Decrease In NH Research Articles

Enhancing selective NH4+ recovery from wastewater using modified zeolite-based flow electrode capacitive deionization

Despite flow-electrode capacitive deionization (FCDI) is an emerging technology for desalination, contaminant removal, and resource recovery, the application of conventional FCDI in wastewater treatment is hindered by the electrode selectivity and material costs. In this study, we synthesized a low-cost ammonium (NH4+) adsorption electrode material by modifying zeolite using ethylenediaminetetraacetic acid disodium salt (EDTA-2Na). The flow electrode prepared by the mixture of EDTA-zeolite and carbon black exhibits a high selectivity and adsorption capacity for the recovery of NH4+ from wastewater. The NH4+ in wastewater passes through the ion exchange membrane and is rapidly adsorbed by the modified zeolite through ion exchange, while Na+ is retained in the electrolyte. The decrease in NH4+ concentration and the increase in Na+ concentration in the catholyte lead to a significant change in ion concentration gradient across the membrane. Consequently, the transmembrane selectivity between NH4+ and Na+ reached 3.46. We validated the feasibility of NH4+ recovery using FCDI with food waste fermentation supernatant. Under optimal operating conditions, 99.15 % of the NH4+ in the fermentation supernatant was removed, and 95.92 % of the NH4+ in the electrolyte was stored in the EDTA-zeolite. By gravitational settling, the NH4+-rich modified zeolite was separated from carbon black and could be utilized as nitrogen fertilizer. Meanwhile, the mixture of carbon black and brine was used to prepare a fresh electrode suspension. In brief, the FCDI system exhibits a satisfying NH4+ recovery performance and demonstrates a sustainable wastewater resource recovery strategy.

The ameliorative effects of exogenous methyl jasmonate on grapevines under drought stress: Reactive oxygen species, carbon and nitrogen metabolism

Drought stress is recognized as one of the foremost abiotic stresses for worldwide agriculture. Methyl jasmonate (MeJA) is a vital phytohormone that is involved in plant growth, development, and stress adaptation. This study aimed to investigate the influence of exogenous MeJA on carbon and nitrogen metabolism in grapevine leaves under drought stress. Two-year-old grape cuttings (Vitis vinifera L.) were foliar sprayed with either 100 μM MeJA solution or distilled water and then exposed to drought stress. The results showed that exogenous MeJA increased the activities of superoxide dismutase (21 %) and catalase (16 %), resulting in decreased accumulation of reactive oxygen species. Drought stress critically disturbed the processes of photosynthesis, sucrose and starch metabolism, nitrogen assimilation, and amino acid metabolism. MeJA pretreatment improved the photosynthetic capacity and decreased the activities of sucrose synthase (31 %), acid invertase (15 %), and neutral invertase (27 %), thereby improving the accumulation of starch (10 %) and sucrose (90 %). In addition, MeJA pretreatment promoted nitrogen assimilation under drought stress. An increase in activities of nitrate reductase (60 %) and glutamine synthetase (13 %), and a decrease in NH4+ content was observed. Meanwhile, the MeJA application promoted the accumulation of proline and γ-aminobutyric acid, which contributed to the osmotic adjustment and ROS scavenging. In conclusion, exogenous MeJA could promote drought tolerance of grapevines by alleviating oxidative damage and regulating carbon and nitrogen metabolism.

Atmospheric Reactive Nitrogen Deposition from 2010 to 2021 in Lake Taihu and the Effects on Phytoplankton

