VTechWorks Repository :: Browsing by Author "Shang, Chao"

Browsing by Author "Shang, Chao"

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Biosynthesis of Steroidal Glycoakaloids in Solanum chacoense Bitter
Mweetwa, Alice Mutiti (Virginia Tech, 2009-07-24)
Steroidal glycoalkaloids (SGAs) are secondary metabolites produced by approximately 350 species in the Solanaceae family. SGAs are reported to be important for pest resistance and flavor enhancement at low concentrations but are toxic to humans and other mammals at high concentrations. Studies on sterol / SGA biosynthesis have implicated squalene synthase as a key regulatory enzyme because it catalyzes an irreversible step from the mevalonic acid pathway. However, the regulatory mechanisms of squalene synthase are not yet known. A study was conducted to elucidate the distribution pattern of SGAs and to clone the squalene synthase gene in order to determine a relationship between SGAs and gene expression levels. Solanum chacoense, a wild potato species was used as a model plant from which tissues were harvested at specified developmental stages and analyzed for SGA content. The results from the SGA analysis suggest a qualitative and quantitative tissue- and age-dependent accumulation of SGAs. Regenerative tissues such as, axiliary shoots, flowers and floral buds had the highest levels of 88, 49 and 63 Âµmole/g DW, respectively. The roots, stems and tubers showed the lowest amounts of SGAs of 1 to 8, 5 to 15 and 7 to 15 Âµmole/g DW, respectively. Stolons and tubers accumulated higher amounts of α-chaconine (59 to 67%) than α-solanine (61 to 64%) at all developmental stages analyzed. On the other hand, in young expanding, fully expanded, and old senescing leaves where leptine and leptinines tend to dominate, α-solanine and α-chaconine together accounted for only 8 to 15%, 7 to 15%, and 8 to 45%, respectively. Plant organs that showed the highest biosynthetic activity for SGA production also had high levels of transcripts coding for genes of isoprenoid biosynthesis. The results from the cloning and characterization of squalene synthase suggest that the cloned cDNA fragment is a putative S. chacoense squalene synthase gene with an open reading frame / predicted protein precursor of 411 amino acids. The cloned cDNA has high similarity (68-100%) to known plant squalene synthase genes and contains six deduced peptide domains observed in other species. The 3â untranslated regions of floral buds, young leaves (early vegetative stage), and fully expanded leaves (anthesis) were different in length with, 249, 335, and 202 nucleotides, respectively. The Southern blot analysis suggests a single copy gene although the existence of a gene family cannot be ruled out.
Development and Validation of a UPLC-MS/MS Method to Monitor Cephapirin Excretion in Dairy Cows following Intramammary Infusion
Ray, Partha; Knowlton, Katharine F.; Shang, Chao; Xia, Kang (PLOS, 2014-11-06)
Cephapirin, a cephalosporin antibiotic, is used by the majority of dairy farms in the US. Fecal and urinary excretion of cephapirin could introduce this compound into the environment when manure is land applied as fertilizer, and may cause development of bacterial resistance to antibiotics critical for human health. The environmental loading of cephapirin by the livestock industry remains un-assessed, largely due to a lack of appropriate analytical methods. Therefore, this study aimed to develop and validate a cephapirin quantification method to capture the temporal pattern of cephapirin excretion in dairy cows following intramammary infusion. The method includes an extraction with phosphate buffer and methanol, solid-phase extraction (SPE) clean-up, and quantification using ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The LOQ values of the developed method were 4.02 µg kg−1 and 0.96 µg L−1 for feces and urine, respectively. This robust method recovered >60% and >80% cephapirin from spiked blank fecal and urine samples, respectively, with acceptable intra- and inter-day variation (<10%). Using this method, we detected trace amounts (µg kg−1) of cephapirin in dairy cow feces, and cephapirin in urine was detected at very high concentrations (133 to 480 µg L−1). Cephapirin was primarily excreted via urine and its urinary excretion was influenced by day (P = 0.03). Peak excretion (2.69 mg) was on day 1 following intramammary infusion and decreased sharply thereafter (0.19, 0.19, 0.08, and 0.17 mg on day 2, 3, 4, and 5, respectively) reflecting a quadratic pattern of excretion (Quadratic: P = 0.03). The described method for quantification of cephapirin in bovine feces and urine is sensitive, accurate, and robust and allowed to monitor the pattern of cephapirin excretion in dairy cows. This data will help develop manure segregation and treatment methods to minimize the risk of antibiotic loading to the environment from dairy farms.
Development of Breeder-Friendly KASP Markers for Low Concentration of Kunitz Trypsin Inhibitor in Soybean Seeds
Rosso, M. Luciana; Shang, Chao; Song, Qijian; Escamilla, Diana M.; Gillenwater, Jay; Zhang, Bo (MDPI, 2021-03-06)
Trypsin inhibitors (TI), a common anti-nutritional factor in soybean, prevent animals’ protein digestibility reducing animal growth performance. No commercial soybean cultivars with low or null concentration of TI are available. The availability of a high throughput genotyping assay will be beneficial to incorporate the low TI trait into elite breeding lines. The aim of this study is to develop and validate a breeder friendly Kompetitive Allele Specific PCR (KASP) assay linked to low Kunitz trypsin inhibitor (KTI) in soybean seeds. A total of 200 F_3:5 lines derived from PI 547656 (low KTI) X Glenn (normal KTI) were genotyped using the BARCSoySNP6K_v2 Beadchip. F_3:4 and F_3:5 lines were grown in Blacksburg and Orange, Virginia in three years, respectively, and were measured for KTI content using a quantitative HPLC method. We identified three SNP markers tightly linked to the major QTL associated to low KTI in the mapping population. Based on these SNPs, we developed and validated the KASP assays in a set of 93 diverse germplasm accessions. The marker Gm08_44814503 has 86% selection efficiency for the accessions with low KTI and could be used in marker assisted breeding to facilitate the incorporation of low KTI content in soybean seeds.
