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Journal of Hazardous Materials 163(2009)671–677

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Journal of Hazardous

Materials

j o u r n a l h o m e p a g e :w w w.e l s e v i e r.c o m /l o c a t e /j h a z m a

Phytotoxicity and speciation of copper,zinc and lead during the aerobic composting of sewage sludge

Miao-miao He,Guang-ming Tian ?,Xin-qiang Liang

Department of Environmental Engineering,College of Environment and Resources Science,Zhejiang University,Hangzhou 310029,China

a r t i c l e i n f o Article history:

Received 19May 2007

Received in revised form 16May 2008Accepted 4July 2008

Available online 11July 2008Keywords:

Sewage sludge Composting

Heavy metal speciation Phytotoxicity

a b s t r a c t

The content and speciation of heavy metals in composted sewage sludge is the main cause of negative impacts on environment and health of animal and human.An aerobic composting procedure was con-ducted to investigate the in?uences of some key parameters on phytotoxicity and speciation of Cu,Zn and Pb during sewage sludge composting.The pH value reached the optimal range for development of microorganisms,and content of organic matter (OM)and dissolved organic carbon (DOC)decreased with the composting age.The total amounts of Cu,Zn and Pb were much lower in the ?nal compost.The results from sequential extraction procedure of heavy metals showed that composting process changed the distribution of ?ve fractions of Cu,Zn and Pb,and reduced the total contents and sum percentages of four mobile fractions (exchangeable (EXCH),carbonate (CAR),reducible iron and manganese (FeM-nOX),and organic matter bound (OMB)),indicating that the metal mobility and phytotoxicity decreased after aerobic composting.The seed germination and root growth of Pakchoi (Brassica Chinensis L.)were enhanced with composting age and reached the highest value at the end of compost.The decrease of OM and DOC was signi?cantly correlated to changes of metal distribution and germination index (GI)of Pakchoi.Only for Cu in the compost,the GI could be predictable from the sum mobile metal fractions (EXCH +CAR +FeMnOX +OMB)(R =?0.814*).For Zn and Pb,R value was signi?cantly increased by use of other components,such as pH,OM and DOC,which suggested that the transformation of heavy metal spe-ciation and phytotoxicity of sewage sludge during an aerobic composting was rather strongly dependent on multiple components than a single element.

1.Introduction

Land application of composted sewage sludge represents one of the most cost-effective methods for treatment and ?nal disposal of sewage sludge,because the valuable components (N,P,K,organic matter (OM)and other necessary nutrients for plant growth)in stable sludge can be recycled and the properties of soil can be improved [1–3].Unfortunately,the presence of non-biodegradable and toxic heavy metals limits agricultural application of composted sludge,which tends to accumulate along the food chains and bring potential risks to animal and human [4].

Total heavy metal concentration is an important indicator of pol-lution.It has been reported that total content of metals in sewage sludge was about 0.5–4%(on a dry weight basis)[5].However,heavy metals associated with different fractions had different impacts on the environment [6]and their phytotoxicity would connect to

?Corresponding author.Tel.:+8657186971975;fax:+8657186971898.

E-mail addresses:hemiaomiao0301@https://www.wendangku.net/doc/5a1043713.html, (M.-m.He),gmtian@https://www.wendangku.net/doc/5a1043713.html, (G.-m.Tian),liang410@https://www.wendangku.net/doc/5a1043713.html, (X.-q.Liang).

some forms rather than the total concentration of metals [7].The sequential chemical extraction procedures could provide an under-standing of chemical fractions of heavy metals and was useful for predicting metal mobility,bioavailability and leaching rates [8].

Many researchers have focused on the heavy metal specia-tion and phytotoxicity of composted sewage sludge or raw sludge for agricultural use [9–13].They found that heavy metals in the soils amended by composted sludge presented the higher stability and lower bioavailability [14,15].Walter et al.[12]suggested that composting procedure changed the mobility of heavy metals and reduced the phytotoxicity of sludge.

The composting process accelerates decomposition of organic matter,especially in the stages with high temperature.Conse-quently,the signi?cant variation of properties in compost materials occurred within a relatively short period,such as moisture,pH,ammonia,dissolved organic carbon and humus [16–20].These changes could in?uence the distribution of heavy metal speciation and phytotoxic behavior of the compost materials.Some authors have studied the evolution of metal contents and fractions in the composting system [19–21].However,the phytotoxicity of heavy metals was ignored,and the contribution of heavy metals in mobile

672M.-m.He et al./Journal of Hazardous Materials163(2009)671–677

speciation associated with other physicochemical parameters on the phytotoxic behavior is also needed to evaluate.

In the current study,an aerobic composting experiment was conducted on sewage sludge to evaluate the changes of heavy met-als speciation and phytotoxic behavior in terms of Pakchoi seed germination.Meanwhile,the effects of some key parameters on metal phytotoxicity and speciation during composting were also investigated.

