Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “soils”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
NASA NTRS1998

Effect of land-use practice on soil moisture variability for soils covered with dense forest vegetation of Puerto Rico

Little is known about the landuse management effect on soil moisture and soil pH distribution on a landscape covered with dense tropical forest vegetation. This study was conducted at three locations where the history of the landuse management is different. Soil moisture was measured using a 6-cm three-rod Time Domain Reflectometery (TDR) probe. Disturbed soil samples were taken from the top 5-cm at the up, mid, and foothill landscape position from the same spots where soil moisture was measured. The results showed that soil moisture varies with landscape position and depth at all three locations. Soil pH and moisture variability were found to be affected by the change in landuse management and landscape position. Soil moisture distribution usually expected to be relatively higher in the foothill (P3) area of these forests than the uphill (P1) position. However, our results indicated that in the Luquillo and Guanica site the surface soil moisture was significantly higher for P1 than P3 position. These suggest that the surface and subsurface drainage in these two sites may have been poor due to the nature of soil formation and type.

Tsegaye, T.↗
NASA NTRS2010

Mineralogical and Chemical Characterization of Lunar Highland Soils: Insights into the Space Weathering of Soils on Airless Bodies

With reflectance spectroscopy, one is measuring only properties of the fine-grained regolith, most affected by space weathering. The Lunar Soil Characterization Consortium has undertaken the task of coordinated characterization of lunar soils, with respect to their mineralogical and chemical makeup. It is these lunar soils that are being used as "ground-truth" for all air30 less bodies. Modal abundances and chemistries of minerals and glasses in the finest size fractions (20-45, 10-20, and <10 microns) of four Apollo 14 and six Apollo 16 highland soils have been determined, as well as their bulk chemistry and IS/FeO values. Bi-directional reflectance measurements (0.3-2.6 microns) of all samples were performed in the RELAB. A significant fraction of nanophase Fe(sup 0) (np-Fe(sup 0)) appears to reside in agglutinitic glasses. However, as grain size of a soil decreases, the percentage of total iron present as np-Fe0 increases significantly, whereas the agglutinitic glass content rises only slightly; this is evidence for a large contribution to the IS/FeO values from the surface-correlated nanophase Fe(sup 0), particularly in the <10 micron size fraction. The compositions of the agglutinitic glasses in these fine fractions of the highland soils are different from the bulk-chemistry of that size; however, compositional trends of the glasses are not the same as those observed for mare soils. It is apparent that the glasses in the highland soils contain chemical components from outside their terrains. It is proposed that the Apollo 16 soils have been adulterated by the addition of impact-transported soil components from surrounding maria.

Taylor, Lawrence A.↗
DOE OSTI2020

Ectomycorrhizal fungal diversity interacts with soil nutrients to predict plant growth despite weak plant-soil feedbacks

Background and aims Plant-soil feedbacks are the result of multiple abiotic and biotic mechanisms. However, few studies have addressed how feedbacks vary based on abiotic context or attempted to identify microbiota responsible for feedbacks. In this work, we investigated whether plant-soil feedbacks of an ectomycorrhizal tree (Quercus macrocarpa) varied based on soil nutrient status and whether fungal community composition and diversity could explain feedback patterns. Furthermore, we inoculated Q. macrocarpa seedlings with field-sampled soils taken from five soil origins – including heterospecific and conspecific trees and an old field – which were profiled using fungal DNA metabarcoding.Results Despite finding that soils associated with different hosts harbored distinct fungal communities and that fungal communities were predictive of plant growth, we did not find any significant plant-soil feedbacks regardless of fertilization status. We did find that the growth promotive effect associated with ectomycorrhizal OTU diversity was weakened with fertilization, suggesting context-dependent relations between plant growth and a guild of fungal mutualists. Our results demonstrate that the host-specific accumulation of functionally important soil microbes is not always sufficient to drive observable plant-soil feedbacks. Our data provide support for a role for ECM fungal diversity in mediating plant growth responses, though it is unclear whether this effect is direct or indirect.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2016

Persistence of the herbicides florasulam and halauxifen-methyl in alluvial and saline alluvial soils, and their effects on microbial indicators of soil quality

