scholarly journals Satellite evidence of substantial rain-induced soil emissions of ammonia across the Sahel

2018 ◽  
Vol 18 (22) ◽  
pp. 16713-16727 ◽  
Author(s):  
Jonathan E. Hickman ◽  
Enrico Dammers ◽  
Corinne Galy-Lacaux ◽  
Guido R. van der Werf
Keyword(s):  
Soil Moisture ◽  
Rainy Season ◽  
Agricultural Soils ◽  
Fine Particulate Matter ◽  
Primary Source ◽  
N Deposition ◽  
Box Model ◽  
Ozone Monitoring Instrument ◽  
Animal Excreta ◽  
Birch Effect

Abstract. Atmospheric ammonia (NH3) is a precursor to fine particulate matter formation and contributes to nitrogen (N) deposition, with potential implications for the health of humans and ecosystems. Agricultural soils and animal excreta are the primary source of atmospheric NH3, but natural soils can also be an important emitter. In regions with distinct dry and wet seasons such as the Sahel, the start of the rainy season triggers a pulse of biogeochemical activity in surface soils known as the Birch effect, which is often accompanied by emissions of microbially produced gases such as carbon dioxide and nitric oxide. Field and lab studies have sometimes, but not always, observed pulses of NH3 after the wetting of dry soils; however, the potential regional importance of these emissions remains poorly constrained. Here we use satellite retrievals of atmospheric NH3 using the Infrared Atmospheric Sounding Interferometer (IASI) regridded at 0.25∘ resolution, in combination with satellite-based observations of precipitation, surface soil moisture, and nitrogen dioxide concentrations, to reveal substantial precipitation-induced pulses of NH3 across the Sahel at the onset of the rainy season in 2008. The highest concentrations of NH3 occur in pulses during March and April when NH3 biomass burning emissions estimated for the region are low. For the region of the Sahel spanning 10 to 16∘ N and 0 to 30∘ E, changes in NH3 concentrations are weakly but significantly correlated with changes in soil moisture during the period from mid-March through April when the peak NH3 concentrations occur (r=0.28, p=0.02). The correlation is also present when evaluated on an individual pixel basis during April (r=0.16, p<0.001). Average emissions for the entire Sahel from a simple box model are estimated to be between 2 and 6 mg NH3 m−2 d−1 during peaks of the observed pulses, depending on the assumed effective NH3 lifetime. These early season pulses are consistent with surface observations of monthly concentrations, which show an uptick in NH3 concentration at the start of the rainy season for sites in the Sahel. The NH3 concentrations in April are also correlated with increasing tropospheric NO2 concentrations observed by the Ozone Monitoring Instrument (r=0.78, p<0.0001), which have previously been attributed to the Birch effect. Box model results suggest that pulses occurring over a 35-day period in March and April are responsible for roughly one-fifth of annual emissions of NH3-N from the Sahel. We conclude that precipitation early in the rainy season is responsible for substantial NH3 emissions in the Sahel, likely representing the largest instantaneous fluxes of gas-phase N from the region during the year.

scholarly journals Satellite evidence of substantial rain-induced soil emissions of ammonia across the Sahel

2018 ◽  
Author(s):  
Jonathan E. Hickman ◽  
Enrico Dammers ◽  
Corinne Galy-Lacaux ◽  
Guido R. van der Werf
Keyword(s):  
Soil Moisture ◽  
Rainy Season ◽  
Agricultural Soils ◽  
Fine Particulate Matter ◽  
Primary Source ◽  
Fire Emissions ◽  
Fine Particulate ◽  
Animal Excreta ◽  
Soil Emissions ◽  
Birch Effect

