Potassium hydrogencarbonate

Ecotoxicological Summary

Hazard for aquatic organisms

Freshwater

Hazard assessment conclusion:

no hazard identified

Marine water

Hazard assessment conclusion:

no hazard identified

STP

Hazard assessment conclusion:

no hazard identified

Sediment (freshwater)

Hazard assessment conclusion:

no hazard identified

Sediment (marine water)

Hazard assessment conclusion:

no hazard identified

Hazard for air

Air

Hazard assessment conclusion:

no hazard identified

Hazard for terrestrial organisms

Soil

Hazard assessment conclusion:

no hazard identified

Hazard for predators

Secondary poisoning

Hazard assessment conclusion:

no potential for bioaccumulation

Additional information

Potassium hydrogencarbonate is an alkaline substance, which dissociates completely in aqueous media to form potassium cations (K+) and inorganic carbon species. Emission of potassium hydrogencarbonate could therefore potentially increase the potassium concentration and pH in the aquatic environment.

In addition to the short-term toxicity studies conducted with potassium hydrogencarbonate summarised in the technical dossier, environmental toxicity data on potassium chloride were compiled in the OECD SIDS Assessment on potassium chloride (SIDS Initial Assessment Report for 13th SIAM, 2001 UNEP Publication), demonstrating that potassium (K+) is not hazardous to freshwater and seawater organisms, since the effect levels were well above 100 mg/L.

The hazard of potassium hydrogencarbonate for the environment is therefore determined by the pH effect. For this reason, the effect of potassium hydrogencarbonate on the organisms depends on the buffer capacity of the aquatic or terrestrial ecosystem. Because the buffer capacity, the pH and the fluctuation of the pH are very specific for a certain ecosystem, it was not considered useful to derive PNECs.

Furthermore, the pH of effluents is normally measured frequently and can be neutralised easily (directive 2010/75/EU on industrial emissions (integrated pollution prevention and control) requires pH monitoring of discharges). Therefore, a significant increase of the pH of the receiving water is not expected. Generally, the change in pH of the receiving water should stay within a tolerated range of the pH at the effluent site, and for these reason adverse effects on the aquatic environment are not expected due to production or use of potassium carbonate, if emissions of waste water are controlled by appropriate pH limits and/or dilutions in relation to the natural pH and buffering capacity of the receiving water.

 

The higher the buffer capacity of the water, the lower the effect on pH will be. In general, the buffer capacity preventing shifts in acidity or alkalinity in natural waters is regulated by the equilibrium between carbon dioxide (CO2), the bicarbonate ion ((HCO3)-) and the carbonate ion ((CO3)2-):

 

CO2 + H2O <-> (HCO3)- + H+ (pKa1 = 6.35)

(HCO3)- <-> (CO3)2- + H+ (pKa2 = 10.33)

 

If the pH is < 6, un-ionised CO2 is the predominant species and the first equilibrium reaction is most important for the buffer capacity. At pH values of 6-10 the bicarbonate ion is the predominant species and at pH values > 10 the carbonate ion is the predominant species. In the majority of natural waters the pH values are between 6 and 10, thus the bicarbonate concentration and the second equilibrium reaction are most important for the buffer capacity (Rand, 1995; De Groot and Van Dijk, 2002; OECD, 2002). UNEP (1995) reported the bicarbonate concentration for a total number of 77 rivers in North-America, South-America, Asia, Africa, Europe and Oceania. The 10th–percentile, mean and 90th-percentile concentrations were 20, 106 and 195 mg/l, respectively (OECD, 2002).

 

Geochemical, hydrological and/or biological processes mainly determine the pH of an aquatic ecosystem. The pH is an important parameter of aquatic ecosystems and it is a standard parameter of water quality monitoring programs. The most important freshwater aquatic ecosystems of the world revealed average annual pH values between 6.5 and 8.3, but lower and higher values have been measured in other aquatic ecosystems. In aquatic ecosystems with dissolved organic acids a pH of less than 4.0 has been measured, while in waters with a high chlorophyll content the bicarbonate assimilation can result in pH values of higher than 9.0 at midday (OECD, 2002). Also, potassium has been measured extensively in aquatic ecosystems. For example, UNEP (1995) reported the concentration for a total number of 75 rivers in North America, South-America, Asia, Africa, Europe and Oceania. The 10th -percentile, mean and 90th -percentile were 0.8 , 3.2 and 6.0 mg/l, respectively. The potassium concentration of topsoils is 0.2-3.3% (Chemical Economics Handbook, 1999), and that of seawater is 380 mg/l (Tait, 1980). For European freshwaters, there are extensive databases on physico-chemical properties, including pH, hardness (calculated from the measured calcium and magnesium concentration), alkalinity (determined by acid/base titration or calculated from the calcium concentration, see further Section 3.1.3.2) and potassium concentration.

 

Data on physico-chemical properties of freshwaters in individual European countries and the combined data for freshwaters in European countries were collected and reported by De Schamphelaere et al. (2003) and Heijerick et al. (2003). The combined European data for the above physico-chemical properties, all relevant for pH changes, are summarised below. The data in this table are based on 1991-1996 data for 411 European locations, extracted from the ‘GEMS/Water database’ (Global Environmental Monitoring System) that is mainly aimed on the large river systems. A correlation analysis on the data from all 411 locations indicate that all parameters listed below are positively correlated, i.e. an increased pH is associated with increased concentrations of Ca, Mg and Na and increased hardness and alkalinity (De Schamphelaere et al., 2003; Heijerick et al., 2003).

