SUPPORTING INFORMATION. How rice (Oryza sativa L.) responds to elevated As under different Si-rich soil amendments

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1 SUPPORTING INFORMATION How rice (Oryza sativa L.) responds to elevated As under different Si-rich soil amendments William A. Teasley, Matt A. Limmer, Angelia L. Seyfferth* Department of Plant and Soil Sciences, University of Delaware, Newark, DE 19716, USA. *Corresponding author: Angelia L. Seyfferth, 18 Pages, 11 Figures, 7 Tables S1

2 Table of Contents Figure S1. Adsorption Isotherm of Non-spiked Soil Figure S2. Sequential Extraction of Soil-As Phases Figure S3. Flux Chamber Figure S4. Plant Biomass Figure S5. Plant As and Si concentrations Figure S6. Linear combination fitting of XAS Spectra Figure S7. Porewater As concentrations Figure S8. Porewater ph, Eh, and Fe concentrations Figure S9. CO 2 and CH 4 Flux over Rice Growth Figure S10. Mass of S, P, and K in Rice Shoots Figure S11. Porewater and Root Calcium Table S1. Extractable Plant Nutrients in Soil Table S2. CBD- and AAO-extractable As, Si, and Fe Table S3. Elemental Analysis of Husk and Ash Amendments Table S4. SRM Rice Flour 1568a Recoveries Table S5. Comparison of As species recoveries in SRM Rice Flour 1568a Table S6: Results of XANES Analysis of As Species in Fe plaque Table S7: Cumulative Emissions of CH 4 and CO 2 References S3 S4 S5 S6 S7 S8 S9 S10 S11 S12 S13 S14 S14 S15 S15 S16 S16 S17 S18 S2

3 Figure S1: Adsorption isotherm of non-spiked soil to determine appropriate As loading for soil spiking. Solutions of µm As (80:20 As i (III):As i (V) molar ratio) were mixed 30:1 (w/w) with soil in an acetate buffered solution (ph 6) for 24 h. A polynomial curve was fit to the data and used to calculate the As loading rate. S3

4 Figure S2: Average extractable As (± SD, n =2) from different soil-as phases of -As-control (no added As or Si) soil and +As post-experiment soil. Statistical tests were performed separately for each soil-as phase and only for post-experiment soils. Significant differences (p < 0.05) between treatments are indicated by different letters. Soil-As phases with no lettering were found to have no significant differences between treatments. S4

5 Figure S3: A dark gas flux chamber was constructed using 8 inch diameter PVC pipe, a PVC pipe cap, and push-connect fittings. Three 12-volt computer fans were secured to the inside of the chamber and powered by an AC adapter. Junctions were sealed with neoprene and silicone sealant. The pot-chamber-greenhouse gas analyzer formed a closed system where accumulating gases within the chamber were measured in real-time over 3 minutes. Due to a large chamber size (0.045 m 3 ), a 45 s deadband was removed and the remaining 135 s was used to calculate flux with the following equation 1 : Equation S1: ffffff = dddd dddd VV cc PP AA cc RR (TT ss ) where fcx is the flux of CO 2 or CH 4, dc/dt is the change in concentration with time measured by the LGR (ppm s -1 ), V c is the system volume (0.045 m 3 ), A c is the area of the pot soil ( m 2 ), P is atmospheric pressure ( kg m s -2 ), R is the ideal gas law constant ( kg m 2 μmol -1 K -1 s -2 ), and T s is the temperature of standing water within the pots in C. S5

6 A BC C BC B c bc a b bc b ab a ab ab Figure S4: Average (± standard deviation (SD), n=4) grain, husk, straw and root biomass (dry weight per pot) of rice grown in -As-control (no added As or Si), +As-control (added As but no Si amendment), or +As soil amended with CaSiO 3, Husk, or Ash. Different uppercase letters denote significant differences (p < 0.05) in average aboveground biomass (sum grain, husk, and straw) between treatments and lowercase letters denote significant differences in straw or root biomass between treatments. S6

7 Figure S5. Average (± standard deviation, n = 4) total As (A) and Si (B) in husk, straw, and plaque-free roots of rice grown in soil spiked with As (+As-control) or soil spiked with As and amended with CaSiO 3, Husk, or Ash and irrigated with Ascontaminated water. Letters denote significant differences (p < 0.05) between treatments within each plant organ. S7

