Nutrient Species Research Articles

Cycling of dissolved organic nutrients and indications for nutrient limitations in contrasting Amazon rainforest ecosystems

In the nutrient-poor soils of the Amazon rainforest, phosphorus (P) emerges as a critical limiting factor for ecosystem productivity. Despite these limitations, the Amazon exhibits remarkable productivity that is maintained by its efficient nutrient recycling mechanisms. Central to this process is the role of organic matter, particularly its dissolved (DOM) fraction, which serves as a crucial nutrient reservoir for both plants and microorganisms. This study delves into the dynamics of nutrient-containing DOM within the soils of two contrasting rainforest ecosystems: clayey terra firme forests, known for their robust nutrient recycling and presumed P-limitation, and sandy white-sand forests, characterized by reduced nutrient recycling capacity and presumed nitrogen (N)-limitation. Utilizing ultra-high resolution mass spectrometry (HR-MS), we analyzed the molecular composition of dissolved organic nutrient species. We evidenced nutrient limitation applying innovative concepts: (1) assessing nutrient depletion in DOM via nutrient-to-carbon ratios, (2) comparing the composition of nutrient-enriched DOM pools across soil depth profiles to infer microbial nutrient processing, and (3) examining the temporal variability of nutrient-containing DOM as an indicator of nutrient uptake and production. Our results corroborate the hypothesis of P-limitation in terra firme forests, with significant processing of N-containing DOM also observed, indicating a synergistic demand for both P and N. Surprisingly, white-sand soils exhibited no signs of N-limitation but instead sulfur (S)-limitation, a novel finding for these ecosystems. This study highlights the diversity of potential nutrient limitations in the central Amazon and the importance of the bioavailable “black box” DOM for tropical nutrient cycles.

Binding between Cu2+/Zn2+ and aged polyethylene and polyethylene terephthalate microplastics in swine wastewaters: Adsorption behavior, and mechanism insights

Microplastics (MPs) have aroused growing environmental concerns due to their biotoxicity and vital roles in accelerating the spread of toxic elements. Illuminating the interactions between MPs and heavy metals (HMs) is crucial for understanding the transport and fate of HM-loaded MPs in specific environmentally relevant scenarios. Herein, the adsorption of copper (Cu2+) and zinc (Zn2+) ions over polyethylene (PE) and polyethylene terephthalate (PET) particulates before and after heat persulfate oxidation (HPO) treatment was comprehensively evaluated in simulated and real swine wastewaters. The effects of intrinsic properties (i.e., degree of weathering, size, type) of MPs and environmental factors (i.e., pH, ionic strength, and co-occurring species) on adsorption were investigated thoroughly. It was observed that HPO treatment expedites the fragmentation of pristine MPs, and renders MPs with a variety of oxygen-rich functional groups, which are likely to act as new active sites for binding both HMs. The adsorption of both HMs is pH- and ionic strength-dependent at a pH of 4–6. Co-occurring species such as humic acid (HA) and tetracycline (TC) appear to enhance the affinity of both aged MPs for Cu2+ and Zn2+ ions via bridging complexation. However, co-occurring nutrient species (e.g., phosphate and ammonia) demonstrate different impacts on the adsorption, improving uptake of Cu2+ by precipitation while lowering affinity for Zn2+ owing to the formation of soluble zinc-ammonia complex. Spectroscopic analysis indicates that the dominant adsorption mechanism mainly involves electrostatic interactions and surface complexation. These findings provided fundamental insights into the interactions between aged MPs and HMs in swine wastewaters and might be extended to other nutrient-rich wastewaters.

