Scholarly article on topic 'Study on Suitability of Hazardous Wastes Entering the Landfill Directly'

Study on Suitability of Hazardous Wastes Entering the Landfill Directly Academic research paper on "Chemical sciences"

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Abstract of research paper on Chemical sciences, author of scientific article — Dan Li, Bei-dou Xi, Zimin Wei, Xiaosong He, Yonghai Jiang, et al.

Abstract The physicochemical properties of eight hazardous waste samples (S1, S2, S3, S4, S5, S6, S7 and S8) obtained from Heilongjiang Province were analyzed to assess the suitability of landfill directly. The results showed that the wet content of eight samples was according with the landfill standards. However, some parameters of the samples S1, S2, S5 and S6 were not up to the standards. In addition, the Fe, Mn, Zn, Ni, Cr, and Be content in samples S1 and S5 exceeded the landfill standard limit. The sources of heavy metals were identified by analysing the correlation of the Zn, Mn and Ni concentration in different samples. The result showed that the correlation coefficient of the Zn, Mn and Ni concentration exhibited a significant level, which indicated that the metal Zn, Mn and Ni might originate the same source. The inorganic fluoride content in all samples did not exceed the landfill control standard, whereas the cyanide concentration was as 244.80∼2 692.76 times as the control limits except S1. In addition, benzene series were detected in some samples except S6 and S7, indicating that these samples needed pre-treatment before landfill.

Academic research paper on topic "Study on Suitability of Hazardous Wastes Entering the Landfill Directly"

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Environmental Sciences

Procedía Environmental Sciences 16 (2012) 229 - 238 '

The 7th International Conference on Waste Management and Technology

Study on suitability of hazardous wastes entering the landfill

directly

Dan Lia'b, Bei-dou Xib'*, Zimin Weia, Xiaosong Heb, Yonghai Jiangb, Guopeng

Zhaoa,b

aNortheast Agricultural University College of Life Science, Harbin 150030, Heilongjiang bLaboratory of Water Environmental System Engineering, Chinese Research Academy of Environmental Science, Beijing 100012,

Abstract

The physicochemical properties of eight hazardous waste samples (S1, S2, S3, S4, S5, S6, S7 and S8) obtained from Heilongjiang Province were analyzed to assess the suitability of landfill directly. The results showed that the wet content of eight samples was according with the landfill standards. However, some parameters of the samples S1, S2, S5 and S6 were not up to the standards. In addition, the Fe, Mn, Zn, Ni, Cr, and Be content in samples S1 and S5 exceeded the landfill standard limit. The sources of heavy metals were identified by analysing the correlation of the Zn, Mn and Ni concentration in different samples. The result showed that the correlation coefficient of the Zn, Mn and Ni concentration exhibited a significant level, which indicated that the metal Zn, Mn and Ni might originate the same source. The inorganic fluoride content in all samples did not exceed the landfill control standard, whereas the cyanide concentration was as 244.80~2 692.76 times as the control limits except S1. In addition, benzene series were detected in some samples except S6 and S7, indicating that these samples needed pre-treatment before landfill.

© 2(H2 Selection and/or peer-review under responsibility of Basel Convention Coordinating Centre for Asia and the Pacific and National Center of Solid Waste Management, Ministry of Environmental Protectionof China.

Keywords: hazardous waste; leaching characteristic; control limits; suitability

1. Introduction

Hazardous waste (HW) is referred to that included in the national list of HW. In addition, It also contains some solid wastes which are identified in accordance with identification standards or methods of

* Corresponding author. Tel.: 010-84913133; fax: 010-84913805. E-mail address: xibeidou@263.com.

