soil P-available, fiber and nutrient fractions of sorghum whole plant. The conclusion is that applying probiotics with lower phosphate fertilizer in sorghum cultivation produces growth, forage production, nutrition and fiber fraction content, and P-available and colony PSB, like 100% P fertilizer application. Probiotic bacteria could be applied as phosphate-solubilizing bacteria and reduce the application of P fertilizer on BMR sorghum in ultisol.

Evaluating the Impact of Biochemical Reactions on H2 Storage in Depleted Gas Fields

Summary Underground hydrogen storage (UHS) is an emerging technology to store energy, produced by renewable sources, in subsurface porous formations. UHS efficiency in depleted gas reservoirs can be affected by H2 biochemical degradation due to interactions with rock, brine, and gas. In the reservoir, subsurface microorganisms can metabolize H2 with possible hydrogen losses, H2S production, clogging, and formation damage. In this work, we investigate the impact of hydrogen losses due to microbial activities on UHS operations in depleted gas reservoirs lying in sandstone formations. We developed a workflow to exploit the chemical reactive transport functionalities of a commercial reservoir simulator, to model biochemical processes occurring in UHS. Kinetic chemical reaction formulation was used to replicate a Monod’s type microorganism growth, using PHREEQC to tune reaction parameters by matching a 0D process in an ideal reactor. Then, we applied the methodology to evaluate the impact of biotic reactions on UHS operations in depleted gas fields. Eventually, various sensitivities were carried out considering injection/production cycle lengths, cushion gas volumes, and microbial model parameters. Benchmark against PHREEQC demonstrated that, by properly tuning the kinetic reaction model coefficients, we are capable of adequately reproducing Monod-like growth and competition of different microbial community species. Field-scale results showed that hydrogen losses due to biochemistry are limited, even though this may depend on the availability of reactants in the specific environment: In this work, we focus on gas reservoirs where the molar fraction of the key nutrient, CO2, is small (≤2%) and the formation is a typical sandstone. Operational parameters (e.g., storage cycle length) have an impact on the biochemical dynamics and, then, on the hydrogen degradation and generation of undesired byproducts. Similar considerations hold for the model microbial growth kinetic parameters: In this study, they were established using available literature data for calibration, but we envisage tuning them using experimental results on specific reservoirs. The current model setup does not account for rock-fluid geochemical interactions, which may result in mineral precipitation/dissolution affecting the concentration of substrates available for biotic reactions. Nonetheless, it can provide an estimate of hydrogen consumption during storage in depleted gas reservoirs due to microbial activities. This study is among the first attempts to evaluate the impact of hydrogen losses by the presence of in-situ microbial populations during hydrogen storage in a realistic depleted gas field. The assessment was performed by implementing a novel workflow to encapsulate biochemical reactions and bacterial dynamic growth in commercial reservoir simulators, which may be applied to estimate the efficiency and associated risks of future UHS projects.

Effects of Organic Amendments and Mineral Fertilizers on Optimizing Nutrient Cycling in Alkaline Soil

Soil microbial biomass carbon (MBC) and nitrogen (MBN) are indicators of microbial size and soil fertility, representing a vital living nutrient reservoir in the soil. This study aimed to evaluate the impact of various organic sources, such as poultry manure (PM), farmyard manure (FYM), compost (CM), and biochar (BC), along with different levels of mineral fertilizers on soil microbial dynamics and nutrient (N, P) mineralization through laboratory incubation experiments. The organic amendments were applied at rates of 0.25%, 0.5%, and 1.0% of soil carbon (w/w), combined with 75%, 50%, and 25% of recommended doses of NPK (120:90 and 60 kg N, P2O5, and K2O ha-1), respectively. Following the application of amendments, the soil underwent a 16-day incubation period to measure CO2 emissions and a 28-day period for N and P mineralization. The rate of CO2 evolution exhibited a significant increase with higher carbon levels but declined over time. Compost showed the highest CO2 evolution at any given time, followed by PM, FYM, and BC, likely due to a higher readily available fraction of carbon. Compost, particularly at the 1% C level in combination with inorganic fertilizer, led to a significant increase in soil microbial biomass C and N. Nitrogen and phosphorous mineralization increased with the duration of the 28-day incubation period. However, the net release of N and P decreased with higher carbon levels, potentially associated with both immobilization and the fact that higher levels received lower (25%) NPK levels. Nevertheless, soils treated with CM and PM maintained higher levels of N and P, associated with their higher fraction of labile nutrients. These findings suggest that the continuous application of organic sources enhances N and P mineralization, soil microbial biomass, and their activity. Therefore, the regular application of carbon sources emerges as a strategic approach to improving the soil health of less fertile alkaline calcareous soils.

