Effects of Byproducts Amended Lead Contaminated Urban Soils On Carrot Yield and Lead Uptake.

Abstract

            Lead (Pb) has been used to produce a large number of materials and manufactured products. In areas with history of lead paint use, high vehicular traffic and/or areas close to urban and industrial centers atmospheric lead deposition may be very high.   As such, urban environments in general receive high deposition of lead due to high road density, high vehicle use, industrial activity, and high population density per given area in wide spread.  The aerosol form Pb can be re-suspended and easily inhaled on fine dust particles and/or inadvertently consumed in crops grown in lead contaminated soils.   At low levels Pb will impair psychological and neurobehavioral functions particularly in the young children. Remediation of lead contaminated soils by conventional methods is expensive. The use of low cost environmentally safe amendments for the in situ fixation of lead contaminated soil is a promising remediation. In situ lead fixation does not reduce the total concentration of soil lead but changes its speciation, thus rendering the changed lead species less toxic and even non-bioavailable in the eco-system.  In our study, four different agricultural, municipal and industrial by-products that are known to contain chemical compounds that will absorb and fix lead were used.  The by-products used were poultry litter ash as a phosphate source, drinking water treatment residual as an aluminum, sulfate and iron source, steel slag as an alumina, iron, and magnesium source, and leaf compost as a organic matter source.  Soils were collected from three urban locations: Ft. DuPont National Park Washington DC, Washington, DC residential soil, and Baltimore, City MD residential soil, with an average total lead of 38, 1099 and 1088 mg kg^-1.  By products were mixed with each soil at three rates and incubated moist for 58 days. Carrots were grown for 90 days. Carrot biomass yield were significantly affected by byproducts amendment.  Carrot yield for the Baltimore soil had the highest yield followed by Washington D C and Ft DuPont respectively.  Lead uptake by carrots will be presented.