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Speciation of Cu and Zn during composting of pig manure amended with rock phosphate
Waste Management xxx (2014) xxx–xxx
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Speciation of Cu and Zn during composting of pig manure amended with rock phosphate Duian Lu a,b, Lixia Wang a,⇑, Baixing Yan a, Yang Ou a, Jiunian Guan a,b, Yu Bian a,b, Yubin Zhang c a
Key Laboratory of Wetland Ecology and Environment, Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Changchun 130102, PR China University of Chinese Academy of Sciences, Beijing 100049, PR China c College of Plant Science, JiLin University, Changchun 130062, PR China b
a r t i c l e
i n f o
Article history: Received 15 January 2014 Accepted 4 April 2014 Available online xxxx Keywords: Toxic metal Pig manure Composting Rock phosphate
a b s t r a c t Pig manure usually contains a large amount of metals, especially Cu and Zn, which may limit its land application. Rock phosphate has been shown to be effective for immobilizing toxic metals in toxic metals contaminated soils. The aim of this study work was to investigate the effect of rock phosphate on the speciation of Cu and Zn during co-composting of pig manure with rice straw. The results showed that composting process and rock phosphate addition significantly affected the changes of metal species. During co-composting, the exchangeable and reducible fractions of Cu were transformed to organic and residue fractions, thus the bioavailable Cu fractions were decreased. The rock phosphate addition enhanced the metal transformation depending on the level of rock phosphate amendment. Zinc was found in the exchangeable and reducible fractions in the compost. The bioavailable Zn fraction changed a little during the composting process. The composting process converted the exchangeable Zn fraction into reducible fraction. Addition of an appropriate amount (5.0%) of rock phosphate could advance the conversion. Rock phosphate could reduce metal availability through adsorption and complexation of the metal ions on inorganic components. The increase in pH and organic matter degradation could be responsible for the reduction in exchangeable and bioavailable Cu fractions and exchangeable Zn fraction in rock phosphate amended compost. Ó 2014 Elsevier Ltd. All rights reserved.
1. Introduction The intensive and industrial livestock production generates large amounts of pig manure in China and has led to inappropriate disposal practices when it is used as an organic fertilizer (Chen et al., 2010). Continuous agricultural utilization of pig manure may pose environmental problems, such as water contamination, odor pollution and soil accumulation of toxic metals (GomezBrandon et al., 2008; Lu et al., 2013). The environmental problems have given rise to the need for environmentally sound and economically feasible technologies for treating pig manure before application to agricultural lands (Chen et al., 2010). Composting pig manure may provide a better alternative for manure management. Composting is a spontaneous biological decomposition process of organic materials in a predominantly aerobic environment (Bernal et al., 2009). During composting, the organic materials are degraded into full mineralized materials such as CO2, H2O, mineral ions, stabilized organic matter (OM) and ash, resulting in a net loss ⇑ Corresponding author. Tel.: +86 431 85542325; fax: +86 431 85542260. E-mail address: [email protected] (L. Wang).
of total OM and a concentration of inorganic constituents. Thus, composting could reduce the volume and weight of the raw materials. As the compost product is stable and usually contains large amounts of nutrients, it could be applied to agricultural lands as valuable fertilizer and soil amendment (Bernal et al., 2009). Several researchers have shown that pig manure may contain higher concentrations of Cu and Zn than other metals, because of feed additives in livestock production (Cang et al., 2004; Wang et al., 2013; Zhang et al., 2012). It is common practice to add minerals such as Cu and Zn to animal feeds via mineral additives because of their antimicrobial and growth-stimulating effects (Zhang et al., 2012). Consequently, successive application of pig manure to agricultural lands may be noxious to soils, plants, and human health. Toxic metals uptake by plant will lead to accumulation in human tissues and cause adverse effects on human health via food chain. Focus on the improvement of the composting process to reduce the availability of toxic metals using various minerals is attracting the attention of researchers. The effects of additives on composting have been intensely studied. Wong and Selvam (2006) found that co-composting of sewage sludge with lime could significantly reduce the availability of toxic metals in
http://dx.doi.org/10.1016/j.wasman.2014.04.008 0956-053X/Ó 2014 Elsevier Ltd. All rights reserved.
Please cite this article in press as: Lu, D., et al. Speciation of Cu and Zn during composting of pig manure amended with rock phosphate. Waste Management (2014), http://dx.doi.org/10.1016/j.wasman.2014.04.008
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the final composts, as well as pathogens. Natural zeolite and clinptilolite have been proved to be a suitable material for toxic metals immobilization during composting of sewage sludge (Zorpas et al., 2008). The industrial waste by-product (red mud) has been reported as a useful amendment in reducing metal leachability and plant availability in sludge compost (Qiao and Ho, 1997). However, information on the metal speciation during co-composting of pig manure with rock phosphate (RP) has not been well reported. Phosphorus deficiency is a major limiting factor in the majority of soils for crop production (Richardson et al., 2009). Using RP as fertilizer to overcome P deficiency was repeatedly reported (Kolawole and Tian, 2007). The direct use of RP is limited by its poor solubility, especially in alkaline soils (Verma et al., 2013). Addition of RP into composts could enhance the nutrient value of the compost. Furthermore, the composting process will help to accelerate the mobilization of unavailable P in RP, which in turn will help in supplying P to crops (Zayed and Abdel-Motaal, 2005). RP has been demonstrated to be a good chemical amendment for reducing metal bioavailability in situ remediation in toxic metals contaminated soils (Cajuste et al., 2006; Chen et al., 2007). Total metal concentration is an important indicator of pollution risks, but it provides little or no indication of their specific bioavailability or mobility (Tack and Verloo, 1995). The knowledge of metal speciation may be useful to assess the potential environmental effects as metal associated with different fractions have different impacts on the environment (Ben Achiba et al., 2010). The sequential extraction procedure could provide the understanding of the natures of metal fractions and allow the prediction of metal mobility or bioavailability (Hahladakis et al., 2013; Tsai et al., 2003). The present study aimed at evaluating the effect of the addition of RP on the speciation of Cu and Zn during co-composting of pig manure with rice straw. Parameters such as pH, OM were determined in order to investigate the correlation between the exchangeable and bioavailable metals and the parameters for different treatments. 2. Materials and methods 2.1. Experimental procedure There were four different treatments in the study. Rice straw was used as a bulking agent for adjusting the C/N ratio of the pig manure to a value of 20. The compost mixture (about 30 kg each, fresh weight) was then mixed thoroughly with RP (particle diameter <0.149 mm) at 0% (CK), 2.5% (P2.5), 5.0% (P5.0), 7.5% (P7.5) (w/w, dry weight basis). Composting was conducted in a bin with a volume of 98L. Moisture content of the stock material was initially adjusted to about 70% and was then maintained at the same level by adding necessary deionized water during composting. The compost piles were turned and mixed every two days throughout the composting process for aeration. Temperature was recorded daily using a thermometer at the center of the compost piles. The composting lasted 49 days and triplicate independent samples were taken during the composting time (on day 1, 7, 15, 23, 31, 39, 49). The compost samples were air dried, ground and sieved to <0.25 mm for further analyses. The physicochemical properties of the experimental raw materials are shown in Table 1. 2.2. Chemical analysis pH and electrical conductivity (EC) were measured in water extracts at 1:10 (w/v) (He et al., 2009). Ash content was determined by combustion at 550 °C for 8 h. Organic matter was determined by subtraction of ash content. Total organic carbon
Table 1 Physicochemical properties of the experimental raw materials (dry matter basis).a
a b c
Parameter
Pig manure
Rice straw
Rock phosphate
pH EC (dS m 1) Total N (g kg 1) Total P (g kg 1) Organic matter (g kg Cu (mg kg 1) Zn (mg kg 1)
7.10 ± 0.01 3.65 ± 0.01 31.49 ± 0.62 15.80 ± 0.23 806.03 ± 3.73 453.66 ± 2.33 3401.25 ± 44.20
7.03 ± 0.01 3.01 ± 0.02 11.42 ± 0.01 3.63 ± 0.10 886.86 ± 9.92 99.75 ± 32.17 492.75 ± 119.14
9.46 ± 0.01 0.99 ± 0.05 NDb 366.18 ± 14.23 NDb TQc 63.48 ± 0.01
1
)
Values (mean ± standard) are the averages of three replicates. Not detected. Trace quantity.
