Hui Yua, B, Guo-He Huanga, C. *, Huiningxiaob, Lei Wanga, Wei Chenc

Supplementary Information

biodegradation Kinetics of POlycylic armotic hydrocarbons (PAHs) in soil-water systems: combined effects of DOM and biosurfactant enhanced biodegradation

Hui Yua, b, Guo-he Huanga, c. *, HuiningXiaob, Lei Wanga, Wei Chenc

aMOE Key Laboratory of Regional Energy Systems Optimization, S&C Academy of Energy and Environmental Research, North China Electric Power University, Beijing 102206, China

b Department of Chemical Engineering, University of New Brunswick, Fredericton, NB, Canada E3B 5A3

cEnvironmental Systems Engineering Program, Faculty of Engineering and Applied Science, University of Regina, Regina, SK, Canada, S4S 0A2

*Corresponding author Tel.: +1-306-585-4095. Fax: +1-306-585-4855

E-mail: (Guo-he Huang)

3tables

2 figures

DOM Characterization

Table S1shows chemical characterizations of two kinds of DOMs. The concentrations of total organic carbon in compost DOM (2128 mg C/L) was much higher than that in soil DOM (61 mg C/L); while the ash content of compost DOM (37.5%) was lower than that of soil DOM (50.1%). This indicated that organic matter in compost DOM was much higher than that in soil DOM. The N content in compost DOM (2.87%) was much higher than that in soil DOM (0.3%). As for the H/C ratio, the compost DOM exhibited a lower value than soil DOM, suggesting that compost DOM had relative higher aromatic nature. The E4/E6 ratios for soil and composting samples were 12.5 and 7.4, respectively, demonstrating that the compost DOM had a relatively higher molecular weight. When the DOM content in all samples were adjusted to 20 mg C/L, the specific UV absorptions at 254 nm were 1.050 and 0.761 Lmg−1 m−1 for DOMs derived from compost and soil, respectively. The aromatic carbon content in compost DOM was also higher than that in soil DOM.

Table S1 chemical characteristics of two DOM samples

Fig. S1 shows FTIR spectra of the two kinds of DOMs. A broad band at 3200 to 3500 cm-1was assigned to H-bonds and OH groups; the peak of compost DOM showed a broader band than soil DOM. The band at 2870 to 2970 cm-1presented aliphatic carbons, of which two small peaks at 2964 and 2930 cm-1 were assigned to asymmetricalstretching of C-H in methyl and methylene groups, respectively. For soil DOM, a small peak at 2873 cm-1 was assigned to symmetrical stretching of C-H in methyl groups; a strong absorbance at 1420 cm-1 exhibited paraffinic characteristics. For the spectrum of compost DOM, there was a distinct peak at 1603 cm-1, implying polymer groups with C=C stretching vibrations in aromatic or vinyl groups and vibrations of COO- or H-bonded C=O. while there was no such kind of peak presence in the spectrum of soil DOM. This implied higher aromatic properties of compost DOM.

The 1HNMRspectraof twoDOMs are shown in figure S2. The peak shape of soil DOM showed simple and well-defined peaks, while the compost DOM presented complex and unresolved peaks. The identified peaks in the 1H NMR spectra were assigned to aliphatic H in methyl protons and main-chain methylene (0.8-1.5 ppm)

, carbonyl group in an acid or ester at β-C (1.8 ppm), ethers or hydroxyl group (3.6 ppm), esters (4.0 ppm), water (4.8 ppm) and carboxyl group (8.4 ppm). Both of these two samples showed these identified peaks with different responses. The soil DOM showed a strong peak in 3.6 ppm, which was attributed to protons to ethers or hydroxyl group; in comparison, the peak of compost DOM was unclear. Besides, for the spectrum of compost DOM, there were multiple peaks at 1.8 to 3.6 ppm. This indicated the component of high molecules of polymers; H may be bonded to aromatic C in methine group or bounded to O or N in aliphatic C. However, the detailed composition of the polymers needed to be further analyzed. In addition, there was a broad but weak peak at 6 to 8 ppm in the spectra of compost DOM, which was assigned to protons in aromatic and conjugated double-bound signals. In comparison, few signals in this band range were observed from the soil DOM. This also suggested relatively higher aromaticity of compost DOM.

