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Soil
Published in Stanley E. Manahan, Environmental Chemistry, 2022
Nitrogen fixation is the process by which atmospheric N2 is converted to nitrogen compounds available to plants. Human activities result in the fixation of a great deal more nitrogen than would otherwise be the case. Artificial sources now account for 30%–40% of all nitrogen fixed and probably more in industrialized economies. These include chemical fertilizer manufacture, nitrogen fixed during fuel combustion, combustion of nitrogen-containing fuels, and the increased cultivation of nitrogen-fixing legumes (see the following paragraph). Of some concern with this increased fixation of nitrogen is the possible effect on the atmospheric ozone layer by N2O released during denitrification of fixed nitrogen.
Nitrogen Cycle Bacteria in Agricultural Soils
Published in Vivek Kumar, Rhizomicrobiome Dynamics in Bioremediation, 2021
Guillermo Bravo, Paulina Vega-Celedón, Constanza Macaya, Ingrid-Nicole Vasconez, Michael Seeger
Nitrogen fertilization is a standard practice for improving crop growth and productivity. The nitrogen availability in crops depends on microbial activity. Nitrogen fertilization affects the structure of nitrogen fixing, nitrification and denitrification microorganisms (Fig. 1) (Hai et al. 2009, Morgante et al. 2010, Hernández et al. 2011). Metagenomic studies based on the analysis of the nifH gene show discrepancies in the effects of nitrogen fertilization on nitrogen fixation. Jung et al. (2011) described that nitrogen fixation processes are inhibited with increasing nitrogen availability in soils, affecting the abundance of nitrogen fixing microorganisms. The effects of nitrogen fertilization on nitrogen fixing bacteria is dependent on crop type, pH, temperature, type of fertilization (inorganic or organic) and organic matter (Fig. 1) (Ouyang et al. 2018, Pereg et al. 2018). Hai et al. (2009) reported a decrease in the number of nitrogen-fixing microbes during the application of urea and compost in agricultural soils. Ouyang et al. (2018) indicated that inorganic and organic nitrogen fertilization had no effects on the abundance of the nifH gene using metagenomic analysis on crop. Pereg et al. (2018) showed that organic fertilization strongly increases the nifH gene, whereas fertilizers rich in inorganic ammonia and nitrate showed lower increase of this gene.
Illustrations of Nitrate Pollution of Groundwater
Published in Larry W. Canter, in Groundwater, 2019
Nitrogen fixation by plants was accounted for by considering that: (1) a leguminous crop may fix 23 to 45 kg N per acre and growing season; (2) the area with nitrogen-fixing crops; and (3) the number of crops per year. Based on the relevant data, the nitrogen fixation ranged from about 600 to 1200 kg/km2/year. In addition to nitrogen fixation by plants, there is a nonsymbiotic fixation by bacteria such as Azotobacter and Clostridium. Assuming a rate of 10 to 25 kg/ha/year and applying it to the rest of the cropped area not covered by leguminous species, a flux of 440 to 1100 kg/km2/year was obtained. Therefore, the total nitrogen fixation was considered to range from about 1000 to 2000 kg/km2/year (Jacks and Sharma, 1983).
Green hydrogen production by Rhodobacter sphaeroides
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2023
Dahbia Akroum-Amrouche, Hamza Akroum, Hakim Lounici
The nitrogen source will also greatly influence production efficiency. Moreover, as the nitrogenase equation demonstrates, a surplus of nitrogen in the medium will disadvantage the nitrogen fixation reaction and, therefore, decrease the concomitant hydrogen production. For these reasons, the carbon/nitrogen molar ratio in the growth medium plays a role in defining the photo-fermentative production of hydrogen. According to Eroglu et al (Eroglu et al. 1999), a report of 15 mM (malic acid) for 2 mM (glutamate) in the culture medium would represent the ideal ratio for hydrogen production by photofermentation while Pandey, Srivastava, and Sinha (2012) reported that the bacteria produced the maximum hydrogen potential and hydrogen production rate at a report C/N 13 using glutamate (1.7 mmol m_3) as nitrogen source and malate (3 g m_3) as carbon source.
Effect of complex iron on the phosphorus absorption by two freshwater algae
Published in Environmental Technology, 2021
Yongting Qiu, Zhihong Wang, Feng Liu, Zekun Wu, Hongwei Chen, Daijun Tang, Junxia Liu
Iron is a necessary mineral nutrient for algae proliferation because it plays a very important role in the electron transfer and enzymatic reaction of algae in the physiological, metabolic processes such as nitrogen fixation, photosynthesis, respiration, nucleic acid and protein synthesis [13–16]. However, only a small part of iron in natural water exists in the form of inorganic complexes or free iron ions (Fe3+), and more than 90% of total dissolved iron is organic chelating iron ligands [17]. Because most algae have the ability to absorb complex iron [18], the existence of complex iron will contribute greatly to the proliferation of algae. Nagai et al. [19,20] found that complex iron could effectively inhibit the growth of Microcystis aeruginosa and Fusarium albopictus. Chen and Wang [21] compared the absorption of iron (iron carrier, humic acid, natural high molecular weight compounds) by marine diatoms and cyanobacteria and found that iron absorption by phytoplankton was negatively correlated with the binding ability of organic matter to iron.
Prediction models for evaluating heavy metal uptake by Pisum sativum L. in soil amended with sewage sludge
Published in Journal of Environmental Science and Health, Part A, 2020
Ebrahem M. Eid, Kamal H. Shaltout, Saad A. M. Alamri, Nasser A. Sewelam, Tarek M. Galal, Eid I. Brima
The top three HM concentrations in P. sativum tissues and the soil amended with SS were Fe > Mn > Zn, suggesting ease of uptake of these HMs due to their presence in higher concentrations in the soil and their essential roles in plant growth.[41,43] For example, Fe is capable of acting as an electron carrier in enzyme systems that bring about oxidation-reduction reactions in plants; such reactions are essential steps in photosynthesis and many other metabolic processes. Fe and Mn are components of the enzyme nitrogenase, which is essential for the processes of symbiotic and non-symbiotic nitrogen fixation.[4] Mn and Zn function as bridges to connect enzymes with their substrates, while Mn is essential for certain nitrogen transformations in plants and microorganisms. In addition, Zn plays a role in protein synthesis, the formation of some growth hormones, and the productive process of certain plants. However, Cd, Pb, Mo, Co and Ni tend to accumulate poorly in the tissues of investigated plants, and their uptake occurs mainly in the root system. Similar findings have been reported in many studies, such as Latare et al.,[44] Eid et al.[10] and Ahmed and Slima.[42] Some toxic HMs, such as Cd and Pb, have been recognized by the World Health Organization (WHO) to cause cancer, livestock health problems, and human nerve damage, among other severe health problems.[45] Additionally, both elements were suggested to reduce the total chlorophyll content by inhibiting chlorophyll biosynthetic enzymes.[46]