Isotopic signatures of major methane sources in the coal seam gas fields and adjacent agricultural districts, Queensland, Australia

• Main Authors: X. Lu, S. J. Harris, R. E. Fisher, J. L. France, E. G. Nisbet, D. Lowry, T. Röckmann, C. van der Veen, M. Menoud, S. Schwietzke, B. F. J. Kelly
• Format: Article
• Language: English
• Published: Copernicus Publications 2021-07-01
• Series: Atmospheric Chemistry and Physics
• Online Access: https://acp.copernicus.org/articles/21/10527/2021/acp-21-10527-2021.pdf
• ISSN: 1680-7316; 1680-7324

<p>In regions where there are multiple sources of methane (<span class="inline-formula">CH₄</span>) in close proximity, it can be difficult to apportion the <span class="inline-formula">CH₄</span> measured in the atmosphere to the appropriate sources. In the Surat Basin, Queensland, Australia, coal seam gas (CSG) developments are surrounded by cattle feedlots, grazing cattle, piggeries, coal mines, urban centres and natural sources of <span class="inline-formula">CH₄</span>. The characterization of carbon (<span class="inline-formula"><i>δ</i>¹³C</span>) and hydrogen (<span class="inline-formula"><i>δ</i>D</span>) stable isotopic composition of <span class="inline-formula">CH₄</span> can help distinguish between specific emitters of <span class="inline-formula">CH₄</span>. However, in Australia there is a paucity of data on the various isotopic signatures of the different source types. This research examines whether dual isotopic signatures of <span class="inline-formula">CH₄</span> can be used to distinguish between sources of <span class="inline-formula">CH₄</span> in the Surat Basin. We also highlight the benefits of sampling at nighttime. During two campaigns in 2018 and 2019, a mobile <span class="inline-formula">CH₄</span> monitoring system was used to detect <span class="inline-formula">CH₄</span> plumes. Sixteen plumes immediately downwind from known <span class="inline-formula">CH₄</span> sources (or individual facilities) were sampled and analysed for their <span class="inline-formula">CH₄</span> mole fraction and <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M14" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><msup><mi mathvariant="italic">δ</mi><mn mathvariant="normal">13</mn></msup><msub><mi mathvariant="normal">C</mi><mrow class="chem"><msub><mi mathvariant="normal">CH</mi><mn mathvariant="normal">4</mn></msub></mrow></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="41pt" height="18pt" class="svg-formula" dspmath="mathimg" md5hash="1d1eae5b775e61a583e928af9d6abadd"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-10527-2021-ie00001.svg" width="41pt" height="18pt" src="acp-21-10527-2021-ie00001.png"/></svg:svg></span></span> and <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M15" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><mi mathvariant="italic">δ</mi><msub><mi mathvariant="normal">D</mi><mrow class="chem"><msub><mi mathvariant="normal">CH</mi><mn mathvariant="normal">4</mn></msub></mrow></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="32pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="3f034aab678b35cdd6a950ab10b896d9"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-10527-2021-ie00002.svg" width="32pt" height="14pt" src="acp-21-10527-2021-ie00002.png"/></svg:svg></span></span> signatures. The isotopic signatures of the <span class="inline-formula">CH₄</span> sources were determined using the Keeling plot method. These new source signatures were then compared to values documented in reports and peer-reviewed journal articles. In the Surat Basin, CSG sources have <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M17" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><msup><mi mathvariant="italic">δ</mi><mn mathvariant="normal">13</mn></msup><msub><mi mathvariant="normal">C</mi><mrow class="chem"><msub><mi mathvariant="normal">CH</mi><mn mathvariant="normal">4</mn></msub></mrow></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="41pt" height="18pt" class="svg-formula" dspmath="mathimg" md5hash="42da5be3ee1259aed48175631a9ebeef"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-10527-2021-ie00003.svg" width="41pt" height="18pt" src="acp-21-10527-2021-ie00003.png"/></svg:svg></span></span> signatures between <span class="inline-formula">−55.6</span> ‰ and <span class="inline-formula">−50.9</span> ‰ and <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M20" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><mi mathvariant="italic">δ</mi><msub><mi mathvariant="normal">D</mi><mrow class="chem"><msub><mi mathvariant="normal">CH</mi><mn