was calculated as 58% of OM (Zmora-Nahum et al., 2005). Total N and P contents in the composts were determined by Kjeldhal digestion and analysed by indophenols-blue method for NH+4 and ascorbic acid method for PO34 (Bremner, 1996). Available P was determined using NaHCO3 (Sinegani and Hosseinpur, 2010). Total toxic metal was determined using atomic absorption spectrophotometry (AAS) (GBC 932, Australian) after digestion with concentrated HNO3 and HClO4 (Jones and Case, 1990). The modified BCR sequential extraction method was carried out for the sequential extraction of Cu and Zn (Nemati et al., 2011). In the modified BCR procedure, all toxic metals are partitioned into four operationally defined fractions: exchangeable (EXC), reducible (RED), oxidizable (OXI) and residual (RES). The EXC fraction was extracted with 40 ml of 0.11 M CH3COOH by shaking the sample for 16 h at room temperature. The RED fraction in the second step was extracted with 40 ml of 0.5 M NH2OHHCl (adjusted to pH 1.5 with concentrated HNO3) by shaking the residue from the previous step for 16 h at room temperature. To extract the OXI fraction, the residue from the second step was digested with 10 ml of H2O2 for 1 h at room temperature. It was then heated to near dryness in a water bath at 85 °C. An additional 10 ml of H2O2 was added and heated to near dryness again. After cooling, 50 ml of 1.0 M ammonium acetate was added to the residue and shaken for 16 h at room temperature. The RES fraction was obtained by digestion the residue from the third step with aquaregia and HF. The supernatant from each extraction was analyzed by AAS (GBC 932, Australian). The bioavailability factor (BF) of Cu and Zn was defined as the ratio of the metal content in EXC and RED fractions to the total metal content (Nomeda et al., 2008). 2.3. Statistical analysis All the figures were performed using OrginPro 8.0. Statistical analysis was performed using SPSS 16.0. Pearson correlation was investigated between the EXC fraction, the BF and selected variables: pH and OM. 3. Results and discussion 3.1. Changes in temperature, pH, EC and C/N ratio The evolutions of temperature were found similarly among the different compost piles (Fig. 1A). The temperature increased rapidly to above 50 °C in the initial 4 days and maintained at the thermophilic phase for nearly one week. Then the temperature decreased and reached ambient temperature on day 31. The similar temperature profile showed that the RP addition did not affect the metabolic activity of microbes. The changes in the pH of the composts are shown in Fig. 1B. In the control treatment, pH increased from 8.35 to 8.75 on day 7 and
Please cite this article in press as: Lu, D., et al. Speciation of Cu and Zn during composting of pig manure amended with rock phosphate. Waste Management (2014), http://dx.doi.org/10.1016/j.wasman.2014.04.008
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A
70
50
CK P2.5 P5.0 P7.5
9.8 9.6 9.4 9.2
40
pH
Temperature (°C)
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10.0
B
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30
8.6 8.4
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8.2 8.0
10 0
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3.0 2.8
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28 26 24 22
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3.2
20
Composting time (days)
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14 1.8 12 1.6 0
10
20
30
40
50
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0
10
20
30
40
50
Composting time (days)
Fig. 1. Changes in (A) temperature, (B) pH, (C) EC and (D) C/N ratio during composting of pig manure amended with rock phosphate.
then decreased to 8.46 at the end of composting. A similar pH trend was found by other researchers during composting (Huang et al., 2004). But in the RP amended composts, pH showed increase at the beginning and reached plateau value on day 31, 23, 7 for P2.5, P5.0 and P7.5, respectively. The increase in pH during the initial stage of composting was mainly because of the degradation of organic acid or release of ammonia compounds, while the decrease in the pH of the composts in the later phase was likely to be a consequence of new synthesis of organic acids and production of phenolic compounds (Satisha and Devarajan, 2007). At the beginning of composting, the pH in the control and RP amended compost was almost the same, which could be due to the buffering effect of the humic substance in the RP amended compost mixture (Hsu and Lo, 1999). Thereafter, the compost mixtures amended with RP showed higher pH than the control treatment and there was no decrease of pH found in the RP amended composts, which might be due to the release of bases from the RP. The dynamics of pH in RP amended compost agreed with the results found during composting of municipal solid waste amended with RP, FeSO4 and lime (Iqbal et al., 2010). These implied that alkaline material addition such as RP and lime provided buffering against the decrease in pH. The changes in EC for all treatments followed the same trend (Fig. 1C). There was a little decrease in EC at the initial 7 days which could be due to the precipitation of mineral ions. Then the EC increased as a consequence of concentration effect and release of mineral salts due to the fierce OM degradation. Addition of RP decreased the EC to low degrees in the composts with an increase in RP amendment level. In all compost mixtures, the C/N ratio increased at the initial 7 days and then decreased thereafter (Fig. 1D). The increase in C/N ratio could be due to the nitrogen losses which were usually found serious at the beginning of composting, while the decrease in C/N ratio could be due to the mineralization of the OM.
3.2. Changes in total P, available P and C/P ratio The compost mixture amended with RP had significantly higher content of total P as compared to the control treatment (Fig. 2A). However, addition of RP reduced the available P content due to the poor solubility of RP and dilution effect (Fig. 2B). The reaction of soluble P with other components (e.g. CaCO3) might also be responsible for the reduction in available P content in the compost. Similarly, Biswas and Narayanasamy (2006) reported that the addition of RP significantly reduced water soluble P content during composting of straw. During composting, significant increases in total P content were obtained in all compost mixtures. The total P content of the control treatment increased from 12.19 g kg 1 in the raw compost mixture to 24.88 g kg 1 in the mature compost, indicating 2.04 times enrichment of P during the composting process, while the total P content of P2.5, P5.0 and P7.5 increased from 18.87 g kg 1, 22.75 g kg 1, 28.01 g kg 1 to 31.81 g kg 1, 41.64 g kg 1, 47.04 g kg 1, respectively, indicating 1.68–1.83 times enrichment of P. The increase of total P was mainly caused by the concentration effect due to the degradation of OM. The C/P ratio decreased significantly during composting process in all compost mixture due to the OM decomposition (Fig. 2C). The available P/total P ratio had an increasing trend during the initial days of composting, but showed decrease in the mature compost (Fig. 2D). The increase in available P/total P ratio at the beginning could be due to the release of available P during the OM degradation. In RP amended compost, the CO2 evolved and organic acid released during decomposition of OM would be responsible for the increase in available P/total P ratio. The organic acid and weak carbonic acid formed by CO2 could dissolve RP and increase the available P content in RP amended compost during composting (Biswas and Narayanasamy, 2006). The decrease in available
Please cite this article in press as: Lu, D., et al. Speciation of Cu and Zn during composting of pig manure amended with rock phosphate. Waste Management (2014), http://dx.doi.org/10.1016/j.wasman.2014.04.008
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D. Lu et al. / Waste Management xxx (2014) xxx–xxx 50
A 45
P7.5
-1
Available P (mg kg )
-1
CK P2.5
10000
P5.0
40
Total P (g kg )
B 11000
CK P2.5
35 30 25 20
P5.0 P7.5
9000 8000 7000 6000 5000
15 4000 10 01
02
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0
01
02
Composting time (days) 45
C
04
05
0
60
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CK P2.5
35
P5.0
D Available P/Total P (%)
P7.5 30 25
C/P
03
Composting time (days)
20 15
55
CK P2.5
50
P5.0 P7.5
45 40 35 30 25
10 20 5 15 01
02
03
04
05
0
01
02
Composting time (days)
03
04
05
0
Composting time (days)
Fig. 2. Changes in (A) total P, (B) available P, (C) C/P ratio and (D) available P/total P during composting of pig manure amended with rock phosphate.
P/total P ratio could be due to the precipitation process, as available P would react with metal irons and form insoluble compound.
increased by 85%, 74% and 67% for Cu, Mn and Zn during composting of swine manure, while Singh and Kalamdhad (2013) found that the total contents of Cu, Mn and Zn increased by 5%, 9% and 29% during composting of green wastes. The composting materials have significant effects on metal condensation. The compost with OM could be easily degraded usually has a higher increment in the toxic metal concentration. The environmental impacts of particulate metal speciation are highly related to the behaviors of remobilization. Toxic metals in EXC and RED fractions are considered to be mobile and bioavailable, while the OXI and RES fractions are stable and non-bioavailable (Nomeda et al., 2008). In the initial compost mixtures in all treatments, the percentage distribution of different species of Cu followed the order: RED-Cu > EXC-Cu > OXI-Cu > RES-Cu (Fig. 4). During composting,
3.3. Distribution of Cu and Zn The evolution of total contents of Cu and Zn during composting is shown in Fig. 3. The compost mixture amended with RP had lower total metal contents. Addition of RP decreased the total metal contents with an increase in RP amendment level due to the dilution effect. During composting, total metal contents in all compost mixtures increased significantly which might be due to the mass loss via respiration and mineralization of OM. From the beginning to the end of composting, the total contents of Cu and Zn increased by 64.50–87.31% and 82.23–101.27%, respectively. Similarly, Hsu and Lo (2001) reported that toxic metal contents
A
400
B
CK P2.5
350
P5.0
300
P7.5
2250 2000
CK P2.5
1750
P5.0 P7.5
1500
Zn (mg kg )
-1
-1
Cu (mg kg )
250 200 150 100
1250 1000 750 500
50
250
0
0
1
7
15 23 31 Composting time (days)
39
49
1
7
15 23 31 Composting time (days)
39
49
Fig. 3. The evolution of total contents of (A) Cu and (B) Zn during composting of pig manure amended with rock phosphate.
Please cite this article in press as: Lu, D., et al. Speciation of Cu and Zn during composting of pig manure amended with rock phosphate. Waste Management (2014), http://dx.doi.org/10.1016/j.wasman.2014.04.008
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D. Lu et al. / Waste Management xxx (2014) xxx–xxx 100
A
B
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Cu distribution in P2.5 (%)
Cu distribution in CK (%)
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70 60 50 40 30 20 10
70 60 50 40 30 20 10
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Composting time (days) 100
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Cu distribution in P7.5 (%)
80
Cu distribution in P5.0 (%)
15
Composting time (days)
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70 60 50 40 30 20 10
0
0 1
7
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23
31
39
49
1
Composting time (days)
7
15
23
31
Composting time (days) EXC-Cu
RED-Cu
OXI-Cu
RES-Cu
Fig. 4. Sequential extraction of Cu during composting of pig manure amended with rock phosphate.
