Arsenic speciation in Soil and Sediment

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					Arsenic speciation in
 Soil and Sediment

   Myron Georgiadis


             Florida International University
             TAG Meeting January 10, 2003
           Backgrounds
Leaching occurs from CCA-Treated Wood
into soil and sediments
Traditional methods for arsenic analysis in
soil - Digestion
Develop an extraction method for Arsenic
in soils and sediments while preserving
the species.
     Method Development
Reference Soil PACS2
    PACS2 – Marine Sediment Reference Material
    from National Research Council Canada
Extraction Solution: pH, Buffer Capacity,
Chemical Interactions
PACS2 was extracted with a phosphate
buffer.
Analyzed by HPLC-HG-AFS.
Arsenic Concentration vs Time
                 9
                 8
                           As(III)   As(V)
                 7
                 6
Conc. ( m g/g)




                 5
                 4
                 3
                 2
                 1
                 0
                       1             3             5              12   24
                                         Time Extracted (hours)

                     - Conversion of As(III) to As(V).
                     - Reabsorption back into soil.
           Approaches
Potential Effect of Fe and Mn
Extract with EDTA to remove metals from
solution which may aid in the
interconversion
Provide a reducing environment using
hydroxylamine
Use of Complexing Reagent NaDDC and
APDC
Potential Effect of Fe and Mn

               2.50
                                                    As(III)   As(V)
               2.00
Conc (m g/g)




               1.50


               1.00


               0.50


               0.00
                      1   3          5         12               24
                          Extraction Time (Hours)
                     Extraction with EDTA
                      PACS2 Extraction with PO4 + EDTA


               9.0
               8.0
               7.0                 As(III)   As(V)
Conc (m g/g)




               6.0
               5.0
               4.0
               3.0
               2.0
               1.0
               0.0
                      1        3             5       12   24
                                Time Extracted (Hours)
                     Use of Hydroxylamine

            5.E+06
            4.E+06                As(III)    As(V)
            4.E+06
            3.E+06
Peak Area




            3.E+06
            2.E+06
            2.E+06
            1.E+06
            5.E+05
            0.E+00
                          0                          24
                              Time (Hours)
               Use of Hydroxylamine
              Arsenite stability over a period of 24 hours with
                      and without 1% Hydroxyl Amine
        As(III)           50ppb Spiked Arsenite
                                                       PO4 NH2OH
             70.0
             60.0
Conc (ppb)




             50.0
             40.0
             30.0
             20.0
             10.0
              0.0
                          0                        24
                                 Time (Hours)
    Complexing Reagents

Sodium diethyldithiocarbamate
trihydrate (NaDDC)
Ammonium pyrrolidine
dithiocarbamate (APDC)
 Arsenic Concentrations in
Marine Organisms Attached to
     CCA-treated Wood
Organisms analyzed: soft coral, hydroids,
crabs, barnacles, orange sponge, yellow
sponge, black sponge, oyster, tube worm,
amphipods, starfish, unknown invertebrate
(black outer layer, soft inner)
Hydroids and amphipods showed elevated
arsenic concentration for those collected from
on CCA-wood
                  As Speciation: standards
                [2 ]   T IC :4 5 5 5 8 .D    [C o u n t]

  5 0 0 0




                                                      10 ppb standards

                        1


  2 5 0 0
                                                                                              5
                                                                        4
                                     3
                               2



s e c ->    0          2 0 0       4 0 0   6 0 0   8 0 0   1 0 0 0   1 2 0 0   1 4 0 0   1 6 0 0   1 8 0 0   2 0 0 0




      1. AsB; 2. As(III); 3. DMA; 4. MMA; 5. As(V)
As speciation: Hydriods on Concrete
               Pilings
                [2 ]   T IC :4 5 5 8 4 .D   [C o u n t]

  2 0 0 0



                  AsB          Unknown 1




  1 0 0 0




                                                              Unknown 3 or MMA

                 AsC                     Unknown 2
                               As(III)                                                     As(V)
                                   DMA

s e c ->    0          2 0 0     4 0 0    6 0 0   8 0 0   1 0 0 0   1 2 0 0   1 4 0 0   1 6 0 0   1 8 0 0   2 0 0 0
As speciation: Barnacle on OLD RSMAS
                  Pier
                 [2 ]   T IC :4 5 5 7 0 .D   [C o u n t]

   5 0 0 0

                                AsB




                                  Unknown 1
   2 5 0 0




                                                                     Unknown 3 or MMA

                   AsC
                  AsC
                                          Unknown
                                         Unknown 2 2                                        As(V)
                                As(III)
                                 As(III)           Unknown 4                                   As(V)
                                      DMA
 s e c ->    0          2 0 0     4 0 0   6 0 0    8 0 0   1 0 0 0   1 2 0 0   1 4 0 0   1 6 0 0   1 8 0 0   2 0 0 0
         Acknowledgements

Dr. Helena Solo-Gabriele
Dr. Pat Walsh
Dr. Greg Mayer
Dr. John Barimo
Ms. Zhangrong Chen
Mr. Myron Georgiadis

				
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posted:9/15/2012
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