Sum Of Nitrate Research Articles

Distribution and sea-to-air fluxes of nitrous oxide and methane from a seasonally hypoxic coastal zone in the southeastern Arabian Sea

The seasonal variability, pathways, and sea-to-air fluxes of nitrous oxide (N2O) and methane (CH4) in the coastal environment, where coastal upwelling and mudbanks co-exist are presented based on the monthly time-series measurements from November 2021 to December 2022. Upwelling-driven hypoxic water's shoreward propagation and persistence were the major factors controlling the N2O concentrations, while the freshwater influx and sedimentary fluxes modulate CH4 concentrations. The N2O concentrations were high during the southwest monsoon (up to 35 nM; 19 ± 8 nM)), followed by spring inter-monsoon (up to 19 nM; 10 ± 5 nM), and lowest during the northeast monsoon (up to 13 nM; 8 ± 2 nM), whereas the CH4 levels were high during the spring inter-monsoon (8.4 to 65 nM), followed by southwest monsoon (6.8 to 53.1 nM) and relatively lower concentrations during the northeast monsoon (3.3 to 32.6 nM). The positive correlations of excess N2O with Apparent Oxygen Utilisation (AOU) and the sum of nitrate and nitrite (NOx) indicate that nitrification is the primary source of N2O in the mudbank regime. The negative correlation of CH4 concentrations with salinity indicates considerable input of CH4 through freshwater influx. CH4 exhibited a highly significant positive correlation with Chlorophyll-a throughout the study period. Furthermore, it displayed a statistically significant positive correlation with phosphate (PO43−) during the northeast monsoon while a strong negative correlation with PO43− during the spring inter-monsoon, pointing towards the role of aerobic CH4 production pathways in the mudbank regime. N2O and CH4 exhibited a contrasting seasonal pattern of sea-to-air fluxes, characterised by the highest N2O fluxes during the southwest monsoon (hypoxia) (13 ± 10 μM m−2 d−1), followed by spring inter-monsoon (12 ± 16 μM m−2 d−1), and the lowest during the northeast monsoon (0.6 ± 3 μM m−2 d−1). Conversely, the highest sea-to-air fluxes of CH4 were noticed during the spring inter-monsoon (74 ± 56 μM m−2 d−1), followed by the southwest monsoon (45 ± 35 μM m−2 d−1), and the lowest values during the northeast monsoon (19 ± 16 μM m−2d−1). Long-term time-series measurements will be invaluable in understanding the longer-term impacts of climate-driven variability on marine biogeochemical cycles in dynamic nearshore systems.

Intertidal spring dynamics and coastal nutrient loading revealed through geophysics, drone surveys, and in‐situ monitoring

AbstractCoastal eutrophication poses an increasing risk to ecosystem health due to enhanced nutrient loading to the global coastline. Submarine groundwater discharge (SGD) represents a significant pathway for nitrate‐nitrogen (NO3‐N) transport to the coast, but diffusive SGD transport is difficult to monitor directly, given the low flux rates and expansive discharge areas. In contrast, focused SGD from intertidal springs can potentially be sampled and directly gauged, providing unique insight into SGD and associated contaminant transport. Basin Head is a coastal lagoon in Prince Edward Island, Canada that is a federally protected ecosystem. Nitrate‐nitrogen is conveyed from agricultural fields in the contributing watershed to the eutrophic lagoon via intertidal groundwater springs and groundwater‐dominated tributaries. We used several field methods to characterize groundwater discharge, nutrient loading, and in‐channel mixing associated with intertidal springs. The tributaries and intertidal springs were gauged and sampled to estimate a representative summer nitrate load to the lagoon. Our analysis revealed that NO3‐N export to the lagoon through tributaries and springs throughout summer 2023 was on average 401 kg N/month, with the combined spring loading comparable in magnitude to the combined tributary loading. We collected thermal infrared and visual imagery using drone surveys and found spatial overlap between cold‐water plumes from the spring discharge and macroalgae blooms, indicating the local thermal and ecosystem impacts of the focused SGD. We also mapped the electrical resistivity (salinity) distribution in the water column around one large spring with electromagnetic geophysics at different tidal stages to reveal the three‐dimensional spring plume dynamics. Results showed that the fresher spring water floated above the saline lagoon water with the brackish plume oriented in the direction of the tidal current. Collectively, our multi‐pronged field investigations help elucidate the hydrologic, thermal, and nutrient dynamics of intertidal springs and the cascading ecosystem impacts.

