Avaliação da liberação de elementos traço em solos tratados com xisto retortado

Abstract

EVALUATION OF TRACE ELEMENTS RELEASING FROM SOILS TREATED WITH RETORTED OIL SHALE. Soils that had received successive applications of retorted oil shale (ROS) in an experiment under field conditions were used in this study, aiming to evaluate the availability of trace elements. In the batch tests, we observed that toxic elements present in the ROS are not desorbed from the matrix in significant amounts to contaminate soil and groundwater. The element Ca represents the greatest nutrient contribution, which has high mobility and ease release into the soil solution. Concerning the results obtained from the soil extracts analysis; we observed that the undesirable elements released into the extracts are not directly related to the presence of ROS in the soil samples. Comparing the behavior of soil samples with and without ROS it is possible to infer that many of the trace elements are derived from soil constituents, from previous fertilizer and pesticides applications. The study suggested that the ROS can be used as a soil conditioner for agricultural purposes without adding harmful elements to the environment.Keywords: soils; trace elements; retorted oil shale. INTRODUÇÃOO folhelho pirobetuminoso (xisto) é uma rocha sedimentar rica em querogênio, que é um composto orgânico de composição indefinida, gerado pela ação química e de microrganismos sobre a matéria orgânica ao longo de milhões de anos. 1 O Brasil possui a segunda maior reserva de xisto no mundo, sendo os Estados Unidos detentor das maiores reservas mundiais, 1,2 além de outros países que merecem destaque como Austrália, Canadá, China, Estônia, Itália, Jordânia, Marrocos, Rússia e Zaire. 3 Em São Mateus do Sul, no estado do Paraná, é explorada a extração de xisto da mais importante reserva de xisto do Brasil, a Formação Irati, a qual abrange também os estados de Mato Grosso do Sul, Goiás, São Paulo, Santa Catarina e Rio Grande do Sul. 3 A Unidade de Negócios da Industrialização do Xisto realiza a mineração e o processamento do xisto extraído neste local. O processamento do xisto produz óleo e gás em condições de alta temperatura e alta pressão, além de outros subprodutos, sendo um deles o xisto retortado (XR) produzido em grandes quantidades, representando cerca de 80 a 90% da quantidade de matéria prima inicial do processo. 1 O XR é uma matriz dependente de sua origem e do processo de extração de óleo e gás, e pode conter compostos orgânicos e elementos traços indesejáveis ao meio ambiente. A composição química e as características do XR têm sido objeto de estudo de vários países, variando conforme a região de origem. 1,4-10 Na matriz do XR estão presentes minerais tais como quartzo, feldspatos, argilas (principalmente ilita e clorita), carbonatos (calcita e dolomita), pirita e outros minerais. [11][12][13] Outros elementos químicos também estão presentes no XR como Fe, Al, Mg, Ca, K e P, em quantidades majoritárias, além de elementos em menores proporções como Mn, Zn, Ba, Pb, Mo, Cu, Ni, Cr, Co e Cd, entre outros. As quantidades relativas de cada elemento...

Incorporation of retorted oil shale in Brazilian agricultural soil: An assessment of impacts after successive applications

“…1(e and f) showed that the higher ROS dose (18 Mg ha À1 ) was unable to increase the soil content of barium and arsenic. These results are in agreement with those from Santos et al (2017) and Loeck (2018) which observed that the ROS can be used as a soil conditioner in agriculture without adding harmful elements to the environment.…”

“…This type of study can be used to access soil side-effects caused by any type of soil inputs. The evaluated amendment was retorted oil shale (ROS), whose agronomic efficiency and potential applications were properly documented previously (Santos et al, 2017;Giacomini, 2017;Giacomini, 2017), therefore, its wide use in agriculture are potentially high. The ROS is a solid by-product of the oil, natural gas, and sulphur extraction from oil shale and represents 80e90% of the feedstock weight (around 5.000 tons per day) (Petrobras, 2019;Pimentel et al, 2010).…”

The use of retorted oil shale as urea coating does not modify chemical parameters of free-drained soil solution

“…The EC in soil solution collections obtained similar values in fertilization with U and U+ROS and planting spacing. Our results corroborates those reported by Santos et al (2017) in soil extracts where successive doses of retort shale were applied under field conditions, in which they did not observe changes in EC and inferred that although with higher levels of some elements in ROS, the quantities released were not enough to cause a change in EC values.…”

“…However, in the chemical composition of ROS, trace elements can indicate a potential pollutant from this residue, whose vertical transfer could imply in surface water and groundwater contamination/pollution by the leaching process, but few is known about such potential. Pereira & Vitti (2004) and Santos et al (2017) evaluated the release of metals from ROS and reported that its use did not modify the soil concentrations of toxic metal ions, pointing out the low concentration of the respective trace elements in the ROS, and, in general, the presence of ROS did not contribute to leaching and bioavailability of trace elements, maintaining these elements below threshold levels according to current legislation. However, there is still a need for further information on the leaching of chemical elements present in ROS, mainly considering the employment of ROS in a large quantity, as the continuous use in coated urea for many years.…”