Progress 09/15/06 to 09/14/07
Outputs
OUTPUTS: One major activity from this project was to mentor and teach graduate students at the University of Florida, the University of Puerto Rico, and students from Sub-Saharan Africa universities how soil organic matter content and functionality affect the sorption and transformation of organic pesticides. The major soil components that influenced sorption of 9 pesticides: ametryne, atrazine, carbaryl, carbofuran, diuron, DDT, dieldrin, endosulfan, and metolachlor, were soil organic matter content and organic carbon, and the aromatic functional groups of organic matter.The data collected from this project were presented and discusses at state, regional, and national meetings in conferences, workshops and symposia in Florida and Puerto Rico. Summer courses were gives by the PD to MS and PhD chemistry students from (Ethiopia, Kenya, Sudan, Tanzania, Uganda and Zambia) on interaction of pesticides with tropicals soils. Our project has a data base for sorption of pesticides in 21 carbonatic soils (from FL and PR), 16 Histosol soil samples (from FL and PR), 5 Spodosol soil samples (from Fl), and 21 Oxisol soil samples from Uganda. Degradation data are also available for some pesticides in some of the soils used in this study. A sorption model based on the Solvophobic theory was developed for determining sorption of strongly hydrophobic organic chemicals(SHOCs) in aqueous systems. The probe compounds were DDT and dieldrin that showed that these chemicals strongly adsorb on container walls (for example Teflon) in aqueous systems and may lead to overestimating SHOCs sorption coefficients in soils. Literature data for DDT and dieldrin confirmed our findings. Data from our project demonstrated that it was impossible to determine sorption isotherms of SHOCs in aqueous systems. Therefore we propose to use a technique using mixed solvents (e.g. water + methanol) and then extrapolate sorption coefficients in aqueous systems using the Solvophobic model. NMR techniques were also found useful in identifying organic matter functional groups that might be responsible for sorption of organic pesticides. From this project we trained on MS and one PhD student at the University of Florida, one MS student from the University of Puerto Rico, and one PhD student from Makerere University, Kampala, Uganda. All four students have graduated. Educational materials distributed from this project include thesis, dissertations, abstracts, and publications in refereed scientific journals and in newsletters. PARTICIPANTS: Dr. Peter Nkdi-Kizza (PD) worked on the project during soil sampling, determination of physical and chemical soil properties, determination of sorption and degradation parameters of pesticides in aqueous and mixed solvent systeme. He wrote manuscripts from the data collected and also presented findings at scientific meetings. Dr. G. N. Kasozi, worked on the entire project as a PhD student at the University of Florida. The funds from TSTAR paid for his PhD program. He was involved in taking soil samples from the fields, measured sorption isotherms, degradation rate coefficients, and wrote a PhD dissertation, wrote manuscripts for publication, and presented papers at scientific meetings. Mr. A. Muwamba worked on the project as an MS graduate student at the University of Florida. He contributed on the sorption of strongly hydrophobic organic chemicals (SHOCs) on container walls and soils in mixed solvents. He was supported to do his research by funds from this project. He wrote his MS thises and presented papers at scientific meetings. Dr. Patrick Hatcher, Department of Chemistry and Biochemistry, Old Dominion University, provided service for NMR analysis. Dr. Jose Dumas was the CO-PD at the University of Purto Rico. He participated in all aspects of the project using soils from Purto Rico. He prepared and presented papers at scientific meetings. TARGET AUDIENCES: The target audience are farmers and Regulatory Agencies in South Florida and Puerto Rico where carbonatic soils are found. PROJECT MODIFICATIONS: A no-cost extension was applied for and approved. The extension was from September, 2007 to september, 2009 because the research by Dr. Dumas was not complete in 2007.
