| Planting rice has been main method of improving soda saline-alkali soil. As amendment, Al2(SO4)3has performed better effect on amending the soil to plant rice.But it is not clear that wether Al can influence fluorine in the soil,though it can decrease pH and improve soil physical properties. In order to study the effect of Al applied on the fluorine in soil, the paper took soda saline-alkali soil as experimental soil, on the basis of optimizing fluorine measurement method by electrode, mainly studied the distribution characteristics of fluorine in soda saline-alkali soil, fluorine adsorption/desorption, the effect of Al on fluorine forms and adsorption in soil and the regularities of rice absorbing fluorine. The paper researched fluorine harm from a new angle and provided theoretical support for reducing fluoride bioavailability, controlling of fluorine into the food chain. The main conclusions are as follows:1、When electrode method was used to measure the content fluorine in solution, TISAB consisted of Na3C6H5O7?2H2O、NaNO3、C6H8O7could shelter Al interference, stabilize ion activity of F, adjust pH to suitable range with higher accuracy. The best measure mode was the known addition method. And alkali fusion was better pretreatment method for measurement fluorine content in plant tissue.2、The results of investigation fluorine content in soda saline-alkali soil and water of west Jilin province were that the total fluorine in topsoil was not high and was less than black soil and national fluorine background level in soil, but its content of water soluble and exchangeable fluorine was higher which had high bioavailability and was the reason of endemic fluorosis prevalent in the local. In the soil profile, the content of water soluble、exchangeable、total fluorine in topsoil(0-20cm) were higher than interlayer(20-40cm) because of fluorine aggregating to ground with soil water lifting during sampling period, but total fluorine content in bottom layer(40-60cm) was higher than other soil layers as fluorine was activated lighter by less influence of natural and artificial factors. The distribution of fluorine in soda saline-alkali soil was residual F>water soluble F>Fe/Mn binding F, exchangeable F>organic binding F. The correlation between exchangeable F and other forms F was significantly, so it took bridge function in the transfer of F forms in soil. Fluorine in several ground water and well water exceeded the national standard of drinking water or irrigation water.3、The experiment of fluorine adsorption in soda saline-alkali soil showed that fluorine adsorption and desorption amount in the soil was increased with initial fluorine content increasing and then not change when it reached maximum, but the desorption rate was in trend of decreasing first and then increasing with minimum of62.79%. Langmuir faction fitted the process of F isothermal adsorption in the soil better. From the adsorption dynamics, adsorbed equilibrium time was48hours, and half of adsorbed fluorine was adsorbed in the first hour with95%-97%being desorbed. Dual constant equation could better fit the process of fluorine adsorbed without the influence of initial fluorine content. pH affected soda saline-alkali soil adsorbing fluorine, the lower the pH, the more the fluorine adsorption amount and the less desorption rate. Al shortened fluorine adsorbed equilibrium time, fluorine adsorption amount was increasing and desorption rate was decreasing with Al added improving. As anions content increasing, fluorine adsorption amount was first decreased and then increased, its desorption rate was higher than single fluorine added. When anions-fluorine-Al coexist in the solution, fluorine adsorption amount was more and desorption rate was less compared with anions-fluorine coexist, desorption rate was higher compared with Al-fluorine coexist. Amount of fluorine adsorption and desorption in H2PO4-treatments was higher than other anions.4、In the leaching experiment, the treatments of Al added could decrease fluorine leaching rate in soil compared with no Al added treatments. But its depressed degree was different according to the relative content of Al and F with the results of pH change in soil after Al2(SO4)3applied, the change of Aluminum oxide/hydroxide amount, the charge of Soil colloid and Al releasing by fluorine adsorption. The total fluorine leaching rate was lowest in the1:ltreatment because its adsorption amount was highest and desorption rate was lowest.5、Pot experiment showed that the low concentration of fluorine could promote plant height、stem and leaf、root growing, but the high fluorine concentration played inhibiting role. Fluorine inhibited tiller number and grain dry weight throughout. The order of fluorine content in each part of mature rice was husk>brown rice>root>stem and leaf. As Al2(SO4)3applied increasing, the fluorine content in rice plant decreased first and then increased. Thus, suitable ratio of Al and F might lower fluorine content in rice plant, but it did not change the distribution regulation in each part. Each form of fluorine in soil was increased with initial fluorine content increasing. When Al was added, free fluorine and water soluble fluorine was less than blank control and decreased with Al2(SO4)3applied increasing, residual fluorine increased, other forms of fluorine was in the trend of increasing first and then decreasing. The suitable Al2(SO4)3applied amount in this experiment was0.4%-0.6%which was equivalent to1:1.9-1:8.5of Al and F mole ratio. On this condition, fluorine in each rice plant part and water soluble/exchangeable fluorine in soil was relative low, Fe/Mn and organic binding fluorine was relative high. Although fluorine adsorption amount was not the highest and it desorption rate was not the least, fluorine adsorption amount was higher and desorption rate was lower than blank control. Thus, this ratio of Al to F inhibited fluorine migration to ground water and decreased fluorine in rice plant which reduced fluorine intake amount for animals and human through the food chain. |
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