mathvariant="normal">4</mn></msub></mrow></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="32pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="727a1f5b52f1ef3dd605c58191d5f5b2"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-10527-2021-ie00004.svg" width="32pt" height="14pt" src="acp-21-10527-2021-ie00004.png"/></svg:svg></span></span> signatures between <span class="inline-formula">−207.1</span> ‰ and <span class="inline-formula">−193.8</span> ‰. Emissions from an open-cut coal mine have <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M23" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><msup><mi mathvariant="italic">δ</mi><mn mathvariant="normal">13</mn></msup><msub><mi mathvariant="normal">C</mi><mrow class="chem"><msub><mi mathvariant="normal">CH</mi><mn mathvariant="normal">4</mn></msub></mrow></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="41pt" height="18pt" class="svg-formula" dspmath="mathimg" md5hash="76c16cb94847cb6c106716d5ea60319e"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-10527-2021-ie00005.svg" width="41pt" height="18pt" src="acp-21-10527-2021-ie00005.png"/></svg:svg></span></span> and <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M24" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><mi mathvariant="italic">δ</mi><msub><mi mathvariant="normal">D</mi><mrow class="chem"><msub><mi mathvariant="normal">CH</mi><mn mathvariant="normal">4</mn></msub></mrow></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="32pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="73c2e30734959e3febedf5865ec40a0d"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-10527-2021-ie00006.svg" width="32pt" height="14pt" src="acp-21-10527-2021-ie00006.png"/></svg:svg></span></span> signatures of <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M25" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>-</mo><mn mathvariant="normal">60.0</mn><mo>±</mo><mn mathvariant="normal">0.6</mn></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="58pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="5256e0fdf5606884a02e4ba6415ac2a0"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-10527-2021-ie00007.svg" width="58pt" height="10pt" src="acp-21-10527-2021-ie00007.png"/></svg:svg></span></span> ‰ and <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M26" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>-</mo><mn mathvariant="normal">209.7</mn><mo>±</mo><mn mathvariant="normal">1.8</mn></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="64pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="b8ada67f867afdba822f276417963a70"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-10527-2021-ie00008.svg" width="64pt" height="10pt" src="acp-21-10527-2021-ie00008.png"/></svg:svg></span></span> ‰ respectively. Emissions from two ground seeps (abandoned coal exploration wells) have <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M27" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><msup><mi mathvariant="italic">δ</mi><mn mathvariant="normal">13</mn></msup><msub><mi mathvariant="normal">C</mi><mrow class="chem"><msub><mi mathvariant="normal">CH</mi><mn mathvariant="normal">4</mn></msub></mrow></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="41pt" height="18pt" class="svg-formula" dspmath="mathimg" md5hash="68469465d4d1ae44db978e76d22c0822"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-10527-2021-ie00009.svg" width="41pt" height="18pt" src="acp-21-10527-2021-ie00009.png"/></svg:svg></span></span> signatures of <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M28" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>-</mo><mn mathvariant="normal">59.9</mn><mo>±</mo><mn mathvariant="normal">0.3</mn></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="58pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="d6637d9aa9c8a55f966608820bc8a060"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-10527-2021-ie00010.svg" width="58pt" height="10pt" src="acp-21-10527-2021-ie00010.png"/></svg:svg></span></span> ‰ and <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M29" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>-</mo><mn mathvariant="normal">60.5</mn><mo>±</mo><mn mathvariant="normal">0.2</mn></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="58pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="7842699a583d50e46b4ea222a2cbc1a4"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-10527-2021-ie00011.svg" width="58pt" height="10pt" src="acp-21-10527-2021-ie00011.png"/></svg:svg></span></span> ‰ and <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M30" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><mi mathvariant="italic">δ</mi><msub><mi mathvariant="normal">D</mi><mrow class="chem"><msub><mi mathvariant="normal">CH</mi><mn