Effects of broiler litter age and application rate on nutrient mineralization under laboratory condition

AbstractBroiler litter (BL), a byproduct of the broiler (Gallus gallus sp.) production cycle, can be regarded as a beneficial organic source to supply essential nutrients for crop growth. Understanding BL nutrient mineralization helps producers better manage nutrients on farms. However, the effects of BL age (length of time BL stays in poultry house before it is cleaned out, also known as the clean out frequency of BL) and application rate on the mineralization of BL nutrients are still poorly understood. Therefore, a 150‐day laboratory incubation study investigated the influence of BL age (6, 18, and 30 months) and application rate (5 and 10 Mg ha−1) on nutrient mineralization. The experimental design was a completely randomized design with three replications. Soil samples were collected at day 0, 10, 30, 60, 90, 120, and 150 and analyzed for nitrogen (N) species nitrate, ammonium, total N, and water‐extractable nutrients (water‐extractable phosphorus, potassium [WEK], calcium [WECa], magnesium [WEMg], iron [WEFe], copper [WECu], zinc (WEZn), boron [WEB], and manganese [WEMn]). Results showed that BL nutrient mineralization was affected by BL age or application rate, except WEFe. A greater amount of nitrate‐N was released during the first month, suggesting faster nitrification during the first 30 days after application. Mineral N (sum of nitrate‐ and ammonium‐N) release was more significant with the increasing age of BL and application rate. Greater availability of WEK, WECa, WEMg, and WEB was found in 18‐ and 30‐month BL from 10 Mg ha−1, and lowest in 6‐month BL from 5 Mg ha−1, whereas 6‐month BL with 10 Mg ha−1 has the greatest WECu. Our results suggested that older BL (30 months) with a greater application rate (10 Mg ha−1) had greater nutrient supply potential.

Coarse particulate matter air quality in East Asia: implications for fine particulate nitrate

Abstract. Air quality network data in China and South Korea show very high year-round mass concentrations of coarse particulate matter (PM), as inferred by the difference between PM10 and PM2.5. Coarse PM concentrations in 2015 averaged 52 µg m−3 in the North China Plain (NCP) and 23 µg m−3 in the Seoul Metropolitan Area (SMA), contributing nearly half of PM10. Strong daily correlations between coarse PM and carbon monoxide imply a dominant source from anthropogenic fugitive dust. Coarse PM concentrations in the NCP and the SMA decreased by 21 % from 2015 to 2019 and further dropped abruptly in 2020 due to COVID-19 reductions in construction and vehicle traffic. Anthropogenic coarse PM is generally not included in air quality models but scavenges nitric acid to suppress the formation of fine particulate nitrate, a major contributor to PM2.5 pollution. GEOS-Chem model simulation of surface and aircraft observations from the Korea–United States Air Quality (KORUS-AQ) campaign over the SMA in May–June 2016 shows that consideration of anthropogenic coarse PM largely resolves the previous model overestimate of fine particulate nitrate. The effect is smaller in the NCP which has a larger excess of ammonia. Model sensitivity simulations for 2015–2019 show that decreasing anthropogenic coarse PM directly increases PM2.5 nitrate in summer, offsetting 80 % the effect of nitrogen oxide and ammonia emission controls, while in winter the presence of coarse PM increases the sensitivity of PM2.5 nitrate to ammonia and sulfur dioxide emissions. Decreasing coarse PM helps to explain the lack of decrease in wintertime PM2.5 nitrate observed in the NCP and the SMA over the 2015–2021 period despite decreases in nitrogen oxide and ammonia emissions. Continuing decrease of fugitive dust pollution means that more stringent nitrogen oxide and ammonia emission controls will be required to successfully decrease PM2.5 nitrate.

Estimation of 226Ra and 228Ra Content Using Various Types of Sorbents and Their Distribution in the Surface Layer of the Black Sea

