| In recent decades,the soil contamination has increasingly become more complex and diversified due to the fast development of industry and agriculture in China.The co-contamination of heavy metals and phthalic acid esters has been particularly prominent,and would lead to serious environmental consequences.Characterized by the strong mobility nature,the heavy metals can enter the human body system through the food chain and thereby threaten human health.Phthalic acid esters(PAEs)are the most commonly used plasticizer compounds in the world,which are widely existed in the agricultural plastic film,and the PAEs will gradually release into the soil over time.Consequently,the co-contamination of the PAEs and the heavy metals ready accumulated in soils raised serious environmental risk.Biochar is a carbon-rich solid material derived from thermal decomposition process known as pyrolysis of waste agricultural and forest residual biomass.Due to porous structure and abundant surface functional group,biochar can effectively adsorb heavy metals and organic compounds in the soil,it has become a new bio-adsorbent for soil amendments.Therefore,a pot experiment was conducted using Brassica chinensis L.as an bio-indicator plant to investigate the effect of biochar application on the bioavailability of cadmium(Cd)and di-(2-ethylhexyl)phthalate(DEHP)and plant growth.The feedstocks of biochar were derived from dead pigs and Platanus orientalis Linn.branches.These were applied at five rates(0,0.5,1,2,and 4%)to two soils with different organic carbon contents(higher organic carbon HOC: 3.08% and lower organic carbon LOC: 0.75%).The aim of this study was to explore the effects of biochar application on soil fertility,contaminant bioavailability,soil enzyme activity,plant growth and nutrients absorption.The main results are as following.1.The application of pig and P.orientalis biochar significantly(P<0.05)increased soil pH,electron conductivity,cation exchange capacity and organic carbon content,especially in the LOC soil.Results showed that increasing biochar application rates decreased DTPA-extractable Cd concentrations in soils and increased the residual DEHP concentrations in soils.Biochar application also reduced the plant uptake of both Cd and DEHP from co-contaminated soils,the maximum reduction was observed in 2% pig biochar-treated LOC soil,decreased by 92.7%(Cd)and 52.0%(DEHP).Application of biochar enhanced the soil urease,sucrase and catalase activities,but suppressed the acid phosphatase activity.In addition,the malondialdehyde,proline and soluble sugars concentrations in the plant shoot were decreased after biochar application.The effect of pig biochar was better than P.orientalis biochar.in reducing the bioavailability of contaminants and improving the quality of Brassica chinensis L..2.4% pig biochar application inhibited the seed germination of Brassica chinensis L..Except for the 4% pig biochar treatments,the biomass and height of plant were significantly(P<0.05)enhanced after biochar amendment,and the pig biochar had a more prominent influence.Application of biochar significantly(P<0.05)increased the soil available potassium and phosphorus concentrations,but decreased the available nitrogen concentration.Biochar application increased the concentrations of potassium,phosphorus,nitrogen,calcium(Ca),magnesium(Mg)and sodium(Na)uptake by plant shoots,and reduced the manganese(Mn)concentration taken up.In conclusion,pig biochar and P.orientalis biochar could enhance soil adsorption capacity of Cd and DEHP and reduce their bioavailability,promote the plant nutrients absorption,improve the soil quality and crop yield.Pig biochar had greater potential for improving soil and plant quality than P.orientalis biochar due to better properties(such as surface alkalinity,nutrients contents,and ash content).Organic carbon content was another important factor influencing the bioavailability of Cd and DEHP,the biochar application was more effective in the soil with lower organic carbon content. |
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