ELSEVIER

1878-0296 © 2012 Selection and/or peer-review under responsibility of Basel Convention Coordinating Centre for Asia and the Pacific and National Center of Solid Waste Management, Ministry of Environmental Protection of China doi: 10.1016/j.proenv.2012.10.032

state regulations [1-2]. With the rapid economic and industrial development, the generation of HW increases sharply in recent years. Due to the toxicity, corrosivity, reactivity, inflammability, infectivity, and radioactivity, HW contaminates on the environment in some different degree, which has resulted in a long and difficult recovery of the hidden dangers and consequences. Therefore, The HW disposal has become an important and difficult problem for environmental protection in the world at present. it has become an imperative task to strengthen the HW management with many more effective measures. In order to carry out the HW management, the identification and monitor of HW should be conducted firstly. The primary aim of HW identification is to confirm the hazardous characteristics of solid wastes, and its important indicator of the HW toxicity characteristic identification is the leaching characteristics [5-6].

The final disposal of solid HW mainly includes secure landfill, incineration and comprehensive utilization at home and abroad. Secure landfill and incineration are widely used at present. The incineration method is suitable to HW that with higher organic matter content, higher calorific value and higher toxicity. The heat generated in the process can be recycled. However, the HW incineration may result in the generation of CO, NOx, HCl and some other gases during the process, which will place a potential threat on human being health and surrounding environment. Therefore, the application of incineration is not very wide. Landfill is the most widely used way. furthermore, It is the largest handling capacity disposal as well in the world [7-9]. The secure landfill of HW is totally closed, which can control both the leachate and landfill gases well. When the membrane in landfill is broken, the landfill leachate will result in a secondary pollution of the surrounding soil and water environment in all probabilitiy [1012]. Thus, in order to ensure that the monitor indicator of HW does not exceed the control limits for entering into landfill directly, there is a rigorous detection of HW before it enterss landfill. Otherwise, HW must be handled by some way of stabilization and treatment resources such as incineration or solidification before landfill to reduce the direct and indirect contamination on surrounding environment.

Eight HW samples obtained from different source were selected in this study, the harmful substances content in HW was researched, and the suitability of HW entering the landfill directly on the basis of HW landfill pollution and control standards was analyzed. These results can provide a reference to the suitability of HW landfill.

2. Materials and Methods

2.1 Instruments and reagents

Instrument: Freeze-drying machine (FD-1D-50,Bo Yikang of Beijing), Air bath oscillator (HZQ-C, Dong Lian Dian Zi of Harbin), Circulation of water vacuum pump (SHB-95), Filtration device (three parts), Portable pH (TOLEDO 320 Meter), Electronic analytical balance (METTLER TOLEDO ML104/02), UV spectrophotometer (UV 2100 and 4802VU/VIS), ICP(High-frequency inductively coupled plasma emission spectrometer), Ion Chromatography (ICS-2000), TOC (multi N/C 2100 S), Gas chromatography mass spectrometry (7980A-5975C), COD Fast Analyzer (CTL-12 environmental protection equipment of Cheng De), etc.

Reagents: All chemical reagents using in the experiments were analytical grade or chemically pure, and with ultrapure water. Standard solutions of Cu, Fe, Zn, Mn, Cd, Cr, Pb, Ni, Be, Ba, and As were provided by the Standard Room of China Environmental Monitoring Station (100^g/mL). Standard solution of ammonium was from Metrology Institute of China (0.01 mg/mL). Oxidant and catalyst suit of COD, nessler's reagent, standard substance of benzene series, etc.

2.2 Experimental samples

The HW leached in this study were collected from sewage treatment plant, oil field burning workshop of electroplating factory, paint factory, pesticide factory, and mechanical processing factory. These factories were located in Jiamusi and Da Qing city, Heilongjiang Province. Eight samples, which were numbered as S1, S2, S3, S4, S5, S6, S7, and S8, were mainly waste ash, mud, and offscum.

2.3 Experimental methods

2.3.1 Sample pretreatment and leaching process

(1) Pretreatment

Duo to its high moisture content and for subsequent determination, all the samples were freeze-dried for 24 h, and then kept in a desiccator to save spare.

(2) Leaching process

According to "National Environmental Protection Standards HJ 557-2012, Solid waste-Extraction procedure for leaching toxicity-Horizontal vibration method" [13], the HW samples were extracted

Extractant: ultra-pure water.

