Drug Use Changes at the Individual Level: Results from a Longitudinal, Multisite Survey in Young Europeans Frequenting the Nightlife Scene

<b><i>Background:</i></b> Monitoring emerging trends in the increasingly dynamic European drug market is vital; however, information on change at the individual level is scarce. In the current study, we investigated changes in drug use over 12 months in European nightlife attendees. <b><i>Method:</i></b> In this longitudinal online survey, changes in substances used, use frequency in continued users, and relative initiation of use at follow-up were assessed for 20 different substances. To take part, participants had to be aged 18–34 years; be from Belgium, Italy, the Netherlands, Sweden, or the UK; and have attended at least 6 electronic music events in the past 12 months at baseline. Of 8,045 volunteers at baseline, 2,897 completed the survey at both time points (36% follow-up rate), in 2017 and 2018. <b><i>Results:</i></b> The number of people using ketamine increased by 21% (<i>p</i> &#x3c; 0.001), and logarithmized frequency of use in those continuing use increased by 15% (<i>p</i> &#x3c; 0.001; 95% CI: 0.07–0.23). 4-Fluoroamphetamine use decreased by 27% (<i>p</i> &#x3c; 0.001), and logarithmized frequency of use in continuing users decreased by 15% (<i>p</i> &#x3c; 0.001, 95% CI: −0.48 to −0.23). The drugs with the greatest proportion of relative initiation at follow-up were synthetic cannabinoids (73%, <i>N</i> = 30), mephedrone (44%, <i>N</i> = 18), alkyl nitrites (42%, <i>N</i> = 147), synthetic dissociatives (41%, <i>N</i> = 15), and prescription opioids (40%, <i>N</i> = 48). <b><i>Conclusions:</i></b> In this European nightlife sample, ketamine was found to have the biggest increase in the past 12 months, which occurred alongside an increase in frequency of use in continuing users. The patterns of uptake and discontinuation of alkyl nitrates, novel psychoactive substances, and prescription opioids provide new information that has not been captured by existing cross-sectional surveys. These findings demonstrate the importance of longitudinal assessments of drug use and highlight the dynamic nature of the European drug landscape.

Impact of ozone and inlet design on the quantification of isoprene-derived organic nitrates by thermal dissociation cavity ring-down spectroscopy (TD-CRDS)

We present measurements of isoprene-derived organic nitrates (ISOP-NITs) generated in the reaction of isoprene with the nitrate radical (NO3) in a 1 m3 Teflon reaction chamber. Detection of ISOP-NITs is achieved via their thermal dissociation to nitrogen dioxide (NO2), which is monitored by cavity ring-down spectroscopy (TD-CRDS). Using thermal dissociation inlets (TDIs) made of quartz, the temperature-dependent dissociation profiles (thermograms) of ISOP-NITs measured in the presence of ozone (O3) are broad (350 to 700 K), which contrasts the narrower profiles previously observed for, for example, isopropyl nitrate (iPN) or peroxy acetyl nitrate (PAN) under the same conditions. The shape of the thermograms varied with the TDI's surface-to-volume ratio and with material of the inlet walls, providing clear evidence that ozone and quartz surfaces catalyse the dissociation of unsaturated organic nitrates leading to formation of NO2 at temperatures well below 475 K, impeding the separate detection of alkyl nitrates (ANs) and peroxy nitrates (PNs). The use of a TDI consisting of a non-reactive material suppresses the conversion of isoprene-derived ANs at 473 K, thus allowing selective detection of PNs. The potential for interference by the thermolysis of nitric acid (HNO3), nitrous acid (HONO) and O3 is assessed.

