scholarly journals A coupled two-dimensional hydrodynamic and terrestrial input model to simulate CO<sub>2</sub> diffusive emissions from lake systems

2013 ◽  
Vol 6 (2) ◽  
pp. 3509-3556 ◽  
Author(s):  
H. Wu ◽  
C. Peng ◽  
M. Lucotte ◽  
N. Soumis ◽  
Y. Gélinas ◽  
...  
Keyword(s):  
Aquatic Ecosystems ◽  
Field Measurements ◽  
Terrestrial Ecosystems ◽  
Accurate Estimation ◽  
Diffusive Flux ◽  
Two Dimensional ◽  
Quality Model ◽  
Terrestrial Organic Matter ◽  
Carbon Dioxide Co2 ◽  
Lake Systems

Abstract. Most lakes worldwide are supersaturated with carbon dioxide (CO2) and consequently act as atmospheric net sources. Since CO2 is a major greenhouse gas (GHG), the accurate estimation of CO2 exchanges at air/water interfaces of aquatic ecosystems is vital in quantifying the carbon budget of aquatic ecosystems overall. To date, lacustrine CO2 emissions are poorly understood, and lake carbon source proportions remain controversial, largely due to a lack of integration between aquatic and terrestrial ecosystems. In this paper a new process-based model (TRIPLEX-Aquatic) is introduced incorporating both terrestrial inputs and aquatic biogeochemical processes to estimate diffusive emissions of CO2 from lake systems. The model was built from a two-dimensional hydrological and water quality model coupled with a new lacustrine CO2 diffusive flux model. For calibration and validation purposes, two years of data collected in the field from two small boreal oligotrophic lakes located in Québec (Canada) were used to parameterize and test the model by comparing simulations with observations for both hydrodynamic and carbon process accuracy. Model simulations were accordant with field measurements in both calibration and verification. Consequently, the TRIPLEX-Aquatic model was used to estimate the annual mean CO2 diffusive flux and predict terrestrial dissolved organic carbon (DOC) impacts on the CO2 budget for both lakes. Results show a significant fraction of the CO2 diffusive flux (~30–45%) from lakes was primarily attributable to the input and mineralization of terrestrial DOC, which indicated terrestrial organic matter was the key player in the diffusive flux of CO2 from oligotropical lake systems in Québec, Canada.

Assessment of Turbulent Processes in Lake Kinneret by the Two-Dimensional Reservoir Water Quality Model “Better”

1993 ◽  
Vol 27 (7-8) ◽  
pp. 381-385 ◽  
Author(s):  
Y. Oziransky ◽  
B. Shteinman
Keyword(s):  
Water Body ◽  
River Mouth ◽  
Temporal Distribution ◽  
Lake Kinneret ◽  
Toxic Substances ◽  
Two Dimensional ◽  
Quality Model ◽  
Reservoir Water ◽  
The North ◽  
Longitudinal Gradients

Data of high spatial and temporal resolution, and a special sampling program are essential for successful application of mathematical models designed to reproduce observed seasonal patterns of temperature, dissolved oxygen, nutrients, pH, and algal biomass for both vertical and longitudinal gradients in a water body. Lake Kinneret suspended solids are of great potential value for estimating transport, exposure to water body elements, and fate of many toxic substances. Therefore the distribution of admixtures in two longitudinal and five vertical segmentation schemes were examined with the two-dimensional water body quality box model “BETTER” (Bender et al, 1990). The transects were taken in the north-western part of Lake Kinneret close to the Jordan River mouth and the National Water Carrier (NWC) head pumping station. The outflow volumes were given according to regular sampling of natural speed of water outflow from different lake layers under calm conditions. Temporal distribution of mixing concentrations as well as turbulent diffusion horizontal coefficients due to the spatial distribution of turbulent scale were obtained during the model's run with the December 1991 data.