Characterizing dissolved inorganic and organic nutrients in the oligotrophic Kuroshio Current off eastern Taiwan during warm seasons

This study conducted sensitive and precise analyses of dissolved organic nitrogen (DON) and dissolved organic phosphorus (DOP) concentrations and trace concentrations of nitrate and nitrite (N+N) and soluble reactive phosphorus (SRP) in seawater. The methods were applied to investigate the distributions and controls of N+N, SRP, DON, and DOP in the oligotrophic Kuroshio Current (KC) area off eastern Taiwan during warm seasons. The water in the studied area was classified into four major types: typical Kuroshio water (KW), KW influenced by the East China Sea water, KC influenced by the South China Sea (SCS) water, and KW influenced by the SCS water and river plumes, which is confined to the coastal zone. Nutrient distributions in KC revealed very low N+N (0.002−0.40 μM) and SRP (0.015−0.125 μM) concentrations but high DON (<8 μM) and DOP (<0.3 μM) concentrations above the nutricline depth, which accounted for >80% of TDN and TDP, respectively; theses concentrations can primarily be attributed to strong, permanent surface stratification. Among the water types, KW had the lowest N+N, SRP, DON, and DOP concentrations but greatest chlorophyll maximum depth and nutricline depth, except for in locations influenced by island-induced upwelling. The concentrations of all nutrients increased by various degrees in the other water types, which was attributed to the exchange and mixing of different water masses and coastal uplift of subsurface waters. KW was not only highly oligotrophic but also N+N-limited reflected from very low [N+N]/[SRP] ratio (0.02−0.15) in the mixed layer (ML). Overall, the N+N limitation and high nitrate anomaly value (N*: 2.47 ± 0.16 μM) above the nutricline depth strongly indicate prevailing N2 fixation at the surface of KW. Very high DON/DOP ratio in KW (16.9−69.1) probably resulted from the release of N-rich organic nutrients from phytoplankton including N2 fixers at the surface and faster recycling of DOP than DON in deep waters. Persistent coastal uplift of subsurface water occurs everywhere over the shore-side region of the KC, resulting in increasing surface concentrations of nutrients and chlorophyll a. Overall, the aforementioned physical and biogeochemical processes determined the upper-ocean distributions of nutrient species in warm seasons.

Global structure of competing model with flocculation in a reaction–diffusion chemostat

In this paper, we study a system of reaction–diffusion equations arising from the competition of two competing species for a single limited nutrient with flocculation in an unstirred chemostat. By the conservation principle, we reduce the dimension of the system by eliminating the equation for the nutrient. Then the global structure of the reduced system is studied by the bifurcation theory in its feasible domain. Finally, we use numerical simulation to verify and supplement our theoretical results.

Comparative nutrient drawdown capacities of farmed kelps and implications of metabolic strategy and nutrient source.

Seaweed aquaculture, particularly kelp farming, is a popular topic as a potential solution for mitigating anthropogenic pollutants and enhancing coastal drawdown of carbon and nitrogen. Using a common garden approach, this study evaluated nutrient drawdown capacities of Alaria marginata (ribbon kelp) and Saccharina latissima (sugar kelp) across four commercial kelp farms in Southeast and Southcentral Alaska. Our findings show that A. marginata exhibited ~30% more carbon and 21% more nitrogen content compared to S. latissima. These results demonstrate the potential for A. marginata to serve as a more efficient species for nutrient drawdown into farmed kelp tissues (per unit biomass) for consideration of potential mitigative actions. The efficacy of this drawdown is likely to be driven by the careful pairing of kelp species with farming environment. Temporally, there was a noted increase in carbon content and a decline in nitrogen content from March to May for both species, consistent with known seasonal nutrient dynamics in coastal waters. Notably, differences in the carbon stable isotope signatures (δ13C) between the kelps may hint at variations in metabolic pathways and nutrient sourcing, particularly concerning the preferential assimilation of CO2 versus , and highlight the need for further work on this topic for applied macroalgal research.

