| At present, the planting bases have already become a major agricultural production model in our country, but due to more human interference, the soil environment deteriorate, which makes a large number of harmful substances into the soil, resulting in declining soil quality, affecting crop growth and quality, and indirectly endangering human health. The experiment, soil from four platycodon grandiflorum planting bases in Shenyang (Unity Village, Daoyi town, PingLuo town, Zaohua town) chosen as research objects, firstly studied on soil nutrients, heavy metals content, organophosphorus pesticide residues and microbial diversity, which initially confirmed the soil quality status of Shenyang platycodon grandiflorum planting bases and explored the relation between the soil heavy metals, organophosphorus pesticide residues and soil microbial community, in order to provide a theoretical basis for soil ecological safety of platycodon grandiflorum planting bases and biological prevention and treatment of contaminated soil. Obtain the following results:(1) The macro-secondary-micro soil nutrients status was evaluated by general test (GT). The results showed that:four planting base soils belonged to non-saline acidic or neutral soil. Organic matter (17.6-31.3g/kg) was at middle-low level. Total N (1.34-2.76g/kg) and total P (0.49-0.94g/kg) were in moderate and suitable level. Total K (14.7-21.6g/kg) was at middling level for all soils. Available P (30.57-109.65mg/kg) was at rich level, but alkali-hydrolyzed N (51.57-112.36mg/kg) and available K (60.58-142.84mg/kg) were commonly deficiency; Available Fe、Mn、Cu、Zn、B were at middle-rich level. The relationship among the test results was studied. The results initially revealed that organic matter and total N had significantly positive correlation with available P、alkali-hydrolyzed N and total N had significant positive correlations at P<0.05level. The same correlations were also between alkali-hydrolyzed N, total P and available P. Total K and available K, only with available Zn、B had a positive correlation. Among trace elements, available Cu、Mn and Fe had significantly positive correlations at P<0.05level.(2) The heavy mental pollution of planting base soils was evaluated and elements relevance as well as principal component analysis were discussed. For all four bases, seven heavy metal elements [As (7.36-14.6mg/L), Cd (0.11-0.21mg/L), Cr (44-70mg/L), Pb (24.4-97.1mg/L), Hg (0.09-0.12mg/L), Ni (25.8-41.2mg/L), Cu (22.8-35.9mg/L), Zn (57.3-86.1mg/L)] had came up to pollution level, which in order was Pb> Hg> Zn> Ni=Cu> As> Cd> Cr. The fuzzy comprehensive assessment showed that Pingluo town and Unity village attained low-degree pollution, Daoyi town belonged to moderate pollution; Zaohua town was heavily polluted. In addition to Zaohua town belonging to middle ecosystem endanger class, other three bases were in strong degree of ecosystem endanger. Heavy metals Cd-As, Cd-Pb, Cu-Pb, Cu-Ni, Hg-Cr had significant correlations at P<0.05level. Zn-Cu had significant correlations at P<0.01level. Principal component analysis determined that the first principal factor was Cd、Pb、Cu and Zn, Ni and Hg were as the second principal factor. As and Cr belonged to the third main factor.(3) The available contents of heavy metals, the effective coefficient and correlation analysis showed that:the available contents of heavy metals among Zaohua town, Pingluo town and Unity village had no significant difference, which were significantly higher than Daoyi town. The effective coefficient of seven heavy metals was in order of Cd> Pb> Cu> Zn> Ni> As> Cr. Due to similar nature, the correlation coefficient of Fe-Ni、Cu-Fe and Zn-Cd reached significant or very significant level.(4) Distribution characteristics of heavy metal in the soil profile were detected and analyzed. The entire quantity content of Cu, Zn and Ni in the soil surface soil (5-15cm) were significantly greater than that in the middle-earth (15～35cm), while the content of subsoil (35～50cm) and middle-earth had little change.The content of As in the subsoil was mostly more than middle-earth. Pb in three soil samples showed a downward trend, Hg、Cd、Cr changed without regularity. Available heavy metals accumulated mainly in the surface soil and middle earth. (5) Organophosphorus pesticides residues in soil were detected by GC. With the common organophosphorus pesticides (phorate, dimethoate, parathion, diazinon, methyl parathion, chlorpyrifos, trichlorfon, dichlorvos, iprobenfos) detected, of which five kinds were found. The decreasing order of total residues amount was isofenphos (0.6177μg/g)> dimethoate (0.7672μg/g)> chlorpyrifos (0.3188μg/g)> diazinon (0.1234μg/g)> phorate (0.0523μg/g). Organicphosphorus pesticide residues in the soils Zaohua town, Daoyi town and Pingluo town ranged from0.3188μg/g to0.7421μg/g, while Unity village soil was the lowest (0.1822μg/g). According to the United States and Canada pesticide residue standards for soil, four planting base soils were subject to pesticide contamination. Organophosphorus pesticide residues in soil vertical distribution showed the same pattern, that is, organophosphorus pesticide residues in the middle-earth soil were the most.(6) Correlation between soil microbial community, diversity and the pollution factor were studied. The dominant bacteria in contaminated soil were identified by PCR technology. Of four bases, the bacteria are dominant species. The number of actinomycetes and heavy metal pollution showed obviously negative correlation. Microorganisms and organophosphorus pesticide residues in the total amount had negative correlation, in which the highest correlation coefficient was fungi. There were negative correlation between bacteria, fungi, actinomycetes diversity and the entire quantity of heavy mental elements, except As and Cd. However, correlation between available heavy metals and microorganisms state was reverse, of which Zn and fungi、bacteria had significant correlation at P<0.05level Correlation coefficients of organophosphorus pesticide residues and shannon index of bacteria, fungi and actinomycetes, respectively, were-0.849、-0.947、0.547. Influence of different pesticides on bacterial diversity varied. Through the DNA identification, four dominant bacteria were staphyococcus sp.、acinetobacterbaumannii、bacillus cereus and bacillus mycoides. |
PDF Full Text Request