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| Titel |
New estimates of direct N2O emissions from Chinese croplands from 1980 to 2007 using localized emission factors |
| VerfasserIn |
B. Gao, X. T. Ju, Q. Zhang, P. Christie, F. S. Zhang |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 8, no. 10 ; Nr. 8, no. 10 (2011-10-31), S.3011-3024 |
| Datensatznummer |
250006170
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| Publikation (Nr.) |
 copernicus.org/bg-8-3011-2011.pdf |
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| Zusammenfassung |
| Nitrous oxide (N2O) is a long-lived greenhouse gas
with a large radiation intensity and it is emitted mainly from agricultural
land. Accurate estimates of total direct N2O emissions from croplands
on a country scale are important for global budgets of anthropogenic sources
of N2O emissions and for the development of effective mitigation
strategies. The objectives of this study were to re-estimate direct N2O
emissions using localized emission factors and a database of measurements
from Chinese croplands. We obtained N2O emission factors for paddy
fields (0.41 ± 0.04%) and uplands (1.05 ± 0.02%) from a
normalization process through cube root transformation of the original data.
After comparing the results of normalization from the original values,
Logarithmic and cube root transformations were used because the frequency of
the original data was not normally distributed. Direct N2O emissions
from Chinese croplands from 1980 to 2007 were estimated using IPCC (2006)
guidelines combined with separate localized emission factors for paddy
fields and upland areas. Direct N2O emissions from paddy fields showed
little change, increasing by 10.5% with an annual rate of increase of 0.4%
from 32.3 Gg N2O-N in 1980 to 35.7 Gg N2O-N in 2007. In
contrast, emissions from uplands changed dramatically, increasing by 308%
with an annual rate of 11% from 68.0 Gg N2O-N in 1980 to 278 Gg N2O-N
in 2007. Total direct N2O emissions from Chinese croplands
increased by 213% with an annual rate of 7.6% from 100 Gg N2O-N
in 1980 to 313 Gg N2O-N in 2007, and were determined mainly by upland
emissions (accounting for 67.8–88.6% of total emissions from 1980 to
2007). Synthetic N fertilizers played a major role in N2O emissions
from agricultural land, and the magnitude of the contributions to total
direct N2O emissions made by different amendments was synthetic N
fertilizer > manure > straw, representing about 78, 15, and 6% of
total direct N2O emissions, respectively, between 2000 and 2007. The
spatial pattern of total N2O emissions in 2007 in China shows that high
direct N2O emissions occurred mainly in the north and in the Sichuan
Basin in the southwest. The provinces with the highest emissions were Henan
(35.4 Gg) and Shandong (31.6 Gg) and Tibet had the lowest (0.65 Gg). High
direct N2O emissions per unit of arable land occurred mainly on the
North China Plain and the southeast coast. The mean value nationally was
2.52 kg N ha−1, with 18 provinces above this value and with emissions
of >4.0 kg N ha−1 in Beijing, Tianjin and in Jiangsu, Shandong,
Fujian and Henan provinces. |
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