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Migration, Accumulation and Control of the Cu and Zn in the Pig Manure-Earthworm System

Author: LiLingXiangYu
Tutor: TianGuangMing
School: Zhejiang University
Course: Environmental Engineering
Keywords: pig manure Cu Zn earthworm migration and accumulation control
CLC: X174
Type: Master's thesis
Year: 2010
Downloads: 158
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Abstract

The intensive pig farming has developed rapidly in recent two decades.As a consequence,the amount of pig manure increases significantly and its component varies a lot compared with that before.Pig manure is moderately to heaily polluted with heavy metals（e.g.Cu and Zn）.This is caused by feed additives overuse（largely exceeds physiological requirement levels for waine disease control and weight improvement）.The growth of the swine industry has caused a surplus of manure to be disposed of in comparison to the areas available for it to be spread.As a result,there are a lot of environmental problems such as water,air and soil pollution as well as safety of agricultural food.Additionally,the great deal of pig manure restricts the sustainable development for pig production.A new approach of pig manure treatment,pig manure-earthworm system（i.e., breeding earthworms with pig manure）,has been developed in recent years.By this way,the pig maure is reclaimed and disposed,and protein-rich earthworm biomass, the perfect feed for livestock,is obtained.The earthworms play an important role in the pig manure-earthworm system.Based on the spot check,we investigate the migration and accumulation of Cu and Zn in pig manure-earthworm system in the greenhouse,and the possibility of reducing the risk of heavy metals accumulated in earthworms and earthworm cast by adding additives such as peat,phosphate rock and fly ash.The study was done as follow:1.Study on the accumulaltion of Cu and Zn in earthworm（Eisenia fetida） by spot check.Pig manure samples and earthworms were collected from four different greenhouses located in Yuhang country,Zhejiang Province,China.The four greenhouses selected were Site 1（S1）,Site 2（S2）,Site 3（S3） and Site 4（S4）, respectively.The study was investigated whether and to what extent E.fetida accumulated Cu and Zn in the pig manure-earthworm system,and the relationship between bioavailability of Cu and Zn in pig manure and their bioaccumulation in E. fetida.It was found that E.fetida did accumulate Cu and Zn although the concentrations of Zn in earthworm were between 5.92 and 7.34 times higher than those of Cu;the concentrations of Cu in E.fetida were between 24.22 and 81.44 mg kg^-1,and the concentrations of Zn in E.fetida were between 177.85 and 481.79 kg mg^-1.Based on the bioaccumulation factor（BAF） in earthworm E.fetida,the BAFs of Cu were between 0.030 and 0.099,whereas those of Zn were between 0.318 and 0.738.Significant relationships were found between bioavailability of heavy metals in pig manure and their bioaccumulation in E.fetida.The variation in the Cu concentration of E.fetida was best explained by the concentration of exchangeable and Fe-Me oxides-bound fractions,while that of Zn was best explained by the concentrations of exchangeable,carbonates-bound and Fe-Me oxides-bound fractions. Furthermore,there were strong positive correlations between the concentrations of the exchangeable fraction in the pig manure and the concentrations of corresponding metal accumulated in E.fetida,e.g.,Cu（R=0.973,p＜0.01） and Zn（R=0.702,p＜0.01）.It confirmed that the higher the concentration of exchangeable fraction in pig manure was,the higher the corresponding metal concentration of earthworm was.2.Study on the effect of the transit through the gut of earthworm（E.fetida） on fractionation of Cu and Zn in pig manure.The study was investigated the fractionation of Cu and Zn in the earthworm（E.fetida） casts from pig manure,the effect of the gut transit on the factors affecting the metal fractionation,like pH, organic matter（OM）,total phosphorous（TP） and the amount of Cu and Zn,and the relationship between fractionation of metal in the earthworm cast and factors.It showed that the content of Cu bound to organic matter in pig manure increased from 60%to 75%after transit through the gut of earthworm,whereas that of Zn decreased from 50%to 25%.Based on these changes,Cu was less bioavailable,whereas Zn was more bioavailable.The factors affecting metal fractionation,like pH,organic matter（OM） and total phosphorous（TP） contents,and total metal concentration,were also affected significantly by the transit through the gut of earthworm.The pH value was significantly lower（p＜0.05） in the earthworm casts compared with the pig manure.As well as the pH,OM content decreased significantly（p＜0.05）.On the contray,the contents of TP and total Cu and Zn increased significantly.Stepwise multiple regression analysis revealed that the fractionation of Cu in the earthworm casts was influenced by OM,TP and the amount of Cu in the earthworm casts.The total Zn concentration in the earthworm casts was the primary factor that explained most of the variation in Zn fractionation.3.Study on the control of Cu and Zn in the pig manure-earthworm system.The peat was added to the pig manure at the level of 0%,5%,10%and 15%（mass ratio）, respectively,so were phosphate rock and fly ash.Earthworms were reared with the mixture in the greenhouse.The study was investigated the effect of additives on the accumulation of Cu and Zn in earthworms（E.fetida）,the concentrations of Cu and Zn in earthworm cast and,the bioavailability of Cu and Zn in earthworm cast.It showed that the amount of Cu and Zn accumulated in E.fetida was reduced by adding additives;the concentrations of Cu in E.fetida were reduced between 1.82 and 9.72 mg kg^-1 by adding peat to pig manure,with the maximal extent to 29.16%,and those of Zn were reduced between 4.56 and 67.58 mg kg^-1,with the maximal extent to 42.09%.As for phosphate rock,the concentrations of Cu in E.fetida were reduced between 1.25 and 8.26 mg kg^-1,with the maximal extent to 24.41%,and those of Zn were reduced between 3.85 and 45.63 mg kg^-1,with the maximal extent to 28.42%. The concentrations of Cu in E.fetida were reduced between 1.76 and 10.83 mg kg^-1 by adding fly ash to pig manure,with the maximal extent to 32.02%,and those of Zn were reduced between 5.67 and 59.52 mg kg^-1,with the maximal extent to 32.82%. Obviously,the fly ash played the most significant role in the reducing the amount of Cu accumulated in E.fetida,whereas the peat was the optimal additive for that of Zn. The additives did not reduce but increase the concentrations and bioavailability of Cu and Zn in earthworm cast.

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