Nutrient metrics to compare algal photosynthetic responses to point and non-point sources of nitrogen pollution

Point- and non-point source nutrients are likely to have different ecological impacts in receiving waters, due to differences in the concentration and proportions of nutrient fractions. However, the direct comparison of their ecological impacts in receiving waters has barely been quantified. We undertook algal bioassays with algal communities from river sites and showed that there was a photosynthetic yield (Fv/Fm) response to nutrient enrichment when river nutrient concentrations were relatively low, but not at higher nutrient concentrations. To combat this variability in the photosynthetic state of algae, we developed a standardized algal bioassay (3-day), using a cultured species of algae which was starved of nitrogen, to compare the photosynthetic response to three nitrogen sources: treated wastewater, aquaculture farm discharges, and soil erosion-derived nutrient sources. This study showed that the nutrient parameter that had the highest correlation with algal photosynthetic response was total dissolved nitrogen (TDN), i.e., the sum of dissolved inorganic and organic nitrogen, rather than dissolved inorganic nitrogen alone. This was true across all three nutrient sources (R2 = 0.58–0.78). Additionally, the same concentrations of TDN from soil erosion-derived and aquaculture samples resulted in a significantly higher algal photosynthetic response, compared to the treated wastewater. This indicates that TDN from soils and aquaculture farms was significantly more bioavailable to the cultured algae than treated wastewater. When a range of parameters were correlated with algal responses, organic and inorganic nutrients, and organic carbon were the parameters that had the highest explanatory power for soil erosion-derived and aquaculture samples (R2 = 0.75–0.87). The importance of organic compounds in these equations points to the potential of microbial transformation of organic nutrients into more bioavailable forms during the 3-day bioassay. This highlights the need to understand the relationship between algal and microbial communities in natural systems for nutrient source impact assessment. This study provides an improved understanding and metrics for comparing the algal growth response to different nutrient sources.

A method to characterize precipitated minerals in organic waste and their transformation by anaerobic digestion: Focus on phosphorus

Unsustainable global phosphorus (P) management has led to the identification of digestate from anaerobic digestion (AD) as a potential source of P recovery. Understanding P interactions during AD is thus crucial for P recovery and modeling can help optimize recovery. Both understanding and modeling require accurate P fractionation into minerals that contain P, e.g., struvite, vivianite, amorphous calcium phosphate (ACP). The aim of this study was to develop a novel P fractionation method based on acidic leachate of P, Ca, Mg, Fe, K, and Al. Nine samples were acidified, three of which were digestate and six substrates used to feed a biogas unit. Acidification curves were obtained for each nutrient in each sample. Nutrient leachate was used to develop a fractionation algorithm based on P, allowing nutrient fractionation of all the samples. Dissolved nutrients during acidification were assumed to be issued from precipitated mineral origin. Precipitated P was found in all digestates, slaughterhouse sludge, and pig and cattle slurry and was originated from struvite, vivianite, and amorphous calcium phosphate (ACP) minerals. Struvite represents up to 70.6% of total P and ACP between 13.8% and 24.8% in digestates whereas vivianite was the main P precipitated form in slaughterhouse sludge (27.4%). Precipitated Mg were mainly found in samples where P was fractionated mainly as struvite. Precipitated Ca was fractionated into calcite and ACP while Fe was fractionated into vivianite and other ferrous minerals. No dissolved Al or K was found. Al was mainly fractioned as inert/organic, and K was mainly fractioned as soluble in all the samples. In conclusion, the acidification protocol and the fractionation algorithm developed in this study represent a useful, rapid and inexpensive P fractionation methodology for environmental samples during anaerobic digestion.