Digestion of inositol phosphates by dairy cows: Method development and application
Ray, Partha Pratim (Virginia Tech, 2012-05-02)
Successful implementation of dietary P management strategies demand improved understanding of P digestion dynamics in ruminants and this is not possible without a reliable and accurate phytate (Pp) quantification method. The objective of the first study was to develop a robust, accurate, and sensitive method to extract and quantify phytate in feeds, ruminant digesta and feces. Clean-up procedures were developed for acid and alkaline extracts of feed, ruminant digesta and feces and clarified extracts were analyzed for Pp using high performance ion chromatography (HPIC). The quantified Pp in acid and alkaline extracts was comparable for feed but alkaline extraction yielded greater estimates of Pp content for digesta and feces than did acid extraction. Extract clean-up procedures successfully removed sample matrix interferences making alkaline extraction compatible with HPIC. The developed method was applied to investigate the disappearance of Pp from the large intestine of dairy heifers. Eight ruminally- and ileally-cannulated crossbred dairy heifers were used and each heifer was infused ileally with 0, 5, 15, or 25 g/d Pp and total fecal collection was conducted. On average 15% of total Pp entering the large intestine was degraded but the amount of infused Pp did not influence the degradability of Pp. Net absorption of P from the large intestine was observed. A feeding trial was conducted to investigate the effect of dietary Pp supply on ruminal and post-ruminal Pp digestion. Six ruminally-and ileally-cannulated crossbred lactating cows were used and dietary treatments were low (0.10% Pp), medium (0.18% Pp), and high (0.29% Pp) Pp, and a high inorganic P (Pi; 0.11% Pp; same total P content as high Pp). Ruminal Pp digestibility increased linearly with dietary Pp. As in the infusion study, net disappearance of Pp from the large intestine was only 16% of total Pp entering the large intestine and not influenced by dietary Pp. Fecal P excretion increased linearly with increasing dietary Pp but was not affected by form of dietary P. In lactating cows Pp digestibility was not affected by dietary Pp and fecal P excretion was regulated by total dietary P rather than by form of dietary P.
Effects of Biosolids on Carbon Sequestration and Nitrogen Cycling
Li, Jinling (Virginia Tech, 2013-01-07)
Land application of biosolids has been demonstrated to improve nutrient availability (mainly N and P) and improve organic matter in soils, but the effects of biosolids on C sequestration and N cycling in the Mid-Atlantic region is not well understood. The objectives were: 1) to investigate soil C sequestration at sites with a long-term history of biosolids either in repeated application or single large application; 2) to characterize and compare soil C chemistry using advanced 13C nuclear magnetic resonance (NMR) and C (1s) near edge x-ray absorption fine structure (NEXAFS) spectroscopic techniques; and 3) to compare biosolids types and tillage practices on short-term N availability in the Coastal Plain soils. Biosolids led to C accumulation in the soil surface (< 15 cm) after long-time application in both Piedmont and Coastal Plain soils. The C saturation phenomenon occurred in Coastal Plain soils, thus additional soil C accumulation was not achieved by increasing C inputs from biosolids to the Coastal Plain. Soil organic C from profiles in the field sites was not different at depths below the plow layer (15-60 cm). The quantitative NMR analyses concluded that O-alkyl C was the dominant form in the particulate organic matter (POM), followed by aromatic C, alkyl C, COO/N-C=O, aromatic C-O, OCH3 / NCH and ketones and aldehydes. The aliphatic C and aromatic C were enriched but the O-alkyl C was decreased in the biosolids-amended soils. The changes indicated that the biosolids-derived soil C was more decomposed and, thus, more stable than the control. The NEXAFS spectra showed that O-alkyl C was the dominant form in the POM extracted from biosolids-amended soils, followed by aromatic C, alkyl C, carboxylic C and phenolic C groups. These results were similar to those from NMR analysis. The regression and correlation analyses of C functional groups in the POM between NEXAFS and NMR indicated that both techniques had good sensitivity for the characterization of C from biosolids-amended soils. To evaluate short-term biosolids N availability, a three-year field study to investigate the effects of lime-stabilized (LS) and anaerobically digested (AD) biosolids on N availability in a corn-soybean rotation under conventional tillage and no-tillage practices was set up in 2009-2011. Results showed that both LS and AD biosolids increased spring soil nitrate N, plant tissue N at silking, post-season corn stalk nitrate N, grain yield, and soil total N by the end of the growing season. The same factors used to calculate plant available N for incorporated biosolids can be used on biosolids applied to no-till systems in coarse-textured soils. All these results indicated that the application of biosolids affects the long-term quantification and qualification of soil organic C and also improve short-term N availability in the Mid-Atlantic region.
