DOAS for flue gas monitoring—II. Deviations from the Beer-Lambert law for the UV/visible absorption spectra of NO, NO2, SO2 and NH3

Deviations from the Beer-Lambert law were studied for the differential absorption cross-sections for NO, SO2, NO2 and NH3. This was performed by simple calculations, computer simulations of spectra and by recordings of spectra for the above mentioned species at various total columns. The linearity studies for the DOAS instrument displayed large variations for the molecules studied and for different wavelength bands. In a calculation it was shown that the optical depth deviated from a linear concentration dependence by a term which was directly proportional to the statistical variance of the true absorption cross sections and proportional to the square of the total column, under the assumption of a boxcar instrument lineshape. Species exhibiting little variance or fine structure in their spectra, for instance NO2, displayed a larger linear region compared with molecules exhibiting a rich structure, i.e., NO. The former species was linear to a total column of 3150 mg/m2, which correspond to a maximum optical depth of 0.7, while the latter was linear to only 6 mg/m2, corresponding to a maximum optical depth of 0.024, in the resolution range studied. The linear regions for the other species studied were 90 mg/m2 for SO2 at 230 nm, 180 mg/m2 for SO2 at 300 nm and 36 mg/m2 for NH3. The main effect of the nonlinearity was to cause a reduction in the peak height of the absorption. It was shown that the nonlinearity effect is independent on the spectral resolution when a large number of absorption lines are covered by the bandpass of the instrument. It was also shown that the largest change in linearity occurs when the resolution is similar in magnitude to the absorption linewidth. The nonlinear behavior for NO varied less than 2% in the temperature range 300–1000 K and the spectral resolution range 0.25–1 nm. The nonlinearity effect caused quantitative rather than qualitative changes of the spectral features and typical relative errors can be as high as 35% in a flue gas

Surveillance of Sulfur Fuel Content in Ships at the Great Belt Bridge 2020

Results are reported from stack gas emission measurements of individual ships at the Great Belt Bridge in Denmark. From the data the fuel sulfur content (FSC) used by the ships has been estimated. The project has been carried out on behalf of the Danish Environmental Pro-tection Agency and this report covers the period December 2019 to November 9, 2020. The overall aim of the project was to carry out operational surveillance of ships with respect to the EU sulfur directive that was entered into force in 2015 and which is implemented in the Danish legislation. It requires the usage of low sulfur marine fuel in SECAs (0.10 %) or using abate-ment technique (e.g. scrubber), The main purpose of the surveillance was to guide further port state control of ships at the destination harbors of the ships, both in Denmark and other ports, and to gather general statistics about compliance rates.This report describes the technical systems and their performance and discusses the general compliance levels with respect to the EU sulfur directive and Danish legislation. The surveil-lance measurements were conducted by automatic gas sniffer measurements at the Great Belt Bridge, reporting in real time to a web database. The measurement systems have been developed by Chalmers University of Technology through Swedish national funding and EU projects. The measurement system at the Great Belt Bridge has been in operation since 2015.In the period December 2019 to November 9, 2020, 3910 valid sniffer measurements of indi-vidual ships were carried out at the Great Belt Bridge with medium and good quality. The pre-cision of the fixed sniffer is estimated as 0.04 FSC % (1σ) and therefore only ships running with an FSC of 0.18 % (2σ) or higher can be detected as non-compliant ships with reasonable statistical confidence. The sniffer also has an estimated systematic bias of - 0.077 % FSC for the measurements in 2020, based on comparisons with port state control authorities. This bias, together with the measurement precision, is accounted for when determining the non-compliance threshold value. The data for the period December 2019 to November 9, 2020 shows a compliance rate of 98.6 %. This corresponds to 55 non-compliant ships (1.4 %) and out of these only 1 ship (i.e. 0.03 %) was in gross non-compliance, i.e. running with FSC above 0.3 % while the rest had an FSC below 0.14 %. This is slightly lower than in 2019 (4 ships corresponding to 0.075% above FSC 0.3 %) and it can be compared to the correspond-ing numbers for 2018 when the compliance rate was 95.3 % and 1.8 % of the ships were in gross noncompliance. One reason for the improvements could be that scrubber installations appears to work better in 2019 and 2020 compared to the previous years.The observed high and improved compliance rate in 2020 is similar to the measurements in 2019 and consistent with other measurement studies in northern Europe during 2019. Airborne mini-sniffer measurements of 600 ships around the coast of Denmark, on behalf of the Danish EPA, shows 50 % less noncompliance between 2018 and 2019, with only 3 ships above FSC of 0.3 %. Sniffer measurements carried out in Belgian waters, in the English Channel, by fixed wing aircraft show that the non-compliance rates of ships with FSC above 0.4% changed from 4.9 % to 0.4 % between 2018 and 2019, with similar values in 2020. Fixed site measurements in the ship channel to Hamburg shows improved compliance rates since 2015 with noncompli-ance rates less than 1 % in Wedel and Bremerhaven in 2019. Sniffer measurements at the 6resund Bridge by Chalmers University of Technology, on behalf of Swedish transport agency, shows 99.7% compliance rates in 2020 with no ships in gross noncompliance.https://www2.mst.dk/Udgiv/publications/2020/12/978-87-7038-250-2.pd