2.Materials and methods

https://www.wendangku.net/doc/5a1043713.html,posting procedure

Dewatered anaerobically digested sewage sludge,collected from Sibao Wastewater Treatment Plant in Hangzhou,China,was mixed with sawdust as a bulking agent at4:1(w/w fresh weight)to obtain a water content of60–70%and C/N ratio of25.The composting reac-tor was cuboid and with inner dimension of1.0m×0.8m×0.8m (length×width×height).The mixture was composted for42days. Composting process was controlled by a forced-aeration static pile system and the air was supplied to the composting mass at50L min?1and12times per day(15min with intermission of 105min per time,totally3h per day).At the depth of0.3m,tem-perature was monitored daily.Three phases were observed during composting:the mesophilic phase(32–50?C,0–4days),the ther-mophilic phase(50–65?C,5–21days,the highest value appeared on day7)and the cooling phase(fall to room temperature,22–42 days).About200g sample was collected from5positions in the composting reactor on days0,4,7,14,21,28and42,and mixed for chemical and biological testing by triplicate.

2.2.Chemical analysis

The moisture content of fresh compost sample was determined by oven-drying at70±5?C[22].The aqueous extracts of com-post were obtained by shaking at200rpm with distilled water at a solid:water ratio of1:10(w/v)for16h at20?C.After the suspension was centrifuged at10,000rpm for20min and?ltered through0.45?m membrane?lter papers,the pH,EC and dissolved organic carbon(DOC)were determined by pH meter,conductiv-ity meter and a total organic carbon analyzer(Apollo9000,USA), respectively.Concentration of organic matter was determined by the Walkley and Black wet dichromate oxidation method[23]. For total N,the method of Kjeldahl digestion–distillation was used[24].Total P was analyzed by the molybdenum blue color method after H2SO4–HClO4digestion[25].Total Cu,Zn and Pb concentrations were analyzed by HF–HNO3–HClO4digesting pro-cedures[26]and measured by AAS(Thermo Solar MKII-6).The selected physicochemical properties of sewage sludge were listed in Table1.

Table1

Selected physicochemical properties of sewage sludge

Properties Sewage sludge(SS)

Moisture(%)82.4±3.5a

pH 6.1±0.07 Electrical conductivity(EC,ds m?1) 1.3±0.1 Organic matter(%)37.6±1.4 Dissolved organic carbon(DOC,g kg?1)10.0±1.7

Total nitrogen(TN,g kg?1)27.7±0.9 Total phosphorus(TP,g kg?1)15.4±0.03

Cu(mg kg?1)346.8±10.6

Zn(mg kg?1)3241.6±52.9

Pb(mg kg?1)194.6±9.5

a The values are means±standard deviations(n=3).2.3.Sequential extraction

Speciation of Cu,Zn and Pb in this study was conducted by using the procedure of Tessier et al.[27],which was widely used in the studies on heavy metals in sludge[12,21,28,29].Five fractions of heavy metal were de?ned:(1)exchangeable(EXCH):1g air-dried sample was extracted with1.0M MgCl2at pH7with agitation at 220rpm for1h at25?C;(2)carbonate(CAR):residue from(1)was extracted with1.0M NaOAc at pH5with agitation at220rpm for 5h at25?C;(3)reducible iron and manganese(FeMnOX):residue from(2)was extracted with0.04M NH2OHHCl in25%HOAc(v/v) for6h at96o C in water bath with occasional agitation;(4)organic matter bound(OMB):residue from(3)was extracted with0.02M HNO3and30%H2O2of pH2for5h at85o C,and then3.2M NH4OAc in20%HNO3(v/v)was added and agitated for0.5h at25?C;(5) residual(RES):residue from(4)was digested by HF–HNO3–HClO4 procedures[26].After centrifugation and?ltration,the supernatant from each extraction was analyzed by AAS(Thermo Solar MKII-6).

According to Tessier,the fraction of EXCH is readily in?uenced by changes of ionic composition in the liquid;CAR is susceptible to pH variations;FeMnOX is unstable in reductive conditions;OMB decomposes and changes under the oxidizing conditions;and RES permanently?xed in crystal lattice and not enter the food chain.In the normal conditions,fractions of EXCH and CAR mainly represent the heavy metal mobility in the short-term.During the composting, however,all of the fractions except RES make contributions to the metal mobility and bioavailability due to the rapid evolutions of compost properties.

