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Nitrogen isotopes in ice core nitrate linked to anthropogenic atmospheric acidity change.

ABSTRACT: Nitrogen stable isotope ratio (?(15)N) in Greenland snow nitrate and in North American remote lake sediments has decreased gradually beginning as early as ?1850 Christian Era. This decrease was attributed to increasing atmospheric deposition of anthropogenic nitrate, reflecting an anthropogenic impact on the global nitrogen cycle, and the impact was thought to be amplified ?1970. However, our subannually resolved ice core records of ?(15)N and major ions (e.g., NO3(-), SO4(2-)) over the last ?200 y show that the decrease in ?(15)N is not always associated with increasing NO3(-) concentrations, and the decreasing trend actually leveled off ?1970. Correlation of ?(15)N with H(+), NO3(-), and HNO3 concentrations, combined with nitrogen isotope fractionation models, suggests that the ?(15)N decrease from ?1850-1970 was mainly caused by an anthropogenic-driven increase in atmospheric acidity through alteration of the gas-particle partitioning of atmospheric nitrate. The concentrations of NO3(-) and SO4(2-) also leveled off ?1970, reflecting the effect of air pollution mitigation strategies in North America on anthropogenic NO(x) and SO2 emissions. The consequent atmospheric acidity change, as reflected in the ice core record of H(+) concentrations, is likely responsible for the leveling off of ?(15)N ?1970, which, together with the leveling off of NO3(-) concentrations, suggests a regional mitigation of anthropogenic impact on the nitrogen cycle. Our results highlight the importance of atmospheric processes in controlling ?(15)N of nitrate and should be considered when using ?(15)N as a source indicator to study atmospheric flux of nitrate to land surface/ecosystems.

SUBMITTER: Geng L

PROVIDER: S-EPMC4000786 | biostudies-other | 2014 Apr

REPOSITORIES: biostudies-other

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Nitrogen isotopes in ice core nitrate linked to anthropogenic atmospheric acidity change.

Geng Lei L Alexander Becky B Cole-Dai Jihong J Steig Eric J EJ Savarino Joël J Sofen Eric D ED Schauer Andrew J AJ

Proceedings of the National Academy of Sciences of the United States of America 20140407 16

Nitrogen stable isotope ratio (δ(15)N) in Greenland snow nitrate and in North American remote lake sediments has decreased gradually beginning as early as ∼1850 Christian Era. This decrease was attributed to increasing atmospheric deposition of anthropogenic nitrate, reflecting an anthropogenic impact on the global nitrogen cycle, and the impact was thought to be amplified ∼1970. However, our subannually resolved ice core records of δ(15)N and major ions (e.g., NO3(-), SO4(2-)) over the last ∼20 ...[more]

PMID: 24711383

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Project description:BackgroundIn order to grow, plants rely on soil nutrients which can vary both spatially and temporally depending on the environment, the soil type or the microbial activity. An essential nutrient is nitrogen, which is mainly accessible as nitrate and ammonium. Many studies have investigated transport genes for these ions in Arabidopsis thaliana and recently in crop species, including Maize, Rice and Barley. However, in most crop species, an understanding of the participants in nitrate and ammonium transport across the soil plant continuum remains undefined.ResultsWe have mapped a non-exhaustive set of putative nitrate and ammonium transporters in maize. The selected transporters were defined based on previous studies comparing nitrate transport pathways conserved between Arabidopsis and Zea mays (Plett D et. al, PLOS ONE 5:e15289, 2010). We also selected genes from published studies (Gu R et. al, Plant and Cell Physiology, 54:1515-1524, 2013, Garnett T et. al, New Phytol 198:82-94, 2013, Garnett T et. al, Frontiers in Plant Sci 6, 2015, Dechorgnat J et. al, Front Plant Sci 9:531, 2018). To analyse these genes, the plants were grown in a semi-hydroponic system to carefully control nitrogen delivery and then harvested at both vegetative and reproductive stages. The expression patterns of 26 putative nitrogen transporters were then tested. Six putative genes were found not expressed in our conditions. Transcripts of 20 other genes were detected at both the vegetative and reproductive stages of maize development. We observed the expression of nitrogen transporters in all organs tested: roots, young leaves, old leaves, silks, cobs, tassels and husk leaves. We also followed the gene expression response to nitrogen starvation and resupply and uncovered mainly three expression patterns: (i) genes unresponsiveness to nitrogen supply; (ii) genes showing an increase of expression after nitrogen starvation; (iii) genes showing a decrease of expression after nitrogen starvation.ConclusionsThese data allowed the mapping of putative nitrogen transporters in maize at both the vegetative and reproductive stages of development. No growth-dependent expression was seen in our conditions. We found that nitrogen transporter genes were expressed in all the organs tested and in many cases were regulated by the availability of nitrogen supplied to the plant. The gene expression patterns in relation to organ specificity and nitrogen availability denote a speciality of nitrate and ammonium transporter genes and their probable function depending on the plant organ and the environment.

Dataset Information

Nitrogen isotopes in ice core nitrate linked to anthropogenic atmospheric acidity change.

Publications

Nitrogen isotopes in ice core nitrate linked to anthropogenic atmospheric acidity change.

Similar Datasets

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