EXC-Cu and RED-Cu fractions decreased, while OXI-Cu and RES-Cu fractions increased. In the final composts, the percentage distribution order in the control treatment, P2.5 and P5.0 was RED-Cu > OXI-Cu > EXC-Cu > RES-Cu, while in P7.5 the order was OXI-Cu > RED-Cu > EXC-Cu > RES-Cu. Cu is strongly absorbed by humic substance (Farrell and Jones, 2009). The increase in the humification of organic carbon during composting may be responsible for the reduction in EXC-Cu and RED-Cu fractions and the increase in OXI-Cu fraction (Ingelmo et al., 2012). At the beginning of composting, the BF of Cu in the control treatment was significantly lower than that in RP amended compost, which agreed with the result found during co-composting of lime and sludge (Fang and Wong, 1999). The alkaline material addition could dissolve humic substance and thus reduce the OXI-Cu fraction and increase the BF of Cu in the initial compost mixture. The reduction in the BF of Cu during composting was 18.90% in the control treatment, compared with 29.62% in P2.5, 32.35% in P5.0 and 47.24% in P7.5. The composting process significantly reduced the mobile and bioavailable forms of Cu in the compost mixture which agreed with the results found by other researchers (Chen et al., 2010; Farrell and Jones, 2009). The reductions in EXC-Cu and RED-Cu fractions and increments in OXI-Cu and RES-Cu fractions during composting were significantly higher in RP amended compost mixture compared with no RP added compost mixture, which implied that addition of RP to the compost mixture could effectively advance the transformation of bioavailable form of Cu to more stable forms during composting. Addition of RP increased the proportion of OXI-Cu in the final composts with an increase in RP amendment level. As the stability constant of Cu complexes with OM is high, the organic bound fraction was reported as the major fraction of Cu in the compost by many researchers (Farrell and Jones, 2009; Hsu and Lo, 2001). Cai et al. (2007) reported that most of Cu was
converted to the OXI-Cu during composting and in the final compost the OXI-Cu accounted for more than 70% of total Cu. These implied that Cu has higher affinity for OM and addition of RP could accelerate the formation of OXI-Cu during composting. Compared with lime, RP was more suitable for immobilization Cu, as lime addition would reduce the formation of metal OM complexes during composting (Fang and Wong, 1999). Zinc was always abundant in pig manure and manure compost. Since Zn2+ can be expected to stay in ionic form in solution based on the redox potential for the redox reaction with other metal ions (Qiao and Ho, 1997), the EXC-Zn was dominated fraction in the compost mixture (Fig. 5). The high amount of EXC-Zn implied a great potential environmental threat as the EXC fraction represented the form with the highest mobility, the most readily bioavailable and thereby the most potentially toxic in soils (Cai et al., 2007). The EXC-Zn and RED-Zn fractions accounted for above 95% of total Zn in the composts which meant most of Zn was associated with the bioavailable fractions. Similarly, Nomeda et al. (2008) reported above 60% of Zn was associated with the mobile fractions in sewage sludge compost. Compared with OXI-Cu fraction, the OXI-Zn fraction in the composts was low, which meant the low stability constant of Zn complexes with OM. Similarly, Hernandez et al. (2006) found that the stability constants of Cu-HA complexes and the Cu complexing capacities of HAs were much larger than the corresponding values for Zn. During composting, EXC-Zn fraction decreased while RED-Zn fraction increased. The EXC-Zn fraction of the control treatment, P2.5, P5.0 and P7.5 decreased by 11.30%, 15.27%, 19.84% and 7.98%, respectively, from the initial to the final stage of the composting process, while the RED-Zn fraction of the control treatment, P2.5, P5.0 and P7.5 increased by 11.94%, 15.86%, 21.05% and 7.34%, respectively. In the mature compost, most of Zn was still in EXC and RED
Please cite this article in press as: Lu, D., et al. Speciation of Cu and Zn during composting of pig manure amended with rock phosphate. Waste Management (2014), http://dx.doi.org/10.1016/j.wasman.2014.04.008
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D. Lu et al. / Waste Management xxx (2014) xxx–xxx
A
100
B
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Zn distribution in P2.5 (%)
Zn distribution in CK (%)
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1
Composting time (days)
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15
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Composting time (days) EXC-Zn
RED-Zn
OXI-Zn
RES-Zn
Fig. 5. Sequential extraction of Zn during composting of pig manure amended with rock phosphate.
fractions which meant the BF of Zn changed a little throughout the composting. The composting process converted the EXC-Zn fraction to RED-Zn fraction, which agreed to the result reported by Farrell and Jones (2009) during composting of municipal solid waste, but contrasted with the result reported by He et al. (2009) during composting of sewage sludge. He et al., found that during composting, RED-Zn and OXI-Zn fractions would be transformed to EXC fraction and thus the Zn mobility increased. The differences meant that the speciation of Zn during composting depended on the raw compost materials used. As Zn has relatively high affinity for sorption on the surfaces of Fe and Mn oxides (RED form), the increase in pH during composting might be responsible for the decrease in EXC-Zn fraction and increase in RED-Zn fraction (Zheljazkov and Warman, 2004). Compared with the control treatment, the compost mixtures amended with RP had a higher reduction in EXC-Zn fraction and a higher increment in RED-Zn fraction, except in P7.5 pile. The results implied that addition of an appropriate amount of RP (5%) could enhance the conversion of EXC-Zn to RED-Zn fraction. The formation of Zn phosphates with low solubility might be responsible for the decrease in EXC-Zn fraction in RP amended compost (Cajuste et al., 2006). The distribution of Cu and Zn in the various fractions by sequential extraction during composting revealed that the potential mobility of Zn was higher than Cu in the pig manure compost. RP has higher affinity for Cu than Zn (Cao et al., 2004). Addition of RP could reduce the BF of Cu and EXC fraction of Zn compared to the control treatment during composting. RP has been proved to be effective to immobilize toxic metals such as Pb, Cu, Zn from various metals contaminated soils (Cajuste et al., 2006). Cao et al. (2004) summarized that the possible mechanisms for metal retention by RP in contaminated waters and soils included (1) ion exchange processes at the surface of RP,
(2) surface complexation, (3) precipitation of some amorphous to poorly crystalline, mixed metal phosphates, and (4) substitution of Ca in PR by other metals during recrystallization. Usually, soluble phosphates, such as diammonium phosphate could greatly reduce toxic metals in mobile fraction by forming metal phosphate precipitates (McGowen et al., 2001). Apparently, the low solubility of RP limited its ability to reduce soluble toxic metals. However, the organic acid and weak carbonic acid formed during composting could dissolve the RP and thus provide free phosphate ions 2– (H2PO1– 4 and HPO4 ) in the solution which could facilitate the formation of metal phosphates and thereby metal immobilization in the RP amended compost. Similarly, Cajuste et al. (2006) found that application of acidulated RP to soil could significantly reduce metal mobility and bioavailability because of the free phosphate from the dissolution of RP. The decrease in available P/total P during composting meant that some available P reacted with metal ions and formed precipitation. 3.4. Pearson correlation between the EXC fraction, BF, pH and OM The correlation of EXC fraction or BF of Cu and Zn with pH and OM were investigated to determine the influence of pH evolution and OM degradation on the changes of the metal speciation (Table 2). The pH did not significantly affect the EXC fraction or the BF of the metals in the control treatment. However, the pH significantly correlated with the EXC-Cu and EXC-Zn fraction in P2.5 (R = 0.816* and R = 0.939**, respectively) and P5.0 (R = 0.830* and R = 0.931**, respectively), and highly correlated with the BF of Cu in P2.5 (R = 0.882*), P5.0 (R = 0.912**) and P7.5 (R = 0.825*). The correlation between pH and BF of Zn was low. The OM significantly correlated with EXC-Cu fraction in P2.5 (R = 0.835*) and P5.0 (R = 0.931**), and highly correlated with the
Please cite this article in press as: Lu, D., et al. Speciation of Cu and Zn during composting of pig manure amended with rock phosphate. Waste Management (2014), http://dx.doi.org/10.1016/j.wasman.2014.04.008
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Table 2 Pearson correlation coefficients of exchangeable (EXC) fraction and bioavailability factor (BF) of Cu and Zn with pH and organic matter (OM) during composting for all treatments. CK pH EXC-Cu BF-Cu EXC-Zn BF-Zn * **
0.160 0.301 0.011 0.552
P2.5 OM 0.531 0.806* 0.773* 0.485
pH 0.816* 0.882** 0.939** 0.477
P5.0 OM
pH
0.835* 0.978** 0.943** 0.735
0.830* 0.912** 0.931** 0.810*
P7.5 OM 0.931** 0.989** 0.987** 0.870*
pH 0.381 0.825* 0.407 0.218
OM 0.689 0.978** 0.763* 0.431
Statistically significant at the probability level 0.05 (2-tailed). Statistically significant at the probability level 0.01 (2-tailed).