Radium isotopes have traditionally been used as tracers of surface and underground fresh waters in land-ocean interactions. The concentration of these isotopes is most effective on sorbents containing mixed oxides of manganese. During the 116 RV Professor Vodyanitsky cruise (22 April-17 May 2021), a study about the possibility and efficiency of 226Ra and 228Ra recovery from seawater using various types of sorbents was conducted. The influence of seawater flow rate on the sorption of 226Ra and 228Ra isotopes was estimated. It was indicated that the Modix, DMM, PAN-MnO2, and CRM-Sr sorbents show the best sorption efficiency at a flow rate of 4-8 column volumes per minute. Additionally, the distribution of biogenic elements (dissolved inorganic phosphorus (DIP), silicic acid, and the sum of nitrates and nitrites), salinity, and 226Ra and 228Ra isotopes was studied in the surface layer of the Black Sea in April-May 2021. Correlation dependencies between the concentration of long-lived radium isotopes and salinity are defined for various areas of the Black Sea. Two processes control the dependence of radium isotope concentration on salinity: conservative mixing of riverine and marine end members and desorption of long-lived radium isotopes when river particulate matter meets saline seawater. Despite the high long-lived radium isotope concentration in freshwater in comparison with that in seawater, their content near the Caucasus shore is lower mainly because riverine waters meet with a great open seawater body with a low content of these radionuclides, and radium desorption processes take place in an offshore area. The 228Ra/226Ra ratio derived from our data displays freshwater inflow spreading over not only the coastal region, but also the deep-sea region. The lowered concentration of the main biogenic elements corresponds to high-temperature fields because of their intensive uptake by phytoplankton. Therefore, nutrients coupled with long-lived radium isotopes trace the hydrological and biogeochemical peculiarities of the studied region.

Nitrate Regeneration and Loss in the Central Yellow Sea Bottom Water Revealed by Nitrogen Isotopes

The Yellow Sea (YS) is an epicontinental sea framed by the densely populated mainland of China and the Korean peninsula. Human activities over the last decades resulted in heavily increasing discharge of reactive nitrogen into the YS, which created numerous ecological problems. To elucidate the role of central YS in the cycling of reactive nitrogen, specifically the Yellow Sea Cold Water Mass (YSCWM), we determined nutrient concentrations, dual stable isotopes of nitrate (δ15N-NO3- and δ18O-NO3-), and stable isotopes of particulate and sedimentary nitrogen in spring and summer, i.e., in biologically inactive and active periods. The nitrate concentration in spring was higher than that in summer in the northern part of the YSCWM, Nitrate increased in the southern part accompanied by a decrease in δ15N-NO3- and δ18O-NO3-, which are indicative of nitrification that was a significant source of recycled nitrate in the south part of YSCWM. To quantify this regenerated nitrate, we use a mixing model with end members of preformed nitrate in spring and regenerated nitrate in summer, both with their distinct dual isotope values. The results suggest that only 35% nitrate was a residual of nitrate preformed in spring and 65% in summer in the southern branch of YSCWM was regenerated. The northern part of YSCWM has low concentrations of dissolved inorganic nitrogen, mainly because of denitrification in sediments. In contrast, the southern pool of YSCWM is a growing reservoir of regenerated terrestrial reactive nitrogen, the addition of which compensates the removal by co-occurring sediment denitrification. In consequence, the southern branch of YSCWM is facing a higher ecological risk than the northern branch, when excess reactive nitrogen discharge from Changjiang River continues at present levels or even increases.

Dimethylated sulfur compounds in the Peruvian upwelling system

Abstract. Our understanding of the biogeochemical cycling of the climate-relevant trace gas dimethyl sulfide (DMS) in the Peruvian upwelling system is still limited. Here we present oceanic and atmospheric DMS measurements which were made during two shipborne cruises in December 2012 (M91) and October 2015 (SO243) in the Peruvian upwelling region. Dimethylsulfoniopropionate (DMSP) and dimethyl sulfoxide (DMSO) were also measured during M91. DMS concentrations were 1.9 ± 0.9 and 2.5 ± 1.9 nmol L−1 in surface waters in October 2015 and December 2012, respectively. Nutrient availability appeared to be the main driver of the observed variability in the surface DMS distributions in the coastal areas. DMS, DMSP, and DMSO showed maxima in the surface layer, and no elevated concentrations associated with the oxygen minimum zone off Peru were measured. The possible role of DMS, DMSP, and DMSO as radical scavengers (stimulated by nitrogen limitation) is supported by their negative correlations with N:P (sum of nitrate and nitrite : dissolved phosphate) ratios. Large variations in atmospheric DMS mole fractions were measured during M91 (144.6 ± 95.0 ppt) and SO243 (91.4 ± 55.8 ppt); however, the atmospheric mole fractions were generally low, and the sea-to-air flux was primarily driven by seawater DMS. The Peruvian upwelling region was identified as a source of atmospheric DMS in December 2012 and October 2015. However, in comparison to the previous measurements in the adjacent regions, the Peru upwelling was a moderate source of DMS emissions at either time (M91: 5.9 ± 5.3 µmol m−2 d−1; SO243: 3.8 ± 2.7 µmol m−2 d−1).