(a)

(b)

Figure S1. FTIR spectra of DOM samples derived from (a)soil and (b)compost

NMR analysis

The difference of the DOMs was furtheranalyzedthrough1H NMR. The two extracted DOM samples also exhibited different peak shapes from the 1H NMR spectra (Figure S4). The peak shape of soil DOM showed simple and well-defined peaks, while the compost DOM presented complex and unresolved peaks, which indicated different compositions in the functional groups of DOM. The identified peaks in the 1H NMR spectra were assigned to aliphatic H in methyl protons and main-chain methylene (0.8-1.5 ppm), carbonyl group in an acid or ester at β-C (1.8 ppm), ethers or hydroxyl group (3.6 ppm), esters (4.0 ppm), water (4.8 ppm) and carboxyl group (8.4 ppm). Both of these two samples showed these identified peaks with different responses. The soil DOM showed a strong peak in 3.6 ppm, which was attributed to protons to ethers or hydroxyl group; in comparison, the peak of compost DOM was unclear. Besides, for the spectrum of compost DOM, there were multiple peaks at 1.8 to 3.6 ppm. This indicated the component of high molecules of polymers; H may be bonded to aromatic C in methine group or bounded to O or N in aliphatic C. However, the detailed composition of the polymers needed to be further analyzed. In addition, there was a broad but weak peak at 6 to 8 ppm in the spectra of compost DOM, which was assigned to protons in aromatic and conjugated double-bound signals. In comparison, few signals in this band range were observed from the soil DOM. This also suggested relatively higher aromaticity of compost DOM.

(a)

(b)

Figure S2. 1H NMR spectra of DOM samples derived from (a) soiland (b)compost

Table S2 Summary of biodegradation experiment design

Bulk means original soil and without DOM removal

Kinetic model

For comparison of first order equation, a modified Monod equation or Michaelis-Menten kinetic model was applied to describe the PAH consumption rate [1-3].

(S1)

where C is the system concentration of PAH measured over time; t is the sampling time; Ks is the half-saturation constant for growth; KP is the equilibrium partition coefficient between soil and aqueous phase; Vmaxis the maximum degradation rate, which depends upon the total concentration of active enzyme in the bacteria, and Vmax can be expressed as, where µmax is the maximum specific growth rate and X0 is the initial cell density. The above model was the sole substrate Monod model which can be described as a no-interaction model. It represents a case where a compound in a mixture behaves as if it were the only compound without accounting for the effects from other existing substrates. When the mixture of substrates exhibit competition, the competitive inhibition kinetic model is applied[1,4].

, j ≠i(S2)

where Ci is the concentration of substrate i; Cj is the concentration of substrate j, , ,which can be defined as the inhibition constant, wherein KSi is the half-saturation constant for substrate i, and KSj is the half-saturation constant for substrate j; kj is the apparent first order rate constant; n is the number of competitive inhibitors.

EquationS2 can be extended for any number of components provided the compounds exhibit competitive inhibition kinetics. Thus, KSj represented a constant, while Ksi, qmax,i and Ci were fitting parameters. In this study, Equation S2 is specified as

(S3)

and

(S4)

Kinetic Equations S3 and S4 were integrated using the fourth-order Runge-Kutta numerical algorithm. Kinetic parameters could be derived through non-linear regression analysis using software Origin and 1stOpt, based on the Levenberg–Marquardt and Universal Global Optimization Algorithm. The biokinetic parameters of PHE and PYR fitting with two kinetic models are presented in Table S3.

Table S3 Comparison of kinetic parameters for biodegradation of PHE and PYR in soil-water systems

S1

References

[1]Desai AM, Autenrieth RL, Dimitriou-Christidis P, McDonald TJ. 2008. Biodegradation kinetics of select polycyclic aromatic hydrocarbon (PAH) mixtures by Sphingomonaspaucimobilis EPA505. Biodegradation 19:223-233.

[2]Lawrence AW, Mccarty PL. 1970. Unified Basis for Biological Treatment Design and Operation.J SanitEngDivAsce 96:757-778.

[3]Simkins S, Alexander M. 1984. Models for Mineralization Kinetics with the Variables of Substrate Concentration and Population-Density.Appl Environ Microbiol 47:1299-1306.

[4]Lotfabad SK, Gray MR. 2002. Kinetics of biodegradation of mixtures of polycyclic aromatic hydrocarbons.ApplMicrobiolBiot 60:361-365.

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