The effects of nitrogen deposition reduction on nutrient loading in freshwaters have been widely studied, especially in remote regions. However, understanding of the ecological effects is still rather limited. Herein, we re-estimated nitrogen deposition, both of wet and dry deposition, in Lake Taihu with monthly monitoring data from 2010 to 2021. Our results showed that the atmospheric deposition of reactive nitrogen (namely NH4+ and NO3-) in Lake Taihu was 4.94-11.49 kton/yr, which equaled 13.9%-27.3% of the riverine loading. Dry deposition of NH4+ and NO3- contributed 53.1% of the bulk deposition in Lake Taihu. Ammonium was the main component of both wet and dry deposition, which may have been due to the strong agriculture-related activities around Lake Taihu. Nitrogen deposition explained 24.9% of the variation in phytoplankton community succession from 2010 to 2021 and was the highest among all the environmental factors. Atmospheric deposition offset the effects of external nitrogen reduction during the early years and delayed the emergence of nitrogen-fixing cyanobacterial dominance in Lake Taihu. Our results implied that a decrease in nitrogen deposition due to a reduction in fertilizer use, especially a decrease in NH4+ deposition, could limit diatoms and promote non-nitrogen-fixing cyanobacterial dominance, followed by nitrogen-fixing taxa. This result was also applied to other shallow eutrophic lakes around the middle and lower reaches of the Yangtze River, where significant reduction of fertilizer use recorded during the last decades.

Evaluating the impacts of biochemical processes on nitrogen dynamics in a tide gate-controlled river flowing into the South China Sea

This study aimed to evaluate the nitrogen (N) dynamics in Lijiang River, a tide gate-controlled river flowing into South China Sea, and to quantify the biochemical processes affecting nitrate fate and transport during the closed-tide gate period. The continuous on-line water monitoring indicates a chemostatic NH4+-N pattern with respect to variable discharges in the upstream section. The survey via daily grab water sampling from July to December 2020 at four equidistant locations in the lower stretch showed that a gradual increase in NO3−-N and decrease in NH4+-N concentrations occurred along the river from upstream to downstream sections and with the time from September to December (the closed-tide gate period). The mean difference between nitrification and denitrification rate peaked at 0.43 mg L−1 d−1 in October in the upper section and gradually reduced to −0.26 mg L−1 d−1 in December in the middle section, indicating the increased advantage of denitrification over nitrification with time. A gradual increase in the mean NO3−-N assimilatory uptake rate with time and a decrease from upstream to downstream were also observed. These results show that the closed-tide gate promoted N biotransformation in Laingian River and significant N removal was achieved through coupled nitrification-denitrification.

Dissolution Characteristics of Ammonium and Nitrate in Soil with Bottom Ash from Biomass Power Plant

Recently, biomass power plants are increasing as an alternative energy source to reduce the carbon emissions from fossil fuels. The amount of waste from biomass power plants increases and bottom ash is generally buried in soil. However, there is little research on the dissolution characteristics of nitrogen, a macronutrient in soil, using bottom ash (BA). To evaluate nitrogen dissolution in soil with BA, we mixed BA with soil, collected leachate for 5 weeks, and measured NH4+-N and NO3--N concentration in leachate. As a results, BA reduced the leaching of NH4+-N and NO3--N by up to 18% and 38%, respectively. The decrease of NH4+-N leaching is judged to be the result of increased NH4+-N adsorption due to the high pH of the bottom ash, and these results are often confirmed in other biochar. The NO3--N leaching also decreased, but it is not related to the adsorption capacity of BA, so further research is needed. These results suggested that BA reduces the contents of NH4+-N and NO3--N in the soil effluent, which can be used as an important indicator for using bottom ash in the soil.The amount of NH4+-N and NO3--N dissolution in soil using bottom ash from biomass power plant (average and standard deviation; 3 replicate). (left) Accumulation of NH4+-N; (right) Accumulation of NO3--N.