The importance of alkyl nitrates and sea ice emissions to atmospheric NO_x sources and cycling in the summertime Southern Ocean marine boundary layer

Atmospheric nitrate originates from the oxidation of nitrogen oxides (NOx = NO + NO2) and impacts both tropospheric chemistry and climate. NOx sources, cycling, and NOx to nitrate formation pathways are poorly constrained in remote marine regions, especially the Southern Ocean where pristine conditions serve as a useful proxy for the preindustrial atmosphere. Here, we measured the isotopic composition (δ15N and δ18O) of atmospheric nitrate in coarse-mode (> 1 μm) aerosols collected in the summertime marine boundary layer of the Atlantic Southern Ocean from 34.5° S to 70° S, and across the northern edge of the Weddell Sea. The δ15N-NO3− decreased with latitude from −2.7 ‰ to −43.1 ‰. The decline in δ15N with latitude is attributed to changes in the dominant NOx sources: lightning at the low latitudes, oceanic alkyl nitrates at the mid latitudes, and photolysis of nitrate in snow at the high latitudes. There is no evidence of any influence from anthropogenic NOx sources or equilibrium isotopic fractionation. Using air mass back trajectories and an isotope mixing model, we calculate that oceanic alkyl nitrate emissions have a δ15N signature of −22.0 ‰ ± 7.5 ‰. Given that measurements of alkyl nitrate contributions to remote nitrogen budgets are scarce, this may be a useful tracer for detecting their contribution in other oceanic regions. The δ18O-NO3− was always less than 70 ‰, indicating that daytime processes involving OH are the dominant NOx oxidation pathway during summer. Unusually low δ18O-NO3− values (less than 31 ‰) were observed at the western edge of the Weddell Sea. The air mass history of these samples indicates extensive interaction with sea ice covered ocean, which is known to enhance peroxy radical production. The observed low δ18O-NO3− is therefore attributed to increased exchange of NO with peroxy radicals, which have a low δ18O, relative to ozone, which has a high δ18O. This study reveals that the mid- and high-latitude surface ocean may serve as a more important NOx source than previously thought, and that the ice-covered surface ocean impacts the reactive nitrogen budget as well as the oxidative capacity of the marine boundary layer.

Thermal dissociation cavity-enhanced absorption spectrometer for measuring NO₂, RO₂NO₂, and RONO₂ in the atmosphere

We developed thermal dissociation cavity-enhanced absorption spectroscopy (TD-CEAS) for the in situ measurement of NO2, total peroxy nitrates (PNs, RO2NO2), and total alkyl nitrates (ANs, RONO2) in the atmosphere. PNs and ANs were thermally converted to NO2 at the corresponding pyrolytic temperatures and detected by CEAS at 435–455 nm. The instrument sampled sequentially from three channels at ambient temperature, 453 and 653 K, with a cycle of 3 min, to measure NO2, NO2+ PNs, and NO2+ PNs + ANs. The absorptions between the three channels were used to derive the mixing ratios of PNs and ANs by spectral fitting. The detection limit (LOD, 1σ) for retrieving NO2 was 97 parts per trillion by volume (pptv) in 6 s. The measurement uncertainty of NO2 was 9 %, while the uncertainties of PN and AN detection were larger than those of NO2 due to chemical interferences that occurred in the heated channels, such as the reaction of NO (or NO2) with the peroxy radicals produced by the thermal dissociation of organic nitrates. Based on laboratory experiments and numerical simulations, we created a lookup table method to correct these interferences in PN and AN channels under various ambient organic nitrates, NO, and NO2. Finally, we present the first field deployment and compare it with other instruments during a field campaign in China. The advantages and limitations of this instrument are outlined.

Impact of ozone and inlet design on the detection of isoprene-derived organic nitrates by thermal dissociation cavity ring-down spectroscopy (TD-CRDS)

We present measurements of isoprene-derived organic nitrates (ISOP-NITs) generated in the reaction of isoprene with the nitrate radical (NO3) in a 1 m3 Teflon reaction chamber. Detection of ISOP-NITs is achieved via their thermal dissociation to nitrogen dioxide (NO2), which is monitored by cavity ring-down spectroscopy (TD-CRDS). Using thermal dissociation inlets (TDIs) made of quartz, the temperature-dependent dissociation profiles (thermograms) of ISOP-NITs measured in the presence of ozone (O3) are broad (350 to 700 K), which contrasts the narrower profiles previously observed for e.g. isopropyl nitrate (iPN) or peroxy acetyl nitrate (PAN) under the same conditions. The shape of the thermograms varied with the TDI’s surface to volume ratio and with material of the inlet walls, providing clear evidence that ozone and quartz surfaces catalyse the dissociation of unsaturated organic nitrates leading to formation of NO2 at temperatures well below 475 K, impeding the separate detection of alkyl nitrates (ANs) and peroxy nitrates (PNs). We present a simple, viable solution to this problem and discuss the potential for interference by the thermolysis of nitric acid (HNO3), nitrous acid (HONO) and O3.