Ultrasonic Imaging of a Crack Using Modified Time Reversal

2016 ◽  
Vol 846 ◽  
pp. 553-558
Author(s):  
Jed Guinto ◽  
Philippe Blanloeuil ◽  
Chun H. Wang ◽  
Francis Rose ◽  
Martin Veidt
Keyword(s):  
Time Reversal ◽  
Computational Simulation ◽  
Field Measurements ◽  
Tone Burst ◽  
Data Matrix ◽  
Accurate Estimation ◽  
Diffraction Tomography ◽  
Static Data ◽  
Reconstruction Quality ◽  
Scatter Field

A majority of the research in Structural Health Monitoring focuses on detection of damage. This paper presents a method of imaging crack damage in an isotropic material using the Time Reversal imaging algorithm. Inputs for the algorithm are obtained via computational simulation of the propagation field of a crack in a medium under tone-burst excitation. The approach is similar to existing techniques such as Diffraction Tomography which makes use of the multi-static data matrix constructed using scatter field measurements from the computational simulation. Results indicate excellent reconstruction quality and accurate estimation of damage size.

scholarly journals Drainage of organic soils and GHG emissions: Validation with country data

2020 ◽  
Author(s):  
Giulia Conchedda ◽  
Francesco N. Tubiello
Keyword(s):  
East Asia ◽  
Oil Palm ◽  
Ghg Emissions ◽  
Field Measurements ◽  
Organic Soils ◽  
Past Century ◽  
South East Asia ◽  
Tropical Peatlands ◽  
Carbon Dioxide Co2 ◽  
Reported Data

Abstract. Drainage of large areas with organic soils was conducted over the past century to free land for agriculture. A significant acceleration of such trends was observed in recent decades in South-East Asia, largely driven by drainage of tropical peatlands, an important category of organic soils, for cultivation of oil palm. This work presents methods and main results of a new methodology developed for FAOSTAT, whereby the overlay of dynamic maps of land cover and the use of information on histosols allows the production of a global annual dataset of drained area and emissions over a time series, covering the period 1990–2019. This is an improvement over the existing FAO approach, which had produced only a static map of drained organic soils for the year 2000. Results indicate that drained area and emissions increased by 13 percent globally since 1990, reaching in 2019 24 million ha of drained organic soils, with world total emissions of 830 million tonnes of carbon dioxide (CO2) equivalent. Of these totals, the largest contribution was from the drainage of tropical peatlands in South-East Asia, generating nearly half of global emissions. Results were validated against national data reported by countries to the UN Climate Convention and to well established literature. Overall, the validation yielded a good agreement with these sources. FAOSTAT estimates explained about 60 percent of the variability in official country reported data. The predicted emissions were virtually identical – with over 90 percent of explained variability – to official data from Indonesia, currently the top emitting country by drained organic soils. Also, calculated emissions factors for oil palm plantations in Indonesia and Malaysia were in the same range and very close to emissions factors derived from detailed field measurements. This validation suggests that the FAO estimates may be a useful and sound reference in support of countries reporting needs. Data are made available as open access via the Zenodo portal (Tubiello and Conchedda, 2020) with DOI https://doi.org/10.5281/zenodo.3942370.

scholarly journals Prediction of Holocene Mercury Accumulation Trends by Combining Palynological and Geochemical Records of Lake Sediments (Black Forest, Germany)

2018 ◽  
Author(s):  
Martin Schütze ◽  
Gegeensuvd Tserendorj ◽  
Marta Pérez-Rodríguez ◽  
Manfred Rösch ◽  
Harald Biester
Keyword(s):  
Principal Component Regression ◽  
Principal Component ◽  
Terrestrial Ecosystems ◽  
Forest Vegetation ◽  
Warm Climate ◽  
Black Forest ◽  
Components Analysis ◽  
Lake Systems ◽  
Hg Accumulation