Porewater exchange drives nutrient cycling and export in a mangrove-salt marsh ecotone

Coastal wetlands regulate nutrient fluxes from the continents to the oceans. Salt marshes are rapidly encroaching into mudflat area in mangrove wetlands, shaping a mangrove-salt marsh ecotone, with unknown implications to coastal biogeochemical cycles. Here, we hypothesized that nitrogen and phosphorus cycling varied in mangrove and salt marsh, having significant implication on coastal waters. We investigated a tidal creek with a marked mangrove-salt marsh gradient in China using high-frequency time-series sampling of dissolved nutrients and observations of porewater exchange rate across the sediment–water interface over a spring-neap tidal cycle. The nitrogen transformation rates and microbiological activities were also investigated to explain the variability in nitrogen concentrations. The mangrove had net groundwater outflow rates of 3.6–4.3 mm d-1 while the salt marsh had net infiltration of surface water with rates of 0.5–2.9 mm d-1. Salt marsh had less capacity for ammonium (NH4-N) production (mineralization and dissimilatory nitrate reduction to ammonium DNRA) than mangrove. Denitrification dominated nitrogen removal reaching 97% and 83% in mangrove and salt marsh, respectively. Microbe distributions were consistent with nitrogen transformations with larger nirS and nrfA abundances for denitrification and DNRA in the mangrove than salt marsh. The mangrove had a net export of NH4-N but a net import of NOx-N (sum of nitrate and nitrite) and dissolved inorganic phosphorus (DIP) during the monitoring period. In contrast, the salt marsh had lower efflux of nutrient than influx leading to a net nutrient import during the monitoring period. Porewater released from the mangrove had a large DIN:DIP mole ratio (706 ± 236) due to high NH4-N concentrations, while NH4-N in the salt marsh were lower than in the mangrove. Overall, this study revealed that mangrove-salt marsh ecotone will push the native mangrove wetlands from being a source towards a sink of NH4-N to coastal waters by decreasing porewater exchange, modifying the nutrients stoichiometry, and ultimately alleviating the potential of N-associated eutrophication in nearby coastal waters.

Phytoplankton community dynamics as a metrics of shrimp healthy farming under intensive cultivation

In this study, the composition and temporal dynamics of phytoplankton communities were tracked in shrimp ponds of two crops with different health status (healthy or diseased) to explore the potential relationship between phytoplankton community dynamics and/or stability and shrimp health status. Differences in phytoplankton community structures and succession patterns between the two crops were detected by non-metric multidimensional scaling and time-lag regression analysis. Although no significant difference was observed in the α-diversity between the two crops, their community dynamics differed. The turnover and mean shifts in species rank abundance and composition changes of phytoplankton community in the second crop were higher than those in the first crop. Moreover, the stability values of the first crop were significantly higher than those of the second crop. Redundancy analysis revealed that total nitrogen and nitrogen to phosphorus ratio (N/P) were correlated with the phytoplankton community composition in the first crop. In the second crop, the phytoplankton community was regulated by water temperature and dissolved oxygen (DO) in addition to nutrients. Based on linear regression, the phytoplankton community dynamic was correlated with the changes of N/P in the first crop. The DO and the sum of nitrate and nitrite (NOx) and orthophosphate (PO4-P) were the major influencing factors of phytoplankton community dynamics in the second crop. In summary, our findings indicate that the phytoplankton community dynamics may affect the shrimp health, and maintaining a stable phytoplankton community will be helpful to the healthy farming of shrimp. This study provides evidence that the phytoplankton community dynamics can serve as the metrics to evaluate the quality of rearing environment in intensive shrimp pond.

Microbiome dynamics in the tissue and mucus of acroporid corals differ in relation to host and environmental parameters.