Effects of diet on phosphorus digestion in dairy cattle
Yang, Tzu-Hsuan (Virginia Tech, 2006-08-08)
Two studies were conducted to evaluate the effects of diet on phosphorus (P) digestion in dairy cattle. The objective of the first study was to evaluate the effects of forage and non-fiber carbohydrate (NFC) content on total P (TP) and inositol phosphates-P (IPs-P) digestion. Samples of feed, duodenal digesta and feces from a previously conducted study were analyzed for TP and IPs-P. In this study, eight lactating Holstein cows were fed diets containing either 60 or 35% forage and either 30 or 40% NFC in a 2 × 2 factorial with replicated 4 × 4 Latin square design. Dietary TP content (% DM) was 0.35, 0.36, 0.36, 0.36 and dietary IPs-P content (%DM) was 0.08, 0.13, 0.06, 0.11 for diets with forage: NFC ratio 35:30, 35:40, 60:30, and 60:40, respectively. Increasing dietary forage content decreased IPs-P and TP intake, fecal TP excretion, and total tract IPs-P digestibility (72.4 vs. 61.4%). Fecal IPs-P excretion tended to decrease as increasing forage content. Duodenal IPs-P and TP flow and apparent TP digestibility were unaffected by forage content. Increasing dietary NFC content increased IPs-P and TP intake, duodenal IPs-P flow, fecal IPs-P excretion, total tract IPs-P digestibility (61.4 vs. 72.4%), and apparent TP digestibility (32.8 vs. 41.6%). Dietary forage and NFC content affected IPs-P and TP digestion. The second study was to evaluate the effects of increasing dietary beet pulp (BP) content to replace high moisture corn (HMC) on ruminal and post-ruminal digestion of TP and IPs-P. Eight lactating Holstein cows were fed diets containing 0, 6.1, 12.1 or 24.3% BP in a replicated 4 × 4 Latin square design. Samples of rumen contents, duodenal digesta, and feces from this previously conducted study were analyzed for TP and IPs-P content. Linear and quadratic effects of BP content were analyzed using Proc Mixed of SAS. Dietary TP and IPs-P content were reduced linearly with increasing BP (0.59, 0.58, 0.57, 0.56% TP and 0.15, 0.14, 0.13, 0.11% IPs-P). Intake, ruminal content, and rumen pool size of TP decreased with increasing BP content. Digestion of TP and duodenal flow and fecal excretion of IPs-P and TP were not affected. With increasing dietary BP content, IPs-P intake was reduced, ruminal IPs-P pool size was reduced, and rumen turnover time (h) of IPs-P was increased. Apparent ruminal IPs-P digestibility (36.5, 31.8, 24.6, 13.6 %) and apparent total tract IPs-P digestibility (85.3, 82.7, 82.1, 79.1%) decreased linearly with increasing BP. Fecal excretion of IPs-P averaged 5.2 g/d. Replacing HMC with BP reduced digestion of IPs-P. The majority of IPs-P disappearance occurred post-ruminally. In conclusion, dietary BP, forage, and NFC content affected IPs-P digestion in dairy cows.
Environmental Fate of Animal Manure-associated Antibiotics and Seed-coated Pesticide in Soils
Cushman, Julia Ananieff (Virginia Tech, 2017-02-20)
There is growing concern over the environmental and human health impacts of chemical contaminants in agricultural systems. The environmental persistence of veterinary antibiotics applied to agricultural fields during manure fertilization could lead to increased antibiotic resistance. New generation, neonicotinoid pesticides pose a threat to aquatic ecosystem health due high water mobility and increased potential for non-target exposure. The objectives of this research were to develop a sensitive, analytical method for quantification of pirlimycin (PLY) in soils to be used in field research and determine the ability of second-generation neonicotinoids to move through soil when applied as a seed coating using a greenhouse study. Liquid-solid extraction of PLY from soil using (1:6, v/v) ammonium hydroxide/methylene chloride produced good PLY recovery (67-140%). Liquid-chromatography coupled with tandem mass-spectrometry for instrumental analysis provided good sensitivity with minimal matrix interferences. The mass balance distribution of neonicotinoid treatment coated onto corn seeds was determined in plant and soil samples for a single pot after 3 weeks of growth. A large percent (83-87%) of initial pesticide coating applied to seed was un-detected in plant in soil. Of the detected portion of neonicotinoid treatment, between 96-98% was observed to move out into the soil. This suggests the potential for long-range transport of seed-coated neonicotinoids.
Fe3 +-saturated montmorillonite effectively deactivates bacteria in wastewater
Qin, Chao; Chen, Chaoqi; Shang, Chao; Xia, Kang (Elsevier, 2018)
Existing water disinfection practices often produce harmful disinfection byproducts. The antibacterial activity of Fe3 +-saturated montmorillonite was investigated mechanistically using municipal wastewater effluents. Bacterial deactivation efficiency (bacteria viability loss) was 92 ± 0.64% when a secondary wastewater effluent was mixed with Fe3 +-saturated montmorillonite for 30 min, and further enhanced to 97 ± 0.61% after 4 h. This deactivation efficiency was similar to that when the same effluent was UV-disinfected before it exited a wastewater treatment plant. Comparing to the secondary wastewater effluent, the bacteria deactivation efficiency was lower when the primary wastewater effluent was exposed to the same dose of Fe3 +-saturated montmorillonite, reaching 29 ± 18% at 30 min and 76 ± 1.7% at 4 h. Higher than 90% bacterial deactivation efficiency was achieved when the ratio between wastewater bacteria population and weight of Fe3 +-saturated montmorillonite was at < 2 × 103 CFU/mg. Furthermore, 99.6–99.9% of total coliforms, E. coli, and enterococci in a secondary wastewater effluent was deactivated when the water was exposed to Fe3 +-saturated montmorillonite for 1 h. Bacterial colony count results coupled with the live/dead fluorescent staining assay observation suggested that Fe3 +-saturated montmorillonite deactivated bacteria in wastewater through two possible stages: electrostatic sorption of bacterial cells to the surfaces of Fe3 +-saturated montmorillonite, followed by bacterial deactivation due to mineral surface-catalyzed bacterial cell membrane disruption by the surface sorbed Fe3 +. Freeze-drying the recycled Fe3 +-saturated montmorillonite after each usage resulted in 82 ± 0.51% bacterial deactivation efficiency even after its fourth consecutive use. This study demonstrated the promising potential of Fe3 +-saturated montmorillonite to be used in applications from small scale point-of-use drinking water treatment devices to large scale drinking and wastewater treatment facilities.