Fungal organic acid uptake of mineral-derived K is dependent on distance from carbon hotspot.

Fungal species are foundational members of soil ecosystems with vital contributions that support interspecies resource translocation. The minute details of these biogeochemical processes are poorly investigated. Here, we addressed this knowledge gap by probing fungal growth in a novel mineral-doped soil micromodel platform using spatially-resolved imaging methodologies. We found that fungi uptake K from K-rich minerals using organic acids exuded in a distance-dependent manner from a carbon-rich hotspot. While identification of specific mechanisms within soil remains challenging, our findings demonstrate the significance of reduced complexity platforms such as the mineral-doped micromodel in probing biogeochemical processes. These findings provide visualization into hyphal uptake and transport of mineral-derived nutrients in a resource-limited environment.

Routine monitoring of western Lake Erie to track water quality changes associated with cyanobacterial harmful algal blooms

Abstract. The western basin of Lake Erie has a history of recurrent cyanobacterial harmful algal blooms (HABs) despite decades of efforts by the United States and Canada to limit phosphorus loading, a major driver of the blooms. In response, the National Oceanic and Atmospheric Administration (NOAA) Great Lakes Environmental Research Laboratory (GLERL) and the Cooperative Institute for Great Lakes Research (CIGLR) created an annual sampling program to detect, monitor, assess, and predict HABs in western Lake Erie (WLE). Here we describe the data collected from this monitoring program from 2012 to 2021. This dataset includes observations on physicochemical properties, major nutrient fractions, phytoplankton pigments, microcystins, and optical properties for western Lake Erie. This dataset is particularly relevant for creating models, verifying and calibrating remote sensing algorithms, and informing experimental research to further understand the water quality dynamics that influence HABs in this internationally significant body of freshwater. The dataset can be freely accessed from NOAA National Centers for Environmental Information (NCEI) at https://doi.org/10.25921/11da-3x54 (Cooperative Institute for Great Lakes Research, University of Michigan and NOAA Great Lakes Environmental Research Laboratory, 2019).

Trade-offs in nutrient and sediment losses in tile drainage from no-till versus conventional till cropping systems.

Nutrient and soil loss from agricultural areas impair surface water quality globally. In the Great Lakes Region, increases in the frequency and magnitude of harmful and nuisance algal blooms in freshwater lakes have been linked to elevated phosphorus (P) losses from agricultural fields, some of which are transported via tile drainage. This study examined whether concentrations and loads of P fractions, total suspended sediments (TSS), nitrate (NO3 - ) and ammonium (NH4 + ) in tile drainage in a clay soil differed between a continuous no-till system combining cover crops and surface broadcast fertilizer (NTCC), and a more conventional tillage system with shallow tillage, fertilizer incorporation and limited use of cover crops (CT). Both sites had modest soil fertility levels. Year-round, high-frequency observations of tile drainage flow and chemistry are described over four full water years and related to management practices on the associated fields. There were similar water yields in tile drainage between the two systems; however, losses of TSS, particulate P (PP) and NO3 - were consistently greater from the CT site, which received larger quantities of fertilizer. In contrast, dissolved reactive P (DRP) losses were considerably greater from the NTCC site, offsetting the lower PP losses, such that there was little difference in TP losses between sites. Approximately 60% of the DRP losses from the NTCC site over the four years were associated with incidental losses following surface application of fertilizer in fall. This study provides insight into trade-offs in controlling losses of different nutrient fractions using different management systems. This article is protected by copyright. All rights reserved.