Corals are associated with diverse microbial assemblages; however, the spatial-temporal dynamics of intra-species microbial interactions are poorly understood. The coral-associated microbial community varies substantially between tissue and mucus microhabitats; however, the factors controlling the occurrence, abundance, and distribution of microbial taxa over time have rarely been explored for different coral compartments simultaneously. Here, we test (1) differentiation in microbiome diversity and composition between coral compartments (surface mucus and tissue) of two Acropora hosts (A. tenuis and A. millepora) common along inshore reefs of the Great Barrier Reef, as well as (2) the potential linkage between shifts in individual coral microbiome families and underlying host and environmental parameters. Amplicon based 16S ribosomal RNA gene sequencing of 136 samples collected over 14 months, revealed significant differences in bacterial richness, diversity and community structure among mucus, tissue and the surrounding seawater. Seawater samples were dominated by members of the Synechococcaceae and Pelagibacteraceae bacterial families. The mucus microbiome of Acropora spp. was dominated by members of Flavobacteriaceae, Synechococcaceae and Rhodobacteraceae and the tissue was dominated by Endozoicimonaceae. Mucus microbiome in both Acropora species was primarily correlated with seawater parameters including levels of chlorophyll a, ammonium, particulate organic carbon and the sum of nitrate and nitrite. In contrast, the correlation of the tissue microbiome to the measured environmental (i.e., seawater parameters) and host health physiological factors differed between host species, suggesting host-specific modulation of the tissue-associated microbiome to intrinsic and extrinsic factors. Furthermore, the correlation between individual coral microbiome members and environmental factors provides novel insights into coral microbiome-by-environment dynamics and hence has potential implications for current reef restoration and management efforts (e.g. microbial monitoring and observatory programs).

Nitrogen and phosphorus ecophysiology of coralline algae

The characteristics of nutrient uptake in macroalgae are generally well known but surprisingly little is known about nutrient uptake in coralline algae despite their ecological importance and extensive depth distribution. This study provides the first information on nitrate, ammonium and phosphate storage and uptake by articulated and crustose coralline algae that are dominant features of temperate subtidal rocky reefs. A comparison was made between an articulated coralline alga, Arthrocardia sp. in the Corallinales and crustose coralline spp. within the Hapalidiales. Seawater nutrient concentration and nutrient storage by coralline algae were monitored between June 2016 and November 2017 in a kelp forest in southern New Zealand. Time-course nutrient depletion experiments were conducted to determine appropriate incubation times for multiple-flask experiments and evaluate maximal uptake of nitrate, ammonium, and phosphate over time in winter and summer. The uptake of ammonium exhibited a saturable kinetics with Vmax of Arthrocardia sp. (2.07 ± 0.32 μmol gDW−1 h−1) significantly higher than that of crustose coralline spp. (0.58 ± 0.17 μmol gDW−1 h−1). A linear relationship with concentration was observed in nitrate and phosphate uptake by both coralline algae. Ammonium was considered a preferred nitrogen source for these corallines compared with nitrate in both summer and winter. Morphological difference is suggested to be an important factor resulting in the difference in nitrogen and phosphorus uptake rates and kinetic parameters of these corallines. Further research is required to understand if these differences are general attributes of the functional ecology of crustose and articulated corallines.

Seasonal effects of additional HONO sources and the heterogeneous reactions of N2O5 on nitrate in the North China Plain

We coupled the heterogeneous hydrolysis of N2O5 into the newly updated Weather Research and Forecasting model with Chemistry (WRF-Chem) to reveal the relative importance of the hydrolysis of N2O5 and additional nitrous acid (HONO) sources for the formation of nitrate during high PM2.5 events in the North China Plain (NCP) in four seasons. The results showed that additional HONO sources produced the largest nitrate concentrations in winter and negligible nitrates in summer, leading to a 10% enhancement of a PM2.5 peak in southern Beijing and a 15% enhancement in southeastern Hebei in winter. In contrast, the hydrolysis of N2O5 produced high nitrate in summer and low nitrate in winter, with the largest contribution of nearly 20% for a PM2.5 peak in southeastern Hebei in summer. During PM2.5 explosive growth events, the additional HONO sources played a key role in nitrate increases in southern Beijing and southwestern Hebei in winter, whereas the hydrolysis of N2O5 contributed the most to a rapid increase in nitrate in other seasons. HONO photolysis produced more hydroxyl radicals, which were >1.5 μg m−3 h−1 in the early explosive stage and led to a rapid nitrate increase at the southwestern Hebei sites in winter, while the heterogeneous reaction of N2O5 contributed greatly to a significant increase in nitrate in summer. The above results suggest that the additional HONO sources and the heterogeneous hydrolysis of N2O5 contributed the most to nitrate formation in NCP in winter and summer, respectively.