Variations in PM2.5 Composition and Sources During 2020-2021 COVID-19 Epidemic Periods in Nanjing

To understand the changes in chemical composition and sources of PM2.5 under the extreme reduction background during the COVID-19 epidemic periods in Nanjing, hourly observation results of PM2.5 components (water-soluble inorganic ions, carbonaceous components, and inorganic elements) of two epidemic events from January to March 2020 and June to August 2021 were analyzed. In comparison to that during pre-epidemic periods, the concentration of NO3- during the two epidemic control periods decreased by 52.9% and 43.0%, respectively, which was larger than the decreases in NH4+(46.4% and 31.6%) and SO42-(33.8% and 16.5%). Since the observation site was located close to a main road, the decrease in elemental carbon (EC, 35.4% and 20.6%) was higher than that in organic carbon (OC, 11.1% and 16.2%). In reference to the variations in the characteristic ratios of the bulk components mentioned above, the epidemic control showed a more substantial influence on traffic emissions than industrial activities. The concentration time series of PM2.5 major components over the epidemic periods indicated that NOx from local traffic emissions had substantial contributions to the formation of NO3-, which led to local short-term PM2.5 pollution. In addition, the positive matrix factorization (PMF) model was used to analyze the hourly observation data of PM2.5 components. The seven identified factors were linked with metallurgy, firework and firecracker combustions, road traffic emissions, coal combustion, dust resuspension, secondary sulfate, and secondary nitrate. Because the nitrate was unstable under high temperature, the contribution of secondary nitrate to PM2.5 during the epidemic control period of 2021 (summer, 21.2%) was much lower than that during the epidemic control period of 2020 (winter, 60.6%); however, the formation of secondary components always dominated the contribution of PM2.5 sources. Therefore, emissions of NOx and SO2 should be further controlled to continuously reduce ambient PM2.5 concentrations in Chinese cities.

Ecological homogenization of soil properties in the American residential macrosystem

AbstractThe conversion of native ecosystems to residential ecosystems dominated by lawns has been a prevailing land‐use change in the United States over the past 70 years. Similar development patterns and management of residential ecosystems cause many characteristics of residential ecosystems to be more similar to each other across broad continental gradients than that of former native ecosystems. For instance, similar lawn management by irrigation and fertilizer applications has the potential to influence soil carbon (C) and nitrogen (N) pools and processes. We evaluated the mean and variability of total soil C and N stocks, potential net N mineralization and nitrification, soil nitrite (NO2−)/nitrate (NO3−) and ammonium (NH4+) pools, microbial biomass C and N content, microbial respiration, bulk density, soil pH, and moisture content in residential lawns and native ecosystems in six metropolitan areas across a broad climatic gradient in the United States: Baltimore, MD (BAL); Boston, MA (BOS); Los Angeles, CA (LAX); Miami, FL (MIA); Minneapolis–St. Paul, MN (MSP); and Phoenix, AZ (PHX). We observed evidence of higher N cycling in lawn soils, including significant increases in soil NO2−/NO3−, microbial N pools, and potential net nitrification, and significant decreases in NH4+pools. Self‐reported yard fertilizer application in the previous year was linked with increased NO2−/ NO3−content and decreases in total soil N and C content. Self‐reported irrigation in the previous year was associated with decreases in potential net mineralization and potential net nitrification and with increases in bulk density and pH. Residential topsoil had higher total soil C than native topsoil, and microbial biomass C was markedly higher in residential topsoil in the two driest cities (LAX and PHX). Coefficients of variation for most biogeochemical metrics were higher in native soils than in residential soils across all cities, suggesting that residential development homogenizes soil properties and processes at the continental scale.

Evaluation of Heliconia psittacorum in a Horizontal Flow Constructed Wetland (HFCW) System for the Treatment of Textile Wastewater