Ingredient fractionation for monogastric animal nutrition: the worth of sum of parts versus the whole

Basic agricultural commodities such as cereal grains, pulses and oilseeds can be fractionated into separate products that can be targeted to high value markets within or outside the feed industry. Resulting nutrient-dense fractions that are enriched in starch, protein, fat, or fibre can then be targeted to animals with different nutritional demands. These value-added nutrient fractions might be targeted at the start of fractionating the commodities or result from human food or biofuel production. Fractions enriched in fibre might be targeted to the feed, paper, or wood industries. Two categories of processes can fractionate cereals, pulses, or oilseeds: (1) an up-front process that produces solely or mostly high value ingredient fractions, or (2) a process that separates one fraction for a high-value market. Examples of category 1 include air classification and sieving. Examples of category 2 include bioethanol production from cereal grains and oil extraction from soybean and canola seed. The resulting non-human edible co-products can be fed to livestock. Dry separation is useful to produce protein-rich fractions from pulse grains. Advantages of dry over wet fractionation are continuous flow rather than batch fractionation, absence of effluents and no drying cost. However, wet fractionation creates more concentrated fractions (isolates) of the nutrient of interest, e.g., protein. Category 1 and 2 processes can occur in tandem. For example, oil can be first extracted from soybeans, resulting in soy oil and soybean meal. Subsequently, soybean meal can be fractionated into protein concentrates or isolates with greater protein content than soybean meal. Fractionation usually has at least one main fraction with a target market in food or industry processes yielding products for human use. This approach is logical, because the feed industry is focussed mostly on small margins and large volumes, whereas higher margins per unit of product can be achieved in markets for food, petfood and feed for fish or animals with high nutritional demands. Animal agriculture remains an ideal approach to convert by-products from ingredient fractionation into high value animal protein. The economic implications of value-added processing are thus important, and sustainable animal agriculture plays a key role turning waste streams into a success story. Although ingredients can be fractionated successfully for animal nutrition, especially for higher margin markets such as aquaculture, petfood or animals with high nutritional demands, most ingredients are fractionated for the human food supply or industrial processes. Using the latter approach with at least one high value fraction targeted to human food or industry and then using non-human edible fractions for feed applications, will ensure that the sum of the parts can be worth more than the whole.

Simulating the fate of compost-derived nutrients in an urban garden

The application of compost to urban vegetable gardens presents an opportunity to recycle nutrients from the urban waste stream back into the human food system. However, many gardeners apply phosphorus (P) in the form of compost at a rate that far exceeds what crops can take up. The fate of this P—whether stored in soil, taken up by plants, or exported through leachate, depends on the dynamics of water, carbon (C), and nitrogen (N) in this agroecosystem. We developed a model representing these four currencies (C, N, P, water) in urban garden soils, that was parameterized and validated using data from four years of data from an experiment in which high or low amounts of labile manure-based compost, or recalcitrant municipal compost, are added to garden plots annually. We used the model to simulate the effects of longer-term (10-year) additions of labile or recalcitrant compost at low, medium, or high levels (based on previously reported survey data for Minneapolis-Saint Paul, Minnesota), tracking the fate of added N and P, as well as calculating net C sequestration. The fraction of compost nutrients recovered over 10 years ranged from 3 to 47% (N) and 4–67% (P) with higher efficiencies associated with lower input rates and for recalcitrant compost. Approximately half of added C was ultimately respired by soil microbes, while C sequestration from crop growth was much lower than soil respiration. This model provides a tool for understanding how management decisions and climate control nutrient recycling and loss via leachate from compost application in urban agroecosystems.

