Soil Quality and Urban Gardening Abstract
Authors:Cindy Khov, Bert Ly
Mentor:Monica Palomo, Assistant Professor , California State Polytechnic University Pomona
Through gardening, soil contaminants such as lead (Pb) can show soil to plant movement, changing soil quality over time. This study focuses on a Southern California community garden’s soil quality. Pb elevation is common in many urban soils and will be used to evaluate soil quality change. Radishes and lettuce were planted to observe soil-plant transfer. When harvested, crops were cleaned by laboratory and kitchen style cleaning with an additional method applied to radishes: peeling. Plant samples were digested using concentrated HNO3 acid in a microwave digestion unit. Soil samples, taken during harvest, were digested using EPA 3051 method to determine trace element concentrations. Kitchen style cleaned samples showed higher Pb concentrations due to soil particle adherence to samples that laboratory cleaning would better remove. The samples’ Pb concentrations indicate soil-plant transfer. While the EPA does not currently have vegetable standards, WHO/FAO standards are followed for international trade. According to WHO/FAO, they have classified the maximum level for lead contaminants in leafy vegetables and bulb vegetables to not exceed 0.3 mg/kg and 0.1 mg/kg, respectively. The leafy vegetable samples in this experiment produced results of 0.4 mg/kg for laboratory cleaning and 0.9 mg/kg for standard kitchen cleaning. The bulb vegetable samples surpassed the 1.5 mg/kg limit for the specified procedures mentioned above.