Abstract. Atmospheric ammonia (NH3) is a precursor to fine particulate matter formation and contributes to nitrogen deposition, with potential implications for the health of humans and ecosystems. Agricultural soils and animal excreta are the primary source of atmospheric NH3, but natural soils can also be an important emittor. In regions with distinct dry and wet seasons such as the Sahel, the start of the rainy season triggers a pulse of biogeochemical activity in surface soils known as the Birch effect, which is often accompanied by emissions of microbially-produced gases such as carbon dioxide and nitric oxide. Field and lab studies have sometimes, but not always, observed pulses of NH3 after the wetting of dry soils; however, the potential regional importance of these emissions remains poorly constrained. Here we use satellite retrievals of atmospheric NH3 using the Infrared Atmospheric Sounding Interferometer (IASI) regridded at 0.25° resolution, in combination with satellite-based observations of precipitation, surface soil moisture, and nitric dioxide concentrations, to present evidence of substantial precipitation-induced pulses of NH3 across the Sahel at the onset of the rainy season in 2008. The highest concentrations of NH3 occur in pulses during March and April, when biomass burning emissions estimated for the region by the Global Fire Emissions Database database are low. For the region of the Sahel spanning 10° to 16° N and 0° to 30° E, changes in NH3 concentrations are weakly but significantly correlated with changes in soil moisture during the period from mid-March through April, when the peak NH3 concentrations occur (r = 0.28, p = 0.02). The correlation is also present when evaluated on an individual pixel-basis during April (r = 0.16, p 

scholarly journals Effects of Monoculture, Crop Rotation, and Soil Moisture Content on Selected Soil Physicochemical and Microbial Parameters in Wheat Fields

2012 ◽  
Vol 2012 ◽  
pp. 1-13 ◽  
Author(s):  
A. Marais ◽  
M. Hardy ◽  
M. Booyse ◽  
A. Botha
Keyword(s):  
Soil Moisture ◽  
Microbial Communities ◽  
Crop Rotation ◽  
Management Practices ◽  
Agricultural Soils ◽  
Soil Microbial Communities ◽  
Soil Microbial Activity ◽  
Most Probable Number ◽  
Probable Number ◽  
Soil Microbial

Different plants are known to have different soil microbial communities associated with them. Agricultural management practices such as fertiliser and pesticide addition, crop rotation, and grazing animals can lead to different microbial communities in the associated agricultural soils. Soil dilution plates, most-probable-number (MPN), community level physiological profiling (CLPP), and buried slide technique as well as some measured soil physicochemical parameters were used to determine changes during the growing season in the ecosystem profile in wheat fields subjected to wheat monoculture or wheat in annual rotation with medic/clover pasture. Statistical analyses showed that soil moisture had an over-riding effect on seasonal fluctuations in soil physicochemical and microbial populations. While within season soil microbial activity could be differentiated between wheat fields under rotational and monoculture management, these differences were not significant.

Laboratory and field measurements of HONO emissions from agricultural soils in Guangdong of China 

2021 ◽  
Author(s):  
Baobin Han ◽  
Peng Cheng ◽  
Yihang Yu ◽  
Wenda Yang ◽  
Zhilin Tian ◽  
...  
Keyword(s):  
Emission Rate ◽  
Agricultural Soils ◽  
Pore Space ◽  
Primary Source ◽  
Field Measurements ◽  
Laboratory Studies ◽  
Release Rates ◽  
Laboratory Results ◽  
Flux Measurements ◽  
Soil Flux

&lt;p&gt;Laboratory studies indicated that soil could produce considerable nitrous acid (HONO) emissions, which is the main primary source of hydroxyl radical (OH) in the troposphere. However, very few field observations of HONO emission from soil were reported. In order to relate laboratory results and field measurements, we measured HONO emissions from 7 representative agricultural soils (rice, vegetables, orchards, peanuts, potatoes, sugarcane and maize) in Guangdong under controlled laboratory conditions, and took flux measurements on 2 of them (rice and vegetables) by dynamic chambers in the field. Generally, release rates of HONO from the seven soils increased with temperature and varied with soil moisture, and the optimum release rates can be reached under specific values of water-filled pore space (WFPS), which is considered to be beneficial to nitrification. The seven soils' optimum release rates ranged from 1.24 to 43.19 ng kg&lt;sup&gt;-1&lt;/sup&gt; s&lt;sup&gt;-1&lt;/sup&gt;, and the Q&lt;sub&gt;10&lt;/sub&gt; (It is defined as the multiple of the increase of soil gas emission rate when the temperature increases by 10&amp;#8451;) ranged from 1.03 to 2.25. Formulas were deduced from the lab results to express HONO emissions for every soil. Flux measurements on two soils varied around -1 to 4 ng N m&lt;sup&gt;-2&lt;/sup&gt; s&lt;sup&gt;-1&lt;/sup&gt;, and both showed similar diurnal variations with peaks around noontime and very low even negative values during nighttime. There were good correlations between HONO fluxes and soil temperature (R&lt;sup&gt;2&lt;/sup&gt;=0.5). Furthermore, irrigation enhanced the HONO emission substantially. However, a large discrepancy existed between soil HONO emissions measured in lab and low HONO fluxes in field. More investigations are needed to explain the paradox.&lt;/p&gt;

