Decrease In Nitrate Concentration Research Articles

Global ocean primary production trends in the modern ocean color satellite record (1998–2015)

Ocean primary production (PP), representing the uptake of inorganic carbon through photosynthesis, supports marine life and affects carbon exchange with the atmosphere. It is difficult to ascertain its magnitude, variability, and trends due to our inability to measure it directly at large scales. Yet it is paramount for understanding changes in marine health, fisheries, and the global carbon cycle. Using assimilation of ocean color satellite data into an ocean biogeochemical model, we estimate that global net ocean PP has experienced a small but significant decline −0.8 PgC y−1 (−2.1%) decade−1 (P < 0.05) in the 18-year satellite record from 1998 to 2015. This decline is associated with shallowing surface mixed layer depth (−2.4% decade−1) and decreasing nitrate concentrations (−3.2% decade−1). Relative contributions to PP by various types of ocean phytoplankton have changed, with decreases in production by intermediate-sized phytoplankton represented by chlorophytes (−14.3% decade−1). This is partially compensated by increases from the unique, more nutrient-efficient, coccolithophores (8.4% decade−1). Geographically, the North and Equatorial Indian Oceans are responsible for much of the decline in PP, falling 0.16 and 0.69 PgC y−1 decade−1, respectively. Reduced production by large, fast-growing diatoms along with chlorophytes characterizes the decline here. In contrast, increases in PP are found in the North and North Central Pacific. The increases here are led by chlorophytes in the North Pacific and the small cyanobacteria in the North Central Pacific. These results suggest that the multi-decadal satellite observational record, coupled with an underlying representation of marine biodiversity in a model, can monitor the uptake of carbon by phytoplankton and that changes, although small, are occurring in the global oceans.

Use of magnetic fields and nitrate concentration to optimize the growth and lipid yield of Nannochloropsis oculata

Microalgae produce increased lipid content accompanied by a significant decrease in cell density with decreasing nitrate concentration. Magnetic fields (MF) have been reported as a factor that could accelerate metabolism and growth in microalgae culture. Thus, this study aimed to optimize the influence of MF and nitrate concentration (sodium nitrate, N) on the growth and lipid productivity of Nannochloropsis oculata. A single-factor experiment integrated with response surface methodology (RSM) via central composite design (CCD) was performed. The results showed that the maximum specific growth rate (0.24 d−1) and maximum lipid productivity (38 mg L−1 d−1) obtained in this study were higher than those of the control culture (by 166% and 103%, respectively). This study also found that the two-way interaction term MF × N had a significant effect on cell growth but not on lipid production. It was concluded that to design appropriate MF for enhanced lipid productivity due to cell growth, further research must focus on developing an understanding of the relationship between the bioeffects of the magnetic field and the proteomic changes involved in lipid accumulation strategies. This approach would enable the design of conditions to obtain inexpensive high-value products from N. oculata.

Impact of Aeration on the Removal of Organic Matter and Nitrogen Compounds in Constructed Wetlands Treating the Liquid Fraction of Piggery Manure

The increasing demand for sustainable, robust and cost-efficient wastewater treatment techniques strengthen the implementation of constructed wetlands (CWs) in the agricultural sector. In countries like Belgium (Flanders), the compliance of strict water quality standards and surface area requirements have hindered considerably their application. New wetland designs such as aerated CWs, could help to overcome these challenges. This study evaluated the capacity of artificially aerated mesocosm systems to decrease chemical oxygen demand (COD) concentrations below the 125 mgO2/L limit imposed on installations treating animal manure. The treatment of this high-strength wastewater has been slightly studied via aerated CWs. A three-stage experiment investigated the effect of constant, intermittent and non-aeration regimes on: ammonium volatilisation, the evolution of organic and nitrogen compounds concentrations, and denitrification. The results were assessed through a mixed modelling procedure using SAS 9.4 software. A COD removal between 65% and 58% in constantly and intermittent aerated systems, versus 27% COD removal in the non-aerated system indicated the effectiveness of aeration. However, a dissimilarity was encountered in the removal of nitrogen compounds, resulting in an 82% decrease of nitrate concentrations in the non-aerated system, versus 0.5% and 11% in the aerated ones. Based on the results, this experimental set-up adjusted to field operational conditions can prove that aerated CWs can treat the liquid fraction of piggery manure.