Constructed wetlands have promised sustainable treatment systems to remediate various industrial wastewaters, including textile. Textile wastewater contains a complex constituent of inorganic and organic pollutants such as dyes, toxic metals, surfactants, nutrients, and total dissolved solids. This preliminary study aims to evaluate the performance of Heliconia psittacorum in a horizontal subsurface flow constructed wetland (HFCW) system for the remediation of textile wastewater. An HFCW system was set in a tank with a volume of 2 m3 divided by three sections where each section filled with coarse gravel, fine gravel, and sand media respectively resulted in a bed volume of 0.322 m3. The top of media was added compost then planted with Heliconia psittacorum. Diluted textile wastewater with a concentration of 20% was fed to the system in a continuous horizontal flow with an HRT of 2.7 days. The performance of the HFCW system showed water quality improvement from the wastewater within 11 weeks of observation. DO increased from < 2 to around 4 mg/L, pH and conductivity increased considerably. High decrease in NH4 and TN concentrations in the effluent of the HFCW system were observed with fluctuated removal efficiency (RE). Maximum RE for ammonia, TN, TSS, and COD was > 80%. Although showing a decreasing pattern during observation, phosphorus was not effectively removed by Heliconia psittacorum in the studied HFCW system. Cleaner effluent was observed than much dirty and black colour of influent. Heliconia psittacorum grew well with increased shoot height and numbers of new plant seedlings. The long-term observation was needed for Heliconia psittacorum in the HFCW system to reach a steady state and to examine its potential to remediate textile wastewater.

Exogenous Hemin alleviates cadmium stress in maize by enhancing sucrose and nitrogen metabolism and regulating endogenous hormones

Cadmium (Cd) stress restricts maize growth and productivity severely. We aimed to investigate the effects of Hemin on the metabolism of sucrose and nitrogen and endogenous hormones in maize under cadmium stress. Maize varieties ‘Tiannong 9’ (cadmium tolerant) and ‘Fenghe 6’ (cadmium sensitive) were grown in nutrient solutions to study the effects of Hemin on maize physiological and ecological mechanisms under cadmium stress. The results showed that Hemin mediated the increase of sucrose content and the activities of key enzymes sucrose phosphate synthase (SPS) and sucrose synthase (SS) in maize leaves under cadmium stress. Soluble acid invertase (SAInv) and basic/neutral invertase (A/N-Inv) enzyme activities in leaves were decreased significantly, and sucrose accumulation in leaves was increased. Hemin also mediated the increase of NO3 − content in leaves, the decrease of NH4 + content and the increase of nitrate reductase (NR), glutamine synthetase (GS), glutamate synthase activity (GOGAT) and glutamate dehydrogenase (GDH) enzyme activities under cadmium stress. The contents of IAA, ZR, and GA in leaves and roots increased, ABA, MeJA, and SA decreased, and IAA/ABA, ZR/ABA, and GA/ABA increased under cadmium stress. Our study showed Hemin can alleviate cadmium stress in maize by enhancing sucrose and nitrogen metabolism and regulating endogenous hormones.

Micro(nano)plastic size and concentration co-differentiate nitrogen transformation, microbiota dynamics, and assembly patterns in constructed wetlands

Micro/nano-sized plastics (MPs/NPs) existing in wastewater system are the potential threats to nitrogen (N) biotransformation. Constructed wetlands (CWs) as wastewater treatment systems are considered the important barriers preventing MPs/NPs from entering the open water. However, little is known about how the accumulation of MPs/NPs affects microbial N transformation, dynamics, assembly, and metabolism of wetland microbiota. Herein, we constructed 12 wetland systems to address the above knowledge gaps over 300-day exposure to different sizes (3 mm - 60 nm) and concentrations (10 - 1000 μg/L) of MPs/NPs. The results showed that MPs/NPs accumulation caused decrease in NH4+-N removal (by 7.6% - 71.2%) and microbial diversity and intriguingly altered microbiota composition (especially in the high-concentration groups) without damage on the high removal efficiency of NO3−-N and NO2−-N (66.2% - 99.8%) in all except for the nano-sized plastic-exposed wetlands. Moreover, MPs/NPs exposure induced shift in the strengths of non-random species aggregation and segregation patterns co-differentiated by the size and concentration of MPs/NPs, and MPs/NPs accumulation created size-differentiated alternative niches for nitrogen-transforming bacteria, e.g., canonical nitrifiers (Nitrospira and Nitrosomonas) and denitrifiers (Thauera, Comamonas, and Aquabacterium), which were enriched in MPs groups where denitrifying enzyme-coding genes were also enriched, suggesting potential positive impact of larger plastics on denitrification. Our study highlights MPs/NPs-induced divergence in microbiota dynamics and nitrogen transformation in CWs, and provides important insights into how microbiota structurally and functionally respond to long-term MPs/NPs disturbance.