BF of Cu in all treatments. The correlation between OM and EXC-Zn was well in all treatments, while the correlation between OM and BF of Zn was low. Significant relationships between pH and EXC-Cu fraction, BF of Cu and EXC-Zn fraction were found in RP amended compost but not in the control treatment. The processes of sorption, precipitation and coprecipitation are pH dependent (Cao et al., 2004). The increase in pH during composting in RP amended composts was an additional mechanism for the reduction in metal bioavailability (Chen et al., 2007). The increase in pH would enhance the complexation between toxic metals and RP (Cao et al., 2004). Furthermore, the increase in pH would accelerate the formation of oxides (RED form), metal-carbonate precipitates, and other complexes that would decrease metal solubility and bioavailability (Mench et al., 2006). The relationship between OM and BF of Cu, EXC-Zn fraction implied that the OM degradation process significantly influenced the metal bioavailability and mobility. The humic substance formed during OM degradation could react with metal irons and thus reduce the bioavailability of the toxic metals (Ingelmo et al., 2012). Several researchers have reported that BF of toxic metal was well dependent on the OM concentration (Liu et al., 2007). 4. Conclusions Addition of RP in compost affects the speciation of toxic metals through increasing the pH, reacting with metal ions and providing available adsorption sites. RP addition significantly reduced the contents of Cu and Zn in the compost mixture. During composting, total metal concentration increased due to the mass loss of the compost. Composting process affected the metal speciation. During composting, EXC-Cu and RED-Cu fractions decreased while OXI-Cu and RED-Cu fractions increased, which meant the bioavailability of Cu decreased. Most of Cu was transformed to OXI-form after the composting process and RP addition advanced the transformation. Zinc was found abundant and mainly in bioavailable form in the compost mixture. During composting, EXC-Zn fraction decreased while RED-Zn fraction increased. However, the BF of Zn did not change much during composting. Addition an appropriate amount of RP (5%) could enhance the transformation of EXC-Zn to RED-Zn fraction. Acknowledgements This work was financially supported by the Major Science and Technology Program for Water Pollution Control and Treatment (2012ZX07201004) and Jilin Provincial Research Foundation for Basic Research, China (201105033). References Ben Achiba, W., Lakhdar, A., Cabteni, N., Du Laing, G., Verloo, M., Boeckx, P., Van Cleemput, O., Jedidi, N., Gallali, T., 2010. Accumulation and fractionation of trace metals in a Tunisian calcareous soil amended with farmyard manure and municipal solid waste compost. J. Hazard. Mater. 176, 99–108.
Bernal, M.P., Alburquerque, J.A., Moral, R., 2009. Composting of animal manures and chemical criteria for compost maturity assessment. A review. Bioresour. Technol. 100, 5444–5453. Biswas, D.R., Narayanasamy, G., 2006. Rock phosphate enriched compost: an approach to improve low-grade Indian rock phosphate. Bioresour. Technol. 97, 2243–2251. Bremner, J.M., 1996. Methods of Soil Analysis. Part 3: Chemical Methods. SSSA, Madison. Cai, Q.Y., Mo, C.H., Wu, Q.T., Zeng, Q.Y., Katsoyiannis, A., 2007. Concentration and speciation of heavy metals in six different sewage sludge-composts. J. Hazard. Mater. 147, 1063–1072. Cajuste, L.J., Cajuste, L., Garcia-O, C., Cruz-D, J., 2006. Distribution and availability of heavy metals in raw and acidulated phosphate rock-amended soils. Commum. Soil Sci. Plan. 37, 2541–2552. Cang, L., Wang, Y.J., Zhou, D.M., Dong, Y.H., 2004. Heavy metals pollution in poultry and livestock feeds and manures under intensive farming in Jiangsu Province, China. J. Environ. Sci. – China 16, 371–374. Cao, X.D., Ma, L.Q., Rhue, D.R., Appel, C.S., 2004. Mechanisms of lead, copper, and zinc retention by phosphate rock. Environ. Pollut. 131, 435–444. Chen, S.B., Xu, M.G., Ma, Y.B., Yang, J.C., 2007. Evaluation of different phosphate amendments on availability of metals in contaminated soil. Ecotoxicol. Environ. Saf. 67, 278–285. Chen, Y.X., Huang, X.D., Han, Z.Y., Huang, X., Hu, B., Shi, D.Z., Wu, W.X., 2010. Effects of bamboo charcoal and bamboo vinegar on nitrogen conservation and heavy metals immobility during pig manure composting. Chemosphere 78, 1177– 1181. Fang, M., Wong, J.W.C., 1999. Effects of lime amendment on availability of heavy metals and maturation in sewage sludge composting. Environ. Pollut. 106, 83– 89. Farrell, M., Jones, D.L., 2009. Heavy metal contamination of a mixed waste compost: metal speciation and fate. Bioresour. Technol. 100, 4423–4432. Gomez-Brandon, M., Lazcano, C., Dominguez, J., 2008. The evaluation of stability and maturity during the composting of cattle manure. Chemosphere 70, 436– 444. Hahladakis, J., Smaragdaki, E., Vasilaki, G., Gidarakos, E., 2013. Use of sediment quality guidelines and pollution indicators for the assessment of heavy metal and PAH contamination in Greek surficial sea and lake sediments. Environ. Monit. Assess. 185, 2843–2853. He, M.M., Tian, G.M., Liang, X.Q., 2009. Phytotoxicity and speciation of copper, zinc and lead during the aerobic composting of sewage sludge. J. Hazard. Mater. 163, 671–677. Hernandez, D., Plaza, C., Senesi, N., Polo, A., 2006. Detection of copper(II) and zinc(II) binding to humic acids from pig slurry and amended soils by fluorescence spectroscopy. Environ. Pollut. 143, 212–220. Hsu, J.H., Lo, S.L., 1999. Chemical and spectroscopic analysis of organic matter transformations during composting of pig manure. Environ. Pollut. 104, 189– 196. Hsu, J.H., Lo, S.L., 2001. Effect of composting on characterization and leaching of copper, manganese, and zinc from swine manure. Environ. Pollut. 114, 119– 127. Huang, G.F., Wong, J.W.C., Wu, Q.T., Nagar, B.B., 2004. Effect of C/N on composting of pig manure with sawdust. Waste Manage. 24, 805–813. Ingelmo, F., Molina, M.J., Soriano, M.D., Gallardo, A., Lapena, L., 2012. Influence of organic matter transformations on the bioavailability of heavy metals in a sludge based compost. J. Environ. Manage. 95, S104–S109. Iqbal, M.K., Shafiq, T., Hussain, A., Ahmed, K., 2010. Effect of enrichment on chemical properties of MSW compost. Bioresour. Technol. 101, 5969–5977. Jones, J.B., Case, V.W., 1990. Soil Testing and Plant Analysis. SSSA, Madison. Kolawole, G.O., Tian, G., 2007. Phosphorus fractionation and crop performance on an alfisol amended with phosphate rock combined with or without plant residues. Afr. J. Biotechnol. 6, 1972–1978. Liu, Y.S., Ma, L.L., Li, Y.Q., Zheng, L.T., 2007. Evolution of heavy metal speciation during the aerobic composting process of sewage sludge. Chemosphere 67, 1025–1032. Lu, D.A., Yan, B.X., Wang, L.X., Deng, Z.Q., Zhang, Y.B., 2013. Changes in phosphorus fractions and nitrogen forms during composting of pig manure with rice straw. J. Integr. Agr. 12, 1855–1864. McGowen, S.L., Basta, N.T., Brown, G.O., 2001. Use of diammonium phosphate to reduce heavy metal solubility and transport in smelter-contaminated soil. J. Environ. Qual. 30, 493–500.
Please cite this article in press as: Lu, D., et al. Speciation of Cu and Zn during composting of pig manure amended with rock phosphate. Waste Management (2014), http://dx.doi.org/10.1016/j.wasman.2014.04.008
8
D. Lu et al. / Waste Management xxx (2014) xxx–xxx
Mench, M., Vangronsveld, J., Lepp, N., Bleeker, P., Ruttens, A., Geebelen, W., 2006. Phytostabilisation of metal-contaminated sites. In: Echevarria, G., Morel, J.L., Goncharova, N. (Eds.), Phytoremediation of Metal-Contaminated Soils, NATO Science Series, vol. 68. Springer, Netherlands, pp. 109–190. Nemati, K., Abu Bakar, N.K., Abas, M.R., Sobhanzadeh, E., 2011. Speciation of heavy metals by modified BCR sequential extraction procedure in different depths of sediments from Sungai Buloh, Selangor, Malaysia. J. Hazard. Mater. 192, 402– 410. Nomeda, S., Valdas, P., Chen, S.Y., Lin, J.G., 2008. Variations of metal distribution in sewage sludge composting. Waste Manage. 28, 1637–1644. Qiao, L., Ho, G., 1997. The effects of clay amendment and composting on metal speciation in digested sludge. Water Res. 31, 951–964. Richardson, A.E., Hocking, P.J., Simpson, R.J., George, T.S., 2009. Plant mechanisms to optimise access to soil phosphorus. Crop Pasture Sci. 60, 124–143. Satisha, G.C., Devarajan, L., 2007. Effect of amendments on windrow composting of sugar industry pressmud. Waste Manage. 27, 1083–1091. Sinegani, A.A.S., Hosseinpur, A., 2010. Evaluation of effect of different sterilization methods on soil biomass phosphorus extracted with NaHCO3. Plant Soil Environ. 56, 156–162. Singh, J., Kalamdhad, A.S., 2013. Assessment of bioavailability and leachability of heavy metals during rotary drum composting of green waste (Water hyacinth). Ecol. Eng. 52, 59–69. Tack, F.M.G., Verloo, M.G., 1995. Chemical speciation and fractionation in soil and sediment heavy-metal analysis – a review. Int. J. Environ. Anal. Chem. 59, 225– 238.
