SUPPORTING INFORMATION FOR THE MANUSCRIPT. Phenanthrene sorption to soil humic acid and humin fractions

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1 SUPPORTING INFORMATION FOR THE MANUSCRIPT Phenanthrene sorption to soil humic acid and humin fractions Bei Wen a *, Jing-jing Zhang a, Shu-zhen Zhang a, Xiao-quan Shan a *, Shahamat U. Khan b and Baoshan Xing c a State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 00, China b Department of Chemistry and Biochemistry, MSN E, George Mason University, 00 University Drive, Fairfax, Virginia 00-, USA c Department of Plant and Soil Science, University of Massachusetts, Stockbridge Hall, 0 Campus Center Way, Amherst, MA 00-, USA * Corresponding Author Phone: phone: +--0; Fax: address: bwen@rcees.ac.cn; xiaoquan@rcees.ac.cn 0 The supporting information provides information on the isolation procedure of HA and humin fractions. Text pages: No of table: No of figures:

2 0 Isolation of Humic acid (HA) and humin fractions. HA and humin were isolated from peat soil according to the International Humic Substances Society (IHSS) procedure published on January,. Briefly, to each of six 0-mL glass centrifuge bottles, 0 g of the peat soil was added, and each bottle was filled with 00 ml of distilled water. The ph of the soil suspensions was then adjusted to - with mol/l HCl. After shaking for h, the suspensions were centrifuged (at g, 0 min) and the supernatants were decanted. The solids were then neutralized by mol/l NaOH to ph, and 00 ml of 0. mol/l NaOH was added to re-suspend the solid under a N stream. The suspensions were immediately sealed, shaken overnight, and centrifuged. The supernatants were decanted, acidified with mol/l HCl to ph, and allowed to stand for h before humic acid (HA) and fulvic acid (FA) fractions were separated by centrifugation. The precipitated HA fraction was then re-dissolved in a minimum amount of 0. mol/l KOH under N, to which KCl was added to give approximately 0. mol/l K +. The HA solution was again centrifuged to remove the suspended solids. This dissolution-precipitation procedure was repeated three times. The HA solution was then acidified and transferred to a dialysis bag having a molecular cutoff of Daltons. The material was dialyzed with distilled water until the test of Cl - in water with AgNO was negative. The dialysis step also removed the residual FA in HA. The solid HA was obtained by freeze-drying, and stored in a desiccator until use. The humin fraction was prepared according to the following procedure (). To each six 0-mL polyethylene bottles 0 g of the peat was added, and each bottle

3 0 was filled with about 00 ml of 0. mol/l NaOH solution. The suspensions were equilibrated overnight. Upon centrifugation of the suspensions (at g, 0 min), the supernatants were decanted off, refilled with 00 ml of fresh 0. mol/l NaOH solution, and allowed to re-equilibrate with the remaining peat. This dissolution-precipitation cycle was repeated six times. The resulting humin was rinsed by de-ionized water to remove its alkalinity and then freeze -dried. Humin was fractionated according to MIBK procedure (Rice and MacCarthy, ) (Figure S). Briefly, the following steps were followed: () About g of humin was transferred to a separatory funnel with 00 ml of de-ionized water and 00 ml of MIBK. The mixture was acidified to about ph by concentrated HCl, shaken vigorously for about min, and allowed to equilibrate for about h. The organic matter in humin was extracted and partitioned between the organic and aqueous phases. Lipid and BHA entered the MIBK phase, leaving FA in the aqueous phase. The aqueous phase and precipitate were separated from MIBK phase, and further separated from each other by centrifugation. The MIBK phase was left in the separatory funnel. The FA in aqueous phase was discarded. () The precipitate was transferred to the same separatory funnel. Then, 00 ml of 0. mol/l NaOH was added. The separatory funnel was shaken vigorously and allowed to stand for h. The BHA entered to the alkaline aqueous phase. The aqueous phase and precipitate were separated from MIBK phase, and further separated from each other by centrifugation. The MIBK phase was left in the separatory funnel. () The precipitate was returned to the separatory funnel again. Then, 00 ml of de-ionized water was