Genome-Wide Association Study and Genomic Selection for Proteinogenic Methionine in Soybean Seeds
Singer, William; Shea, Zachary; Yu, Dajun; Huang, Haibo; Mian, M.A. Rouf; Shang, Chao; Rosso, Maria L.; Song, Qijan J.; Zhang, Bo (Frontiers, 2022-04-25)
Soybean [Glycine max (L.) Merr.] seeds have an amino acid profile that provides excellent viability as a food and feed protein source. However, low concentrations of an essential amino acid, methionine, limit the nutritional utility of soybean protein. The objectives of this study were to identify genomic associations and evaluate the potential for genomic selection (GS) for methionine content in soybean seeds. We performed a genome-wide association study (GWAS) that utilized 311 soybean accessions from maturity groups IV and V grown in three locations in 2018 and 2019. A total of 35,570 single nucleotide polymorphisms (SNPs) were used to identify genomic associations with proteinogenic methionine content that was quantified by high-performance liquid chromatography (HPLC). Across four environments, 23 novel SNPs were identified as being associated with methionine content. The strongest associations were found on chromosomes 3 (ss715586112, ss715586120, ss715586126, ss715586203, and ss715586204), 8 (ss715599541 and ss715599547) and 16 (ss715625009). Several gene models were recognized within proximity to these SNPs, such as a leucine-rich repeat protein kinase and a serine/threonine protein kinase. Identification of these linked SNPs should help soybean breeders to improve protein quality in soybean seeds. GS was evaluated using k-fold cross validation within each environment with two SNP sets, the complete 35,570 set and a subset of 248 SNPs determined to be associated with methionine through GWAS. Average prediction accuracy (r2) was highest using the SNP subset ranging from 0.45 to 0.62, which was a significant improvement from the complete set accuracy that ranged from 0.03 to 0.27. This indicated that GS utilizing a significant subset of SNPs may be a viable tool for soybean breeders seeking to improve methionine content.
Impact of Manure Management Practices on the Environmental Fate of Antibiotics in Manure-Applied Fields
Le, Hanh Thi Van (Virginia Tech, 2019-09-10)
Antibiotics and antibiotic resistance genes from animal manure applied to soil as fertilizer are now among the most concerned contaminants in soil. The widespread use of antibiotics in livestock might amplify the risk of developing antibiotic resistance, causing once treatable diseases to turn deadly. The World Health Organization declared antibiotic resistance as "one of the biggest threats to global health, food security, and development". The goal of this dissertation was to develop best manure management practices by understanding the behavior of manure-associated antibiotics in manure, water, and soil. In particular, my research focused on the effects of manure application methods, on-site manure treatment methods, manure application seasons, and manure-rainfall time gaps on antibiotic surface runoff losses, antibiotic distribution and movement in soil, antibiotic dissipation in soil, and development of antibiotic resistance. Rainfall simulation field-scale and soil incubation lab studies were combined to find the best manure management practices. My research has shown for the first time that using the manure soil subsurface injection method, especially during spring application season due to moist soil, applying manure at least 3 days before a subsequent rainfall, and using composted manure, can significantly reduce the quantity of antibiotic loss with runoff from manure-applied fields to the surrounding environment. The majority of applied antibiotics remained in soil. All antibiotics showed a similar dissipation pattern with fastest kinetics during the first 14 d before slowing down. The effect of two manure application methods on antibiotic dissipation kinetics varied with different antibiotics. Although the half-life of tested antibiotics in soil was short (<21 days), some remained detectable even at 6 months after a single manure application. Results also showed that compared to the surface application, the subsurface injection slits acted as a "hot zone" with a higher amount of antibiotics, manure microbes, and antibiotic resistance. The results provide information for policy makers, manure managers, and farmers to develop better manure management practices that can use manure as fertilizer while minimizing the spread of antibiotics to surrounding water, soil, and plants.
Improving estimations of phosphorus bioavailability for lactating dairy cows
Jarrett, Jamie Pearl (Virginia Tech, 2011-10-14)
Phosphorus (P) is an instrumental nutrient in numerous physiological processes, but can have detrimental environmental impact if fed in excess. Increased P intake in dairy cows leads to increased fecal excretion of P and a reduction in efficiency of use. Variability in P concentration or availability in feedstuffs can exacerbate P excretion. To investigate variability in P between and within feedstuffs, 170 feed samples (forages, concentrates, and by-products), were collected from across the U.S., classified by region fed, and analyzed for total P, inorganic P, and phytate. Forages contained a greater proportion of P in the inorganic form and less total P and phytate as compared to concentrates and by-products. The majority of total P (71.2, 81.8, and 81.9% of total P in forages, concentrates, and by-products, respectively) was associated with inorganic P and phytate. The enzyme phytase has been used successfully in swine and poultry nutrition, as a feed additive, to increase available P and reduce the need for supplemental inorganic P. An experiment was conducted to investigate the effect of phytase use and forage particle length, using a 2 x 2 factorial, on P availability in lactating dairy cows. Total P intake of the four diets was similar (P > 0.15). Total tract digestibility of total P tended (P < 0.10) to be reduced and total P excretion was increased (P < 0.05) with phytase supplementation. Milk fat yield, protein yield, 3.5% FCM, and ECM were increased (P < 0.05) with addition of exogenous phytase to the diet. This indicates that phytate may contain some anti-nutritional factors that reduce availability in other nutrients used for milk production. Variation in P compounds between feeds, and variation in P digestion and production performance with exogenous phytase suggests opportunity for improvement in prediction of P availability from feeds for lactating cows.
