Local variability in snow concentrations of chlorinated persistent organic pollutants as a source of large uncertainty in interpreting spatial patterns at all scales

Abstract

Single point sampling, a widespread practice in snow studies in remote areas, due to logistical constraints, can present an unquantified error to the final study results. The low concentrations of studied chemicals, such as chlorinated persistent organic pollutants, contribute to the uncertainty. We conducted a field experiment in the Arctic to estimate the error stemming from differences in the composition of snow at short distances (1-3 m), including 13 single organochlorine pesticides and 6 polychlorinated biphenyls, thus providing the most detailed published dataset on the subject. We contrasted this variability with the uncertainty at larger spatial scales, both within one valley (regional scale, this study) and as described in the worldwide literature.The range of values for the coefficient of variation for local samples was 20-58% for single organochlorine pesticides (OCPs) and 33-54% for polychlorinated biphenyls (PCBs), and for regional samples it was 21-69% for OCPs and 65-93% for PCBs. We suggest that, to observe the actual changes in the concentration of selected compounds in snow, they should vary at the level of 40-60%, depending on the compound in question. The uncertainty margin remains much smaller than the current discrepancy between observation data and atmospheric deposition models considering snow, deeming field data on snow concentrations a useful ground-truthing dataset. However, field observations on spatial differences at all scales need to be interpreted with caution, and the dataset provided here on the local sampling uncertainty helps define the margins of such interpretations.

Review of scientific literature on available methods of assessing organochlorine pesticides in the environment

“…Therefore, provided the sensitivity of the method is appropriate, an analytical method with low recovery may be suitable for a particular analyte [ 79 ]. Extremely low recoveries were observed in snow (27 %) [ 80 ], glacier-ice core (9.67 %) [ 81 ], water (22.42 %) [ 82 ], and air (38.2 %) [ 51 ] ( Table 2 ). Samples with poor recoveries are often discarded, as was the case with 220 samples that have <40 % recoveries in one study [ 76 ], likewise HCB with recovery 3.35 % and other recoveries <60 % were discarded [ 15 ].…”

“…2x10-6 -7. 8x10-5 CRM: (27–137 Internal standard: 70–98 10–25 GC-MS: “Initial temperature of oven at 40 °C for 2 min, 150 °C (0 min) at the rate of 25 °C min− 1, reaching 200 °C at 0 °C min− 1, 280 °C at 10 °C min− 1 and finally attaining the temperature of 300 °C at 5 °C min− 1 with final holding time of 5 min” RT 12.90–13.90 [ 80 ] Glacier-ice core 25 4 × 10 −6 -1.53 × 10 −4 9.67–112.4 GC-MS: splitless, “temperature program: 80 °C (2.00 min) to 110 °C at 7 °C min-1 then 3 °C min-1 to 250 °C and a final ramp of 10 °C min-1 to 285 °C with a hold of 5 min” ECDs: “temperature program: 80 °C for 2.00 min, then 10 °C min-1 to 150 °C then 2 °C min-1 to 280 °C hold for 5 min. Hydrogen was used as a carrier at 1.0 mL min-1” [ 81 ] Water wells 20 0.02–0.74 0.05–2.46 GC-MS: “the initial temperature of 90 °C (hold 1.3 min), increased to 125 °C at 15 °C/min, 165 °C at 5 °C/min, 195 °C at 2.5 °C/min, and finally, it was increased to 280 °C at 20 °C/min (hold for 4 min)”.…”

Polychlorinated Biphenyls in the Snow Cover of South-Eastern Kazakhstan

“…Thus, the toxicity equivalent (TEQ) established by the World Health Organization (WHO, 2005) was calculated by summing the congener-specific toxic equivalence coefficients (TEFs) [16]. TEFs are an integral part of the toxic equivalent (TEQ) concept and have been developed for dioxins/dioxin-like compounds over the past two and a half decades [17][18][19][20][21][22][23][24][25][26].…”