Estuarine nutrient pollution impact reduction assessment through euphotic zone avoidance/bypass considerations

The feasibility of reducing nutrient pollution impact by redirecting the effluent to depths below the euphotic zone was investigated for the deep estuarine Puget Sound region of the Salish Sea in the Pacific Northwest of America. The hypothesis tested was that the thickness of the outflow layer in deep estuaries may be greater than the euphotic zone depth, allowing a fraction of nutrients to be exported out passively through the layers immediately below. The euphotic zone depth in Puget Sound varies from 8 to 25 m while the depth of the outflow layer can reach up to ≈ 60 m. Outfall relocation strategies were tested on 99% of the anthropogenic nutrient loads currently delivered to Puget Sound. The impact was quantified using the previously established biophysical Salish Sea Model, using gross primary production and exposure to low dissolved oxygen (DO) levels as the metric (< 2 mg/L for hypoxia and < 5 mg/L for impairment). Eliminating nutrient pollution (above natural) from rivers and wastewater reduced hypoxia exposure by 8.1% and 11.2%, respectively. Relocating the outfalls to deeper waters resulted in improvements, but only in the sill-less sub-basins such as Whidbey, where hypoxia and DO impairment exposure decreased (7.9% and 6.8%, respectively). The presence of multiple sills and circulation cells in Puget Sound resulted in increased exposure and rendered nutrient bypass goals unfeasible as originally envisioned. However, an alternate nutrient export pathway was identified through bottom exchange flow out of Puget Sound via Whidbey Basin and Deception Pass. An unexpected reduction in the exchange outflow magnitude (≈ 4%) due additional (22%) freshwater discharged to the estuary bottom was also noted. The potential loss in circulation strength due to rerouting of natural surface freshwater through submerged deep-water outfalls is identified as a new unforeseen anthropogenic impact.

A three-dimensional perspective of phosphorus retention across a field-buffer strip transition

Vegetated filter strips (VFS) act as buffer zones between fields and water bodies that are supposed to retain incoming runoff, sediment, and nutrients. The factors that govern nutrient retention and cycling in VFS are complex and act in all three dimensions. A key element that determines VFS effectivity is flow type, e.g., sheet vs. concentrated flow. These aspects are, however, often insufficiently accounted for in VFS research and design recommendations. In this study, we attempt to tackle these shortcomings by examining the nutrient distribution in detail at two field-VFS transitions, applying a three-dimensional sampling array together with extensive laboratory analyses. Concentrated runoff was the dominant type we found and we argue that flow convergence is the norm rather than the exception. Further complicating this issue is that entry locations of runoff may vary, calling for more sophisticated sampling designs. Overall trends were similar across the analyzed nutrient fractions (different K- and P-pools) and there were distinct trends of decreasing nutrients along the longitudinal (from the field to the VFS) and vertical planes. The horizontal plane (from outside to inside the area of concentrated flow) showed mostly inconclusive or U-shaped gradients. Both sites were similar and close to each other, nevertheless, there were significant differences that affected nutrient retention in the VFS which were linked to site-specific factors. The spatial extent (i.e., width) is often considered the main variable in VFS designs. However, other VFS traits such as vegetation type and structure, as well as external factors such as field topography and the severity of erosive events are equally important and should be attributed more significance.

Physicochemical properties of cricket (Gryllus bimaculatus) gel fraction with soy protein isolate for 3D printing-based meat analogue

Cricket (Gryllus bimaculatus) gel was fractionated and mixed with different soybean protein isolate (SPI) concentrations, and its characteristics were evaluated to determine its potential use as a meat analog. Crushed crickets were separated into the filtrate, supernatant, and pellet fractions by centrifugation and freeze-drying, and powdered and mixed with 18% SPI at different concentrations (5%–20%). The filtrate fraction had the lowest protein content and the highest fat and carbohydrate content among the nutrient fractions. Conversely, the supernatant and pellet fractions had high protein, low fat, and low carbohydrate content. SDS-PAGE detected relatively low-molecular weight proteins. Numerous muscle proteins were identified, including actin, myosin, and hemocyanin, a protein that transports oxygen in insects. Regarding the rheological characteristics of the cricket fraction, the entire fraction exhibited G'>G" in both the frequency and the temperature sweep tests, revealing a tendency for gel-like viscosity. In all cricket fractions, both G' and G" increased with increasing fraction powder concentration. When printed, supernatant fractions had no structural stability, pellet fractions had 5%–15% stability, and filtrate fractions had 5%–20% stability. The three interval thixotropy test revealed that the pellet fraction had a recovery rate of over 90% after high shear deformation. Texture profile analysis showed an increase in both hardness and chewability. After heat treatment, cohesiveness was higher than adhesiveness, indicating greater elasticity. Field-emission scanning electron microscopy results revealed that the pellet fraction was denser than the other fractions, particularly at higher concentrations. Based on the overall characteristics, 15% pellets were found to be the most appropriate fraction and concentration.

