Fig. 3. Model results for the regional zinc balance. (a) Input and output fluxes, where I_Man = inputs by animal manure; I_Se, I_CF, and I_Pes = inputs with sewage sludge, commercial fertilizer, and pesticides, respectively; I_Atm = atmospheric deposition; O_Crop = output by crop removal; and O_L = leaching. The boxes give the interquartile range (IQR). The horizontal bar in each box indicates the median. The length of the whiskers is 1.5 x IQR. Values outside these limits are plotted as points. (b) Net flux, where x_med = median flux. (c) Contribution of the uncertainty sources to total variance of the net flux, where RTU = root of uncertainty. For symbols of uncertainty sources, see Appendix 1.