The variation in the above physico-chemical properties of the large river systems in different European countries is rather small, with exception of some areas in the Nordic countries (Denmark, Sweden, Norway and Finland), which are characterised by ‘soft water’ conditions, i.e. a hardness <24 mg CaCO3/l and low pH. For example, in Sweden the 50th percentile value for hardness is 15 mg CaCO3/l, which is 10-times lower than that for whole Europe. In Sweden the 50th percentile value for pH is just below 7, which is about 1 pH unit lower than that for whole Europe (De Schamphelaere et al., 2003; Heijerick et al., 2003).

 

Percentile	pH	Hardness mg/L as CaCO3	Alkalinity mg/L as CaCO3	Ca mg/L	Mg mg/L	Na mg/L
5^th	6.9	26	3	8	1.5	3
10^th	7.0	41	6	13	2	5
20^th	7.2	70	15	23	3	7
30^th	7..5	97	31	32	4	10
40^th	7.7	126	53	42	5	13
50^th	7.8	153	82	51	6	17
60^th	7.9	184	119	62	7	22
70^th	7.9	216	165	73	8	29
80^th	8.0	257	225	86	10	40
90^th	8.1	308	306	103	12	63
95^th	8.2	353	362	116	15	90

 

Seawater

In over 97% of the seawater in the world, the salinity, is 35‰. The major constituents of seawater at 35 °/oo are Cl- (19.35 g/kg), Na+ (10.77 g/kg), (SO4)2- (2.71 g/kg), Mg2+ (1.29 g/kg), Ca2+ (0.41 g/kg), K+ (0.40 g/kg) and (HCO3)- (0.142 g/kg, being the carbonate alkalinity expressed as though it were all bicarbonate, as this is the dominant species in seawater; the concentrations of CO2 and carbonate in seawater are very low compared to that of bicarbonate). The pH of seawater (ocean water) is normally 8.0-8.3, which is very similar to the vast majority of European freshwaters (8.0-8.2). The bicarbonate concentration in seawater (142 mg/kg, equivalent to 137 mg/l) is between the mean bicarbonate concentration (106 mg/l) and the 90th percentile bicarbonate concentration (195 mg/l) in European freshwaters, indicating a relatively high buffer capacity in seawater. According to the high buffer capacity, seawater is relatively insensitive to pH changes.

 

Overall, it is concluded, that there is no hazard to the environment.

 

References

EU RAR NaOH (2007). European Union Risk Assessment Report sodium hydroxide. Office for Official Publi-cations of the European Union. Luxembourg.

 

HERA (2005). Sodium carbonate (CAS 597-19-8) Ed. 2.0, April 2005, http:www.heraproject.com.

 

OECD (2001). SIDS Initial Assessment Report for 13th SIAM (Bern, 6-9 November 2001) Potassium chloride. UNEP (United nations Environment Program) PUBLICATIONS, published via Internet: http: //www. inchem. org/documents/sids/sids/KCHLORIDE. pdf.

 

OECD (2002a). Screening Information Data Set (SIDS) Initial Assessment report for sodium hydroxyde. Or-ganisation for Economic Co-operation and Development, UNEP Publication (Available on internet:http://www.chem.unep.ch/irptc/sids/OECDSIDS/INDEXCHEMIC.htm))

 

OECD SIDS (2002b) Screening Information Data Set (SIDS) Initial Assessment report for potassium hydroxyde. Organisation for Economic Co-operation and Development, UNEP Publication (Available on inter-net: http://www.inchem.org/documents/sids/sids/POTASSIUMHYD.pdf

 

OECD (2006). SIDS Initial Assessment Report for SIAM 22 (Paris, France 18-21 April 2006) Bicarbonate special. OECD (Organisation for Economic Co-operation and Development) Environmental Directorate, published via Internet: http: //www. oecd. org/document/63/0,3343, en_2649_34379_1897983_1_1_1_1,00. html.

 

De Schamphelaere, K.A.C., D.G. Heijerick and C.R. Janssen (2003) Development and Validation of Biotic Ligand Models for Predicting Chronic Zinc Toxicity to Fish, Daphnids and Algae (Final report of ILZRO project ZEH-WA-1) Laboratory of Environmental Toxicology and Aquatic Ecology, Ghent University, Belgium

 

Heijerick, D.G., K.A.C. De Schamphelaere and C.R. Janssen. 2003. Application of biotic ligand models forpredicting zinc toxicity in Europeansurface waters (Final report of ILZRO project ZEH-WA-2), Laboratory ofEnvironmental Toxicology and Aquatic Ecology, Ghent University, Belgium. (Sponsor: International Lead andZinc Research Organization, ILZRO, United States).

 

Tait, R., V. (1980).Elements of Marine ecology.University Press, Cambridge, UK. P. 91-92.

Conclusion on classification

Potassium hydrogencarbonate is not classified for the environmental compartment based on non toxic properties, its dissociation in the environment, lack of bioaccumulation, and lack of adsorption to particulate matter or surfaces.