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SPMDs, or semipermeable membrane devices, are a passive sampling device used to monitor trace levels of organic compounds with a log Kow > 3. SPMDs are an effective way of monitoring the concentrations of chemicals from anthropogenic runoff and pollution in the marine environment because of their ability to detect minuscule levels of chemical. The data collected from a passive sampler is important for examining the amount of chemical in the environment and can therefore be used to formulate other scientific research about the effects of those chemicals on the organisms as well as the environment. Examples of commonly measured chemicals using SPMDs include: PAHs , PCBs , PBDEs , dioxins and furans as well as hydrophobic waste-water effluents like fragrances, triclosan and phthalates.
To take into consideration short-lived pulses of contaminants found in surface water, passive samplers may be used to monitor and record these pulses that would otherwise be missed. SPMDs can accumulate contaminants from the water column because of triolein comprising the lipid membrane that is housed within the canister. However they are most successful in accumulating trace chemicals in surface water with a calculable flow. The amount of chemical measured using an SPMD is related to the surface area of the sampling device therefore using a larger SPMD increases the amount of chemical sampled.