The influence of the probiotic “Bioseven” on indicators of survival and growth of calves in the early postnatal period

Dairy cattle breeding is one of the promising areas of agriculture. With a systematic approach and modern technologies, it is a highly profitable agrarian business that is dynamically developing. According to experts, the competitiveness and profitability of the industry can be increased due to the use of natural feed additives and preparations to obtain ecologically safe products for humans. Among them, preparations of microbiological origin are increasingly used, in particular, probiotics, which contain living microorganisms useful for the macroorganism. These drugs are used for prophylactic or therapeutic purposes. It is known that most microorganisms inhabiting the intestines are safe and do not cause diseases, but there is a constant competition between bacteria of different species for space and nutrients. The inconsistency of the microclimate parameters in the calf pens had a direct negative effect on the calf's body, especially in the early postnatal period. In particular, the deviation from the temperature balance, increased air humidity, and the presence of drafts caused a violation of the heat exchange processes of the calves' body with hypothermia and overheating of the body, and, as a result, provoked the frequent occurrence of respiratory diseases. In addition, increased air humidity and high microbial pollution caused the emergence of diseases with functional disorders in the digestive tract due to an imbalance of normal flora and increased activity of the development of transit microbes from the external environment, which negatively affected the homeostasis of the calves' body, weakened the natural resistance of calves, their growth, preservation and often led to the death of animals. Oral use of the probiotic “Bioseven” in a dose of 5.0 g (1.5·109 CFU/cm3) based on 10 kg of live weight ensured the complete preservation of the herd of young calves, accelerated their growth energy, as evidenced by exterior indicators of the animals of the experimental group against the control and probable (P < 0.05) average daily gains in live weight – 1.236 ± 0.37 kg/day versus 1.002 ± 0.41 kg/day in the control group of calves. In further studies, we used a dose of the probiotic “Bioseven” – 5.0 g (1.5·109 CFU/cm3) based on 10 kg of live weight, as the optimal dose of the experimental drug, established by the results of research. Comparative results of studies of growth indicators in the calves of the experimental group showed a significant advantage in the actual probable (Р < 0.01) increase in their live weight during the experimental period, which exceeded the similar indicators of the control by 23.6 %. The results of studies of indicators of average daily live weight gain were significantly (Р < 0.05) higher than those of control calves by 28.5 % (Р < 0.01), which testified to the effectiveness of the use of the probiotic “Bioseven” in young calves. Taking into account the obtained results, it becomes clear that the components of the probiotic drug “Bioseven” have a positive effect on the formation of cicatricial digestion in calves.

Atmospheric deposition of mineral dust and associated nutrients over the Equatorial Indian Ocean

Aerosols are potential supplier of nutrients to the surface water of oceans and can impact biogeochemical processes particularly in the remote locations. The nutrient data from atmospheric supply is poorly reported from the Indian Ocean region. In this study, we present atmospheric nutrients such as reactive nitrogen species (Nitrate, Ammonium, Organic nitrogen), micro-nutrients (e.g. Fe, Mn and Cu) concentration along with mineral dust in the aerosol samples collected over meridional transect during summer (April–May 2018) and monsoon (June–July 2019) months. A significant spatial variation of dust was observed during summer (0.6–22.8 μg m−3) and monsoon (2.8–25.1 μg m−3) months with a decreasing trend from north to south. Dust as well as other nutrient species shows a general north to south decreasing trend, however, no such trend was seen in the soluble trace elements (TEs) concentration. Anthropogenic species like NH4+ and nss-K+ were found below detection limit during monsoon campaign. The fractional solubility (in percentage) of Fe, Mn and Cu were estimated by measuring their concentration in ultrapure water leach which averaged around 0.99 ± 1.12, 31.0 ± 14.9 and 31.1 ± 25.4, respectively during summer and 0.09 ± 0.08, 6.0 ± 8.9, 16.7 ± 9.6, respectively, during monsoon period. Correlation of soluble Fe with total Fe and total acidic species suggest varying dust sources is an important controlling factor for the fraction solubility of Fe with negligible contribution from the chemical processing. However, a significant correlation was observed between total acid and fractional solubility of Mn and Cu suggest role of chemical processing in enhancement of their solubility. Dry deposition flux of aeolian dust was estimated for both campaign using Al concentration and relatively higher fluxes were observed for summer (12.6 ± 8.4 mg·m−2·d−1) and monsoon (8.7 ± 8.4 mg·m−2·d−1) months as compared to model based estimates reported in the literature. Contrastingly, estimated deposition flux of soluble Fe from both campaign displays relatively lower values as compared to model based results which underscores a need for re-evaluation of biogeochemical models with real-time data.

