{"id":218303,"date":"2016-05-27T15:10:31","date_gmt":"2016-05-27T18:10:31","guid":{"rendered":"http:\/\/revistapesquisa.fapesp.br\/en\/?p=218303"},"modified":"2016-05-30T10:34:01","modified_gmt":"2016-05-30T13:34:01","slug":"damage-hidden-in-the-mud","status":"publish","type":"post","link":"https:\/\/revistapesquisa.fapesp.br\/en\/damage-hidden-in-the-mud\/","title":{"rendered":"Damage hidden in the mud"},"content":{"rendered":"

\"RioVal\u00e9ria Quaresma\/UFES <\/span>When Val\u00e9ria Quaresma and Alex Bastos, a couple who are experts in geological oceanography, began studying the sediments of coastal Esp\u00edrito Santo State near the mouth of the Rio Doce about five years ago, one of their objectives was to develop a baseline for future plans to manage that region, where two of the principal sources of economic support: fishing, and petroleum extraction are in opposition.\u00a0 The former depends on the health of a coastal ecosystem that can be threatened by accidents that might be caused by the latter.\u00a0 The duo of professors from the Federal University of Esp\u00edrito Santo (UFES) could not have imagined that their knowledge would be called upon so soon.\u00a0 In early November 2015, when dams operated by Samarco, a mining company in Minas Gerais, collapsed, the professors were part of a group of 100 researchers organized by the university.\u00a0 They immediately prepared to collect comparative samples.\u00a0 \u201cOn November 21, when the plume that descended the Rio Doce reached the mouth of the river, our boat was equipped and ready,\u201d says Quaresma.\u00a0 The next day her team collected samples of seawater that was tinged orange.<\/p>\n

The first account of how the sediments that the river normally carries are behaving is described in an article by Quaresma\u2019s group published in December 2015 in the Brazilian Journal of Geology.\u00a0 <\/i><\/em>The results show that the finest-grain sediments are being deposited very quickly in a process known as flocculation, when fresh water meets the salinity and different pH of the sea.\u00a0 Deposition of that sediment, classified as terrigenous mud, occurs principally at depths of at least 10 meters situated to the south of where the Rio Doce discharges, pushed there by a northeast wind\u2014the prevailing wind in that area.\u00a0 \u201cThen the material can be re-suspended and redistributed northward, depending on the force and direction of the winds and waves,\u201d she explains.\u00a0 Quaresma has mapped the deposition of those sediments, not only in her work that resulted from the samples collected by her group, but also in data compiled in the survey article published in November 2015 in the Journal of South American Earth Sciences.\u00a0 <\/i><\/em>Along the coast of the region north of the Rio Doce, larger and less clayey particles predominate.<\/p>\n

Although researchers know the region well and plenty of preparations were made to receive the wave of mud that has traveled through part of both Minas Gerais and Esp\u00edrito Santo states, causing tremendous damage to adjacent cities and the ecology of the river and its surroundings, there has been no immediate assessment of the impact of the debris from the tailings dam.\u00a0 What was clear from the outset was that this is a terrifying volume of clayey material made of very fine particles that do not readily deposit themselves.\u00a0 \u201cWe are not familiar with the sediment that is in the tailings,\u201d says Quaresma.\u00a0 \u201cWe don\u2019t know how it behaves.\u201d\u00a0 She plans to follow the course of the mud in a series of future field trips.\u00a0 \u201cIt will take a couple of months before we can see what has happened to the bottom.\u201d<\/p>\n

The concern generated by the change in the dynamics of sediment transport goes far beyond its essential role in maintaining coastline stability.\u00a0 Looking at the samples already collected, researchers are shocked at how muddy the water is.\u00a0 It makes it hard for them to see their submerged equipment.\u00a0 Quaresma says that this change in the physical characteristics of the water may completely alter the environment that is necessary to the survival of bottom-dwelling organisms that compose the basis of the marine feed chain: the benthic community.<\/p>\n