Tsai, L.J., Yu, K.C., Chen, S.F., Kung, P.Y., Chang, C.Y., Lin, C.H., 2003. Partitioning variation of heavy metals in contaminated river sediment via bioleaching: effect of sulfur added to total solids ratio. Water Res. 37, 4623–4630. Verma, S.L., Penfold, C., Marschner, P., 2013. Mobilisation of rock phosphate by surface application of compost. Biol. Fertil. Soils 49, 287–294. Wang, H., Dong, Y.H., Yang, Y.Y., Toor, G.S., Zhang, X.M., 2013. Changes in heavy metal contents in animal feeds and manures in an intensive animal production region of China. J. Environ. Sci. – China 25, 2435–2442. Wong, J.W.C., Selvam, A., 2006. Speciation of heavy metals during co-composting of sewage sludge with lime. Chemosphere 63, 980–986. Zayed, G., Abdel-Motaal, H., 2005. Bio-production of compost with low pH and high soluble phosphorus from sugar cane bagasse enriched with rock phosphate. World J. Microbiol. Biotechnol. 21, 747–752. Zhang, F.S., Li, Y.X., Yang, M., Li, W., 2012. Content of heavy metals in animal feeds and manures from farms of different scales in northeast China. Int. J. Environ. Res. Pub. Health 9, 2658–2668. Zheljazkov, V.D., Warman, P.R., 2004. Phytoavailability and fractionation of copper, manganese, and zinc in soil following application of two composts to four crops. Environ. Pollut. 131, 187–195. Zmora-Nahum, S., Markovitch, O., Tarchitzky, J., Chen, Y.N., 2005. Dissolved organic carbon (DOC) as a parameter of compost maturity. Soil Biol. Biochem. 37, 2109– 2116. Zorpas, A.A., Inglezakis, V.J., Loizidou, M., 2008. Heavy metals fractionation before, during and after composting of sewage sludge with natural zeolite. Waste Manage. 28, 2054–2060.
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Speciation of Cu and Zn during composting of pig manure amended with rock phosphate Duian Lu a,b, Lixia Wang a,⇑, Baixing Yan a, Yang Ou a, Jiunian Guan a,b, Yu Bian a,b, Yubin Zhang c a
Key Laboratory of Wetland Ecology and Environment, Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Changchun 130102, PR China University of Chinese Academy of Sciences, Beijing 100049, PR China c College of Plant Science, JiLin University, Changchun 130062, PR China b
a r t i c l e
i n f o
Article history: Received 15 January 2014 Accepted 4 April 2014 Available online xxxx Keywords: Toxic metal Pig manure Composting Rock phosphate
a b s t r a c t Pig manure usually contains a large amount of metals, especially Cu and Zn, which may limit its land application. Rock phosphate has been shown to be effective for immobilizing toxic metals in toxic metals contaminated soils. The aim of this study work was to investigate the effect of rock phosphate on the speciation of Cu and Zn during co-composting of pig manure with rice straw. The results showed that composting process and rock phosphate addition significantly affected the changes of metal species. During co-composting, the exchangeable and reducible fractions of Cu were transformed to organic and residue fractions, thus the bioavailable Cu fractions were decreased. The rock phosphate addition enhanced the metal transformation depending on the level of rock phosphate amendment. Zinc was found in the exchangeable and reducible fractions in the compost. The bioavailable Zn fraction changed a little during the composting process. The composting process converted the exchangeable Zn fraction into reducible fraction. Addition of an appropriate amount (5.0%) of rock phosphate could advance the conversion. Rock phosphate could reduce metal availability through adsorption and complexation of the metal ions on inorganic components. The increase in pH and organic matter degradation could be responsible for the reduction in exchangeable and bioavailable Cu fractions and exchangeable Zn fraction in rock phosphate amended compost. Ó 2014 Elsevier Ltd. All rights reserved.
1. Introduction The intensive and industrial livestock production generates large amounts of pig manure in China and has led to inappropriate disposal practices when it is used as an organic fertilizer (Chen et al., 2010). Continuous agricultural utilization of pig manure may pose environmental problems, such as water contamination, odor pollution and soil accumulation of toxic metals (GomezBrandon et al., 2008; Lu et al., 2013). The environmental problems have given rise to the need for environmentally sound and economically feasible technologies for treating pig manure before application to agricultural lands (Chen et al., 2010). Composting pig manure may provide a better alternative for manure management. Composting is a spontaneous biological decomposition process of organic materials in a predominantly aerobic environment (Bernal et al., 2009). During composting, the organic materials are degraded into full mineralized materials such as CO2, H2O, mineral ions, stabilized organic matter (OM) and ash, resulting in a net loss ⇑ Corresponding author. Tel.: +86 431 85542325; fax: +86 431 85542260. E-mail address: [email protected] (L. Wang).
of total OM and a concentration of inorganic constituents. Thus, composting could reduce the volume and weight of the raw materials. As the compost product is stable and usually contains large amounts of nutrients, it could be applied to agricultural lands as valuable fertilizer and soil amendment (Bernal et al., 2009). Several researchers have shown that pig manure may contain higher concentrations of Cu and Zn than other metals, because of feed additives in livestock production (Cang et al., 2004; Wang et al., 2013; Zhang et al., 2012). It is common practice to add minerals such as Cu and Zn to animal feeds via mineral additives because of their antimicrobial and growth-stimulating effects (Zhang et al., 2012). Consequently, successive application of pig manure to agricultural lands may be noxious to soils, plants, and human health. Toxic metals uptake by plant will lead to accumulation in human tissues and cause adverse effects on human health via food chain. Focus on the improvement of the composting process to reduce the availability of toxic metals using various minerals is attracting the attention of researchers. The effects of additives on composting have been intensely studied. Wong and Selvam (2006) found that co-composting of sewage sludge with lime could significantly reduce the availability of toxic metals in
http://dx.doi.org/10.1016/j.wasman.2014.04.008 0956-053X/Ó 2014 Elsevier Ltd. All rights reserved.
Please cite this article in press as: Lu, D., et al. Speciation of Cu and Zn during composting of pig manure amended with rock phosphate. Waste Management (2014), http://dx.doi.org/10.1016/j.wasman.2014.04.008
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the final composts, as well as pathogens. Natural zeolite and clinptilolite have been proved to be a suitable material for toxic metals immobilization during composting of sewage sludge (Zorpas et al., 2008). The industrial waste by-product (red mud) has been reported as a useful amendment in reducing metal leachability and plant availability in sludge compost (Qiao and Ho, 1997). However, information on the metal speciation during co-composting of pig manure with rock phosphate (RP) has not been well reported. Phosphorus deficiency is a major limiting factor in the majority of soils for crop production (Richardson et al., 2009). Using RP as fertilizer to overcome P deficiency was repeatedly reported (Kolawole and Tian, 2007). The direct use of RP is limited by its poor solubility, especially in alkaline soils (Verma et al., 2013). Addition of RP into composts could enhance the nutrient value of the compost. Furthermore, the composting process will help to accelerate the mobilization of unavailable P in RP, which in turn will help in supplying P to crops (Zayed and Abdel-Motaal, 2005). RP has been demonstrated to be a good chemical amendment for reducing metal bioavailability in situ remediation in toxic metals contaminated soils (Cajuste et al., 2006; Chen et al., 2007). Total metal concentration is an important indicator of pollution risks, but it provides little or no indication of their specific bioavailability or mobility (Tack and Verloo, 1995). The knowledge of metal speciation may be useful to assess the potential environmental effects as metal associated with different fractions have different impacts on the environment (Ben Achiba et al., 2010). The sequential extraction procedure could provide the understanding of the natures of metal fractions and allow the prediction of metal mobility or bioavailability (Hahladakis et al., 2013; Tsai et al., 2003). The present study aimed at evaluating the effect of the addition of RP on the speciation of Cu and Zn during co-composting of pig manure with rice straw. Parameters such as pH, OM were determined in order to investigate the correlation between the exchangeable and bioavailable metals and the parameters for different treatments. 2. Materials and methods 2.1. Experimental procedure There were four different treatments in the study. Rice straw was used as a bulking agent for adjusting the C/N ratio of the pig manure to a value of 20. The compost mixture (about 30 kg each, fresh weight) was then mixed thoroughly with RP (particle diameter <0.149 mm) at 0% (CK), 2.5% (P2.5), 5.0% (P5.0), 7.5% (P7.5) (w/w, dry weight basis). Composting was conducted in a bin with a volume of 98L. Moisture content of the stock material was initially adjusted to about 70% and was then maintained at the same level by adding necessary deionized water during composting. The compost piles were turned and mixed every two days throughout the composting process for aeration. Temperature was recorded daily using a thermometer at the center of the compost piles. The composting lasted 49 days and triplicate independent samples were taken during the composting time (on day 1, 7, 15, 23, 31, 39, 49). The compost samples were air dried, ground and sieved to <0.25 mm for further analyses. The physicochemical properties of the experimental raw materials are shown in Table 1. 2.2. Chemical analysis pH and electrical conductivity (EC) were measured in water extracts at 1:10 (w/v) (He et al., 2009). Ash content was determined by combustion at 550 °C for 8 h. Organic matter was determined by subtraction of ash content. Total organic carbon
Table 1 Physicochemical properties of the experimental raw materials (dry matter basis).a
a b c
Parameter
Pig manure
Rice straw
Rock phosphate
pH EC (dS m 1) Total N (g kg 1) Total P (g kg 1) Organic matter (g kg Cu (mg kg 1) Zn (mg kg 1)
7.10 ± 0.01 3.65 ± 0.01 31.49 ± 0.62 15.80 ± 0.23 806.03 ± 3.73 453.66 ± 2.33 3401.25 ± 44.20
7.03 ± 0.01 3.01 ± 0.02 11.42 ± 0.01 3.63 ± 0.10 886.86 ± 9.92 99.75 ± 32.17 492.75 ± 119.14
9.46 ± 0.01 0.99 ± 0.05 NDb 366.18 ± 14.23 NDb TQc 63.48 ± 0.01
1
)
Values (mean ± standard) are the averages of three replicates. Not detected. Trace quantity.