2.4.Pseudo values of heavy metals

Since volatilization of gases and leaching of liquids following the decomposition and mineralization procedures of organic mat-ter during composting,the Cu,Zn and Pb were concentrated in the compost mass[30].To correct this excessive part of heavy metal contents during composting,all concentration values were nor-malized by the moisture content.The corrected pseudo values of heavy metals were evaluated using following formula as described similarly by Amir et al.[19]:

C p=

C a×(1?m0)

1?m t

(mg kg?1)(1)

where C a is the actually measured value of heavy metals(mg kg?1 dry compost);m0is moisture content in the compost sample of0 day;m t is the moisture content at each sampling time(0,4,7,14, 21,28and42days).

2.5.Germination test for the pakchoi seeds

The germination assay was tested using Pakchoi(Brassica Chi-nensis L.)seed,which has a quick growth rate(harvest in about2 months from sowing)and was popular to be used as a phytotoxic indicator to evaluate environmental risk of soil contamination by metals[31].

Compost extracts(three replicates for each sample)were prepared by shaking fresh samples with distilled water at a solid:water=1:10(w/v)for1h.The suspensions were then cen-trifuged,?ltered and kept at4?C before testing.For germination tests,5mL of each extract were dispensed into a sterilized Petri-dish,which was lined with a?lter paper.50seeds of Pakchoi were placed in one dish and incubated at25?C in the dark for3days. Distilled water was used as the control.Treatments were evalu-ated by counting the number of germinated seeds and measuring the length of the root.The percentage of relative seed germination

M.-m.He et al./Journal of Hazardous Materials163(2009)671–677673

Table2

pH values,organic matter contents(OM),and dissolved organic carbon(DOC)con-

centrations during sewage sludge composting

Time(day)pH OM(%)DOC(g kg?1DW)

07.1±0.1a b b65.2±2.2a14.0±1.3a

47.0±0.1b62.2±0.0ab13.6±0.5a

77.9±0.2a60.1±2.7b9.9±0.7b

147.3±0.1b56.5±1.4bc10.1±0.4b

217.0±0.1b55.6±3.9c8.6±0.4c

28 6.9±0.6b52.7±2.0c 6.0±0.6d

42 6.8±0.3b47.0±0.9d 3.5±0.2e

a The values are means±standard deviations(n=3).

b Means with the same letter in a column are not different at P<0.05(LSD test).

(RSG),relative root growth(RRG)and germination index(GI)were

calculated according to the following formula[32,33]:

RSG(%)=number of seeds germinated in sample extract

number of seeds germinated in control

×100

(2)

RRG(%)=root length in sample extract

root length in control

×100(3)

GI=RSG×RRG

100

(4)

2.6.Statistical analysis

All results were presented as the average of three replicates.Cor-relation(Pearson correlation)and linear regression analysis were performed by SPSS Version12.0for windows.

3.Results

3.1.Changes of key parameters during composting

The pH of compost decreased slightly during the mesophilic phase,but increased to the maximum value(pH7.9)on the day 7(Table2).Then,pH fell gradually to6.8in the?nal compost, which was in the range of optimum environment for microor-ganism.The decline of pH might be due to decomposition of organic matter,the release of ammonia or the nitrifying process [34].

The organic matter was biodegraded and transformed to the steadier and hydrated fractions in the process of composting[35]. The OM content decreased gradually from65.2%to47.0%during sludge composting(Table2).Similarly,compost DOC fell from14.0 to3.5g kg?1,although a slight increase occurred during the ther-mophilic stage.This conformed to the results of Inbar et al.[36] and Zheng et al.[20]for composting of cattle manure and sewage sludge,respectively.

3.2.Heavy metal speciation during composting

The total amounts of Cu,Zn and Pb decreased remarkably during the initial21days of composting(Fig.1b,d,f).This was probably due to the higher leaching rate of soluble metals during the mesophilic and thermophilic stages.After thermophilic phase,changes of total metals tended to be steady.According to the limitation of pollu-tants for agricultural use of China[37],the concentrations of Cu and Pb were within“clean”concentrations(in the soil of pH<6.5: Cu250mg kg?1;Pb300mg kg?1),which indicated the lower risk of mature compost for land application.

The exchangeable and carbonate Cu only accounted for the small parts of total Cu.Their concentrations increased,although a decrease tendency appeared during thermophilic phase(Fig.1a).The maximum increasing percents of EXCH-Cu and CAR-Cu were 1.26%and1.10%,respectively,which occurred in the cooling and thermophilic stages,respectively(Fig.2a).Both of FeMnOX-Cu and OMB-Cu dropped sharply during initial21days,and then leveled off in the remainder composting period(Fig.1a and b).The relative per-centage of Fe–Mn oxide and organic matter bound Cu also declined, especially during thermophilic stage(Fig.2a).These results indi-cated that composting process transformed FeMnOX and OMB fractions of Cu into the more extractible fractions of EXCH-Cu and CAR-Cu.The residual Cu was almost stable(95.0±4.0mg kg?1)in the whole process(Fig.1b),and its relative percent increased from 37.46%in the initial compost to48.68%in the?nal compost.OMB-Cu and RES-Cu accounted for the most predominant speciation throughout sludge composting.

