Synchrotron light advances knowledge of Brazilian soil

Chemical, physical and biological processes occurring in different soil regions are studied at the atomic scale.

By Diego Freire

Agência FAPESP – Investigation of the chemical, physical and biological processes that largely control nutrient availability, pollutant transportation and environmental contamination, among other things, is facilitated by the use of synchrotron light, a form of electromagnetic radiation produced by particle accelerators.

This and other applications of synchrotron radiation in several scientific fields were presented during the São Paulo School of Advanced Science on Recent Developments in Synchrotron Radiation (SyncLight 2015), held at the National Energy & Materials Research Center (CNPEM) in Campinas, São Paulo State, Brazil, on July 13-24.

FAPESP supported SyncLight 2015 through its São Paulo School of Advanced Science (SPSAS) program. The event was attended by researchers and students from 17 countries.

According to Hélio Cesar Nogueira Tolentino, a researcher at the National Synchrotron Light Laboratory (LNLS) and coordinator of SyncLight 2015, the aim was to offer a comprehensive overview of the applications of synchrotron radiation for the advancement of science.

“Synchrotron light has important applications in physics, chemistry, biology, geoscience, medicine, engineering and materials science, among others,” Tolentino told Agência FAPESP. “The aim of SyncLight was to motivate and help prepare the new generation of users of this important scientific tool to exploit all the potential it offers by presenting advanced techniques associated with synchrotron radiation and discussing its applications.”

In the case of geoscience, synchrotron light has contributed to deeper knowledge of soil by improving understanding of various processes that occur at the microscopic scale, explained Dalton Belchior Abdala, a researcher at LNLS in the area of soil science.

“The development of Brazilian agriculture will ultimately reflect the technological advances obtained by the use of these techniques,” Abdala said. “The frontiers of knowledge in geoscience over the coming decades will be defined by a better understanding of the chemical, physical and biological processes that take place in soils at their most fundamental level, i.e., the atomic level, and synchrotron radiation will play a key role in that understanding.”

At SyncLight 2015, Abdala delivered a presentation on X-ray absorption spectroscopy techniques applied to research in geoscience, especially to determine the presence of metals in soil and investigate the reactivity of these elements in the environment.

“Research in this area sets out to understand the reactions that occur at the interfaces among different components of the soil, which is a heterogeneous mixture of organic and inorganic compounds with different compositions,” he said. “Synchrotron light facilitates this understanding by enabling researchers to observe reactions that take place at the atomic and molecular scales.”

The characteristics of synchrotron radiation make it ideal for studying biogeochemical processes and simulating the conditions in which they occur in nature. The use of these techniques typically requires a minimum of test specimen preparation to permit the observation of elements found naturally at very low concentrations in soil, as a basis for designing protocols to improve the agronomic efficiency of materials used in agriculture, such as fertilizer and agrochemicals.

The development of new fertilizers has been one of the lines of research that have used the LNLS facility most intensely. These studies have focused on phosphorus for the production of phosphate-based fertilizers because this element, which is one of the macronutrients essential to the life cycles of all plants, is a globally scarce resource.

The LNLS’s existing synchrotron light source, UVX, the only particle accelerator in operation in Latin America, has also been used by researchers affiliated with the Federal University of Viçosa (UFV) to study phosphate in penguin colonies in Antarctica.

They are interested mainly in monitoring ecological successions on the continent as a result of global warming. Phosphate can be used as an indicator of these successions.

They characterized the chemical and mineral compositions of Antarctic soils by using three experimental techniques available in three light lines at LNLS: diffraction, fluorescence, and soft X-ray absorption spectroscopy.

“X-ray absorption, one of the most productive techniques in geoscience, can be used to determine the chemical form of an element in a very direct manner, as it affords access to the local environment of a given atom,” Abdala explained.

Studies such as these show whether phosphorus is associated with the soil matrix by a bidentate or monodentate ligand in given environmental conditions.

“If you determine that phosphorus is found predominantly in monodentate form, then you can conclude that it’s less closely associated with the soil matrix and is more easily absorbed by plants but also more easily lost in the environment,” Abdala said. “If the bidentate form predominates, it’s more strongly associated with the soil matrix. So it’s unlikely to reach equilibrium with the soil solution and participate directly in plant nutrition or contaminate the environment. Techniques based on synchrotron radiation can be used to investigate the reactivity of these elements depending on the chemical species and the local environment of a given element in given environmental conditions.”

Sirius

Sirius, Brazil’s new synchrotron light source now under construction at CNPEM, will offer even more opportunities for soil research, owing to its combination of X-ray absorption, fluorescence and diffraction in the same experimental chamber, as well as its unprecedented precision, said Ryan Tappero from the National Synchrotron Light Source (NSLS) at Brookhaven National Laboratory (BNL) in Upton, New York, USA.

“Cutting-edge research has been done at NSLS, but our particle accelerator is no longer state of the art in synchrotron radiation,” Tappero explained. “As a fourth-generation synchrotron light source, Sirius will raise research in several fields to a new level by extending the radiation spectrum to higher-energy X rays with exponentially higher brightness.”

According to Abdala, Sirius’s spatial resolution will increase the scope for studies of the rhizosphere, the narrow region of soil at the interface with plant roots. “The rhizosphere is very important because the soil-root interface is where plants absorb nutrients and release root exudates, among other processes,” he said.

“Sirius’s spatial resolution and powerful data acquisition system will facilitate studies of how microbes affect the cycling of nutrients in the soil. A better understanding of the dynamics of the processes that occur in the rhizosphere will explain a lot about the mechanisms used by plants to take up soil nutrients such as potassium, calcium and zinc.”

Sirius will also enable scientists to make advances in research on food biofortification, which involves the enrichment of foods with more highly bioavailable forms of several nutrients, according to Abdala.

“For example, dry beans are known to be rich in iron, but this iron is largely associated with phytate, which reduces not just the iron’s bioavailability but also that of zinc and other metals present in beans,” he said. “Sirius will enable us to achieve higher levels of precision in determining the location and chemical species of these elements in regions of a fruit, for example, as well as indicating the parts of greatest interest from the nutritional standpoint.”

Sirius is scheduled to go live in 2018. Its brightness will be the highest of all synchrotron light sources in its energy class in operation or under construction worldwide. Its infrastructure will be open for use by all researchers, whatever their origin.

SPSAS

FAPESP has launched a website for the São Paulo School of Advanced Science (SPSAS) program, offering resources for the organization of short courses on advanced research in a wide array of knowledge areas.

Available in both English and Portuguese, the website provides information on forthcoming events and on those already held, which amount to over 40 and have been attended by thousands of researchers and students from many countries, including the Nobel Laureates Ada Yonath (Israel), Ei-ichi Negishi (Japan), Alvin Roth and John Nash (USA), and Kurt Wüthrich (Switzerland).

Each school has a page of its own with an abstract, a final program, a gallery of photographs showing the activities and people involved, and other information. Several pages include links to stories about schools published by Agência FAPESP.

Each SPSAS receives some 100 students, about half of whom come to Brazil from abroad. Students from other cities, states and countries go through a selection process and are offered such benefits as plane tickets, transfer from the airport to a hotel, and per diems to cover expenses in the city where the school takes place.

Applications must be submitted for analysis in response to Calls for Proposals announced by FAPESP and published on the program’s website. Eleven calls have been issued since the program’s inception in 2009.

The address of the SPSAS website is http://espca.fapesp.br/home.