Soil fluoride fractions and their bioavailability to tea plants (Camellia sinensis L.)

Environ Geochem Health. 2017 Oct;39(5):1005-1016. doi: 10.1007/s10653-016-9868-3. Epub 2016 Sep 3.

Abstract

Drinking teas containing high fluoride (F) imposes fluorosis risk. The soil F bioavailability is an important factor influencing its uptake and contents in teas. The present work was conducted to investigate F fractions in soil and their bioavailability to tea plants. Tea seedlings were cultivated on 6 typical soils treated with a mixture consisting of dolomite, lime, peat and KCl at variable rates in the pot experiment. Soils and young shoots were collected in pairs from 63 sites of 21 plantations in a field experiment. Soil fluoride was sequentially separated into hot water soluble [Formula: see text], exchangeable [Formula: see text] (by 1 mol L-1 MgCl2, pH = 7.0), F bound to Mn and Fe hydroxides [F(oxides,s)], and organic matter [F(OM,s)] or extracted independently by water [Formula: see text] or 0.01 mol L-1 CaCl2 solution [Formula: see text]. Averaged [Formula: see text], [Formula: see text], F(oxides,s) and F(OM,s) accounted for 51, 14, 5 and 30 % of the total sequential extracts, respectively. There were significant correlations among [Formula: see text], [Formula: see text] and F(OM,s). Fluoride contents in leaves correlated with [Formula: see text] (r = 0.71, p < 0.001), [Formula: see text] (r = 0.93, p < 0.001) and F(OM,s) (r = 0.69, p < 0.01) but not other fractions in the pot experiment and with [Formula: see text] (r = 0.43-0.57, p < 0.001) and [Formula: see text] (r = 0.42-0.79, p < 0.001) in the field experiment. It was concluded that 0.01 M CaCl2 extractable fluoride can be a good indicator of soil F bioavailability to tea plants. The significant correlations among some of the F fractions suggested that F in solution, AlF complexes (AlF2+, AlF2+) and those bound to organic matter likely represent the available pools to tea plants.

Keywords: 0.01 M CaCl2 extractable fluoride; Correlation analysis; Fluoride content; Sequential extraction; Water extractable fluoride.

MeSH terms

  • Biological Availability
  • Camellia sinensis / metabolism*
  • China
  • Environmental Monitoring
  • Fluorides / analysis
  • Fluorides / metabolism*
  • Soil / chemistry*
  • Soil Pollutants / analysis
  • Soil Pollutants / metabolism*

Substances

  • Soil
  • Soil Pollutants
  • Fluorides