TITLE Example 19B.--Cd sorption on X, Hfo and OC in loamy soil # PRINT -reset false -user_print true SURFACE_MASTER_SPECIES # Monodentate 60% H_a H_aH; H_b H_bH; H_c H_cH; H_d H_dH H_e H_eH; H_f H_fH; H_g H_gH; H_h H_hH # Bidentate 40% H_ab H_abH2; H_ad H_adH2; H_af H_afH2; H_ah H_ahH2 H_bc H_bcH2; H_be H_beH2; H_bg H_bgH2; H_cd H_cdH2 H_cf H_cfH2; H_ch H_chH2; H_de H_deH2; H_dg H_dgH2 SURFACE_SPECIES H_aH = H_aH; log_k 0; H_bH = H_bH; log_k 0; H_cH = H_cH; log_k 0; \ H_dH = H_dH; log_k 0; H_eH = H_eH; log_k 0; H_fH = H_fH; log_k 0; H_gH = H_gH; log_k 0; \ H_hH = H_hH; log_k 0; H_abH2 = H_abH2; log_k 0; H_adH2 = H_adH2; log_k 0; H_afH2 = H_afH2; log_k 0; H_ahH2 = H_ahH2; log_k 0; H_bcH2 = H_bcH2; log_k 0; H_beH2 = H_beH2; log_k 0; H_bgH2 = H_bgH2; log_k 0; H_cdH2 = H_cdH2; log_k 0; H_cfH2 = H_cfH2; log_k 0; H_chH2 = H_chH2; log_k 0; H_deH2 = H_deH2; log_k 0; H_dgH2 = H_dgH2; log_k 0; # Protons H_aH = H_a- + H+; log_k -1.59 H_bH = H_b- + H+; log_k -2.70 H_cH = H_c- + H+; log_k -3.82 H_dH = H_d- + H+; log_k -4.93 H_eH = H_e- + H+; log_k -6.88 H_fH = H_f- + H+; log_k -8.72 H_gH = H_g- + H+; log_k -10.56 H_hH = H_h- + H+; log_k -12.40 H_abH2 = H_abH- + H+; log_k -1.59; H_abH- = H_ab-2 + H+; log_k -2.70 H_adH2 = H_adH- + H+; log_k -1.59; H_adH- = H_ad-2 + H+; log_k -4.93 H_afH2 = H_afH- + H+; log_k -1.59; H_afH- = H_af-2 + H+; log_k -8.72 H_ahH2 = H_ahH- + H+; log_k -1.59; H_ahH- = H_ah-2 + H+; log_k -12.40 H_bcH2 = H_bcH- + H+; log_k -2.70; H_bcH- = H_bc-2 + H+; log_k -3.82 H_beH2 = H_beH- + H+; log_k -2.70; H_beH- = H_be-2 + H+; log_k -6.88 H_bgH2 = H_bgH- + H+; log_k -2.70; H_bgH- = H_bg-2 + H+; log_k -10.56 H_cdH2 = H_cdH- + H+; log_k -3.82; H_cdH- = H_cd-2 + H+; log_k -4.93 H_cfH2 = H_cfH- + H+; log_k -3.82; H_cfH- = H_cf-2 + H+; log_k -8.72 H_chH2 = H_chH- + H+; log_k -3.82; H_chH- = H_ch-2 + H+; log_k -12.40 H_deH2 = H_deH- + H+; log_k -4.93; H_deH- = H_de-2 + H+; log_k -6.88 H_dgH2 = H_dgH- + H+; log_k -4.93; H_dgH- = H_dg-2 + H+; log_k -10.56 # Calcium H_aH + Ca+2 = H_aCa+ + H+; log_k -3.20 H_bH + Ca+2 = H_bCa+ + H+; log_k -3.20 H_cH + Ca+2 = H_cCa+ + H+; log_k -3.20 H_dH + Ca+2 = H_dCa+ + H+; log_k -3.20 H_eH + Ca+2 = H_eCa+ + H+; log_k -6.99 H_fH + Ca+2 = H_fCa+ + H+; log_k -6.99 H_gH + Ca+2 = H_gCa+ + H+; log_k -6.99 H_hH + Ca+2 = H_hCa+ + H+; log_k -6.99 H_abH2 + Ca+2 = H_abCa + 2H+; log_k -6.40 H_adH2 + Ca+2 = H_adCa + 2H+; log_k -6.40 H_afH2 + Ca+2 = H_afCa + 2H+; log_k -7.45 H_ahH2 + Ca+2 = H_ahCa + 2H+; log_k -10.2 H_bcH2 + Ca+2 = H_bcCa + 2H+; log_k -6.40 H_beH2 + Ca+2 = H_beCa + 2H+; log_k -10.2 H_bgH2 + Ca+2 = H_bgCa + 2H+; log_k -10.2 H_cdH2 + Ca+2 = H_cdCa + 2H+; log_k -6.40 H_cfH2 + Ca+2 = H_cfCa + 2H+; log_k -10.2 H_chH2 + Ca+2 = H_chCa + 2H+; log_k -10.2 H_deH2 + Ca+2 = H_deCa + 2H+; log_k -10.2 H_dgH2 + Ca+2 = H_dgCa + 2H+; log_k -10.2 # Cadmium H_aH + Cd+2 = H_aCd+ + H+; log_k -1.52 H_bH + Cd+2 = H_bCd+ + H+; log_k -1.52 H_cH + Cd+2 = H_cCd+ + H+; log_k -1.52 H_dH + Cd+2 = H_dCd+ + H+; log_k -1.52 H_eH + Cd+2 = H_eCd+ + H+; log_k -5.57 H_fH + Cd+2 = H_fCd+ + H+; log_k -5.57 H_gH + Cd+2 = H_gCd+ + H+; log_k -5.57 H_hH + Cd+2 = H_hCd+ + H+; log_k -5.57 H_abH2 + Cd+2 = H_abCd + 2H+; log_k -3.04 H_adH2 + Cd+2 = H_adCd + 2H+; log_k -3.04 H_afH2 + Cd+2 = H_afCd + 2H+; log_k -7.09 H_ahH2 + Cd+2 = H_ahCd + 2H+; log_k -7.09 H_bcH2 + Cd+2 = H_bcCd + 2H+; log_k -3.04 H_beH2 + Cd+2 = H_beCd + 2H+; log_k -7.09 H_bgH2 + Cd+2 = H_bgCd + 2H+; log_k -7.09 H_cdH2 + Cd+2 = H_cdCd + 2H+; log_k -3.04 H_cfH2 + Cd+2 = H_cfCd + 2H+; log_k -7.09 H_chH2 + Cd+2 = H_chCd + 2H+; log_k -7.09 H_deH2 + Cd+2 = H_deCd + 2H+; log_k -7.09 H_dgH2 + Cd+2 = H_dgCd + 2H+; log_k -7.09 END SURFACE 1 # 1 g soil = 0.7% Organic Matter ~ 3.5 mg Organic Carbon. # 7.1 meq charge per g OC # For Psi vs I (= ionic strength) dependence, adapt specific surface area in PHRC: # SS = 159300 - 220800/(I)^0.09 + 91260/(I)^0.18 # Example: SS = 46514 m2/g for I = 0.003 mol/l # # 3.5 mg OC, 0.025 meq total charge, distributed over the sites: # charge on 4 nHA sites: -2.84 / 4 * 3.5e-3 / 1e3 (eq) H_a 2.48e-06 46.5e3 3.50e-03 H_b 2.48e-06; H_c 2.48e-06; H_d 2.48e-06 # charge on 4 nHB sites: 0.5 * charge on nHA sites H_e 1.24e-06; H_f 1.24e-06; H_g 1.24e-06; H_h 1.24e-06 # charge on 12 diprotic sites: -2.84 / 12 * 3.5e-3 / 1e3 H_ab 8.28e-07; H_ad 8.28e-07; H_af 8.28e-07; H_ah 8.28e-07 H_bc 8.28e-07; H_be 8.28e-07; H_bg 8.28e-07; H_cd 8.28e-07 H_cf 8.28e-07; H_ch 8.28e-07; H_de 8.28e-07; H_dg 8.28e-07 -donnan # 1 g soil = 2.79 mg Fe = 0.05 mmol Fe = 4.45 mg FeOOH # 10% has ferrihydrite reactivity Hfo_w 1e-6 600 4.45e-4 Hfo_s 0.025e-6 -equilibrate 1 EXCHANGE 1 X 55.7e-6 -equilibrate 1 SOLUTION 1 pH 6.0 Ca 1 Cl 2 Cd 1e-6 REACTION 1 CdCl2 1 2e-6 in 20 USER_GRAPH Example 19 -headings Cd_HumicAcids CdX2 Cd_Hfo TOTAL -chart_title "Deterministic Sorption Model" -axis_titles "Dissolved Cd, in micrograms per kilogram water" \ "Sorbed Cd, in micrograms per gram soil" -plot_tsv_file ex19_meas.tsv -axis_scale x_axis 0 40 -axis_scale y_axis 0 6 -initial_solutions true -start 10 H_Cd = SURF("Cd", "H") + EDL("Cd", "H") 20 print CHR$(10) + " ug Cd/L =", tot("Cd") * 112.4e6, " ug Cd/g = ", H_Cd * 112.4e6 \ ," Kd (L/kg) = ", H_Cd*1e3/tot("Cd"), " ug Cd/g in DL =", \ EDL("Cd", "H") * 112.4e6 30 print "Excess meq Ca in DL =", EDL("Ca", "H")*2 - EDL("water", "H") * tot("Ca")*2 40 print "Excess meq Cl in DL =", EDL("Cl", "H") - EDL("water", "H") * tot("Cl") 50 print "Surface charge =", EDL("Charge", "H") 55 af_OM = 1 / 9 60 H_Ca = (SURF("Ca", "H") + EDL("Ca", "H")) * af_OM 70 print 'Total Ca in/on organic matter =', H_Ca, ' CEC on OM =' H_Ca*200/TOT("X"),\ '%.' 80 x = TOT("Cd") * 112.4e6 90 H_Cd = H_Cd * 112.4e6 * af_OM 100 CdX2 = mol("CdX2") * 112.4e6 * 0.96 110 Hfo_Cd = (mol("Hfo_wOCd+") + mol("Hfo_sOCd+")) * 112.4e6 120 PLOT_XY x, H_Cd, color = Green, line_width = 2, symbol = None 130 PLOT_XY x, CdX2, color = Brown, line_width = 2, symbol = None 140 PLOT_XY x, Hfo_Cd, color = Black, line_width = 2, symbol = None 150 PLOT_XY x, H_Cd + CdX2 + Hfo_Cd, color = Red, line_width = 2, symbol = None -end END