Forest vegetation plays a key role in the cycling of mercury (Hg) and organic matter (OM) in terrestrial ecosystems. Litterfall has been indicated as the major transport vector of atmospheric Hg to forest soils, which is eventually transported and stored in the sediments of forest lakes. Hence, it is important to understand how changes in forest vegetation affect Hg in soil and its biogeochemical cycling in lake systems. We investigated the pollen records and the geochemical compositions of sediments from two lakes (Schurmsee and Glaswaldsee) in the Black Forest (Germany) to evaluate whether long-term shifts in forest vegetation induced by climate or land use influenced Hg accumulation in the lakes. We were particularly interested to determine whether coniferous forests were associated with a larger export of Hg to aquatic systems than deciduous forests. Principal components analysis followed by principal component regression enabled us to describe the evolution of the weight of the latent processes determining the accumulation of Hg over time. Our results emphasize that the in-lake uptake of Hg during warm climate periods, soil erosion after deforestation and emissions from mining and other human activities triggered changes in Hg accumulation during the Holocene stronger than the changes caused by forest vegetation alone.

scholarly journals An automated procedure for estimating the leaf area index (LAI) of woodland ecosystems using digital imagery, MATLAB programming and its application to an examination of the relationship between remotely sensed and field measurements of LAI

2008 ◽  
Vol 35 (10) ◽  
pp. 1070 ◽  
Author(s):  
Sigfredo Fuentes ◽  
Anthony R. Palmer ◽  
Daniel Taylor ◽  
Melanie Zeppel ◽  
Rhys Whitley ◽  
...  
Keyword(s):  
Leaf Area Index ◽  
Leaf Area ◽  
Gap Analysis ◽  
Digital Camera ◽  
Field Measurements ◽  
Accurate Estimation ◽  
Image Capture ◽  
Area Index ◽  
Modis Lai ◽  
Matlab Programming

Leaf area index (LAI) is one of the most important variables required for modelling growth and water use of forests. Functional–structural plant models use these models to represent physiological processes in 3-D tree representations. Accuracy of these models depends on accurate estimation of LAI at tree and stand scales for validation purposes. A recent method to estimate LAI from digital images (LAID) uses digital image capture and gap fraction analysis (Macfarlane et al. 2007b) of upward-looking digital photographs to capture canopy LAID (cover photography). After implementing this technique in Australian evergreen Eucalyptus woodland, we have improved the method of image analysis and replaced the time consuming manual technique with an automated procedure using a script written in MATLAB 7.4 (LAIM). Furthermore, we used this method to compare MODIS LAI values with LAID values for a range of woodlands in Australia to obtain LAI at the forest scale. Results showed that the MATLAB script developed was able to successfully automate gap analysis to obtain LAIM. Good relationships were achieved when comparing averaged LAID and LAIM (LAIM = 1.009 – 0.0066 LAID; R2 = 0.90) and at the forest scale, MODIS LAI compared well with LAID (MODIS LAI = 0.9591 LAID – 0.2371; R2 = 0.89). This comparison improved when correcting LAID with the clumping index to obtain effective LAI (MODIS LAI = 1.0296 LAIe + 0.3468; R2 = 0.91). Furthermore, the script developed incorporates a function to connect directly a digital camera, or high resolution webcam, from a laptop to obtain cover photographs and LAI analysis in real time. The later is a novel feature which is not available on commercial LAI analysis softwares for cover photography. This script is available for interested researchers.

Inter-comparison of remotely-sensed actual evapotranspiration products in the Zayandehrud river basin, Iran

2021 ◽  
Author(s):  
Neda Abbasi ◽  
Hamideh Nouri ◽  
Sattar Chavoshi Borujeni ◽  
Pamela Nagler ◽  
Christian Opp ◽  
...  
Keyword(s):  
Vegetation Index ◽  
Normalized Difference Vegetation Index ◽  
Field Measurements ◽  
Water Shortage ◽  
Remotely Sensed ◽  
Irrigation Scheduling ◽  
Accurate Estimation ◽  
Agricultural Areas ◽  
Eta Products

