Soil pH affects the processes reducing nitrate to nitrous oxide and di-nitrogen

Song

et al. 2013

Ecological Engineering

a b s t r a c tSalt-affected soils are extensively present and constitute about 7% of total land surface. However, our knowledge about nitrous oxide (N 2 O) production through rapid nitrification and denitrification processes between the atmosphere and the saline soil is very limited. In order to evaluate the potential of N 2 O consumption in saline soils, this study was therefore designed to quantify the variability in N 2 O emissions monthly in the Yellow River Delta in China. Main issues include: different saline-alkaline soils and temporal aspects. Our aim was to quantify N 2 O emissions and identify the major drivers controlling its emissions for providing guidance in eco-restoring coastal wetland on large scale. By using in situ closed chambers the annual average emissions of N 2 O from the mudflat was determined and it was significantly higher than plant communities, especially herbage communities. In general, the emissions of N 2 O of different ecosystems showed a unique-peak annual pattern, with the peak in September. Saline-alkaline mudflat and different vegetations acted as N 2 O source in the Yellow River Delta and the N 2 O emission of different ecosystems followed the order: Saline-alkaline mudflat > T. chinensis >S. salsa > P. australis. Therefore restoration of saline land through revegetation was necessary to reduce the N 2 O emission of saline soils. The effects of air and soil temperature on N 2 O fluxes were significant in salt-affected soils except P. australis. Soil water content and electrical conductivity correlated positively or negatively with N 2 O emissions in mudflat and P. australis community. While relationships between N 2 O production and other soil properties (TC, TN, C:N ratio, NH 4 + -N and NO 3 − -N) were only significant in mudflat and T. chinensis community. Temporal variations of N 2 O emission were related to the interactions of abiotic factors (air and soil temperature, soil water content and electrical conductivity) and the variations of other soil properties, while spatial variations were mainly affected by the vegetation composition at spatial scale.

Section: Discussionmentioning

confidence: 99%

Seasonal dynamics in nitrous oxide emissions under different types of vegetation in saline-alkaline soils of the Yellow River Delta, China and implications for eco-restoring coastal wetland

Song

et al. 2013

Ecological Engineering

“…Soils contain NO 2 ÿ , with the concentration in the soil solution depending on the extent and frequency of nitrogen addition (e.g., fertilization) and the activity of nitrifying and denitrifying bacteria. Nitrite concentrations can be greater than several hundred micromolar (Court et al, 1962;Stevens et al, 1998), though values of 10 to 50 mM are more common in agricultural soils (Binnerup and Sorensen, 1992;Stevens et al, 1998). Nitrite (100 mM) was added to medium in which ABA-treated (A) or GAtreated (B) aleurone layers had been incubated for 24 h or to medium containing added catechin (340 mM).…”

Section: Discussionmentioning

confidence: 99%

Apoplastic Synthesis of Nitric Oxide by Plant Tissues

2004

Nitric oxide (NO) is an important signaling molecule in animals and plants. In mammals, NO is produced from Arg by the enzyme NO synthase. In plants, NO synthesis from Arg using an NO synthase-type enzyme and from nitrite using nitrate reductase has been demonstrated previously. The data presented in this report strongly support the hypothesis that plant tissues also synthesize NO via the nonenzymatic reduction of apoplastic nitrite. As measured by mass spectrometry or an NO-reactive fluorescent probe, Hordeum vulgare (barley) aleurone layers produce NO rapidly when nitrite is added to the medium in which they are incubated. NO production requires an acid apoplast and is accompanied by a loss of nitrite from the medium. Phenolic compounds in the medium can increase the rate of NO production. The possible significance of apoplastic NO production for germinating grain and for plant roots is discussed.

