Fig. 4. Molar ratios of saturated to unsaturated fatty acids in soils spiked with 100 ng/g phenanthrene. All samples, except the before sample, were taken one day after the phenanthrene was added to soil. Numbers refer to the quantity, in µL per g of soil, of methylene chloride used to deliver phenanthrene. Error bars equal two standard deviations. Significant differences ( = 0.05) only exist between treatments labeled with different letters.