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Water solubility

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Endpoint:
transformation / dissolution of metals and inorganic metal compounds
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
April 2010
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: non-GLP, guideline analysis
Qualifier:
according to guideline
Guideline:
other: SFS-EN 12457-3. Characterisation of waste. Leaching. Compliance test for leaching of granular waste materials and sludges.
Deviations:
no
GLP compliance:
no
Type of method:
other: Leaching test; two-stage shaking test
Type of test:
other: Two-stage shaking test
Mean dissolved conc.:
77 other: mg/kg (dw)
Element analysed:
Barium
Incubation duration:
8 h
Type of test:
other: Two- stage shaking test/SFS-EN 12506, ISO 11885
Mean dissolved conc.:
23 other: mg/kg (dw)
Element analysed:
Barium
Incubation duration:
6 h
Details on results:
Barium was found to be the most leachable metal. Molybdenium, lead, selenium and zinc leached to a minor extent. Of heavy metals, lead leached in detectable amount. The most leachable ions were chloride and sulphate, of which chloride leached ten times more than sulphate. Some Dissolved Organic Carbon was found in the leachate.

Table 2. Results and uncertainties of the leaching test.

 Element  Unit  Result L/S 2  Result L/S 10 (cumulative)  Expanded Uncertainty (95% confidence)  Method  Remarks
 Arsenic, As  mg/kg (d.w.)  <0.03  <0.15  -  SFS-EN 12506, ISO11885 (ICP-OES)  aa
 Barium, Ba  mg/kg (d.w.)  23  77  ±16%  SFS-EN 12506, ISO11885 (ICP-OES)  aa
 Cadmium, Cd  mg/kg (d.w.)  <0.003  <0.015  -  SFS-EN 12506, ISO11885 (ICP-OES)  aa
 Cobalt, Co  mg/kg (d.w.)  <0.01  <0.05  -  SFS-EN 12506, ISO11885 (ICP-OES)  aa
 Chromium, Cr  mg/kg (d.w.)  <0.02  <0.1  -  SFS-EN 12506, ISO11885 (ICP-OES)  aa
 Copper, Cu  mg/kg (d.w.)  <0.02  <0.1  -  SFS-EN 12506, ISO11885 (ICP-OES)  aa
 Molybdenum, Mo  mg/kg (d.w.)  0.042  0.12  ±25%  SFS-EN 12506, ISO11885 (ICP-OES)  
 Nickel, Ni  mg/kg (d.w.)  <0.02  <0.1  -  SFS-EN 12506, ISO11885 (ICP-OES)  aa
 Lead, Pb  mg/kg (d.w.)  0.16  0.64  ±25%  SFS-EN 12506, ISO11885 (ICP-OES)  aa
 Antimony, Sb  mg/kg (d.w.)  <0.01  <0.05  -  ISO11885 (ICP-OES), GFAAS  aa,**
 Selenium, Se  mg/kg (d.w.)  0.017  0.053  ±25%  ISO11885 (ICP-OES), GFAAS  aa,**
 Tin, Sn  mg/kg (d.w.)  <0.03  <0.15  -  ISO11885 (ICP-OES)  
 Vanadium, V  mg/kg (d.w.)  <0.01  <0.05  -  SFS-EN 12506, ISO11885 (ICP-OES)  aa
 Zinc, Zn  mg/kg (d.w.)  0.021  0.23  ±25%  SFS-EN 12506, ISO11885 (ICP-OES)  aa
 Mercury, Hg  mg/kg (d.w.)  <0.001  <0.005  -  SFS-EN 13370, SFS-EN 1483:en (CVAAS)  
 Fluoride, F-  mg/kg (d.w.)  <1  <5  -  SFS-EN 13370, SFS-EN 10304-1 and 2 (IC)  
 Chloride, Cl-  mg/kg (d.w.)  490  500  ±25%  SFS-EN 13370, SFS-EN 10304-1 and 2 (IC)  
 Sulphate, SO42-  mg/kg (d.w.)  <10  <50  -  SFS-EN 13370, SFS-EN 10304-1 and 2 (IC)  
 DOC  mg/kg (d.w.)  6.8  14  ±20%  SFS-EN 13370, SFS-EN 1484  sb
 Phenol index  mg/kg (d.w.)  <0.1  <0.5  -  SFS-EN 13370, SFS-EN ISO 14402:en  sb