The contents of EXCH-Zn and CAR-Zn increased in the mesophilic phase and then tended to remain constant(Fig.1c). The relative percentages of EXCH-Zn and CAR-Zn,respectively, increased6.82%and9.06%during mesophilic and thermophilic phases(Fig.2b).Conversely,FeMnOX-Zn declined rapidly from 668.9mg kg?1(28.59%of initial total Zn)to302.3mg kg?1(16.15% of?nal total Zn)during mesophilic and thermophilic stages,and kept steadily at about300mg kg?1in the cooling stage(Figs.1c and2b).This decreasing trend led dominant fraction of Zn shifted from FeMnOX-Zn in the initial compost to CAR-Zn in the?nal https://www.wendangku.net/doc/5a1043713.html,paratively,the concentrations of OMB-Zn declined more tardily during composting,and its relative percentage fell from 25.58%to18.21%(Figs.1d and2b).The concentration of RES-Zn?uc-tuated slightly and reached the lowest level(357.5mg kg?1)in the ?nal compost(Fig.1d).The relative percent of residual Zn increased 3.38%during mesophilic and thermophilic phases but decreased 1.07%in the cooling stage.

There was a signi?cant decrease in exchangeable Pb during the initial7days(Fig.1e).The content of EXCH-Pb increased during the later thermophilic stage,but dropped again in the cooling period. The variation percentage of EXCH-Pb was larger than other frac-tions,which declined from12.43%in the initial compost to6.91%in the?nal compost(Fig.2c).CAR-Pb increased slightly and reached the maximum content(10.24mg kg?1)at the end of composting. The concentrations and relative percent of FeMnOX-Pb decreased during thermophilic stage and then leveled off.The change of OMB-Pb was not substantial during sludge composting,and only an increase of0.93%in the mesophilic phase could be distinctly found in the relative percentage of OMB-Pb(Figs.1f and2c).Residual Pb, which accounted for the majority of total Pb,decreased slightly but its percentage climbed from67.28%to70.92%during the compost-ing process.

3.3.Phytotoxicity assay

The germination test was usually used to evaluate the compost maturity and phytotoxicity of biowaste materials[38].This index had been proved to be a more sensitive parameter to illuminate both low toxicity affecting root growth and high toxicity affecting germination[39].

The seed germination and root growth of Pakchoi was highly inhibited by the compost in the mesophilic stage,indicating that immature sewage sludge would cause phytotoxic effects to the plant(Fig.3).During the thermophilic period,relative germina-tion rate(RSG)and root elongation(RRG)climbed rapidly from 5.66%and12.21%to67.58%and73.05%,respectively.The germi-nation index increased gradually in the cooling phase and reached the maximum value in the?nal compost extracts(Fig.3).These results re?ected that the phytotoxicity of compost bulk reduced and the bene?cial effects on Pakchoi were more and more remarkable following the composting process.

674M.-m.He et al./Journal of Hazardous Materials 163(2009)671–677

4.Discussion

4.1.In?uences on transformation of metal speciation during sludge composting

The composting process changed the distribution of ?ve frac-tions of Cu,Zn and Pb,and reduced the total concentrations and sum percentages of four mobile fractions (EXCH,CAR,FeMnOX,and OMB),suggesting that the metal mobility and phytotox-icity decreased after aerobic composting.For Cu and Zn,the proportions of FeMnOX and OMB fractions decreased,while the percents of EXCH,CAR and RES fractions increased,especially during the mesophilic and thermophilic periods.The evolution tendency of Pb speciation was different from Cu and Zn.The rel-ative percentages of EXCH-Pb and FeMnOX-Pb decreased,while the proportions of CAR-Pb,OM-Pb and RES-Pb increased.Pb is known to be not readily detected in the mobile forms and is preferentially bound to the residual fraction [40].In contrast,Cu and Zn prefer to bind with exchangeable and carbonate fractions following the formation of humic substances during composting process.

The pH values had no signi?cant effects on transformation of metal speciation in our study (Table 3).Some authors reported that pH was a factor which could in?uence the evolution of metal dis-tribution during composting [20,21].Other authors,however,also did not ?nd the relationships between pH and transformation of heavy metals in the process of compost [17,19].The diverse results might depend on the different raw materials or different durations of compost.For example,Liu et al.[21]only conducted 288h of sludge compost at a sampling interval of 24h,and the compost bulk was always in the acid condition;while Hsu and Lo [17]and Amir et al.[19]did the composting for more than 100days,and compost samples were neutral or alkaline.In our study,the pH val-ues of compost were shown in the neutral or alkaline conditions (Table 2)and compost duration was much longer than Zheng et al.[20]and Liu et al.[21]

Fig.1.Changes of Cu,Zn,and Pb speciation (EXCH-M,CAR-M,FeMnOX-M,OMB-M and RES-M)and total concentrations (T-M)during sewage sludge composting.

