Research Projects

Research in the EBL lab is generously funded through federal grants (USDA, NSF) and other supports from UD, Unidel, commodity groups, and non-profit organizations totaling $8.7 million. Major current research area includes:

1) Phosphorus speciation,  transformation, and loss from soils
             In the era after the Green Revolution, high-intensity livestock production and continued application of manure and fertilizers in excess of crop uptake have resulted in the build-up of P levels in agricultural soils. In some cases, the capacity of the soil to adsorb P has reached saturation, risking the increased loss of P to ground and surface waters.
With a record-high publication related to soil P (> 300,000), the fundamental question on bioavailability and transformation of P in soils both on temporal and spatial scales are yet to be fully addressed. The current emphasis in this axis of research includes identification of the sources and pathway of (trans)formation of residual and recalcitrant P pools. It employs stable isotopes, along with other mineralogical and geochemical techniques, as i) ‘tracer’ to disentangle specific biogeochemical reactions and interactions among different P pools in soil, ii) ‘marker’ to distinguish successive generations of legacy P leached and/and retained in (sub)surface soils corresponding to the changes in P fertilization; and (iii) ‘integrator’ for input/output budgets in soil compartments and export from an ecosystem.
Funding sources: NSF EPSCoR 2013, USDA 2013, 2016
Major collaboration: Donald Sparks (U Delaware)
Publications: Joshi et al. (SSSAJ 2016, SS 2018), Upreti et al. (SSSAJ 2015), Li et al. (SSSAJ 2015) (see publication page for full citation and weblink)

2) Sources and cycling of major organic phosphorus compounds: inositol phosphate, polyphosphate, and glyphosate

i) Phytate and other inositol phosphates
Among different P pools in soils, organic P constitutes 40-55% of total P in agricultural soils that have been amended with poultry litter or animal manure. Inositol phosphates (IPx; where x is the number of phosphate moieties in inositol) comprise generally 36-54% of organic phosphorus in soils.
Research in this axis of research aims to address gaps in current knowledge regarding the distribution of IPx in soils and waters, microbial (phytate degrading bacteria and beta-propeller phytase gene expression) response to phytate loading, and de-phosphorylation of IPx by different phosphatase enzymes and characteristic degradation pathways. It applies a variety of non-conventional research tools including HPLC/HPIC, solid-state and solution 31P NMR, and stable isotopes to address these questions.
Funding sources: NSF-CAREER 2017 and NSF-CHE 2017
Major collaborations: Ludmilla Aristilde (Cornell University, NY), Ralf Greiner (Germany), Arash Massoudieh (Catholic U of America, DC)
Publications: Wu et al. (SSSAJ 2015), Feng et al. (ES&T 2016), Stout et al. (SSSAJ 2016), Sun et al. (SSSAJ 2017), Sun and Jaisi (PS, 2018) (see publication page for full citation and weblink)

ii) Glyphosate
Pesticides are an integral part of US agriculture with virtually 100% of planted acres treated with one or more varieties and annual expenditures reaching approximately $12 billion in 2008. Glyphosate [(N-phosphonomethyl)glycine], a broad-spectrum herbicide, outranks all other herbicides particularly due to i) its effectiveness in controlling many types of weeds; ii) the emergence of glyphosate-tolerant genetically modified crops (including soybean, corn, cotton, and canola); iii) its lower cost relative to other herbicides; iv) its utility in no-till farming, minimizing soil erosion, and water conservation; and v) the public perception that glyphosate has low toxicity and mobility in the environment. Various studies, however, have shown possible toxicological effects linked to its widespread use in soils and other environments.
Current research thrust in this axis aims to overcome the existing methodological challenge to discriminate the parental source/s of a particular degradation product by applying the multi-isotope tool to relate parental and daughter molecules and trace them in the environment. In another front, research on bond specificity has been explored to distinguish and differentiate between biotic and abiotic pathways of glyphosate degradation and examine the potential bias towards the particular pathway of degradation. It applies a variety of research methods including HPLC-MS, NMR (1H, 13C, and 31P), stable isotopes, and general/molecular microbiological techniques to address these questions.
Funding sources: USDA 2017
Major collaborations: Ludmilla Aristilde (Northwestern University, NY), Adam Wallace (U Delaware), Robert Lerch (USDA, ARS)
Publications: Paudel et al. (SSSAJ 2015), Li et al. (JFAC 2016), Jaisi et al. (JFAC 2016), Li et al. (ES&T 2018); Li and Jaisi (ESC 2019), Sun et al. (WR, 2019) (see publication page for full citation and weblink)