DOAS for flue gas monitoring—III. In-situ monitoring of sulfur dioxide, nitrogen monoxide and ammonia

A methodology is described for the in-situ detection of NO, NH3 and SO2 in flue gases by DOAS (Differential Optical Absorption Spectroscopy). In order to perform accurate measurements of the concentration it is necessary to compensate for the temperature dependence of the absorption cross-sections as well as for potential deviations from the Beer-Lambert law (nonlinearity effects). From the experimental data in two previous papers, empirical equations were derived for the compensation of the nonlinearity and temperature effects. These were used to compensate obtained concentration values of NO and SO2 retrieved from DOAS spectra that were recorded in a flue gas at 413 K. The measurements of SO2 showed that in a concentration interval of 500–1600 ppm at 413 K, the resulting systematic discrepancies between the DOAS and a conventional reference system decreased from 40 to only 2% when compensating the DOAS data. The maximum random difference was approximately 15%. In the same manner the systematic difference for NO decreased from 23 to 1%, with a maximum random error of 5%, for concentrations between 60 and 160 ppm. The measurements of NH3 demonstrated the versatility of the DOAS technique for time resolved in-situ measurements (<20 sec), and also the feasibility of the technique for measuring several species simultaneously. The measurement methodology developed for NH3 was more complicated than for NO and SO2 and required a larger amount of laboratory calibrations. In the spectral evaluation procedure of NH3 hot bands were utilized for flue gas temperatures above 450 K

Surveillance of Sulfur Fuel Content in Ships at the Great Belt Bridge 2019

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Best practice report on compliance monitoring of ships with respect to current and future IMO regulation

Since 2015, new rules from the International Maritime Organization (IMO) and legislation from EU and the US allows ships to run with maximum fuel sulfur content (FSC) of 0.1 % m/m on northern European and US waters, respectively, or use appropriate abatement technique. In addition, since2020, there is a global cap of 0.5 % for the FSC. From 2021, northern Europe is a NOx emission control area, requiring at least 80 % emission reduction (Tier III) for all ships built from this year and onward, compared to ships built between 2000 and 2010 (Tier I). There is also a discussion withinIMO how to control particle emission of black carbon (BC). This report focuses on best practice in remote compliance monitoring of FSC without stepping on board of the ship. Similar measurements for NOx are also shown, with a discussion whether these can be used for compliance monitoring.Some examples of remote measurements of BC are provided. Remote measurement methods for compliance monitoring of FSC in ships have been developed during the last 10 years within national and European projects (EnviSum and Compmon) and furthermore implemented in nationalmonitoring in Belgium, Denmark, Germany the Netherlands and Sweden. The measurement methods are generally based on sniffer systems measuring the exhaust gas concentrations of SO2, NOx and particulate matter (BC), respectively, against CO2. There are systems with varying sensitivity that areoperated at different distances from the ships (50 m to 2 km) and from different platforms, i.e. fixed, shipborne and airborne (manned and unmanned). There are also optical systems measuring the ratio of SO2 against NO2, as an indicator of the FSC, primarily used from manned aircraft. The focus inthis report is on standard sniffer systems, based on generally available equipment for air quality monitoring. Such systems have been used extensively during the last 5 years for operational compliance monitoring from both fixed and airborne platforms. A summary of FSC measurementresults for multiple operators and platforms shows that the noncompliance level has decreased significantly over the last 5 years at different parts of Europe, i.e. from 5-13 % in 2015 to below 1 % in 2020. The highest noncompliance levels were found at the SECA border in the English channeland in the middle of the Baltic sea. The measurement data, interpreted with ship modelling data from the Finnish Meteorological Institute, indicates that remote compliance monitoring of NOx should work reasonably well for ships operating at high loads (above 40 % load). For slow steaming shipsthe measurements are associated with larger uncertainties and care should be taken in the interpretation of then results here and further ship emission modelling is needed to assess this. The remote measurements of BC work well to identify high emitters and groups of polluting ships. However, the BC emissions have a strong load dependence are intermittent by nature and it is therefore difficult to make short term measurements. See\ua0https://cshipp.e