Extraction of samples: Forty grams of samples were extracted using 800 mL of ultra-pure water (1:20 ratio), shaken for 8 h in a horizontal shaker and then incubated 16 h at room temperature, Extracts were filtered through 0.45^m acetate membrane filter. Filtrates were divided into two parts: one part was freeze-dried, and the other was conserved in the dark at 4°C in acid-washed oven-dried amber glass flasks.

2.3.2 Solid waste leaching toxicity determination method

The measurement and analysis of HW samples were according to the National Standards of Leaching Toxicity determination method of Solid Waste(GB/T15555.1-12-1995) [3], and Water and Wastewater Monitoring and Analysis Method [4].

(1) Heavy Metal: Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES);

(2) Conventional anions: Ion Chromatography and UV-visible spectrophotometry;

(3) Other compounds (fluoride, cyanide): Nessler's reagent spectrophotometry method, silver nitrate titration method;

(4) Benzenes: Gas Chromatography Mass Spectrometry (U.S. EPA 8260C: 2006). 3. Results and Analysis

3.1 Conventional parameters

According to the items 8.2 and 8.4, stated in landfill pollution control requirements in the pollution control standards of the HW landfill GB18598 -2001 [1] (referred to as "standard" hereinafter), the leachate in the landfill may cause serious pollution on groundwater. Therefore, we need to detect its potential pollutants that may appear in the pre-tratement. The emission control items of filtrate pollutant II and conventional groundwater monitoring factors were tested in the 100 times diluted samples by the ICS 2000 ion chromatograph and 4802 UV / VIS spectrophotometer. The determinations of the project and the detected values were listed in Table 1.

Table 1. Physicochemical properties of eight samples (concentration: mg/g)

Samples CT NO2 SO42- NO3 Br PO43- nh4+-n

S 1 1.04 1.02 3.37 - - 10.22 2.12

S 2 2.39 - 19.32 - 854.8 6.02 1.03

S 3 11.15 0.5 11.55 - 920.27 1.5 -

S 4 1.31 - 5.71 3.06 - 2.69 1.03

S 5 0.35 - 0.14 4.99 - 221.31 11.35

S 6 0.25 - 11.94 1.61 - 2.3 -

S 7 0.02 - 7.31 4.42 - 3.09 1.57

S 8 0.82 - 0.66 - 791.88 12.4 26.55

Note: "-" represents not detected.

Nitrogen and phosphorus element, which can easily lead to water eutrophication phenomena in the control project of the "standard", exist mostly in the form of ions in the water. Although phosphorus was a trace element, it played an important role. It existed mostly in the form of PO43-. As shown in Table 1, the phosphorus content was not very high in the samples except the samples S5 and S4. S4 is phosphide residue, and it may have been treated before. Therefore, most of the phosphate had been removed. In the "standard", although NH4+-N was regarded as a monitoring factor, it was not given a clear control limits. However, during the landfill process, N was converted into NH3 via biological or chemical process, which posed direct pollution on the surrounding atmospheric environment. At the same time, it also brought odor pollution [6]. Therefore, in order to ensure the reasonable control of the HW and reduce its pollution, we suggested that the domestic standard about the leaching amount should be refined and clear.

As discussed before, it could be concluded that there were not a clear control limit for some factors in the item of the "standard". However, the influence of these factors should be controlled. As shown in table 1, these factors were anionic, and could be dissolved easily. Therefore, when they entered into the landfill, the anionic flowed out with the formation of leachate, and caused direct contamination on the groundwater and surrounding environment. Unfortunately, the control and monitor of these factors were obviously inadequate at present in China. The relevant control standard should be further refined and improved.

3.2 Heavy metals

Eight kinds of heavy metal were detected according to the standard. The heavy metal contents were measured by ICP-AES, and shown in Table 2. In order to compare easily, the table also listed the control limits of the HW which were allowed to enter the landfill.