iii) Polyphosphate and nutrient recovery from agricultural and human wastes/waters
Polyphosphate (poly-P) is a chain of phosphate moieties linked through high-energy phospho-anhydride bonds and plays an important role in regulatory functions in prokaryotic cells. Understanding of bacterial synthesis and degradation of poly-P and corresponding isotope effects provides insights into the roles of poly-P in the environmental P cycling.
Our team aims to investigate the formation and degradation of poly-P in the environments, especially in P rich environments such as agricultural and human wastes/waters and related treatment plants. It includes research on enzymatic (cell-free and intact cell) degradation of poly-P and the relationship of orthophosphate and poly-P along with enzyme activity. Another novel area of research is on P recovery from agricultural wastes and fabrication into a novel nano fertilizer. The aim of this research is to develop a fundamental understanding of crystal chemical-structure and function relationships of synthetic nanofertilizer.
Funding sources: NSF EPSCoR 2013, USDA 2017
Major collaborations: Yan Jin (U Delaware); Jason White (CT Ag Experiment Station) 
Publications: Wang et al. (JCH 2015; ES&T 2015; ES-N 2016) (see publication page for full citation and weblink)

3) Phosphorus cycling in the Chesapeake Bay and its watershed
              The Chesapeake Bay, the largest and most productive estuary in the USA, suffers from varying degrees of eutrophication and dead zone, fueled by both point and non–point source nutrient loading. A significant restoration and protection effort has been implemented to improve the water quality in the Bay. Restoration of the Bay is complicated by the multitude of nutrient sources, their temporally and spatially variable inputs, and complex interacting factors affecting the occurrence, fate, and transport of nutrients.  Phosphorus mass balance calculations show that the bay imports ~26% and ~30% of total P from the coastal ocean and from the sediment-water interface, respectively.
Research in the Chesapeake Bay includes identification of P sources in water and sediment columns and biogeochemical processes that promote the release of P from sediment including the positive feedback loop to bottom-water hypoxia and surface eutrophication. It applies stable isotopes, NMR, and synchrotron-based XAS techniques to identify the sources and fate of P in the Bay. Research in the bay watersheds includes East Creek, MD and Lower reaches of the Susquehanna River. It aims to develop a better understanding of the physicochemical and biological mechanisms underpinning mobilization and transport of particulate, colloidal and dissolved P in the downstream continuum and biological cycling in open waters. It applies isotope techniques along with a suite of mineralogical (XRD), microscopic (SEM and TEM), elemental, and spectroscopic (1H, 13C, and 31P NMR) methods to address these questions with particular focus along the physicochemical and hydrodynamic gradients in the agriculture-source runoff dominated region to the river estuaries in the Chesapeake Bay.
Funding sources: NSF EPSCoR 2013, USDA 2014, 2016, NSF 2018
Major collaborations: Donald Sparks, Yan Jin (U Delaware), Patrick Reardon (Oregon S University), Ravi Kukkadapu (PNNL)
Publications: Stout et al. (GCA 2014), Li et al. (ES&T 2015), Joshi et al. (ES&T 2015), Li et al. (JGR-B 2016a,b), Li et al (JGR-B, 2019), Mingus et al. (2019), Su et al. (LO, 2020) (see publication page for full citation and weblink)

4) Method development on stable isotopes
            This research project investigates fundamental processes and phosphate oxygen isotope effects associated with major biogeochemical reactions in controlled and complex media and interfaces. The overall goal of this axis of the research is to develop phosphate oxygen isotope ratios as a biogeochemical tracer to understand the relative roles of abiotic and biotically driven P cycling in different environments.
Funding sources: NSF EPSCoR 2013, USDA 2013, NSF 2017
Major collaborations: Ruth Blake (Yale U, CT), John Eiler (CalTech, CA)
Publications: Stout et al. (GCA 2014), Jaisi and Blake (AA 2014), Jaisi et al. (book 2014; JAFC 2016; WR 2017), Blake et al. (AJS 2017), Sun et al. (SSSAJ 2017, WR 2019), Xia et al. (IEHS, 2020) (see publication page for full citation and weblink)

5) Other active collaborators
          Other active collaborators include Albert Colman (U Chicago, IL), Sae-Jung Chen (Korean Basic Science Institute, S Korea), Todd Kana (U Maryland, MD), Wei Li (Nanjing U, China), Debora Rodrigues (U Houston, TX), Kaushlendra Singh (U West Virginia, WV), Delphis Levia (U Delaware, DE), Wei-Jun Cai (U Delaware, DE), Milko Jorquera (U Frontera, Chile), Avner Gross (U Jerusalem, Israel), Gulihan Ozbay (Delaware State U, DE), Nengwang Chen (Xiamen U, China), Xionghan Feng (Huazhong Ag U, China), Philips Casanova (Northeastern U, MA), Zhi-gang Chen (Xiamen U, China), Zhonggi He (USDA ARS), Sushil Adhikari (Auburn U, AL), Yujun Wang (CAS, China), Yu Wang (CAS, China), Samir Khanal (U Hawaii, HA), Yong Guan Zhu (CAS, China).