mathvariant="normal">4</mn></msub></mrow></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="32pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="6ff0d405767cebd4635d9d7ba9a0e6ee"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-10527-2021-ie00012.svg" width="32pt" height="14pt" src="acp-21-10527-2021-ie00012.png"/></svg:svg></span></span> signatures of <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M31" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>-</mo><mn mathvariant="normal">185.0</mn><mo>±</mo><mn mathvariant="normal">3.1</mn></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="64pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="bb5674ef8f504c1e657dba6af0645f03"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-10527-2021-ie00013.svg" width="64pt" height="10pt" src="acp-21-10527-2021-ie00013.png"/></svg:svg></span></span> ‰ and <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M32" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>-</mo><mn mathvariant="normal">190.2</mn><mo>±</mo><mn mathvariant="normal">1.4</mn></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="64pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="441cbe40347d9992825c8b00b5badb40"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-10527-2021-ie00014.svg" width="64pt" height="10pt" src="acp-21-10527-2021-ie00014.png"/></svg:svg></span></span> ‰. A river seep had a <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M33" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><msup><mi mathvariant="italic">δ</mi><mn mathvariant="normal">13</mn></msup><msub><mi mathvariant="normal">C</mi><mrow class="chem"><msub><mi mathvariant="normal">CH</mi><mn mathvariant="normal">4</mn></msub></mrow></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="41pt" height="18pt" class="svg-formula" dspmath="mathimg" md5hash="8e0218e2f726350c6d2760d57e52ea6d"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-10527-2021-ie00015.svg" width="41pt" height="18pt" src="acp-21-10527-2021-ie00015.png"/></svg:svg></span></span> signature of <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M34" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>-</mo><mn mathvariant="normal">61.2</mn><mo>±</mo><mn mathvariant="normal">1.4</mn></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="58pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="b035e63aea2afab60c9a73b140034682"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-10527-2021-ie00016.svg" width="58pt" height="10pt" src="acp-21-10527-2021-ie00016.png"/></svg:svg></span></span> ‰ and a <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M35" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><mi mathvariant="italic">δ</mi><msub><mi mathvariant="normal">D</mi><mrow class="chem"><msub><mi mathvariant="normal">CH</mi><mn mathvariant="normal">4</mn></msub></mrow></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="32pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="9013802da64b0ff1449b50e4c7ffff9b"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-10527-2021-ie00017.svg" width="32pt" height="14pt" src="acp-21-10527-2021-ie00017.png"/></svg:svg></span></span> signature of <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M36" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>-</mo><mn mathvariant="normal">225.1</mn><mo>±</mo><mn mathvariant="normal">2.9</mn></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="64pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="06cb91ca4c80a28bf8d6308263b73c07"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-10527-2021-ie00018.svg" width="64pt" height="10pt" src="acp-21-10527-2021-ie00018.png"/></svg:svg></span></span> ‰. Three dominant agricultural sources were analysed. The <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M37" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><msup><mi mathvariant="italic">δ</mi><mn mathvariant="normal">13</mn></msup><msub><mi mathvariant="normal">C</mi><mrow class="chem"><msub><mi mathvariant="normal">CH</mi><mn mathvariant="normal">4</mn></msub></mrow></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="41pt" height="18pt" class="svg-formula" dspmath="mathimg" md5hash="485a1125f4a1ab40c73d663bc3dee66c"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-10527-2021-ie00019.svg" width="41pt" height="18pt" src="acp-21-10527-2021-ie00019.png"/></svg:svg></span></span> and <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M38" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><mi mathvariant="italic">δ</mi><msub><mi mathvariant="normal">D</mi><mrow class="chem"><msub><mi mathvariant="normal">CH</mi><mn