Simulating climate change in a coastal watershed with an integrated suite of airshed, watershed, and estuary models

AbstractIn 2020, the Chesapeake Bay Program moved to offset impacts from climate change for the 30‐year period from 1995 through 2025 by having its seven watershed jurisdictions (Delaware, Maryland, New York, Pennsylvania, Virginia, West Virginia, and the District of Columbia) apply additional nutrient pollutant reduction practices. The climate change assessment was performed with integrated models of the Chesapeake watershed, airshed, and estuary. Scenarios run for the years 2025, 2035, 2045, and 2055 estimated effects from the different future climatic conditions. This article presents the results of that assessment and is intended to provide a guide to assist other modeling practitioners in assessing climate change impacts in coastal watersheds. Major influences of climate change that were quantified include increases in precipitation volume, potential evapotranspiration, watershed nutrient loads, tidal water temperature, and sea level. Minor influences quantified in the climate change analysis include changes in nutrient speciation and increases in wet deposition of nitrogen, CO2, rainfall intensity, tidal wetland loss, up‐estuary salt intrusion, and phytoplankton biomass. To offset climate change impacts from 1995 to 2025 on water quality, the scenarios indicate an additional 2.3 million and 0.3 million kg of nitrogen and phosphorus per annum, respectively, will need to be reduced beyond what is called for in the Chesapeake Total Maximum Daily Load.

Hydrochemical characteristics and water quality assessment of natural water in the South China Mountains: the case in Lianzhou.

South China Mountain Region has a well-developed water system with the most abundant water in China. Untreated natural water is the main source of drinking water for the local people. This study aimed to investigate the hydrochemical characteristics and trace element concentrations of natural water in the mountainous regions of South China. In this study, 116 water samples were collected. Traditional hydrochemical methods, water quality index (WQI), hazard index (HI), and nutrient speciation of trace elements (NSTE) were used for analysis. In general, the hydrochemical type was mainly Ca-HCO3- type. The hydrochemical characteristics were mainly influenced by the weathering of calcite and silicate rocks. Overall total dissolved solids (TDS) were low, indicating mainly soft and very soft water. The water that met the standards for mineral water had an average concentration of 59.69mg/L for Sr (strontium) and an average concentration of 0.46mg/L for H2SiO3 (silicic acid). Although the water quality index (WQI) indicated that 91.3% of the water samples in the study area were of good quality (WQI < 25), 2.58% of the water samples had significant non-carcinogenic risk (HI > 1) due to the high As and Pb concentrations. The water in the study area contributed significantly to human intake of Sr, Cr, and V, accounting for 8.4, 8.3, and 7.7% of the required daily intake for adults, respectively. It is recommended that a comprehensive water quality evaluation system be constructed to ensure that mountain water is managed for development and safe to drink.