Effect of biodynamic preparations on the soil biological and agrochemical properties and coloured potato tubers quality

AbstractThe aim of this research, which was undertaken in three years (2013-2015), was to evaluate the effect of biodynamic (BD) preparations 500 and 501 on soil biological and agrochemical properties and potato tuber quality. The soil samples were analyzed for: available phosphorus, available potassium, ammonia nitrogen, nitrogen (sum of nitrate and nitrite nitrogen) and mineral nitrogen. The potato samples were analyzed for: total polyphenols content, total anthocyanin’s content and antiradical activity. The research revealed that significantly the highest concentrations of available phosphorus, available potassium, nitrogen and mineral nitrogen in the soil throughout the growing season were identified on the 14th day after soil application of BD preparation 500 (before potato planting). As well as, soil spray application of BD preparation 500 resulted in higher enzyme activity (urease and saccharase). When the BD preparation 501 was applied, the content of total phenolic compounds in the tubers of cultivars Blue Congo and Red Emmalie was significantly higher, 20.1% and 5.4%, respectively; the content of anthocyanins were significantly higher in the tubers of three tested cultivars. However, the application of this preparation did not have any effect on the content of total phenolic compounds and on the antioxidant activity of Vitelotte tubers. The use of both preparations (500+501) had significant effects only on anthocyanins accumulation in the tubers of Blue Congo and Vitelotte. The application of preparation 500 significantly decreased the content of anthocyanins in the tubers of cvs. Red Emmalie and Vitelotte.

Altered Plasma Global Arginine Bioavailability Ratio in Early-stage Alzheimer’s Disease

Background: L-arginine is an amino acid that can be metabolized to form several bioactive molecules including Nitric Oxide (NO). In the Central Nervous System (CNS), NO regulates various and important physiological functions. However, the involvement of L-arginine metabolism –and by extension of NO- in Alzheimer’s disease (AD) pathogenesis, has been suggested. Objective: To determine the Global L-Arginine Bioavailability Ratio (GABR) and NO levels (as the sum of nitrates and nitrites, NOx) in the plasma of early-stage Alzheimer’s Disease (AD) patients in order to analyze if GABR can reflect an altered NO production, to confirm the importance of L-arginine metabolism in the development of the disease, and to evaluate the putative diagnostic/prognostic value of GABR. Method: GABR index is an indicator of the availability of L-arginine to form NO by nitric oxide synthases. It is calculated as the ratio between the levels of L-arginine and the sum of the levels of L-ornithine and L-citrulline. Plasma amino acids are measured by high-performance liquid chromatography coupled to fluorescence detection. Nitric oxide is measured in plasma as the sum of nitrates and nitrites (NOx). Results: No changes were found in L-arginine levels, whereas L-citrulline and L-ornithine levels were highly increased in AD patients. We also found that GABR decreased significantly by 47.8% in AD patients, whereas NOx levels increased significantly by 46.9%. Receiver Operator Characteristic (ROC) curve analysis for GABR showed a sensitivity of 78.1 and a specificity of 90.5. Conclusion: Low plasma GABR levels in AD patients reflect that the L-arginine-NO pathway has turned towards NO in AD, probably being related to the nitroxidative stress involved in neurodegenerative diseases. Furthermore, increased NOx could also be involved in several altered physiological functions. Therefore, GABR is proposed as a putative useful biomarker of the disease.

Introduction of On-site Soil Analysis and Diagnosis System

Crops must absorb all essential elements sufficiently, because a yield of crop is determined by the Minimum which is the growth limiting factor of Liebig's law of minimum. The minimum is determined by soil testing and recommended as a fertilizer corresponding to the amount of crop production for the crop period before cultivation but the amount of the fertilizer is supplied by farmers’ experiences on the growing condition of crop during cultivation. Owing to the diversity of soil chemical properties, soil must be categorized to be recommended the adequate amount of fertilizer. Therefore we categorized soil as 8 soil testing types with soil pH and soil organic matter (SOM) of Korean soil information system. We also set up the on-site soil analysis and diagnosis system in order to recommend the nutrients by soil testing during cultivation. The process of system was composed of three steps: 1) analyzing chemical properties of pH and Eh and nutritional properties of N and P and osmotic properties of EC or sum of nitrate and sulfate and chloride, 2) diagnosing soil condition as one of 64 kinds of soil conditions with categorizing with 4 chemical properties and 8 nutritional status and 2 osmotic aspects, 3) recommending the amount of minimum according to the soil condition and soil testing type and how to supply fertilizers by a series of pH buffer and fertilizer and water. Soil diagnosis chart Nutrient situation Chemical situation 5.6 ≤ pH ≤ 7.4 pH ≤ 5.5 pH ≥ 7.5 Eh7 < 0.48V NP sufficiency NP sufficient Worrying NO2 Worrying NH3 Worrying denitrification NP deficiency NP shortage Volatilizing NO2 Volatilizing NH3 Denitrification P deficiency P shortage N/P imbalance (P precipitated by Al, Fe) N/P imbalance (P precipitated by Ca, Mg) Immature compost N deficiency (good growth) Crop uptake N Volatilizing NO2 Volatilizing NH3 Denitrification N deficiency (bad growth) N shortage Highly volatilizing NO2 Highly volatilizing NH3 Excessive denitrification N excess Excessive N fertilizer Excessive N fertilizer and Immature compost Excessive compost and manure High N immature compost P excess Excessive P fertilizer - - Soluble P fertilizer or excess manure K excess Reverse osmotic pressure - Excessive compost tea Excess immature compost

