Effect Of Biochar With Micro-fertilizer On Remediation Of Heavy Metal Pollution In Nasturtium Officinale R.Br. Metals

The heavy metal pollution of soil and water caused by wastewater irrigation practices,irrational use of pesticides and fertilizers has gradually become an environmental issue that threatens the development of vegetables in China and needs to be solved urgently.The biochar has been widely used for the treatment of heavy metals in water and improved soil pollution due to its ability to adsorb heavy metals and improve soil structure.Micro-fertilizer are also considered to promote the growth of vegetables and impede heavy metal pollution.In this paper,soil simulation experiments?soil culture and pot experiment were used to study the effects of biochar-micro fertilizer on soil physicochemical properties,heavy metal availability,and the absorption and accumulation of heavy metals by Nasturtium officinale R.Br.,in order to clarify the effects of different types of biochar-micro fertilizers on the pollution of heavy metals in plant,and explore the mechanism of biochar-micro fertilizers in relieving heavy metal pollution in vegetable.The experimental results are as follows: 1?The influence of biochar-Micro fertilizer on Physicochemical Properties and available heavy metals content in vegetable soilIdoor simulation experiment was conducted by adding Pennisetum hydridum biochar,coffee grounds biochar,peanut shell biochar and micro-fertilizer(iron fertilizer,manganese fertilizer and silicon fertilizer)in heavy metal contaminated soil,the five heavy metal available concentrations and other soil physical and chemical indicators were determined at 14 th and 28 th day.The results showed that:(1)Adding biochar �micro fertilizer,the contents of soil pH,organic matter,and ammonium nitrogen were significantly higher than the control group.(2)The heavy metal available concentrations in soil added with biochar or micro-fertilizer were less than that of the control group,and there were significant differences among these different treatments.When the soil was applied with a single addtive,both Pennisetum hydridum biochar and silicon fertilizer showed good passivation.When the soil was applied with compound additives,adding Pennisetum hydridum biochar with iron fertilizer showed good passivation,the concentrations of available Cu,Pb,and Cd decreased by 32.94%,31.26%,and 21.21% respectively at 14 th day,and the concentration of available Zn also decreased by 6.82%,but its immobilization effect on soil Ni was not obvious.When adding coffee grounds biochar with iron fertilizer,the concentrations of available Ni and Zn also decreased by 22.64% and 10.35% respectively at 14 th day,its passivation effect was remarkable.at 28 th day,peanut shell biochar with iron fertilizer had the best passivation,the concentrations of available Cu decreased by 49.06%.coffee grounds biochar with silicon fertilizer had the best passivation,the concentrations of available Ni,Zn decreased by 23.73% and 9.72% respectively.2?Effect of biochar-iron fertilizer on remediation of heavy metal pollution in Nasturtium officinale R.Br.and its mechanismBased on the results of the previous experiment,Pennisetum hydridum biochar and coffee grounds biochar with iron fertilizer were used as mixed materials to study their effects on the growth,quality,and absorption of heavy metals Cd and Pb,and soil physicochemical properties.The results showed that:(1)Biochar-iron fertilizer can promote the growth of plant.The plant height of the first crop of Nasturtium officinale R.Br.after impregnation with Pennisetum hydridum biochar-iron fertilizer and coffee grounds biochar-iron fertilizer were significantly higher than that of the control group,and its amplitude were 11.6% and 13.9% respectively.In the second season,the plant height,the dry weight of the above ground and roots of Nasturtium officinale R.Br.treated with Pennisetum hydridum biochar-iron fertilizer were significantly higher than those of the control group,the amplitude was 30.8%,33.2%,and 23.7%,respectively.The content of soluble sugar and soluble protein of the first season after adding Pennisetum hydridum biochar-iron fertilizer increased by 25.1% and 11.1% compared with the control group.(2)The application of biochar-iron fertilizer can effectively reduce the absorption of Cd and Pb by Nasturtium officinale R.Br.In the first season,adding Pennisetum hydridum biochar-iron fertilizer and coffee grounds biochar-iron fertilizer,the Cd concentration in aboveground part was lower by 42.9% and 38.1% than that of the control group,respectively,the content of Pb is reduced by 68.2% and 62.5%,respectively.In the second season,the contents of Cd in aboveground part of plant after adding two kinds of biochar-iron fertilizer were lower than that of the control group by 20.0%,and the content of Pb was reduced by 58.4% and 48.8%,respectively.(3)Adding biochar-iron fertilizer can significantly increase soil pH and organic matter content,increase soil urease activity,and change the content of ammonium nitrogen,available phosphorus and available potassium in soil.Adding biochar-iron fertilizer increased oxidizable and residual form Cd and Pb content in the soil while reducing the exchangeable and reducible Cd,Pb content.The content of exchangeable form Cd,Pb in soil increased by 8.9%-51.2% and 0.8%-70.2% respectively,compared with CK.The content of reducible form Cd,Pb in soil increased by 37.5%-56.9% and 3.6%-79.2% respectively.3?Effect of biochar-iron fertilizer on alleviating heavy metal pollution of Nasturtium officinale R.Br.in water(1)Effect of biochar-iron fertilizer on reducing Pb and Cu pollution of Nasturtium officinale R.Br.under different pollution levelsUsing hydroponic experiments,the effects on the growth and absorption of Pb and Cu of Nasturtium officinale R.Br.were studied under different concentrations of Pb and Cu.The experimental results are as follows:The inhibition of Pb and Cu on the growth of Nasturtium officinale R.Br.could be alleviated by adding Pennisetum hydridum biochar-iron fertilizer in water.Compared with the untreated group,Pb concentration was 2,4,6,8,10 mg/L for each group.Dry weights increased by 0.2% ? 39.7% ? 13.5% ? 34.5% and 108.6%,respectively.When the Cu concentration was 10,20,50,100,and 200 mg/L,the dry weight of each group increased by 2.4% ? 7.2% ? 58.2% ? 57.5% and 93.0%,respectively.The Pb and Cu contents in the aboveground part were significantly reduced by adding Pennisetum hydridum biochar-iron fertilizer.Compared with the non-addition group,when Pb concentration was 2-10 mg/L,the reduction of Pb content in aboveground part was.8.4% to 51%,the Cu content in aboveground part was reduced by 28.5%-51.2% under the Cu concentration of 10-200mg/L.(2)Effects of two types of biochar and their extracts with iron fertilizers on reducing pb contamination of Nasturtium officinale R.Br.Treatment of Pennisetum hydridum biochar,coffee biochar extract,coffee biochar,Pennisetum hydridum biochar-iron fertilizer and coffee biochar-iron fertilizer can significantly improve the plant height,root length and aboveground part of dry weight.Whether adding biochar or biocarbon extract,the Pb content in shoot and root of Nasturtium officinale R.Br.could be significantly reduced,Pennisetum hydridum biochar-iron fertilizer is more obvious treatment,decreased by 82%.and 85%.To sum up,the results indicated that Pennisetum hydridum biochar-iron fertilizer can reduce the heavy metal absorption and accumulation of heavy metals and reduce the harm of heavy metal pollution by changing physical and chemical properties,reducing heavy metal content in water,and changing heavy metal forms in soils to reduce bioavailability.