Numerical Modeling Unlocks Remarkable Ion Selectivity of Capacitive Deionization

Ion-selective water treatment is an important frontier in water research, as for many applications removing all ions indiscriminately leads to significant extra energy and downstream re-ionization costs. Capacitive deionization (CDI) is under intensive investigations for ion-selective treatment of polluted feedwaters [1]. CDI has the remarkable feature of being not only highly selective, but additionally dynamically tuneable to adjust, real-time, to varying feedwater composition and produced water targets [1]. However, we will show that to further develop CDI technologies to achieve desired separations, in feedwaters of several competing anions and cations, requires detailed numerical models. Such models couple ion transport theory to nanopore electrosorption, and often include pH dynamics. We here describe our recent work exploring the limits of ion-ion selectivity by capacitive deionization with inexpensive nanoporous carbon electrodes. We show how theory enabled us to achieve in the lab remarkable selectivity and a diverse set of separations, such as “perfect” divalent cation selectivity[2], monovalent ion selectivity[3], and removal of amphoteric pollutant species such as boric acid and nutrient species[4]. We show using strong-acid functionalized electrodes that the same two-electrode system can be used for either excellent divalent selectivity, or long-lasting monovalent ion selectivity, depending on cell operational parameters [2,3]. Our work furthers the argument that membraneless CDI, based on inexpensive and easily-scalable porous carbon electrodes, can address a wide variety of important applications in water treatment.

The Amazon shelf sediments, a reactor that fuels intense nitrogen cycling at the seabed

AbstractLarge river plumes such as the Amazon River Plume are known as regions of intense biological, chemical, and physical forcing affecting the delivery and speciation of nutrients. On the shelf, sediments may act as a net source or sink of dissolved inorganic nitrogen (DIN) for the water column depending on the preservation of organic matter (OM) and its remineralization pathways in benthic environments. Previous studies on sediments of the Amazon shelf suggested that the seabed mainly acted as a sink of DIN, with denitrification as the main loss process. However, the Amazon Basin faced drastic changes over the past decades, with climate change, deforestation, and damming potentially impacting the DIN and OM loads to the estuary. These perturbations might have led to changes in benthic remineralization, calling for updates of previously studied benthic remineralization processes on the Amazon shelf. Our analysis of eight short cores confirmed the occurrence of intense recycling of mostly terrestrial material (&gt; 60%) in the river mouth, and little organic carbon was remaining in shelf sediments. We measured a sediment oxygen demand of ~ 23 mmol m−2 d−1, which can explain the ammonification and nitrification of all the organic nitrogen (N) reaching the sediment, underlining the importance of the seabed as a sink for organic N species. Therefore, in spite of the changes in the Amazon Basin, nitrification still seems to be balanced by denitrification, as, similarly to previous results, no DIN diffused out of the sediment.

Sources of major elements and nutrients in the water cycle of an undisturbed river basin – Samothraki Island, Greece

We studied the origin of elements of an undisturbed stream basin during the dry season as derived by atmospheric inputs and lithological processes. Α mass balance model was applied taking into account atmospheric (rain and vapor) inputs and their origin from marine aerosol and dust, as well as the contribution of rock mineral weathering and dissolution of soluble salts. The model results were enhanced using element enrichment factors, element ratios and water stable isotopes. Weathering and dissolution of bedrock and soil minerals contributed the main element portions, besides sodium and sulfate that chiefly derived from wet deposition. Vapor was shown to contribute water to inland waters of the basin. However, rain was the main source of elements compared to vapor, with marine aerosol being the only atmospheric chloride source, contributing also over 60 % of atmospheric sodium and magnesium. Silicate derived from mineral weathering (mainly plagioclase and amorphous silica), while soluble salt dissolution contributed the main portions of the rest of major elements. In headwater springs and streams, element concentrations were more affected by atmospheric inputs and silicate mineral weathering was more intense, contrary to lowland waters that were more affected by soluble salt dissolution. Effective self-purification processes were mirrored in low nutrient levels, despite the significant inputs from wet deposition, with rain being more important contributor than vapor for the majority of nutrient species. Relatively high nitrate concentrations in headwaters were attributed to increased mineralization and nitrification, while the downstream nitrate diminishing was due to prevailing denitrification processes. The ultimate goal of this study is to contribute in establishing stream elements' reference conditions using mass balance modeling approaches.