scholarly journals Physically-based modelling of hydrological processes in a tropical headwater catchment (West Africa) – process representation and multi-criteria validation

2006 ◽  
Vol 10 (6) ◽  
pp. 829-847 ◽  
Author(s):  
S. Giertz ◽  
B. Diekkrüger ◽  
G. Steup
Keyword(s):  
Soil Moisture ◽  
Rainy Season ◽  
Overland Flow ◽  
Soil Layer ◽  
Hydrological Processes ◽  
Runoff Generation ◽  
Field Investigations ◽  
Physically Based ◽  
In The Beginning ◽  
Headwater Catchment

Abstract. The aim of the study was to test the applicability of a physically-based model to simulate the hydrological processes in a headwater catchment in Benin. Field investigations in the catchment have shown that lateral processes such as surface runoff and interflow are most important. Therefore, the 1-D SVAT-model SIMULAT was modified to a semi-distributed hillslope version (SIMULAT-H). Based on a good database, the model was evaluated in a multi-criteria validation using discharge, discharge components and soil moisture data. For the validation of discharge, good results were achieved for dry and wet years. The main differences were observable in the beginning of the rainy season. A comparison of the discharge components determined by hydro-chemical measurements with the simulation revealed that the model simulated the ratio of groundwater fluxes and fast runoff components correctly. For the validation of the discharge components of single events, larger differences were observable, which was partly caused by uncertainties in the precipitation data. The representation of the soil moisture dynamics by the model was good for the top soil layer. For deeper soil horizons, which are characterized by higher gravel content, the differences between simulated and measured soil moisture were larger. A good agreement of simulation results and field investigations was achieved for the runoff generation processes. Interflow is the predominant process on the upper and the middle slopes, while at the bottom of the hillslope groundwater recharge and – during the rainy season – saturated overland flow are important processes.

scholarly journals Impact of elevated precipitation, nitrogen deposition and warming on soil respiration in a temperate desert

2018 ◽  
Vol 15 (7) ◽  
pp. 2007-2019 ◽  
Author(s):  
Ping Yue ◽  
Xiaoqing Cui ◽  
Yanming Gong ◽  
Kaihui Li ◽  
Keith Goulding ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Soil Respiration ◽  
Soil Temperature ◽  
Carbon Dioxide Emissions ◽  
Environmental Changes ◽  
N Deposition ◽  
Climate Feedback ◽  
Single Factor ◽  
Extreme Precipitation Events ◽  
Temperate Desert

Abstract. Soil respiration (Rs) is the most important source of carbon dioxide emissions from soil to atmosphere. However, it is unclear what the interactive response of Rs would be to environmental changes such as elevated precipitation, nitrogen (N) deposition and warming, especially in unique temperate desert ecosystems. To investigate this an in situ field experiment was conducted in the Gurbantunggut Desert, northwest China, from September 2014 to October 2016. The results showed that precipitation and N deposition significantly increased Rs, but warming decreased Rs, except in extreme precipitation events, which was mainly through its impact on the variation of soil moisture at 5 cm depth. In addition, the interactive response of Rs to combinations of the factors was much less than that of any single-factor, and the main response was a positive effect, except for the response from the interaction of increased precipitation and high N deposition (60 kg N ha−1 yr−1). Although Rs was found to show a unimodal change pattern with the variation of soil moisture, soil temperature and soil NH4+-N content, and it was significantly positively correlated to soil dissolved organic carbon (DOC) and pH, a structural equation model found that soil temperature was the most important controlling factor. Those results indicated that Rs was mainly interactively controlled by the soil multi-environmental factors and soil nutrients, and was very sensitive to elevated precipitation, N deposition and warming. However, the interactions of multiple factors largely reduced between-year variation of Rs more than any single-factor, suggesting that the carbon cycle in temperate deserts could be profoundly influenced by positive carbon–climate feedback.