\"The

Marcos Daniel Leite\/UFES<\/span>The fine clay suspension tinged the water at the mouth of the Rio Doce so strongly orange that the collector bottle is almost invisible when submergedMarcos Daniel Leite\/UFES<\/span><\/p><\/div>\n

Chemistry<\/strong>
\nIn addition to the sediments, researchers are also worried about the chemical content of the mud.\u00a0 It is no surprise that iron is abundant, because it was the extraction of iron ore that led to the accident. \u00a0Quaresma says this can pose a problem because an excess of iron can cause an excessive proliferation of plankton (microscopic beings that float in the column of water) and bring about a significant ecological imbalance.<\/p>\n

Chemist Renato Rodrigues Neto, coordinator of the Environmental Geochemistry Laboratory in the Department of Oceanography and Ecology at UFES, heads the group that has been analyzing the elements present in the torrent of debris.\u00a0 So far, although samples have been examined from only five points at the mouth of the Rio Doce, an important increase in certain metals has already been observed when compared with the situation that prevailed prior to arrival of the mud.\u00a0 \u201cThe presence of vanadium, aluminum, iron, manganese, and chrome has greatly increased,\u201d the researcher says.\u00a0 He finished his preliminary report with those results at the end of December 2015.\u00a0 Although horrified by the 50-fold increase in the concentration of iron that his group detected, he says iron is not the element that worries him because it is a naturally-occurring nutrient.<\/p>\n

Of greater concern is the greatly increased presence of chrome, an element that can be toxic, depending on how it appears.\u00a0 \u201cUsually it occurs in its less toxic form,\u201d explains Rodrigues Neto, \u201cbut we have not yet done tests to find out what is there right now.\u201d\u00a0 Such tests are very complicated analyses that will require a partnership with other laboratories.\u00a0 Also to be done, according to the chemist, is to determine whether the chrome is in a bioavailable form that could be absorbed by organisms.<\/p>\n

The seriousness of the accident has led to demands for immediate responses and a rapid organization of researchers assigned to produce them.\u00a0 Even so, understanding how the environment and the organisms that live in it are going to react and be affected takes time.\u00a0 Identification of the effects on animals and plants of the region should begin in the coming months.<\/p>\n

Scientific articles<\/em>
\nBASTOS, A. C. et al<\/em>. Shelf morphology as an indicator of sedimentary regimes: a synthesis from a mixed siliciclastic-carbonate shelf on the eastern Brazilian margin<\/a>.\u00a0 Journal of South American Earth Sciences<\/b><\/strong>.\u00a0 V.\u00a063, pp. 125-36.\u00a0 November 2015.
\nQUARESMA, V. S. et al<\/em>. Modern sedimentary processes along the Doce River adjacent continental shelf<\/a>.\u00a0 Brazilian Journal of Geology<\/b><\/strong>.\u00a0 V.\u00a045, No.\u00a04, pp. 635-44.\u00a0 December 2015.<\/p>\n","protected":false},"excerpt":{"rendered":"Dam collapse in Minas Gerais can change the ecological dynamics of the Rio Doce","protected":false},"author":3,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"_exactmetrics_skip_tracking":false,"_exactmetrics_sitenote_active":false,"_exactmetrics_sitenote_note":"","_exactmetrics_sitenote_category":0,"footnotes":""},"categories":[159],"tags":[259,200,240,252],"coauthors":[1601],"class_list":["post-218303","post","type-post","status-publish","format-standard","hentry","category-science","tag-chemistry","tag-environment","tag-geology","tag-oceanography"],"acf":[],"_links":{"self":[{"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/posts\/218303","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/users\/3"}],"replies":[{"embeddable":true,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/comments?post=218303"}],"version-history":[{"count":0,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/posts\/218303\/revisions"}],"wp:attachment":[{"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/media?parent=218303"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/categories?post=218303"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/tags?post=218303"},{"taxonomy":"author","embeddable":true,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/coauthors?post=218303"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}