was calculated as 58% of OM (Zmora-Nahum et al., 2005). Total N and P contents in the composts were determined by Kjeldhal digestion and analysed by indophenols-blue method for NH+4 and ascorbic acid method for PO34 (Bremner, 1996). Available P was determined using NaHCO3 (Sinegani and Hosseinpur, 2010). Total toxic metal was determined using atomic absorption spectrophotometry (AAS) (GBC 932, Australian) after digestion with concentrated HNO3 and HClO4 (Jones and Case, 1990). The modified BCR sequential extraction method was carried out for the sequential extraction of Cu and Zn (Nemati et al., 2011). In the modified BCR procedure, all toxic metals are partitioned into four operationally defined fractions: exchangeable (EXC), reducible (RED), oxidizable (OXI) and residual (RES). The EXC fraction was extracted with 40 ml of 0.11 M CH3COOH by shaking the sample for 16 h at room temperature. The RED fraction in the second step was extracted with 40 ml of 0.5 M NH2OHHCl (adjusted to pH 1.5 with concentrated HNO3) by shaking the residue from the previous step for 16 h at room temperature. To extract the OXI fraction, the residue from the second step was digested with 10 ml of H2O2 for 1 h at room temperature. It was then heated to near dryness in a water bath at 85 °C. An additional 10 ml of H2O2 was added and heated to near dryness again. After cooling, 50 ml of 1.0 M ammonium acetate was added to the residue and shaken for 16 h at room temperature. The RES fraction was obtained by digestion the residue from the third step with aquaregia and HF. The supernatant from each extraction was analyzed by AAS (GBC 932, Australian). The bioavailability factor (BF) of Cu and Zn was defined as the ratio of the metal content in EXC and RED fractions to the total metal content (Nomeda et al., 2008). 2.3. Statistical analysis All the figures were performed using OrginPro 8.0. Statistical analysis was performed using SPSS 16.0. Pearson correlation was investigated between the EXC fraction, the BF and selected variables: pH and OM. 3. Results and discussion 3.1. Changes in temperature, pH, EC and C/N ratio The evolutions of temperature were found similarly among the different compost piles (Fig. 1A). The temperature increased rapidly to above 50 °C in the initial 4 days and maintained at the thermophilic phase for nearly one week. Then the temperature decreased and reached ambient temperature on day 31. The similar temperature profile showed that the RP addition did not affect the metabolic activity of microbes. The changes in the pH of the composts are shown in Fig. 1B. In the control treatment, pH increased from 8.35 to 8.75 on day 7 and
Please cite this article in press as: Lu, D., et al. Speciation of Cu and Zn during composting of pig manure amended with rock phosphate. Waste Management (2014), http://dx.doi.org/10.1016/j.wasman.2014.04.008
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9.8 9.6 9.4 9.2
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Fig. 1. Changes in (A) temperature, (B) pH, (C) EC and (D) C/N ratio during composting of pig manure amended with rock phosphate.
then decreased to 8.46 at the end of composting. A similar pH trend was found by other researchers during composting (Huang et al., 2004). But in the RP amended composts, pH showed increase at the beginning and reached plateau value on day 31, 23, 7 for P2.5, P5.0 and P7.5, respectively. The increase in pH during the initial stage of composting was mainly because of the degradation of organic acid or release of ammonia compounds, while the decrease in the pH of the composts in the later phase was likely to be a consequence of new synthesis of organic acids and production of phenolic compounds (Satisha and Devarajan, 2007). At the beginning of composting, the pH in the control and RP amended compost was almost the same, which could be due to the buffering effect of the humic substance in the RP amended compost mixture (Hsu and Lo, 1999). Thereafter, the compost mixtures amended with RP showed higher pH than the control treatment and there was no decrease of pH found in the RP amended composts, which might be due to the release of bases from the RP. The dynamics of pH in RP amended compost agreed with the results found during composting of municipal solid waste amended with RP, FeSO4 and lime (Iqbal et al., 2010). These implied that alkaline material addition such as RP and lime provided buffering against the decrease in pH. The changes in EC for all treatments followed the same trend (Fig. 1C). There was a little decrease in EC at the initial 7 days which could be due to the precipitation of mineral ions. Then the EC increased as a consequence of concentration effect and release of mineral salts due to the fierce OM degradation. Addition of RP decreased the EC to low degrees in the composts with an increase in RP amendment level. In all compost mixtures, the C/N ratio increased at the initial 7 days and then decreased thereafter (Fig. 1D). The increase in C/N ratio could be due to the nitrogen losses which were usually found serious at the beginning of composting, while the decrease in C/N ratio could be due to the mineralization of the OM.
3.2. Changes in total P, available P and C/P ratio The compost mixture amended with RP had significantly higher content of total P as compared to the control treatment (Fig. 2A). However, addition of RP reduced the available P content due to the poor solubility of RP and dilution effect (Fig. 2B). The reaction of soluble P with other components (e.g. CaCO3) might also be responsible for the reduction in available P content in the compost. Similarly, Biswas and Narayanasamy (2006) reported that the addition of RP significantly reduced water soluble P content during composting of straw. During composting, significant increases in total P content were obtained in all compost mixtures. The total P content of the control treatment increased from 12.19 g kg 1 in the raw compost mixture to 24.88 g kg 1 in the mature compost, indicating 2.04 times enrichment of P during the composting process, while the total P content of P2.5, P5.0 and P7.5 increased from 18.87 g kg 1, 22.75 g kg 1, 28.01 g kg 1 to 31.81 g kg 1, 41.64 g kg 1, 47.04 g kg 1, respectively, indicating 1.68–1.83 times enrichment of P. The increase of total P was mainly caused by the concentration effect due to the degradation of OM. The C/P ratio decreased significantly during composting process in all compost mixture due to the OM decomposition (Fig. 2C). The available P/total P ratio had an increasing trend during the initial days of composting, but showed decrease in the mature compost (Fig. 2D). The increase in available P/total P ratio at the beginning could be due to the release of available P during the OM degradation. In RP amended compost, the CO2 evolved and organic acid released during decomposition of OM would be responsible for the increase in available P/total P ratio. The organic acid and weak carbonic acid formed by CO2 could dissolve RP and increase the available P content in RP amended compost during composting (Biswas and Narayanasamy, 2006). The decrease in available
Please cite this article in press as: Lu, D., et al. Speciation of Cu and Zn during composting of pig manure amended with rock phosphate. Waste Management (2014), http://dx.doi.org/10.1016/j.wasman.2014.04.008
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A 45
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Fig. 2. Changes in (A) total P, (B) available P, (C) C/P ratio and (D) available P/total P during composting of pig manure amended with rock phosphate.
P/total P ratio could be due to the precipitation process, as available P would react with metal irons and form insoluble compound.
increased by 85%, 74% and 67% for Cu, Mn and Zn during composting of swine manure, while Singh and Kalamdhad (2013) found that the total contents of Cu, Mn and Zn increased by 5%, 9% and 29% during composting of green wastes. The composting materials have significant effects on metal condensation. The compost with OM could be easily degraded usually has a higher increment in the toxic metal concentration. The environmental impacts of particulate metal speciation are highly related to the behaviors of remobilization. Toxic metals in EXC and RED fractions are considered to be mobile and bioavailable, while the OXI and RES fractions are stable and non-bioavailable (Nomeda et al., 2008). In the initial compost mixtures in all treatments, the percentage distribution of different species of Cu followed the order: RED-Cu > EXC-Cu > OXI-Cu > RES-Cu (Fig. 4). During composting,
3.3. Distribution of Cu and Zn The evolution of total contents of Cu and Zn during composting is shown in Fig. 3. The compost mixture amended with RP had lower total metal contents. Addition of RP decreased the total metal contents with an increase in RP amendment level due to the dilution effect. During composting, total metal contents in all compost mixtures increased significantly which might be due to the mass loss via respiration and mineralization of OM. From the beginning to the end of composting, the total contents of Cu and Zn increased by 64.50–87.31% and 82.23–101.27%, respectively. Similarly, Hsu and Lo (2001) reported that toxic metal contents
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-1
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250 200 150 100
1250 1000 750 500
50
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0
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Fig. 3. The evolution of total contents of (A) Cu and (B) Zn during composting of pig manure amended with rock phosphate.
Please cite this article in press as: Lu, D., et al. Speciation of Cu and Zn during composting of pig manure amended with rock phosphate. Waste Management (2014), http://dx.doi.org/10.1016/j.wasman.2014.04.008
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Composting time (days) EXC-Cu
RED-Cu
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Fig. 4. Sequential extraction of Cu during composting of pig manure amended with rock phosphate.
