Lithium in agriculture, environment and food

Due to increasing interest in lithium, and before a possible era of more intense use, a compilation of respective data from multi-element datasets of the author seems to be needed. All data have been obtained from ICP-OES, run against matrix-matched calibrants. Average global abundances of 22 mg/kg in the Upper crust, 13 mg/kg in the Lower crust and 18 mg/kg in the Continental crust rely on total decomposition digests. After weathering, Li is quickly removed from solution by clay minerals and Fe-oxides, but hardly by organics. Total digestion data of 24432 stream sediment of Slovakia showed an elevated occurrence of Li in the High and Lower Tatra mountains and in the Beskides (34-70 mg/kg), whereas in the Lowlands it ranged largely within 22-29 mg/kg. Similarly in Austria, stream sediments in the Pre-alpine Lowland ranged within 16-26 mg/kg, and in the limestone Alps within 5-16 mg/kg.

In soils, however, aqua regia digestion or alternatively, pressure digestion with K-chlorate in dilute nitric acid, is commonly used, which resulted in a median recovery of 57 % (range 44-100%) in apple orchard soils, and of about 54% in a calcareous fluvisol, which had been treated by various fertilization regimes. In these digests, Li is positively correlated with K, Sc, Y, Al, La, Ni, Cr and Tl, but negative or independent versus Ca, Sr, Ba and organic carbon. In profiles of wood soils from the South of Carinthia, both increase and decrease of aqua regia soluble Li was noted versus depth.

In urban soils and road dusts, Li had been detected within the range of arable soils, no enrichments had occurred.

In mobile soil fractions, Li mobility is quite low. Data obtained from various extracts like CAL (Ca-acetate-lactate), dilute acetic acid or ammonium acetate will be compared: In CAL, released Li corresponds with Na, while it is largely independent from Mg, Sr and Ba. In orchard soils, just 0,52% of total (range 0,12-1,17%) were released by 0,16M acetic acid, and in subsequent oxalate extract pH 3 just 1,38% (range 0,41-6,27%) as medians, and in the carbonaceous fluvisol, the acetic acid released even only 0,36%, and subsequent oxalate 0,20% of total.,

In fertilizers, based on NH₄, K and Mg salts, median occurrence of Li is below 0,5 mg/kg. in NPK fertilizers about 1 mg/kg, and in composts 14 mg/kg. Thus, there is no significant Li input into soils from fertilization. Median inputs for 100 kg N/ha or 100 kg P/ha increase from mineral fertilizers to commercial organics, to manures and dungs, to composts. Slight but insignificant changes between different geological locations appeared among the composts.

Addition of NPK fertilizer leads to mobilization of Li by ion exchange. From columns of chernozem soils, a Li peak occurred after passage of one pore volume of eluting water.

Animal feedstuffs contain Li within the same concentration ranges as mineral fertilizers, with medians from 0,6 to 2,0 mg/kg. The concentration ranges are largely overlapping with respect to target animals, both for composite and supplementary feeds. The stomach-contents of wild ducks shot in 4 areas of Austria, contained Li within the same range as commercial feedstuffs for chicken or turkeys. Because basic feeds like grass-silage may contain higher Li-levels, concentrations in manures, dungs and composts may be also higher.

Li levels in meat and vegetables have been found largely overlapping at about 10-70 µg/kg of dry mass, which means about 1- 7 µg/kg in wet weight. Higher levels can be (but need not be) met in processed cheese, as well as in horse meat and deer. Like for most elements, honey contains the presumably lowest Li level, at a median of 3,5 µg/kg (range <0,1 - 30 µg/kg), at almost dry weight.

Data from cereals, potatoes, tomatoes, carrots, milk, cheese, various kinds of meat, and honey will be presented.