In vivo and modeling approaches to improve prediction of phosphorus availability in ruminants
Feng, Xin (Virginia Tech, 2015-06-04)
Improving prediction of P availability necessitates understanding of P digestion and absorption mechanism in ruminants. Greater knowledge of the interaction of P with other nutrients and the utilization of dietary P in the digestive tract will improve our ability to optimize P feeding and reduce P runoff in agricultural areas. In vivo experiments were performed and the data were used to reparamterize a model regarding P digestion and metabolism. The interaction of P and iron was investigated in lactating dairy cows by infusing 0, 200, 500, or 1250 mg/d Fe (equivalent to 0, 2, 5, or 12.5 mg Fe/L in drinking water) in the form of ferrous lactate solution into the abomasum of lactating cows. Phosphorus absorption was not negatively influenced by abomasally infused ferrous lactate, and the highest infusion (1250 mg Fe/d) approximates a drinking water iron content far above that found in most samples from the field. In the second study the effects of dietary P intake on intestinal P absorption was evaluated in eight growing Holstein steers fitted with permanent duodenal and ileal cannulas. Diets varying in P content (0.15%, 0.27%, 0.36% and 0.45%, DM basis) were fed , and increasing P intake increased the quantity of P absorbed from the small intestine linearly without affecting the absorption efficiency (mean = 59.6%). Only a small portion of P absorption occurred in large intestine and this was not affected by dietary P concentration. An absence of change of salivary P secretion at low dietary P suggested rumen function was prioritized during short-term P deficiency. Finally the data from these experiments along with four other studies were used to parameterize the P digestion and metabolism model of Hill et al. (2008) to provide a better understanding of the digestion and metabolism of P fractions in cattle. The data used were adequate to parameterize the digestive elements of the model with good precision, and the model structure appears to be appropriate with no significant mean or slope bias. The resulting model could be used to derive P bio-availabilities of commonly used feedstuffs in cattle production. Although the model explained the data used with no apparent bias, this does not guarantee that the model parameters are valid for all conditions. Additional data are needed to evaluate this model in a wider range of scenarios.
Measurement of Phytase Activity in a Clymer Forest Soil Using the TInsP5 Probe
Huang, Zirou (Virginia Tech, 2009-07-20)
Measurement of soil phytase activity (PA) and delineation of the impact of this important phosphomonoesterase on the P-cycling process in soil and sediments suffer from the lack of a reliable assay. A method for measuring PA in soil that promises to be accurate and reliable has been recently published. The method involves the use of a novel chromophoric analog of phytic acid, referred to as T(tethered)InsP5 (5-O-[6-(benzoylamino)hexyl]-D-myo-inositol-1,2,3,4,6-pentakisphosphate). This study was conducted to measure PA in a Clymer forest soil, which contained over twice the amount of soil organic C as previously tested soils, using the TInsP5 PA assay. This investigation specifically addresses: (1) the development of a soil dilution technique for determining maximal PA, (2) identification of previously unsubstantiated soil-produced dephosphorylated intermediate probe species, (3) the impact of increasing assay buffer pH on soil PA and (4) testing stability of the probe's amide bond in a highly (bio)active forest soil. PA assays were conducted by measuring dephosphorylation of TInsP5 in citrate-acetate buffered (pH 4.2) active and autoclaved (Control) soil suspensions. Phosphorylated probe intermediates (i.e., TInsP4, TInsP3, TInsP2 and TInsP1) and T-myo-inositol were extracted from samples of soil suspension following incubation. Probe species were quantified using reversed phase high-performance liquid chromatography (RPHPLC) with UV detection. PA was calculated based on a mass balance approach. A soil dilution technique was developed to address the challenge of determining maximal PA in soils containing higher organic matter content. In the initial report on use of the TInsP5 method for measuring PA in soil, two "soil-generated" UV-adsorbing compounds (designated Y and Z) were observed, but never confirmed as probe species. The experimental evidence presented in this report supports inclusion of compound Y as a phosphorylated probe intermediate species (i.e. TInsPy), based primarily on its UV adsorption spectra (diode-array detection analysis). Compound Z could not be substantiated as a probe species based on the evidence presented in this study. PA of Claymer forest soil decreased with an increase in assay buffer pH. Further, the probe's amide bond linkage was stable in a forest soil exhibiting high PA.
Mineral Surface Catalyzed Polymerization Of Estrogen And Microbial Deactivation By Fe3+-Saturated Montmorillonite: A Potentially Low Cost Material For Water Decontamination
Qin, Chao (Virginia Tech, 2017-02-07)
With advantages of high cation exchange capacity, swelling-shrinking property and large specific surface area, monmtorillonite is chosen as a carrier and modified with Fe3+ saturation for estrogen decontamination. 17β-Estradiol (βE2) has highest estrogenic activity among estrogens and is selected as representative compound. Rapid βE2 transformation in the presence of Fe3+ - saturated montmorillonite in aqueous system was observed and βE2 oligomers were the major βE2 transformation products. About 98% of βE2 were transformed into oligomers which are >107 times less water-soluble than βE2 and therefore are much less bioavailable and mobile. Fe3+ -saturated montmorillonite catalysis achieved highest βE2 removal efficiency at neutral solution pH and higher temperature. Common cations did not have impact on the reaction efficiency. Dissolved organic matter slightly reduced βE2 removal efficiency. Regardless of wastewater source, ~40% βE2 removal efficiency was achieved for wastewater effluents when they were exposed to same dosage of Fe3+ -saturated montmorillonite as that for simple water systems which achieved ~83% removal efficiency. For real wastewater that contained higher organic matter, higher dosage of Fe3+ -saturated montmorillonite would be needed to create available reaction sites for βE2. This thesis also reports that Fe3+ -saturated montmorillonite effectively deactivate wastewater microorganisms. Microbial deactivation rate was 92±0.6% when secondary wastewater effluent was mixed with Fe3+ -saturated montmorillonite at 35 mg/mL for 30 min, and further increased to 97±0.6% after 4-h exposure. Freeze-drying Fe3+ -saturated montmorillonite iii after each usage resulted in 82±0.5% microbial deactivation efficiency even after fourth consecutive use. For convenient application, Fe3+ -saturated montmorillonite was further impregnated into filter paper through wet-end addition and formed uniformly impregnated paper. Scanning electron microscopy (SEM) imaging showed Fe3+ -saturated montmorillonite was evenly dispersed over cellulose fiber surface. When filtering 50 mL and 200 mL water spiked with live Escherichia coli (E. coli) cells at 3.67×108 CFU/mL, Fe3+ -saturated montmorillonite impregnated paper with 50% mineral weight loading deactivated E. coli with 99% and 77%, respectively. Dielectrophoresis and impedance analysis of filtrate confirmed that the deactivated E. coli passing through Fe3+ -saturated montmorillonite paper did not have trapping response due to higher membrane permeability and conductivity. The results demonstrate feasibility of using Fe3+ -saturated montmorillonite impregnated paper for convenient point-of-use drinking water disinfection.
