The Pollution Characters And Botanic Regulation Along Meijiang River In Xiushan

Since much emphasis in the phytoremediation research of mining farmland soilwith heavy metal pollution has been put on the pot experiments in laboratory withheavy metal added to clean soil, Xiushan Manganese Mine Area of manganese triangleof China was selected as the study area. First, investment about manganese and othermetal pollution of river sediment, rape field and the rape system along the MeijiangRiver has been made, and then soil from local polluted farmland has been collected forthe pot experiments （tested hyperaccumulation plants were phytolacca Americana andViola baoshanensis）. Chemical regulation was applied in the exploration ofhyperaccumulation mechanism and technology of manganese pollution of the farmlandsoil. Results and major conclusions are as follows:Investments about current pollution of river sediment, rape field and the rapesystem along the Meijiang River showed that:1. Contents of Mn in70%of the river sediment samples along the Meijiang Riverand80%of the farmland soil samples exceeded the background value. And contents ofthe three kinds of heavy metal are: Mn> Cu> Cd., while potential ecological riskfactors of the three heavy metals are Cd> Cu> Mn. Content of Mn in the leaves ofrape planted in farmland along the river was much lower than the background valuebut contents of both Cu and Cd exceeded.2. Heavy metals were better absorbed and enriched by the combination ofPhytolacca Americana and Viola baoshanensis than they were absorbed by PhytolaccaAmericana or Viola baoshanensis alone. It showed that Phytolacca americana+Violabaoshanensis>> Viola baoshanensis> Phytolacca Americana in the absorption effects.3. Regulation effects on the Phytolacca americana of the4chemicals are: citricacid> NaHSO₃> EDTA>（NH₄）₂CO₃; while regulation effects on the Violabaoshanensis under field conditions are: citric acid> EDTA> NaHSO₃>（NH₄）₂CO₃.4. Distribution form of heavy metals in soil showed that: a. regulation effects ofdifferent chemicals on Mn in Phytolacca Americana under field conditions are: citricacid> EDTA> NaHSO₃>（NH₄）₂CO₃; effects on Cu in Phytolacca Americana areEDTA> NaHSO₃> citric acid>（NH₄）₂CO₃; effects on Cd in Phytolacca Americanaare （NH₄）₂CO₃> EDTA> NaHSO₃> citric acid; b. regulation effects of differentchemicals on Mn in Viola baoshanensis under field conditions are: NaHSO₃> EDTA> citric acid>（NH₄）₂CO₃; effects on Cu in Viola baoshanensis are EDTA> NaHSO₃>citric acid>（NH₄）₂CO₃; effects on Cd in Viola baoshanensis are（NH₄）₂CO₃> EDTA>NaHSO₃> citric acid.Conclusions can be drawn from research on botanic regulation of pollutedfarmland soil:1. Potential ecological risk of the sediments along the Meijiang River is moderate,severe; potential ecological risk of the rape field along the Meijiang River is low,moderate. Contents of Mn, Cu and Cd in rape leaves has gone far beyond the nationalfood hygiene standards, and also exceeded the maximum daily intake of an adult, whichputs the health of local population at risk.2. Hyperaccumulation plants advantage combination selection test results showedthat the composition of various hyperaccumulation plants managed to extract severalheavy metals simultaneously, and the extraction effects was better than that of a singlehyperaccumulation plant.3. In simulated field regulation, phytolacca Americana and Viola baoshanensiscannot completely display the feature of hyperaccumulation plants but are still able toabsorb heavy metal excessively.4. The4regulation chemicals acted at different levels in the regulation of the twohyperaccumulation plants’ extraction of three heavy metals Mn, Cu and Cd, and theyshowed the feature of selective regulation. Some regulation chemicals turn the residueof heavy metal in a stable state into organic combination state and sulfide combinationstate heavy metal or iron manganese oxide combination state heavy metal instead ofturning them directly into the carbonate combination state of heavy metal or organiccombination state which can absorbed by plants.