Registration Dossier

Environmental fate & pathways

Phototransformation in water

Currently viewing:

Administrative data

Link to relevant study record(s)

Referenceopen allclose all

Endpoint:
phototransformation in water
Type of information:
experimental study
Adequacy of study:
weight of evidence
Study period:
September 2014
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study without detailed documentation
Qualifier:
according to
Guideline:
other: ASTM Method E 896-92
GLP compliance:
not specified
Specific details on test material used for the study:
SOURCE OF TEST MATERIAL
- Source and lot/batch No.of test material: US Army armament research development and engineering center
- Expiration date of the lot/batch: not specified
- Purity: 98%
Radiolabelling:
no
Analytical method:
high-performance liquid chromatography
Details on sampling:
- Sampling intervals for the parent/transformation products: before and after irridiation

- Sampling method: solutions of DNAN were exposed to the simulated sunlight and quantified the concentration changes using an HPLC with UV/Vis detector.
A sample was dissolved in deionized water, adjusted to pH 7 using a phosphate buffer, to achieve a 1 mg/L concentration and placed it in quartz NMR 5 mm tubes. Phototransformation was measured by using a solar simulator, SUNTEST CPS+ Xenon Test Instrument by Atlas Material Testing Technology (Chicago, IL). The Atlas Suntest CPS+ uses an air-cooled xenon lamp to simulate UV and visible solar radiation in the 300–800 nm range. Irradiance (the radiative flux, or the amount of light incident on a unit area of a surface) of 765 W/m2 was used for a period of 200–500 min with samples collected and analyzed over time.

Concentrations of DNAN in solution before and after irradiation by using an Agilent 1200 series HPLC with C18 column at 30°C, a 10 μL manual injection loop, and acetonitrile/water (60/40) mobile phase. A UV/Vis detector measured DNAN at 300 nm (using 360 nm as a reference). No analysis of phototransformation products was done during phototransformation rate studies. Dark samples of DNAN were monitored as the control. Both compounds were found to be stable in the dark over the time of the experiment.

According to ASTM 896 (ASTM International 2005), phototransformation of ionizable materials can exhibit marked pH effects that are attributable to changes in speciation. Therefore, if different species are present in the pH 5–9 range, testing should be conducted at 2–3 pH values throughout the pH 5–9 range.
Light source:
Xenon lamp
Light spectrum: wavelength in nm:
>= 300 - <= 800
Details on light source:
See: Details on analytical Methods
Type of sensitiser:
natural water
Details on sensitiser:
U.S. EPA method OPPTS 835.5270. Humic acid in 60 ppm dissolved OC concentration served as natural organic matter.
Concentration of sensitiser:
ca. 60 other: ppm
Details on test conditions:
To determine the contribution of dissolved natural organic matter present in solution to the transformation of IM compounds under light, we used U.S. EPA method OPPTS 835.5270, “Indirect Photolysis Screening Test” (U.S. EPA 1998). Humic acid (from Sigma Aldrich, St. Louis, MO) in 60 ppm dissolved OC concentration served as natural organic matter.

We took initial phototransformation rate measurements (including those at varying pH for NTO) at 35°C because it is the lowest temperature that the solar simulator can maintain. This temperature is within the recommended standard range of test temperatures for phototransformation according to ASTM E896-92 (ASTM International 2005) but is higher than can be expected in some environments. Consequently, to describe temperature dependence of phototransformation rates, we performed direct phototransformation measurements at pH 7 for four different temperatures between 70°C and 35°C. Control solutions set in the dark indicated that both compounds were stable across the temperature range used.
Dark controls:
yes
Key result
DT50:
ca. 330 min
Test condition:
Direct phototransformation
Key result
DT50:
ca. 5.5 h
Test condition:
Direct phototransformation
Key result
DT50:
ca. 0.23 d
Test condition:
Direct phototransformation
Transformation products:
not measured
Validity criteria fulfilled:
not specified
Conclusions:
Phototransformation half-life of DNAN is 330 min (i.e. 5.5 h or 0.23 d)
Executive summary:

Following ASTM Method E 896-92 guideline, Phototransformation Half-life of DNAN is 330 min, (i.e. 5.5 h or 0.23 d)

Endpoint:
phototransformation in water
Type of information:
experimental study
Adequacy of study:
weight of evidence
Study period:
June 2011
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
comparable to guideline study with acceptable restrictions
Remarks:
no GLP certificate
Study type:
direct photolysis
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 316 (Phototransformation of Chemicals in Water - Direct Photolysis)
Deviations:
not applicable
GLP compliance:
not specified
Radiolabelling:
no
Analytical method:
high-performance liquid chromatography
other: LC-MS for DNAN degradation products, attached to an HPLC system
Details on sampling:
- Sampling intervals for the parent/transformation products: 1 time per day
- Sampling method:
The total power of the Solar Simulator output spectrum was calibrated to the best approximation of ASTM Air Mass 1.5 Global Tilt Standard in the 280-800nm region: total irradiance of 590,000 W m-2. Experiments were conducted at 25ºC in 20 mL quartz covered crucibles (25 mm, internal diameter) with 5 mL of aqueous solutions of NQ (28 mg/ L) or DNAN (51 mg/ L) in deionized water. All tests were done in duplicate. DNAN was analyzed by reverse phase HPLC-UV. Products were analyzed as follows. Ammonium cation was analyzed by HPLC (Thermo-separation-products (TSP) model P4000 & AS3000) using a Hamilton PRP-X200 cation resin column (250 x 4.1 mm I.D., 10 μm) and a conductivity detector (Waters model 432). A mobile phase consisting of 4 mM nitric acid with 30% methanol was used at a flow rate of 0.5 mL/ min and 40°C. Detection limit of the method is 0.050 mg/ L. Formaldehyde was analyzed by HPLC after derivatization with 2,4-pentanedione. Detection limit of the method is 0.025 mg/ L.