Impacts
The results of this study indicate that soil organic carbon content (OC) of organic matter (OM) differs significantly between soils formed under different hydrologic and vegetative settings. Soil OC is often estimated by determining OM content via mass loss on ignition (LOI) and assuming that there are 580 g OC per kg OM. We utilized TG, LOI, and the Walkley-Black (WB) methods to evaluate the relationship between OC and OM contents of carbonatic and organic soils from Florida and Puerto Rico and Spodosols from Florida. The factor to convert OM to OC was 0.56 for carbonatic soils, 0.67 for Spodosols, and 0.69 for Histosols. As such, there is no universal conversion factor between OM and OC for all soils. LOI is not a reliable OM measure if there are mass losses below 200C as is the case for Histosols. Carbonatic soils adsorbed pesticides about 1/3 less compared to non-carbonatic soils. Marl-carbonatic soils adsorbed pesticides even less compared to the outcrop carbonatic soils. The cross-polarization magic angle spinning carbon-13 nuclear magnetic resonance (CP-MAS 13-C NMR) data indicate that Algae is the primary producer of OM in the marl soils. This implied that its contribution to OC aromaticity that predomonantly control the sorption of organic pesticides is limited. The lack of aromatic-C in carbonatic soils OM probably leads to the low sorption capacities exhibited by carbonatic soils from South Florida and Puerto Rico. The linear relationship obtained by normalizing the sorption coefficients with the soil OC content indicates that OC controls the adsorption of organic pesticides in carbonatic soils. However, the data variability across different soil types suggest that functionality of OM is an important criteria for sorption. No statistically significant different half life values were observed for degradation of pesticides in carbonatic and non-carbonatic soils studied. Data were collected on sorption of DDT and dieldrin on sorption by centrifuge tubes made of polytetrafluoroethylene (PTFE), polycarbonate (PC), polypropylene copolymer (PPCO), and glass high pressure liquid chromatography vials (HPLCV). In water the calculated recoveries of DDT and dieldrin from PTFE were 32 and 43% respectively. However, the recoveries of dieldrin from HPLC vials and DDT from PC and PPCO ranged from 2 to 14%. The data demonstrate that sorption on container walls is a source of error that can reduce the integrity of the analyte and might be one of the causes for the large variability in literature KOC values for SHOCs. In designing management strategies and farming practices aimed at protecting the aquifers that underlie carbonatic soils, the strategies may include revision of application rates for pesticides applied to crops grown on carbonatic soils, adding soil amendments and long term change of the nature of OM by altering the organic carbon primary producers. A single conversion factor between OM and OC in soils of 580 g OC per kg OM should be used with caution. For determining sorption coefficients of strongly hydrophobic organic chemicals in aqueous systems sorption on container walls should always be accounted for.
Publications
- Konomi, K., Savabi, M. R., Shinde, D., Jayachandran, K., Nkedi-Kizza, P.,and Reed,S.T. 2005. Water and Atrazine Movement in a Calcareous Compost Applied Soil During Simulated Multiple Storms Events. Water Air and Soil Pollution. 165:365-377.
- Savabi, R. M., Shinde, D., Konomi, K., Nkedi-Kizza, P., and Jayachandran, K. 2005. Modeling the Effect of Soil Amendments (Compost) on Water Balance and Water Quality. Journal of Environmental Hydrology. 13:1-14.
- Nkedi-Kizza, P., Shinde, D., Savabi, R., Ouyang, Y., and Nieves, L. 2006. Sorption Kinetics and Equilibria of Pesticides in carbonatic Soils from South Florida. J. Environ. Qual. 35:268-276.
- Reed, S. T., Shinde, D., Konomi, K., Jayachandran, K., Nkedi-Kizza, P., and Savabi, M. R. 2006. Phosphorus Leaching Potential from Compost Amendments in a Carbonatic Soil. Soil Science 171:865-8.
- Kasozi, G. N., Nkedi-Kizza, P., and Harris, W. G. 2009. Varied Carbon Content of Organic Matter in Histosols, Spodosols, and Carbonatic Soils. Soil Sci Soc Am J 73:1313-1318.
- Muwamba, A., Nkedi-Kizza, P., Dean Rhue, R., and Keaffaber, J. J. 2009. Use of Mixed Solvent Systems to Eliminate Sorption of Strongly Hydrophobic Organic Chemicals on Container Walls. J Environ Qual 38:1170-1176.
- Dumas,J.A.,Nkedi-Kizza.,P.,and Montalvo,R. 2007. Study of Chemical and Physical Properties and Soil Sorption of Metolachlor and Carbofuran in Three Tropical Soils. In: Proc., 42nd Annual Meeting Caribbean Food Crops Soc (CFCS).
- Nkedi-Kizza, P., Muwamba, A., Dumas, J. A., Awuma, K. 2007. Determination of soil sorption coefficient (KOC) of strongly hydrophobic pesticides using mixed solvents and the Solvophobic model: probe pesticide, dieldrin. CFCS 43rd edition.