Concentrations are expressed on a dry weight (d.w.) basis. L / S = liquid to solid ratio. **) = If ICP-OES result is below the method quantitation limit, determination is made using GFAAS. ICP-OES = Inductively coupled plasma optical emission spectrometry. GFAAS = Graphite furnace atomic absorption spectrometry. CVAAS = Cold vapour atomic absorption spectrometry. IC = Ion Chromatography. sb = subcontracted

Conclusions:
The most leachable metal from Ash was barium. Molybdenium, lead, selenium and zinc leached to a minor extent. The most leachable ions were chloride and sulphate, of which chloride leached ten times more than sulphate. Some Dissolved Organic Carbon was found in the leachate.
Executive summary:

Leaching properties of Ash was studied in a non-GLP compliant study according to European standard SFS-EN 12457-3. Ash was homogenised to particle size <4 mm followed by two phase extraction with ultraclean water (18 MΩ/cm, pH 5 - 7.5) in L/S = 2 and L/S = 10. The filtrate was analysed with atomic absorption, ICP-OES and liquid chromatigraphic methods. The most leachable metal from Ash was barium. Molybdenium, lead, selenium and zinc leached to a minor extent. The most leachable ions were chloride and sulphate, of which chloride leached ten times more than sulphate. Some Dissolved Organic Carbon was found in the leachate.

Endpoint:
transformation / dissolution of metals and inorganic metal compounds
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
September 2010
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: non-GLP, non-guideline analysis
Qualifier:
no guideline available
Principles of method if other than guideline:
Acid (pH 4.65) ammonium acetate extraction including analysis with ICP-OES.
GLP compliance:
no
Type of method:
other: Acid ammonium acetate extraction
Type of test:
other: Acetate extraction
Mean dissolved conc.:
2 190 other: mg/kg (d.w.)
Element analysed:
Potassium
Incubation duration:
1 h
Type of test:
other: Acetate extraction
Mean dissolved conc.:
4 470 other: mg/kg (b.w.)
Element analysed:
Silicon
Incubation duration:
1 h
Type of test:
other: Acetate extraction
Mean dissolved conc.:
6 100 other: mg/kg (d.w.)
Element analysed:
Sulphur
Incubation duration:
1 h
Type of test:
other: Acetate extraction
Mean dissolved conc.:
6 170 other: mg/kg (d.w.)
Element analysed:
Magnesium
Incubation duration:
1 h
Type of test:
other: Acetate extraction
Mean dissolved conc.:
158 000 other: mg/kg (d.w.)
Element analysed:
Calcium
Incubation duration:
1 h
Details on results:
The most soluble metal in acidic ammonium acetate was calcium. Other macronutrients, which extracted at higher amounts, were magnesium, sulphur, silicon and potassium. The most extracted trace metals were zinc and copper. Of the most toxic components, lead extracted most followed by nickel, arsenic and cadmium.

Table 1 Acid ammonium acetate soluble elements

Element Unit Result
Aluminum mg/kg (d.w.) 120
Calcium mg/kg (d.w.) 158000
Iron mg/kg (d.w.) 5.0
Magnesium mg/kg (d.w.) 6170
Phosphorus mg/kg (d.w.) 74
Potassium mg/kg (d.w.) 2190
Silicon mg/kg (d.w.) 4470
Sodium mg/kg (d.w.) 490
Titanium mg/kg (d.w.) 1.5
Sulphur mg/kg (d.w.) 6100
Manganese mg/kg (d.w.) 170
Arsenic mg/kg (d.w.) 3.5
Barium mg/kg (d.w.) 69
Cadmium mg/kg (d.w.) 1.5
Cobalt mg/kg (d.w.) 0.87
Chromium mg/kg (d.w.) 3.3
Copper mg/kg (d.w.) 50
Molybdenium mg/kg (d.w.) 3.0
Nickel mg/kg (d.w.) 4.2
Lead mg/kg (d.w.) 8.3
Antimony mg/kg (d.w.) 2.4
Selenium mg/kg (d.w.) 1.5
Vanadium mg/kg (d.w.) 0.89
Zinc mg/kg (d.w.) 190
Mercury mg/kg (d.w.) <0.1
Conclusions:
The most soluble metal in acidic ammonium acetate was calcium. Other macronutrients, which extracted at higher amounts, were magnesium, sulphur, silicon and potassium. The most extracted trace metals were zinc and copper. Of the most toxic components, lead extracted most followed by nickel, arsenic and cadmium.
Executive summary:

Ammonium acetate soluble metals from Ash were analysed in non-GLP compliant laboratory with a non-guideline method. The aim of this study was to simulate long term leaching properties of metals from Ash. Extraction ratio was 1:10 (V/V) and extraction time was 1 h. pH of the test was 4.65. Before determination, the extract was separated from the solid residue by filtration. The element concentrations of the extracts were determined with inductively coupled plasma optical emission spectrometer (ICP-OES). Of nutriets, calcium was clearly the most extractable element. Also magnesium, sulphur, silicon and potassium obtain remarkable long-term leaching properties, but approx. 25 times less than calcium. Zinc, copper and barium extracted as amounts of over 10 mg/kg (d.w.). Of the most toxic components, lead extracted most followed by nickel, arsenic and cadmium. Mercury was not found to be acidic ammonium acetate soluble element.

Endpoint:
water solubility
Type of information:
experimental study
Adequacy of study:
supporting study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: A non-GLP, guideline analysis with modifications.
Reason / purpose for cross-reference:
reference to same study
Qualifier:
according to guideline
Guideline:
other: EN 12457-3
Deviations:
yes
Principles of method if other than guideline:
Bottom ash (aged for five years) was studied with sequential batch leaching from L/S 1 to L/S 3 using the modified EN 12457-3 (two stage batch test) method. The modified method included three subsequently steps of leaching at cumulative liquid to solid (L/S) ratios of 1, 2 and 3 L/kg.
GLP compliance:
no
Remarks on result:
other: Results presented in "details of results" section
Details on results:
The validation parameters are shown in Table 7. In the leaching test pH was between 8.0-8.1 in all the leachates. The stabile pH indicates that the material has been well aged during the storing and that hydroxides have been converted to carbonates due to the exposure to air (CO2). Conductivity was found to decrease from 803 to 373 mS/m and redox potential varied between 280 and 315 mV.

Study results are presented in table 8. The ash contained a considerable amount of salts with high solubility, shown by the initial high concentrations of e.g. Na, K and Cl. The highest metal concentrations in leachate L/S 1 were found for Na, Ca, K, Mg and Si. The concentration of Na, K and Cl was reduced by 75 %, 65 % and 90% from L/S 1 to L/S 3, respectively. The concentration of Ca, Al and Zn was stabile during all studied L/S-ratios, while the concentration of Cu was reduced by 50% from L/S 1 to L/S 3. The concentration of DOC decreased simultaneously with decreasing copper concentration (approx. 35% from L/S 1 to L/S 3). Concentrations of Cd and Mn were found to slightly increase from L/S1 to L/S 3. All the studied elements showed high precision; the standard deviation was in general lower or equal to the analytical error of the individual elements.

Table 7. Parameters of validation measured at termination of leaching

 Validitetsparametrar  L/S  1  2  3
 pH    8.0 (±1%)  8.1 (±1%)  8.1 (±0%)
 Ledningsförmåga  mS/m 25 °C  803 (±1%)  506 (±2%)  373 (±5%)
 Redox Eh  mV  284 (±3%)  280 (±11%)  315 (±2%)

Table 8. Concentrations of compounds in leachates (sampled at L/S 1, 2 and 3) together with concentrations in solution used for dilution in the ecotox-tests. Samples were filtrated through 0.45 μm pore-filter prior analyses. For comparison, concentrations in natural water sampled at the location Landsortsdjupet in the Baltic See are also shown. This sample is assumed to be comparable with the origin of the water used for dilution (Askö).