Long-term straw return influenced ammonium ion retention at the soil aggregate scale in an Anthrosol with rice-wheat rotations in China

Soil aggregates are an important controlling factor for the physico-chemical and biological processes such as ammonium (NH4+) retention. Straw return to the field is increasingly recommended to promote soil carbon (C) sequestration and improve crop yields. However, the effects of straw return on NH4+ retention at soil aggregate level in agricultural soils have seldom been investigated. This study aimed to evaluate the influences of long-term straw return on NH4+ adsorption and fixation in microaggregates (<0.25 mm) with or without soil organic carbon (SOC) oxidization. Soil samples were collected from plots of three treatments, i.e., no fertilizer (CK), inorganic NPK fertilizers (NPK), and inorganic NPK fertilizers with rice straw return (NPKS), from a 20-year-old field trial with rice-wheat rotations in Taihu Lake Region, China. Soil aggregates were separated using wet-sieving method. The SOC of microaggregates was oxidized by H2O2. The results showed that long-term straw return significantly increased SOC and NH4+ adsorption, but inhibited NH4+ fixation in microaggregates. NH4+ adsorption potential and strength - obtained from adsorption isotherms - increased, but NH4+ fixation decreased along with increasing SOC in microaggregates, indicating the important role of SOC in NH4+ adsorption and fixation. This was verified by the SOC oxidization test that showed a relative decrease in NH4+ adsorption potential for the NPKS treatment and an increase in NH4+ fixation in all three treatments. Therefore, long-term straw return influences NH4+ adsorption and fixation by enhancing SOC content and could improve N availability for crop uptake and minimize applied N fertilizer losses in rice-wheat cropping systems.

ЭФФЕКТИВНЫЕ БИОМАРКЕРЫ В ДИАГНОСТИКЕ ПИЩЕВОЙ АЛЛЕРГИИ НА ЯБЛОКО И ИХ СРАВНИТЕЛЬНАЯ ОЦЕНКА

Objectives. To evaluate the diagnostic efficacy of the prick-test and the levels of tryptase, cations K&lt;sup&gt;+&lt;/sup&gt;, NH&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;+&lt;/sup&gt; and Ca&lt;sup&gt;2+&lt;/sup&gt;, peroxidase activity in the oral fluid (OF) as biomarkers of apple allergy and to comparatively assess them. Material and methods. We examined 35 patients with a history of allergic reactions to a fresh apple (the study group) and 29 healthy persons (the control group). All participants underwent the prick-test with 3 varieties of fresh apples and oral-pharyngeal provocative test (OPPT) with freshly prepared apple juice with the assessment of tryptase, peroxidase activity, K&lt;sup&gt;+&lt;/sup&gt;, NH&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;+&lt;/sup&gt; and Ca&lt;sup&gt;2+&lt;/sup&gt; cations levels in the OF. Results. The prick-test was positive in 94% of patients. In 70% of patients after OPPT, there was a significant tryptase level increase in the OF compared with healthy persons (p=0.000003). After provocation, in the study group, in 74% of cases, a significant peroxidase activity level increase in the OF was revealed in comparison with the control group (p&lt;0.0000001). A significant K&lt;sup&gt;+&lt;/sup&gt; level increase in the oral fluid was found in 81% of patients, in contrast to healthy persons after OPPT (p=0.02). In 67% of cases in the study group, a significant NH&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;+&lt;/sup&gt; level decrease after OPPT was found in comparison with the initial cation level in this group (p=0.039). Patients with a history of apple allergy after provocation showed a higher Ca&lt;sup&gt;2+&lt;/sup&gt; cations level in the OF than the control (p=0.02). Conclusions. Biomarkers of hypersensitivity to apples of the varieties Golden Delicious, Red Prince and Belarusian sweet were revealed: positive prick-test, an increase of tryptase, myeloperoxidase activity, K&lt;sup&gt;+&lt;/sup&gt; cations and a decrease of NH&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;+&lt;/sup&gt; level after OPPT. Biomarkers have a high diagnostic value and can be used both in combination and separately to identify systemic and local hypersensitivity and to diagnose food allergy to apples.