Regional climate and patterns of phytoplankton annual succession in the open waters of the Black Sea

The annual succession of phytoplankton of the open waters of the Black Sea was investigated on the basis of a database covering the 30-year period from 1985 to 2014. Seasonal variations of the taxonomic composition were analysed with regard to weather conditions and the physical and chemical properties of the environment. Two different patterns of annual phytoplankton succession were revealed for the post-winter period from March to November. After cold winters a classical annual succession of diatoms → dinoflagellates → coccolithophores → dinoflagellates → diatoms was observed, whereas after regular winters another type of succession; dinoflagellates → dinoflagellates → coccolithophores → diatoms → diatoms, took place. These two successions corresponded to seasonal dynamics of nitrate concentration and its share in the total inorganic nitrogen. During cold years these parameters decreased from spring to summer with a subsequent increase in autumn, whereas in regular years they were unusually high in summer. The enigma of this summer nitrate enrichment is well explained by the hypothesis of increasing cross-shelf nutrient transport. During regular years, weak hydrodynamic forcing occurs throughout the year, resulting in a large number of mesoscale eddies along the shelf in summer–autumn that in turn cause the intense transport of coastal waters rich in nitrate to the Sea interior. Development of the large-celled diatom Pseudosolenia calcar-avis in the sea basin observed in summer is in line with this hypothesis. This mechanism was also confirmed by positive relationships between the high sea-surface temperature, and the low Ekman pumping velocity and mean kinetic energy of currents in winter on the one hand, and the contribution of diatoms to the total phytoplankton biomass in summer–autumn, on the other. A case study of mesoscale eddies in the open waters in summer–autumn demonstrated a shift in species composition to large-celled diatoms inside these structures. Climate warming observed during the last 25 years resulted in a decrease in the frequency of cold winters from 30% to 15%, which has led to a decline in the annual phytoplankton standing stock. Thus, in the Black Sea, climate warming affects phytoplankton not directly by an increase in temperature, but by a decrease in the frequency of cold winters.

Modeling impacts of climate and land use change on streamflow, nitrate, and ammonium in the Kor River, southwest of Iran

Abstract This study examined the separate and combined impacts of future changes in climate and land use on streamflow, nitrate and ammonium in the Kor River Basin, southwest of Iran, using the representative concentration pathway 2.6 and 8.5 scenarios of the Fifth Assessment Report (AR5) of the Intergovernmental Panel on Climate Change (IPCC). Different land use and climate change scenarios were used and the streamflow, nitrate and ammonium in the future period (2020–2049) under these scenarios were simulated by Integrated Catchment Model for Nitrogen (INCA–N). Results indicated that climate change will increase streamflows and decrease nitrate and ammonium concentrations in summer and autumn. Land use changes were found to have a little impact on streamflows but a significant impact on water quality, particularly under an urban development scenario. Under combined scenarios, larger seasonal changes in streamflows and mixed changes of nitrate and ammonium concentrations were predicted.

Characteristics of N2O Release and Influencing Factors in Grass-type and Algae-type Zones of Taihu Lake During Summer