M.-m.He et al./Journal of Hazardous Materials 163(2009)671–677675

The evolutions of CAR-Cu,FeMnOX-Cu,OMB-Cu and sum of four mobile fractions presented signi?cant correlations to the decrease of OM and DOC (Table 3).Residual Cu was positively related to OM,but had no remarkable relationship with DOC.No correlations were found between EXCH-Cu and OM or DOC.For Zn,the decrease of OM and DOC did not signi?cantly correlate to increase of EXCH-Zn and CAR-Zn (Table 3).However,FeMnOX-Zn,OMB-Zn,RES-Zn and sum of four mobile fractions showed remarkable relationships with OM and DOC.Unlike Cu and Zn,EXCH-Pb and CAR-Pb have more af?nity for OM and DOC (Table 3).However,the decrease of OMB-Pb,RES-Pb and sum of four mobile fractions did not relate to the decline of OM and DOC.Our results were inconsistent with those of Amir et al.[19]and Liu et al.[21],who found the signi?cant correla-tions between easily extractable fractions (exchangeable fraction,or fractions with extractant of water-soluble or KNO 3)of Cu and Zn and organic matter contents.For exchangeable or water-soluble Pb,they did not ?nd the correlations with organic matter.The exchangeable or water-soluble fractions of metals could easily

leach

Fig.2.Variations of relative percentage in Cu,Zn and Pb speciation (EXCH,CAR,FeM-nOX,OMB and RES)during mesophilic,thermophilic and cooling phases of sewage sludge

composting.

Fig.3.Changes of the percentage of relative seed germination (RSG),relative root growth (RRG)and germination index (GI)during sewage sludge composting.

out with H 2O during composting;on the other hand,these forms could be transformed from other fractions following the decom-position of organic matters.It is dif?cult to determine how much the leaching and transformation,respectively,account for the over-all variations,so that there are diverse results on the most easily extractible speciation.However,in our study,changes of EXCH-Cu during later thermophilic and cooling stages of sludge composting were signi?cantly correlated to decrease of OM (R =?0.902**)and DOC (R =?0.975**),and EXCH-Zn in the thermophilic phase was related to OM (R =0.775*)and DOC (R =?0.817*).For other frac-tions,the results were similar to those of Amir et al.[19]and Liu et al.[21].

4.2.In?uences on metal phytotoxicity during sludge composting The seed germination and root growth of Pakchoi signi?cantly increased with composting age and reached the highest value at the end of compost (RSG =92.3%,RRG =101.7%and GI =93.9%),indi-cating the lowest phytotoxicity existed in the ?nal compost.As reported by Zucconi et al.[39],the compost was phytotoxic-free when GI values were higher than 80%.However,results about GI should be carefully used on the agricultural application.If the com-posts with a GI of about 95%are applied to agricultural land,it could

Table 3

Linear correlation coef?cients (R )of heavy metals speciation with pH,organic matter contents (OM),and dissolved organic carbon concentrations (DOC)during sewage sludge composting

OM DOC Cu

EXCH 0.040?0.517?0.606CAR

?0.353?0.836*?0.769*FeMnOX 0.3220.925**0.929**OMB 0.2210.926**0.919**RES

0.5890.763*0.703EXCH +CAR +FeMnOX +OMB 0.2240.923**0.916**Zn

EXCH 0.211?0.650?0.671CAR

0.194?0.373?0.323FeMnOX 0.1890.865*0.841*OMB 0.6210.854*0.778*RES

0.1830.869*0.848*EXCH +CAR +FeMnOX +OMB 0.3040.818*0.798*Pb

EXCH ?0.0130.816*0.822*CAR

?0.420?0.923**?0.965**FeMnOX 0.2330.898**0.907**OMB 0.0130.5170.407RES

0.6520.7220.598EXCH +CAR +FeMnOX +OMB

?0.035

0.717

0.686

(*and **):Statistically signi?cant at the probability level 0.05and 0.01,respectively (2-tailed).

676M.-m.He et al./Journal of Hazardous Materials163(2009)671–677

Table4

Linear correlation coef?cients(R)of relative seed germination(RSG),relative root growth(RRG)and germination index(GI)with pH,organic matter contents (OM),dissolved organic carbon concentrations(DOC),and sum of mobile fractions (EXCH+CAR+FeMnOX+OMB)during sewage sludge composting

pH OM DOC EXCH+CAR+FeMnOX+OMB

Cu Zn Pb RSG?0.569?0.942**?0.941**?0.896**?0.815*?0.688 RRG?0.551?0.971**?0.946**?0.924**?0.741*?0.706 GI?0.643?0.940**?0.938**?0.814*?0.629?0.513

(*and**):Statistically signi?cant at the probability level0.05and0.01level,respec-tively(2-tailed).

still lead the negative effects on seed germination and plant growth. Therefore,it’s better to prolong the compost maturation duration to further decline the negative effects.