Variations in traffic-related water-soluble inorganic ions in PM2.5 in Kanazawa, Japan, after the implementation of a new vehicle emission regulation

In this study, a three-year sampling campaign was conducted at a roadside air pollution monitoring station in Kanazawa, Japan. A total of 7 water-soluble inorganic ions (WSIIs) in ambient particulate matter (PM2.5) was determined via ion chromatography. After the implementation of a new vehicle emission regulation enacted in 2016 in Japan, the annual average concentration of the total WSIIs decreased, from 5.32 ± 3.27 μg/m3 in 2017 to 3.70 ± 2.43 μg/m3 in 2018. This decrease is mainly attributed to the reduction in the three major species of sulfate (SO42−), ammonium (NH4+), and nitrate (NO3−). The reduction in NO3− with decreasing nitrogen oxide (NOx) emphasizes the role of the new regulation. The reduction in NOx might also indirectly lead to a decrease in SO42− or directly lead to a decrease in NH4+. Through a comparison to other WSIIs emission sources, a similar composition was found to that of other traffic-related WSIIs, but the considered WSIIs are clearly different from those emitted by coal and biomass combustion sources. Via further comparison of the distribution of the [NO3−]/[SO42−] ratio values from different sources, we observed that the ratio values are close to those of WSIIs emitted by coal combustion sources, which indicates that this ratio might not be a suitable indicator for the identification of the contribution of mobile and stationary sources in Japanese cities. Overall, this study affirms the effectiveness of the new regulation in terms of WSIIs emission reduction and provides basic WSIIs data pertaining to the roadside environment in Kanazawa for the first time.

Water Quality Improvement Shifts the Dominant Phytoplankton Group From Cryptophytes to Diatoms in a Coastal Ecosystem

We investigated long-term variations in the dominant phytoplankton groups with improvements in water quality over 11 years in the Yeongil Bay on the southeastern coast of Korea. River discharge declined during the study period but TN from river discharge remained stable, indicating the input of enriched nutrients to the bay was fairly consistent. NH4+ levels decreased with a decrease in TN from the POSCO industrial complex. While the study region was characterized by the P-limited and deficient environment, cryptophytes dominated with the intensified P-limitations. The relative abundance of cryptophytes declined from 70% in 2010 to 10% in 2016, but that of diatoms increased from 70% in 2009 to 90% in 2016. Correlation analysis showed a positive correlation of cryptophytes with NH4+ and a negative correlation with photic depth. Generalized additive models also exhibited an increase in diatom dominance and a decrease in cryptophyte dominance with an increase in water quality, indicating that a decrease in NH4+ and increase in light favored the diatom growth but suppressed the cryptophyte growth. Thus, water quality improvements shift the dominant group in the coastal ecological niche from cryptophytes to diatoms.

Controls on Nutrient Cycling in Estuarine Mangrove Lake Sediments

We estimated the net exchange of nitrogen and phosphorus species using core incubations under light and dark conditions in estuarine lakes that are the aquatic interface between the freshwater Everglades and marine Florida Bay. These lakes and adjacent shallow water Florida Bay environments are sites where the restoration of hydrological flows will likely have the largest impact on salinity. Sediment respiration, measured by oxygen uptake, averaged (±S.D.) −2400 ± 1300, −300 ± 1000, and 1900 ± 1400 μmol m−2 h−1 for dark incubations, light incubations, and gross photosynthesis estimates, respectively, with dark incubations consistent with oxygen uptake measured by microelectrode profiles. Although most fluxes of soluble reactive phosphorus, nitrate, and N2–N were low under both light and dark incubation conditions, we observed a number of very high efflux events of NH4+ during dark incubations. A significant decrease in NH4+flux was observed in the light. The largest differences between light and dark effluxes of NH4+ occurred in lakes during periods of low coverage of the aquatic macrophyte Chara hornemannii Wallman, with NH4+ effluxes &gt; 200 μmol m−2 h−1. Increasing freshwater flow from the Everglades is expected to expand lower salinity environments suitable for Chara, and therefore, diminish the sediment NH4+ effluxes that may fuel algal blooms.

