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Abstract Environmental factors such as nutrient and light availability may play important roles in determining the magnitude and direction of microbial priming and detrital decomposition and, therefore, the relative importance of microbial priming in carbon (C) dynamics in freshwater ecosystems.We integrated light availability with an existing conceptual model predicting the magnitude of the priming effect (PE) along a dissolved nutrient gradient (i.e.nutrientPE model). Our modifiedlight‐nutrientPE model hypothesises how light may mediate priming at any given nutrient concentration and provides a calculation method for quantitative PE values (i.e. light effect size at a given nutrient concentration).We used recirculating stream mesocosms withQuercus stellata(post oak) leaf litter as an organic matter (OM) substrate in a 150‐day experiment to test our model predictions. We manipulated light levels [ambient (full light), shaded (c.19% of ambient)] and phosphorus (P) concentration (10, 100, 500 µg PO4‐P/L) in a fully factorial design. We also supplied all mesocosms with 500 µg/L dissolved inorganic nitrogen. Microbial biomass, water column dissolved organic C, and leaf litter dry mass and recalcitrant OM [i.e. the fibre (cellulose + lignin) component of post oak substrate] were measured. Recalcitrant OM (ROM)k‐rates (day−1) were used to calculate the light effect size within P treatments as a log response ratio (ln[ambientk‐rate/shadek‐rate]) to ascertain PE magnitude and direction (positive or negative).Light was an important driver of dissolved organic C, a potential source of additional labile organic matter essential for priming heterotrophic microbes. There were weak PEs in total leaf litter dry mass remaining, but PEs were more pronounced in leaf litter ROM remaining. The strongest positive PEs (specific to litter ROM pools) occur in the highest P treatment, presumably due to a change in which nutrient, nitrogen versus P, was a limiting factor for microbes based on nutrient ratios rather than P concentration alone. These results illustrate the importance of considering light levels, nutrient ratios (rather than individual nutrients), and detrital ROM components in further PE model development.
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Quantification of pharmaceuticals in the sealant fluids of actively used waterless urinals
Abstract Prior measurements at bench scale revealed that waterless urinal cartridges containing oily sealant fluids are capable of partitioning pharmaceuticals from urine and therefore reducing their concentration in wastewater. We sought to measure pharmaceutical removal from in‐use waterless urinals. We developed a method to quantify pharmaceuticals in the sealant phase, which resulted in 79 ± 30% and 71 ± 30% recovery of eight pharmaceuticals from two sealant fluids, respectively. The method was applied to sealant samples collected over three weeks from in‐use waterless urinals on a university campus. Six of eight pharmaceuticals were present in the sealant samples from 1.4 µg/L to 241 µg/L. Loads of the six pharmaceuticals detected in the sealants were removed from the receiving wastewater from 0.02 µg/day to 3.4 µg/day across the sampling period. The concentration of the pharmaceuticals were similar over time, indicating rapid saturation and washout of the sealant. We also observed relatively rapid loss of sealant at maintenance intervals consistent with the manufacturer's instructions. These findings indicate that while waterless urinals do remove some pharmaceuticals from the wastewater stream, meaningful changes to wastewater concentrations will only result if the sealant fluid and/or the urinal cartridge are significantly modified. Practitioner pointsWe developed a quantification method for pharmaceuticals in oily waterless urinal sealants.Pharmaceuticals were present at relatively low concentrations in the sealant phase of two in‐use waterless urinals.We identify engineering challenges that must be overcome to meaningfully reduce pharmaceutical loads in wastewater with waterless urinals.
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- Award ID(s):
- 1804255
- PAR ID:
- 10449919
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Water Environment Research
- Volume:
- 93
- Issue:
- 10
- ISSN:
- 1061-4303
- Page Range / eLocation ID:
- p. 1837-1845
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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