To determine if and how the key parameters affect the compost phytotoxicity,the linear regression analysis of Pakchoi germination assay with pH,OM,DOC,and sum of mobile metal fractions were analyzed(Tables4and5).

The pH value did not signi?cantly related to the Pakchoi ger-mination and root growth(Table4),which varied from the data of Kim et al.[41].This might be due to the usage of different com-post curing progresses.However,similar to Kim et al.[41],the changes of Pakchoi germination and root growth were highly cor-related to progressive degradation of OM and DOC(Table4).The organic matter and dissolved organic carbon during composting were important factors in compost maturity[42,43]and controlling phytotoxicity of compost[20,44].The ethylene oxide,short-chain aliphatic acids and various phenolic compounds,which are pro-duced during the decomposition of organic matter and presented in dissolved organic matter,were identi?ed as the phytotoxic agents and might suppress seed germination[45,46].Once these materials disappeared,plant growth was markedly enhanced.

The Pakchoi seed germination(RSG)and root growth rate (RRG)had the signi?cantly negative correlations with sum mobile fractions(EXCH+CAR+FeMnOX+OMB)of Cu and Zn,but no rela-tionship was found with Pb(Table4).The germination index, which was used to evaluate the phytotoxicity of compost,could only be estimated by overall mobile fractions of Cu(R=?0.814*, Tables4and5).For Zn and Pb,the R-values were signi?cantly increased by utilizing other components,such as pH,OM and DOC

Table5

Data on the linear regression analysis for germination index(GI)in relation to the sum of mobile fractions(EXCH+CAR+FeMnOX+OMB)of Cu,Zn and Pb,and other key parameters(pH,organic matter content(OM),and dissolved organic carbon (DOC))

Linear regression analysis R

GI=?1.268Cu(EXCH+CAR+FeMnOX+OMB)+192.8560.814* GI=?1.099Cu(EXCH+CAR+FeMnOX+OMB)?49.56pH

+524.619

0.914*

GI=0.57Cu(EXCH+CAR+FeMnOX+OMB)?0.812OM+426.4810.950** GI=0.112Cu(EXCH+CAR+FeMnOX+OMB)?36.109pH?9.03DOC

+362.358

0.997***

GI=?0.170Zn(EXCH+CAR+FeMnOX+OMB)+308.5290.629 GI=?0.143Zn(EXCH+CAR+FeMnOX+OMB)?44.037pH+578.830.925* GI=0.11Zn(EXCH+CAR+FeMnOX+OMB)?36.849pH?8.807DOC

+362.311

0.997***

GI=?5.674Pb(EXCH+CAR+FeMnOX+OMB)+241.2370.570 GI=3.052Pb(EXCH+CAR+FeMnOX+OMB)?11.969DOC+35.6260.959** GI=2.785Pb(EXCH+CAR+FeMnOX+OMB)?13.196pH?0.698OM

+425.055

0.978*

GI=0.80Pb(EXCH+CAR+FeMnOX+OMB)?34.132pH

?9.04DOC+333.237

0.998***

(*,**and***):Statistically signi?cant at the probability level0.05,0.01,and0.001 levels,respectively(2-tailed).(Table5).Although the neutral or alkaline conditions(pH>7.0)in our research did not signi?cantly in?uence mobility and bioavail-ability of heavy metals,the pH still could enhance the phytotoxicity of metals as an accessorial factor.Decomposition of organic mat-ter and dissolved organic carbon could decrease organic hazardous agents of compost;meanwhile,it reduced mobility of heavy metals and consequently decreased the phytotoxic behavior.Additionally, DOC can form stable and soluble complexes with heavy metals,so that the risks of heavy metals in the compost on plant might be weakened with the decomposition or leaching of DOC[16].

These results con?rmed that the evaluation of metal phyto-toxicity during sewage sludge composting was dependent on the multiple components,besides the mobile metal fractions,rather than the single element.In arriving at a meaningful model for assessment of in?uences on heavy metal phytotoxicity and spe-ciation during composting,the knowledge about heavy metals associated with other physicochemical properties is important.

In summary,decomposition of organic matter during com-posting was the most important accessorial factor to in?uence phytotoxicity and speciation of heavy metals.From an agricultural point of view,therefore,decomposition degree of organic matter during composting should be paid particular attentions.Addition-ally,the land application of stable sewage sludge with high OM or DOC content needs long-term?eld studies to determine their potential toxicity and minimize the negative environmental effects. Acknowledgements

This research was supported by provincial technique program of Zhejiang(2004c23024).The authors would like to thank some anonymous reviewers for their helpful suggestions on earlier drafts of this manuscript.

