Gardening On Arsenic and Lead-Contaminated Brownfields: Is It Safe?: II.

Increased food prices and a desire to be cognizant of food sources have led to the transformation of brownfields located in older industrialized cities of the US to some productive use. Neighborhood farmers who harness these lands for vegetables/short term crops maybe challenged by environmental contaminants. Gardening on raised beds with “clean” soil, has been a popular but expensive approach. In 2010, we established a 37.2m² test plot on a moderately acidic (pH of 5.6) loamy sand soil (81% sand, 19% silt) containing elevated levels of lead (Pb) and arsenic (As) in Tacoma, WA. Main objectives of our work are to conduct site-specific research, and provide technical assistance for community gardening initiatives in different geographic areas of the country. Specific objectives were to evaluate plant uptake of As and Pb by three different vegetable crops, and the effectiveness of soil amendments on reducing plant availability and bioaccessibility of these contaminants. The basic experimental design was a randomized complete block with split plot arrangement. The main plot factor was Tagro mix (a blend of biosolids, sawdust and screened sand) applied at 2 levels (control/no tagro and tagro mix adjusted to pH using dolomite. Lettuce (North Star), carrot (Red cored Chantenay), and tomatoes (Early Girl) grown and harvested upon maturity, were tested for total Pb and As concentrations following “kitchen style washing” and a laboratory cleaning procedure. Average soil Pb concentrations for control plots ranged from 166 to 172 mg/kg, while lime and tagro amended (LT) plots ranged from 160 to 204 mg/kg. Average soil As concentrations ranged from 82 to 86 mg/kg in control plots while LT plots ranged from 58 to 88 mg/kg. Arsenic concentrations in all three vegetable crops with or without tagro treatment were below 0.2 mg/kg (DW basis) while Pb concentrations ranged from 0.5 to 22.5 mg/kg.