Passive Air Samplers As a Tool for Assessing Long-Term Trends in Atmospheric Concentrations of Semivolatile Organic Compounds

Abstract

Many attempts have been made to quantify the relationship between the amount of persistent organic pollutants sequestered by passive air sampling devices and their actual concentrations in ambient air. However, this information may not be necessary for some applications. In this study, two sets of 30 ten-year-long time series of simultaneous passive and high-volume active air sampling carried out at the Košetice observatory in the Czech Republic were used for a comparison of temporal trends. Fifteen polyaromatic hydrocarbons, seven polychlorinated biphenyls and eight organochlorine pesticides were investigated. In most cases, a good agreement was observed between the trends derived from passive and active monitoring with the exception of several compounds obviously affected by sampling artifacts. Two sampling artifacts were observed: breakthrough of high-volume sampler filters for penta- and hexachlorobenzene and semiquantitative values for PAHs with a high molecular weight. It has been suggested before that annually aggregated results of passive air monitoring may be used directly for the assessment of the long-term behavior of these compounds. The extensive set of long-term data used in this study allowed us to confirm this finding and to demonstrate that it is also possible to derive temporal trends and the compounds' half-lives in air from the passive-sampling time series.

Comparability of long-term temporal trends of POPs from co-located active and passive air monitoring networks in Europe

“…More detailed information on analytical methods and MONET sampler design is described elsewhere. 19,25 Data treatment Active air concentrations from EMEP were available either as primary (weekly) data or as monthly arithmetic means, in ng m À3 . This allowed us to construct homogenous, temporally equidistant time series in which the data are distributed regularly over time.…”

“…These irregularities prevented us from annually averaging the passive MONET concentrations, even though averaging can signicantly improve the robustness of trend estimates for equidistant time series. 19,28 We instead used the primary data in the temporal trend calculations to prevent any potential bias caused by the unequal distribution of measurements within years. For example, where available concentrations only reect part of an entire year, annual averaging could result in highly biased results for compounds with strong seasonal uctuations (HCHs, PCBs).…”

“…For the purposes of trend analysis, values below LOQ were replaced by one-half of the LOQ. 19 The potential effect of these LOQ values on the calculation of temporal trends is discussed in the Limitations section.…”

“…1,2 Results from active air sampling have been used extensively to calculate sampling rates and derive concentrations of POPs measured in short-term (#2 year) passive sampling calibration studies. 3,[8][9][10][11][12][13][14][15][16][17][18] However, besides one previous study by our group, 19 there have been no attempts to calculate and compare long-term (>5 year) temporal trends of POPs from passive monitoring to established active monitoring trends. We have previously shown that temporal trends can be directly determined from concentrations of POPs within 28 d passive samplers without derivation of air concentrations, and that these trends show strong agreement with trends from active sampling at the same location in Košetice, Czech Republic.…”

“…We have previously shown that temporal trends can be directly determined from concentrations of POPs within 28 d passive samplers without derivation of air concentrations, and that these trends show strong agreement with trends from active sampling at the same location in Košetice, Czech Republic. 19 To validate this approach for effectiveness evaluation under the Stockholm Convention, we applied the same methodology to all other sites in Europe with co-located active EMEP samplers and passive MONET samplers deployed for the more common 84 d duration with at least 5 years of data. Our aim was to evaluate the ability of a passive air monitoring network to accurately replicate long-term temporal trends of POPs derived from an established active air monitoring network, and to assess the suitability of long-term passive sampling in regions where longterm active sampling is not feasible.…”