scholarly journals New constraints on biogenic emissions using satellite-based estimates of carbon monoxide fluxes

2019 ◽  
Vol 19 (21) ◽  
pp. 13569-13579 ◽  
Author(s):  
Helen M. Worden ◽  
A. Anthony Bloom ◽  
John R. Worden ◽  
Zhe Jiang ◽  
Eloise A. Marais ◽  
...  
Keyword(s):  
Carbon Monoxide ◽  
Transport Model ◽  
A Priori ◽  
Primary Source ◽  
Biogenic Emissions ◽  
Chemical Production ◽  
Chemical Transport Model ◽  
Ozone Monitoring Instrument ◽  
Top Down ◽  
Decadal Scale

Abstract. Biogenic non-methane volatile organic compounds (NMVOCs) emitted from vegetation are a primary source for the chemical production of carbon monoxide (CO) in the atmosphere, and these biogenic emissions account for about 18 % of the global CO burden. Partitioning CO fluxes to different source types in top-down inversion methods is challenging; typically a simple scaling of the posterior flux to prior flux values for fossil fuel, biogenic and biomass burning sources is used. Here we show top-down estimates of biogenic CO fluxes using a Bayesian inference approach, which explicitly accounts for both posterior and a priori CO flux uncertainties. This approach re-partitions CO fluxes following inversion of Measurements Of Pollution In The Troposphere (MOPITT) CO observations with the GEOS-Chem model, a global chemical transport model driven by assimilated meteorology from the NASA Goddard Earth Observing System (GEOS). We compare these results to the prior information for CO used to represent biogenic NMVOCs from GEOS-Chem, which uses the Model of Emissions of Gases and Aerosols from Nature (MEGAN) for biogenic emissions. We evaluate the a posteriori biogenic CO fluxes against top-down estimates of isoprene fluxes using Ozone Monitoring Instrument (OMI) formaldehyde observations. We find similar seasonality and spatial consistency in the posterior CO and top-down isoprene estimates globally. For the African savanna region, both top-down CO and isoprene seasonality vary significantly from the MEGAN a priori inventory. This method for estimating biogenic sources of CO will provide an independent constraint on modeled biogenic emissions and has the potential for diagnosing decadal-scale changes in emissions due to land-use change and climate variability.

scholarly journals Water Budget on Various Land Use Areas Using NARR Reanalysis Data in Florida

2011 ◽  
Vol 2011 ◽  
pp. 1-13 ◽  
Author(s):  
Chi-Han Cheng ◽  
Fidelia Nnadi
Keyword(s):  
Land Use ◽  
Soil Moisture ◽  
Water Budget ◽  
Urban Forest ◽  
Primary Source ◽  
Reanalysis Data ◽  
Rooting Depth ◽  
Drought Event ◽  
Rainfall Anomalies ◽  
Regional Reanalysis

1992 to 2002 data from North American Regional Reanalysis (NARR) were used to investigate water budget on five land use areas: urban, forest, agriculture, lake, and wetland in the state of Florida, USA. The data were evaluated based on the anomalies of rainfall, evaporation, and soil moisture from the average condition. The anomalies were used to investigate the effect of extreme conditions on water budget parameters for various land uses in both northeast and south of Florida. The results showed that extreme events such as La Niña strongly affected the water budget on land-use areas in both regions as the negative monthly rainfall anomalies were observed during the 1999-2000 event, while EI Niño and thunderstorms in summer caused positive rainfall anomalies with more than 70% in all study areas. Higher rainfall led to higher soil moisture anomalies for the agriculture, forest, and wetland from 1992 to May 1998 in both study regions. However, soil moisture becomes primary source for evaporation in drier conditions, and differences in capacity of plants access water, often dictated by the rooting depth, can result in contrasting evaporative losses across vegetation types. Hence, the forest, which had the deeper roots, had lower soil moisture anomalies, but higher evaporation anomalies than agriculture area during the drought event.