EFFECT OF DIFFERENT SOURCES OF ORGANIC FERTILIZERS ON VEGETATIVE GROWTH, YIELD AND STORABILITY OF LETTUCE PLANTS

This investigation was carried out during two winter seasons of 2016/2017 and 2017/2018 at the Agricultural Research Farm, El-Kassasien Hort. Res. Station, Ismalia Governorate, Egypt, to study the effect of different sources of organic fertilizers, i.e. chicken manure, farmyard manure (FYM), compost manure and the mixture of them as compared to mineral fertilizer on vegetative growth, fresh and dry weight per plant, root system, yield and its components of cv. Balady (Local lettuce cultivar) grown under sandy soil conditions.It aimed also to study the effect of the abovementioned treatments on storability of lettuce plants during storage at 0oC and 90-95% RH. Fertilization of lettuce plants with chicken manure at 7.5 m3/fed. or with the mixture of chicken at 2.5 m3plus FYM at 5 m3plus compost manure at 3.7 m3/fed. significantly increased vegetative growth, fresh and dry weight of different organs per plant, root system per plant and water content as well as yield and it's components, while decreased nitrate content without significant differences between them in most cases.Using organic manure the mixture of chicken manure at 2.5 m3plus farmyard manure at 5 m3plus compost manure at 3.7 m3/fed. or chicken manure improve storability of lettuce plants by reducing weight loss and polyphenol oxidase (PPO) activity, maintained chlorophyll and total phenolic contents during storage and gave plants with good appearance after 12 days of storage for chicken manure and after 16 days for mixture treatment.

Nitrate subsurface transport and losses in response to its initial distributions in sloped soils: An experimental and modelling study

AbstractTransport and losses of nitrate from sloped soils are closely linked to nitrogen fertilizer management. Previous studies have always focused on different types of fertilizer applications and rarely analysed various initial nitrate distributions as a result of nitrogen fertilizer applications. Under certain conditions, both subsurface lateral saturated flow and vertical leaching dominate nitrate losses. Soil tank experiments and HYDRUS‐2D modelling were used to better understand the subsurface nitrate transport and losses through lateral saturated flow and vertical leaching under various initial nitrate distributions. Low (L: 180 mg L−1), normal (N: 350 mg L−1), and high (H: 500 mg L−1) nitrate concentrations were used in five different distributions (NNNN, NLLN, LHHL, LNLN, and HNHN) along the slope of the tank. The first two treatments (NNNN and NLLN) were analysed both experimentally and numerically. Experiments were conducted under 12 rainfall events at intervals of 3 days. The HYDRUS‐2D model was calibrated and validated against the experimental data and demonstrated good model performance. The other three treatments (LHHL, LNLN, and HNHN) were investigated using the calibrated model. Nitrate concentrations in purple sloped soils declined exponentially with time under intermittent rainfalls, predominantly in the upper soil layers. Non‐uniform initial nitrate distributions contributed to larger differences between four locations along the slope in deeper soil layers. The non‐uniform nitrate distribution either enhanced or reduced decreases in nitrate concentrations in areas with higher or lower initial nitrate concentrations, respectively. Higher nitrate concentrations at the slope foot and along the slope were reduced mainly by lateral flow and vertical leaching, respectively. Increasing nitrogen application rates increased subsurface nitrate losses. Mean subsurface lateral nitrate fluxes were twice as large as mean vertical leaching nitrate fluxes. However, due to longer leaching durations, total nitrate losses due to vertical leaching were comparable with those due to lateral flow, which indicated comparable environmental risks to surface waters and groundwater.