  Halt i lakvatten vid L/S 1, 2 och 3                  Halt i spädningsmedia          
      L/S 1 n=2  Stdv %  L/S2 n=2  Stdv %  L/S3  Spädningsmedia* ofiltrerad  Spädnings-media*  Stdv %  Landsort s-djupet**
 Metaller                              
 Ca mg/l   526  2  520  2  525  89  96,8  4  92
 Fe mg/l   <0,007    <0,004    0,005  <0,004  0,0187  112  0,0016
 K mg/l   210  12  114,5  2  77,4  70,2  74,7  13  70,8
 Mg mg/l   62,8  2  44,45  1  38,2  224  237  6  223
 Na mg/l   1435  2  695  0  377  1940  1980  4  1847
 Si mg/l   2,855  3  2,845  3  2,63        
 Al μg/l   200,5  1  196,5  5  209  5,68  10,4  50  
 As μg/l   3,245  15  <2,7    <1  2,31  2,31  74  
 Ba μg/l   42,4  1  32,5  4  29,5  38,4  37,4  2  
 Cd μg/l   <0,095    <0,071    0,077  <0,05  <0,05    0,021
 Co μg/l   0,9945  12  0,826  26  0,592  <0,05  0,09  63  
 Cr μg/l   6,215  1  3,32  0  2,11  <0,5  0,842  24  
 Cu μg/l   79,4  16  50,3  3  39,3  2,67  3,55  13  0,55
 Hg μg/l   <0,02    <0,02    <0,02  <0,02      
 Mn μg/l   15,85  2  25  3  27,4  2,5  1,59  82  1,7
 Mo μg/l   221,5  6  174  6  134        
 Ni μg/l   5,41  4  5,09  25  3,41  5,86  7,14  25  0,69
 Pb μg/l   0,4115  10  <0,02    0,22  <0,20  0,24  24  
 Sb μg/l   37,5  10  24,45  0  18,2        
 Se μg/l   3,46  11  1,645  9  0,897        
 V μg/l   1,05  0  1,055  6  0,888        
 Zn μg/l   27,65  5  26,9  23  26,1  12,8  14,1  16  0,38
 Övriga                             
 Cl mg/l  936  4  337  17  106  4730  3915  19  
 F mg/l  <0,2    0,41    <0,2  <0,4      
 S-tot mg/l  1220  1  822  12  741  185  188  6  161
 SO4 mg/l  3470  5  2500  7  2180  661  550  17  
 DOC mg/l  13,3  3  5,855  15  4,43  3,48  4,48  33  3 -5
 DIC mg/l   22,7  1  21,75  7  18,6        2***

*Data för spädmedium hämtad ur rapport av Värmeforsk (2011). Spädmedium är filtrerat och upphettat brackvatten hämtat utanför Stockholms universitets fältstation på Askö.

**Data gällande för Landsortsdjupet från Forsberg (2005) med undantag för DOC där data är hämtade från Österlund (2010) och är representativa för Bottniska viken och Gotlandsdjupet.

*** Förväntad halt i Havsvatten.

Conclusions:
The highest metal concentrations in the first leachate were found for Na, Ca, K, Mg and Si. The concentration of Na, K and Cl was reduced by 75 %, 65 % and 90 % from L/S 1 to L/S 3, respectively. The concentration of Ca, Al and Zn was stabile during all studied L/S-ratios, while the concentration of Cu was reduced by 50% from L/S 1 to L/S 3. The concentration of DOC decreased simultaneously with decreasing copper concentration (approx. 35% from L/S 1 to L/S 3). Concentrations of Cd and Mn were found to slightly increase from L/S1 to L/S 3.
Executive summary:

A modified two stage batch leaching test (EN 12457-3) was used to analyse leaching of metals and salts from 5 -years aged bottom ash in a non-GLP study. Metal analyses were performed for both ash and leachates. The leachates were analyzed for the following elements Ca, Fe, K, Mg, Na, Si, Al, As, Ba, Cd, Co, Cr, Cu, Mn, Mo, Ni, Pb, Sb, Se, V, Zn (mod. EPA-200.7 and EPA-200.8) and Hg (EN ISO 17852:2008), anions chloride, fluoride, sulphate (mod. EN ISO 10304-1 and EN ISO 10304-2) together with dissolved organic carbon (DOC) and total inorganic carbon (TIC) (EN 1484). The most readily leached metals were Na, Ca, K, Mg and Si. The concentration of Na, K and Cl was reduced by 75 %, 65 % and 90% from L/S 1 to L/S 3, respectively. Of the trace metals, concentrations of Mo and Al were highest in the first eluate (L/S 1). Release of Cd and Mn was slower as their concentration increased during the test. Continuous, more steady leaching was found for Ca, Al and Zn. The concentration of DOC decreased simultaneously with decreasing copper concentration (approx. 35% from L/S 1 to L/S 3). pH was approx. 8 during the different test sequences.

