Late season pharmaceutical fate in wetland mesocosms with and without phosphorous addition

Crushed recycled glass as a substrate for constructed wetland wastewater treatment: a case study of its potential to facilitate pharmaceutical removal

The use of recycled glass as a substrate for constructed wetlands was assessed through two studies. The first study examined the dissipation of atenolol, carbamazepine, and sulfamethoxazole in mesocosm-modeled wetlands using glass or limestone gravel as substrates, with or without cattails (Typha spp.). Following pseudo-first-order kinetics, atenolol dissipated the fastest from the water surface of the mesocosms (t_1/2~1 day), followed by sulfamethoxazole (t_1/2~14 days), and carbamazepine (t_1/2~48 days), with no significant differences across treatments. Increased half-lives were observed at greater depth, likely due to light screening. A Monte Carlo sensitivity analysis diagnosed sunlight absorption rates and second-order hydroxyl-mediated indirect photolysis rates to be the main sources of uncertainty in our dissipation rate estimates, compared to our observed rates. The second study examined in situ pharmaceutical removal in tertiary pilot-scale subsurface filters made of crushed recycled glass or sand in a wastewater treatment facility in Manitoba, Canada. Glass and sand showed no significant differences for pharmaceutical removals; atenolol and metoprolol were removed below limits of detection, while carbamazepine and sulfamethoxazole persisted over a retention time of 24 h. Overall, recycled glass performed similarly to traditional substrates for wetland-based wastewater treatment.

Occurrence, distribution, and ecological risk of pharmaceuticals in a seasonally ice-sealed river: From ice formation to melting

Occurrence, distribution, and ecological risk of 21 pharmaceuticals in the Jilin Songhua River were investigated during its freeze-thaw periods, including ice formation, sealed, and breakup. Florfenicol was the most abundant pharmaceutical, with mean concentrations of 123.4 ± 61.1 ng L^-1 in water and 73.8 ± 66.3 ng kg^-1 in ice. Sulfadiazine occurred at a higher mean concentration in downstream areas (45.6 ± 7.4 ng L^-1) than in upstream areas (0.7 ± 0.7 ng L^-1). Most pharmaceuticals appeared in relatively high concentrations in water during the ice-breakup period. Complex factors including pharmaceutical usage patterns, ice-regulated photodegradation, biodegradation, water flow, and freeze-concentration effects, as well as the release of pharmaceuticals from ice, were responsible for the temporal variation of pharmaceuticals. Pseudo-ice/water distribution coefficients showed the distribution of pharmaceuticals in ice and demonstrated the effects of their release from the ice on their temporal variations. Most pharmaceuticals posed a risk to algae; of these, amoxicillin exhibited the highest risk. In addition, thawing increased the concentration of thiamphenicol in water, which elevated its ecological risk level. The findings suggest that the pharmaceuticals retained in ice should be considered with regard to regulating pharmaceuticals' temporal variations in seasonal ice-covered rivers during the freeze-thaw process.

Response of the mayfly (Cloeon dipterum) to chronic exposure to thiamethoxam in outdoor mesocosms

Thiamethoxam is a widely used neonicotinoid insecticide that has been detected in surface water monitoring programs in North America and Europe. This has led to questions about its toxicity to nontarget insects, specifically those with an aquatic life stage. To address the uncertainty associated with possible impacts from environmental exposures, a chronic (35-d) outdoor mesocosm study with a formulated product containing thiamethoxam was conducted. The specific focus of the study was the response of mayflies (Ephemeroptera), which have been reported to be particularly sensitive in laboratory studies. A range of concentrations (nominally 0.1, 0.3, 1.0, 3.0, and 10.0 µg/L thiamethoxam), plus untreated controls were tested, and the abundance and emergence of mayflies (Cloeon dipterum) were assessed weekly for 35 d. Mean measured time-weighted average exposures were within 6% of nominal over the duration of the study, with the mean half-life of thiamethoxam in each treatment ranging from 7 to 13 d. Statistically significant reductions in both larval abundance and adult emergence were observed at 10.0, 3.0, and 1.0 μg/L following 1, 2, and 3 wk of exposure, respectively. Exposure to 0.1 and 0.3 µg/L thiamethoxam had no statistically significant effect on larval mayfly abundance or adult emergence at any point in the study. These findings support a 35-d no-observed-effect concentration (NOEC) of 0.3 µg thiamethoxam/L for mayflies (C. dipterum) under chronic conditions. Furthermore, because the 95th percentile of environmental concentrations has been reported to be 0.054 µg/L, these results indicate that populations of C. dipterum and similarly sensitive aquatic insects are unlikely to be significantly impacted by thiamethoxam exposure in natural systems represented by the conditions in our study. Environ Toxicol Chem 2018;37:1040-1050. © 2017 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals, Inc. on behalf of SETAC.