Enhanced electrocatalytic denitrification using non-noble Ni-Fe electrode supplied by Fe3O4 nanoparticle and humic acid

The present study aimed to investigate the effect of Fe3O4 nanoparticles and humic acids (HAs) in electrocatalytic denitrification using a non-noble Ni-Fe cathode. As a non-noble metal electrode, the Ni-Fe was prepared through the electrodeposition method and then characterized by physical and electrochemical analyses. The obtained results show that using Fe3O4 NPs, the nitrate (NO3−) reduction efficiency increased from 42% to 84%. Moreover, the ammonium (NH4+) concentration decreased from 6 mg/l to 3.6 mg/l (91.19% selectivity to N2). The NO3− reduction efficiency reached from 42% to 85.5% using HAs, and the concentration of NH4+ decreased to 1.7 mg/l (95.63% selectivity to N2). The nitrite (NO2−) concentration was negligible. The decrease in NH4+ concentration and increased selectivity to N2 using Fe3O4 nanoparticles has resulted from radical hydroxyl (OH) production. Moreover, in the presence of HAs, the superoxide anion (O2∙-)produced, which played an influential role in the production of OH along with hypochlorous acid (HClO). The results revealed that the Ni-Fe/Fe3O4 electrode in the presence of HAs had an outstanding ability for NO3− reduction with high efficiency, high selectivity to N2, low energy consumption, and low production of dangerous by-products.

One-year monitoring of nitrogen forms after the application of various types of biochar on different soils

Biochar is a carbon rich product obtained from pyrolysis of biomass. The use of biochar as soil amendment has been boosted in the last years due to its possible influence on fertility, including its potential ability to lower mineral nitrogen losses, but specially for its potential to reduce greenhouse gases and to increase carbon sequestration in soil. However, the studies on the effects of biochar on nitrogen forms in soil are heterogeneous and contradictory. The present work aims to clarify this point by applying 6 different biochars (with different origin and production process) on 6 different soils (of different properties). The amendment corresponded to an agronomic addition rate of 30 Mg ha−1, together with the addition of urea at a 100 kg N per ha rate. Then those mixtures were incubated for one year at a 60% of the WHC. The samples were analyzed for nitrogen forms (Kjeldahl-N, ammonium-N, nitrate-N, nitrite-N, and microbial-N) at different incubation times (1 week, 1 month, 4 months and 1 year after the addition). The results showed that the effects of different biochars on the soil nitrogen forms were variegated, mainly attributable to soil properties, and to a lesser extent to the particular biochar used. Overall, the Kjeldahl-N (KN) decreased after the incubation time, and only the mixtures with N-rich biochars achieved slightly higher KN compared to controls. Also, biochars tended to induce a decrease in NH4+-N, and, especially, in NO3–-N. The biochars causing highest shifts on N inorganic forms were those produced from agronomic sources (olive and corn wastes) and the one from pine wood materials subjected to high pyrolysis temperature conditions.