Table 2. Analysis of heavy metal leaching concentration (mg/kg)

Samples Fe Mn Cu Zn Cd Cr Pb Ni Be Ba As

S 1 5.00 4.10 1.10 17.60 1.00 4.60 1.80 1.20 9.40 7.60 6.20

S 2 2.40 25.50 0.20 43.00 0.40 323.60 0.20 0.80 1.60 4.20 2.00

S 3 1.20 0.80 0.80 9.40 0.20 6.00 0.00 0.00 3.00 2.60 2.20

S 4 2.10 6.40 0.20 10.60 0.20 1.80 0.50 4.60 2.80 2.00 1.40

S 5 12.10 510.50 0.50 887.00 0.10 1.50 0.30 624.10 5.60 3.20 2.00

S 6 1.20 1.20 0.70 5.10 0.20 5.20 0.80 0.80 2.80 5.80 2.80

S 7 2.20 1.10 0.40 27.10 0.20 2.80 0.60 0.40 2.00 3.40 1.80

S 8 16.80 0.40 0.20 9.10 0.40 4.40 2.20 0.40 2.40 3.20 1.80

Control limits -- -- 3.75 3.75 0.025 0.60 0.25 0.75 0.01 7.5 0.125

Note: "-" stands for not detected, "--" represents no specified detection limit.

As shown in Table 2, it was easily found that the content of most heavy metals was not high in this experiment. This result indicated that water, such as ultrapure water etc, as the main body of extraction

solvent system extract lower amount of filtrate than acid as the main extractant and the effect of leaching using water was significantly low. It was agreed with the results reported by Li et al [20], Nie et al [21], and HALIM et al [22]. The main reasons were that the heavy metals were hard to combine with the water molecules, whereas they were easy to bind and react with hydrogen ion in acid or large number of ionized hydrogen in acid salt. Besides, some heavy metals, which were still combined in minerals and some other substrates, were hard to leach from water. Compared with the research of predecessors [14-16], it was not difficult to find, the leaching amount of heavy metals was relatively high, when using acetic acid solution at pH 2.88 ± 0.05, the mixed solution of acetic acid / sodium acetate buffer solution at pH 4.93 ± 0.05 or nitric acid sulfuric acid (v/v=60/40) as the extraction agents, especially highest in acetate buffer solution, . Some scholars believed that this was because the buffer effect of the acetate on the alkalinity and the complexation capacity of acetate ions on the metals were better [17-18]. Meanwhile, the acetate buffer solution was also the extractants which were used in the standard identification method — TCLP method specified by the U.S. EPA [19]. Therefore, the acidic extractant was the best option to extract in further studies.

In the local analysis, the leaching amount of many kinds of elements in S5 was higher. Based on the view of leaching dynamics, the leaching of heavy metals was mainly dominated by erosion and dissolution action, and it was a fast reaction process. So the leaching had already begun at the moment that experimental samples and extraction solvent contact with each other. And in the following few hours, the leaching trends slowed down, but it continued to achieve a balance [23]. Therefore, as S5 was from the treatment plant of wastewater and sludge, the sludge soaked in the water environment for a long time, so its compatibility with water was better. It reached a good balance and stability due to the prolonged contact with water before conducting the experiment, thus heavy metals were easier to leach out. From the aspect of pH value, the pH value of the extractant itself can affect the leaching amount of heavy metals significantly. In our country and abroad, many researches on this aspect had been carried out. Heavy metals resolved better when the pH value reduced. Thus, the solubility of heavy metals in acidic conditions was stronger and the leaching rate was higher, which was attributed to the trend of heavy metals forming soluble oxides in acidic environment [24-26]. The pH value of ultrapure water was approximately 7, and neutral solution had little effect on the heavy metals leaching experiments. Although ultrapure water was regarded as the extraction solvent in this experiment, but the samples with a certain pH value in itself, which make the entire extraction system acidic or alkaline. As shown in Table 1, the pH value of S5 was 4.09, which was obviously acidic, so the leaching amount was high. This agreed with the conclusion we discussed before. At the same time, compared to other samples the heavy metals leaching amount of the same element was relatively low for the three samples from Daqing(Table 2). It was probably because the samples were derived from oil field and with hydrophobic substances covered its surface, which caused leaching from the water difficult.

