| Morels are one of China’s precious edible fungi for both medicine and food,and it is also the main edible fungus product exported by China,but with the discharge of industrial waste and the excessive input of agricultural products in the agricultural production process,the heavy metal pollution in the soil is increasingly aggravated.The problem of excessive heavy metals in morels has seriously affected the quality safety of morel products and human health,so how to effectively repair the matrix soil contaminated by heavy metals and reduce the absorption of heavy metals in the soil by morels has become an urgent problem to be solved.In this study,the effects of morels on soil physicochemical properties,changes in heavy metal content in soil,occurrence form of heavy metals,morels on soil heavy metal enrichment and morel quality were explored by applying calcium carbonate(T),calcium dihydrogen phosphate(L),PAM(J)and biochar(S)to morel substrate soil,in order to provide a theoretical basis for improving soil heavy metal pollution,reducing the content of heavy metals in morels and improving the quality of morels.The results of the main studies are as follows:(1)After adding amendments to the soil,the soil pH increased to a maximum value of 7.36 when calcium carbonate was applied at 0.5%,and the highest conductivity and organic matter were found when biochar was applied at 0.5%.The content of Pb in the substrate soil of the study area exceeded the background value of Guizhou soil,and the content of Cd was higher than the national standard screening value.The effect of adding amendments on Pb,Cd,As,Hg,Zn and Cu in the soil was different,among which,in the S2 treatment group,the contents of Cd,Zn,As and Cu in the soil were the lowest,and the reduction of Pb in the J1 treatment group was the lowest;the improvement effect of the four amendments on Hg was not obvious.(2)After adding the amendment,the content of the exchange state of Pb,Zn,Cu and Cd in the soil reached the minimum values in the L3,S1,J2 and L3 treatment groups,with a reduction of 50.96%,68.61%,22.97%and 57.38% respectively;the content of the carbonate bound state reached the minimum values in the L3,L1,T2 and L1 treatment groups,with a reduction of 61.28%,96.85%,12.91% and 35.29%;the content of Fe-Mn oxidation state reached the minimum value in S3,L3,S3 and J3 treatment groups,with a reduction of 31.89%,29.41%,21.42% and 19%respectively;the content of organic state reached the minimum value in S1,T2,T3 and L1 treatment groups,with a reduction of 30.77%,54.35%,29.09%,45.72%;the residue content reached the maximum value in L3,L2,L1,L3 treatment groups,increasing by 5.65%,13.3%,16.77%,20.39% respectively.The correlation analysis between soil pH and chemical forms of soil heavy metals showed that the increase of soil pH could reduce the effectiveness of soil heavy metals.(3)The content of Cd and As in morel mushrooms exceeded the standard.After the addition of improver,the contents of Cd,As and Cu in morel mushroom decreased and were lower than those in the control group,with the minimum values in S3,J3 and S2 treatment groups,and the rates of decrease were 61.92%,73.41% and 45.22% respectively;the contents of Pb,Hg and Zn were the minimum values in T3,L1 and T3 treatment groups,and the rates of decrease were 58.63%,74% and9.91%.(4)After the addition of improvers,the order of enrichment of heavy metals by morel mushrooms is: Cd > Hg > Cu > Zn > As > Pb.Among the four improvers,the weakest enrichment of Pb by morel mushrooms is T3,L2,J3 and S3,with a reduction rate of 56.65%,33.01%,37.93% and22.66% respectively;the enrichment of Cd by morel mushrooms is The weakest treatment groups were T3,L3,J1 and S3,with the reduction rates of 21.55%,28.04%,21.62% and 60.72% respectively;the weakest treatment groups of As enrichment ability of rambutan were T2,L2,J3 and S2,with the reduction rates of 70.86%,55.52%,73.01% and 54.91%respectively;the weakest enrichment ability of rambutan for Hg The treatment groups with the weakest enrichment of Hg were T1,L2,J1 and S2,with 73.09%,79.06%,40.97% and 60.14% respectively;the treatment groups with the weakest enrichment of Zn were T3,L2,J1 and S2,with 8.26%,6.51%,7.99% and 2.21% respectively;the treatment groups with the weakest enrichment of Cu were T3,L1,J1 and S2,with reduction rates of 34.7%,37.83%,20.14% and 42.13% respectively.(5)In the treatment group with the addition of calcium carbonate and PAM,Pb,Cd and Zn in morel mushrooms were significantly correlated with the exchange state of the corresponding heavy metals in the soil(P < 0.05),while the content of Cu in morel mushrooms was positively correlated with the exchange state content of Cu but not significantly,indicating that the effective state content of heavy metals in the soil is the main factor affecting the content of heavy metals in morel mushrooms;in the treatment group with the addition of calcium dihydrogen phosphate and biochar In the treatment group with the addition of calcium dihydrogen phosphate and biochar,the Cd and Zn in the morel mushroom and the exchange state content of Cd and Zn in the soil were significantly positively correlated(P < 0.05),while the Pb and Cu in the morel mushroom and the exchange state content of Pb and Cu in the soil were positively correlated but not significantly,indicating that the enrichment capacity of the morel mushroom for heavy metals in the soil was related to the effective state content of heavy metals,but also related to the characteristics of the morel mushroom itself.(6)The addition of improvers increased the crude protein content in the morels by 2.33%～4.09%,3.56%～8.29%,3.07%～4.58%,and6.14%～10.54% respectively,among which,the S2 treatment group was the most effective in enhancing the crude protein content in morels.The application of three improvers,calcium carbonate,PAM,and biochar,at high concentrations,significantly increased the content of 17 amino acids compared with the control group,and the content of all amino acids,except proline,was significantly increased when calcium dihydrogen phosphate was applied. |
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