In this study, the persistence of florasulam and halauxifen-methyl in combination was investigated in an alluvial (AL) and saline alluvial (SAL) soils under laboratory condition at field recommended (FR) dose (i.e. 12.76 g a.i. ha -1 ), 10 FR and 0FR (control) throughout the experiment. Effect of these herbicides on soil microbial biomass carbon (MBC), basal soil respiration (BSR), substrate induced soil respiration (SIR), hydrolysis of fluorescein diacetate (FDHA) and β-glucosidase activities was also measured under same conditions. The residues of florasulam and haluaxifen-methyl were extracted with acetonitrile using modified QuChERS method, followed by quantification using liquid chromatography-mass spectrometry (LC-MS/MS). Half-lives of florasulam and halauxifen-methyl were in the range of 12.65-16.82 days and 7.13-10.24 days in AL respectively and the same for SAL was 15.28-17.60 days and 7.25-8.88 days. Herbicide treatment inhibited MBC, BSR, SIR, and microbial metabolic quotient (qCO 2 ) up to 30 days of incubation at the applied doses in both the soils. At the end of incubation, FR treated soils became statistically at par with control. However, the FDHA and β-glucosidase activities were affected in both the soils at the applied doses of the herbicide up to 15 days. Thereafter, the FR treated soils were statistically at par with control. Finally, data revealed that, recommended dose of this herbicide formulation did not ultimately impair microbial components of the studied soils.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Effects of rows arrangement, soil management, and rainfall characteristics on water and soil losses in Italian sloping vineyards

Highlights: • GC effectiveness varies according to the type of rainfall event and row orientation. • Rows orientation along contour lines prevents runoff also when CT is adopted. • Highest runoff and soil losses depend on “long-lasting” or “intense” events. • Rainfall depth and rainfall maximum intensity count in predicting erosion rate. Erosional processes are highly affected by seasonal climatic fluctuations and soil management practices. Controlled grass cover is one of the most used soil conservation practices adopted in temperate climates, even if the protective effect of grass cover may decrease according to seasonal pattern. This technique is effective and, thus, widely adopted in the inter-rows of orchards such as olives, citrus or vineyards. This study reports the erosive events recorded in two different rain-fed hillslope vineyards with different rows orientation located in the Monferrato region, NW Italy. The study is addressed at compare the effects of different inter-row managements and rainfall characteristics on runoff and soil loss in hillslope vineyards (average slope from 15% to 35%). Rainfall, runoff and erosion variables were monitored in hydraulically bounded vineyard plots, where the inter-rows were managed with tillage and grass cover. Seventy-two erosive events were recorded in the period 1992–1996 in two vineyard plots with rows along the contour lines while 86 erosive events were recorded in two plots with rows up-and-down the slope from 2000 to 2014 (158 erosive events and four plots in total). Events were classified according to rainfall characteristics as “long-lasting”, “intense” and “normal”. In plots with rows along the contour lines, “intense” events were responsible for the highest mean soil loss in tilled plots (0.7 Mg ha{sup −1}) with very high erosion rates (12.3 Mg ha{sup −1}) observed during a single storm. In plots with rows up-and-down the slope the highest erosion rates, 21.2 and 3.4 Mg ha{sup −1}, were recorded during fall “long-lasting” events in the tilled and grass cover plots respectively. The grass cover proved to be effective in decreasing runoff and soil losses during most of the events (at least 68% and 61% of the occurrences, respectively) reducing soil losses especially during summer storms when most of the “intense” events occured. Furthermore, the results show the fundamental role of contour-slope row orientation in reducing runoff and soil losses, disregarding the inter-rows soil management that is adopted.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2023

Soil Respiration Responses to Throughfall Exclusion Are Decoupled From Changes in Soil Moisture for Four Tropical Forests, Suggesting Processes for Ecosystem Models

