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Street-level emissions of methane and nitrous oxide from the wastewater collection system in Cincinnati, Ohio.

ABSTRACT: Recent studies have indicated that urban streets can be hotspots for emissions of methane (CH4) from leaky natural gas lines, particularly in cities with older natural gas distribution systems. The objective of the current study was to determine whether leaking sewer pipes could also be a source of street-level CH4 as well as nitrous oxide (N2O) in Cincinnati, Ohio, a city with a relatively new gas pipeline network. To do this, we measured the carbon (?13C) and hydrogen (?2H) stable isotopic composition of CH4 to distinguish between biogenic CH4 from sewer gas and thermogenic CH4 from leaking natural gas pipelines and measured CH4 and N2O flux rates and concentrations at sites from a previous study of street-level CH4 enhancements (77 out of 104 sites) as well as additional sites found through surveying sewer grates and utility manholes (27 out of 104 sites). The average isotopic signatures for ?13C-CH4 and ?2H-CH4 were -48.5‰ ± 6.0‰ and -302‰ ± 142‰. The measured flux rates ranged from 0.0 to 282.5?mg CH4 day-1 and 0.0-14.1?mg N2O day-1 (n?=?43). The average CH4 and N2O concentrations measured in our study were 4.0?±?7.6?ppm and 392?±?158?ppb, respectively (n?=?104). 72% of sites where fluxes were measured were a source of biogenic CH4. Overall, 47% of the sampled sites had biogenic CH4, while only 13% of our sites had solely thermogenic CH4. The other sites were either a source of both biogenic and thermogenic CH4 (13%), and a relatively large portion of sites had an unresolved source (29%). Overall, this survey of emissions across a large urban area indicates that production and emission of biogenic CH4 and N2O is considerable, although CH4 fluxes are lower than those reported for cities with leaky natural gas distribution systems.

SUBMITTER: Fries AE

PROVIDER: S-EPMC6537879 | biostudies-literature | 2018 May

REPOSITORIES: biostudies-literature

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Street-level emissions of methane and nitrous oxide from the wastewater collection system in Cincinnati, Ohio.

Fries Anastasia E AE Schifman Laura A LA Shuster William D WD Townsend-Small Amy A

Environmental pollution (Barking, Essex : 1987) 20180202

Recent studies have indicated that urban streets can be hotspots for emissions of methane (CH4) from leaky natural gas lines, particularly in cities with older natural gas distribution systems. The objective of the current study was to determine whether leaking sewer pipes could also be a source of street-level CH4 as well as nitrous oxide (N2O) in Cincinnati, Ohio, a city with a relatively new gas pipeline network. To do this, we measured the carbon (δ13</s ...[more]

PMID: 29414346

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Project description:Streams and river networks are increasingly recognized as significant sources for the greenhouse gas nitrous oxide (N2 O). N2 O is a transformation product of nitrogenous compounds in soil, sediment and water. Agricultural areas are considered a particular hotspot for emissions because of the large input of nitrogen (N) fertilizers applied on arable land. However, there is little information on N2 O emissions from forest streams although they constitute a major part of the total stream network globally. Here, we compiled N2 O concentration data from low-order streams (~1,000 observations from 172 stream sites) covering a large geographical gradient in Sweden from the temperate to the boreal zone and representing catchments with various degrees of agriculture and forest coverage. Our results showed that agricultural and forest streams had comparable N2 O concentrations of 1.6 ± 2.1 and 1.3 ± 1.8 µg N/L, respectively (mean ± SD) despite higher total N (TN) concentrations in agricultural streams (1,520 ± 1,640 vs. 780 ± 600 µg N/L). Although clear patterns linking N2 O concentrations and environmental variables were difficult to discern, the percent saturation of N2 O in the streams was positively correlated with stream concentration of TN and negatively correlated with pH. We speculate that the apparent contradiction between lower TN concentration but similar N2 O concentrations in forest streams than in agricultural streams is due to the low pH (<6) in forest soils and streams which affects denitrification and yields higher N2 O emissions. An estimate of the N2 O emission from low-order streams at the national scale revealed that ~1.8 × 109 g N2 O-N are emitted annually in Sweden, with forest streams contributing about 80% of the total stream emission. Hence, our results provide evidence that forest streams can act as substantial N2 O sources in the landscape with 800 × 109 g CO2 -eq emitted annually in Sweden, equivalent to 25% of the total N2 O emissions from the Swedish agricultural sector.

Dataset Information

Street-level emissions of methane and nitrous oxide from the wastewater collection system in Cincinnati, Ohio.

Publications

Street-level emissions of methane and nitrous oxide from the wastewater collection system in Cincinnati, Ohio.

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