Fluoride problems in Moldova 69
SOME OBSERVATIONS ON FLUORIDE PROBLEMSIN THE MOLDOVA REPUBLIC
S Toma,a J Kreidman,a O Vedina,b and S Veliksara
Chishinau, Moldova, and Logan, Utah USA
SUMMARY: Fluoride content was determined in different soil types of Moldova. The total fluoride concentrations varied in soils depending on their granular composition. Flood sodic soils are characterized by the highest content of fluoride - up to 1120 ppm. The level of water-soluble fluoride ranged from 0.2 to 14.6 ppm. Long-term phosphoric fertilizer application and irrigation with fluoride-containing water have led to fluoride accumulation in soil and plants.
Keywords: Anthropogenic impact, Fertilizers, Fluoride pollution, Fluoride content, Moldova.
INTRODUCTION
Fluoride (F) is of special interest as a pollutant of the environment. Insufficient knowledge about the nature and magnitude of environmental fluoride pollution has led to underestimation of its damaging effects on plants, animals and humans. It is possible there is a connection between environmental fluoride pollution, certain ecological changes and manifestation of some diseases (Siberian ulcer, cancer etc.).1-3
The purpose of this study was to investigate changes in fluoride content in soils, water, and plants of Moldova, and to examine the influence of different doses of phosphoric fertilizers and irrigation with water containing fluoride.
MATERIALS AND METHODS
The content of fluoride was investigated in ground-litter rocks of different geological age,4 in subsurface waters, and in the main soil types and subtypes of Moldova.5-7 The samples were collected from 72 sections and 14 drill holes in the 4 soil provinces. Fluoride content in soils was determined in different genetical horizons at a depth of 230 cm. For some samples, the content of fluoride was determined theoretically using special equations of regression.7-8
The influence of long-term (23 years) phosphate fertilizer application and irrigation on the fluoride content of soils and plants was also examined. Fluoride determinations were conducted with alizarin complexing without preliminary distillation.9
RESULTS AND DISCUSSION
Moldova Republic is situated in Eastern Europe. It borders Romania on the west and the Ukraine on the northeast and south. In terms of the geological structure, the territory belongs completely to the southwestern slope of the Russian platform, and only its southern portion is part of the Scythian plate. The majority of the sedimentary rocks are submerged in the southwest and make Pre-Dobrudja deep glades in the south.4
In the foundation of the Upper Cretaceous layer a basal conglomerate is observed, which consists of slightly worn fragments of underlying rocks with phosphorite accumulations up to 34,000 mg/kg.
The range of the total fluoride in the soils depends on their granular composition (Table 1). Thus the super-sandy soils contain 64 to 269 ppm of fluoride, and sodic soils 542 to 794 ppm. Flood soils are characterized by a high content of fluoride - 500 to 1120 ppm. The concentrations of water-soluble fluoride range from 0.2 to 14.6 ppm, or less than 1% of total fluoride content.
Table 1. Total and water-soluble fluoride in soils of Moldova (depth 0-50 cm).
Soiltypes / Granular
composition / Total F (ppm) / Water soluble F (ppm)
min / max / min / max
Forest soils
Burozem (steppe
brown soil) / super sandy / 64 / 247 / 0.6 / 2.3
heavy loam / 260 / 509 / 0.8 / 2.9
Light grey
forest / super sandy / 90 / 220 / 0.8 / 1.8
light and
medium loam / 161 / 558 / 0.2 / 5.8
Grey forest / super sandy / 68 / 269 / 0.2 / 3.5
light and
medium loam / 185 / 859 / 0.2 / 4.1
Dark grey forest / heavy loam / 87 / 648 / 0.3 / 4.1
Chernozems (Steppe soils)
Podzolic / heavy loam light and medium clay / 123 / 761 / 0.7 / 14.6
Leached / light and
medium loam / 127 / 750 / 0.8 / 3.8
Calcareous / light-medium and heavy loam / 250 / 652 / 1.0 / 3.9
Sodic soils / heavy clay / 542 / 794 / 0.3 / 6.7
River valley
soils / light clay / 500 / 1120 / 0.6 / 4.3
heavy loam / 285 / 1050 / 0.4 / 4.3
Subsurface waters are used in Moldova as a water source. The Cretaceous water-bearing horizon is saturated with fluoride. High fluoride concentrations are found in mixed waters containing chalk and torton; the water of lower Sarmatian deposits has lower concentrations of fluoride (up to 0.5 mg/L) and constitutes a major part of the territory.
