Determining time-weighted average concentrations of nitrate and. ammonium in freshwaters using DGT with ion exchange membrane-based

Transcription

1 Electronic Supplementary Material (ESI) for Environmental Science: Processes & Impacts. This journal is The Royal Society of Chemistry 2016 Determining time-weighted average concentrations of nitrate and ammonium in freshwaters using DGT with ion exchange membrane-based binding layers Jianyin Huang a, William W. Bennett a, David T. Welsh a *,and Peter R. Teasdale a a Environmental Futures Research Institute, Griffith University, Gold Coast campus, QLD 4215, Australia * Corresponding Author: d.welsh@griffith.edu.au. Tel: +61 (07) Fax: +61 (07)

2 Contents Figure S1. Mass of NH 4 -N accumulated by CMI-DGT over 24 h at various ionic strength solutions. Figure S2. Relationship between the diffusion coefficient of NH 4 -N and conductivity for CMI-DGT. Figure S3. Effects of different concentrations of Na + ( ), K + ( ), Ca 2+ ( ) and Mg 2+ ( ) on NH 4 -N uptake. Figure S4. Capacity of AMI-DGT for NO 3 -N and CMI-DGT for NH 4 -N. Table S1. The recipe of synthetic freshwater (ph = 7.20 ± 0.05). Table S2. Comparison of the uptake and elution efficiencies for binding membranes and hydrogels. Table S3. Comparison of uptake of binding membranes and hydrogels for different ph. Table S4. The corresponding D values of CMI-DGT and PrCH for NH + 4 at different conductivity (0.0001, and 0.01 mol L -1 NaCl). Table S5. Trigger values based on Queensland Water Quality Guidelines. Table S6. NO 3 -N concentrations at Loders Creek: C SOLN, C A520E-DGT and C AMI-DGT. Table S7. NH 4 -N concentrations at Loders Creek: C SOLN, C PrCH-DGT and C CMI-DGT. Table S8. NO 3 -N concentrations at Saltwater Creek: C SOLN, C A520E-DGT and C AMI-DGT. Table S9. NH 4 -N concentrations at Saltwater Creek: C SOLN, C PrCH-DGT and C CMI-DGT. 2

3 Table S1. The recipe of synthetic freshwater in 8 L (ph = 7.20 ± 0.05 and conductivity = 0.23 ms cm -1 ). Synthetic freshwater with different ionic strengths were prepared by proportionally changing 2 the concentrations of ions (e.g ms cm -1 = 5 the amount of the ions in the new recipe, 0.40 ms cm -1 = approximately 2 the amount). Finally, the concentration of HCO - 3 was <2 mmol L -1 to maintain the ph (7.0 ± 0.5). Chemicals Concentration (mmol L -1 ) CaCl 2.2H 2 O Na 2 SO KCl NaCl MgCl 2.6H 2 O HCO

4 AMI and CMI membranes had high uptake and elution efficiencies for NO 3 -N and NH 4 -N, respectively. Table S2. Comparison of the uptake and elution efficiencies for binding membranes and hydrogels. Binding agents AMI A520E 1 CMI PrCH 2 Uptake efficiency (%) Elution efficiency (%) 96.7 ± ± ± ± ± ± ± ± 5.3 The ratios of C AMI-DGT :C SOLN and C CMI-DGT :C SOLN were between 0.87 and 1.06, suggesting that the binding layer membranes produced similar results to the resin binding gels. Table S3. Comparison of the uptake of binding membranes and hydrogels for different ph. ph C AMI DGT/C SOLN C A520E DGT/C SOLN C CMI-DGT/C SOLN C PrCH DGT/C SOLN ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± 0.03 Similar NH + 4 diffusion coefficients were found in CMI-DGT and PrCH-DGT. 2 Mass of accumulated NH 4 -N on CMI-DGT decreased with increasing conductivity (Figure S3). High diffusion coefficient of NH + 4 was found at low ionic strength (conductivity) and decreased with increasing conductivity (Figure S2). 4

5 Ammonium (NH 4 -N) Accumulated ( g) Deployment Time (h) Figure S1. Mass of NH 4 -N accumulated by CMI-DGT over 24 h at various ionic strength solutions. The solid line is a regression line. Experimental conditions: NH 4 -N = 1.5 ± 0.21 mg L -1 ; conductivity = ± ms cm -1 ( ), ± ms cm -1 ( ); ± ms cm -1 ( ); ± ms cm -1 ( ); 1.0 ± ms cm -1 ( ). 5

6 Diffusion Coefficient (cm 2 s -1 ) Conductivity ( S cm -1 ) Figure S2. Relationship between the diffusion coefficient of NH 4 -N and conductivity for CMI-DGT ( ) and PrCH-DGT ( ) using an agarose diffusive layer. Data were modified according to the Stokes-Einstein equation to 25 C. ph = 7.07 ± The trend line for the exponential relationship between diffusion coefficient (D) and conductivity for CMI-DGT was R 2 = , D = Conductivity and PrCH-DGT was R 2 = , D = Conductivity Table S4. The corresponding D values of CMI-DGT and PrCH for NH 4 + at different conductivity (0.0001, and 0.01 mol L -1 NaCl). Conductivity (µs cm -1 ) D values (10-5 ) CMI PrCH