Probiotic infant cereal improves children’s gut microbiota: Insights using the Simulator of Human Intestinal Microbial Ecosystem (SHIME®)

Infant́s gut microbiota can be modulated by many factors, including mode of delivery, feeding regime, maternal diet/weight and probiotic and prebiotic consumption. The gut microbiota in dysbiosis has been associated with innumerous diseases. In this sense, early childhood intestinal microbiome modulation can be a strategy for disease prevention. This study had the purpose to evaluate the effect of an infant cereal with probiotic (Bifidobacterium animalis ssp. lactis BB-12®) on infant́s intestinal microbiota using SHIME®, which simulates human gastrointestinal conditions. The ascending colon was inoculated with fecal microbiota from three children (2–3 years old). NH4+, short chain fatty acids (SCFASs) and microbiota composition were determined by selective ion electrode, GC/MS and 16S sequencing, respectively. After treatment, butyric acid production increased (p < 0.05) 52% and a decrease in NH4+ production was observed (p < 0.01). The treatment stimulated an increase (p < 0.01) of Lactobacillaceae families, more precisely L. gasseri and L. kefiri. L. gasseri has been associated with the prevention of allergic rhinitis in children and L. kefiri in the prevention of obesity. Thus, infant cereal with BB-12® is able to stimulate the growth of L. gasseri and L. kefiri in a beneficial way, reducing NH4+ and increasing the production of SCFAs, especially butyric acid, in SHIME®.

English

The present study investigated the role of inoculation with Nitrobien biofertilizer (N-Bio, Azospirillum and azotobacter spp.) on the response of maize plants to cadmium-toxicity (applied as 2 and 10 mM CdSO4). Cd-stress caused a significant reduction in the fresh and dry biomass of leaves and roots as well as a marked disturbance in the anatomical features of roots and stomatal structure and behavior. Cd-stress significantly depressed the total photosynthetic pigments, photochemical efficiency of PS II, total carbohydrates, and proteins content. Furthermore, increasing Cd level prompted oxidative stress measured in terms of malondialdehyde and H2O2 contents in maize plants. Application of N-Bio improved these attributes in Cd-stressed maize plants. Moreover, NO3- uptake and its assimilating enzymes (nitrate reductase, NR; glutamine synthase, GS; and, glutamate dehydrogenase GDH) were significantly increased in N-Bio-pretreated Cd-stressed plants than Cd- stressed ones and that was associated with a decrease of NH4+ content. N-Bio pretreatment also stimulated the accumulation of amino acids and markedly increased endogenous phytohormone content (IAA, GA3) of Cd-stressed maize plants. These results revealed the potentiating effect of N-Bio pretreatment in regulating Cd-induced damages in maize plants. © 2021 Friends Science Publishers

NH4+-N/NO3−-N ratio controlling nitrogen transformation accompanied with NO2−-N accumulation in the oxic-anoxic transition zone

Although nitrogen (N) transformations have been widely studied under oxic or anoxic condition, few studies have been carried out to analyze the transformation accompanied with NO2−-N accumulation. Particularly, the control of mixed N species in N-transformation remains unclear in an oxic-anoxic transition zone (OATZ), a unique and ubiquitous redox environment. To bridge the gap, in this study, OATZ microcosms were simulated by surface water and sediments of a shallow lake. The N-transformation processes and rates at different NH4+-N/NO3−-N ratios, and NO2−-N accumulations in these processes were evaluated. N-transformation process exhibited a turning point. Simultaneous nitrification and denitrification occurred in its early stage (first 10 days, dissolved oxygen (DO) ≥ 2 mg/L) and then denitrification dominated (after 10 days, DO < 2 mg/L), which were not greatly affected by the NH4+-N/NO3−-N ratio, on the contrary, the transformation rates of NH4+-N and NO3−-N were distinctly affected. The NH4+-N transformation rates were positively correlated with the NH4+-N/NO3−-N ratio. The highest NO3−-N transformation rate was observed at an NH4+-N/NO3−-N ratio of 1:1 with organic carbon/NO3−-N of 3.09. The NO2−-N accumulation, which increased with the decrease in NH4+-N/NO3−-N ratio, was also controlled by organic carbon concentration and type. The peak concentration of NO2−-N accumulation occurred only when the NO3−-N transformation rate was particularly low. Thus, NO2−-N accumulation may be reduced by adjusting the control parameters related to N and organic carbon sources, which enhances the theoretical insights for N-polluted aquatic ecosystem bioremediation.