“…In these conversions, NO 2 Ϫ accumulates when its production is kinetically faster than NO 2 Ϫ consumption (9,10). Nitrite accumulation had been thought to occur rarely in the environment (11); however, recent observations suggested that NO 2 Ϫ formation can occur as a result of NO 3 Ϫ reduction and NH 4 ϩ oxidation under conditions that favor NO 2 Ϫ production over consumption (12)(13)(14)(15)(16). For example, high pH and abundance of NH 4 ϩ and hydroxylamine (NH 2 OH) affect NO 2 Ϫ oxidizers, causing NO 2 Ϫ accumulation from nitrosification (15), while oxygen intrusion and/or electron donor limitations may cause NO 2 Ϫ accumulation from denitrification (12).…”

mentioning

confidence: 99%

Nitrite Control over Dissimilatory Nitrate/Nitrite Reduction Pathways in Shewanella loihica Strain PV-4

Yoon

Sanford

Löffler

2015

Appl Environ Microbiol

؊ as a relevant modulator of NO 3 ؊ fate in S. loihica strain PV-4, and, by extension, suggest that NO 2 ؊ is a relevant determinant for N retention (i.e., ammonification) versus N loss and greenhouse gas emission (i.e., denitrification). T wo major dissimilatory pathways determine the fate of nitrate (NO 3Ϫ ) in anoxic environments: denitrification and respiratory ammonification (1, 2). In denitrification, NO 3 Ϫ is stepwise reduced via nitrite (NO 2 Ϫ ), nitric oxide (NO), and nitrous oxide (N 2 O) to dinitrogen (N 2 ). In respiratory ammonification, NO 3 Ϫ is reduced via NO 2 Ϫ to ammonium (NH 4 ϩ ). Nitrite is the common intermediate of the two pathways and the branching point for both dissimilatory pathways. In the presence of NH 4 ϩ , NO 2 Ϫ also can serve as the electron acceptor for anaerobic ammonium oxidation (anammox) (3); however, in soil environments this process appears to be less relevant than the other two processes (4). The fate of NO 2 Ϫ via denitrification or respiratory ammonification has great environmental impact. Denitrification forms gaseous products (N 2 O, N 2 ), which are emitted from the soil, resulting in N loss, whereas respiratory ammonification generates NH 4 ϩ leading to N retention (5, 6). Atmospheric N 2 O is a potent greenhouse gas and an ozone-depleting agent (7,8). Therefore, knowledge of the environmental factors that control these NO 2 Ϫ reduction pathways is needed to estimate, predict, and possibly manipulate N loss versus N retention.The major sources of NO 2 Ϫ in the environment include NH 4 ϩ oxidation performed by nitrosifiers and NO 3 Ϫ reduction. In these conversions, NO 2 Ϫ accumulates when its production is kinetically faster than NO 2 Ϫ consumption (9, 10). Nitrite accumulation had been thought to occur rarely in the environment (11); however, recent observations suggested that NO 2 Ϫ formation can occur as a result of NO 3 Ϫ reduction and NH 4 ϩ oxidation under conditions that favor NO 2 Ϫ production over consumption (12)(13)(14)(15)(16). For example, high pH and abundance of NH 4 ϩ and hydroxylamine (NH 2 OH) affect NO 2 Ϫ oxidizers, causing NO 2 Ϫ accumulation from nitrosification (15), while oxygen intrusion and/or electron donor limitations may cause NO 2 Ϫ accumulation from denitrification (12). In pure-culture studies, several denitrifiers and respiratory ammonifiers were found to reduce NO 3 Ϫ at a higher rate than NO 2 Ϫ , causing dynamic changes of the NO 2 Ϫ :NO 3 Ϫ ratios in the medium (10). Additional NO 2 Ϫ may be generated by NO 3 Ϫ -to-NO 2 Ϫ reducers sensu stricto, which generate NO 2 Ϫ as an end product (12). For example, in activated sludge, the activity of NO 3 Ϫ -to-NO 2 Ϫ reducers leads to NO 2 Ϫ formation; however, the contribution of NO 3 Ϫ -to-NO 2 Ϫ reducers to NO 2 Ϫ accumulation in natural environments is uncertain (17,18).Even though NO 2 Ϫ formation occurs in diverse environments (12,19), information regarding the impact of NO 2 Ϫ on dissimilatory NO 3 Ϫ /NO 2 Ϫ reduction pathways is scarce. Increased NO 2 Ϫ concentrations and respi...