EXC-Cu and RED-Cu fractions decreased, while OXI-Cu and RES-Cu fractions increased. In the final composts, the percentage distribution order in the control treatment, P2.5 and P5.0 was RED-Cu > OXI-Cu > EXC-Cu > RES-Cu, while in P7.5 the order was OXI-Cu > RED-Cu > EXC-Cu > RES-Cu. Cu is strongly absorbed by humic substance (Farrell and Jones, 2009). The increase in the humification of organic carbon during composting may be responsible for the reduction in EXC-Cu and RED-Cu fractions and the increase in OXI-Cu fraction (Ingelmo et al., 2012). At the beginning of composting, the BF of Cu in the control treatment was significantly lower than that in RP amended compost, which agreed with the result found during co-composting of lime and sludge (Fang and Wong, 1999). The alkaline material addition could dissolve humic substance and thus reduce the OXI-Cu fraction and increase the BF of Cu in the initial compost mixture. The reduction in the BF of Cu during composting was 18.90% in the control treatment, compared with 29.62% in P2.5, 32.35% in P5.0 and 47.24% in P7.5. The composting process significantly reduced the mobile and bioavailable forms of Cu in the compost mixture which agreed with the results found by other researchers (Chen et al., 2010; Farrell and Jones, 2009). The reductions in EXC-Cu and RED-Cu fractions and increments in OXI-Cu and RES-Cu fractions during composting were significantly higher in RP amended compost mixture compared with no RP added compost mixture, which implied that addition of RP to the compost mixture could effectively advance the transformation of bioavailable form of Cu to more stable forms during composting. Addition of RP increased the proportion of OXI-Cu in the final composts with an increase in RP amendment level. As the stability constant of Cu complexes with OM is high, the organic bound fraction was reported as the major fraction of Cu in the compost by many researchers (Farrell and Jones, 2009; Hsu and Lo, 2001). Cai et al. (2007) reported that most of Cu was
converted to the OXI-Cu during composting and in the final compost the OXI-Cu accounted for more than 70% of total Cu. These implied that Cu has higher affinity for OM and addition of RP could accelerate the formation of OXI-Cu during composting. Compared with lime, RP was more suitable for immobilization Cu, as lime addition would reduce the formation of metal OM complexes during composting (Fang and Wong, 1999). Zinc was always abundant in pig manure and manure compost. Since Zn2+ can be expected to stay in ionic form in solution based on the redox potential for the redox reaction with other metal ions (Qiao and Ho, 1997), the EXC-Zn was dominated fraction in the compost mixture (Fig. 5). The high amount of EXC-Zn implied a great potential environmental threat as the EXC fraction represented the form with the highest mobility, the most readily bioavailable and thereby the most potentially toxic in soils (Cai et al., 2007). The EXC-Zn and RED-Zn fractions accounted for above 95% of total Zn in the composts which meant most of Zn was associated with the bioavailable fractions. Similarly, Nomeda et al. (2008) reported above 60% of Zn was associated with the mobile fractions in sewage sludge compost. Compared with OXI-Cu fraction, the OXI-Zn fraction in the composts was low, which meant the low stability constant of Zn complexes with OM. Similarly, Hernandez et al. (2006) found that the stability constants of Cu-HA complexes and the Cu complexing capacities of HAs were much larger than the corresponding values for Zn. During composting, EXC-Zn fraction decreased while RED-Zn fraction increased. The EXC-Zn fraction of the control treatment, P2.5, P5.0 and P7.5 decreased by 11.30%, 15.27%, 19.84% and 7.98%, respectively, from the initial to the final stage of the composting process, while the RED-Zn fraction of the control treatment, P2.5, P5.0 and P7.5 increased by 11.94%, 15.86%, 21.05% and 7.34%, respectively. In the mature compost, most of Zn was still in EXC and RED
Please cite this article in press as: Lu, D., et al. Speciation of Cu and Zn during composting of pig manure amended with rock phosphate. Waste Management (2014), http://dx.doi.org/10.1016/j.wasman.2014.04.008
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Composting time (days) EXC-Zn
RED-Zn
OXI-Zn
RES-Zn
Fig. 5. Sequential extraction of Zn during composting of pig manure amended with rock phosphate.
fractions which meant the BF of Zn changed a little throughout the composting. The composting process converted the EXC-Zn fraction to RED-Zn fraction, which agreed to the result reported by Farrell and Jones (2009) during composting of municipal solid waste, but contrasted with the result reported by He et al. (2009) during composting of sewage sludge. He et al., found that during composting, RED-Zn and OXI-Zn fractions would be transformed to EXC fraction and thus the Zn mobility increased. The differences meant that the speciation of Zn during composting depended on the raw compost materials used. As Zn has relatively high affinity for sorption on the surfaces of Fe and Mn oxides (RED form), the increase in pH during composting might be responsible for the decrease in EXC-Zn fraction and increase in RED-Zn fraction (Zheljazkov and Warman, 2004). Compared with the control treatment, the compost mixtures amended with RP had a higher reduction in EXC-Zn fraction and a higher increment in RED-Zn fraction, except in P7.5 pile. The results implied that addition of an appropriate amount of RP (5%) could enhance the conversion of EXC-Zn to RED-Zn fraction. The formation of Zn phosphates with low solubility might be responsible for the decrease in EXC-Zn fraction in RP amended compost (Cajuste et al., 2006). The distribution of Cu and Zn in the various fractions by sequential extraction during composting revealed that the potential mobility of Zn was higher than Cu in the pig manure compost. RP has higher affinity for Cu than Zn (Cao et al., 2004). Addition of RP could reduce the BF of Cu and EXC fraction of Zn compared to the control treatment during composting. RP has been proved to be effective to immobilize toxic metals such as Pb, Cu, Zn from various metals contaminated soils (Cajuste et al., 2006). Cao et al. (2004) summarized that the possible mechanisms for metal retention by RP in contaminated waters and soils included (1) ion exchange processes at the surface of RP,
(2) surface complexation, (3) precipitation of some amorphous to poorly crystalline, mixed metal phosphates, and (4) substitution of Ca in PR by other metals during recrystallization. Usually, soluble phosphates, such as diammonium phosphate could greatly reduce toxic metals in mobile fraction by forming metal phosphate precipitates (McGowen et al., 2001). Apparently, the low solubility of RP limited its ability to reduce soluble toxic metals. However, the organic acid and weak carbonic acid formed during composting could dissolve the RP and thus provide free phosphate ions 2– (H2PO1– 4 and HPO4 ) in the solution which could facilitate the formation of metal phosphates and thereby metal immobilization in the RP amended compost. Similarly, Cajuste et al. (2006) found that application of acidulated RP to soil could significantly reduce metal mobility and bioavailability because of the free phosphate from the dissolution of RP. The decrease in available P/total P during composting meant that some available P reacted with metal ions and formed precipitation. 3.4. Pearson correlation between the EXC fraction, BF, pH and OM The correlation of EXC fraction or BF of Cu and Zn with pH and OM were investigated to determine the influence of pH evolution and OM degradation on the changes of the metal speciation (Table 2). The pH did not significantly affect the EXC fraction or the BF of the metals in the control treatment. However, the pH significantly correlated with the EXC-Cu and EXC-Zn fraction in P2.5 (R = 0.816* and R = 0.939**, respectively) and P5.0 (R = 0.830* and R = 0.931**, respectively), and highly correlated with the BF of Cu in P2.5 (R = 0.882*), P5.0 (R = 0.912**) and P7.5 (R = 0.825*). The correlation between pH and BF of Zn was low. The OM significantly correlated with EXC-Cu fraction in P2.5 (R = 0.835*) and P5.0 (R = 0.931**), and highly correlated with the
Please cite this article in press as: Lu, D., et al. Speciation of Cu and Zn during composting of pig manure amended with rock phosphate. Waste Management (2014), http://dx.doi.org/10.1016/j.wasman.2014.04.008
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Table 2 Pearson correlation coefficients of exchangeable (EXC) fraction and bioavailability factor (BF) of Cu and Zn with pH and organic matter (OM) during composting for all treatments. CK pH EXC-Cu BF-Cu EXC-Zn BF-Zn * **
0.160 0.301 0.011 0.552
P2.5 OM 0.531 0.806* 0.773* 0.485
pH 0.816* 0.882** 0.939** 0.477
P5.0 OM
pH
0.835* 0.978** 0.943** 0.735
0.830* 0.912** 0.931** 0.810*
P7.5 OM 0.931** 0.989** 0.987** 0.870*
pH 0.381 0.825* 0.407 0.218
OM 0.689 0.978** 0.763* 0.431
Statistically significant at the probability level 0.05 (2-tailed). Statistically significant at the probability level 0.01 (2-tailed).
BF of Cu in all treatments. The correlation between OM and EXC-Zn was well in all treatments, while the correlation between OM and BF of Zn was low. Significant relationships between pH and EXC-Cu fraction, BF of Cu and EXC-Zn fraction were found in RP amended compost but not in the control treatment. The processes of sorption, precipitation and coprecipitation are pH dependent (Cao et al., 2004). The increase in pH during composting in RP amended composts was an additional mechanism for the reduction in metal bioavailability (Chen et al., 2007). The increase in pH would enhance the complexation between toxic metals and RP (Cao et al., 2004). Furthermore, the increase in pH would accelerate the formation of oxides (RED form), metal-carbonate precipitates, and other complexes that would decrease metal solubility and bioavailability (Mench et al., 2006). The relationship between OM and BF of Cu, EXC-Zn fraction implied that the OM degradation process significantly influenced the metal bioavailability and mobility. The humic substance formed during OM degradation could react with metal irons and thus reduce the bioavailability of the toxic metals (Ingelmo et al., 2012). Several researchers have reported that BF of toxic metal was well dependent on the OM concentration (Liu et al., 2007). 4. Conclusions Addition of RP in compost affects the speciation of toxic metals through increasing the pH, reacting with metal ions and providing available adsorption sites. RP addition significantly reduced the contents of Cu and Zn in the compost mixture. During composting, total metal concentration increased due to the mass loss of the compost. Composting process affected the metal speciation. During composting, EXC-Cu and RED-Cu fractions decreased while OXI-Cu and RED-Cu fractions increased, which meant the bioavailability of Cu decreased. Most of Cu was transformed to OXI-form after the composting process and RP addition advanced the transformation. Zinc was found abundant and mainly in bioavailable form in the compost mixture. During composting, EXC-Zn fraction decreased while RED-Zn fraction increased. However, the BF of Zn did not change much during composting. Addition an appropriate amount of RP (5%) could enhance the transformation of EXC-Zn to RED-Zn fraction. Acknowledgements This work was financially supported by the Major Science and Technology Program for Water Pollution Control and Treatment (2012ZX07201004) and Jilin Provincial Research Foundation for Basic Research, China (201105033). References Ben Achiba, W., Lakhdar, A., Cabteni, N., Du Laing, G., Verloo, M., Boeckx, P., Van Cleemput, O., Jedidi, N., Gallali, T., 2010. Accumulation and fractionation of trace metals in a Tunisian calcareous soil amended with farmyard manure and municipal solid waste compost. J. Hazard. Mater. 176, 99–108.