Evaluating the potential use of a dairy industry residue to induce denitrification in polluted water bodies: A flow-through experiment

Improving the effectiveness and economics of strategies to remediate groundwater nitrate pollution is a matter of concern. In this context, the addition of whey into aquifers could provide a feasible solution to attenuate nitrate contamination by inducing heterotrophic denitrification, while recycling an industry residue. Before its application, the efficacy of the treatment must be studied at laboratory-scale to optimize the application strategy in order to avoid the generation of harmful intermediate compounds. To do this, a flow-through denitrification experiment using whey as organic C source was performed, and different C/N ratios and injection periodicities were tested. The collected samples were analyzed to determine the chemical and isotopic composition of N and C compounds. The results proved that whey could promote denitrification. Nitrate was completely removed when using either a 3.0 or 2.0 C/N ratio. However, daily injection with C/N ratios from 1.25 to 1.5 seemed advantageous, since this strategy decreased nitrate concentration to values below the threshold for water consumption while avoiding nitrite accumulation and whey release with the outflow. The isotopic results confirmed that nitrate attenuation was due to denitrification and that the production of DIC was related to bacterial whey oxidation. Furthermore, the isotopic data suggested that when denitrification was not complete, the outflow could present a mix of denitrified and nondenitrified water. The calculated isotopic fractionation values (ε15NNO3/N2 and ε18ONO3/N2) might be applied in the future to quantify the efficiency of the bioremediation treatments by whey application at field-scale.

Nitrogen transformation of stable ammonium fertilizer in black soil and cinnamon soil

A chamber culture experiment was conducted to measure soil nitrogen transformation following application of stabilized ammonium fertilizers in black soil and cinnamon soil. There were three application levels (0.20, 0.50, 1.00 g N·kg-1 dry soil, respectively) of nitrogen fertilizer. The results showed that nitrification gradually delayed with the increased amount of ammonium application in the cinnamon soil. The treatment of 1.00 g N·kg-1 significantly inhibited nitrification. Nitrification in the cinnamon soil occurred at day 3 and day 7 with 0.20, 0.50 g N·kg-1 dry soil respectively. In the black soil, nitrification occurred at day 3 in all treatments, with nitrification potential decreasing with the increases of ammonium application amount. Nitrification maintained three weeks and two weeks under treatment of 0.20 g N·kg-1 dry soil in cinnamon soil and in black soil, and maintained four weeks and three weeks under treatment of 0.50 g N·kg-1 dry soil. The application with nitrification inhibitors 3,4-dimethylpyrazole phosphate (DMPP) of 1.0% of total nitrogen and dicyandiamide (DCD) of 4.0% of total nitrogen significantly inhibited nitrification, decreased nitrate concentration and nitrification potential. Our results suggested that nitrification would be inhibited as increased ammonium amount in cinnamon and higher than in black soil. In addition, nitrification was significantly inhibited under the ammonium addition rate of 0.20, 0.50 g N·kg-1 dry soil with nitrification inhibitor. Therefore, for the nitrification inhibitor culture experi-ment, it is recommended that the amount of ammonium addition does not exceed 1.00 g N·kg-1 dry soil, and the best concentration is 0.50 g N·kg-1 dry soil.

Reduction of stream nitrate concentrations by land management in contrasted landscapes

Optimizing management practices at the plot scale is sometimes not sufficient to reach water framework directive objectives for nitrate pollution. Land management measures involving targeted setting aside of croplands is a promising solution, but its efficiency depends on the local context. We used a distributed agro-hydrological model to compare management interventions intended to decrease vertical and lateral nitrate leaching from soil to groundwater and stream water in two contrasted agricultural catchments. The simulated scenarios combined two strategies: optimization of agricultural practices and land-use conversion from agricultural to natural land at different locations within the catchments. Long-term climate, discharge, and nitrate concentrations have been monitored for the two catchments and agricultural practices are well known over the 13-year simulation period (2002–2015). The Kervidy-Naizin site (KN) is subject to intense livestock pressure with mean nitrogen inputs of 257 kg ha−1 year−1, while the Aurade site (AU) is primarily cereal cultivation with nitrogen inputs of 109 kg ha−1 year−1. The results highlight a large nitrogen legacy in KN, resulting in a progressive and long lived (> 10 years) response to changes in management, while in AU, this response is perceptible after only 5–7 years. For both catchments, the most effective scenario involves wide riparian buffer strips in interception position covering about 15% of the catchment area. In KN, this land conversion scenario, simulated with the agro-hydrological model TNT2, created a decrease of nitrate concentration in stream water by 25% versus 15% in AU. Contrastingly, the implementation of best management practices decreased stream nitrate concentration only by 9% for KN and 4% for AU.

