| The phenomenon of compound contamination of soil with antibiotics and heavy metals is common.It is urgent for heavy metal contaminated soil to be repaired under the stress of antibiotics.In this study,flower plants like Tagetes patula L and Mirabilis jalapa L were used as test plants to carry out Cd-contaminated soil remediation work,and to investigate the effects of tetracycline antibiotics and the production of acid bacteria.The main results are as follows:1.Alkaline cadmium contaminated soil can have a toxic effect on Tagetes patula L and reduce its biomass.Compared with the control group,the T3(30 mg/kg)treatment had the largest decrease in stem and leaf biomass,with a decrease of 27.4% and 31.2%,respectively.In different concentration of Cd contaminated soil,Tagetes patula L showed better cadmium enrichment and metastasis capacity,bioconcentration factor and translocation factor were greater than 2,and the bioconcentration factor reached 3.18(T1 treatment).Heavy metal cadmium is concentrated in the ground.With the increase of cadmium concentration in the soil,the toxic effect of Tagetes patula L increased and the bioconcentration factor decreased.In field experiments,the bioconcentration factor of Tagetes patula L was 1.1,and the transfer coefficient was 1.66.Although it was smaller than tthat in the pot experiment,the biomass and cadmium accumulation amount was much larger than that of the pot experiment.It can be used as a remediation plant for cadmium-contaminated soil.The root of Mirabilis jalapa L showed better cadmium tolerance,The higher the cadmium concentration,the greater the biomass of the roots.The T3(30 mg/kg)treatment maximized the root biomass,which was 2.38 g/pot.While the growth of the ground was inhibited by cadmium.In the experiment,the cadmium bioconcentration factor of Mirabilis jalapa L increased with the increase of cadmium concentration,but all of them were less than 1,and there is no significant difference.It did not have the conditions for cadmium superenrichment plant.2.Acid-producing bacteria can increase the content of oxalic acid and acetic acid in soil,and at the same time can increase the biomass of Tagetes patula L,but it will be affected by the concentration of cadmium in the soil.The greater the concentration of cadmium,the less the biomass of Tagetes patula L increases.The BT0(0 mg/kg)treatment had the largest increase in stem biomass,which was 10.2%.The BT1(5 mg/kg)treatment had the largest increment of leaf biomass,which increased by 33.0%.When the cadmium concentration in soil was BT1(5 mg/kg)and BT2(15 mg/kg),the acid-producing bacteria could enhance the cadmium accumulation ability of Tagetes patula L and enhance the repair effect,and cadmium accumulation above ground increased by 39.8% and 18.5%,respectively.When the cadmium concentration was BT3(30 mg/kg),acid-producing bacteria reduced the ability of Tagetes patula L to enrich cadmium,and reduced the repair effect.When the cadmium concentration was BT1(5 mg/kg),the acid-producing bacteria will promote the growth of Mirabilis jalapa L.The root,stem and leaf biomass increased by 2.8%,20.4%,and 83.5%,respectively.Under this condition,acid-producing bacteria increase the ability of extracting cadmium of Mirabilis jalapa L and accumulation of cadmium on the ground was significantly increased by 39.8%,which enhanced the repair effect.When cadmium concentration is BT2(15 mg/kg)and BT3(30 mg/kg),the acid-producing bacteria can inhibit the growth of Mirabilis jalapa L and it has a significant inhibitory effect on the roots,and and root biomass decreased by 62.4% and 55.7%,respectively.Under these conditions,acid-producing bacteria reduced the extraction ability of the heavy metal cadmium。The accumulation of cadmium on the aerial parts decreased by 32.3% and 25.0%,respectively,which reduced the recovery effect.3.In cadmium-tetracycline contaminated soils,tetracycline enhanced the toxic effects on Tagetes patula L and Mirabilis jalapa L and reduced biomass of them.The greater the concentration of tetracycline,the greater the decrease in biomass of Tagetes patula L,and the aboveground biomass was reduced from 5.29 g/pot treated with CK1(0 mg/kg)to 4.12 g/pot treated with B3(5 mg/kg).Under different concentrations of tetracycline treatment,there was a significant difference(p<0.05 LSD test)in biomass of roots and leaves of Mirabilis jalapa L.Tetracycline has different effects on phytoremediation.For Tagetes patula L,tetracycline treatment with B1(0.5 mg/kg)can can enhance the enrichment ability and transport capacity of Tagetes patula L to cadmium,and improve the efficiency of the restoration of the cadmium polluted soil.Under these conditions,the bioconcentration factor,translocation factor,and accumulation of cadmium in shoots reached the maximum values of 3.26,2.65,and 238.32 μg/pot,respectively.Tetracycline treatment with B2(2 mg/kg)can can reduce the cadmium-enrichment ability of Tagetes patula L,and reduce transport capacity and repair efficiency.Under these conditions,the bioconcentration factor,translocation factor,and accumulation of cadmium in shoots reached the minimum values of 2.17,1.59,and 136.48 μg/pot,respectively.Tetracycline treatment with B3(5 mg/kg)can enhance the enrichment capacity of Tagetes patula L to cadmium,but reduce the transport capacity and repair efficiency.For Mirabilis jalapa L,tetracycline stress can increase the cadmium accumulation ability of it.The higher the concentration,the greater the bioconcentration factor of Mirabilis jalapa L,and it reached 1.25 under the treatment of B3(5 mg/kg).Bdue to the reduction of biomass,the cadmium accumulation in the aboveground parts of Mirabilis jalapa L under the treatments of B1(0.5 mg/kg)and B2(2 mg/kg)decreased by 11.7% and 3.7%,respectively,which reduced the recovery efficiency.The accumulation of cadmium in the aboveground parts increased by 17.7% under B3(5 mg/kg)treatment,which increased the recovery efficiency of Mirabilis jalapa L.4.Inoculation of acid-producing bacteria in tetracycline-cadmium compound contaminated soil will increase the content of acetic acid and oxalic acid.Treatment of tetracycline with BB1(tetracycline: 0.5 mg/kg,bacteria)enhanced the growth promoting effect of acid-producing bacteria on stem and leaf of Tagetes patula L and completely inhibited the growth promoting effect on roots,enhanced the reinforcement of acid-producing bacteria on cadmium enrichment and transport capacity and repair effect of Tagetes patula L.The promoting effect of acid bacteria on the growth of Tagetes patula L was inhibited by tetracycline with BB1(tetracycline: 2 mg/kg,bacteria)and BB1(tetracycline: 5 mg/kg,bacteria),which inhibited the enhancing effect of acid-producing bacteria on cadmium-enrichment ability and transport capacity of Tagetes patula L,and reduced the repair efficiency.Tetracycline alleviated the inhibitory effect of acid-producing bacteria on the growth of root of Mirabilis jalapa L,completely inhibited the growth-promoting effect of acid-producing bacteria on the growth of stem of Mirabilis jalapa L,and enhanced the inhibitory effect of acid-producing bacteria on the growth of leaf.Different concentrations of tetracycline can alleviate or even eliminate the inhibitory effect of acid-producing bacteria on the cadmium absorption capacity of Mirabilis jalapa L,and improve the extraction ability and repair efficiency of it.5.In cadmium-contaminated soil,whether or not adding tetracycline or inoculating acid-producing bacteria,the aboveground biomass and enrichment coefficient of Tagetes patula L were greater than that of Mirabilis jalapa L.The repairing effect of Tagetes patula L on cadmium-contaminated soil was better than that of Mirabilis jalapa L,and It is more suitable as a remediation plant for cadmium-tetracycline compound contaminated soil. |
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