Abstract Climatic drying is predicted for many tropical forests yet models remain poorly parameterized for these ecosystems, hampering predictions of forest‐climate interactions. We applied an integrated model–experiment approach, parameterizing an ecosystem model with tropical forest observational data and comparing model predictions to a field drying manipulation. We hypothesized that drying suppresses soil CO 2 fluxes (i.e., respiration) in relatively dry tropical forests but increases CO 2 fluxes in wetter tropical forests by alleviating anaerobiosis. We measured soil CO 2 fluxes during wet‐dry cycles from 2015 to 2022 in four Panamanian forests that vary in rainfall and soil fertility. Measured soil CO 2 fluxes declined in the dry season and peaked in the early wet season ahead of peak soil moisture, resulting in lower soil moisture optima for respiration than previously modeled. We then parameterized the model using field data and the new moisture‐respiration response functions. The updated model predicted increased soil CO 2 fluxes with drying in wetter and fertile forests and suppressed fluxes in drier, infertile forests. In contrast to model predictions, a chronic throughfall exclusion experiment initially suppressed soil respiration across forests, with sustained suppression for four years in the wettest forest only (−28% ± 4% during the dry season). In the fertile forest, drying eventually elevated CO 2 fluxes over this period (+75% ± 28% during the late wet season). The unexpected negative drying effect in the wettest, infertile forest could have resulted from reduced vertical flushing of nutrients into soils. Including hydro‐nutrient interactions in ecosystem models could improve predictions of tropical forest‐climate feedbacks.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2017

Modeling Global Soil Carbon and Soil Microbial Carbon by Integrating Microbial Processes into the Ecosystem Process Model TRIPLEX-GHG

Microbial physiology plays a critical role in the biogeochemical cycles of the Earth system. However, most traditional soil carbon models are lacking in terms of the representation of key microbial processes that control the soil carbon response to global climate change. In this study, the improved process-based model TRIPLEX-GHG was developed by coupling it with the new MEND (Microbial-ENzyme-mediated Decomposition) model to estimate total global soil organic carbon (SOC) and global soil microbial carbon. The new model (TRIPLEX-MICROBE) shows considerable improvement over the previous version (TRIPLEX-GHG) in simulating SOC. We estimated the global soil carbon stock to be approximately 1195 Pg C, with 348 Pg C located in the high northern latitudes, which is in good agreement with the well-regarded Harmonized World Soil Database (HWSD) and the Northern Circumpolar Soil Carbon Database (NCSCD). We also estimated the global soil microbial carbon to be 21 Pg C, similar to the 23 Pg C estimated. We found that the microbial carbon quantity in the latitudinal direction showed reversions at approximately 30°N, near the equator and at 25°S. A sensitivity analysis suggested that the tundra ecosystem exhibited the highest sensitivity to a 1°C increase or decrease in temperature in terms of dissolved organic carbon (DOC), microbial biomass carbon (MBC) and mineral-associated organic carbon (MOC). Furthermore, our work represents the first step towards a new generation of ecosystem process models capable of integrating key microbial processes into soil carbon cycles.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2015

In Situ Fixation of Metal(loid)s in Contaminated Soils: A Comparison of Conventional, Opportunistic, and Engineered Soil Amendments

This study aimed to assess and compare the in vitro and in vivo bioaccessibility/bioavailability of As and Pb in a mining contaminated soil (As, 2267 mg kg –1 ; Pb, 1126 mg kg –1 ), after the addition of conventional (phosphoric acid), opportunistic [water treatment residues (WTRs)], and engineered [nano- and microscale zero valent iron (ZVI)] amendments. Phosphoric acid was the only amendment that could significantly decrease Pb bioaccessibility with respect to untreated soil (41 and 47% in the gastric phase and 2.1 and 8.1% in the intestinal phases, respectively), giving treatment effect ratios (TERs, the bioaccessibility in the amended soil divided by the bioaccessibility in the untreated soil) of 0.25 and 0.87 in the gastric and intestinal phase, respectively. The in vivo bioavailability of Pb decreased in the phosphate treatment relative to the untreated soil (6 and 24%, respectively), and also in the Fe WTR 2% (12%) and nZVI-2 (13%) treatments. The ZVI amendments caused a decrease in As bioaccessibility, with the greatest decrease in the nZVI2-treated soil (TERs of 0.59 and 0.64 in the gastric and intestinal phases, respectively). Furthermore, arsenic X-ray absorption near-edge spectroscopy analysis indicated that most of the As in the untreated soil was present as As(V) associated with Fe mineral phases, whereas in the treated soil, the proportion of arsenosiderite increased. Arsenite was present only as a minor species (3–5%) in the treated soils, with the exception of an nZVI treatment [~14% of As(III)], suggesting a partial reduction of As(V) to As(III) caused by nZVI oxidation.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2017

Association with pedogenic iron and aluminum: effects on soil organic carbon storage and stability in four temperate forest soils