8 Figure S6: Linear combination fits of k 3 weighted Fe EXAFS spectra (A) and As k-edge spectra (B) of root Fe-plaque that was removed from roots via sonication and concentrated on a nitrocellulosic filter membrane. Each fit is one replicate chosen as a representative sample from the +As-control and treatment groups. S8

9 Figure S7: Porewater concentrations of total As (A), As i (III) (B), DMA (C), and As i (V) (D). Total As expressed as average of 4 replicates per treatment group (± 95% confidence interval). As species expressed as individual measurements (n = 2 per treatment per sampling date). S9

10 Figure S8: Average (± 95% confidence interval, n = 4) porewater ph (A), redox (B), and concentrations of Fe 2+ (C) and total Fe (D) for paddy rice exposed to different Si treatments under elevated soil As. S10

11 Figure S9. Average flux (± 95% confidence interval, n = 4) of CO 2 (A) and CH 4 (B) measured weekly over 120 days of rice growth of rice grown in soil spiked with As (control) or soil spiked with As and amended with CaSiO 3, fresh husk, or rice husk ash and irrigated with As. Flux was measured dynamically and calculated using 135 second of gas concentrations measured at 1 Hz. S11

12 Straw S (g kg -1 ) b ab a ab D 0.2 Straw P (g kg -1 ) b b a b E 0 20 a F Straw K (g kg -1 ) b b ab 0 Figure S10: Average (± SD) mass of S (A), P (B), and K (C) in aboveground plant organs (straw, husk, and grain) and corresponding straw concentrations of S (D), P (E) and K (F). Significant differences (p < 0.05) between treatments indicated by different letters. Significant differences were observed in aboveground plant S (F = 8.56, p = 0.026), P (F = 14.14, p = ), and K (F = 15.19, p = ), and in straw concentrations of S (F = 6.52, p = 0.007), P (F = 8.71, p = 0.002), and K (F = 4.59, p = 0.023). S12

13 Figure S11: Porewater Ca 2+ (A) (± 95% confidence interval, n = 4) over rice growth and Ca concentrations in plaque-free roots (B) (average ± SD, n = 4). Significant differences (p < 0.05) are indicated by different letters. Amending soils with CaSiO 3 increased porewater Ca 2+ concentrations compared to the other groups (A), which led to significantly elevated Ca concentrations in roots (F = 54.05, p < ) (B), but not in aboveground tissues (data not shown). S13

14 Table S1: Average (± SD, n = 3) extractable nutrients of untreated soil. CaCl 2 BaCl 2 Acetic acid (mg kg -1 ) (mg kg -1 ) (mg kg -1 ) B 2.6 ± ± ± 0.4 Ca NM 483 ± ± 10 Cu BDL BDL BDL Fe BDL BDL 1.6 ± 0.04 K 31 ± 2 89 ± 2 94 ± 2 Mg 111 ± ± ± 5 Mn 4 ± ± ± 0.3 Na 66 ± ± ± 4 P BQL BDL 9.5 ± 0.3 S 13 ± ± ± 0.5 Si 3.2 ± ± ± 0.2 Zn 1 ± ± ± 0.6 NM - Not measured BDL - Below detection limit BQL - Below quantification limit Table S2. Average (± SD, n = 3) ammonium oxalate (AAO) and citrate-bicarbonate-dithionite (CBD) extractable Si, As, and Fe in untreated soil. AAO (mg kg -1 ) CBD (mg kg -1 ) Si 59 ± ± 14 Fe 1570 ± ± 340 As 1.41 ± ± 0.18 S14

15 Table S3 Average elemental concentrations (± standard deviation, n = 3 unless otherwise noted) of Husk and Ash amendments used in this study as analyzed by XRF (Si) or ICP-OES or ICP-MS (As) after acid digestion. Husk Ash (mg kg -1 ) (mg kg -1 ) As a 0.26 ± ± 0.02 Ca 616 ± ± 92 Fe b K 1740 ± ± 278 Mg 301 ± ± 50 Mn 209 ± ± 23 Na 31 ± ± 8 P 185 ± ± 82 S 464 ± ± 6 Zn 13 ± 1 18 ± 1 Si b a analyzed by ICP-MS b analyzed by XRF (n=1) Table S4: Average concentration (± standard deviation) and recoveries of National Institute of Standards and Technology standard reference material 1568a (rice flour). Element mg kg -1 Recovery (% ) n As a ± Ca 124 ± K 1180 ± Mg 482 ± Mn 18.7 ± P 1530 ± S 1140 ± Zn 18.5 ± a analyzed with ICP-MS S15

