Beef cattle methane emissions measured with tracer-ratio and inverse dispersion modelling techniques

The development and validation of management practices to mitigate greenhouse gas (GHG) emissions from livestock require accurate emission measurements. This study assessed the accuracy of a practical inverse dispersion modelling (IDM) technique to quantify methane (CH4) emitted from a small cattle herd (16 animals) confined to a 63 m × 60 m experimental pen. The IDM technique calculates emissions from the increase in the CH4 concentration measured downwind of the animals. The measurements were conducted for 7 d. Two types of open-path (OP) gas sensors were used to measure concentration in the IDM calculation: a Fourier transform infrared spectrometer (IDM-FTIR) or a CH4 laser (IDM-Laser). The actual cattle emission rate was measured with a tracer-ratio technique using nitrous oxide (N2O) as the tracer gas. We found very good agreement between the two IDM emission estimates (308.1 ± 2.1 – mean ± SE – and 304.4 ± 8.0 g CH4 head−1 d−1 for the IDM-FTIR and IDM-Laser respectively) and the tracer-ratio measurements (301.9 ± 1.5 g CH4 head−1 d−1). This study suggests that a practical IDM measurement approach can provide an accurate method of estimating cattle emissions.

On-farm beef cattle methane emissions measured with tracer-ratio and inverse-dispersion modelling techniques

The development and validation of management practices to mitigate greenhouse gas (GHG) emissions from livestock requires accurate emission measurements. This study assessed the accuracy of a practical inverse dispersion (IDM) micrometeorological technique to quantify methane (CH4) emitted from a small cattle herd (16 animals) confined to a 63 × 60 m pen. The IDM technique calculates emissions from the increase in CH4 concentration measured downwind of the animals. Two types of open-path (OP) gas sensors were used to measure concentration in the IDM calculation: a Fourier transform infrared spectrometer (IDM-FTIR) or a CH4 Laser (IDM-Laser). The actual cattle emission rate was given by a tracer-ratio technique using nitrous oxide as the tracer gas. We found very good agreement between the two IDM emission estimates (316 and 322 g CH4 head−1 d−1 for the IDM-FTIR and IDM-Laser, respectively) and the tracer-ratio measurements (315 g CH4 head−1 d−1). This study shows that a practical IDM measurement approach can provide an accurate method of estimating cattle emissions.

Quantifying NH3 and CH4 emissions from a dairy housing using backward Lagrangian stochastic modelling

