Multitracer study on the uptake mechanism of yttrium and rare earth elements by autumn fern

Landscape REE anomalies and the cause of geophagy in wild animals at kudurs (mineral salt licks) in the Sikhote-Alin (Primorsky Krai, Russia)

To test the "rare earth" hypothesis of geophagy, geological and hydrogeochemical studies unparalleled anywhere in the world were carried out at kudurs (salt licks) in two districts in the Primorsky Krai, Russia. The mineral and chemical compositions of geophagic earth consumed by animals, the chemical composition of surface waters and vegetation, and the chemical composition of biological tissues of red deer (Cervus elaphus) were studied in this research. It was found that ultra-fresh surface and fontinal waters in the studied areas contain anomalously high concentrations of rare earth elements (REE), the sums of which exceeded the average values in the Primorsky Krai and worldwide by tenfold, and more. The presence of landscape REE anomalies is confirmed by elevated concentrations of these elements in vegetation. Using electron microscopy, it was determined that the sources of REE in landscape components are rocks containing secondary, readily soluble, REE minerals (hydrophosphates and fluorocarbonates). The study of the chemical composition of animal tissues showed the presence of significant concentrations of heavy REE (HREE) in the blood and brain, which indirectly indicates a high probability of animals developing stress reactions against the background REE-elementosis. Eaten earthy substances in both areas are represented by mixtures of smectite clays and zeolites with high ion-exchange properties. In the digestive tract of animals, such sorbents actively interact with the biological electrolyte, saturating it with sodium ions and absorbing HREE. The main meaning of geophagy is regulation of the concentration and proportion of REE in the body. Sometimes it manifests itself in intake of significant amounts of Na.

The Biogeochemistry of Lantanides in Soils

The lithogenous minerals containing lantanides (Ln) are unsustainable within the zone of hypergenesis. Their dilution impoverish soils in terms of lantanides content, especially in humid regions. In conditions of neutral environmental pH in dry steppe zone, the lantanides loose their mobility, and, hence, become unavailable for plants. The lantanides are characterized by the high biochemical and biological activity. The physiologic impact of lantanides on plants is set. The separate parts of vascular plants accumulate lantanides in different degree. The difference may reach 100-fold level. For many plants the accumulation of lantanides occurs at the reverse order: roots > leaves > stalks > grain/fruits. Lantanides accumulators (such as brackens), promote their accumulation within the humus layer of soils. Fertilizers with lantanides are widely implemented in China. They powder seeds and implement top dressing in soils with lantanides deficit, i.e., with low bulk content and/or with low availability for plants. Although at moderate increasing of Ln concentration in solution, there is often observed the increasing of the crop yield in laboratory conditions. However, the implementation of lantanides in the soil does not always give the positive effect. The main share of Ln in the soils with high sorption capacity is sorbed, and the increasing of doses leads to the decrease of the yield. The light lantanides are characterized by physical and chemical properties equal to Cа2+. And the mass replacement of Cа2+ by lantanides harms the development of plants. The high doses of lantanides have a negative impact on the biochemical processes in plants. The competition with iron and phosphorus is stipulated by the close solubility of iron and lanthanum phosphates: the accumulation of La in plants tissues affects the content of P and Fe within them.

Rare earth elements: Yttrium and higher plants

Rare earth elements (REEs) form a chemically uniform group with very similar physical and chemical properties. The REEs include the elements scandium, yttrium, and the lanthanides from lanthanum to lutetium. They are widely distributed and present in all parts of the biosphere. REEs are required in industry, agriculture, medicine, biotechnology, environmental problems and many other fields. Lately, many experiments show their positive or negative, first of all nonspecific, effect on life processes of higher plants as well as growth and yield of cultivated species, but the physiological mechanisms are still not well understood. It has been determined that yttrium is widely distributed in plants, as well as that certain plant species uptake yttrium at different extent. Its highest accumulation is in the root and the leaf. Although yttrium was discovered more than two centuries ago, its effect on higher plants - their anatomical and morphological built, physiological and biochemical processes etc. - is very little known. One of the basic reasons is that yttrium, as well as other REEs elements, according to current knowledge, is not biogenic for higher plants and - wider - for live organisms. The objective of this paper is to concisely show previous knowledge about yttrium in the plant world.

Isotopic tracer studies of chemical behavior of rare earth elements in environmental and biological sciences

Rare earth elements (REE), a group of elements with atomic numbers from 57 to 71, have been widely applied in recent years not only in industry but also in agriculture, forestry, animal husbandry and medicine. Numerous anthropogenic activities make REE to easily enter the environment and finally the human body via the food chain. Therefore, detailed studies on chemical behavior of these metals in environmental and biological systems are imperative. Isotopic tracer method is especially suited to such studies and has played an important role in assessing the environmental effects of REE. In this paper, some recent progress in the study of chemical behavior of REE in environmental and biological sciences made by the isotopic tracer method is outlined.

Multitracer Screening: Brain Delivery of Trace Elements by Eight Different Administration Methods

Trace elements are closely associated with the normal functioning of the brain. Therefore, it is important to determine how trace elements enter, accumulate, and are retained in the brain. Using the multitracer technique, which allows simultaneous tracing of many elements and comparison of their behavior under identical experimental conditions, we examined the influence of different administration methods, i.e., intravenous (IV), intraperitoneal (IP), intramuscular (IM), subcutaneous (SC), intracutaneous (IC), intranasal (IN), peroral (PO), and percutaneous (PC) administration, on the uptake of trace elements. A multitracer solution containing 16 radionuclides (i.e., 7Be, 46Sc, 48V, 51Cr, 54Mn, 59Fe, 56Co, 65Zn, 74As, 75Se, 83Rb, 85Sr, 88Y, 88Zr, 95mTc, and 103Ru) was used. The results indicated that the 83Rb brain uptake rate with intranasal administration was approximately twice those obtained with the other administration methods. This result indicated that a portion of Rb was delivered into the brain circumventing the blood circulation and that delivery could be accomplished mainly by olfactory transport. Multitracer screening of trace element delivery revealed differences in brain uptake pathways among administration methods.