The Occurrence and Fate of Steroid Hormones from Manure Amended Agriculture Fields
Sosienski, Theresa Ann (Virginia Tech, 2017-07-14)
Hormones are endocrine disrupting compounds, which have been shown to alter the sexual development of aquatic organisms. Animal manure applications to agricultural fields for nutrient management can be a source of environmental hormones. This dissertation investigates the occurrence of hormones in fields applied with various manures and their adjacent streams, as well as the effect of manure application technologies on the fate of hormones in soils, sediments, and runoff. A total of 11 hormone compounds were studied. All studied analytes were quantified using liquid chromatography and triple-quadrupole mass spectrometry following various sample extraction and clean-up strategies. The spatial and temporal distribution of manure-associated hormones in a manure surface applied agricultural field and adjacent stream was studied at time points up to 7.5 months after a routine manure application. Hormones were detected mainly in the top 0-5cm soils. Significantly higher levels of hormones were found in the drystack applied area of the field when compared to dairy manure slurry applied portion. New technologies for the subsurface application of poultry litter show promise as a tool to reduce the transportation of environmental hormones in surface runoff. Once adequate sampling protocols were established; it was determined that subsurface injection of both dairy manure and poultry litter reduced the impact of manure surface runoff. Hormones also showed little vertical and lateral movement in the soil. The transformation rates of 1,4-androstadiene-3,17-dione, 4-androstene-3,17-dione and estrone were studied comparing the effects of temperature, soil type, and application type. The calculated half-life of 1,4-androstadiene-3,17-dione in poultry litter surface-applied soils was 1.9 times higher than that in the poultry litter subsurface-injected soils, indicating a faster dissipation rate in the injection slits. Estrone persisted at detectable levels for the duration of the study in all treatments. The continued use of best management practices and innovative manure management techniques for the reduction of nutrients, sediment and other contaminants has the potential to also reduce hormone transport to the natural environment. Monitoring many different types of hormones in all areas of an environmental system will continue to provide better information on the occurrence and fate of hormones sourced from manure amended soils.
Rapid Phytate Quantification in Manures and Runoff Sediments using HPIC
Rippner, Devin A. (Virginia Tech, 2013-08-02)
Accurate quantification of phosphorus (P) fractions in manures and agricultural runoff is vital to understanding P dynamics in the environment. Phytate is an organic form of P, with 6 phosphate groups, which is found in manures, but is difficult to quantify due to its affinity for complex formation with aluminum (Al) and iron (Fe). The objective of the first study was to measure if high concentrations of aluminum (Al) and iron (Fe) hinder accurate quantification of phytate in dairy manure and broiler litter when measured by high performance ion chromatography (HPIC). In this study dairy manure and broiler litter samples were spiked with Al, Fe, and phytate. Samples were alkaline extracted, acidified,cleaned up and filtered, and then phytate was analyzed with HPIC. High concentrations of Fe did not hinder phytate recovery in manure or litter samples. While phytate recovery was close to 100% at typical manure and litter Al concentrations, high concentrations of Al inhibited phytate recovery in litter samples and in some manure samples. Overall, alkaline extraction of dairy manure and broiler litter and analysis with HPIC proved to be a relatively accurate, fast and cheap within normal Al and Fe ranges, compared to the commonly used NMR method. The developed method was then used to measure the concentration of phytate P (Pp) rather than the entire phytate molecule (6 moles Pp per mole phytate) in runoff waters and in an adsorption study. Phytate P has not been previously measured in runoff, due to the low concentrations of Pp found in runoff and the complexity Pp extraction from runoff. Runoff treatments were dairy manure with and without added Pp (DM, DM+Pp), broiler litter with and without added Pp (BL, BL+Pp), and control, with and without two levels of Pp (control, control Pp low, control Pp high). Runoff was collected under simulated rainfall and analyzed for total and dissolved reactive P (DRP). Runoff was also separated into sediment (>0.45"m) and liquid (<0.45"m and lyophilized) fractions for Pp analysis by high performance ion chromatography (HPIC). The new method for Pp analysis recovered 70% of Pp spiked into runoff samples. Phytate P was found only on the sediment fraction of runoff and was not detected in the liquid fraction, even when it was lyophilized and extracted. This agreed with the adsorption study, which showed strong adsorption of Pp. Phytate P loss from control Pp high was significantly greater than Pp loss from control. ï¿½When control Pp high was removed from analysis, Pp loss from BL, BL+Pp, DM, and DM+Pp was significantly greater than from control. Phytate P in the manures appeared to behave differently than pure Pp salts, likely to do the formation of protein-phytate and cation-phytate complexes in the manures. Phytate P had no effect on DRP in runoff for any treatment, indicating no significant release of inorganic P through competitive binding. The majority of P lost in runoff was in fractions other than DRP and Pp in the sediment fraction. Efforts to control the erosive loss of soil during rainfall events appear to be the best way to reduce total P loss, irrespective of the presence of Pp.