Endpoint:
water solubility
Type of information:
experimental study
Adequacy of study:
supporting study
Reliability:
3 (not reliable)
Rationale for reliability incl. deficiencies:
other: A non-GLP, non-guideline analysis.
Principles of method if other than guideline:
Analysis of leaching properties of metals from wood, peat, mixed biofuel and Recycled Fuel (REF) ashes originating from four different types of power plants. The used liquid-solid fractions were L/S 2 and 10.
GLP compliance:
no
Remarks on result:
other: Detailed results are presented in "Details of results" section
Details on results:
Limit values of As, Cd, Cr, Cu, Mo, Pb, Sb, Zn or Sulphate for unpaved and paved constructions were not exeeded.

Table 1 presents leaching properties of different ashes produced with different kind of fuels (mg/kg). Limit values for utilisation presented in the table 2 are not exceeded in the studied ashes (Table 1).

Table 1. Leaching properties of selected metals (i.e. critical components, see Environmental fate properties) from different ashes produced with different kind of fuels (mg/kg).

Sample

REF; Grate firing

REF; Grate firing (washed)

REF; BFC bottom ash

REF; BFC fly ash

Mixed biofuel; BFC bottom ash

Mixed biofuel; BFC fly ash

Mixed biofuel, incl. REF; BFC bottom ash

Mixed biofuel, incl. REF; BFC fly ash

Limit value of utilisation I

Limit value of utilisation II

 

L/S2 / L/S10

L/S2 / L/S10

L/S2 / L/S10

L/S2 / L/S10

L/S2 / L/S10

L/S2 / L/S10

L/S2 / L/S10

L/S2 / L/S10

L/S10

L/S10

 pH

9.5 / 10.2

9.7 / 10.5

11.2 / 11.8

11.0 / 11.5

11.1 / 11.1

12.1 / 11.7

11.6 / 11.4

12.7 / 12.5

 

 

 Conductivity

560 / 55

79 / 19

176 / 195

2570 / 290

48 / 39

499 / 138

104 / 70

1497 / 719

 

 

 As

 

 

 

<0.02 / <0.2

 

 

 

 

0.14

0.85

 Cd

 

 

 

<0.02 / <0.02

<0.02 / <0.02

<0.02 / <0.02

 

 

0.011

0.015

 Cu

0.02 / 0.1

<0.02 / <0.1

<0.02 / <0.1

<0.02 / <0.1

<0.02 / <0.1

 <0.02 / <0.1

 

 

1.1

2.0

 Pb

 

 

 

 

<0.02 / <0.1

<0.02 / <0.1

 

 

1.0

1.8

 Sb

 

 

 

<0.06 / 0.2

 

 

0.05 / 0.14

<0.01 / <0.05

0.12

0.4

 Sulphate

 

 

 

130 / 340

 

 

 

 

1500

 

BFC = Bubbling Bed Combustion

REF = Recovered Fuel

Limit value I for unpaved constructions, limit value II for paved constructions (Mroueh et al. 2000).

Table 2. Minor (mg/kg) and major (%) components in ashes related to Table 1.

Minor (mg/kg)

Wood ash

Peat ash

 

REF; Grate firing

 

REF; BFC bottom ash

 

REF; BFC fly ash

 

Mixed biofuel; BFC bottom ash

 

Mixed biofuel; BFC fly ash

 

Mixed biofuel, incl. REF; BFC bottom ash

 

Mixed biofuel, incl. REF; BFC fly ash

Sb

N/A

N/A

12

27

94

N/A

N/A

N/A

N/A

As

0.2-60

31-116

40

21

51

<30

<30

<30

<50

Cd

0.4-40

0.5-5

3.9

0.05

15

<10

<10

<10

<10

Cr

40-250

43-130

150

120

230

22

63

48

100

Cu

15-300

60-160

850

1200

2200

29

120

120

180

Pb

15-1000

160-970

93

55

790

<40

55

<40

91

Major (%)

Wood ash

Peat ash

 