mathvariant="normal">4</mn></msub></mrow></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="32pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="c098a2282e13ef9f62373f77e0b06802"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-10527-2021-ie00020.svg" width="32pt" height="14pt" src="acp-21-10527-2021-ie00020.png"/></svg:svg></span></span> signatures of a cattle feedlot are <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M39" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>-</mo><mn mathvariant="normal">62.9</mn><mo>±</mo><mn mathvariant="normal">1.3</mn></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="58pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="4b2916965dea04c6c9d667fcacb78ec2"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-10527-2021-ie00021.svg" width="58pt" height="10pt" src="acp-21-10527-2021-ie00021.png"/></svg:svg></span></span> ‰ and <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M40" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>-</mo><mn mathvariant="normal">310.5</mn><mo>±</mo><mn mathvariant="normal">4.6</mn></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="64pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="12ac13028a289d1fc2825b39758cbc24"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-10527-2021-ie00022.svg" width="64pt" height="10pt" src="acp-21-10527-2021-ie00022.png"/></svg:svg></span></span> ‰ respectively, grazing (pasture) cattle have <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M41" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><msup><mi mathvariant="italic">δ</mi><mn mathvariant="normal">13</mn></msup><msub><mi mathvariant="normal">C</mi><mrow class="chem"><msub><mi mathvariant="normal">CH</mi><mn mathvariant="normal">4</mn></msub></mrow></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="41pt" height="18pt" class="svg-formula" dspmath="mathimg" md5hash="cd0a208e4b4d2899640a4887a537e0d7"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-10527-2021-ie00023.svg" width="41pt" height="18pt" src="acp-21-10527-2021-ie00023.png"/></svg:svg></span></span> and <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M42" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><mi mathvariant="italic">δ</mi><msub><mi mathvariant="normal">D</mi><mrow class="chem"><msub><mi mathvariant="normal">CH</mi><mn mathvariant="normal">4</mn></msub></mrow></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="32pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="5d840c3785e377fcb2be2fdaf9ef06cc"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-10527-2021-ie00024.svg" width="32pt" height="14pt" src="acp-21-10527-2021-ie00024.png"/></svg:svg></span></span> signatures of <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M43" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>-</mo><mn mathvariant="normal">59.7</mn><mo>±</mo><mn mathvariant="normal">1.0</mn></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="58pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="d2d514e4c1f7ecfd9c4dff51bcf582ca"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-10527-2021-ie00025.svg" width="58pt" height="10pt" src="acp-21-10527-2021-ie00025.png"/></svg:svg></span></span> ‰ and <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M44" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>-</mo><mn mathvariant="normal">290.5</mn><mo>±</mo><mn mathvariant="normal">3.1</mn></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="64pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="02ba9a450e2c4d7fad98baf33678dd9a"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-10527-2021-ie00026.svg" width="64pt" height="10pt" src="acp-21-10527-2021-ie00026.png"/></svg:svg></span></span> ‰ respectively, and a piggery sampled had <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M45" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><msup><mi mathvariant="italic">δ</mi><mn mathvariant="normal">13</mn></msup><msub><mi mathvariant="normal">C</mi><mrow class="chem"><msub><mi mathvariant="normal">CH</mi><mn mathvariant="normal">4</mn></msub></mrow></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="41pt" height="18pt" class="svg-formula" dspmath="mathimg" md5hash="28878e980776554e9874acbbd3e88629"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-10527-2021-ie00027.svg" width="41pt" height="18pt" src="acp-21-10527-2021-ie00027.png"/></svg:svg></span></span> and <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M46" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><mi mathvariant="italic">δ</mi><msub><mi mathvariant="normal">D</mi><mrow class="chem"><msub><mi mathvariant="normal">CH</mi><mn mathvariant="normal">4</mn></msub></mrow></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="32pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="92a38a38ea8f2546e4f385db3b2d7fec"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-10527-2021-ie00028.svg" width="32pt" height="14pt" src="acp-21-10527-2021-ie00028.png"/></svg:svg></span></span> signatures