Soil Organic Matter Dynamics in Cropping Systems of Virginia's Valley Region
Sequeira, Cleiton Henrique (Virginia Tech, 2011-02-04)
Soil organic matter (SOM) is a well known indicator of soil quality due to its direct influence on soil properties such as structure, soil stability, water availability, cation exchange capacity, nutrient cycling, and pH buffering and amelioration. Study sites were selected in the Valley region of Virginia with the study objectives to: i) compare the efficiency of density solutions used in recovering free-light fraction (FLF) organic matter; ii) compare different soil organic fractions as sensitive indices of short-term changes in SOM due to management practices; iii) investigate on-farm effects of tillage management on soil organic carbon (SOC) and soil organic nitrogen (SON) stocks; and iv) evaluate the role of SOM in controlling soil available nitrogen (N) for corn uptake. The efficiency of the density solutions sodium iodide (NaI) and sodium polytungstate (SPT) in recovering FLF was the same at densities of 1.6 and 1.8 g cm⁻³, with both chemicals presenting less variability at 1.8 g cm⁻³. The sensitivity of SOM fractions in response to crop and soil management depended on the variable tested with particulate organic matter (POM) being the most sensitive when only tillage was tested, and FLF being the most sensitive when crop rotation and cover crop management were added. The on-farm investigation of tillage management on stocks of SOC and total soil N (TSN) indicated significant increases at 0–15 cm depth by increasing the duration (0 to 10 years) of no-tillage (NT) management (0.59 ± 0.14 Mg C ha⁻¹ yr⁻¹ and 0.05 ± 0.02 Mg N ha⁻¹ yr⁻¹). However, duration of NT had no significant effect on SOC and TSN stocks at 0–60 cm depth. Soil available N as controlled by SOM was modeled using corn (Zea mays L.) plant uptake as response and several soil N fractions as explanatory variables. The final model developed for 0–30 cm depth had 6 regressors representing the different SOM pools (active, intermediate, and stable) and a 𝑅² value of 65%. In summary, this study provides information about on-farm management affects on SOM levels; measurement of such effects in the short-term; and estimation of soil available N as related to different soil organic fractions.
Soil Organic Nitrogen - Investigation of Soil Amino Acids and Proteinaceous Compounds
Ma, Li (Virginia Tech, 2015-05-01)
Soil carbon (C) and nitrogen (N) are predominantly in organic form. Proteins/ peptides, as an important organic form of N, constitute a substantial part of soil organic matter. On one hand, proteins/peptides are an important N source for plants and microorganisms, particularly in soils where inorganic N is limited. On the other hand, their stabilization in soils by forming organo-mineral associates or macromolecule complex reduces the C loss as CO2 into the atmosphere. Therefore, studies on the turnover, abundance, composition, and stability of proteins/peptides are of crucial importance to agricultural productivity and environmental sustainability. In the first part of this study, the bioavailability and distribution of amino acids, (building block of proteins/peptides), were investigated, in soils across the North-South and West-East transects of continental United States. The second part of this study aimed to understand the variations of organic C speciation in soils of continental United States. Previous investigations of the interactions between soil minerals and proteins/peptides were mostly limited to batch sorption experiments in labs, seldom of which gave the details at the molecular scales. Therefore, in the third part of this study, the molecular orientation of self-assembled oligopeptides on mineral surfaces was investigated by employing synchrotron based polarization-dependent Near Edge X-ray Adsorption Fine Structure Spectroscopy (NEXAFS) techniques. Specific aims of this study were: 1) to assess potentially bioavailable pool of proteinaceous compounds and the immediately bioavailable pool of free amino acids in surface and subsurface soils of various ecosystems; 2) to evaluate the relationship between environmental factors and levels/composition of the two pools; 3) to investigate the organic C speciation in soils of various land use; and 4) to understand molecular level surface organization of small peptides on mineral surfaces. The levels of free amino acids and hydrolysable amino acids which represent the potentially bioavailable pool of proteinaceous compounds in A-horizon soils were significantly high than in C-horizon soils due to the accumulation of organic matter in surface. On average, free amino acids accounted for less than 4 % of hydrolysable amino acids which represent the total proteinaceous compounds in soils. The composition of free amino acids was significantly different between surface soil and subsurface soil and was significantly influenced by mean annual temperature and precipitation. A relatively uniform composition of hydrolysable amino acids was observed irrespective of a wide range of land use. Significant variations were observed for the levels of free and hydrolysable amino acids along mean annual temperature and precipitation gradients, as well as among vegetation types of continental USA, suggesting levels of free and hydrolysable amino acids were associated with the above-ground biomass and root distribution. Organic C speciation investigation revealed the presence of carboxylic-C (38%), aliphatic-C (~ 22%), aromatic-C (~ 18%), O/N-alkyl-C (~ 16%), and phenolic-C (< 6%). Factors such as temperature and vegetation cover were revealed in this study to account for the fluctuations of the proportions of aromatic-C and phenolic-C, in particular. Phenolic-C may serve as a good indicator for the effect of temperature or vegetation on the composition of SOC. The average composition of soil organic C, over the continental scale, was relatively uniform over various soil ecosystems and between two soil horizons irrespective of surface organic C content. Polarization dependent NEXAFS analysis showed the oligopeptides tend to orient on mineral surface with an average tilt angle of 40 ° between the molecular chain and the mineral surface.
