| In the intensive farming livestock,a large number of additives are added to the poultry feed.Due to the high content of heavy metals in the additives,the content of feces and organic fertilizers is excessively severe.After a large number of applications,the soil and crops will be polluted.When harmful metal elements in crops exceed a certain concentration,human health will be seriously affected.In present study,the characteristics of heavy metals in organic fertilizers in different provinces and cities of Huang-Huai-Hai were investigated and then explored their potential environmental risks.A field experiments was conducted to study the effects of organic fertilizers on soil heavy metals?total and available content?and fertility?nitrogen,phosphorus,potassium and organic matter?,as well as the influence of heavy metal accumulation and quality of vegetables,the main results are as follows:?1?120 kinds of chicken manure organic fertilizer samples from 5 provinces and 2 cities in Huang-Huai-Hai region were collected to investigate heavy metal content,fractionation,and environmental risk through toxicity characteristic leaching procedure.The results showed that content of heavy metals in chicken manure organic fertilizer varied greatly,which showed Zn>Cu>Pb>As>Cd.When compared with the standard of organic manure,the ratio of Cd,As and Pb exceeded the standard was 6.7%,47.05%and 14.28%.Moreover,the contents of heavy metals in different provinces were significantly different.The amount of Cd and Zn in organic manure fertilizer were mainly Fe and Mn oxide-bound fraction,accounting for 37.3%and 43.79%,respectively.However,the proportion of residual fraction of Pb,organically bound fraction of Cu and exchangeable form of As were higher.The contents of TCLP-Zn,-Cu,-Cd,-Pb and-As in organic manures were 41.11,33.3,0.07,1.25 and 0.21 mg·kg-1,respectively,and the number of Zn and Pb in organic manure exceeded the standard was 6 and 5,mainly located in Hebei and Jiangsu provinces.There was a significant correlation between total content of Zn,Cu,Cd and As in organic manure and content of TCLP?P<0.05?.According to the annual manure application rate of chicken manure of 15 t·hm-2,the safety application years of chicken manure was Henan>Tianjin>Anhui=Shandong=Jiangsu>Hebei>Beijin?2?In the field experiments,after applying two kinds of chicken manure organic fertilizers?L1 and L2?,the content of total nitrogen,alkaline dissolved nitrogen,total phosphorus,available phosphorus,and total potassium content was 1.79-3.81 g·kg-1,132.37-283.40 mg·kg-1,2.21-4.76mg·kg-1,162.23-583.25 mg·kg-1,and 24.73-27.66 g·kg-1,respectively.The amount of soil organic matter,total nitrogen,alkali-hydrolyzable nitrogen,total phosphorus,and available phosphorus increased with increasing the content of fertilizer.There was no significant difference in total potassium in the soil,but there was a significant positive correlation between fertilizer application and total nitrogen,available phosphorus,and alkali-hydrolysis nitrogen?P<0.05?,and the application amount was positively correlated with total phosphorus,available phosphorus,and organic matter.Fertilization could not only increased soil fertility,but also improved soil physical and chemical properties.?3?Under field experiments,after applying two kinds of chicken manure organic fertilizers?L1 and L2?,the fresh weight of Chinese cabbage increased first and then decreased with the increase of the application of organic manure.The fresh weight of vegetables was highest at T1treatment,being 74.62 and 55.05 g,respectively,but the minimum of 31.78 and 26.01 g fresh weight was got under T8 treatments,respectively.The amount of soluble sugar increased with the increase of organic fertilizer application,and increased by 11.00%-73.20%and 20.99%-144.32%,respectively,when compared with CK.The contents of Zn,Cu,Cd,and As in the cabbage increased with the increase of application rate of organic manure,and reached the highest value in the T8 treatment.The highest content of heavy metals in Chinese cabbage under the treatment of L1 and L2 was 94.28 and 99.67 mg·kg-1 for Zn,respectively,21.82 and 18.21 mg·kg-1 for Cu,respectively,1.068 and 0.938 mg·kg-1 for Cd,respectively,and 0.055 and 0.059 mg·kg-1 for As,respectively.The contents of heavy metals Zn,Cd,and As in soil increased with the increase of organic fertilizer application?L1 and L2?,and the highest contents,Cd and As in soil were 265.54and 245.51 mg·kg-1,respectively,for Zn,2.93 and 2.87 mg·kg-1,respectively,for Cd,and 33.70and 40.29 mg·kg-1,respectively,for As.It was found that TCLP-Zn,-Cu,and-As increased significantly with increasing fertilizer levels,but the contents of TCLP-Cd and-Pb decreased significantly with increasing fertilizer levels.According to the National Standard for the Safety of Heavy Metals in Vegetables?GB18406.1-2001?,the contents of Cd and Pb in Chinese cabbage exceeded the standard.According to Soil Environmental Quality Standard?GB15618-1995?,the Cd content was higher the third-grade standard.As content in soils under T8 treatment of the organic fertilizer L1 exceeds the third-level standard,and while it exceeded three-level standard of soils under the addition of T4 and T8 of organic fertilizer L2. |
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