Supplementary information

Plant-assisted rhizoremediation of decabromodiphenyl ether for e-waste recycling area soil of Taizhou, China

Yan Hea,*, Xinfeng Lia, Xinquan Shena, Qin Jianga, Jian Chenb, Jiachun Shia, Xianjin Tanga, Jianming Xu a,*

a College of Environmental and Natural Resource Sciences, Zhejiang Provincial Key Laboratory of Subtropical Soil and Plant Nutrition, Zhejiang University, Hangzhou 310058, China

b Agricultural & Forestry Bureau of Wenling, Zhejiang Province, Wenling 317500, China

* Corresponding Author. E-mail: ; ; Phone: +86-571-8898-2065

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Details for the design of rhizobag

The dimension of the rhizobag was 200×100×180 (length × width × height, mm), which was made by nylon mesh (< 25 μm). The design of rhizobag successfully prevents roots from entering the surrounding nonrhizosphere soils as well as keeping the rhizosphere soils separated, while permitting the transfer of soil microfauna and root exudates between the compartments.

Preparation for the freshly BDE-209 spiked soil

Preparation for the freshly spiked soil was basically described by Huang et al. (2010). Briefly, BDE-209 solution, using 100 ml methylbenzene/acetone (1:10, V/V) as the solvent, was mixed uniformly with an aliquot of polluted soil (20 kg, 10% of potting soil). The spiked soil was thereafter placed under a fume hood to let the solvent vaporize for 12 h, and then continuously tumbled with the rest of the potting soil for 2 h at room temperature to ensure efficient mixing. The freshly spiked polluted soil was then allowed to dry in a fume hood in the dark until the solvent had volatilized completely, shaken for 30 min every day, equilibrated, and incubated in the dark for a week at room temperature.

Analytical methods for soil PLFAs

Since a lot of soil samples were consumed for the analyses of the BDE-209 residues and soil redox parameters, the rest were not enough for conducting a separate extract of PLFAs for each replicate samples. Thus, PLFAs were extracted from freeze-dried soil samples of adequately blended mixture of three duplicates of each treatment, with Bligh-Dyer extracting solution consisting of chloroform-methanol-citrate buffer (1:2:0.8, V/V/V) that was modified from He et al. (2009).

Pooled supernatants from two repeated extractions were separated into two phases by the addition of chloroform and the above extracting buffer. The lipid-containing phase was transferred to 10 ml burned glass test tubes, dried under N2, dissolved in 600 ml of chloroform, and transferred onto a silica gel solid phase extraction cartridge (500mg, 3ml; Supelco, Bellofonte, PA). Following the elution of neutral lipids and glycolipids with 10 ml chloroform and 10 ml acetone, respectively, phospholipids were eluted with 8 ml methanol and dried under N2. Methylmyristate fatty acid (19:0) was added as internal standard, and PLFAs were subsequently derivatized by mild-alkali methanolysis. The resulting fatty acid methyl esters were then separated by an Agilent 6890II GC fitted with a MIDI Sherlock® microbial identification system (Version 4.5, MIDI, USA). Individual fatty acids were designated in terms of the total number of carbon atoms : number of double bonds, followed by the position (ω) of the double bond from the methyl end of the molecule. The prefixes ‘‘a’’ and ‘‘i’’ indicates anteiso- and iso-branching, respectively, ‘‘10Me’’ describes a methyl group on the tenth carbon atom from the carboxyl end of the molecule, and ‘‘cy’’ represents a cyclopropane fatty acid. The PLFA data presented were the average of twice analyses.

Analytical methods for soil DOC, the activities of soil oxido-reductases, and some soil redox relevant biochemical indexes

To determine the concentration of soil dissolved organic carbon (DOC), about 2 g equivalent freeze-dried soils were extracted with 10 ml Milli-Q water by shaking at 200 r min-1 under 20 oC for 30 min. The supernatant after centrifugation was then filtered through a 0.45 μm filter paper, and finally measured using an automated total organic carbon analyzer (Multi N/C 3100, Analytikjena AG, Jena, Germany).

The activities of soil oxido-reductases (catalase and dehydrogenase), and some soil redox relevant biochemical indexes, including NH4+, NO3+, Fe2+ and Fe3+, were also analyzed. Catalase activity was determined by back-titrating residual H2O2 with KMnO4 which was described by Stepniewska et al. (2009). Dehydrogenase activity was analyzed after incubation soil samples in TTC-glucose-Tris buffer solution at 37oC in the dark for 24 h (Liu et al., 2011). The NH4+ and NO3+ concentrations were measured using a continuous flow analyzer (TRAACS 2000, Bran and Luebbe, Norderstedt, Germany) after soil samples were extracted with KCl solution at a ratio of 1:10 (w/v) (Zhou et al., 2014). The concentration of Fe2+ and Fe3+ was measured by a colorimetric assay according to Hayat et al. (2011).

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Table S1. The 22 identified phospholipid fatty acids (PLFAs) and their attributive microbial species as well as their correlations with BDE-209 percent removal.

PLFA / Sa / Br / M / C / I / AI / H / B / G+ / G- / F / A / AMF / Marker / Rb
12:0 / √ / 0.459*
i14:0 / √ / √ / √ / G+ / 0.505*
14:0 / √ / 0.340
i15:0 / √ / √ / √ / √ / G+ / 0.525*
a15:0 / √ / √ / √ / √ / G+ / 0.540*
15:0 / √ / √ / 0.581**
16:0 / √ / -0.071
i16:0 / √ / √ / √ / √ / G+ / 0.087
a16:0 / √ / √ / -0.319
16:1ω5c / √ / √ / √ / G+; F / 0.502*
10Me16:0 / √ / G+; AMF / 0.024
i17:0 / √ / √ / √ / √ / G+ / -0.248
a17:0 / √ / √ / √ / √ / G+ / 0.048
cy17:0 / √ / √ / √ / G- / 0.187
17:0 / √ / √ / -0.088
10Me17:0 / √ / AMF / -0.233
18:1ω9c / √ / F / 0.070
18:1ω7c / √ / √ / √ / G- / 0.656**
18:0 / √ / -0.051
10Me18:0 / √ / AMF / -0.278
cy19:0ω8c / √ / -0.159
20:0 / √ / 0.166

√ This PLFA was involved in the corresponding microbial taxa.

a S: saturated; Br: branched; M: monounsaturated; C: cyclopropyl-; I: iso-; AI: anteiso-; H: hydroxyl-; B: bacteria; G+: gram-positive bacteria; G-: gram-negative bacteria; F: fungi; A: actinomycetes; AMF: arbuscular mycorrhizal fungi.

b R: BDE-209 dissipation rates

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References

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