Research advancements in nutrients and heavy metals, its speciation and behavior during hydrothermal carbonization of sludge – A critical review

Due to rapid increase in urbanization generation rate of sludge is expected to reach over 60 million tonnes hence its proper management has become necessary more than ever. Although, sludge is a complex mixture substance having high moisture content, low energy density and possesses several pollutants but it is also a carbon rich material having potential of resource utilization which attracts many thermochemical techniques to convert it into high value product. Hydrothermal carbonization (HTC) is an efficient pre-treatment technique of converting moisture waste material to high value product with low energy consumption. Phosphorus and nitrogen are major nutrients for agriculture and due to HTC, they can be recovered from hydrochar (HC) as well as process water depending on various conditions. Secondly, the presence of heavy metals is limiting the applicability of sludge-derived HC as soil conditioner and they can be easily transferred to human beings via crops. High ash content in sludge-derived HC is disadvantageous for using it as a fuel. Therefore, this review paper critically discusses transforming mechanism and speciation of nutrients and heavy metals (HMs) for fully utilization of sludge through HTC and how additives (oxides, acids and inorganics) are affecting behavior of nutrients and HMs is systematically discussed. In the end, future perspectives have been discussed for its efficient utilization.

Arsenic in Rice: An Emerging Challenge in Context of Food Security

Arsenic speciation in food and diet was assessed for human exposure through dietary approaches because it seems as a critical public health issue all over the world. Globally, rice is a vital commodity in world hunger and vastly important for survival of human race. Rice is widely used for the formulation of baby formulas, breakfast cereals, bread, cookies, cakes, rice drinks and other foodstuff. Arsenic is concentrated at higher rates in rice grains and containing more than 85% of total arsenic forms that poses serious health aliments o human as well as animal life on the planet. Meanwhile, Arsenic contaminated water and soil may induce hazardous affects to humans through water-soil-plant pathway.

Interspecies relationships between nosocomial pathogens associated to preterm infants and lactic acid bacteria in dual-species biofilms.

The nasogastric enteral feeding tubes (NEFTs) used to feed preterm infants are commonly colonized by bacteria with the ability to form complex biofilms in their inner surfaces. Among them, staphylococci (mainly Staphylococcus epidermidis and Staphylococcus aureus) and some species belonging to the Family Enterobacteriaceae are of special concern since they can cause nosocomial infections in this population. NETF-associated biofilms can also include lactic acid bacteria (LAB), with the ability to compete with pathogenic species for nutrients and space. Ecological interactions among the main colonizers of these devices have not been explored yet; however, such approach could guide future strategies involving the pre-coating of the inner surfaces of NEFTs with well adapted LAB strains in order to reduce the rates of nosocomial infections in neonatal intensive care units (NICUs). In this context, this work implied the formation of dual-species biofilms involving one LAB strain (either Ligilactobacillus salivarius 20SNG2 or Limosilactobacillus reuteri 7SNG3) and one nosocomial strain (either Klebsiella pneumoniae 9SNG3, Serratia marcescens 10SNG3, Staphylococcus aureus 45SNG3 or Staphylococcus epidermidis 46SNG3). The six strains used in this study had been isolated from the inner surface of NEFTs. Changes in adhesion ability of the pathogens were characterized using a culturomic approach. Species interactions and structural changes of the resulting biofilms were analyzed using scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM). No aggregation was observed in dual-species biofilms between any of the two LAB strains and either K. pneumoniae 9SNG3 or S. marcescens 10SNG3. In addition, biofilm thickness and volume were reduced, suggesting that both LAB strains can control the capacity to form biofilms of these enterobacteria. In contrast, a positive ecological relationship was observed in the combination L. reuteri 7SNG3-S. aureus 45SNG3. This relationship was accompanied by a stimulation of S. aureus matrix production when compared with its respective monospecies biofilm. The knowledge provided by this study may guide the selection of potentially probiotic strains that share the same niche with nosocomial pathogens, enabling the establishment of a healthier microbial community inside NEFTs.

