A substance that can dissolve in water is soluble.
A soluble toxic Poisonous; can injure or kill people or other organisms substance spilled into the water could contaminate water intakes and the marine food web, if its concentration reaches a hazardous level. It also could harm marine animals or plants.
The concentration of a dissolved substance is likely to be highest in small water bodies and/or places where there is little mixing by waves and currents.
An insoluble substance doesn't dissolve in water. If spilled into the water, if it's denser than water, it will sink to the bottom. There, it can endanger bottom-dwelling animals, such as shellfish beds.
An insoluble substance spilled into the water, if it's less dense than water, will float on the surface and can beach on shore. At the surface or on shore, it can endanger animals that spend time at the surface, such as seabirds and marine mammals.
Check the substance's CAMEO Chemicals data sheet to find out about its water solubility.
How a spilled hazardous substance could damage marine or aquatic life or become a public health hazard depends on its water solubility, and its toxicity. Water solubility is the maximum amount of a substance that can dissolve in water at a given temperature and pressure. Conditions that influence whether the maximum amount of a substance will dissolve and how long the process will take include:
Temperature: higher temperatures promote faster dissolving.
Mixing: more stirring by waves or currents promotes faster dissolving.
Water solubility is shown in percent and also in
other units (usually at 68 degrees F). For example, the solubility of
vinyl acetate in water is 2% (100 mg/mL, 20,000 mg/L). A solution of vinyl
acetate in water can hold up to 2% vinyl acetate when the temperature
is about 68 degrees F.
A substance that's completely soluble in water--100% can dissolve--is called miscible.
Whether a hazardous substance is water soluble affects how it can cause harm if spilled into a water body. Generally,
An insoluble substance, if it's denser than water, will sink to the bottom. There, it could harm bottom-dwelling marine animals. For example, it could smother shellfish beds.
An insoluble substance, if it's less dense than water, would float on the water surface and could beach on the shore. If it's toxic Poisonous; can injure or kill people or other organisms or flammable Easy to ignite and burns readily, its evaporating vapor could create a hazardous vapor cloud. A floating hazardous substance also could harm seabirds or marine mammals, as well as shore animals if it were to beach.
A soluble substance could form a plume in the water column. If it is toxic, it could contaminate water intakes or marine food webs, or injure marine animals.
Two factors influence how harmful a soluble hazardous substance could be in the water: dissolving rate and the volume of water available:
Dissolving rate. A substance that dissolves faster can reach higher concentrations in water than substances that dissolve more slowly. When dissolving takes less time, there's less time for waves and currents to disperse and dilute the dissolved substance. Higher concentrations of a hazardous substance are more likely to cause harm. More...
Some substances dissolve in a few seconds or minutes. Others require days or weeks. Water solubility doesn't directly tell you the rate at which the substance will dissolve in water, but generally:
More soluble substances usually dissolve faster.
Substances dissolve faster at higher temperatures.
Substances dissolve faster where there's more mixing energy, such as areas of strong currents or wave action.
Volume of water available. In the ocean or a U.S. Great Lake, even a large volume of a toxic substance can be diluted down to harmless concentrations relatively quickly, especially if waves or currents contribute a lot of mixing energy. When a toxic substance is spilled into a small body of water such as a canal or diked area, the concentration of the substance is more likely to reach a dangerous level, because less water is available to dilute the solution.
Besides these factors, consider a substance's toxicity when assessing its potential to harm marine life. Some substances with low solubilities can harm marine organisms because they also are toxic at low concentrations. DDT is an example: its solubility ranges from about 1 to 7 ppb Parts per billion, but it also is toxic to invertebrates at these low concentrations.
Follow the steps below to find out about a substance's solubility:
Open CAMEO Chemicals' Search window (opens new window), and type in the chemical's name and/or CAS or UN/NA number. Click Search.
In the Search Results pages, find the chemical, and click View Data Sheet.
Scroll down to "Section 4 - Physical Properties." Scroll through the list of properties to find the water solubility (e.g., "Water Solubility: greater than or equal to 100 mg/mL at 68 deg F"). Examples:
Sulfuric acid is miscible (dissolves completely) in water:
Cyanogen is 1% soluble in water (slightly soluble):
Cimetidine's solubility in water is is 5.0 mg/mL at 68 degrees F (slightly soluble):
If the water solubility isn't in the properties list, scroll up to "Section 1 - Chemical Identifiers." Review the General Description of the chemical, which often describes the chemical's behavior in water (e.g., "Mixes with water," "Sinks and mixes with water," or "Completely miscible Completely soluble with water"). Examples:
Allyl glycidyl ether is insoluble in water:
O-chlorotoluene is slightly soluble in water:
If the chemical of concern is soluble, also check whether it is water-reactive.
