BIOACCESSIBILITY OF METALS IN SAILS FOR DIFFERENT LIQUID TO SOLID RATIOS IN SYNTHETIC GASTRIC FLUID

The bioaccessible fraction of metals in the stomach has been estimated for two soil materials using laboratory synthesized gastric juice. He avy metals present in each soil matrix were extracted and measured, as a technique to simulate metal solubilization processes that occur in the human stomach. The results from the synthetic gastric juice extrac tion were compared to values obtained using a modified EPA concentrate d acid extraction procedure, method 3051, on the same soils. The exper iments evaluated the effect of varying the liquid to solid ratio on ga stric juice extraction efficiency for arsenic (As), chromium (Cr), nic kel (Ni), cadmium (Cd), and lead (Ph). Soil samples employed were a Na tional Institute of Standards and Technology (NIST) standard soil (Mon tana SRM 2710) and a composite hazardous waste contaminated soil from Jersey City, NJ. The current work demonstrates that bioaccessibility i s not the same for each metal within a given soil, nor between the soi ls. Estimates of the bioaccessible fraction of the metals studied rang ed from 2 to 61% of the NIST certified values for Montana soil, and fr om 3% to 58% of EPA method 3051 values in contaminated Jersey City soi l. The experiments indicated that the bioaccessibility of metals in th e soils extracted by the in vitro synthetic gastric juice will only be affected slightly by changes in gastric fluid liquid to solid ratios for the range 100:1 to 5000:1 (mL/g). Further, the masses of each soil (0.05 or 0.5 g) used did not affect the bioaccessibility at the 1000: 1 ratio.