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Benzotriazoles (BTs) are regarded as contaminants of emerging concern. However, their transformation products (BTTPs) in aquifers remains poorly characterized. The present study is the first detailed report on profiles of the BTTPs in an urban oxic intergranular aquifer related to water type, land use and the aquifer's depth. The 2-methyl-2H-benzotriazole (2-MeBT) and 2,4-dimethyl-2H-benzotriazole (2,4-dMeBT) were quantified using the gas chromatography–mass spectrometry (GC–MS) analytical technique based on internal standards. For the first time the relationship between the 2-MeBT and 2,4-dMeBT concentrations was studied in sampled water and discussed with respect to the different flow paths and sources of contamination. Three main sources of BTTPs were determined in urban groundwater: BTs and BTTPs included in the outflow of effluents from wastewater-treatment plants and energy-producing facilities into surface streams that recharge the aquifer and in the leaking effluents from industrial and public wastewater pipelines. The results confirm that the BTTPs are transformed from parent compounds in the aquifer's unsaturated zone in the case when the effluents are temporally stored in sediments with a lower hydraulic conductivity, which is indicated with the highest median concentrations of BTTPs referring to the perched aquifers where the BTTPs proportions were 92–99%. BTTPs dominated over the parent BTs also in groundwater. The highest concentrations of BTTPs (up to 174 and 144 ng L−1 for the 2-MeBT and 2,4-dMeBT ng L−1, respectively) were measured in groundwater abstracted from the upper parts of the aquifer in the area where the losses from industrial wastewater pipelines were evidenced. The 2,4-dMeBT dominated over the 2-MeBT in the BTTPs originating from BTs included in the industrial effluents, which is the opposite to the case when their origin is in the municipal effluents. The median sum concentration of the BTTPs in drinking-water resources (2.0 ng L−1) is lower than the quality criterion recommended for BTs so far. Nevertheless, the abundance of BTs in the environment and the apparent environmental relevance of the BTTPs in urban groundwater indicate the need for a risk assessment of BTTPs with respect to health and the environment.

Benzotriazoles (BTs) are considered as Contaminants of Emerging Concern (CECs); however, information about their fate in aquifers continues to be absent. This was the focus of the present study, which provides the first evidence for relevant BTs' degradation products (BTTPs) in urban aquifers that may impact the groundwater quality. The mechanisms and biotransformation pathways of BTs were investigated in an oxic intergranular medium. The BTs and BTTPs were identified and quantified by gas chromatography–mass spectrometry (GC–MS) and liquid chromatography–mass spectrometry (LC–MS) analytical techniques based on reference standards and internal materials. The major transformation products were identified as 2-methyl-2H-benzotriazole (2-MeBT) for the degradation of 1H-benzotriazole (BT) and as 2,4-dimethyl-2H-benzotriazole (2,4-dMeBT) and 1,4-dimethyl-1H-benzotriazole (1,4-dMeBT) for the degradation of 4-methyl-1H-benzotriazole (4-MeBT), and most probably also 5-methyl-1H-benzotriazole (5-MeBT). The leakage of wastewater pipelines is most probably the source of BTs. Sediments with a lower hydraulic conductivity give rise to perched aquifer conditions that lead to the temporal storage of leaking effluents and presumably the majority of BTs' transformation processes via methylation and tautomerization. The most stable BTTPs entered the saturated zone of the aquifer, where they prevailed. Concentrations up to 1500 ng L−1 were measured for the 2,4-dMeBT, which suggest a contamination risk for groundwater that is or may be used as a source for drinking water in the case of a constant input of pollutant loads from sewer systems.

Benzodiazepine derivatives are prescribed in large quantities globally and are potentially new emerging environmental contaminants. Unfortunately, a dearth of data exists concerning occurrence, persistence and fate in the environment. This paper redresses this by reviewing existing literature, assessing the occurrence of selected benzodiazepine anxiolytics (diazepam, oxazepam and bromazepam) in wastewater influent and effluent and surface water from Slovenia, evaluating their removal during water treatment and identifying the transformation products formed during water treatment. Their occurrence was monitored in hospital effluent, river water and in wastewater treatment plant influent and effluent. The study reveals the presence of benzodiazepine derivatives in all samples with the highest amounts in hospital effluents: 111 ng L −1 , 158 ng L −1 and 72 ng L −1 for diazepam, bromazepam and oxazepam, respectively. Removal efficiencies with respect to biological treatment of diazepam were 16–18% (oxic), 18–32% (anoxic → oxic), 53–76% (oxic → anoxic) and 83% (oxic → anoxic → oxic → anoxic cascade bioreactors), while the removal oxazepam was 20–24% under anoxic conditions. Coupled biological and photochemical treatment followed by the adsorption to activated carbon resulted in a removal efficiency of 99.99%. Results reveal the recalcitrant nature of benzodiazepine derivatives and suggest that only combinational treatment is sufficient to remove them. In addition, eight novel diazepam and four novel oxazepam transformation products are reported.