Transformation of Carbon, Nitrogen and Phosphorus in Deep Row Biosolids Incorporation-Hybrid Poplar Plantation in Coastal Plain Mined Land Reclamation Sites
Kostyanovskiy, Kirill Igorevich (Virginia Tech, 2009-09-17)
Deep row incorporation (DRI) is a biosolids recycling method that is especially appropriate for reclaiming disturbed land because of the extremely high application rates used. Nutrient additions in excess of the vegetation requirements, especially in coarse-textured soils, can potentially impair water quality. Increasing C and N additions with biosolids DRI can also generate emissions of greenhouse gases N₂O and CH₄ and decrease the value of C sequestration. Objectives of this research were: (i) compare the effects of DRI biosolids type and rate and annual conventional fertilizer application on N and P leaching losses; (ii) determine the effects of aging on the N, C and P dynamics in the DRI biosolids seams; (iii) compare the effects of biosolids type and conventional N fertilization on N₂O, CH₄ and CO₂ emissions; and (iv) compare the effects of DRI biosolids and conventional N fertilization on hybrid poplar biomass dynamics, C, N and P sequestration. The following eight treatments were established to achieve objectives (i) and (iv): 0 (control), 167, 337, 504 kg N ha⁻¹ yr⁻¹ as conventional fertilizer; 213 and 426 Mg ha⁻¹ anaerobically digested (AD) and 328 and 656 Mg ha⁻¹ lime stabilized (LS) biosolids applied in trenches. The amount of N lost from the DRI biosolids was 261–803 kg N ha⁻¹, while the fertilizer treatments were not different from 0 kg N ha⁻¹ yr⁻¹ control. Orthophosphate and TKP leached in negligible amounts. Deep row biosolids incorporation did not pose P leaching risks but did result in high N leaching below the biosolids seams. Aboveground biomass production in the biosolids treatments was not different from the control treatment and ranged from 2.1±0.3 to 4.0±0.5 kg tree⁻¹. The fertilizer treatments produced significantly less biomass than the control and the biosolids treatments. Hybrid poplars sequestered up to 3.20±0.54 Mg C ha⁻¹, 71±12 kg N ha⁻¹, and 11.0±1.8 kg P ha⁻¹. The planting density capable of the N uptake in order to avoid N leaching was estimated at 3912 to 11363 trees ha⁻¹. Our results suggest increased hybrid poplar planting density and decreased application rates of DRI biosolids may decrease the risk of groundwater contamination with N. Three treatments were compared to address objective (ii): 426 Mg ha⁻¹ AD and 656 Mg ha⁻¹ LS biosolids. Organic C losses were 81 Mg ha⁻¹ and 33 Mg ha⁻¹ for LS and AD biosolids, respectively. Total N lost over the course of two years was 15.2 Mg ha⁻¹ and 10.9 Mg ha⁻¹ for LS and AD biosolids, respectively, which was roughly 50% of the N applied. No significant losses of P were detected. Most of the P was Al- and Fe-bound in the AD biosolids and Ca-bound in the LS biosolids. Our results indicated that recommended rates of DRI biosolids in coarse textured soils should be based on crop N requirements and N mineralization considerations, and P mobility from biosolids of the type used should not pose a water quality risk. Four treatments were compared to address objective (iii): 426 Mg ha⁻¹ AD and 656 Mg ha⁻¹ LS biosolids; 0 (control) and 504 kg N ha⁻¹ y⁻¹ as conventional fertilizer. Contributions from CH₄ and CO₂ emissions to the radiative forcing were very small compared to N₂O. More N₂O was produced in the DRI biosolids treatments than in the conventional fertilizer treatments, and N₂O production was higher in AD than in LS. Expressed as global warming potentials, N₂O emissions from AD (101.5 Mg C ha⁻¹) were 4.6 times higher than from LS and 14.5-16.1 times higher than from the fertilizer treatments. High N₂O emissions from deep row incorporated biosolids reduce the C sequestration benefits of the DRI method.
Water repellency effects on liquid- and vapor-phase water exchange in soil and clay minerals
Chen, Jingjing (Virginia Tech, 2019-02-12)
Drought conditions and wildfires can induce soil water repellency. Precipitation shifts are expected to exacerbate drought and wildfire in regions such as the southeastern United States, making it critical to understand how repellency affects water exchange processes in soil. The objectives of this dissertation were to 1) quantify the water vapor sorption dynamics of two clay minerals in which water repellency was induced; 2) identify if and for how long wildfires in humid hardwood forests induce water repellency, 3) evaluate if organic carbon content and hydrophobic functional groups explain actual and potential soil water repellency; and 4) understand how vertical position (i.e., depth) of water repellent layers affect infiltration processes. To meet these objectives, a laboratory test was first conducted examining water vapor sorption processes in water-repellent clay minerals. Next, a field study occurred in two forests that experienced wildfires in late 2016: Mount Pleasant Wildfire Refuge, Virginia, and Chimney Rock State Park, North Carolina, United States. Measurements include water drop penetration time, soil water content, and tension infiltration. Complimentary laboratory tests quantified potential soil water repellency, soil organic carbon content and hydrophobic functional groups. Results showed that water repellency inhibited water vapor condensation because of altered mineral surface potentials and decreased surface areas. Burned hardwood forest soils presented water repellency for > 1 year, though laboratory measurements presented different trends than in situ measurements. Total organic carbon content and hydrophobic functional groups correlated with soil water repellency measured in the laboratory but not the field. Soil water content was lower in burned than unburned soils, and negatively correlated with water repellency. Water repellency in the surface layers significantly reduced relative water infiltration rates, whereas subsurface water repellency did not, and water repellency persisted longer in sites with surface compared to subsurface water repellency. Finally, while the wildfires increased the occurrence of water repellency, they did not alter the underlying relationship between relative infiltration and surface water repellency. Altogether, this study provided new insight into water repellency effects on water partitioning at soil-atmosphere interfaces, and presented evidence of soil and hydrological changes induced by wildfires in humid hardwood forests.

Browsing by Author "Shang, Chao"

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