&lt;p&gt;Accurate estimation of evapotranspiration (ET) helps to create a better understanding of water allocation, irrigation scheduling, and crop management especially in arid and semiarid regions where agricultural areas are far more affected by water shortage and drought events. Remote sensing (RS) facilitates estimating the ET in regions where long-term field measurements are missed.&amp;#160; In this study, we compare the performance of free open-access remotely sensed actual ET products at eleven counties of the Zayandehrud basin. The Zayandehrud basin, one of the major watersheds of Iran, suffers from recurrent droughts and long-term impacts of aridity. The RS products used in this study are namely WaPOR (2009-2019), MOD16A2 (2003-2019), SSEBOp (2003-2019). We also merged the two products of SSEBOp and WaPOR and assessed its performance. To prepare the Merged ETa Product (MEP), WaPOR was resampled to the spatial resolution of SSEBOp. Then, the average pixel values of the resampled ETa product and SSEBOp were calculated. To compare ETa estimations over croplands in each county, maximum Normalized Difference Vegetation Index (NDVI) maps at annual scale (2003-2019) were prepared using LANDSAT 5, 7, and 8 images. Annual mean ETa estimations were then extracted over croplands by using annual maximum NDVI layers. We compared the RS-based ETa with reported long-term ETa values extracted from the local available literature. Our results showed a consistent underestimation of MOD16A2 in all counties. The MEP and WaPOR outperformed other products in the estimation of ETa in seven. Estimations of WaPOR and SSEBOp agreed in most of the counties. Our analysis displayed that, although MOD16A2 underestimated ETa values, it could together with SSEBOp capture the drought better than that of WaPOR and MEP in the lower reaches of the basin. Further study is needed to evaluate the monthly and seasonal performance of RS-based ETa products.&lt;/p&gt;

Impact of structure, doping and defect- engineering in 2D materials for CO2 capture and conversion

2021 ◽  
Author(s):  
E. J. Jelmy ◽  
Nishanth Thomas ◽  
Dhanu Treasa Mathew ◽  
Jesna Louis ◽  
Nisha T Padmanabhan ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Co2 Capture ◽  
2D Materials ◽  
Vital Role ◽  
Energy Crisis ◽  
Two Dimensional ◽  
Defect Engineering ◽  
Anthropogenic Carbon ◽  
2D Nanomaterials ◽  
Carbon Dioxide Co2

The investigations on anthropogenic carbon dioxide (CO2) capture and conversion have a vital role in eradicating the global warming and energy crisis. In this context, defect- engineered two-dimensional (2D) nanomaterials...

Comparison of field measurements to predicted reaeration coefficients, k2, in the application of a water quality model, QUAL2E, to a tropical river

2002 ◽  
Vol 46 (9) ◽  
pp. 47-54 ◽  
Author(s):  
M. Mohamed ◽  
J.D. Stednick ◽  
F.M. Smith
Keyword(s):  
Water Quality ◽  
Standard Error ◽  
Field Measurements ◽  
Water Quality Modeling ◽  
Low Flow ◽  
Quality Model ◽  
Predictive Equations ◽  
Discharge Data ◽  
Study Results ◽  
Reaeration Coefficient

Some of the many tools used for watershed management are mathematical and computer models for wasteload allocations. QUAL2E is one of the most popular water quality models used for such purposes. The question arises as to whether the model is applicable in a different climate such as that in the tropics. In this study, QUAL2E was used to model Sg. Selangor River in Malaysia using the predictive equations for reaeration coefficient (k2) within the model and the measured reaeration coefficients for the river. The study results indicated that use of the reaeration coefficient (k2) measured at Sg. Selangor River did give the lowest standard error (SE) for the simulation of water quality during the 7Q10 low-flow period which is considered as the worst scene scenario in water quality modeling. But during calibration and validation using actual low-flow discharge data, the measured reaeration coefficients did not give the lowest standard error (SE). In conclusion, the results indicated that QUAL2E is applicable in tropical rivers when used with the modeled river parameters (i.e. hydraulic parameters, meteorological conditions etc.). Measured reaeration coefficients produced good results and several predictive equations also produced comparatively good results.

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