Recipient Organization
UNIVERSITY OF DELAWARE
(N/A)
NEWARK,DE 19717
Performing Department
Plant & Soil Sciences
Non Technical Summary
Nutrients and contaminants (e.g., pesticides and heavy metals) and emerging contaminants (e.g. hormones and pharmaceuticals) are widespread in the environment. Pathogens, which include viruses, bacteria or other microorganisms, are also creating major challenges as water resources dwindle and wastewater is reused. These contaminants, pathogens and metabolites present unique challenges in understanding their fate and transport in the soil-water environment. Many contaminants are potent at very low concentrations and labile, associating strongly with soil solids and undergoing rapid and complex transformations. Often these compounds (pesticides, radionuclides, and metals) can strongly associate with soil colloid particles (≤ 10mm in size), which can significantly enhance the mobility. Colloids can be mineral particles, organic entities, or small living organisms, like bacteria or viruses, and engineered nanoparticles. They are ubiquitous in soils, and play an important role in soil formation and contaminant fate and transport. Understanding colloidal processes in soils and sediments is important for environmental quality and human health. We need to understand the mechanisms of colloid retention at different interfaces to make accurate predictions of colloid transport, colloid-facilitated transport of contaminants, nutrients, and other colloid associated entities such as soil carbon. The improved understanding will allow design of effective management and remediation practices to prevent soil and water contamination.We will use microscopic (electron and confocal microscopy) and macroscopic (light scattering, column experiments) techniques as well as filed sampling to investigate and quantify the mechanisms controlling colloid fate and transport in the vadose zone and incorporate them into mathematical models (HYDRUS). In Delaware, we will particularly focus on improving the understanding of colloid mobilization and its role in carbon cycling and nutrient (P) transport in wetlands and the Chesapeake watersheds.Our project goals include the following: 1) to generate new insight into the role natural wetlands play in cycling of P and C, and the impact of hydrologic characteristics on these processes; 2) to develop a comprehensive understanding of the geochemical and hydrological mechanisms leading to DOM and P release and transport as affected by colloid mobilization in wetlands; 2) to re-assess current nutrient management plans, existing models on total maximum daily load (TMDL), and possibly widen source-based research to identify the extent to which agricultural P sources have impaired water quality in the Chesapeake Bay as well as other watersheds in the country. Scientific findings from this research will be disseminated through publications, scientific conferences and various extension programs at UD and in the region.
Animal Health Component
25%
Research Effort Categories
Basic
75%
Applied
25%
Developmental
(N/A)
Goals / Objectives
To improve our fundamental understanding of soil physical properties and processes, and how they interact with other environmental and biogeochemical processes across various spatial and temporal scales.
To extend our knowledge of scale-appropriate methodologies to improve stakeholder-management of soil and water resources that benefit agricultural, natural resource and environmental sustainability.
Project Methods
The objectives will be accomplished through extensive field sampling from selected wetland sites and the Chesapeake watersheds and complimentary laboratory experiments. We will measure the concentrations and identify the forms of N, P, Fe, OM, and mobile colloids in the inlet and outlet of wetlands. We will conduct batch and column experiments to elucidate the mechanisms of colloid mobilization and the role of mobile colloids in the fate and transport of N, P, and OM.We will analyze particulate and colloidal P in water columns collected along the continuum from the low salinity agricultural runoff dominated Deer Creek that drains into the Susquehanna River, the lower reaches of the Susquehanna River, and its estuary in the Chesapeake Bay. We will apply colloidal sciences paired with oxygen isotopes in phosphate (IRMS) techniques along with a suite of mineralogical (mXRD), microscopic (SEM, TEM, and confocal), elemental, and spectroscopic (1H, 13C, and 31P NMR) analyses and run a series of field simulated laboratory experiments to understand physicochemical and biological mechanisms controlling the mobilization of particulate/colloidal P and bioavailability of P in particulate/colloid matter.The laboratory and field studies will be closely integrated: field observations will be used to determine the critical parameters to be closely examined in laboratory experiments and laboratory results will provide mechanistic interpretation of field data.The data from these experiments will be used to assess the release and transport characteristics of DOM, P and colloids under the various experimental conditions.The existing HYDRUS 1-D code that has incorporated a colloid transport segment and a wetland module (Šimunek,http://www.pc-progress.com/en/Default.aspx?jirka-simunek) will be used to quantify the experimental results. In the event that the existing models cannot be used to describe the complex interplay between DOM, colloids and redox conditions, we hope to provide experimental basis for the conceptualization of the reactions/processes so that a model suitable for describing such processes may be developed in the future.