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Effects of stream channelization on exports of nitrogen and phosphorus from north Carolina coastal plain watersheds 总被引:1,自引:0,他引:1
Laura A. Yarbro Edward J. Kuenzler Patrick J. Mulholland Robert P. Sniffen 《Environmental management》1984,8(2):151-160
Nitrogen and phosphorus exports from channelizedstream watersheds were elevated over those from nearby natural swamp-stream watersheds. Nitrate exports were significantly greater from channelized-stream watersheds, and higher exports were attributed to faster groundwater drawdown, continual streamflow, and transformation of former floodplain to croplands following channelization. Exports of total organic nitrogen and total nitrogen were also significantly greater from channelized-stream watersheds. Differences in the exports of ammonium, filterable reactive phosphorus, and filterable unreactive phosphorus between the two watershed types were not detectable. Particulate phosphorus exports were significantly higher from channelized-stream watersheds, presumably because of greater erosion potential of nearby croplands and steep channel banks in the altered watersheds. The presence of nonpoint sources of pollution increased watershed exports of nutrients regardless of stream morphology. Examination of nutrient budgets for a portion of swamp floodplain at the base of one natural-stream watershed revealed that changes in local groundwater hydrology and stream morphology associated with channelization appeared to have greater effect on nutrient exports than simply the loss of bordering forested floodplain. 相似文献
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Comparison of land nitrogen budgets for European agriculture by various modeling approaches 总被引:1,自引:0,他引:1
de Vries W Leip A Reinds GJ Kros J Lesschen JP Bouwman AF 《Environmental pollution (Barking, Essex : 1987)》2011,159(11):3254-3268
A comparison of nitrogen (N) budgets for the year 2000 of agro-ecosystems is made for the EU 27 countries by four models with different complexity and data requirements, i.e. INTEGRATOR, IDEAg, MITERRA and IMAGE. The models estimate a comparable total N input in European agriculture, i.e. 23.3–25.7 Mton N yr−1, but N uptake varies more, i.e. from 11.3 to 15.4 Mton N yr−1 leading to total N surpluses varying from 10.4 to 13.2 Mton N yr−1. The estimated overall variation at EU 27 is small for the emissions of ammonia (2.8–3.1 Mton N yr−1) and nitrous oxide (0.33–0.43 Mton N yr−1), but large for the sum of N leaching and runoff (2.7–6.3 Mton N yr−1). Unlike the overall EU estimates, the difference in N output fluxes between models is large at regional scale. This is mainly determined by N inputs, differences being highest in areas with high livestock density. 相似文献
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Maofa Ge Chenhui Ji Shengrui Tong Xinran Zhang Fangjie Li Wenqian Zhang Weiran Li Zhen Wang Gen Zhang Guiqian Tang Zirui Liu 《环境科学学报(英文版)》2023,35(2):557-569
Atmospheric oxidizing capacity (AOC) is the fundamental driving factors of chemistry process (e.g., the formation of ozone (O3) and secondary organic aerosols (SOA)) in the troposphere. However, accurate quantification of AOC still remains uncertainty. In this study, a comprehensive field campaign was conducted during autumn 2019 in downtown of Beijing, where O3 and PM2.5 episodes had been experienced successively. The observation-based model (OBM) is used to quantify the AOC at O3 and PM2.5 episodes. The strong intensity of AOC is found at O3 and PM2.5 episodes, and hydroxyl radical (OH) is the dominating daytime oxidant for both episodes. The photolysis of O3 is main source of OH at O3 episode; the photolysis of nitrous acid (HONO) and formaldehyde (HCHO) plays important role in OH formation at PM2.5 episode. The radicals loss routines vary according to precursor pollutants, resulting in different types of air pollution. O3 budgets and sensitivity analysis indicates that O3 production is transition regime (both VOC and NOx-limited) at O3 episode. The heterogeneous reaction of hydroperoxy radicals (HO2) on aerosol surfaces has significant influence on OH and O3 production rates. The HO2 uptake coefficient (γHO2) is the determining factor and required accurate measurement in real atmospheric environment. Our findings could provide the important bases for coordinated control of PM2.5 and O3 pollution. 相似文献
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