On the importance of atmospheric loss of organic nitrates by aqueous-phase ●OH oxidation

Organic nitrates are secondary species in the atmosphere. Their fate is related to the chemical transport of pollutants from polluted areas to more distant zones. While their gas-phase chemistry has been studied, their reactivity in condensed phases is far from being understood. However, these compounds represent an important fraction of organic matter in condensed phases. In particular, their partition to the aqueous phase may be especially important for oxidized organic nitrates for which water solubility increases with functionalization. This work has studied for the first time the aqueous-phase ⚫OH-oxidation kinetics of four alkyl nitrates (isopropyl nitrate, isobutyl nitrate, 1-pentyl nitrate, and isopentyl nitrate) and three functionalized organic nitrates (α-nitrooxyacetone, 1-nitrooxy-2-propanol, and isosorbide 5-mononitrate) by developing a novel and accurate competition kinetic method. Low reactivity was observed, with kOH ranging from 8×107 to 3.1×109 L mol−1 s−1 at 296±2 K. Using these results, a previously developed aqueous-phase structure–activity relationship (SAR) was extended, and the resulting parameters confirmed the extreme deactivating effect of the nitrate group, up to two adjacent carbon atoms. The achieved extended SAR was then used to determine the ⚫OH-oxidation rate constants of 49 organic nitrates, including hydroxy nitrates, ketonitrates, aldehyde nitrates, nitrooxy carboxylic acids, and more functionalized organic nitrates such as isoprene and terpene nitrates. Their multiphase atmospheric lifetimes towards ⚫OH oxidation were calculated using these rate constants, and they were compared to their gas-phase lifetimes. Large differences were observed, especially for polyfunctional organic nitrates: for 50 % of the proposed organic nitrates for which the ⚫OH reaction occurs mainly in the aqueous phase (more than 50 % of the overall removal), their ⚫OH-oxidation lifetimes increased by 20 % to 155 % under cloud/fog conditions (liquid water content LWC = 0.35 g m−3). In particular, for 83 % of the proposed terpene nitrates, the reactivity towards ⚫OH occurred mostly (>98 %) in the aqueous phase, while for 60 % of these terpene nitrates, their lifetimes increased by 25 % to 140 % compared to their gas-phase reactivity. We demonstrate that these effects are of importance under cloud/fog conditions but also under wet aerosol conditions, especially for the terpene nitrates. These results suggest that considering aqueous-phase ⚫OH-oxidation reactivity of biogenic nitrates is necessary to improve the predictions of their atmospheric fate.

Thermal dissociation cavity enhanced absorption spectrometer for detecting NO₂, RO₂NO₂ and RONO₂ in the atmosphere

We developed a thermal dissociation cavity enhanced absorption spectroscopy (TD-CEAS) for the in-situ measurement of NO2, total peroxy nitrates (PNs, RO2NO2), and total alkyl nitrates (ANs, RONO2) in the atmosphere. PNs and ANs are thermally converted to NO2 at the corresponding pyrolysis temperatures and detected by CEAS at 435–455 nm. The instrument samples sequentially from three channels at ambient temperature, 453 K and 653 K, with a cycle of 3 minutes, for measuring NO2, NO2+PNs, and NO2+PNs+ANs, respectively. The absorptions between the three channels are used to derive the mixing ratios of PNs and ANs by the spectral fitting. The limit of detection (LOD) is estimated to be 97 pptv (1σ) at 6 s intervals for NO2. The measurement uncertainty of NO2 is estimated to be 8 %, while the uncertainties of PNs and ANs detection is larger than NO2 due to some chemical interferences in the heating channels, such as the reaction of NO (or NO2) with the peroxy radicals produced by the thermal dissociation of organic nitrates. Based on the laboratory experiments and numerical simulations, we set up a lookup table method to correct these interferences in PNs and ANs channel under various concentrations of ambient organic nitrates, NO, and NO2. Finally, we present the first field deployment and compared it with other instruments during a field campaign in China, the advantage and limitations of this instrument are outlined.