Study On Transfer And Residue Of Feed Additives In Soils And Vegetables

Pig manure is rich in organic matter,which can provide crops enough nutrients to meet their needs of growth.Therefore,pig manure (including the biogas residues) as has been the typical of the green organic fertilizer.In recent years,the rapid development of agricultural economic cycle(breeding pigs-pig manure-organic fertilizer-crops) regards the pig manure as a substitute for chemical fertilizers.However, the feed based on modern animal husbandry industry contains a variety of feed additives,including a variety of antibiotics and heavy metals,and most of them are excreted with feces.Some antibiotics and heavy metals are relatively stable,refractory,strong toxicity and with accumulation effect in soil.As a result,whether the application of pig manure (especially use in long-term at a certain region) will affect the microbial flora,soil quality and ultimately jeopardize the safety of agricultural products,become the focus of ecotoxicology.This paper studied the residue and transfer of feed additives in soils and vegetables in three typical pig farms in Zhejiang.The main results are summarized as follows:1.Assessment of residues of feed additives in pig manureAccording to the data of pig farms in Zhejiang,and in the light of environmental impact assessment method,we analyze the pig excretions, and emphatic-cally in the transfer of feed additives in food chain.The results showed the amount of Cu,Zn,As,and Mn in pig manure discharged into the environment of Yiwu pig farm were 639.54kg/a, 1420.67kg/a,72.83kg/a and 203.49kg/a,and that for organic fertilizer directly into the soil were up to the amount of 303.14kg/a,673.40kg/a, 34.52kg/a and 96.37kg/a;the amount of Cu,Zn,As,and Mn in pig manure discharged into the environ-ment of Yuyao pig farm were 496.28kg/a,l139.51kg/a,25.60kg/a and 148.88kg/a,and that for organic fertilizer directly into the soil were up to the amount of 136.95kg/a, 314.50kg/a,7.07kg/a and 41.04kg/a;the amount of Cu,Zn,As,and Mn in pig manure discharged into the environment of Xiaoshan pig farm were 558.14kg/a,1427.50kg/a,69.91kg/a and 186.05kg/a,and that for organic fertilizer directly into the soil were up to the amount of 183.07kg/a,468.22kg/a,22.93kg/a and 61.65kg/a.The volume of urine of three pig farms were 6906t/a,5997t/a and 7545t/a respectively,and the emission of NH₃ and H₂S were NH₃ 6.02t/a,H₂S 1.19t/a;NH₃ 5.18t/a, H₂S 1.02t/a;and NH₃ 6.57t/a,H₂S 1.29t/a respectively. 2.The impact of pig manure to soil microorganismThe content of bacteria,fungi and actinomycetes in experimental soils of Yiwu were 319.11%,205.19%and 155.61%higher than that of the control groups(p＜0.05);the content of bacteria,fungi and actinomycetes in experimental soils of Yuyao were 144.93%,325.21% and 128.11%higher than that of the control groups(p＜0.05);the content of bacteria,fungi and actinomycetes in experimental soils of Xiaoshan were 71.40%,85.26%and 42.90%higher than that of the control groups (p＜0.05).While the content of Azotobacter and Rhizobium in experimental soils of Yiwu were 56.52%and 39.63%lower than the control groups(P＜0.05);the content of Rhizobium in experimental soils of Yuyao was 24.89%lower than the control groups(P＜0.05).The results suggest that the total amount of soil microorganisms increased with the use of pig manure,but the content of Azotobacter and Rhizobium which are very important to crops were significantly reduced.3.Residue of heavy metals of pig manure(feed)in soils and vegetablesThe content of Cu,Zn,As,Cd,Pb and Mn in experimental soils of Yiwu were 928.03%,441.69%,106.72%,69.14%,27.44%and 27.52% higher than that of the control groups(p＜0.05);and were 311.54%, 259.93%,117.07%,219.05%,52.82%and 129.65%higher than that of the control groups(p＜0.05) of Yuyao;and were 1040.26%,332.73%, 96.10%,136.84%,82.90%and 57.19%higher than that of the control groups(p＜0.05) of Xiaoshan.The over standard rate of Cu,Zn and Cd in Yiwu experimental soils were 133.98%,75.91%and 356.67%;and were 27.62%,52.05%and 123.33%in Yuyao;the over standard rate of Zn and Cd in Xiaoshan experimental soils were 14.88%and 50.00%.There was no found of over standard in control groups except Cd in Yiwu.The content of Cu,Zn,Cd,Pb and Mn of experimental vegetables were about 2-3 times higher than control groups,the content of Zn,Cd and Pb in the underground part of leek,celery and pakchoi in experimental groups were all over standard.The content of As could not be detected in control groups,but were all detected in experimental groups.In addition,the content of heavy metals in underground part of vegetables was all higher than the overground part.4.Residue of antibiotics of pig manure(feed) in soils and vegetablesAll the experimental soils were detected oxytetracycline(OTC) and chlortetracycline(CTC).The CTC content of Yiwu experimental soil and the OTC content of Xiaoshan experimental group were 1.5057 mg/kg and 1.1449mg/kg.OTC and CTC could not be detected in control groups, except Xiaoshan.OTC and CTC could be detected in underground part of experimental vegetables,while could not be detected in control groups.It shows that OTC and CTC can be accumulated in the soil,and also can be accumulated(part of underground sections) in vegetables with the time.5.Pollution assessment and transfer regularity in food chain of feed additivesUsing single factor pollution index and Nemerow integrated pollution index to assess the soils and vegetables,the results showed the Nemerow integrated pollution index of experimental soils were 3.52, 1.753 and 1.217 respectively,which significantly higher than control groups(1.990,0.576 and 0.264).The Nemerow integrated pollution index of experimental vegetables were significantly higher than control groups. Except the pakchoi in Yuyao and all the radishes,all other experimental vegetables were contaminated.Cd has the highest enrichment coefficient and Zn,Mn and Pb have higher mobility of these three vegetables.The underground part of leek in Yiwu has the highest enrichment coefficient of OTC and CTC,which were 0.114 and 0.083 respectively.Taking Xiaoshan pig farms as an example,if 1500 tons of fresh manure is used to plant leeks,the content of Cu,Zn,As and Mn which finally into the overground part of leek are 1.7035kg,7.1149kg,0.2735 and 0.3368kg;and the content of OTC that into the underground part of leek is 3.6553kg.