Bio-cleaning of nitrate salt efflorescence on stone samples using extremophilic bacteria

For the first time, we propose the use of an extremophilic bacterium to remove nitrate salt efflorescence from the surfaces of stone samples. A haloalkaliphilic bacterium was selected “ad hoc” for its ability to reduce nitrates; i.e. Halomonas campaniensis sp. nov., strain 5AGT (DSM 15293T, ATCC BAA-966T). Quantitative monitoring of nitrate content, on untreated and treated surfaces of stone samples artificially enriched with nitrate, as a function of incubation/treatment time, was carried out by molecular spectroscopy. The results obtained reveal the good performance of Halomonas campaniensis bacterium in decreasing nitrate concentration on stone surfaces both in a controlled laboratory environment for temperature and relative humidity and in a real outdoor environmental conditions.

Effectiveness of Organic Fertigation and Moringa Leaf Extract Spray as an Alternative to Chemical Fertigation for Improving Yield and Quality of Lettuce under Soilless Condition

TWO experiments were conducted at Sakha Agricultural Research Station, Bacteriology Lab greenhouse for studying the effect of fertigation with fish extract organic solution as an alternative to mineral nutrient solution as well as foliar spray with moringa leaf extract on morphological, chemical, microbial characteristics and yield of lettuce plant grown under soilless system during winter seasons of 2014 and 2015. In general, the results indicated that fertigation with the fish extract organic nutrient solution increase all the studied characteristics compared to fertigation with the mineral nutrient solution, except for NO3 content which sharply decreased due to organic nutrition treatment which attained 157.52 and 175.24 (mg plant-1) compared to 497.14 and 476.8 (mg plant-1) for mineral nutrition treatment at 2014 and 2015 seasons, respectively. Similarly, foliar spray with moringa extract with mineral nutrition decreased nitrate content (463.46 and 450.16 mg plant-1) lower than mineral nutrition without spray (497.14 and 476.8 mg plant-1) at 2014 and 2015 seasons, respectively. Therefore, positive results on vegetative growth, chemical characteristics and yield of lettuce plant grown under soilless system by using of fertigation with fish extract organic solution and foliar spray with moringa leaf extract to decrease the nutritive gap and vegetables nitrate pollution problems as well as partially avoid the problem of irrigation water shortage.

Effect Of Sodium Nitro-Prusside( Snp) Pretreatment on Ammonia Assimilating Enzymes of Salt Stressed Tomato Leaves (Lycopersicon esculentum)

THE EFFECTS of treatment with 100mM NaCl on photosynthetic activity, protein and proline contents , activities of key nitrogen metabolism enzymes, nitrate reductase (NR) and nitrite reductase (NiR), ammonia assimilating enzymes: Glutamine synthetase (GS), glutamate synthase (GOGAT) and glutamate dehydrogenase (NADH-GDH) activities and finally ammonia and nitrate contents were investigated in 40-day old leaves of tomato plants. There was a decline in total protein (TP) and insoluble protein (InsP) fractions accompanied with a significant increase in proline and soluble protein contents in response to NaCl – stress. Under salinized conditions, there was a significant inhibition in all tested leaf gas exchange parameters, stomatal conductance (gs), internal CO2 concentration (Ci) and hence, CO2 assimilation (A). Also, a significant inhibition of NR & NiR enzymes and a strongly decrease in nitrate content were observed. In contrast, ammonia assimilating enzymes (GS, GOGAT, NADH-GDH and NAD-GDH) activities were obviously increased in NaCl – salinized tomato leaves, this accompanied with a significant increase in ammonia content. Soaking tomato seeds in 10μM sodium nitroprusside (SNP) for 8h were elevated-to some extent- all the studied parameters and there was an improvement in TP, proline, all gas exchange parameters, NR & NiR activities and nitrate content. While ammonia assimilating enzymes (GS, GOGAT, NADH-GDH and NAD-GDH) activities and ammonia content were significantly decreased compared to NaCl - salinized tomato leaves.