of <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M47" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>-</mo><mn mathvariant="normal">47.6</mn><mo>±</mo><mn mathvariant="normal">0.2</mn></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="58pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="9b1fb17755b66540a81e53684cec696d"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-10527-2021-ie00029.svg" width="58pt" height="10pt" src="acp-21-10527-2021-ie00029.png"/></svg:svg></span></span> ‰ and <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M48" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>-</mo><mn mathvariant="normal">300.1</mn><mo>±</mo><mn mathvariant="normal">2.6</mn></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="64pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="826504dfa3f99fad6751c15f1b3b54b3"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-10527-2021-ie00030.svg" width="64pt" height="10pt" src="acp-21-10527-2021-ie00030.png"/></svg:svg></span></span> ‰ respectively, which reflects emissions from animal waste. An export abattoir (meat works and processing) had <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M49" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><msup><mi mathvariant="italic">δ</mi><mn mathvariant="normal">13</mn></msup><msub><mi mathvariant="normal">C</mi><mrow class="chem"><msub><mi mathvariant="normal">CH</mi><mn mathvariant="normal">4</mn></msub></mrow></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="41pt" height="18pt" class="svg-formula" dspmath="mathimg" md5hash="b36361797659dd2fd97c29a78371eb5f"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-10527-2021-ie00031.svg" width="41pt" height="18pt" src="acp-21-10527-2021-ie00031.png"/></svg:svg></span></span> and <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M50" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><mi mathvariant="italic">δ</mi><msub><mi mathvariant="normal">D</mi><mrow class="chem"><msub><mi mathvariant="normal">CH</mi><mn mathvariant="normal">4</mn></msub></mrow></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="32pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="5e453361ca84b8850a253d762c935201"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-10527-2021-ie00032.svg" width="32pt" height="14pt" src="acp-21-10527-2021-ie00032.png"/></svg:svg></span></span> signatures of <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M51" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>-</mo><mn mathvariant="normal">44.5</mn><mo>±</mo><mn mathvariant="normal">0.2</mn></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="58pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="0727759c171cc0aa84a294bbcd5e22a4"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-10527-2021-ie00033.svg" width="58pt" height="10pt" src="acp-21-10527-2021-ie00033.png"/></svg:svg></span></span> ‰ and <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M52" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>-</mo><mn mathvariant="normal">314.6</mn><mo>±</mo><mn mathvariant="normal">1.8</mn></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="64pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="1da53e6bd0d2affba58abd2a7bf12b80"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-10527-2021-ie00034.svg" width="64pt" height="10pt" src="acp-21-10527-2021-ie00034.png"/></svg:svg></span></span> ‰ respectively. A plume from a wastewater treatment plant had <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M53" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><msup><mi mathvariant="italic">δ</mi><mn mathvariant="normal">13</mn></msup><msub><mi mathvariant="normal">C</mi><mrow class="chem"><msub><mi mathvariant="normal">CH</mi><mn mathvariant="normal">4</mn></msub></mrow></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="41pt" height="18pt" class="svg-formula" dspmath="mathimg" md5hash="1a93b7e1851f6b4850ed595a6fc58e85"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-10527-2021-ie00035.svg" width="41pt" height="18pt" src="acp-21-10527-2021-ie00035.png"/></svg:svg></span></span> and <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M54" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><mi mathvariant="italic">δ</mi><msub><mi mathvariant="normal">D</mi><mrow class="chem"><msub><mi mathvariant="normal">CH</mi><mn mathvariant="normal">4</mn></msub></mrow></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="32pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="fba2c118711602e40ee558e2b390904f"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-10527-2021-ie00036.svg" width="32pt" height="14pt" src="acp-21-10527-2021-ie00036.png"/></svg:svg></span></span> signatures