Quantification of methane emissions from cattle farms, using the tracer gas dispersion method

In Denmark, agriculture is the largest source of anthropogenic methane emissions (81%), mainly from cattle (dairy and beef) farms. Whole-farm methane emissions were quantified at nine Danish cattle farms, using the tracer gas dispersion method. Five to six measurement campaigns were carried out at each farm, covering a full year. Of the nine cattle farms, seven were home to dairy cows and two to beef cattle. The farms represented typical breeds, housing and management systems used in Denmark. Whole-farm methane emission rates ranged from 0.7 to 28 kg h−1, with the highest measurements seen at locations with the highest number of animals. Emissions tended to be higher from August to October, due to elevated temperatures and high amounts of stored manure during this period of the year. The average emission factor (EF) for dairy cow farms was 26 \ub1 8.5 g Livestock Unit (LU)−1 h−1, whereas it was 16 \ub1 4.1 LU−1 h−1 for beef cattle farms, i.e. 38% lower for the latter. The use of deep litter house management explained some of the differences found in the EFs for dairy cows. Methane emission rates estimated using IPCC models and national guidelines tended, on average for all farms and measurements, to be underestimated by 35% in comparison with the measured methane emissions, for all models and farms. The results suggest that future improvements to inventory models should focus on enteric methane emissions from beef cattle and manure methane emissions for both dairy cows and beef cattle, especially from deep litter management

Ship emissions of SO2 and NO2: DOAS measurements from airborne platforms

A unique methodology to measure gas fluxes of SO2 and NO2 from ships using optical remote sensing is described and demonstrated in a feasibility study. The measurement system is based on Differential Optical Absorption Spectroscopy using reflected skylight from the water surface as light source. A grating spectrometer records spectra around 311 nm and 440 nm, respectively, with the telescope pointed downward at a 30A degrees angle from the horizon. The mass column values of SO2 and NO2 are retrieved from each spectrum and integrated across the plume. A simple geometric approximation is used to calculate the optical path. To obtain the total emission in kg h(-1) the resulting total mass across the plume is multiplied with the apparent wind, i.e. a dilution factor corresponding to the vector between the wind and the ship speed. The system was tested in two feasibility studies in the Baltic Sea and Kattegat, from a CASA-212 airplane in 2008 and in the North Sea outside Rotterdam from a Dauphin helicopter in an EU campaign in 2009. In the Baltic Sea the average SO2 emission out of 22 ships was (54 +/- 13) kg h(-1), and the average NO2 emission was (33 +/- 8) kg h(-1), out of 13 ships. In the North Sea the average SO2 emission out of 21 ships was (42 +/- 11) kg h(-1), NO2 was not measured here. The detection limit of the system made it possible to detect SO2 in the ship plumes in 60% of the measurements when the described method was used. A comparison exercise was carried out by conducting airborne optical measurements on a passenger ferry in parallel with onboard measurements. The comparison shows agreement of (-30 +/- 14)% and (-41 +/- 11)%, respectively, for two days, with equal measurement precision of about 20%. This gives an idea of the measurement uncertainty caused by errors in the simple geometric approximation for the optical light path neglecting scattering of the light in ocean waves and direct and multiple scattering in the exhaust plume under various conditions. A tentative error budget indicates uncertainties within 30-45% but for a reliable error analysis the optical light path needs to be modelled. A ship emission model, FMI-STEAM, has been compared to the optical measurements showing an 18% overestimation and a correlation coefficient (R-2) of 0.6. It is shown that a combination of the optical method with modelled power consumption can estimate the sulphur fuel content within 40%, which would be sufficient to detect the difference between ships running at 1% and at 0.1%, limits applicable within the IMO regulated areas