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.

Quantitative Nutrient Management Reduces Nitrate Accumulation in Hydroponic Butterhead Lettuces Grown under Artificial Lighting

To reduce nitrate concentrations in vegetables grown under artificial lighting, we determined nitrate accumulation under various conditions of nitrate availability. Butterhead lettuce plants were grown with nutrient solutions of various concentrations, which were maintained according to electrical conductivity (EC) throughout the cultivation period. Under these conditions, growth in nutrient solutions with lower EC led to slight decreases in nitrate concentrations in leaves, but also decreased fresh and dry weights of shoots, leading to the risk of a yield loss under EC control management (ECM). By contrast, when total nitrate requirement was supplied only at the start of cultivation, nitrate concentrations in leaves were decreased significantly with only slightly reduced plant growth. Hence, marketable-sized butterhead lettuces with lower nitrate concentrations can be produced by supplying total nitrate requirements in the nutrient solution at the start of cultivation.

Spatial and temporal trends of nitrate, chloride, and bromide concentration in an alluvial aquifer, North‐Central Texas, USA

AbstractThe Seymour aquifer consists of unconfined outcrops of sand and gravel in a semiarid, agricultural region of north‐central Texas in the United States of America. Most water samples collected from the aquifer in 2015 had nitrate concentrations above the drinking water standard of 44.3 milligrams per liter (mg/L). Generally, areas with high nitrate concentration in 2010 remained high in 2015, although the median dropped by 3.9 mg/L. The largest decreases in nitrate concentration—up to 97 mg/L (60%)—were observed in wells with depths less than the median of 13.1 meters (m). However, other wells, including depths above and below the median, showed increases in nitrate concentration of up to 40 mg/L (42%). In 2015, chloride concentrations in six wells exceeded the secondary contaminant level of 250 mg/L, and one well had a chloride concentration of 1,810 mg/L. Past and ongoing agricultural practices, including cultivation of native grassland, application of fertilizer, and irrigation with nitrate‐contaminated groundwater, help sustain overall high nitrate concentrations within the aquifer. Local conditions governing nitrogen inputs and dilution result in significant improvement or worsening of the nitrate problem over relatively short timeframes. The pumping of groundwater from the aquifer may facilitate mixing with groundwater of increased salinity that has been affected by the dissolution of evaporites in underlying Permian bedrock.

Numerical Simulation and Sensitivity Analysis for Nitrogen Dynamics Under Sewage Water Irrigation with Organic Carbon

This study is focused on investigating the impacts of organic carbon on the denitrification process of nitrogen transformation and transport. A numerical model, Nitrogen-2D, is modified by considering the impact of organic carbon in the denitrification equation. The modified model is used to simulate the soil nitrogen (including nitrate and ammonium) dynamics under the primary and secondary sewage water irrigation with different organic carbon concentrations. The simulated results of accumulated drainage water amount, soil nitrogen concentration, and nitrogen concentration in the drainage water show that the simulations and measurements are consistent. The comparison of results from the original and improved models shows the necessity to consider the impact of organic carbon. The nitrogen mass balance is calculated to analyze the nitrogen transformation processes quantitatively under different input organic carbon sources. Furthermore, the effect of different input organic carbon sources on the soil nitrogen dynamics is investigated by using the modified Nitrogen-2D model with the calibrated parameters. The input organic carbon source helps to speed up the mineralization and denitrification, which contributes to the slight increase of ammonium concentration and the decrease of nitrate concentration in the shallow soil. Since a large number of soil water and nitrogen transformation and transport parameters are needed when setting up the model, a local sensitivity method is conducted to evaluate the input parameters by the sewage water irrigation case. The results show that the drainage water amount is very sensitive to the exponent n and the coefficient α of the soil water retention function and that the ammonium concentration is very sensitive to the first-order nitrification rate constant, the decomposition rate coefficient in humus pool, and the soil ammonium adsorption coefficient. The nitrate concentration is sensitive to more parameters, especially to the exponent n and the coefficient α in the soil water retention function and to the denitrification rate constant.