Bernal, M.P., Alburquerque, J.A., Moral, R., 2009. Composting of animal manures and chemical criteria for compost maturity assessment. A review. Bioresour. Technol. 100, 5444–5453. Biswas, D.R., Narayanasamy, G., 2006. Rock phosphate enriched compost: an approach to improve low-grade Indian rock phosphate. Bioresour. Technol. 97, 2243–2251. Bremner, J.M., 1996. Methods of Soil Analysis. Part 3: Chemical Methods. SSSA, Madison. Cai, Q.Y., Mo, C.H., Wu, Q.T., Zeng, Q.Y., Katsoyiannis, A., 2007. Concentration and speciation of heavy metals in six different sewage sludge-composts. J. Hazard. Mater. 147, 1063–1072. Cajuste, L.J., Cajuste, L., Garcia-O, C., Cruz-D, J., 2006. Distribution and availability of heavy metals in raw and acidulated phosphate rock-amended soils. Commum. Soil Sci. Plan. 37, 2541–2552. Cang, L., Wang, Y.J., Zhou, D.M., Dong, Y.H., 2004. Heavy metals pollution in poultry and livestock feeds and manures under intensive farming in Jiangsu Province, China. J. Environ. Sci. – China 16, 371–374. Cao, X.D., Ma, L.Q., Rhue, D.R., Appel, C.S., 2004. Mechanisms of lead, copper, and zinc retention by phosphate rock. Environ. Pollut. 131, 435–444. Chen, S.B., Xu, M.G., Ma, Y.B., Yang, J.C., 2007. Evaluation of different phosphate amendments on availability of metals in contaminated soil. Ecotoxicol. Environ. Saf. 67, 278–285. Chen, Y.X., Huang, X.D., Han, Z.Y., Huang, X., Hu, B., Shi, D.Z., Wu, W.X., 2010. Effects of bamboo charcoal and bamboo vinegar on nitrogen conservation and heavy metals immobility during pig manure composting. Chemosphere 78, 1177– 1181. Fang, M., Wong, J.W.C., 1999. Effects of lime amendment on availability of heavy metals and maturation in sewage sludge composting. Environ. Pollut. 106, 83– 89. Farrell, M., Jones, D.L., 2009. Heavy metal contamination of a mixed waste compost: metal speciation and fate. Bioresour. Technol. 100, 4423–4432. Gomez-Brandon, M., Lazcano, C., Dominguez, J., 2008. The evaluation of stability and maturity during the composting of cattle manure. Chemosphere 70, 436– 444. Hahladakis, J., Smaragdaki, E., Vasilaki, G., Gidarakos, E., 2013. Use of sediment quality guidelines and pollution indicators for the assessment of heavy metal and PAH contamination in Greek surficial sea and lake sediments. Environ. Monit. Assess. 185, 2843–2853. He, M.M., Tian, G.M., Liang, X.Q., 2009. Phytotoxicity and speciation of copper, zinc and lead during the aerobic composting of sewage sludge. J. Hazard. Mater. 163, 671–677. Hernandez, D., Plaza, C., Senesi, N., Polo, A., 2006. Detection of copper(II) and zinc(II) binding to humic acids from pig slurry and amended soils by fluorescence spectroscopy. Environ. Pollut. 143, 212–220. Hsu, J.H., Lo, S.L., 1999. Chemical and spectroscopic analysis of organic matter transformations during composting of pig manure. Environ. Pollut. 104, 189– 196. Hsu, J.H., Lo, S.L., 2001. Effect of composting on characterization and leaching of copper, manganese, and zinc from swine manure. Environ. Pollut. 114, 119– 127. Huang, G.F., Wong, J.W.C., Wu, Q.T., Nagar, B.B., 2004. Effect of C/N on composting of pig manure with sawdust. Waste Manage. 24, 805–813. Ingelmo, F., Molina, M.J., Soriano, M.D., Gallardo, A., Lapena, L., 2012. Influence of organic matter transformations on the bioavailability of heavy metals in a sludge based compost. J. Environ. Manage. 95, S104–S109. Iqbal, M.K., Shafiq, T., Hussain, A., Ahmed, K., 2010. Effect of enrichment on chemical properties of MSW compost. Bioresour. Technol. 101, 5969–5977. Jones, J.B., Case, V.W., 1990. Soil Testing and Plant Analysis. SSSA, Madison. Kolawole, G.O., Tian, G., 2007. Phosphorus fractionation and crop performance on an alfisol amended with phosphate rock combined with or without plant residues. Afr. J. Biotechnol. 6, 1972–1978. Liu, Y.S., Ma, L.L., Li, Y.Q., Zheng, L.T., 2007. Evolution of heavy metal speciation during the aerobic composting process of sewage sludge. Chemosphere 67, 1025–1032. Lu, D.A., Yan, B.X., Wang, L.X., Deng, Z.Q., Zhang, Y.B., 2013. Changes in phosphorus fractions and nitrogen forms during composting of pig manure with rice straw. J. Integr. Agr. 12, 1855–1864. McGowen, S.L., Basta, N.T., Brown, G.O., 2001. Use of diammonium phosphate to reduce heavy metal solubility and transport in smelter-contaminated soil. J. Environ. Qual. 30, 493–500.
Please cite this article in press as: Lu, D., et al. Speciation of Cu and Zn during composting of pig manure amended with rock phosphate. Waste Management (2014), http://dx.doi.org/10.1016/j.wasman.2014.04.008
8
D. Lu et al. / Waste Management xxx (2014) xxx–xxx
Mench, M., Vangronsveld, J., Lepp, N., Bleeker, P., Ruttens, A., Geebelen, W., 2006. Phytostabilisation of metal-contaminated sites. In: Echevarria, G., Morel, J.L., Goncharova, N. (Eds.), Phytoremediation of Metal-Contaminated Soils, NATO Science Series, vol. 68. Springer, Netherlands, pp. 109–190. Nemati, K., Abu Bakar, N.K., Abas, M.R., Sobhanzadeh, E., 2011. Speciation of heavy metals by modified BCR sequential extraction procedure in different depths of sediments from Sungai Buloh, Selangor, Malaysia. J. Hazard. Mater. 192, 402– 410. Nomeda, S., Valdas, P., Chen, S.Y., Lin, J.G., 2008. Variations of metal distribution in sewage sludge composting. Waste Manage. 28, 1637–1644. Qiao, L., Ho, G., 1997. The effects of clay amendment and composting on metal speciation in digested sludge. Water Res. 31, 951–964. Richardson, A.E., Hocking, P.J., Simpson, R.J., George, T.S., 2009. Plant mechanisms to optimise access to soil phosphorus. Crop Pasture Sci. 60, 124–143. Satisha, G.C., Devarajan, L., 2007. Effect of amendments on windrow composting of sugar industry pressmud. Waste Manage. 27, 1083–1091. Sinegani, A.A.S., Hosseinpur, A., 2010. Evaluation of effect of different sterilization methods on soil biomass phosphorus extracted with NaHCO3. Plant Soil Environ. 56, 156–162. Singh, J., Kalamdhad, A.S., 2013. Assessment of bioavailability and leachability of heavy metals during rotary drum composting of green waste (Water hyacinth). Ecol. Eng. 52, 59–69. Tack, F.M.G., Verloo, M.G., 1995. Chemical speciation and fractionation in soil and sediment heavy-metal analysis – a review. Int. J. Environ. Anal. Chem. 59, 225– 238.
Tsai, L.J., Yu, K.C., Chen, S.F., Kung, P.Y., Chang, C.Y., Lin, C.H., 2003. Partitioning variation of heavy metals in contaminated river sediment via bioleaching: effect of sulfur added to total solids ratio. Water Res. 37, 4623–4630. Verma, S.L., Penfold, C., Marschner, P., 2013. Mobilisation of rock phosphate by surface application of compost. Biol. Fertil. Soils 49, 287–294. Wang, H., Dong, Y.H., Yang, Y.Y., Toor, G.S., Zhang, X.M., 2013. Changes in heavy metal contents in animal feeds and manures in an intensive animal production region of China. J. Environ. Sci. – China 25, 2435–2442. Wong, J.W.C., Selvam, A., 2006. Speciation of heavy metals during co-composting of sewage sludge with lime. Chemosphere 63, 980–986. Zayed, G., Abdel-Motaal, H., 2005. Bio-production of compost with low pH and high soluble phosphorus from sugar cane bagasse enriched with rock phosphate. World J. Microbiol. Biotechnol. 21, 747–752. Zhang, F.S., Li, Y.X., Yang, M., Li, W., 2012. Content of heavy metals in animal feeds and manures from farms of different scales in northeast China. Int. J. Environ. Res. Pub. Health 9, 2658–2668. Zheljazkov, V.D., Warman, P.R., 2004. Phytoavailability and fractionation of copper, manganese, and zinc in soil following application of two composts to four crops. Environ. Pollut. 131, 187–195. Zmora-Nahum, S., Markovitch, O., Tarchitzky, J., Chen, Y.N., 2005. Dissolved organic carbon (DOC) as a parameter of compost maturity. Soil Biol. Biochem. 37, 2109– 2116. Zorpas, A.A., Inglezakis, V.J., Loizidou, M., 2008. Heavy metals fractionation before, during and after composting of sewage sludge with natural zeolite. Waste Manage. 28, 2054–2060.
Please cite this article in press as: Lu, D., et al. Speciation of Cu and Zn during composting of pig manure amended with rock phosphate. Waste Management (2014), http://dx.doi.org/10.1016/j.wasman.2014.04.008