16 Table S5: Measured As species in SRM 1568a (rice flour) in the present study and in a variety of other studies by different researchers 2-7. Source As i (mg/kg -1 ) DMA (mg/kg -1 ) MMA (mg/kg -1 ) Present study Maher et al Jackson et al Williams et al Heitkemper et al D'amato et al Kohlmeyer et al Table S6: Linear combination fitting results of normalized As K-edge XANES spectra and goodness of fits (R value) obtained on root-system Fe plaque. Treatment Percent of fitted species R value As i (III) As i (V) +As-control CaSiO Husk Ash S16

17 Table S7: Cumulative emissions (± SD, n=4) of CH 4 (CO 2 equivalents based on 100-year GWP 8 ) and CO 2. Cumulative Cumulative Cumulative Treatment CH 4 Flux CH 4 (g CO 2 eq. CO 2 Flux (g m d -1 ) m d -1 ) (g m d -1 ) +As-control 51.7 (± 7.4) b 3980 (± 570) b 1690 (± 99) b CaSiO (± 3.1) ab 4500 (± 240) ab 1900 (± 91) a Husk 64.3 (± 2.4) a 4950 (± 180) a 1880 (± 72) a Ash 48.5 (± 7.4) b 3740 (± 570) b 1790 (± 94) ab Values followed by the same letter are not statistically significant at the 0.05 level. S17

18 References 1. Pumpanen, J.; Kolari, P.; Ilvesniemi, H.; Minkkinen, K.; Vesala, T.; Niinisto, S.; Lohila, A.; Larmola, T.; Morero, M.; Pihlatie, M.; Janssens, I.; Yuste, J. C.; Grunzweig, J. M.; Reth, S.; Subke, J. A.; Savage, K.; Kutsch, W.; Ostreng, G.; Ziegler, W.; Anthoni, P.; Lindroth, A.; Hari, P., Comparison of different chamber techniques for measuring soil CO2 efflux. Agr Forest Meteorol 2004, 123, (3-4), D'Amato, M.; Forte, G.; Caroli, S., Identification and quantification of major species of arsenic in rice. J AOAC Int 2004, 87, (1), Heitkemper, D. T.; Vela, N. P.; Stewart, K. R.; Westphal, C. S., Determination of total and speciated arsenic in rice by ion chromatography and inductively coupled plasma mass spectrometry. J Anal Atom Spectrom 2001, 16, (4), Jackson, B. P.; Taylor, V. F.; Karagas, M. R.; Punshon, T.; Cottingham, K. L., Arsenic, Organic Foods, and Brown Rice Syrup. Environ Health Perspect 2012, 120, (5), Kohlmeyer, U.; Jantzen, E.; Kuballa, J.; Jakubik, S., Benefits of high resolution IC-ICP- MS for the routine analysis of inorganic and organic arsenic species in food products of marine and terrestrial origin. Anal Bioanal Chem 2003, 377, (1), Maher, W.; Foster, S.; Kirkowa, F., Measurement of inorganic arsenic species in rice after nitric acid extraction by HPLC-ICPMS: Verification using XANES. Environ. Sci. Technol 2013, 47, Williams, P. N.; Price, A. H.; Raab, A.; Hossain, S. A.; Feldmann, J.; Meharg, A. A., Variation in arsenic speciation and concentration in paddy rice related to dietary exposure. Environ. Sci. Technol 2005, 39, (15), Myhre, G., D. Shindell, F.-M. Bréon, W. Collins, J. Fuglestvedt, J. Huang, D. Koch, J.-F. Lamarque, D. Lee, B. Mendoza, T. Nakajima, A. Robock, G. Stephens, T. Takemura and H. Zhan, Anthropogenic and natural radiative Forcing. In Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change, Stocker, T. F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M. Midgley, Ed. Cambridge, United Kingdom and New York, NY, USA, S18