Impact of Light Intensity and Nitrogen of Nutrient Solution on Nitrate Content in Three Lettuce Cultivars Prior to Harvest

Nitrate smoothly accumulates in leafy vegetables and poses serious health hazards if connected excessively in the human diet. The objective of this study was to improve the cultivation method of low nitrate lettuce grown in plant factory. A substantial decrease of nitrate content (NO3-) in three lettuce cultivars were subjected by short-term pre-harvest treatment combined with lowing nitrogen supply of nutrient solution to half concentration and high photosynthetic photon flux density (PPFD) by LED lighting. The lettuce (Lactuca sativa L. cv. Frill ice, Lvzhu, Ziwei) were hydroponically grown in full strength of nutrient solution based on Yamasaki formula up to harvest time within a controlled environment under two light sources using fluorescent lamps and LEDs. The results demonstrated that a subsequent 3-days treatment of additional PPFD from 250 µmol m-2 s-1 to 350 µmol m-2 s-1 from 18 days after transplanting and half concentrations of nitrogen (NO3--N) in nutrient solution which is composition to standard resulted in the decrease of nitrate content as compared to plants grown under initial PPFD and full concentration of NO3--Ncomposition. The gradual decrease in nitrate content was accompanied by an increased concentration of nutritionally carbohydrates. Another important indicator of nutritional quality such as vitamin C content exhibited some variation, fresh weight of cultivars in cv. Frill ice and Ziwei observed higher with fluorescent lamps and for cv. Lvzhu with LED treatment section followed by lowest nitrate content of fresh leaves, respectively. Further, presented results disclosed that to avoid high accumulation of nitrate in leafy vegetables, the strategy of lowering nitrogen supply and increasing light intensity prior to harvest benefiting growers and consumers by improving quality of the product also making it consumer friendly.

Application of Compost and Vermicompost as Substitutes for Mineral Fertilizers to Produce Green Beans

SUSTAINABLE agricultural development need to provide alternatives of mineral fertilizers to produce safe food for humans, maintain of soil fertility and preserve of environment from pollution. Field experiment was conducted at the site of Vegetable Research Departments, Horticulture Research Institutein Giza Governorate, Egypt, to study possibility of using compost and vermicompost (compost of earthworm) as substitutes partial or fully for mineral fertilizers used in the production of green beans. The beanseeds (cv. Paulista) were sown in clay soil duringthe summer season of 2016 and 2017. Treatments of compost and vermicompost individually orin combination with or without adding 50% of recommended dose of mineral fertilizers,were investigated on bean plants. The effects of these treatments on the growth and yield of green beans were compared tofull recommendeddose of mineral fertilizers as control. All treatments of compost and vermicompostwithout mineral fertilizers decreased all the vegetative properties of bean plants. Compost and vermicompost singly or in combination + 50% mineral fertilizers were not showed any significant differences compared to 100% mineral fertilizers. The treatments of 100% mineral fertilizers and 50% mineral fertilizers + vermicompost sole or combined with compost gave the highest early and total yield compared to other treatments.Applyingcompost and vermicompostwith or without mineral fertilizers, decreased nitrate content of bean pods. This study suggested possibilityfor using compost and vermicompost to reduce the amount of mineral fertilizers to produce good yield,healthyand safe of green beans.

Biotechnological Approaches for Intensification of Ammonium Removal During Drinking Water Treatment

