Chilean regulations on metal-polluted soils: The need to advance from adapting foreign laws towards developing sovereign legislation.

Chile as a major international Cu producer faces serious soil contamination issues in mining areas. Currently Chile does not have any specific law governing the maximum permissible concentrations of metals in soils to protect ecosystems and human health. Chile heavily relies on the use of environmental laws of 14 foreign countries; the choice of the country depends on the similarity of its environmental conditions with those in Chile. In this study, we used an online database to compare the similarity of Chilean rocks to those in foreign countries. Likewise, we performed soil sampling and determined the background concentrations of Cu, As, Pb, and Zn in soils of the Aconcagua basin, the largest river basin in the Valparaiso Region of central Chile. The results showed that geochemical patterns in Chile have the greatest resemblance to New Zealand, Mexico, and Italy. The background Cu concentration in the Aconcagua basin (134 mg kg-1) exceeded the legislated limits of New Zealand (100 mg kg-1) and Italy (120 mg kg-1), whereas the background Zn concentration (200 mg kg-1) exceeded the legislated limit of Italy (150 mg kg-1). Due to the elevated natural abundance of Cu and Zn in Chile, international laws should not be applied in Chile for the assessment of soil contamination. In addition, we assessed ecological risk using the results of our previous studies obtained by analyzing native field-contaminated soils of the Valparaiso region. In the Aconcagua basin, Cu posed high risk for plants in 11% of the samples, whereas As posed high risk for earthworms in 48% of the samples. We suggest that future studies are required to search for other organisms that can serve as biomarkers of metal toxicity because our previous studies were limited to plants and earthworms. Importantly, As posed high risk to human health in 25% of the samples in our study. There is a need for future studies to demonstrate empirically an association between soil As and children's blood As in order to establish the national threshold values of soil As to protect human health. We conclude that there is an urgent need in Chile to advance from the current approach of adapting foreign laws to developing Chilean sovereign environmental legislation.

Publisher Correction: Geochemical constraints on the Hadean environment from mineral fingerprints of prokaryotes.

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Geochemical constraints on the Hadean environment from mineral fingerprints of prokaryotes.

The environmental conditions on the Earth before 4 billion years ago are highly uncertain, largely because of the lack of a substantial rock record from this period. During this time interval, known as the Hadean, the young planet transformed from an uninhabited world to the one capable of supporting, and inhabited by the first living cells. These cells formed in a fluid environment they could not at first control, with homeostatic mechanisms developing only later. It is therefore possible that present-day organisms retain some record of the primordial fluid in which the first cells formed. Here we present new data on the elemental compositions and mineral fingerprints of both Bacteria and Archaea, using these data to constrain the environment in which life formed. The cradle solution that produced this elemental signature was saturated in barite, sphene, chalcedony, apatite, and clay minerals. The presence of these minerals, as well as other chemical features, suggests that the cradle environment of life may have been a weathering fluid interacting with dry-land silicate rocks. The specific mineral assemblage provides evidence for a moderate Hadean climate with dry and wet seasons and a lower atmospheric abundance of CO2 than is present today.

From cytoplasm to environment: the inorganic ingredients for the origin of life.

Early in its history, Earth's surface developed from an uninhabitable magma ocean to a place where life could emerge. The first organisms, lacking ion transporters, fixed the composition of their cradle environment in their intracellular fluid. Later, though life adapted and spread, it preserved some qualities of its initial environment within. Modern prokaryotes could thus provide insights into the conditions of early Earth and the requirements for the emergence of life. In this work, we constrain Earth's life-forming environment through detailed analysis of prokaryotic intracellular fluid. Rigorous assessment of the constraints placed on the early Earth environment by intracellular liquid will provide insight into the conditions of abiogenesis, with implications not only for our understanding of early Earth but also the formation of life elsewhere in the Universe.