The anthropogenic contribution of fluoride to total soil content was also studied. The reaction of soils and plants to different doses of phosphoric fertilizers and irrigation with water containing fluoride was investigated. The content of fluoride in the above-ground part of wheat at the growth stage of 5-7 leaves was 6.13 (without fertilizers) and 10.38 mg/kg dry weight (after 23 years of superphosphate application). The concentration of fluoride in grain and roots was much lower than in leaves. Long-term superphosphate application leads to retarded growth, chlorosis, and yield reduction of wheat because of fluoride toxicity.
The water used for irrigation in the southern part of Moldova contains relatively high levels of fluoride. The effect of this water on the fluoride content in wheat was studied during a 5-year period (Table 2). The irrigation of wheat with fluoride-containing water increased the content of fluoride in plants, especially at the stage of tillering and in stems at the stage of booting. High levels of fluoride in soil were observed after irrigation with fluoride-containing water.
Table 2. Change in fluoride content of wheat grown on calcareous light
chernozem (steppe soil) after irrigation with fluoride-containing water.
no irrigation / after irrigation
Tillering / Whole plants / 12.2 / 28.2
Booting / Stems / 4.7 / 13.8
Leaves / 10.7 / 10.0
Fluoride research on stockbreeding was also carried out. Fluorosis in animals can occur subsequent to absorption of fluoride from potable water (85-91% of fluoride is assimilated from it) and from ingested materials (forages and fodder mineral additions), especially from grass grown on the soil after long-term treatment with phosphoric fertilizers (40-50% fluoride assimilation from ingested materials).
The degree of animal fluorosis has also been investigated, especially in spotted, cretaceous-pigmented, speckled, and deformed teeth. Fluoride likewise accumulates in animal organisms, mainly in bone tissue. A high content of fluoride impedes some metabolic processes and also disturbs the function of the liver and the thyroid gland.3,9
CONCLUSION
There are many problems connected with fluoride in the environment in the territory of Moldova. Regions exist with high and low levels of fluoride in potable water. Some have high accumulation of fluoride in soils and plants after long-term application of phosphate fertilizers, and the animals suffer from elevated fluoride intake. Under conditions of high fluoride pollution it is important to minimize exposure and to investigate its environmental and ecological consequences.
REFERENCES
1 Shliahov E, Prisacaru V. Epidemiological supervision of Siberian ulcer. Chisinau (Kishinev): Stiinza, 1989 (in Russian).
2 Gaponiyk E. Degree and ecological consequences of fluoride contamination. Obninsk: Hydrometheorology, 1983 (in Russian).
3 Toma S, Kreidman J. Fluoride problems in Moldova: Review. Chisinau (Kishinev): MoldNIITI, 1997 (in Russian).
4 Dziadevich G. Fluoride determination in soils and waters using alizarin complexing without preliminary distillation. Moscow: MSU, 1974 (in Russian).
5 Drumia A. Ecological structure. Atlas of Moldova Republic. Moscow: GUGiK, 1978 (in Russian).
6 Feldman E. Medical-geographical investigation of the territory of Moldova. Chisinau (Kishinev): Stiinza, 1977 (in Russian).
7 Petrasov E. Geochemistry of fluoride in water of Moldavian artesian basin. Leningrad: Nauka, 1973 (in Russian).
8 Kreidman J. Fluoride in soils of Moldova. Chisinau (Kishinev): Stiinza, 1992 (in Russian).
9 Kreidman J. Formulae for fluoride content calculation in chernozems, forest and river valley soils. In: Anthropogenic volution, evaluation and methods of soil study. Chisinau (Kishinev): Stiinza, 1992: 95-107 (in Russian).
10 Mandric F, Iacubovscaja I. Prophylactic and measures of control of fluorosis in Moldova: review. Chisinau (Kishinev): MoldNIITI, 1981 (in Russian).
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Published by the International Society for Fluoride Research
Editorial Office: 17 Pioneer Crescent, Dunedin 9001, New Zealand
Fluoride 32 (1) 1999