Inputs of rare earth elements in Brazilian agricultural soils via P-containing fertilizers and soil correctives.

The mineral exploration of rare earth elements (REEs) and their entry into the soil via fertilizers has generated concern about environmental impacts and human health risks. We evaluated 60 samples of limestone, gypsum and phosphate fertilizers marketed in Brazil in order to characterize their contents, signature and solubility of REEs. The fertilizers from igneous origin presented the largest accumulation of REEs. Accumulation of the light REEs Ce, La, Nd, Pr, Sm and Eu were larger than the heavy REEs (Y, Dy, Gd, Er, Yb, Ho, Tb and Lu). The solubility of fertilizers produced from sedimentary sources was greater than that of igneous sources. The mean annual REEs contribution of SSP and organo-mineral + phosphate rock (both of igneous origin) to soils was > 4000 t year-1, with highest additions for Ce, La, Nd and Y. Thus, phosphate fertilization and liming were considered to be significant sources of REEs and soils receiving continuously high doses of these inputs are likely to be enriched in REEs. Risk assessment studies are necessary to evaluate the impact of these REEs additions to soils on human health.

Laryngeal Neuropathy in Adult Goats With Copper Deficiency.

The aim of this study was to elucidate the cause of a neurological syndrome characterized by stridor in adult goats with clinical signs of copper deficiency. The main clinical signs consisted of apathy, emaciation, pale mucous membranes, mucous nasal discharge, dyspnea, severe achromotrichia, diffuse alopecia, torpor, ataxia, and stridor. When the goats were forced to move, the stridor increased. In a herd of 194 Toggenburg goats, 10 adult goats with clinical signs of copper deficiency were removed from the herd and divided into 2 groups: group 1, which consisted of 4 nannies and 1 buck with stridor, and group 2, which consisted of 4 nannies and 1 buck without stridor. Group 3, used as a control, consisted of 5 adult goats from another flock without any clinical signs of disease. The mean serum copper concentrations were 1.3 ± 0.3 µmol/L in group 1, 8.1 ± 1.1 µmol/L in group 2, and 11.3 ± 2.2 µmol/L in group 3. The mean serum iron concentrations were 42.3 ± 14.2 µmol/L in group 1, 39.1 ± 8.2 µmol/L in group 2, and 20.6 ± 6.1 µmol/L in group 3. The main histological lesions in goats from group 1 were axonal degeneration of the recurrent laryngeal nerves and atrophy of the muscles of vocal folds and of the dorsal cricoarytenoid and right and left cricothyroid muscles. Goats with ataxia had neuronal degeneration and necrosis of cerebellar Purkinje cells and of the cranial cervical ganglion. We concluded that the stridor was caused by axonal degeneration of the recurrent laryngeal nerves due to the severe copper deficiency.

Accumulation of arsenic and nutrients by castor bean plants grown on an As-enriched nutrient solution.

Phytoextraction is a remediation technique that consists in using plants to remove contaminants from soils and water. This study evaluated arsenic (As) accumulation in Castor bean (Ricinus communis cv. Guarany) grown in nutrient solution in order to assess its phytoextraction ability. Castor bean plants were grown under greenhouse conditions in pots containing a nutrient solution amended with increasing doses of As (0, 10, 50, 100, 250, 500 and 5000 microg L(-1)) in a completely randomized design with four replications. Shoot and roots dry matter production as well as arsenic and nutrient tissue concentrations were measured at the end of the experiment. The results showed that increasing As concentration in nutrient solution caused a decrease in shoot and root biomass but did not result in severe toxicity symptoms in castor bean growing under a range of As concentration from 0 to 5000 microg L(-1). The As doses tested did not affect the accumulation of nutrients by castor bean. Although castor bean did not pose characteristics of a plant suitable for commercial phytoextraction, it could be useful for revegetation of As-contaminated areas while providing an additional income by oil production.