REF; Grate firing

 

REF; BFC bottom ash

 

REF; BFC fly ash

 

Mixed biofuel; BFC bottom ash

 

Mixed biofuel; BFC fly ash

 

Mixed biofuel, incl. REF; BFC bottom ash

 

Mixed biofuel, incl. REF; BFC fly ash

Al

3.03

11.2

12

4.25

8.7

6.47

8.52

4.88

8.91

K

4.7

0.7

12.4

2.5

2.48

3.49

2.14

N/A

N/A

Ca

12

6.78

8.17

6.78

18.7

3.19

10

6.21

13.8

Mg

1.24

0.6

N/A

N/A

N/A

N/A

N/A

N/A

N/A

Na

0.69

0.3

2.31

1.04

1.39

1.87

1.13

N/A

N/A

Si

13.7

18.6

N/A

N/A

N/A

N/A

N/A

N/A

N/A

Fe

3.16

7.44

6.61

1.9

6.02

0.91

2.84

0.84

2.66

Sulphate

4.01

0.79

2.1

0.2

8.31

N/A

N/A

N/A

N/A

References

Mroueh, U.-M. et al. 2000. Sivutuotteet maarakenteissa. Tekes-teknologiakatsaus 93/2000. 87 s. (In Finnish)

Conclusions:
Limit values of As, Cd, Cu, Pb, Sb, or Sulphate for unpaved and paved constructions were not exeeded in the leachates of different ashes.
Executive summary:

Leaching tests with L/S 2 and L/S 10 were performed for wood, peat, mixed biofuel and Recycled Fuel (REF) ashes originating from four different types of power plants in a non-GLP study. Results were compared to limit values of unpaved and paved constructions (Mroueh et al. 2000). Limit values of As, Cd, Cu, Pb, Sb, or Sulphate were not exeeded in the leachates of different ashes. Although concentrations of these metals were clearly higher in REF ashes than in mixed biofuel ashes, there was no remarkable difference in leaching test results.

Endpoint:
water solubility
Type of information:
experimental study
Adequacy of study:
key study
Study period:
Study was conducted between 2 June 2010 and 4 June 2010
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP compliant guideline study.
Qualifier:
according to guideline
Guideline:
EU Method A.6 (Water Solubility)
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Remarks:
25 February 2009
Type of method:
column elution method
Water solubility:
< 1 mg/L
Temp.:
30 °C
pH:
ca. 12
Remarks on result:
other: pH range was 12.48-12.54. Water solubility value is estimated.
Details on results:
Unable to detect on the UV spectrometer - no peak absorbance obtained. Therefore HPLC and UV spectrometry unsuitable methods of determination.
Owing to the fact that the column elution method did not produce any useable results the flask method was attempted. 5.1757g was added to flask 1, 5.5255g to flask 2 & 5.0365g to flask 3. The flasks were then shaken for 1 day, 2 days and 3 days at 30°C. After leaving the flasks to settle overnight, a sample of the supernatant was removed, filtered and scanned using the UV spectrophotometer. No peak absorbance was observed, the only option to determine the water solubility was to provide an estimated value. 1mg of sample was weighed into a 1000ml volumetric flask which was shaken vigorously. Small particles were apparent after several periods of shaking, hence an estimated value of <1 mg/l.

Table 1. Preliminary (Estimated) Analysis

Mass of sample (mg)  Volume of water in which  sample dissolve (ml)  Estimated solubility (g/L)  Analysis method
 1000  0  Column Elution Method

Comment: Unable to detect on the UV spectrometer - no peak absorbance obtained. Therefore HPLC and UV spectrometry unsuitable methods of determination.

Table 2. Formal Analytical Determination

UV- Analytical Determinations

Flask No. pH  Absorbance 1  Absorbance 2  Mean concentration (g/L) 
12.50  N/A 
12.48  N/A 
12.54  N/A 

Conclusions:
Interpretation of results: slightly soluble (0.1-100 mg/L) <1mg/l
The Ash was found to be slightly water soluble (< 1 mg/l).
Executive summary:

The water solubility of Ash was studied in a GLP compliant laboratory according to Method A.6. in Comission Regulation No 440/2008. The preliminary shaking test with a flask method showed very low water solubility. Thus, column elution method was used for more detailed study. The column elution showed no UV peak absorbance, which together with the shaking test led to the conclusion of water solubility lower than 1 mg/l.

