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The following text is copied from the OECD SIDS document for sodium percarbonate (OECD 2006), section 2.2 and subsections:

"An emission of sodium percarbonate to the environment could potentially occur during production and formulation of sodium percarbonate. In most cases the household cleaning products, which contain sodium percarbonate, are added to tap water during use. After use, the spent washing liquor will be disposed via the drain. However, sodium percarbonate dissociates in water into hydrogen peroxide and sodium carbonate. Hydrogen peroxide is effectively degraded and sodium carbonate will be neutralised to sodium bicarbonate (NaHCO3) and therefore entries of sodium percarbonate into the environment via household cleaning products are unlikely. Sodium percarbonate rapidly dissolves in water and dissociates into sodium ions, carbonate ions and hydrogen peroxide.

For solid sodium percarbonate no transport to the air is expected because of the negligible vapour pressure. When sodium percarbonate is dissolved in water, it dissociates to sodium carbonate and hydrogen peroxide rather easily. The high water solubility and low vapour pressure indicate that sodium carbonate will be found predominantly in the aquatic environment (OECD, 2003). Volatilisation of hydrogen peroxide from surface waters and moist soil is expected to be very low, while it is expected to be highly mobile in soil (European Commission, 2003b). It can be concluded that the aquatic compartment is the main compartment for sodium carbonate and hydrogen peroxide.

Hydrogen peroxide

Hydrogen peroxide is a reactive substance in the presence of other substances, elements, radiation, materials or cells. Both biotic and abiotic degradation processes are important routes in removal of hydrogen peroxide in the environment:

2 H2O2 → 2 H2O + O2

Abiotic degradation of hydrogen peroxide is due to either reaction with itself (disproportionation),or reaction with transition metals, organic compounds capable of reacting with hydrogen peroxide, reaction with free radicals, heat or light (European Commission, 2003b). Hydrogen peroxide is normally a short-lived substance in the environment but half-lives vary greatly depending on the circumstances.

Sodium carbonate

Both sodium and inorganic carbonate have a wide natural occurrence (UNEP, 1995; OECD, 2003). The sodium concentration was reported for a total number of 75 rivers in North and South America, Africa, Asia, Europe and Oceania, with a 10th percentile of 1.5 mg/L, mean of 28 mg/L and 90th percentile of 68 mg/L (UNEP, 1995). Also the bicarbonate (HCO3-) concentration was reported for a total number of 77 rivers in North-America, South-America, Asia, Africa, Europe and Oceania. The 10th percentile, mean and 90th-percentile were 20, 106 and 195 mg/L, respectively. An emission of sodium carbonate to water will result in an increase in alkalinity and tendency to raise the pH value:

CO32- + H2O → HCO3- + OH-

HCO3- + H+ → CO2 + H2O

In water the carbonate ion will re-equilibrate until an equilibrium is established. The increase in pH depends on the buffer capacity of the water, which in most cases is determined by the natural background concentration of bicarbonate."

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