References

[1]T.Hemández,J.L.Moreno,F.Costa,In?uence of sewage sludge application on

crop yields and heavy metal availability,Soil Sci.Plant Nutr.37(1991)201–210.

[2]S.R.Smith,Agricultural Recycling of Sewage Sludge and the Environment,C.A.B.

International,Wallingford,1996,pp.207–236.

[3]R.Zu?aurre,A.Olivar,P.Chamorro,C.Nerín,A.Callizo,Speciation of metals in

sewage sludge for agricultural uses,Analyst123(1998)255–259.

[4]A.C.Chang,T.C.Granato,A.L.Page,A methodology for establishing phytotoxicity

criteria for Cr,Cu,Ni,and Zn in agricultural land application of municipal sewage sludges,J.Environ.Qual.21(1992)521–536.

[5]L.Wong,J.G.Henry,Bacterial leaching of heavy metals from anaerobically

digested sludge,in:D.L.Wise(Ed.),Biotreatment System,vol.2,CRC Press, Boca Raton,FL,1988,pp.125–169.

[6]N.F.Y.Tam,Y.S.Wong,Retention and distribution of heavy metals in mangrove

soils receiving wastewater,Environ.Pollut.94(1996)283–291.

[7]P.Flyhammar,Use of sequential extraction of heavy metals on anaerobically

municipal solid waste,Sci.Total Environ.212(1998)203–215.

[8]W.Grazebisz,W.Z.Kocialkowski,B.Chudzinski,Copper geochemistry and avail-

ability in cultivated soils contaminated by a copper smelter,J.Geochem.Explor.

58(1997)301–307.

[9]B.J.Alloway,A.P.Jackson,The behavior of heavy metals in sewage sludge-

amended soils,Sci.Total Environ.100(1991)151–176.

[10]J.T.Sims,J.S.Kline,Chemical fractionation and plant uptake of heavy metals in

soils amended with co-composted sewage sludge,J.Environ.Qual.20(1991) 387–395.

[11]V.Antoniadis,B.J.Alloway,The role of dissolved organic matter in the mobility

of Cd,Ni and Zn in the sewage sludge-amended soils,Environ.Pollut.117(2002) 515–521.

[12]I.Walter,F.Martínez,V.Cala,Heavy metal speciation and phytotoxic effects of

three representative sewage sludges for agricultural uses,Environ.Pollut.139 (2006)507–514.

[13]Q.Y.Cai,C.H.Mo,Q.T.Wu,Q.Y.Zeng,A.Katsoyiannis,Concentration and specia-

tion of heavy metals in six different sewage sludge-composts,J.Hazard Mater.

147(2007)1063–1072.

[14]N.Korboulewsky,S.Dupouyet,G.Bonin,Environmental risks of applying

sewage sludge compost to vineyards:carbon,heavy metals,nitrogen,and phos-phorus accumulation,J.Environ.Qual.31(2002)1522–1527.

[15]P.R.Warman,W.C.Termeer,Evaluation of sewage sludge,septic waste and

sludge compost applications to corn and forage:yields and N,P and K content of crops and soils,Bioresour.Technol.96(2005)955–961.

M.-m.He et al./Journal of Hazardous Materials163(2009)671–677677

[16]J.H.Hsu,S.L.Lo,Chemical spectroscopic analysis of organic matter transforma-

tions during composting of pig mature,Environ.Pollut.104(1999)189–196.

[17]J.H.Hsu,S.L.Lo,Effect of composting on characterization and leaching if copper,

manganese,and zinc from swine manure,Environ.Pollut.114(2001)119–127.

[18]F.Amlinger,B.G?tz,P.Dreher,J.Geszti,C.Weissteiner,Nitrogen in biowaste

and yard waste compost:dynamics of mobilization and availability—a review, Eur.J.Soil Biol.39(2003)107–116.

[19]S.Amir,M.Ha?di,G.Merlina,J.C.Revel,Sequential extraction of heavy metals

during composting of sewage sludge,Chemosphere59(2005)801–810. [20]G.D.Zheng,D.Gao,T.B.Chen,W.Luo,Stabilization of nickel and chromium in

sewage sludge during aerobic composting,J.Hazard Mater.142(2006)216–221.

[21]Y.S.Liu,L.L.Ma,Y.Q.Li,L.T.Zheng,Evolution of heavy metal speciation dur-

ing the aerobic composting process of sewage sludge,Chemosphere67(2007) 1025–1032.

[22]U.S.Department of Agriculture and https://www.wendangku.net/doc/5a1043713.html,posting Council,Test Methods for

the Examination of Composting and Compost,Edaphos International,Houston, TX,2001.

