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Environmental fate & pathways

Additional information on environmental fate and behaviour

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Endpoint:
additional information on environmental fate and behaviour
Type of information:
experimental study
Adequacy of study:
supporting study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: The soil simulation tests are not performed according to any guideline studies. However, the methodology is well described, and the results are produced by an authorised National Environmental Research Institute.

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2009
Report Date:
2009

Materials and methods

Test guideline
Qualifier:
no guideline followed
Guideline:
other: Research project; no guideline followed. The materials and methods are documented in the research report, and decribed in the following section.
Deviations:
not specified
Remarks:
five parallel sand columns were used in the study.
Principles of method if other than guideline:
Biodegradation and migration of the substance was studied for 15 weeks (110 d) in columns filled with a soil matrix. The columns were used to study the possible effects of the substance to groundwater quality. The substance concentrations, TOC, alkalinity, pH, nitrate, nitrite, ammonium, total nitrogen, conductivity, oxygen, temperature, and concentration of trace metals were followed from the soil effluents during the experiment. The analysing methods used in this study were as follows:

-concentration of the substance, HPLC
-TOC; Carbon analyzer
-Nitrate, nitrite, ammonium, N-tot, Colorimeter
-Alkalinity, Titration
-Oxygen, conductivity, Probe
-Trace metals, ICP-AES, ICP-MS
-Temperature, thermometer

The substance was introduced into the columns by pumping it through the column with a continous flow rate of 1 ml/min. The study was performed by preparing a tap water solution of the substance (1000 mg/l) corresponding to a concentration of 120 mg/l N-tot and 513 mg/l TOC. The substance purity was 99%.

Five parallel sand columns 3.5 m in height and 0.3 m in diameter were used in the experiment. Two of the columns (2 and 3) contained sand and columns 1,4 and 5 had also a podsol layer on top of the sand. The sand was obtained from Suomies (Hyvinkää, Finland), and it was homogenous with a grainsize of 0.02-0.6 mm. The podsol layer (10 cm in thickness) was obtained from a pine forest (Suomies). The podsol layer was not mixed with the sand. It was used as an undistributed piece on the top of the sand in the columns. Column 1 was used as a control. Only tap water was fed into this column without any substance amendments. The columns were kept within a temperature range of 6 to 7 C during the experiment.

The composition and fate of the degradation products, as well as the leaching potential of trace metals in the soil effluents were recorded during the biodegradation studies.
GLP compliance:
no
Type of study / information:
The study provides additional information on the biodegradation and migration of the substance in soil columns. Information on the degradation products and the fate of these products was also obtained. Additionally, it also provides information on the possible effects of the leachates on groundwater quality.

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
Purity of the substance was 99 %.

Results and discussion

Any other information on results incl. tables

The substance appeared to degrade very efficiently in the soil columns. The initial concentration of the substance fed into the soil columns was 1000 mg/l. During the biodegradation experiment, the concentrations of the substance in the effluents were very low (up to 9 mg/l) or undetectable by HPLC. TOC-concentrations of the effluents supported the results drawn from the analyses of the substance concentrations in effluents. No difference was observed in the TOC concentrations in the water-fed column (used as a control column) in comparison with the substance-fed columns.

The increased level of inorganic constituents (ammonium, nitrate, nitrite, biocarbonate = measured as alkalinity) in the soil effluents indicated also the biodegradation of the substance during the experiment. Oxygen concentration was reduced in all test columns during the experiment (approximately from 12 mg/l down to 2-4 mg/l).

Fate of degradation products of the substance in soil

Complete aerobic mineralization of the substance results in the formation of carbon dioxide, ammonium and water. Carbon dioxide is partly dissolved in the percolating water and forms bicarbonate which can be indicated by alkalinity measurements. Ammonium is biologically oxidised through nitrite to nitrate. Under anaerobic conditions, nitrate may also be biologically reduced into gaseous N2. Other pathways include reduction through nitrite or conversion of ammonia and nitrite directly to nitrogen gas by Anammox bacteria. Other key factors affecting the fate of ammonium in soil are sorption and ion exchange.

