Passive sampling: Difference between revisions

Revision as of 16:05, 29 January 2019

Revision as of 16:27, 25 June 2019

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===Diffusive gradients in thin films (DGT)===

{{Main|Diffusive gradients in thin films}}

Diffusive gradients in thin films (DGT) samplers passively sample [[ion]]ic trace metals, as well as [[antibiotic]]s, [[oxyanion]]s, [[bisphenol]]s, and [[nanoparticle]]s in different configurations. They are composed of plastic pistons and caps, with a window that exposes a binding gel, diffusive gel, and filter membrane to the sampling water. They can be used in both freshwater and marine environments, as well as in the water located between freshwater and marine [[sediment]] particles, called ''pore water'' or ''interstitial water''. Once the mass of accumulated contaminants on the DGT sampler is known, the DGT equation (based on [[Fick's law]]) can be used to calcuatecalculate the time averaged water concentration of contaminants.<ref name="DGT">{{cite journal |last1=Zhang |first1=Chaosheng |last2=Ding |first2=Shiming |last3=Xu |first3=Di |last4=Tang |first4=Ya |last5=Wong |first5=Ming H |title=Bioavailability assessment of phosphorus and metals in soils and sediments: a review of diffusive gradients in thin films (DGT) |journal=Environmental Monitoring and Assessment |date=2014 |volume=186 |issue=11}}</ref>

===Peepers===

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===Semipermeable membrane devices (SPMDs)===

{{Main|Semipermeable membrane devices}}

Semipermeable membrane devices (SPMDs) passively sample [[Chemical polarity|nonpolar]] organic contaminants with a log octanol-water partition coefficient (K_ow) value greater than 3. Examples of these types of chemicals include polycyclic aromatic hydrocarcbonshydrocarbons (PAHs), polychlorinated biphenyls (PCBs), [[polybrominated diphenyl ethers]] (PBDEs), chlorinated pesticides, [[dioxin]]s, and [[furan]]s. SPMDs are composed of sealed plastic tubing filled with [[triolein]], in which nonpolar organics are very soluble and which serves as a representation of the fatty tissues of aquatic organisms. The tubing is then weaved between metal rods and enclosed in a metal cage. The sampler can be made in varying lengths of tubing for different applications, since sampling rate depends on the surface area of tubing exposed to the water. As long as the amount of water passing over the sampler is known, nonpolar organic contaminant water concentrations can be calculated after extracting contaminants from a SPMD.<ref name = POCISSPMD />

[[File:Stabilized liquid membrane device (SLMD).jpg|thumb|75px |A 7.5 centimeter SLMD, filled with a 1:1 mixture of Kelex-100 and oleic acid.]]