[23]D.V.Nelson,L.E.Sommers,Methods of Soil Analysis,Part3:Total Carbon,

Organic Carbon and Organic Matter,SSSA,Madison,1982,pp.539–579. [24]J.M.Bremner,Methods of Soil Analysis,Part3:Chemical Methods,SSSA,Madi-

son,1996,pp.1103–1108.

[25]S.Kuo,Methods of Soil Analysis,Part3:Chemical Methods,SSSA,Madison,

1996,pp.908–910.

[26]M.R.Carter,Soil Sampling and Methods of Analysis,Lewis Publishers,London,

1993.

[27]A.Tessier,P.G.X.Campbell,M.Bisson,Sequential extraction procedure for the

speciation of particulate trace metals,Anal.Chem.51(1979)844–851.

[28]Y.M.Luo,P.Christie,Bioavailability of copper and zinc in soils treated with

alkaline stabilized sewage sludge,J.Environ.Qual.27(1998)335–342.

[29]J.W.C.Wong,K.Li,M.Fang,D.C.Su,Toxicity evaluation of sewage sludges in

Hong Kong,Environ.Int.27(2001)373–380.

[30]S.Canaruttto,G.Petruzzelli,L.Lubrano,G.V.Guidi,How composting affects

heavy metal content,BioCycle32(1991)48–50.

[31]M.P.Hirsch,Availability of sludge-borne silver to agricultural crops,Environ.

Toxicol.Chem.17(1998)610–616.

[32]N.J.Hoekstra,T.Bosker,https://www.wendangku.net/doc/5a1043713.html,ntinga,Effects of cattle dung farms with different

feeding strategies on germination and initial root growth of cress(Lepidium sativum L.),Agric.Ecosyst.Environ.93(2002)189–196.[33]A.Fuentes,M.Lloréns,J.Sáez,M.I.Aguilar,J.F.Ortu?no,V.F.Meseguer,Phytotox-

icity and heavy metals speciation of stabilised sewage sludges,J.Hazard Mater.

108(2004)161–169.

[34]S.H.Atchley,J.B.Clark,Variability of temperature,pH,and moisture in aerobic

composting process,Appl.Environ.Microb.38(1979)1040–1044.

[35]O.Reinikainen,M.Herranen,Different methods for measuring compost stabil-

ity and maturity,in:B.Balis,https://www.wendangku.net/doc/5a1043713.html,saridi,R.A.K.Szmidt,E.Stentiford,J.Lopez-Real (Eds.),Acta Horticulturae:Proceedings of the International Symposium on Composting of Organic Matter,vol.549,ISHS,Belgium,2001,pp.99–102. [36]Y.Inbar,Y.Hadar,Y.Chen,Recycling of cattle manure:the composting process

and characterization of maturity,J.Environ.Qual.22(1993)857–863.

[37]Chinese EPB,Limitation of pollutants in solid wastes for agricultural use of

China(GB4284-84)[S],Chinese State Standard,1984.

[38]N.Roe,P.Stoffella,D.Graetz,Compost from various municipal solid wastes

feed stocks affect vegetable crops.I.Emergence and seedling growth,J.Am.

Soc.Hortic.Sci.122(1997)427–432.

[39]F.Zucconi,A.Pera,M.Forte,M.De Bertoldi,Evaluating toxicity of immature

compost,BioCycle22(1981)54–57.

[40]G.Petruzzelli,L.Ottaviani,E.Lubrano,Veschetti,Characterization of heavy

metal mobile species in sewage sludge for agricultural utilization,Agrochimica 38(1994)277–284.

[41]K.Y.Kim,H.W.Kim,S.K.Han,E.J.Hwang,C.Y.Lee,H.S.Shin,Effect of granular

porous media on the composting of swine manure,Waste Manage28(2008) 2336–2343.

[42]C.Garcia,T.Hernandez,F.Costa,Changes in carbon fractions during composting

and maturation of organic wastes,Environ.Pollut.15(1991)433–439.

[43]S.Zmora-Nahum,O.Markovitcha,J.Tarchitzky,Y.Chen,Dissolved organic car-

bon(DOC)as a parameter of compost maturity,Soil Biol.Biochem.37(2005) 2109–2116.

[44]K.A.Bolton,L.J.Evans,Elemental composition and speciation of some land?ll

leachates with particular reference to cadmium,Water Air Soil Pollut.60(1991) 43–53.

[45]M.H.Wong,Y.H.Cheung,C.L.Cheung,The effects of ammonia and ethylene

oxide in animal manure and sewage sludge on the seed germination and root elongation of Brassica parachinensis,Environ.Pollut.30(1983)109–123. [46]F.Zucconi,A.Monaco,M.Forte,M.De Bertoldi,Phytotoxins during the stabi-

lization of organic matter,in:J.K.R.Grasser(Ed.),Composting of Agricultural and Other Wastes,Elsevier Science,Amsterdam,1985,pp.73–86.