4 added. The separatory funnel was shaken vigorously for about min, and allowed to equilibrate overnight. The aqueous phase and precipitate were separated from MIBK phase, and further separated from each other by centrifugation. The BHA in the supernatant was combined with the BHA fraction obtained from step. The precipitate contained IR fraction. The MIBK phase contained lipid fraction. () The aqueous BHA was acidified to ph with M HCl, and BHA was allowed to precipitate overnight. After centrifugation, the BHA precipitate was de-ashed with 0. mol/l HCl / 0. mol/l HF solution, washed with de-ionized water, freeze-dried, gently ground to pass through a 0-µm sieve, and stored for subsequent use. () The MIBK were concentrated to about to ml by a rotary evaporator, freeze dried, gently ground to pass through a 0-µm sieve, and stored in a desiccator until use. () The IR fraction was treated five times with HCl/HF solution (. mol/l HCl -. mol/l HF), rinsed six times with de-ionized water, centrifuged, freeze-dried, gently ground to pass through a 0-µm sieve, and stored for subsequent use for characterization and sorption experiment. The total organic carbon in humin was.% of that in peat soil. The organic carbon contents of BHA, lipid and IR fractions were about.%,.% and.% of that in humin. 0 () Rice, J. A.; MacCarthy, P. Isolation of humin by liquid-liquid partitioning. Sci. Total Environ., /, -.

5 Table S. Elemental compositions, atomic ratios, ash contents, and E/E ratios of SOM fractions a Elemental composition (wt. %) Atomic ratio E/E b Ash Sample C H N S H/C O/C (N+O)/C (wt.%) HA BHA Lipid Na 0. IR Na. a Values are on an ash-free basis. H/C: atomic ratio of hydrogen to carbon. O/C: atomic ratio of oxygen to carbon. (N+O)/C: atomic ratio of sum of nitrogen and oxygen to carbon. Na: not applicable. b E/E of humic acids is the ratio of the absorbance at nm to that at nm.

6 Table S. Integration results of solid-state C NMR spectra and ratios of the sum of aliphatic to aromatic peak area of the SOM fractions Distribution of C chemical shift (ppm) (%) aliphatic aromatic aliphaticity POC Sample Alkyl C O-alkyl C Aromatic C O-aryl C Carboxyl C Carbonyl C C C (%) (0-0) (0-) (-) (-) (-0) (0-0) (%) (%) HA BHA Lipid IR Aliphatic C: total aliphatic carbon region (- ppm). Aromatic C: total aromatic carbon region (-). The POC, percentage of polar organic carbon, was calculated from the peak areas listed above with an equation: POC = (O-alkyl C + O-aryl C + carboxyl C + carbonyl C)/(alkyl C + O-alkyl C +aromatic C + o-aryl C + carboxyl C + carbonyl C) 0. Aliphaticity = aliphatic C (0- ppm)/aromatic C (- ppm).

7 0 0 Aqueous contains FA, discard Aqueous contains BHA Humin Add MIBK and H O, ph of the aqueous layer was adjusted to below by HCl, shake. Add NaOH, shake Add H O, shake Aqueous contains BHA MIBK contains lipid Residue contains mineral Add HCl to precipitate BHA; add HCl-HF to de-ash; wash, freeze-dry and grind Figure S. Sequence of MIBK method. Concentrated, freeze -dry and grind Add HCl-HF to de-ash and wash; freeze-dry and grind

8 0 0 Sorption percentage (%) Sorption time (hour) Figure S. Kinetics of phenanthrene sorption onto the HA ( ), BHA ( ), Lipid ( ) and IR ( ) fractions at the initial concentration of 0. mg/l phenanthrene.

9 0. Percentage of polar organic carbon y = 0.x R = 0.0, p= (N+O)/C Figure S. Relationship between the polarity index ((O+N)/C) and the percentage of polar organic carbon calculated from C NMR spectra of four SOM fractions.

10 0 Percentage of alkyl C in sorbent (%) y =.0x -. R = (N+O)/C Figure S. Relationship between the polarity index ((O+N)/C) and the percentage of alkyl carbon of four SOM fractions.

11 000 Solid-phase concentration (mg/kg) 00 0 E Liquid-phase equilibrium concentration (mg/l) Figure S. Sorption isotherms of phenanthrene by HA ( ), BHA ( ), lipid ( ) and IR ( ) fractions.