Spatial heterogeneity of N2O generation and emissions in multi-ecotype lakes limited the accurate estimation of the N2O fluxes in lakes, but few studies on the characteristics of N2O generation and emissions have been conducted. In this study, N2O flux at the water-gas interface, dissolved N2O concentration in the water column, and N2O flux at the sediment-water interface in typical grass-type and algal-type zones of Taihu Lake were analyzed during summer, and indoor micro-environment experiments were conducted to illustrate the main factors affecting the generation and emissions of N2O. The results showed that the N2O fluxes at the water-gas interface, dissolved N2O concentration, and N2O fluxes at the sediment-water interface of the emergent macrophyte type area was higher than the algae-type area and submerged macrophyte area during the summer., with N2O fluxes at the water-gas interface of (115.807±7.583), (79.768±1.842), and (3.685±0.295) μmol ·(m2 ·h)-1, respectively. The dissolved N2O concentration in the water column were (0.051±0), (0.029±0.001), and (0.018±0) μmol ·L-1, respectively; and the N2O fluxes at the sediment-water interface were (178.275±3.666), (160.685±0.642), and (75.665±1.016) μmol ·(m2 ·h)-1, respectively. The spatial difference could be attributed to dominant plants and the concentration of inorganic nitrogen in the water column. The results of micro-environment experiments showed that nitrate and organic carbon sources could significantly increase the N2O production potential of sediments, the high concentration of NH4+-N in the water column might inhibit the N2O production in sediments, and the production rates of N2O in the sediment increased remarkably when the incubation temperature increased, suggesting that the generation and emissions of N2O were mainly restricted by nitrate, organic carbon, and temperature in summer.

Optimization of strong-base anion exchange O&M costs for hexavalent chromium treatment

Hexavalent chromium [Cr(VI)] in drinking water is pending regulation in California and is being considered for regulation in other locations. While strong-base anion exchange (SBA-IX) can efficiently remove Cr(VI) to low-levels that may be required to comply with future MCLs, operational and maintenance (O&M) costs can be considerable if the spent brine is disposed of as hazardous waste. Through bench- and pilot-scale experiments and full-scale demonstrations, this study examined the ability of emerging and established brine treatment and reuse techniques as well as recently developed resins to decrease O&M costs.When profiling anion elution during regeneration with nanofiltration treated and untreated spent brine, it appeared that at least 1 and 3 reuse cycles were feasible, respectively. Stannous- and ferrous-based reductants were more efficient than sulfur-based reductants when treating spent brine. Bed volumes to 8 μg/L chromium breakthrough with 7 resins varied by as much as a factor of 2 and correlated (R2 = 0.84) with resin total exchange capacities. Spent brine reuse, segmented regeneration (an optimized brine reuse method), ferrous reduction, and nanofiltration of spent brine were estimated to decrease O&M costs by 30, 70, 63, and 61%, respectively. Selection of high performing resins was the most simple way to decrease O&M costs (up to 70% savings).The sum of nitrate and sulfate raw water equivalent concentrations was found to be the principal water quality parameter that influenced the performance of 4 resins in 7 different groundwaters because nitrate and sulfate concentrations were orders of magnitude greater than chromium concentrations. Resins with higher chromium capacities eluted more co-contaminants including arsenic, selenium, uranium, and vanadium because they likely had higher co-contaminant capacities. Co-contaminant elution was found to be complex because associations can form between regenerant and co-eluting anions. Sodium chloride was the most efficient regenerant, though other regenerants provided benefits such as enhanced uranium elution most likely by complexing with uranium to inhibit its precipitation. Nitrate peaking was found to be limited even when reusing untreated and nanofiltration treated spent brine.

Nitrogen deposition in precipitation to a monsoon-affected eutrophic embayment: Fluxes, sources, and processes

Daya Bay in the South China Sea (SCS) has experienced rapid nitrogen pollution and intensified eutrophication in the past decade due to economic development. Here, we estimated the deposition fluxes of nitrogenous species, clarified the contribution of nitrogen from precipitation and measured ions and isotopic composition (δ15N and δ18O) of nitrate in precipitation in one year period to trace its sources and formation processes among different seasons. We found that the deposition fluxes of total dissolved nitrogen (TDN), NO3−, NH4+, NO2−, and dissolved organic nitrogen (DON) to Daya Bay were 132.5, 64.4 17.5, 1.0, 49.6 mmol m−2∙yr−1, respectively. DON was a significant contributor to nitrogen deposition (37% of TDN), and NO3− accounted for 78% of the DIN in precipitation. The nitrogen deposition fluxes were higher in spring and summer, and lower in winter. Nitrogen from precipitation contributed nearly 38% of the total input of nitrogen (point sources input and dry and wet deposition) in Daya Bay. The δ15N-NO3- abundance, ion compositions, and air mass backward trajectories implicated that coal combustion, vehicle exhausts, and dust from mainland China delivered by northeast monsoon were the main sources in winter, while fossil fuel combustion (coal combustion and vehicle exhausts) and dust from PRD and southeast Asia transported by southwest monsoon were the main sources in spring; marine sources, vehicle exhausts and lightning could be the potential sources in summer. δ18O results showed that OH pathway was dominant in the chemical formation process of nitrate in summer, while N2O5+ DMS/HC pathways in winter and spring.