World War II Opium Wars recorded in oceans corals

first_img Email A team of researchers led by Ruoyu Sun, a geochemist now at Trent University, Peterborough, in Canada, wanted to see whether corals could be a good record of mercury pollution, too. So they extracted a 200-year-old core from a Porites lutea coral in the South China Sea, expecting the record to match those gathered from remote ice and peat samples: a gradual increase over time due to mining, coal combustion, and later industrial production. On 7 January 1841, the U.K. iron steamer Nemesis exploded a Chinese ship with a rocket in a battle during the First Opium War—a conflict between China and the United Kingdom over trade. That shot, along with other explosions and gunfire, would have spewed the toxic metal mercury into the air. Now, a new study suggests that corals in the South China Sea may have taken up the metal, keeping a record of this and future wars locked in their skeletons. The finding provides a look at how humans have been polluting the ocean throughout history, and may help us understand how the metal travels in our atmosphere today.The skeletons of hard corals are made of aragonite, a calcium carbonate mineral. As the organism grows, it pulls additional calcium out of the water to build its skeleton. Corals’ annual growth bands, like the rings of a tree, can be used to track the history of the organism. But because certain metal pollutants—like lead and mercury—can take the place of calcium in the coral’s skeletal structure, the rings can also be an archive of the metals floating in the seawater. Click to view the privacy policy. Required fields are indicated by an asterisk (*) Sign up for our daily newsletter Get more great content like this delivered right to you! Country Country * Afghanistan Aland Islands Albania Algeria Andorra Angola Anguilla Antarctica Antigua and Barbuda Argentina Armenia Aruba Australia Austria Azerbaijan Bahamas Bahrain Bangladesh Barbados Belarus Belgium Belize Benin Bermuda Bhutan Bolivia, Plurinational State of Bonaire, Sint Eustatius and Saba Bosnia and Herzegovina Botswana Bouvet Island Brazil British Indian Ocean Territory Brunei Darussalam Bulgaria Burkina Faso Burundi Cambodia Cameroon Canada Cape Verde Cayman Islands Central African Republic Chad Chile China Christmas Island Cocos (Keeling) Islands Colombia Comoros Congo Congo, the Democratic Republic of the Cook Islands Costa Rica Cote d’Ivoire Croatia Cuba Curaçao Cyprus Czech Republic Denmark Djibouti Dominica Dominican Republic Ecuador Egypt El Salvador Equatorial Guinea Eritrea Estonia Ethiopia Falkland Islands (Malvinas) Faroe Islands Fiji Finland France French Guiana French Polynesia French Southern Territories Gabon Gambia Georgia Germany Ghana Gibraltar Greece Greenland Grenada Guadeloupe Guatemala Guernsey Guinea Guinea-Bissau Guyana Haiti Heard Island and McDonald Islands Holy See (Vatican City State) Honduras Hungary Iceland India Indonesia Iran, Islamic Republic of Iraq Ireland Isle of Man Israel Italy Jamaica Japan Jersey Jordan Kazakhstan Kenya Kiribati Korea, Democratic People’s Republic of Korea, Republic of Kuwait Kyrgyzstan Lao People’s Democratic Republic Latvia Lebanon Lesotho Liberia Libyan Arab Jamahiriya Liechtenstein Lithuania Luxembourg Macao Macedonia, the former Yugoslav Republic of Madagascar Malawi Malaysia Maldives Mali Malta Martinique Mauritania Mauritius Mayotte Mexico Moldova, Republic of Monaco Mongolia Montenegro Montserrat Morocco Mozambique Myanmar Namibia Nauru Nepal Netherlands New Caledonia New Zealand Nicaragua Niger Nigeria Niue Norfolk Island Norway Oman Pakistan Palestine Panama Papua New Guinea Paraguay Peru Philippines Pitcairn Poland Portugal Qatar Reunion Romania Russian Federation Rwanda Saint Barthélemy Saint Helena, Ascension and Tristan da Cunha Saint Kitts and Nevis Saint Lucia Saint Martin (French part) Saint Pierre and Miquelon Saint Vincent and the Grenadines Samoa San Marino Sao Tome and Principe Saudi Arabia Senegal Serbia Seychelles Sierra Leone Singapore Sint Maarten (Dutch part) Slovakia Slovenia Solomon Islands Somalia South Africa South Georgia and the South Sandwich Islands South Sudan Spain Sri Lanka Sudan Suriname Svalbard and Jan Mayen Swaziland Sweden Switzerland Syrian Arab Republic Taiwan Tajikistan Tanzania, United Republic of Thailand Timor-Leste Togo Tokelau Tonga Trinidad and Tobago Tunisia Turkey Turkmenistan Turks and Caicos Islands Tuvalu Uganda Ukraine United Arab Emirates United Kingdom United States Uruguay Uzbekistan Vanuatu Venezuela, Bolivarian Republic of Vietnam Virgin Islands, British Wallis and Futuna Western Sahara Yemen Zambia Zimbabwe Philippe Bourjon A Porites lutea coral. But the record they found was very different. In the oldest part of the core, dating to between 1800 and 1830, levels of mercury were low and relatively constant. But over the coral’s next 170 years of life, the amount of mercury incorporated into its skeleton spiked repeatedly, sometimes reaching concentrations four to 12 times higher than the baseline. Those spikes line up precisely with a number of violent conflicts that raged in nearby China, including the First Opium War (1839–1842), the Second Opium War (1856–1860), and World War II, according to a study published this month in Environmental Science & Technology. The baseline mercury level also rose throughout the 1900s—but that increase is dwarfed by the wartime spikes.“We never expected [mercury] would come from the wars,” Sun says—but there’s a good reason why it would. The metal is used in the production of weapons and explosives, and their detonation could also release mercury into the air. When the elemental form of mercury in the atmosphere encounters reactive chemicals like bromine ejected from the ocean via sea spray, it forms what researchers call “reactive gaseous mercury” molecules. These then settle into the ocean, after which corals can take up the dissolved mercury into their skeletons.For Hannah Horowitz, an atmospheric chemist at Harvard University who wasn’t involved in the study, this local effect of wars fits into the new picture that’s emerging of how mercury behaves in the atmosphere. Once considered a more long-lived chemical that travels vast distances as it drifts through the atmosphere for a year or more, the impacts of mercury are increasingly being thought of as more local. “We’re revising that down to the order of months,” Horowitz says. That would explain why the signal of mining and manufacturing in the West might not make its way to the South China Sea.Others are more skeptical of the results. Seeing a signal of wars in coral, according to Carl Lamborg, a geochemist at the University of California, Santa Cruz, is “maybe not impossible, but would require enormous inputs of mercury over time.” One large source of uncertainty is that corals may not take up mercury at a constant rate, meaning that a record of mercury from coral skeletons wouldn’t faithfully track the amount of mercury in seawater. Research on how mercury is taken up by corals is still in the early stages, Lamborg stresses. But, he says, “their interpretation is as reasonable as any other.”And, certainly, this isn’t the last step for Sun and his colleagues. To firm up the connection between coral mercury and wars, Sun next plans to look for specific mercury isotopes in the coral archive. Different sources of mercury in the atmosphere—including volcanoes, coal combustion, and explosives—contain different amounts of the element’s isotopes, Sun says. Liquid mercury derived from the mineral cinnabar—which, among other things, was used as an additive in many explosives in the 19th century—might have its own such fingerprint, he adds. “If that’s the same as the one in the corals then we’ll be sure.”last_img