Effects of Sulfamethoxazole and 2-Ethylhexyl-4-Methoxycinnamate on the Dissimilatory Nitrate Reduction Processes and N2O Release in Sediments in the Yarlung Zangbo River

Abstract

The nitrogen pollution of rivers as a global environmental problem has received great attentions in recent years. The occurrence of emerging pollutants in high-altitude rivers will inevitably affect the dissimilatory nitrate reduction processes. In this study, sediment slurry experiments combined with 15N tracer techniques were conducted to investigate the influence of pharmaceutical and personal care products (alone and in combination) on denitrification and the anaerobic ammonium oxidation (anammox) process and the resulting N2O release in the sediments of the Yarlung Zangbo River. The results showed that the denitrification rates were inhibited by sulfamethoxazole (SMX) treatments (1–100 μg L−1) and the anammox rates decreased as the SMX concentrations increased, which may be due to the inhibitory effect of this antibiotic on nitrate reducing microbes. 2-Ethylhexyl-4-methoxycinnamate (EHMC) impacted nitrogen transformation mainly though the inhibition of the anammox processes. SMX and EHMC showed a superposition effect on the denitrification processes. The expression levels of the denitrifying functional genes nirS and nosZ were decreased and N2O release was stimulated due to the presence of SMX and/or EHMC in the sediments. To the best of our knowledge, this study is the first to report the effects of EHMC and its mixtures on the dissimilatory nitrate reduction processes and N2O releases in river sediments. Our results indicated that the widespread occurrence of emerging pollutants in high-altitude rivers may disturb the nitrogen transformation processes and increase the pressure of global warming.

Contrasting Effects of Environmental Concentrations of Sulfonamides on Microbial Heterotrophic Activities in Freshwater Sediments

“…Increasing concentrations of SMZ led to increased depression of denitrification rates ( Hou et al, 2015 ). Similar results were obtained by Xu et al (2020) and Chen et al (2021) , who exposed river sediments to increasing concentrations of SMX. All these studies showed that the contamination of sediments by high concentrations of SMX or SMZ could increase the emission of nitrous oxide (N 2 O) and alter the ecological functioning of the benthic compartment.…”

“…Despite very few studies on the effects of SMX and SMZ on sediment microbial communities, it has been evidenced that the contamination of sediments by this type of substance can impact microbial processes involved in the N cycle ( Hou et al, 2015 ; Xu et al, 2020 ; Chen et al, 2021 ). In a sediment slurry incubation experiment with a dose-response design, Hou et al (2015) described a negative exponential relationship between denitrifying gene abundances and SMZ concentrations.…”

Physiological and kinetic evaluation of ampicillin oxidation as unique electron source by a denitrifying sludge

“…Liu et al ., 34 using 20–40 mg L −1 ciprofloxacin, observed low levels of N 2 O accumulated in 49 days, whereas in coastal sediments sulfamethazine concentrations higher than 50 ng L −1 resulted in N 2 O as the main denitrification product 53 . Increased N 2 O production was reported in denitrifying assays as 1–1000 ng kg −1 narasin or tetracycline was added 51 or sulfamethoxazole concentration was increased from 0.1 to 100 μg L −1 54 . Regarding this, the authors reported that the expression levels of the denitrifying functional genes for nosZ decreased as the antibiotic concentration increased, and therefore the release of N 2 O was promoted under these conditions.…”

“…53 Increased N 2 O production was reported in denitrifying assays as 1-1000 ng kg −1 narasin or tetracycline was added 51 or sulfamethoxazole concentration was increased from 0.1 to 100 μg L −1 . 54 Regarding this, the authors reported that the expression levels of the denitrifying functional genes for nosZ decreased as the antibiotic concentration increased, and therefore the release of N 2 O was promoted under these conditions. Thus Nos enzyme activity or expression of nosZ gene during denitrification might be altered according to the concentration of antibiotics present.…”

Contaminants of Emerging Concern: A Review of Biological and Economic Principles to Guide Water Management Policies

“…For instance, pollution from CECs has been shown to interact with nutrient emissions. The antibacterial properties of antibiotics inhibit microbial activity in aquatic environments, which leads to a reduction in nitrogen removal rates and a subsequent increase in the formation of N 2 O, an intermediate of the nitrate reduction process and greenhouse gas that contributes to global warming (Xu et al, 2020). Thus, more research assessing the environmental damage and risks from pollutant mixtures is of utmost importance.…”