Soil organic carbon (SOC) can be stabilized via association with iron (Fe) and aluminum (Al) minerals. Fe and Al can be strong predictors of SOC storage and turnover in soils with relatively high extractable metals content and moderately acidic to circumneutral pH. Here we test whether pedogenic Fe and Al influence SOC content and turnover in soils with low Fe and Al content and acidic pH. In soils from four sites spanning three soil orders, we quantified the amount of Fe and Al in operationally-defined poorly crystalline and organically-complexed phases using selective chemical dissolution applied to the soil fraction containing mineral-associated carbon. We evaluated the correlations of Fe and Al concentrations, mean annual precipitation (MAP), mean annual temperature (MAT), and pH with SOC content and 14C-based turnover times. We found that poorly crystalline Fe and Al content predicted SOC turnover times (p < 0.0001) consistent with findings of previous studies, while organically-complexed Fe and Al content was a better predictor of SOC concentration (p < 0.0001). Greater site-level MAP (p < 0.0001) and colder site-level MAT (p < 0.0001) were correlated with longer SOC turnover times but were not correlated with SOC content. Our results suggest that poorly crystalline Fe and Al effectively slow the turnover of SOC in these acidic soils, even when their combined content in the soil is less than 2% by mass. However, in the strongly acidic Spodosol, organo-metal complexes tended to be less stable resulting in a more actively cycling mineral-associated SOC pool.

14C↗
DOE OSTI2017

Importance of lateral flux and its percolation depth on organic carbon export in Arctic tundra soil: Implications from a soil leaching experiment

Temperature rise in the Arctic is causing deepening of active layers and resulting in the mobilization of deep permafrost dissolved organic matter (DOM). However, the mechanisms of DOM mobilization from Arctic soils, especially upper soil horizons which are drained most frequently through a year, are poorly understood. Here, we conducted a short-term leaching experiment on surface and deep organic active layer soils, from the Yukon River basin, to examine the effects of DOM transport on bulk and molecular characteristics. We report our data showed a net release of DOM from surface soils equal to an average of 5% of soil carbon. Conversely, deep soils percolated with surface leachates retained up to 27% of bulk DOM-while releasing fluorescent components (up to 107%), indicating selective release of aromatic components (e.g. lignin, tannin), while retaining non-chromophoric components, as supported by spectrofluorometric and ultra high resolution mass spectroscopic techniques. Our findings highlight the importance of the lateral flux of DOM on ecosystem carbon balance as well as processing of DOM transport through organic active layer soils en route to rivers and streams. This work also suggests the potential role of leachate export as an important mechanism of C losses from Arctic soils, in comparison with the more traditional pathway from soil to atmosphere in a warming Arctic.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2018

The path from litter to soil: Insights into soil C cycling from long-term input manipulation and high-resolution mass spectrometry

The pathways carbon (C) takes from plant litter to soil organic matter (SOM) underlies our understanding of how soil C stocks and microbial decomposition will respond to climate change, and determining whether natural soil C sinks can be enhanced to offset potential losses. Long-term ecosystem-scale litter manipulations and innovations in the molecular characterization of SOM provide a unique opportunity to explore these dynamics. We incubated soils from a 20-year litter-input experiment for 525 days and asked how litter quantity and source (i.e., roots versus aboveground litter) affected soil C cycling, including microbial function and the size and molecular composition of C pools defined by degree of mineral association. Input exclusion led to a 30% loss of soil C, attributable largely to the non-mineral-associated C fraction, and was accompanied by declines in soil C decomposition. The absence of roots led to a shift in the microbial catabolic profile, though there was no evidence that root litter was preferentially stabilized. Carbon did not accumulate under litter addition. However, direct examination of the finest mineral fraction with Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) revealed dramatic changes to the chemical composition of carbon. In particular, lipid content increased proportionally with input addition, and was subsequently mineralized during incubation, indicating that this apparently stable fraction is metabolically active. Moreover, non-metric dimensional scaling (NMS) showed that both litter treatments and incubation caused the molecular composition of SOM to diverge, and explained 79% of the variance in soil respiration. We conclude that the path from litter to soil is more complex than previously thought and mineral-associated SOM thought to be stable may be microbially available.