of <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M55" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>-</mo><mn mathvariant="normal">47.6</mn><mo>±</mo><mn mathvariant="normal">0.2</mn></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="58pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="9091337436331f59bd1399ee4bfb79f4"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-10527-2021-ie00037.svg" width="58pt" height="10pt" src="acp-21-10527-2021-ie00037.png"/></svg:svg></span></span> ‰ and <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M56" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>-</mo><mn mathvariant="normal">177.3</mn><mo>±</mo><mn mathvariant="normal">2.3</mn></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="64pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="15c780d2354b97e2dbba7bf1c30c8bdf"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-10527-2021-ie00038.svg" width="64pt" height="10pt" src="acp-21-10527-2021-ie00038.png"/></svg:svg></span></span> ‰ respectively. In the Surat Basin, source attribution is possible when both <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M57" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><msup><mi mathvariant="italic">δ</mi><mn mathvariant="normal">13</mn></msup><msub><mi mathvariant="normal">C</mi><mrow class="chem"><msub><mi mathvariant="normal">CH</mi><mn mathvariant="normal">4</mn></msub></mrow></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="41pt" height="18pt" class="svg-formula" dspmath="mathimg" md5hash="0b801a4e022e2f63902ed093fb5e7108"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-10527-2021-ie00039.svg" width="41pt" height="18pt" src="acp-21-10527-2021-ie00039.png"/></svg:svg></span></span> and <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M58" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><mi mathvariant="italic">δ</mi><msub><mi mathvariant="normal">D</mi><mrow class="chem"><msub><mi mathvariant="normal">CH</mi><mn mathvariant="normal">4</mn></msub></mrow></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="32pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="1d59873d57ae30abbf08185a7776b95d"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-10527-2021-ie00040.svg" width="32pt" height="14pt" src="acp-21-10527-2021-ie00040.png"/></svg:svg></span></span> are measured for the key categories of CSG, cattle, waste from feedlots and piggeries, and water treatment plants. Under most field situations using <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M59" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><msup><mi mathvariant="italic">δ</mi><mn mathvariant="normal">13</mn></msup><msub><mi mathvariant="normal">C</mi><mrow class="chem"><msub><mi mathvariant="normal">CH</mi><mn mathvariant="normal">4</mn></msub></mrow></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="41pt" height="18pt" class="svg-formula" dspmath="mathimg" md5hash="16e70d572b6d6d02c9524107e9a51120"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-10527-2021-ie00041.svg" width="41pt" height="18pt" src="acp-21-10527-2021-ie00041.png"/></svg:svg></span></span> alone will not enable clear source attribution. It is common in the Surat Basin for CSG and feedlot facilities to be co-located. Measurement of both <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M60" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><msup><mi mathvariant="italic">δ</mi><mn mathvariant="normal">13</mn></msup><msub><mi mathvariant="normal">C</mi><mrow class="chem"><msub><mi mathvariant="normal">CH</mi><mn mathvariant="normal">4</mn></msub></mrow></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="41pt" height="18pt" class="svg-formula" dspmath="mathimg" md5hash="652b3aca945950480191fbb5cf261d69"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-10527-2021-ie00042.svg" width="41pt" height="18pt" src="acp-21-10527-2021-ie00042.png"/></svg:svg></span></span> and <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M61" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><mi mathvariant="italic">δ</mi><msub><mi mathvariant="normal">D</mi><mrow class="chem"><msub><mi mathvariant="normal">CH</mi><mn mathvariant="normal">4</mn></msub></mrow></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="32pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="b7918119e8a00d96169bddb28e2dc23e"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-10527-2021-ie00043.svg" width="32pt" height="14pt" src="acp-21-10527-2021-ie00043.png"/></svg:svg></span></span> will assist in source apportionment where the plumes from two such sources are mixed.</p>