7 C DGT /C SOLN Cation Concentration (mol L -1 ) 0.1 Figure S3. Effects of different concentrations of Na + ( ), K + ( ), Ca 2+ ( ) and Mg 2+ ( ) on NH 4 -N uptake by CMI-DGT. Data are mean values (n = 3) ± 1 standard deviation. Experimental conditions: NH 4 -N concentration = 1.5 ± 0.1 mg L -1 ; time = 24 h; ph = 7.0 ± 0.37 for mol L -1 Na +, K +, Ca 2+ and Mg 2+, ph = 5.9 ± 0.28 for mol L -1 Ca 2+ and Mg 2+. C DGT :C SOLN for NH 4 -N was between 0.84 and 1.03 at mol L -1 of Na +, K +, Ca 2+ and Mg 2+. C DGT :C SOLN was 1.13 and 0.94 at 0.01 mol L -1 Na + and K +, respectively. As the ionic strength increased, the C DGT :C SOLN ratio for NH 4 -N tended to decrease in the presence of all cations. At 0.01 mol L -1 Ca 2+ and Mg 2+, C DGT :C SOLN ratio was only 0.18 and 0.30, respectively. CMI-DGT was not quantitative at 0.1 mol L -1 for any of the cations. 7

8 Membrane DGTs have high binding capacities for NO 3 -N (921 ± 88 μg) and NH 4 -N (3512 ± 51 μg). Mass of NO 3 -N on Adsorbent ( g) A Deployment Time (h) Mass of NH 4 -N on Adsorbent ( g) B Deployment Time (h) Figure S4. (A) Binding capacity of AMI-DGT ( ) for NO 3 -N and (B) CMI-DGT ( ) for NH 4 -N. Data are mean values (n = 3) ± 1 standard deviation. Experimental conditions: (A) initial NO 3 -N = 13.6 mg L -1, final NO 3 -N = 12.3 µg L -1 ; temperature = 24.1 ± 0.5 C; (B) initial NH 4 -N = 33.1 mg L -1, final NH 4 -N = 30.6 mg L -1 ; temperature = 23.5 ± 0.4 C; both conductivities are between ms cm -1 and volumes are 8 L. 8

9 Table S5. Trigger values based on Queensland Water Quality Guidelines. Ecosystem type NO x -N (µg L -1 ) NH 4 -N (µg L -1 ) PO 4 -P (µg L -1 ) Upland stream Lowland stream Freshwater lakes/ reservoirs Table S6. NO 3 -N concentrations (μg L -1 ) at Loders Creek: C SOLN, C A520E-DGT and C AMI-DGT. Concentrations are presented as mean values (n = 3) ± 1 standard deviation. Time C SOLN C AMI-DGT C A520E-DGT C AMI-DGT: C A520E-DGT 8-11 Dec ± ± ± ± Dec ± ± ± ± Dec ± ± ± ± 0.01 Table S7. NH 4 -N concentrations (μg L -1 ) at Loders Creek: C SOLN, C PrCH-DGT and C CMI-DGT, Concentrations are presented as mean values (n = 3) ± 1 standard deviation. Time C SOLN C CMI-DGT C PrCH-DGT C CMI-DGT: C PrCH-DGT 8-11 Dec ± ± ± ± Dec ± ± ± ± Dec ± ± ± ±

10 Table S8. NO 3 -N concentrations (μg L -1 ) at Saltwater Creek: C SOLN, C A520E-DGT and C AMI-DGT. Concentrations are presented as mean values (n = 3) ± 1 standard deviation. Time C SOLN C AMI-DGT C A520E-DGT C AMI-DGT: C A520E-DGT Jan ± ± ± ± Jan - 2 Feb ± ± ± ± Feb ± ± ± ± 0.24 Table S9. NH 4 -N concentrations (μg L -1 ) at Saltwater Creek: C SOLN, C PrCH-DGT and C CMI-DGT. Concentrations are presented as mean values (n = 3) ± 1 standard deviation. Time C SOLN C CMI-DGT C PrCH-DGT C CMI-DGT: C PrCH-DGT Jan 22.7 ± ± ± ± Jan - 2 Feb 17.0 ± ± ± ± Feb 15.2 ± ± ± ± 0.09 References 1. J. Huang, W. W. Bennett, P. R. Teasdale, S. Gardiner and D. T. Welsh, Anal. Chim. Acta., 2016, 923, J. Huang, W. W. Bennett, D. T. Welsh, T. Li and P. R. Teasdale, Anal. Chim. Acta., 2016, 904,