Ammonia and methane emissions from dairy concentrated animal feeding operations in California, using mobile optical remote sensing

Dairy concentrated animal feeding operations (CAFOs) are significant sources of methane (CH4) and ammonia (NH3) emissions in the San Joaquin Valley, California. Optical techniques, namely, remote sensing by Solar Occultation Flux (SOF) and Mobile extractive FTIR (MeFTIR), were used to measure NH3 air column and ground air concentrations of NH3 and CH4, respectively. Campaigns were performed in May and October 2019 and covered 14 dairies located near Bakersfield and Tulare, California. NH3 and CH4 emission rates from single CAFOs averaged 101.9 \ub1 40.6 kgNH3/h and 437.7 \ub1 202.0 kgCH4/h, respectively, corresponding to emission factors (EFs) per livestock unit of 9.1 \ub1 2.7 gNH3/LU/h and 40.1 \ub1 17.8 gCH4/LU/h. The NH3 emissions had a median standard uncertainty of 17% and an expanded uncertainty (95% Confidence Interval (CI)) of 37%; meanwhile, CH4 emissions estimates had greater uncertainty, median of 25% and 53% (in the 95% CI). Decreasing NH3 to CH4 ratios and NH3 EFs from early afternoon (13:00) to early night (19:00) indicated a diurnal emission pattern with lower ammonia emissions during the night. On average, measured NH3 emissions were 28% higher when compared to daytime emission rates reported in the National Emissions Inventory (NEI) and modeled according to diurnal variation. Measured CH4 emissions were 60% higher than the rates reported in the California Air Resources Board (CARB) inventory. However, comparison with airborne measurements showed similar emission rates. This study demonstrates new air measurement methods, which can be used to quantify emissions over large areas with high spatial resolution and in a relatively short time period. These techniques bridge the gap between satellites and individual CAFOs measurements

What explains SECA compliance: rational calculation or moral judgment?

We explain the Sulphur Emission Control Area (SECA) compliance through analyzing both rational and moral factors for compliance motivation. According to preliminary analysis based on samples and measurements, the compliance rate for SECA is rather good and air quality has improved significantly. As costs of compliance are rather high and penalties for non-compliance rather low for regulation targets, moral motivation factors must be relevant for compliance. Maintaining good relationships with control authorities and peers requires shipowners to comply with the rules for practical and moral legitimacy. Our interviews with Danish, Finnish and Estonian shipowners confirmed that most of them follow the law simply because it is the law, this applying both to current Baltic Sea SECA rules and the future global sulphur emission rules. Obeying environmental law thus has a taken-for-granted status among shipping companies. Almost half of the companies specifically mentioned they follow the SECA rules because they want to take care of the environment, thus having internalized the regulatory content. Some companies see global compliance to depend on efficient controls

Measurements of industrial emissions of alkenes in Texas using the solar occultation flux method

Solar occultation flux (SOF) measurements of alkenes have been conducted to identify and quantify the largest emission sources in the vicinity of Houston and in SE Texas during September 2006 as part of the TexAQS 2006 campaign. The measurements have been compared to emission inventories and have been conducted in parallel with airborne plume studies. The SOF measurements show that the hourly gas emissions from the large petrochemical and refining complexes in the Houston Ship Channel area and Mount Belvieu during September 2006 corresponded to 1250 +/- 180 kg/h of ethene and 2140 +/- 520 kg/h of propene, with an estimated uncertainty of about 35%. This can be compared to the 2006 emission inventory value for ethene and propene of 145 +/- 4 and 181 +/- 42 kg/h, respectively. On average, for all measurements during the campaign, the discrepancy factor is 10.2(+ 8,-5) for ethene and 11.7(+ 7,-4) for propene. The largest emission source was Mount Belvieu, NE of the Houston Ship Channel, with ethene and propene emissions corresponding to 440 +/- 130 kg/h and 490 +/- 190 kg/h, respectively. Large variability of propene was observed from several petrochemical industries, for which the largest reported emission sources are flares. The SOF alkene emissions agree within 50% with emissions derived from airborne measurements at three different sites. The airborne measurements also provide support to the SOF error budget