| With the development of agricultural modernization and the adjustment of planting structure,facility agriculture has become the new industry in modernized agriculture.Now the national infrastructal agriculture area is about 4 million hm2,and the facilities vegetables accounted for over 95% of the total area of the facility.In 2010,greenhouse vegetable production reached over 170 million tons in China,which accounted for about 25% of the total vegetable production.Due to the characteristics of human strong activities affecttion and the over irrigation and fertilization,and causing soil harden,secondary salinization and other environmental problems.The physical and chemical properties in soil change with the time increasing of the facility cultivated,and then influencing the activity of heavy metals in soil.So it gives rise to the environmental problem of soil heavy metal accumulation,with Pb and Cd exceeding bid more seriously.Soil secondary salinization and heavy metal accumulation in soil have become the main factors to hinder the sustainable development of facility agriculture in our country.Thus,restoring the secondary salinization and heavy metal compound pollution soil is an urgent evironmental problem to be solved in facility agriculture.At present,the common methods to remedy saline soil mainly include engineering,chemical,biological and agricultural measures.Although these measures have achieved some success,these methods have disadvantages of long remediation time,high cost,low efficiency.Until now,the remediation techniques of heavy metal polluted soils mainly include replace the polluted soil,heat treatment,electrokinetic remediation,phytoremediation,chemical fixation and leaching methods.However,there are still some defects,such as high construction investment,high running cost,easy to cause sencondary pollution.It is essential to combine with multiple measures.Halophytes have strong desalting ability.Some halophytes showed certain enrichment ability to heavy metals,and showed great potential to extract heavy metal from soil.Moreover,the biological effectiveness of heavy metal can be improved by chelating agent,and then the removal percents of heavy metal by plants are higher.EDTA is widely used to strengthen the plant remeding of heavy metal contaminated soil,and the effect is good.So the combination applied of halophytes and EDTA to repair heavy metal pollution salt soil has a broad development prospect.However,few reports on the reseach to repair heavy metal pollution salt soil can be found,and the report on application of EDTA with the halophytes in repairing heavy metal contaminated saline soil is less fewer.In this study,the removal effect of Sedum aizoon L.,Suaeda salsa and Alfalfa to NO3-,Cl-and SO42-in simulation saline soil were investigated by pot experiment,and screened the optimal plants to removal of the anions.The extract efficiacies of Pb and Cd in the simulation Pb,Cd pollution soils were examined by the combination with different levels of EDTA and three halophytes,and screened the optimal plants to remediate the Pb,Cd pollution soil and optimize the EDTA addition concentration.According to the results of the above experiments,the remediation efficiacies of simulation Pb,Cd polluted saline soil were studied,and screened the optimal plant to remediate the Pb,Cd pollution salinized soil.Then using Sedum aizoon L.with 4 mmol/kg EDTA repair the actual pollution soil,and investigated the remediation efficiacies of actual pollution soil.The main results were obtained as follows:1.After transplanting halophytes 70 days,the removal experiments of soil anion(NO3-?SO42-?Cl-)in simulation saline soil concluded that: Under 0.15% soil salinity,the bimass of all of the three kinds of halophytes were higher than control;and the removal percent of NO3-by Sedum aizoon was 68.56%;and the removal percents of SO42-and Cl-by Alfalfa were 53.46% and 66.42%.Under 0.45% soil salinity,the bimass of Suaeda salsa were higher than control,but the other 2 kinds of plants were lower than control;and the removal percents of NO3-,SO42-,Cl-by Sedum aizoon were 68.36%,47.36%,57.38% respectively.Under 0.75% soil salinity,none of Alfalfa was survival and the growth of Sedum aizoon was inhibited,but the bimass of Suaeda salsa were higher than control;the removal percents of NO3-by Sedum aizoon was 35.68%;and the removal percents of SO42-and Cl-by Suaeda salsa were 31.83% and 31.25%.The results show that the ability of removal anionic by Sedum aizoon is stronger at the low salinity levels,while the ability of removal anionic by Suaeda salsa is more stronger at the high salinity levels.2.After transplanting halophytes 70 days,the removal experiments of Pb,Cd in simulation heavy metal polluted soil concluded that: The increasing of Pb,Cd concents in soil had little influence on the growth of all the three kinds of halophytes.The best removal effect of Pb,Cd by halophytes was Sedum aizoon under mild,moderate and severe pollution soil conditions,and the removal percent of Cd was a little higher than Pb under the same conditions.With addition EDTA,both the removal percent of Pb,Cd in soil and the accumulation of Pb,Cd in plants increased.The best removal effect of Pb,Cd was obtained when addition of 4 mmol/kg EDTA,and the largest removal percents of Pb were 30.84%,32.59%,28.78%,and the largest removal percents of Cd were 34.22%,36.47%,35.83% under mild,moderate,severe pollution soil conditions,respectively.After addition of EDTA,both the TF and BCF of all the three kinds of halophytes increased in different extent.It further illustrates that the removal effect of Pb,Cd can be increased with addition of EDTA.With the addition of 4 mmol/kg EDTA,the extract efficiacies of Pb,Cd were best.Moreover,the accumulation ability of Pb,Cd by Sedum aizoon was strongest.3.After transplanting halophytes 70 days,the removal experiments of Pb,Cd in simulation heavy metal polluted saline soil concluded that: Under 0.15% soil salinity,both the bimass of the two kinds of halophytes were higher than control;under 0.45%,0.75% soil salinity,the bimass of Suaeda salsa were higher than control,but the bimass of Sedum aizoon were lower than control.Under 0.15% soil salinity,the removal percents of NO3-,SO42-,Cl-by Sedum aizoon were 71.23%,51.67%,58.27%.Under 0.75% soil salinity,the removal percent of NO3-by Sedum aizoon was 37.42%,the removal percents of SO42-,Cl-by Suaeda salsa were 31.83%,31.68%.The removal percents of Pb by Sedum aizoon were 41.37%,41.21%,38.56%,and the removal percents of Cd were 47.25%,45.67%,45.39% under mild,moderate,severe pollution soil conditions.The BCF and TF of Pb,Cd by Sedum aizoon were higher,but declined under high salinity.The result showed that with the increasing of soil salinity,the removal effect of Pb,Cd increased.It is found that by analysising the physiological and biochemical index(chlorophyll,proline,MDA,SOD)of plants: the intimidation reflection of Sedum aizoon was more strongly with the increasing of soil salinity,but soil salinity variation had little influence on the growth of Suaeda salsa;and at the same level of soil salinity,Pb and Cd concentration variation had no significant influence on the growth of plants.4.Using Sedum aizoon with EDTA to repair the actual pollution soil,the maximal removal percents of Sedum aizoon for NO3-,SO42-and Cl-were 59.22%?42.11% and 51.65%,and the removal effects of Pb,Cd attained 37.87%,41.61%,and the contents of Pb,Cd in shoots of Sedum aizoon were 486,5.16 mg/kg dry weight.The removal effects of Pb,Cd and anion in soil by Sedum aizoon were significant,it is an effective method of remediation of heavy metal and salination combined pollution soil. |
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