Description of key information

The water solubility of Ash was studied in a GLP compliant laboratory according to Method A.6. in Commission Regulation No 440/2008. The water solubility was found to be < 1 mg/l. Despite the major proportion of Ash is non-soluble minerals, salts and some metals leach from it. Leaching properties were studied with four different leaching tests. 

Key value for chemical safety assessment

Water solubility:
1 mg/L
at the temperature of:
20 °C

Additional information

Ash typically consists of minerals mainly as oxides and trace metals (Isännäinen &Huotari (1994)). This leads to a difficulty to measure water solubility as required according to REACH information requirements in Annex VII (7.7.). Low solubility observed in the guideline compliant study reflects the physical property of Ash. Council directive 1999/31/EC on the landfill waste regulates of establishing criteria and procedures for the acceptance of waste at landfills. One tool to assess environmental impacts of inert materials is to study leaching properties of them. The leaching test i.e. water extraction performed for this dossier is accordant to national legislation and compliant with an European standard. Extraction of metals in water shows short term leachability properties.

Of the analysed ions in water leachate, Chlorine was most abundant. Additionally, some dissolved organic compounds were detected, but no phenol compounds were present.

Since environmental pH is typically below neutral, acid (pH 4.5) ammonium acetate extraction was performed to describe solubility in the longer term. Table 1 presents the concentrations of certain leached heavy metals in leaching test and in acetate extraction of Ash.

Table 1. Concentrations of leached heavy metals from Ash (mg/kg (d.w.)). Leaching test describes quickly water soluble fraction and acetate extraction reflects long term leachability from Ash.
       Unit  Leaching test     Acetate extraction
 Result L/S 2  Result L/S 10 (cumulative)  Result
 Arsenic, As  mg/kg (d.w.)  <0.03  <0.15  3.5
 Barium, Ba  mg/kg (d.w.)  23  77  69
 Cadmium, Cd  mg/kg (d.w.)  <0.003  <0.015  1.5
Copper, Cu  mg/kg (d.w.)  <0.02  <0.1  50
 Lead, Pb  mg/kg (d.w.)  0.16  0.64  8.3
 Antimony, Sb  mg/kg (d.w.)  <0.01  <0.05  2.4

In ammonium acetate extraction, major components were found to leach followingly: Ca>Mg>Si>K>Na>Al>P>Fe. Of these, Ca leached 25 fold more than Mg, Si and K, to which the difference of the amounts of Na and Al was approx. 10 fold. P was leached 5 -10 fold less than the previous group and Fe 15 times less than P. Aim of Ash use in fertilisation is to release main nutrients. Aluminium, however, can have adverse effects due to its toxic properties. Mobility and toxic effects of aluminium in environment are pH dependent. Binding at humic substances typically decrease toxicity.

Table 2 presents leaching properties of different ashes produced with different kind of fuels (mg/kg) (Ranta & Wahlström (2002)). Limit values for utilisation presented in the table 2 are exceeded neither in Ash (Table 1) nor in the studied ashes (Table 2).

Table 2. Leaching properties of different ashes produced with different kind of fuels (mg/kg) according to Ranta & Wahlström (2002).

Sample

REF; Grate firing

REF; Grate firing (washed)

REF; FBC bottom ash

REF; FBC fly ash

Mixed biofuel; BFC bottom ash

Mixed biofuel; BFC fly ash

Mixed biofuel, incl. REF; BFC bottom ash

Mixed biofuel, incl. REF; BFC fly ash

Limit value of utilisation I

Limit value of utilisation II

 

L/S2 / L/S10

L/S2 / L/S10

L/S2 / L/S10

L/S2 / L/S10

L/S2 / L/S10

L/S2 / L/S10

L/S2 / L/S10

L/S2 / L/S10

L/S10

L/S10

 pH

9.5 / 10.2

9.7 / 10.5

11.2 / 11.8

11.0 / 11.5

11.1 / 11.1

12.1 / 11.7

11.6 / 11.4

12.7 / 12.5

 

 

 Conductivity

560 / 55

79 / 19

176 / 195

2570 / 290

48 / 39

499 / 138

104 / 70

1497 / 719

 