scholarly journals Testing the performance of state-of-the-art dust emission schemes using DO4Models field data

2015 ◽  
Vol 8 (2) ◽  
pp. 341-362 ◽  
Author(s):  
K. Haustein ◽  
R. Washington ◽  
J. King ◽  
G. Wiggs ◽  
D. S. G. Thomas ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Field Data ◽  
Dust Emission ◽  
Shear Velocity ◽  
Box Model ◽  
Wind Speeds ◽  
Dust Flux ◽  
Dry Lake ◽  
Order Of Magnitude ◽  
Emission Threshold

Abstract. Within the framework of the Dust Observations for Models (DO4Models) project, the performance of three commonly used dust emission schemes is investigated in this paper using a box model environment. We constrain the model with field data (surface and dust particle properties as well as meteorological parameters) obtained from a dry lake bed with a crusted surface in Botswana during a 3 month period in 2011. Our box model results suggest that all schemes fail to reproduce the observed horizontal dust flux. They overestimate the magnitude of the flux by several orders of magnitude. The discrepancy is much smaller for the vertical dust emission flux, albeit still overestimated by up to an order of magnitude. The key parameter for this mismatch is the surface crusting which limits the availability of erosive material, even at higher wind speeds. The second-most important parameter is the soil size distribution. Direct dust entrainment was inferred to be important for several dust events, which explains the smaller gap between modelled and measured vertical dust fluxes. We conclude that both features, crusted surfaces and direct entrainment, need to be incorporated into dust emission schemes in order to represent the entire spectra of source processes. We also conclude that soil moisture exerts a key control on the threshold shear velocity and hence the emission threshold of dust in the model. In the field, the state of the crust is the controlling mechanism for dust emission. Although the crust is related to the soil moisture content to some extent, we are not as yet able to deduce a robust correlation between state of crust and soil moisture.

scholarly journals Physically-based modelling of hydrological processes in a tropical headwater catchment in Benin (West Africa) – process representation and multi-criteria validation

2006 ◽  
Vol 3 (2) ◽  
pp. 595-651 ◽  
Author(s):  
S. Giertz ◽  
B. Diekkrüger ◽  
G. Steup
Keyword(s):  
Soil Moisture ◽  
Rainy Season ◽  
Overland Flow ◽  
Soil Layer ◽  
Hydrological Processes ◽  
Runoff Generation ◽  
Field Investigations ◽  
Physically Based ◽  
In The Beginning ◽  
Headwater Catchment

Abstract. The aim of the study was to test the applicability of a physically-based model to simulate the hydrological processes in a headwater catchment in Benin. Field investigations in the catchment have shown that lateral processes as surface runoff and interflow are most important. Therefore the 1-D SVAT-model SIMULAT was modified to a hillslope version (SIMULAT-H). Due to a good database the model was evaluated in a multi-criteria validation using discharge, discharge components and spatially distributed soil moisture data. For the validation of discharge good results were achieved for dry and wet years. Main differences were observable in the beginning of the rainy season. The comparison of the discharge components determined by hydrochemical measurements with the simulation revealed that the model simulated the ratio of groundwater fluxes and fast runoff components correctly. For the validation of the discharge components of single events larger differences were observable, which was partly caused by uncertainties in the precipitation data. The representation of the soil moisture dynamics by the model was good for the top soil layer. For deeper soil horizons, which are characterized by higher gravel content, the differences between simulated and measured soil moisture were larger. Concerning the runoff generation processes a good agreement of simulation results and field investigations was achieved. On the upper and the middle slope interflow is the predominant process, while at the bottom of the hillslope groundwater recharge and – during the rainy season – saturated overland flow are important processes.

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