- Dumas, J.A., Nkedi-Kizza, P., Montalvo, R., Vega, J.,and Soler,S. 2007. The role of humic acids from carbonatic soils in the sorption process of ametryne and diuron. CFCS 43rd edition.
- Nkedi-Kizza, P., Dumas, J. A., and Soler, S. 2007. Sorption of Pesticides in Carbonatic Soils from Florida and Puerto Rico.CFCS 42nd Annual Meeting edition.
- Nkedi-Kizza, P. Mixed Solvents Eliminate Sorption of Strongly Hydrophobic Organic Chemicals on Container Walls. 2009. CSA News, July 2009 V54 NO7
- Kasozi, G. N., and Nkedi-Kizza, P. 2005. Characterization of sorption of organic pesticides in carbonatic soils of South Florida and Puerto Rico. Program Abstract, Soil and Crop Science Society of Florida (SCSSF 65th Annual Meeting - May 18-20th, 2005), DoubleTree Guest Suites, Boca Raton.
- Kasozi, G. N., and Nkedi-Kizza, P., and Dumas, J. 2007). Characterization of sorption of pesticides applied to carbonatic soils of South Florida, and Puerto Rico and Oxisols from Uganda. Program Abstract, Caribbean Food Crop Society 43rd Annual meeting,September 16-21st, Radisson Hotel, San Jose Costa Rica.
- Kasozi, G. N., and Nkedi-Kizza, P.2007. Characterization of sorption of hydrophobic organic chemicals in carbonatic and non-carbonatic soils from Florida, Puerto Rico and Uganda. Program Abstract, SCSSF 67th Annual Meeting, June 3-5th, PGA National Resort and Spa, Palm Beach Gardens, Florida. Kasozi, G. N., and Nkedi-Kizza,P.(2007). Modification of Methods Used for Characterizing Degradation and Sorption of Organic Pesticides in Soils: Carbaryl as a Probe Compound. Annual Soil and Water Science Research Forum September 15th, 2006, J. Wayne Reitz Union, University of Florida.
- Kasozi, G. N., and Nkedi-Kizza, P. 2008. Characterization of sorption of pesticides applied to carbonatic soils of South Florida, and Puerto Rico and Oxisols from Uganda. Southeastern Regional Soil Physics Conference. April 14-16th, 2008. Florida A&M, Tallahassee, Florida.
- Muwamba A., and Nkedi-Kizza P. 2007. Determination of Soil Sorption Coefficient (Koc) of Strongly Hydrophobic Organic Chemicals (SHOCs) Using Mixed Solvents Systems and the Solovophobic Model. Program Abstract, Joint Annual Meeting of the Florida State Horticulture Society and the Soil and Crop Science Society of Florida, Palm Beach Florida, 2007.
- Muwamba A., and Nkedi-Kizza,P. 2007. Determination of Soil Sorption Coefficient (Koc) of Strongly Hydrophobic Organic Chemicals (SHOCs) Using Mixed Solvents Systems and the Solovophobic Model: Probe Pesticide, Dieldrin. Program Abstract, Soil and Water Science Research Forum, University of Florida Gainesville, 09/14/2007.
- Kasozi G. N. (2007). Characterization of sorption and degradation of pesticides in carbonatic and associated soils from South Florida and Puerto Rico, and Oxisols from Uganda. PhD Dissertation, University of Florida, Gainesville. 157p. http://purl.fcla.edu/fcla/etd/UFE0021819
- Muwamba A., and Nkedi-Kizza P. 2008. Use of Mixed Solvent Systems to Eliminate Sorption of Strongly Hydrophobic Organic Chemicals (SHOCs) on Container Walls: DDT as a Probe Compound, Program Abstract, Southeastern Regional Soil Physics Conference. April 14-16th, 2008. Florida A&M, Tallahassee, Florida
- Muwamba A., and Nkedi-Kizza P. 2008. Use of Mixed Solvent Systems to Eliminate Sorption of Strongly Hydrophobic Organic Chemicals (SHOCs) on Container Walls. Program Abstract, Joint Annual Meeting of Agronomy Society of America and Geological Society of America, Houston Texas (5-9 Oct. 2008).
- Muwamba, A. 2007. Determination of aqueous soil sorption coefficient (Koc) of strongly hydrophobic organic chemicals (SHOCs) using mixed solvent systems and the Solvophobic model. MS Thesis, University of Florida; http://purl.fcla.edu/fcla/etd/UFE0021819
|