Microbial Remediation Of Combined Pollution Of Heavy Metal Cd²⁺ And Quinclorac

Compound pollution means the pollution caused by two or more pollutants which exist in the same environment medium,and it can be roughly divided into three types,such as compound pollution of heavy metals,compound pollution of organic,compound pollution of heavy metal and organic.The effect of compound pollution formed by a variety of pollutants has become a hot research topic in recent years.The effect of compound pollution of quinclorac and Cd²⁺ was studied in this paper.Quinclorac is a special herbicide for paddy weed,there is a large number of residues in the soil resulted from the extensive use widely wildly in tobacco-paddy rotating area,which can seriously affect the yield and quality of tobacco and other next-stubble crops.The heavy metal cadmium is widely used in electroplating industry and metallurgical industry,it can be selectively accumulate in liver and kidney after absorbed by humans and animals,which will seriously damage the renal tubular and causes a series of symptoms,such as proteinuria and glycosuria ultimately.Bacteria strain used in this paper was isolated from a pesticide plant sludge which is named C2,it not only degrades quinclorac but also gathers heavy metal of Cd²⁺,and we studied the features of C2 on degradation of quinclorac and enrichment of Cd²⁺ in this paper.The bacteria strain C2,which was isolated from a pesticide plant sludge takes quinclorac as sole carbon source and gather heavy metal Cd²⁺ at the same time.C2 was identified as Enterobacter ludwigii strain EN-119 C2 through the morphological characteristics,physiological and biochemical experiment and combined with the analysis of 16 S r DNA sequences.The results of C2 to degrade quinclorac and enrich Cd²⁺ showed that the optimum temperature of absorption and degradation is 25³5?,and the optimum p H is 6.0.The degradation rate of 50mg/L quinclorac by C2 was reached to 40.9% and the accumulation rate of 50mg/L Cd²⁺ reached to 92% on day 6.The compound remediation experiment result of quinclorac and Cd²⁺ in inorganic salt medium showed that quinclorac degradation rate and Cd²⁺ enrichment rate by strain C2 were both declined,meanwhile,the degrade rate of 50mg/L quinclorac and enrichment rate of 50mg/L Cd²⁺ were 31% and 60% respectively on 6th day.The result also indicated that when the concentration of quinclorac is constant,the rate of degradation and accumulation decrease significantly with the heavy metal concentration increases.The concentration of pollutants increase produces severe toxic effect,which can lead to reduced biomass and adsorption rate and degradation rate decreased consequently.To analyze the morphological and functional group changes of C2 before and after degradation and concentration by scanning electron microscopy?SEM?,the pictures got from SEM showed that there produced a lot of flocculent secretions after the degradation of quinclorac.These secretions may be polysaccharides,proteins and extracellular enzymes during the degradation,and strain C2 appear obvious deformation after absorbing heavy metal Cd²⁺.We also observed the characteristic functional groups of C2 before and after the degradation and enrichment through Fourier infrared spectrum method.The result showed that there was little change of the peak of strain C2 before and after the degradation and enrichment,just the absorption location and intensity of a few characteristic peaks were changed.This indicates that cell composition and whole structure don't change when degraded quinclorac and gathered heavy metal ions,only the COO-?-SO₃?C-O?C-Br?C-I on the surface of strain C2 were involved in the effect of degradation and enrichment.