<p>Inverse dispersion modelling (IDM) using a backward Lagrangian stochastic (bLS) dispersion model has been successfully applied to quantify emissions from confined ground sources e.g. as for ammonia (NH<sub>3</sub>) loss after manure spreading. The most widely used bLS model for emission measurements of NH<sub>3</sub> and methane (CH<sub>4</sub>) from agricultural sources such as lagoons and livestock buildings is based on Flesch et al. (2004). For such applications, the model assumptions of a diffusive ground source within a homogeneous turbulence field, which implies absence of obstacles as e.g. buildings disturbing the flow, is clearly not fulfilled. It remains unclear to what extend these violations introduce bias into the emission estimates. Further, the model by Flesch et al. does not include deposition removal, which for NH<sub>3</sub>, can induce an underestimation of the emission from the source (Häni et al., 2018). Häni et al. extended the standard bLS calculation model with an optional dry deposition mechanism.</p><p>In a field campaign between mid-September and mid-December 2018, CH<sub>4</sub> and NH<sub>3</sub> emissions from a natural ventilated dairy housing with 40 cows were quantified using the IDM method with the bLS model by Häni et al. (2018). From the three-month period, results for 63 measurement days at 30-minute resolution were evaluated and thereof 71% of the data points were discarded from the emission calculation due to inapplicable turbulence conditions or instrument failure.</p><p>NH<sub>3</sub> and CH<sub>4</sub> concentrations were analysed with open-path instruments (NH<sub>3</sub>: miniDOAS,; CH<sub>4</sub>: GasFinder, Boreal Laser, Inc., Edmonton, Alberta, Canada) (aligned in parallel) with 50 m path lengths (distance between sensor and reflector). During part of the field campaign (24 days), simultaneous in-house measurements of CH<sub>4</sub> and NH<sub>3</sub> emissions using the tracer ratio method (iTM) (SF<sub>6</sub> and SF<sub>5</sub>CF<sub>3</sub>, Mohn et al., 2018) were conducted and results compared with the estimates retrieved by the IDM method. Overall, the results from the IDM method compare well to the results of the in-house measurements, with mean daily emissions of 18.3 kg CH<sub>4</sub>/d (IDM) and 17.9 kg CH<sub>4</sub>/d (iTM) and 1.08 kg NH<sub>3</sub>/d (IDM) and 1.56 kg NH<sub>3</sub>/d (iTM), respectively. Regarding NH<sub>3</sub>, the IDM method was run without the inclusion of a dry deposition mechanism. First results from IDM calculations with the inclusion of dry deposition indicate, that dry deposition modelling may explain the difference in NH<sub>3</sub> emissions between the IDM method and the iTM.</p><p><strong>References</strong></p><p>Flesch, T. K., Wilson, J. D., Harper, L. A., Crenna, B. P., and Sharpe, R. R.: Deducing ground-to-air emissions from observed trace gas concentrations: A field trial, J. Appl. Meteorol., 43, 487–502, 2004.</p><p>Häni, C., Flechard, C., Neftel, A., Sintermann, J., and Kupper, T.: Accounting for Field-Scale Dry Deposition in Backward Lagrangian Stochastic Dispersion Modelling of NH3 Emissions, Atmosphere, 9, 146, 2018.</p><p>Mohn, J., Zeyer, K., Keck, M., Keller, M., Zähner, M., Poteko, J., Emmenegger, L., and Schrade, S.: A dual tracer ratio method for comparative emission measurements in an experimental dairy housing, Atmospheric Environment, 179, 12–22, 2018.</p>

Zinc Absorption From Agronomically Biofortified Wheat Is Similar to Post-Harvest Fortified Wheat and Is a Substantial Source of Bioavailable Zinc in Humans

ABSTRACT Background Limited data exist on human zinc absorption from wheat biofortified via foliar (FBW) or root (hydroponically fortified wheat, HBW) zinc application. Stable isotope labels added at point of consumption (extrinsic labeling) might not reflect absorption from native zinc obtained by intrinsic labeling. Objectives We measured fractional and total zinc absorption (FAZ, TAZ) in FBW and HBW wheat, compared with control wheat (CW) and fortified wheat (FW). The effect of labeling method was assessed in HBW (study 1), and the effect of milling extraction rate (EXR, 80% and 100%) in FBW (studies 2 and 3). Methods Generally healthy adults (n = 71, age: 18–45 y, body mass index: 18.5–25 kg/m2) were allocated to 1 of the studies, in which they served as their own controls. In study 1, men and women consumed wheat porridges colabeled intrinsically and extrinsically with 67Zn and 70Zn. In studies 2 and 3, women consumed wheat flatbreads (chapatis) labeled extrinsically. Zinc absorption was measured with the oral to intravenous tracer ratio method with a 4-wk wash-out period between meals. Data were analyzed with linear mixed models. Results In study 1 there were no differences in zinc absorption from extrinsic versus intrinsic labels in either FW or HBW. Similarly, FAZ and TAZ from FW and HBW did not differ. TAZ was 70–76% higher in FW and HBW compared with CW (P < 0.01). In studies 2 and 3, TAZ from FW and FBW did not differ but was 20–48% higher compared with CW (P < 0.001). Extraction rate had no effect on TAZ. Conclusions Colabeling demonstrates that extrinsic zinc isotopic labels can be used to accurately quantify zinc absorption from wheat in humans. Biofortification through foliar zinc application, root zinc application, or fortification provides higher TAZ compared with unfortified wheat. In biofortified wheat, extraction rate (100–80%) has a limited impact on total zinc absorption. These studies were registered on clinicaltrials.gov (NCT01775319).

