Spatial variability and solubility of barium in a petroleum well-drilling waste disposal area.

The petroleum industry generates a range of wastes which is often are disposed in soil close to the well location, negatively affecting soil and water quality. The objective of this study was to evaluate the solubility and map the spatial variability of barium in a potentially contaminated area. The study area consisted of a petroleum well-drilling waste disposal site located in the municipality of Mato Rico-PR. A large georeferenced sampling grid was organized. Soil samples were collected at depths of 30, 60, 90, and 120 cm for determination of the "pseudo-total" concentrations and geochemical fractionation of barium. The barium concentrations showed spatial dependence, which permitted the use of geostatistical interpolators. Regarding depth, the depth of 0-30 cm showed the largest contaminated area; however, higher concentrations of barium were found at the depth of 60-90 cm. The results of geochemical fractionation showed that the analyzed samples contained percentages higher than 99% in the non-labile fraction (residual). These results indicate clearly that the barium was in a condition of low solubility, even for samples that had the highest concentrations, presenting low-environmental risk.

The effects of oil well drill cuttings on soil and rice plant development (Oryza sativa) under two redox conditions.

Few studies have focused on the release of toxic elements from oil well drill cuttings and their effect on soil. The present study evaluated these effects using rice growth as the endpoint. Drill cuttings were collected from a Brazilian well and added in doses of 300, 3,000 and 6,000 mg kg(-1) soil, which was maintained at oxidized or reduced conditions. When the redox potential reached approximately -250 mV, barium concentrations were determined by geochemical fractionation. Overall, doses of 300 and 3,000 mg kg(-1) promoted plant development, while a dose of 6,000 mg kg(-1) inhibited it due to the associated increase in electrical conductivity and exchangeable sodium concentration. In addition, the lower redox potential promoted solubilization of barite from the drill cuttings, which increased barium absorption by plants and translocation to grain, posing a risk to human health.

Effect of variations in the redox potential of Gleysol on barium mobility and absorption in rice plants.

Two assays were designed to obtain information about the influence of redox potential variations on barium mobility and bioavailability in soil. One assay was undertaken in leaching columns, and the other was conducted in pots cultivated with rice (Oryza sativa) using soil samples collected from the surface of Gleysol in both assays. Three doses of barium (100,300 mg kg(-1) and 3000 mg kg(-1)-soil dry weight) and two redox potential values (oxidizing and reducing) were evaluated. During the incubation period, the redox potential (Eh) was monitored in columns and pots until values of -250 mV were reached. After the incubation period, geochemical partitioning was conducted on the barium using the European Communities Bureau of Reference (BCR) method. Rainfall of 200 mm d(-1) was simulated in the columns and in the planting of rice seedlings in the pots. The results of the geochemical partitioning demonstrated that the condition of reduction favors increased barium concentrations in the more labile chemical forms and decreased levels in the chemical forms related to oxides. The highest barium concentrations in leached extracts (3.36 mg L(-1)) were observed at the highest dose and condition of reduction at approximately five times above the drinking water standard. The high concentrations of barium in the soil did not affect plant dry matter production. The highest levels and accumulation of barium in roots, leaves, and grains of rice were found at the highest dose and condition of reduction. These results demonstrate that reduction leads to solubilization of barium sulfate, thereby favoring greater mobility and bioavailability of this element.

Zinco, chumbo e cádmio em plantas de arroz (Oryza Sativa L. ) cultivadas em solo após adição de resíduo siderúrgico / Zinc, lead and cadmium influence in rice plants (Oryza Sativa L. ) cultivated in soil with addition of siderurgical residue

Os efeitos da aplicação de resíduo siderúrgico, proveniente da concentração de zinco em lama de altos-fornos siderúrgicos, como fonte de zinco para plantas de arroz (Oryza Sativa L.) BRS Curinga e a toxicidade devida ao cádmio e ao chumbo no resíduo, foram estudados em experimento de casa de vegetação. O material de solo usado foi proveniente do horizonte A e B de um Latossolo Vermelho-Amarelo e do horizonte A de um Neossolo Flúvico, coletados no município de Pinheiral, Estado do Rio de Janeiro. Foram aplicadas quatro doses de resíduo (94; 281; 844 e 2531kg ha-1). Foi determinado o teor de zinco, cádmio e chumbo na raiz e na parte aérea das plantas de arroz. As plantas crescidas no horizonte A do Neossolo Flúvico apresentaram a maior produção de matéria seca e a maior acumulação de zinco e a menor de cádmio. As plantas de arroz desenvolvidas no horizonte B do Latossolo apresentaram a menor produção de matéria seca, menor acumulação de zinco e a maior de chumbo, enquanto que as cultivadas no horizonte A do Latossolo apresentaram a mais elevada produção de matéria seca dos três substratos utilizados. O zinco e o chumbo concentraram-se, principalmente, nas raízes das plantas, e o cádmio se concentrou na parte aérea. Pelas características apresentadas nos solos estudados e pelas concentrações fitotóxicas do chumbo e do cádmio encontradas nas plantas desenvolvidas sobre o horizonte B do Latossolo, não é recomendável a utilização desse resíduo como fonte de zinco para a cultura do arroz.

The effects of application of siderurgical residue, originated from the zinc concentration in siderurgical high-ovens mud, as supply of zinc for rice plants (Oryza Sativa L.) and the toxicity due to cadmium and lead from the residue, were studied in a greenhouse experiment.The period of the experiment was from April of 2005 to March of 2006. The soil materials were from the A and B horizons of a Yellow - Red Oxisol, and the A horizon of an Entisol, from Pinheiral municipality, State of Rio de Janeiro, and the rice (Oryza Sativa L.) variety utilized was the "BRS Curinga". There were applied four dosages of residue (94; 281; 844 and 2531kg ha-1) plus the testimony, without residue. The amount of zinc, cadmium and lead was determined in the root and aerial part of the rice plants. The plants cultivated in the A horizon of the Entisol presented the biggest dry biomass production, the highest zinc accumulation, and the smallest cadmium level. The plants cultivated in the Oxisol B horizon had the smallest dry biomass production, lowest zinc accumulation, and the highest level of lead. As for the Oxisol A horizon, the rice plants showed a good dry biomass production. The zinc and lead concentrated, mainly, in the roots; and cadmium in the aerial part. Based on the characteristics of the studied soils, and the fitotoxicity by lead showed in the rice plants grown on the Oxisol B horizon, the application of the siderurgical residue, is not recommended, as a zinc source for the rice crop.