Long-term response of an estuarine ecosystem to drastic nutrients changes in the Changjiang River during the last 59 years: A modeling perspective

The riverine nutrient inputs to the ocean reflects land-use changes and can affect the health of coastal environments over time, especially for a highly-anthropogenically influenced river-estuary-shelf system. To investigate the impact of riverine inputs on the Changjiang Estuary ecosystem at a multi-decadal time scale where long-term observations are limited, we built a three-dimensional physics-biogeochemistry-coupled model system based on the Finite-Volume Community Ocean Model (FVCOM) and the European Regional Shelf Ecosystem Model (ERSEM). Our model successfully simulated the temporal and spatial nutrient variabilities in the river-estuary-shelf con7tinuum from 1960 to 2018. The results showed increasing trends of nitrate and phosphate and fluctuating silicate variability, thereby leading to rising nitrogen (N) to phosphorus (P) ratios and decreasing silicon (Si) to N and P ratios. Such changes in the stoichiometric relationship of nutrient species also alter the community structure of the primary producers in estuaries. Our model showed a general increase of diatoms over the 59 years, corresponding to decreased proportions of micro-phytoplankton and pico- phytoplankton. With different backgrounds of light and nutrient limitations in the river and inner shelf, our model suggests that the trend of the diatom proportion in the light-limited river mouth is more associated with silicate variability, with decreased diatom proportions occurring in the 2000s. Our model relates the hydroclimate, nutrient load, and biogeochemical cycling, reproducing estuarine ecosystem variability and clarifying issues such as the causality of the ecosystem interactions.

Numerical Modeling Unlocks Remarkable Ion Selectivity of Capacitive Deionization

Ion-selective water treatment is an important frontier in water research, as for many applications removing all ions indiscriminately leads to significant extra energy and downstream re-ionization costs. Capacitive deionization (CDI) is under intensive investigations for ion-selective treatment of polluted feedwaters [1]. CDI has the remarkable feature of being not only highly selective, but additionally dynamically tuneable to adjust, real-time, to varying feedwater composition and produced water targets [1]. However, we will show that to further develop CDI technologies to achieve desired separations, in feedwaters of several competing anions and cations, requires detailed numerical models. Such models couple ion transport theory to nanopore electrosorption, and often include pH dynamics. We here describe our recent work exploring the limits of ion-ion selectivity by capacitive deionization with inexpensive nanoporous carbon electrodes. We show how theory enabled us to achieve in the lab remarkable selectivity and a diverse set of separations, such as “perfect” divalent cation selectivity[2], monovalent ion selectivity[3], and removal of amphoteric pollutant species such as boric acid and nutrient species[4]. We show using strong-acid functionalized electrodes that the same two-electrode system can be used for either excellent divalent selectivity, or long-lasting monovalent ion selectivity, depending on cell operational parameters [2,3]. Our work furthers the argument that membraneless CDI, based on inexpensive and easily-scalable porous carbon electrodes, can address a wide variety of important applications in water treatment.

Submarine groundwater-derived inorganic and organic nutrients vs. mariculture discharge and river contributions in a typical mariculture bay

• Fresh SGD carries 7.4-80 % of the total SGD nutrients in a typical mariculture bay. • SGD contributes much more nutrients than river and rivals mariculture wastewater. • SGD-derived organic nutrients are dominant but were typically ignored previously. • China-wide upscaling shows significance of SGD in the whole mariculture areas. Submarine groundwater discharge (SGD) is recognized as one of the most significant pathways for terrestrial nutrient entry into coastal systems. However, SGD-derived nutrient fluxes, particularly organic nutrients, have not yet been considered in the management of mariculture areas. We quantified both saline (12.5 cm day −1 ) and fresh (1.8 cm day −1 ) SGD and related nutrient fluxes using the radium quartet and water mass balance model, respectively, and then reassessed nutrient budgets in a typical mariculture bay. Although fresh SGD accounts for 13 % of the total SGD, it carries 7.4–80.5 % of the total SGD nutrients, suggesting that fresh SGD was an important source of new nutrients with high nitrogen to phosphorus (N/P) ratios (585) into the coastal waters. Based on the rebuilt nutrient budgets, total SGD and mariculture discharge were the two major nutrient sources into the coastal water, providing 2.8–21.2 and 1.9–13.9 times more nutrients than local rivers, respectively. The nutrient speciation results revealed that SGD-derived organic nutrients, which are typically ignored, were dominant (i.e., dissolved inorganic nitrogen and dissolved organic phosphorus through SGD contributed about 22.9 % and 41.5 % of all nutrient resources). Furthermore, China-wide upscaling showed that SGD-derived nutrient fluxes in the mariculture area along the coast of China are comparable those of the rivers in China. Therefore, we suggest that SGD-derived inorganic and organic nutrient fluxes should be incorporated into the ecosystem management of mariculture areas.