From the view of a single element, it was easy to find that the leaching amount of Fe, Zn, Mn, Ni, Cr and Be was higher than any other elements significantly. But from the aspect on the analysis of control limits of admission to landfill, the values were listed in Table 3.

Table 3. Analysis of samples exceeded and the rate of suitability for landfill directly

Element types Sample gauge Proportion of entering landfill directly/ (%)

Cu No overrun 100. 00

Fe No effect --

Zn All overrun 0

Mn No effect --

Cd All overrun 0

Cr All overrun 0

Pb S2, S3 were not overrun 25.00

Ni S3, S7, S8 were not overrun 37.50

Be All overrun 0

Ba S1 was overrun 87.50

As All overrun 0

Note: The proportion represents the number of samples which can enter landfill directly without pre-treatment from the total samples from the perspective of a certain kind of element; "--" represents no specified detection limits.

As shown in Table 3, from the perspective of a single element analysis, the individual samples can enter into landfill without disposal directly when monitoring only one kind of metals. However, when it was based on the aspect of other kinds of heavy metals, all samples exceed the limit values. Therefore, the number of samples which can enter landfill directly without pre-treatment was zero. S1 exceeded badly the limit value among all samples. Among all kinds of heavy metals detected in excess of control limits, Ni was the minimum which was as 1.01times the control limits, whereas Be was the maximum which exceeded 940 times [1].

From the metal type which was exceeded the limit values, the analysis showed that the Cr content in S1 was as 539.33 times as the control limits, and the Ni content in S5 was as 832.13 times as the control limits. It was more than the admission of HW landfill requirements severely, so all samples should be dealt with stabilization means such as incineration, solidification and etc before entering into the landfill.

3.3 Correlation Analysis

In order to further analyze the factors which had higher detection rate and larger impact, the correlation between the heavy metal content in the test items was analyzed preliminary. The correlation coefficients were calculated with the SPSS 18.0 statistical analysis system. The results were shown in Table 4.

Table 4. The correlation analysis of heavy metals

Metal Cu Fe Zn Mn Cd Cr Pb Ni Be Ba As

Cu P T 1

Fe P T -.261 .532

Zn P T -.028 .948 .456 .256

Mn P T -.033 .938 .454 .259 1.000** .000

Cd P T .519 .187 .061 .886 -.328 .428 -.329 .427

Cr P -.374 -.208 -.117 -.106 .092

T .362 .621 .782 .803 .828

Pb P .126 .588 -.268 -.273 .637 -.305

T .766 .125 .521 .513 .089 .463

Ni P -.017 .463 .999** .999** -.334 -.152 -.257

T .968 .248 .000 .000 .418 .720 .539

Be P .745* .160 .289 .286 .706 -.327 .374 .296

T .034 .705 .487 .492 .050 .430 .361 .477

Ba P .687 -.128 -.173 -.174 .765* .049 .452 -.177 .650

T .060 .763 .683 .681 .027 .907 .261 .675 .081 As P .826* -.086 -.140 -.143 .886** -.133 .470 -.139 .866** .894** 1 __T .011 .839 .741 .736 .003 .754 .240 .743 .005 .003__

Note: "P", stands for Pearson correlation coefficient, and "T" stands for Two-tailed test; "*", Correlation reached a significant level (P<0.05); "**", Correlation reached a highly significant level (P<0.01).

According to the data in Table 4, there was a low correlation among heavy metal elements. The correlation was minimal or irrelevant, which proved that the sources of the majority elements were different. However, the correlation coefficients were high among Zn, Ni and Mn (P <0.01). This result suggested that the three elements leaching from the same source, and source apportionment can be done in subsequent experiments, in order to find the best solution to pollution preventing, and to provide a 7favourable reference to the HW landfill approach. In addition, the correlation between As, Cd, Be, and Ba reached a significant level, indicating that they may originated from the same source.

