Passive sampling and benchmarking to rank HOC levels in the aquatic environment

Ian John Allan,Anders Ruus,Branislav Vrana,Jasperien De Weert,Norman Whitaker Green,Alfhild Kringstad,Petr Terentjev,Guttorm Christensen

doi:10.1038/s41598-021-90457-3

Abstract

The identification and prioritisation of water bodies presenting elevated levels of anthropogenic chemicals is a key aspect of environmental monitoring programmes. Albeit this is challenging owing to geographical scales, choice of indicator aquatic species used for chemical monitoring, and inherent need for an understanding of contaminant fate and distribution in the environment. Here, we propose an innovative methodology for identifying and ranking water bodies according to their levels of hydrophobic organic contaminants (HOCs) in water. This is based on a unique passive sampling dataset acquired over a 10-year period with silicone rubber exposures in surface water bodies across Europe. We show with these data that, far from point sources of contamination, levels of hexachlorobenzene (HCB) and pentachlorobenzene (PeCB) in water approach equilibrium with atmospheric concentrations near the air/water surface. This results in a relatively constant ratio of their concentrations in the water phase. This, in turn, allows us to (i) identify sites of contamination with either of the two chemicals when the HCB/PeCB ratio deviates from theory and (ii) define benchmark levels of other HOCs in surface water against those of HCB and/or PeCB. For two polychlorinated biphenyls (congener 28 and 52) used as model chemicals, differences in contamination levels between the more contaminated and pristine sites are wider than differences in HCB and PeCB concentrations endorsing the benchmarking procedure.

Highlights

The chlorinated benzenes hexachlorobenzene (HCB) and pentachlorobenzene (PeCB) are ubiquitous in the environment as result of high historical production volumes and persistence
The average HCB concentration in air measured in the North Sea region in spring and summer of 2009–2010 was 58 pg m−3 and very close to the European median background concentration of 45 pg m−3 estimated for 2 0064,5
Included were data from the mobile dynamic passive sampling unit used in the Danube river and in the Black Sea[13]. We propose that this HCB/PeCB diagnostic ratio can be used for benchmarking (i) to indicate presence of active or point pollution sources of one of the two chemicals, (ii) for benchmarking of concentrations of other chemicals sampled with silicone rubber with the aim to identify potential presence of pollution sources and compare their levels over large distances

Summary

Introduction

The chlorinated benzenes hexachlorobenzene (HCB) and pentachlorobenzene (PeCB) are ubiquitous in the environment as result of high historical production volumes and persistence. While the pattern is obvious, it is difficult to distinguish whether it is the result of actual relative changes in air concentrations of HCB and PeCB or if it is operational, i.e. because of the measurement itself with e.g. a lack of temperature correction of the passive sampling data or because of a combination of the two.

Results

Conclusion