 

 As

 

 

 

<0.02 / <0.2

 

 

 

 

0.14

0.85

 Cd

 

 

 

<0.02 / <0.02

<0.02 / <0.02

<0.02 / <0.02

 

 

0.011

0.015

 Cu

0.02 / 0.1

<0.02 / <0.1

<0.02 / <0.1

<0.02 / <0.1

<0.02 / <0.1

 <0.02 / <0.1

 

 

1.1

2.0

 Pb

 

 

 

 

<0.02 / <0.1

<0.02 / <0.1

 

 

1.0

1.8

 Sb

 

 

 

<0.06 / 0.2

 

 

0.05 / 0.14

<0.01 / <0.05

0.12

0.4

 Sulphate

 

 

 

130 / 340

 

 

 

 

1500

 

FBC = Fludised Bed Combustion; BFB = Bubbling Bed Combustion

REF = Recovered Fuel

Limit value I for unpaved constructions, limit value II for paved constructions (Mroueh et al. 2000).

Table 3. Minor (mg/kg) and major (%) components in ashes related to Table 2 (Ranta & Wahlström (2002)).

Minor (mg/kg)

Wood ash

Peat ash

 

REF; Grate firing

 

REF; FBC bottom ash

 

REF; FBC fly ash

 

Mixed biofuel; BFC bottom ash

 

Mixed biofuel; BFC fly ash

 

Mixed biofuel, incl. REF; BFC bottom ash

 

Mixed biofuel, incl. REF; BFC fly ash

Sb

N/A

N/A

12

27

94

N/A

N/A

N/A

N/A

As

0.2-60

31-116

40

21

51

<30

<30

<30

<50

Cd

0.4-40

0.5-5

3.9

0.05

15

<10

<10

<10

<10

Cr

40-250

43-130

150

120

230

22

63

48

100

Cu

15-300

60-160

850

1200

2200

29

120

120

180

Pb

15-1000

160-970

93

55

790

<40

55

<40

91

Major (%)

Wood ash

Peat ash

 

REF; Grate firing

 

REF; FBC bottom ash

 

REF; FBC fly ash

 

Mixed biofuel; BFC bottom ash

 

Mixed biofuel; BFC fly ash

 

Mixed biofuel, incl. REF; BFC bottom ash

 

Mixed biofuel, incl. REF; BFC fly ash

Al

3.03

11.2

12

4.25

8.7

6.47

8.52

4.88

8.91

K

4.7

0.7

12.4

2.5

2.48

3.49

2.14

N/A

N/A

Ca

12

6.78

8.17

6.78

18.7

3.19

10

6.21

13.8

Mg

1.24

0.6

N/A

N/A

N/A

N/A

N/A

N/A

N/A

Na

0.69

0.3

2.31

1.04

1.39

1.87

1.13

N/A

N/A

Si

13.7

18.6

N/A

N/A

N/A

N/A

N/A

N/A

N/A

Fe

3.16

7.44

6.61

1.9

6.02

0.91

2.84

0.84

2.66

Sulphate

4.01

0.79

2.1

0.2

8.31

N/A

N/A

N/A

N/A

In a sequential leaching test (Breitholz M. et al. (2012)) with L/S 1, 2, and 3, Na, Ca, K, Mg and Si were the most leached major components. The concentration of Na, K and Cl was reduced by 75 %, 65 % and 90% from L/S 1 to L/S 3, respectively. Of the minor components, concentrations of As, Ba, Cr, Cu, Pb ad Sb decreased between 30% and 70%. The concentration of DOC decreased simultaneously with decreasing copper concentration (approx. 35% from L/S 1 to L/S 3). Concentrations of Cd and Mn were found to slightly increase from L/S1 to L/S 3 and concentrations of Ca, Al and Zn were stabile during all studied L/S-ratios.

REFERENCES

Isännäinen S, Huotari H (1994) Tuhkan ja metsäteollisuuden muiden jätejakeiden prosessointi lannoitekäyttöön soveltuvaksi. Esiselvitys. VTT Energia, Jyväskylä, 1994. In Finnish.

Mroueh, U.-M. et al. 2000. Sivutuotteet maarakenteissa. Tekes-teknologiakatsaus 93/2000. 87 s. In Finnish.