Background. Nitrogen-containing substances are the most common components of groundwater of Ukraine. It was detected, that ammonium may impact on the process of water disinfection, the appearance of nitrite in the distribution system and the problem with the taste and smell of water. The presence of high concentrations of nitrites and nitrates in water can cause methemoglobinemia in children that causes cyanosis and asphyxia. So, there is an urgent demand of developing approaches to intensification of ammonia removing from drinking water. Objective. The aim of these studies is to examine the characteristics of biotechnological processes of nitrogen compounds removing from drinking water in its purification with charge BIOFILTER. Methods. The object of the study was underground water from wells located in the Khmelnitsky region. The initial concentration of ammonia in water was 2.16 mg/dm 3 , nitrite – 0.48 mg/dm 3 , nitrate – 4.5 mg/dm 3 . Investigation of removing of nitrogen-containing substances was conducted on a pilot plant, consisting of aerator, closed contact tank and model filters with charge BIOFILTER. Water was saturated with oxygen in water aerator then came to closed contact tank, where the following parameters were gauged: the concentration of dissolved oxygen, ammonia, nitrites and nitrates. The concentration of dissolved oxygen, ammonia, nitrites and nitrates were controlled in the output water. The pilot plant was set up and worked on the well. Results. It is shown that when the concentration of oxygen decreased from 8.0 to 6.4 mg/dm 3 , a sharp decrease in nitrate concentrations from 4.5 to 3.9 mg/dm 3 was observed. A gradual decrease of nitrates concentrations was observed with increasing doses of consumed oxygen. It was suggested that the nitrification process was passing simultaneously with a process of denitrification as evidenced by a sharp decrease in the concentration of nitrates with a decrease in the oxygen dissolved in water. Conclusions. A decrease in dissolved oxygen concentration violates theoretical ratio of nitrate content in water was experimentally confirmed. The actual content of nitrates in the treated water was less than the theoretical, indicating the passage of denitrification process simultaneously with a process of nitrification. The less concentration of dissolved oxygen in the water at the outlet of the filter, the deeper denitrification is held.

Nitrogen Metabolism in Adaptation of Photosynthesis to Water Stress in Rice Grown under Different Nitrogen Levels.

To investigate the role of nitrogen (N) metabolism in the adaptation of photosynthesis to water stress in rice, a hydroponic experiment supplying with low N (0.72 mM), moderate N (2.86 mM), and high N (7.15 mM) followed by 150 g⋅L-1 PEG-6000 induced water stress was conducted in a rainout shelter. Water stress induced stomatal limitation to photosynthesis at low N, but no significant effect was observed at moderate and high N. Non-photochemical quenching was higher at moderate and high N. In contrast, relative excessive energy at PSII level (EXC) was declined with increasing N level. Malondialdehyde and hydrogen peroxide (H2O2) contents were in parallel with EXC. Water stress decreased catalase and ascorbate peroxidase activities at low N, resulting in increased H2O2 content and severer membrane lipid peroxidation; whereas the activities of antioxidative enzymes were increased at high N. In accordance with photosynthetic rate and antioxidative enzymes, water stress decreased the activities of key enzymes involving in N metabolism such as glutamate synthase and glutamate dehydrogenase, and photorespiratory key enzyme glycolate oxidase at low N. Concurrently, water stress increased nitrate content significantly at low N, but decreased nitrate content at moderate and high N. Contrary to nitrate, water stress increased proline content at moderate and high N. Our results suggest that N metabolism appears to be associated with the tolerance of photosynthesis to water stress in rice via affecting CO2 diffusion, antioxidant capacity, and osmotic adjustment.

Environmental controls on the growth, photosynthetic and calcification rates of a Southern Hemisphere strain of the coccolithophore Emiliania huxleyi

AbstractWe conducted a series of diagnostic fitness response experiments on the coccolithophore, Emiliania huxleyi, isolated from the Subtropical Convergence east of New Zealand. Dose response curves (i.e., physiological rate vs. environmental driver) were constructed for growth, photosynthetic, and calcification rates of E. huxleyi relative to each of five environmental drivers (nitrate concentration, phosphate concentration, irradiance, temperature, and pCO2). The relative importance of each environmental driver on E. huxleyi rate processes was then ranked using a semi‐quantitative approach by comparing the percentage change caused by each environmental driver on the measured physiological metrics under the projected conditions for the year 2100, relative to those for the present day, in the Subtropical Convergence. The results reveal that the projected future decrease in nitrate concentration (33%) played the most important role in controlling the growth, photosynthetic and calcification rates of E. huxleyi, whereas raising pCO2 to 75 Pa (750 ppm) decreased the calcification : photosynthesis ratios to the greatest degree. These findings reveal that other environmental drivers may be equally or more influential than CO2 in regulating the physiological responses of E. huxleyi, and provide new diagnostic information to better understand how this ecologically important species will respond to the projected future changes to multiple environmental drivers.