According to this study, the ammonium and nitrite concentrations in soil effluent indicated that ammonium was oxidised to nitrate. This resulted in very low concentrations of ammonium and in elevated concentrations of nitrate in the soil leachates. Nitrate concentrations increased towards the end of the experiment approaching the feed concentration of 120 mg N/l. While the nitrate levels in the effluents increased, the alkalinity and pH decreased (from initial pH 7 down to pH 6 in the end of the study). Ammonium and nitrate contributed to almost 100% of total N in the effluents from the beginning until the end of the 110 d experiment. The total nitrogen concentrations at the end of the study were 40 -80 mg/l, the nitrate concentrations 20 -80 mg/l, and nitrite concentrations 1,1 -1,8 mg/l, respectively.

Trace metals in the leachates

The leaching of 30 ions from the columns were quantified. Generally, higher metal concentrations were measured in the leachates from the substance-fed columns compared to the control column (without substance amendment). The sum of the main cations (Na+,K+,Ca2+,Mg2+, NH4+) and main anions (HCO3-, SO42-,SiO2-3, NO-3, NO2-) as meq/l were reported on days 12, 26, 68, and 110. In the control column, the sum of cations decreased from 2.44 to 2.18 meq/l during 110 days experiment. In the substance-fed columns they increased from concentrations of 2.36 -2.94 meq/l to 6.26 -7.62 meq/l, respectively. The sum of anions in the control column decreased from 2.62 to 2.47 meq/l. In the substance-fed columns they increased from 2.26 -3.12 meq/l to 6.45 -7.94 meq/l, respectively.

The substance which was amended into the soil columns increased the leaching of metals from the soil (sand). The most critical metal in terms of leaching was nickel. The concentration of nickel increased up to 8 ug/l in the substance-fed columns while in the control column (without substance amendment) nickel concentration in the effluent remained at 2 ug/l.

Applicant's summary and conclusion

Conclusions:
The substance rapidly biodegraded in the sand soil columns. The biodegradation was studied for 110 days by pumping tap water amended with the substance through a soil texture, at an initial concentration of 1000 mg/l and a continous flow rate of 1 ml/min. Five parallel columns were used in the experiment. One of the columns was used as a control column without any substance amendment. The substance concentrations, TOC, alkalinity, pH, nitrate, nitrite, ammonium, total nitrogen, conductivity, oxygen, temperature, and concentration of trace metals were analysed from the effluents during the experiment.

According to this study, the substance or its organic degradation compounds are not likely to enter the groundwater. Ammonium was released during the biodegradation, and further oxidised via nitrate and nitrite. Additionally, formation of ammonium, nitrate and nitrite during the biodegradation might cause undesirable environmental effects to waterbodies when the substance is used as a de-icer in large scale. According to this study, it is recommended to assess these effects on a case-by-case basis. Based on the results of this study, the substance introduced into the soil columns increased the leaching of metals from the soil. Nickel seemed to be the most critical metal leaching from the soil. However, the nickel concentrations in the soil leachates did not exceede the quality requirements for drinking water set by the European Union (1998).
Executive summary:

The substance rapidly biodegraded in the sand soil columns. The biodegradation was studied for 110 days by pumping tap water amended with the substance through a soil texture, at an initial concentration of 1000 mg/l and a continous flow rate of 1 ml/min. Five parallel columns were used in the experiment. One of the columns was used as a control column without any substance amendment. The substance concentrations, TOC, alkalinity, pH, nitrate, nitrite, ammonium, total nitrogen, conductivity, oxygen, temperature, and concentration of trace metals were analysed from the effluents during the experiment.

According to this study, the substance or its organic degradation compounds are not likely to enter the groundwater. Ammonium was released during the biodegradation, and further oxidised via nitrate and nitrite. Additionally, formation of ammonium, nitrate and nitrite during the biodegradation might cause undesirable environmental effects to waterbodies when the substance is used as a de-icer in large scale. According to this study, it is recommended to assess these effects on a case-by-case basis. Based on the results of this study, the substance introduced into the soil columns increased the leaching of metals from the soil. Nickel seemed to be the most critical metal leaching from the soil. However, the nickel concentrations in the soil leachates did not exceede the quality requirements for drinking water set by the European Union (1998).