Greywater treatment in a green wall using different filter materials and hydraulic loading rates

Green walls in urban environments can be both an aesthetic feature and be of practical use in greywater treatment. This study evaluates the effect of different loading rates (4.5 l/d, 9 l/d, and 18 l/d) on the efficiency of treating actual greywater from a city district in a pilot-scale green wall with five different filter materials as substrates (biochar, pumice, hemp fiber, spent coffee grounds (SCG), and composted fiber soil (CFS)). Three cool climate plant species, Carex nigra, Juncus compressus, and Myosotis scorpioides, were chosen for the green wall. The following parameters were evaluated: biological oxygen demand (BOD), fractions of organic carbon, nutrients, indicator bacteria, surfactants, and salt. Three of the five materials investigated – biochar, pumice, and CFS - showed promising treatment efficiencies. The respective overall reduction efficiencies of BOD, total nitrogen (TN) and total phosphorus (TP) were 99%, 75%, and 57% for biochar; 96%, 58%, and 61% for pumice; and 99%, 82% and 85% for CFS. BOD was stable in the biochar filter material with effluent concentrations of 2 mg/l across all investigated loading rates. However, higher loading rates had a significantly negative effect on hemp and pumice for BOD. Interestingly, the highest loading rate (18 l/d) flowing over pumice removed the highest levels of TN (80%) and TP (86%). Biochar was the most effective material in removing indicator bacteria, with a 2.2–4.0 Log10 reduction for E. coli and enterococci. SCG was the least efficient material, giving a higher BOD in the effluent than in the influent. Therefore, this study presents the potential of natural and waste-derived filter materials to treat greywater effectively and the results can contribute to the future development of nature-based greywater treatment and management practices in urban areas.

Enrichment and chemical fractionation of plant nutrients, potentially toxic and economically valuable elements in digestate from mesophilic and thermophilic fermentation

This study investigated the effect of mesophilic (37 °C) and thermophilic (55 °C) digestion on the enrichment and fractionation of plant nutrients (P, Mn, Fe), potentially toxic elements (Cd, Cr, Pb, As, Cu, Ni, Co, Zn) and economically valuable elements (Ge, rare earth elements REE). Batch experiment was conducted with the substrates of Phalaris arundinacea and inoculum for 40 days and the latter digestate was collected for further analysis. Digestate from selected reactors was filtered through 0.2 μm syringe filters to separate dissolved elements from the particulate. The solid digestate was extracted with ammonium acetate (pH 7 and pH 5) to determine the extraction of mobile/exchangeable and acid soluble elements, respectively. In fresh digestate, element concentration increased by more than 20–100% especially Ge (94%) and REEs (119%) and pH (6.5–7.9) was significantly higher compared to mesophilic (6.1–7.5). In dried digestate, thermophilic digestion showed increased enrichment of Fe, Co, Cu, Zn, Cr, As, Cd, Pb and especially Ge (193%) and REEs (90%) compared to mesophilic indicating a strong enrichment in thermophilic digestion. Considering both operating conditions 5% of elements were present in the liquid, less than 30% were exchangeable and acid soluble and more than 70% were stabile bound into solids. Thermophilic conditions significantly increased the portion of dissolved and labile-bound elements in the digestate. Reactor temperature offers a promising way to use digestate as a secondary raw material for element recovery in the spirit of phytomining, which contributes to a “cascade use” of digestate in the circular economy.