Black Carbon, Organic Carbon, and Co-Pollutants Emissions and Energy Efficiency from Artisanal Brick Production in Mexico

In many parts of the developing world and economies in transition, small-scale traditional brick kilns are a notorious source of urban air pollution. Many are both energy inefficient and burn highly polluting fuels that emit significant levels of black carbon (BC), organic carbon (OC) and other atmospheric pollutants into local communities, resulting in severe health and environmental impacts. However, only a very limited number of studies are available on the emission characteristics of brick kilns; thus there is a need to characterize their gaseous and particulate matter (PM) emission factors to better assess their overall contribution to emissions inventories and to quantify their ecological, human health, and climate impacts. In this study, the fuel-, energy-, and brick-based emissions factors and time-based emission ratios of BC, OC, inorganic PM components, CO, SO2, CH4, NOx, and selected volatile organic compounds (VOCs) from two traditional artisanal kilns and one MK2 kiln in Mexico were quantified using the tracer ratio sampling technique. Simultaneous measurements of PM components, CO and CO2 were also obtained using a filter-based sampling probe technique. Additional measurements included the internal temperature of the brick kilns, mechanical resistance of bricks produced, and characteristics of fuels employed. The results show that both techniques capture similar temporal profiles of the brick kiln emissions and produce comparable emission factors, indicating that the tracer ratio technique can be an alternative option to the filter-based sampling probe technique in understanding the temporal profile of the chemical composition of brick kilns emissions. A more integrated inter-comparison of the brick kilns' performances was obtained by simultaneously assessing emissions factors, energy efficiency, fuel consumption, and the quality of the bricks produced. Overall, a well-designed and operated MK2 kiln produced lower PM2.5, BC, OC emission factors and higher energy efficiency than the traditional artisanal brick kilns. Average fuel-based BC emission factors ranged from 0.15–0.58 g/kg-fuel whereas BC / OC mass ratios ranged from 0.9–5.2, depending on the kiln type. The results from this study contribute to the limited number of databases available on the emission characteristics of the informal brick production sector.

In-situ measurements of atmospheric hydrofluorocarbons (HFCs) and perfluorocarbons (PFCs) at the Shangdianzi regional background station, China

Atmospheric hydrofluorocarbons (HFCs) and perfluorocarbons (PFCs) were measured in-situ at the Shangdianzi (SDZ) Global Atmosphere Watch (GAW) regional background station, China, from May 2010 to May 2011. The time series for five HFCs and three PFCs showed occasionally high-concentration events while background conditions occurred for 36% (HFC-32) to 83% (PFC-218) of all measurements. The mean mixing ratios during background conditions were 24.5 ppt (parts per trillion, 10−12, molar) for HFC-23, 5.86 ppt for HFC-32, 9.97 ppt for HFC-125, 66.0 ppt for HFC-134a, 9.77 ppt for HFC-152a, 79.1 ppt for CF4, 4.22 ppt for PFC-116, and 0.56 ppt for PFC-218. The background mixing ratios for the compounds at SDZ are consistent with those obtained at mid to high latitude sites in the Northern Hemisphere. North-easterly winds were associated with negative contributions to atmospheric HFC and PFC loadings (mixing ratio anomalies weighted by time associated with winds in a given sector), whereas south-westerly advection (urban sector) showed positive loadings. Chinese emissions estimated by a tracer ratio method using carbon monoxide as tracer were 3.6 ± 3.2 kt yr−1 for HFC-23, 4.3 ± 3.6 kt yr−1 for HFC-32, 2.7 ± 2.3 kt yr−1 for HFC-125, 6.0 ± 5.6 kt yr−1 for HFC-134a, 2.0 ± 1.8 kt yr−1 for HFC-152a, 2.4 ± 2.1 kt yr−1 for CF4, 0.27 ± 0.26 kt yr−1 for PFC-116, and 0.061 ± 0.095 kt yr−1 for PFC-218. The lower HFC-23 emissions compared to earlier studies may be a result of the HFC-23 abatement measures taken as part of Clean Development Mechanism (CDM) projects that started in 2005.