Origin of dissolved organic carbon under phosphorus-limited coastal-bay conditions revealed by fluorescent dissolved organic matter

To determine the origins of dissolved organic carbon (DOC) in a bay of volcanic Jeju Island, where the discharge of fresh groundwater (FGW) is dominant, we measured fluorescent dissolved organic matter (FDOM) and implemented a parallel factor analysis (PARAFAC). The PARAFAC model identified three humic-like components (FDOMH) and one protein-like component (FDOMP). DOC was extremely deficient in the FGW (35 ± 13 μM) and positively correlated with salinity in the coastal environment, indicating oceanic DOC contribution. The FDOMP pattern was similar to that of DOC, suggesting that marine biological production is a primary DOC source in this region. Particularly, significant FDOMP correlations in the coastal waters with the fluxes of dissolved inorganic phosphorus (DIP; R2 = 0.31) and dissolved silicon (R2 = 0.46) from the FGW demonstrated that in situ biological production is facilitated by FGW-borne nutrient addition. However, the absence of a correlation between the fluxes of dissolved inorganic nitrogen (DIN) and FDOMP (R2 &amp;lt;0.01) indicated that anthropogenic DIN is not essential for DOC production under the P-limited nutrient conditions and diatom-dominant conditions prevailing on the coastal Jeju Island. Here, we calculated the potential capacity of carbon fixation by marine biological activity based on the Redfield ratio of carbon and phosphorus with DIP fluxes. The flux accounts for approximately 2% of the terrestrial carbon uptake in South Korea. Therefore, optical properties of FDOM may be good indicators of coastal DOC origin, and nutrient speciation may be linked to the carbon cycle.

Adapting classical water quality diagrams for ecohydrological and policy applications

Ecological values of water have gained increasing attention over the past decades in both (eco)hydrological research and water resources management. Water quality is an important ecological steering variable, and graphical water quality diagrams may aid in rapid interpretation of the hydrochemical status of a site. Traditionally used water quality diagrams for showing multiple variables (e.g. Stiff, Maucha) were developed primarily for hydrogeological purposes, with limited information on ecologically relevant nutrient parameters.This paper presents adapted classical water quality diagrams that retain the traditional information on ions for hydrogeological characterization, and additionally provide information on nutrients for ecological water quality characterization.A scaling factor is used for the minor ions to visually get them across more equally compared to the macro-ion ions in the water quality diagram. Scaling of minor ions is presented based on average concentrations, as well as on water quality policy norms. Four different water quality diagrams are presented, all with the same ions included, but with different appearances to suit different preferences of individual users. Regional, national and continental scale data are used to illustrate how the different diagrams show spatial and temporal water quality characteristics.The adapted diagrams are innovative with respect to adding comprehensive visual information on the four ecohydrologically relevant nutrient species levels (NO3, NH4, PO4, K), advanced insight in redox status from the combination of four redox sensitive parameters (Fe, NO3, SO4, NH4) and the option to scale minor ions relative to average measured concentrations or to water quality policy norms. Using policy norms for scaling has the advantage of providing an ‘alarm function’ of exceedance of norms when concentrations surpass the ring used in the diagram. We discuss possible standardisation of scaling factors to enable comparability between sites.