Biological Effects Of Yttrium, Bioleaching Agent Thiamine Single And Combined Stress On Earthworms

In recent years, with strong production of ion rare earth mining, the first "surfacemining-pool leach" process gradually development of in-situ leaching mining technology in ourcountry. The emissions of residual ore leaching agent contains so large number of rare earth oxideand （NH₄）2SO₄（ammonium sulfate） that have impact on the surrounding farmland soil ecologicalenvironment. Earthworms are indicator of the soil ecological environment health, which havebecome the target receptors of many pollutants biological effectiveness research. At present, thestudy that the heavy metals and pesticide pollution on earthworm biological effectiveness aremore, but about rare earth ore leaching residue ore agent pollution on earthworm biologicaleffective research has not been reported out. In this paper, to LongNa rich Yttrium（Y） rare earthore leaching mine pollution of farmland soil as the research background, the acute toxicity andbody antioxidant enzyme the influences of Y、（NH₄）2SO₄single and composite to earthwormswere performed on further research in order to know the emissions of residual ore leaching agentimpacted on the soil biological hazard in process of in-situ leaching ore mining rare earth ore, forthe rare earth ore development activities of contaminated farmland soil toxicology diagnosis andprovide scientific basis for ecological reclamation.The acute toxicity of Y、（NH₄）2SO₄single and composite to earthworms was studied by themethods of contact filter paper test and natural soil test. The results showed that the single toxicsequence of Y and （NH₄）2SO₄was Y>（NH₄）2SO₄, the values of their48h LC50were Y213.41mg/L、（NH₄）2SO₄13890mg/L for contact filter paper test; the values of their14d LC50were Y1216.57mg/kg、（NH₄）2SO₄4293.53mg/kg for natural soil test. The results showed thatthe difference may depend on the biological mechanisms of Y、（NH₄）2SO₄composite toearthworms population.（NH₄）2SO₄at low and medium concentration, it could decrease thetoxicity of Y, and the toxicity of Y decreased with the decrease of （NH₄）2SO₄concentration, athigh （NH₄）2SO₄concentration, it could increase the toxicity of Y. Therefore, the component anddifferent concentration of combined pollutant are the significant factors to determine the toxicityof combined pollutant. Y、（NH₄）2SO₄single and composite on earthworms was low toxicity, butthey does too much that can cause death earthworms, and earthworms to （NH₄）2SO₄resistanceability is strong Y.The accumulation of single and combined （NH₄）2SO₄cases Y in earthworms was observedin the natural soil test. The accumulative quantity of Y in earthworms was relative to the quantityin the soil of Y and the exposure times. The more are the quantity in the soil of Y and theexposure times, the more are the accumulative quantity of Y in earthworms. When the earthworms exposed to single Y, the logarithm of the accumulative quantity of Y in earthwormsand that of Y quantity in the soil were linearly relative with the low cases:Cearthworm=124.69Ln（Csoil）－493.25，R2=0.9041. When the earthworms exposed to combined withY and （NH₄）2SO₄,（NH₄）2SO₄not only affect the accumulative quantity of Y in earthworms, butalso affected bioconcentration factors （BCF） of Y in earthworms. In a word,（NH₄）2SO₄at lowconcentration could increase the accumulative quantity of Y in earthworms, but at high（NH₄）2SO₄concentration, it could decrease the accumulative quantity ofY in earthworms.Y、（NH₄）2SO₄single and composite to three antioxidant enzymatic activities （SOD、CAT、POD） and malondialdehyde （MDA） content in earthworms was studied by the natural soil test.This paper’s objective was to investigate whether their catalase （CAT），superoxide dismutase（SOD） and peroxidase （POD） were influenced by Y and （NH₄）2SO₄at different concentrationsand exposure times. Adult earthworms were exposed to exposure times ranging from3to28days.The results showed that each change of Y and （NH₄）2SO₄in treatments was significantly differentcompared with the control at the same duration of exposure times. In the experiments ofcombined pollution, the activities of CAT, SOD and POD were weaker or more activate thansingle experiment, but MDAcontent was not shown the significant order all the experimentation.Therefore, Y and （NH₄）2SO₄give amount of earthworm caused toxicity affect in the test waseliminated synergy of SOD, CAT and POD, thus the earthworms’cell membrane has not receivedgreat damage. But compared with blank control group, the activities of SOD, CAT, POD and thecontent of MDA are subject to different influences on the body; all said the earthwormantioxidant defense system affected.