Reynolds, L L.↗
DOE OSTI2019

Bound and mobile soil water isotope ratios are affected by soil texture and mineralogy, whereas extraction method influences their measurement

Questions persist about interpreting isotope ratios of bound and mobile soil water pools, particularly relative to clay content and extraction conditions. Interactions between pools and resulting extracted water isotope composition are presumably related to soil texture, yet few studies have manipulated the bound pool to understand its influence on soil water processes. Using a series of drying and spiking experiments, we effectively labelled bound and mobile water pools in soils with varying clay content. Soils were first vacuum dried to remove residual water, which was then replaced with heavy isotope-enriched water prior to oven drying and spiking with heavy isotope-depleted water. Water was extracted via centrifugation or cryogenic vacuum distillation (at four temperatures) and analysed for oxygen and hydrogen isotope ratios via isotope ratio mass spectrometry. Water from centrifuged samples fell along a mixing line between the two added waters but was more enriched in heavy isotopes than the depleted label, demonstrating that despite oven drying, a residual pool remains and mixes with the mobile water. Soils with higher clay + silt content appeared to have a larger bound pool. Water from vacuum distillation samples have a significant temperature effect, with high temperature extractions yielding progressively more heavy isotope-enriched values, suggesting that Rayleigh fractionation occurred at low temperatures in the vacuum line. By distinctly labelling bound and mobile soil water pools, we detected interactions between the two that were dependent on soil texture. Although neither extraction method appeared to completely extract the combined bound and mobile (total water) pool, centrifugation and high temperature cryogenic vacuum distillations were comparable for both δ 2 H and δ 18 O of soil water isotope ratios.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2015

Modeling pulsed soil respiration in an African savanna ecosystem

Savannas cover 60% of the African continent and play an important role in the global carbon (C) emissions from fire and land use. To better characterize the biophysical controls over soil respiration in these settings, half-hourly observations of volumetric soil-water content, temperature, and the concentration of carbon dioxide (CO2) at different soil depths were continually measured from 2005 to 2007 under trees ("sub-canopy") and between trees ("inter-canopy") in a savanna vegetation near Skukuza, Kruger National Park, South Africa. The measured soil climate and CO2 concentration data were assimilated into a process-based model that estimates the CO2 production and flux with coupled dynamics of dissolved organic C (DOC) and microbial biomass C. Our results show that temporal and spatial variations in CO2 flux were strongly influenced by precipitation and vegetation cover, with two times greater CO2 flux in the subcanopy plots (similar to 2421 g CO2 m(-2) yr(-1)) than in the inter-canopy plots (similar to 1290 g CO2 m(-2) yr(-1)). Precipitation influenced soil respiration by changing soil temperature and moisture; however, our modeling analysis suggests that the pulsed response of soil respiration to precipitation events (known as "Birch effect") is a key control on soil fluxes at this site. At this site, "Birch effect" contributed to approximately 50% and 65% of heterotrophic respiration or 20% and 39% of soil respiration in the sub-canopy and inter-canopy plots, respectively. These results suggest that pulsed response of respiration to precipitation events is an important component of the C cycle of savannas and should be considered in both measurement and modeling studies of carbon exchange in similar ecosystems. (C) 2014 Elsevier B.V. All rights reserved.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2020

Collar Properties and Measurement Time Confer Minimal Bias Overall on Annual Soil Respiration Estimates in a Global Database

Abstract Measuring the soil‐to‐atmosphere carbon dioxide (CO 2 ) flux (soil respiration, R S ) is important to understanding terrestrial carbon balance and to forecasting climate change. Such measurements are frequently made using measurement collars permanently inserted into the soil surface. However, differences in measurement duration and frequency, as well as collar properties, may lead to biases in the estimation of annual R S . Using a newly updated global R S database (SRDB‐V5), we investigated the annual R S bias associated with five methodological factors: collar height, collar coverage area, collar insertion depth, measurement duration, and measurement frequency. We found that annual R S was negatively correlated with collar insertion depth, consistent with the idea that collar insertion cuts roots and thus reduces R S . Annual R S was also negatively related with collar height and collar coverage area, perhaps because uniform head‐space mixing is difficult to achieve in larger volume chambers; however, these effects were quantitatively small (bias of ~2% to 10% of mean R S ). We found no correlation of measurement duration or measurement frequency with annual R S . These findings suggest that variation in R S methodology generally introduces minimal bias overall. Therefore, compilations of minimally adjusted annual R S measurements provide a reliable resource for synthesis studies, global annual R S modeling, and investigation of how soil carbon responds to climate change.

Jian, Jinshi↗