Glycolate, acetate, formate, and glyoxylate were quantified by HPLC (Waters) equipped with a pump model 600, an autosampler model 717 plus, and a conductivity detector (model 432).The separation was made on a DIONEX IonPac AS15 column (4 x 250 mm). A mobile phase of 5 mM KOH was first run for 20 min then a gradient up to 40 mM KOH was used for 30 min which was maintained for additional 5 min at a flow rate of 1.5 mL/ min and 40°C. The detection of anions was enhanced by reducing the background with an autosuppressor from ALTECH (model DS-Plus) which allowed detection limits for each anion of 0.15 mg/ L. Other anions (NO2-, NO3-) were monitored using an HPLC from Dionex (system DX-500) equipped with a conductivity detector and Dionex ion chromatography column (IonPac AS15) (250 mm x 4 mm ID). The mobile phase is 30 mM KOH solution. Analysis was carried out at room temperature under a flow rate of 1.5 mL/ min.

DNAN degradation products were analyzed by LC-MS using a mass spectrometer (MS, Bruker MicroTOFQ mass analyzer) attached to an HPLC system (Hewlett Packard 1200 Series) equipped with a DAD detector. Aliquots (10 μL) were injected into a 3.5 micron-pore size Zorbax SB-C18 column (2.1 mm ID × 150 mm; Agilent, Mississauga, Canada) at 25°C. The solvent system was composed of a CH3OH/H2O gradient (40 to 90% v/v) at a flow rate of 0.15 mL/ min. For mass analysis, negative electrospray ionization (ES-) was used to produce deprotonated molecules (M-H)¯ and characteristic mass fragments. Mass range was scanned from 40 to 1000 m/z. Degradation products, mass balances, and stoichiometries were determined to elucidate degradation pathways to better understand the fate of these compounds when exposed to solar irradiation.

- Sampling intervals/times for pH measurements: not specified
- Sampling intervals/times for sterility check: not specified
- Sample storage conditions before analysis: not specified
- Other observation, if any (e.g.: precipitation, color change etc.): not specified
Light source:
sunlight
Light spectrum: wavelength in nm:
>= 280 - <= 800
Relative light intensity:
590 000
Details on light source:
In order to predict the degradability of those chemicals in naturally occurring conditions, the irradiation experiments were conducted using artificial sunlight generated from a SolSim Solar Simulating Photoreactor (Luzchem Research, Inc, Canada). The total power of the Solar Simulator output spectrum was calibrated to the best approximation of ASTM Air Mass 1.5 Global Tilt Standard in the 280-800nm region: total irradiance of 590,000 W m-2.
Details on test conditions:
TEST SYSTEM
- Type, material and volume of test apparatus/vessels: 20 mL quartz covered crucibles
- If no traps were used, type of test system: closed

TEST MEDIUM
- Kind and purity of water: deionized water

REPLICATION
- No. of replicates (dark): 2
- No. of replicates (irradiated): 2
Duration:
25 d
Temp.:
25 °C
Initial conc. measured:
51 mg/L
Reference substance:
not specified
Dark controls:
not specified
Key result
% Degr.:
50
Sampling time:
3.1 d
Test condition:
disappeareance with SolSim
Quantum yield (for direct photolysis):
0.22
Predicted environmental photolytic half-life:
3.1 d
Transformation products:
yes
Remarks:
C7H7NO4, C6H4N2O5, C6H6N2O3, C6H4N2O4, C7H6N2O4, C7H4N2O4, C7H4N2O5, C7H4N2O5.
No.:
#1
No.:
#2
No.:
#3
No.:
#4
No.:
#6
No.:
#5
Validity criteria fulfilled:
yes
Conclusions:
Photodegradation of DNAN and the formation of its degradation products with time. Similar to NTO, plot of ln {C[DNAN] /C0 [DNAN]} vs. time gave straight line with r2 =0.99 confirming that photolysis of DNAN (51 mg/ L) proceeded was a first order reaction. The rate constant kDNAN SS and t1/2 of DNAN disappearance with SolSim were 0.22 d-1 and 3.1 d, respectively.
Executive summary:

The report summarizes findings on the environmental fate and ecological impact of DNAN. Firstly, aqueous solubility (Sw), octanol/water partition coefficients (Kow), sorption and stability were measured in two soils (DRDC-08 and DRDC-09 as provided by DRDC). Secondly the toxicity of the chemical on various ecological receptors including earthworms, alga, and bacteria were determined. Preliminary findings showed that DNAN has a higher sorption coefficient indicating that this chemical will stay close to the soil surface.

However DNAN was found to photodegrade at wavelengths within the range of solar irradiation. Also indigenous bacteria in soil were found capable of degrading DNAN. These preliminary experimental findings indicate that DNAN may not stay in the open environment indefinitely but rather they can photodegrade (soil surface) and biodegrade.

Description of key information

For this endpoint 2 different independent sources of data were provided. Every information provided is relevant for this endpoint, even if the information from each single source alone could be judged insufficient, as these studies did not followed strictly established guidelines, under GLP conditions.

Despite, a strong consistency in the results presented in both studies used for this endpoint was noticed, leading to conclude that combined weight is substantial for allowing an expert judgement.

In fact, every study presented for this endpoint, did not follow strictly established guidelines, but these studies all concluded on the same key value: Half-life of the susbtance in water (i.e. 2,4 -dinitroanisole) is 0.22 d.

Key value for chemical safety assessment

Half-life in water:
0.22 d

Additional information