3.4 Non-heavy metals

According to the control limits requirements of HW entering into the landfill in the standard, the typical toxic and hazardous compounds and the first monitoring indicators were tested by using the best and optimal methods, such as ion chromatography and silver nitrate titration method. The samples were diluted 100 times in the leaching solution and the detected values were listed in Table 5.

Table 5. Analysis of inorganic fluoride and cyanide

Concentration (mg/kg) Inorganic fluoride (calcium fluoride not included) CN- Moisture content / (%) pH values

S 1 2.79 61.20 30.97 6.94

S 2 -- - 44.23 6.70

S 3 2.78 214.20 31.64 7.36

S 4 -- 71.40 70.23 8.21

S 5 2.07 673.19 44.91 4.09

S 6 2.83 503.62 25.45 7.14

S 7 -- 153.00 65.03 6.92

S 8 2.62 81.60 83.32 8.70

Control limits 5.00 0.25 85.00 7.00-12.00

Note: "-" represents not detected.

Data in Table 5 showed that the moisture content of all the samples were no more than 85 percent, which was in accordance with the requirements of hazardous waste landfill admission.

Moisture lost less after pre-treatment of compaction curing, which would not obtain leachate generally. Therefore, all eight samples could enter into landfill directly without any pre-treatments [1]. But at the same time, the pH value of S5 was 4.70, which was significantly lower than 7.00, the same as sample S1, S2 and S7. The pH values of the remaining four samples were range from 7.00 to 12.00. Therefore, sample S3, S4, S6 and S8 could enter landfill directly without pre-treatment [1].

As it was shown in Table 5, fluoride was not detected in the sample S2, S4 and S7. Although the remaining five samples had detected a little, the detected values were not beyond the landfill control limits. Therefore, from this point of view, all eight samples could be admission to landfill directly. Data also showed that the content of cyanide in the sample of eight sources were far beyond

the control limits, the minimum was 244.80 times and the maximum is up to 2 692.76 times. So, from this aspect, all samples should not be admission to landfill but only if be pre-treatment correspondingly.

3.5 Benzene series

Since some samples, such as the samples S6, S7 and S8 were collected from the Daqing oilfield waste water treatment plant and waste sludge incineration plant, the probability of containing polluted oil, benzene and other polluted organic matters was very high. In order to detect the potential threat posed on the landfill soil and groundwater, the content of eight kinds of benzene series in samples was detected by U.S. EPA 8260C: 2006 meteorological chromatography mass spectrometry method. The test items and the detected values are listed in table 6.

Table 6. Analysis of benzene series content (mg/kg)

Samples Benzene Toluene M / P -xylene O-xylene Ethylbenzene Styrene Cumene

S 1 0.0218 0.0117 0.0276 0.01184 0.0316 0.0318 -

S 2 0.0244 0.01358 0.029 0.01234 0.0328 0.0322 -

S 3 - - 0.0292 0.0124 0.032 - -

S 4 - - 0.0278 0.012 0.032 - -

S 5 0.0314 0.0262 0.0298 0.01282 0.0326 0.0326 -

S 6 - - - - - - -

S 7 - - - - - - -

S 8_0.0206 0.01702 0.0272 0.01194 0.032_-_-_

Note: "-" represents not detected.

As shown in Table 6, although the control limits of benzenes were not given in the standard explicitly, the eight kinds of the benzene series detection limit was 0.01mg/kg according to the instrument detection performance and parameters, the benzenes in eight kinds of HW samples had been detected in different levels except cumene, though the detectable amount is not very high. However, as the benzene series were flammable, highly toxic, carcinogenic, and highly volatile, the trace amounts of benzene series might cause direct contamination of soil and water, and the potential threat to living beings and human.

Eight kinds of benzene series detected in this experiment were common series of toxic pollutants, the detection rate of M-, P-, O-xylene and ethylbenzene was much higher in S1, S2, S3, S4, S5, and S7. The detection rate of benzene, toluene and styrene was low in S1, S2, S5 and S8. Tthe detection rate of cumene was zero, was the lowest, which detected in none of the eight kinds of samples. At the same time, there were more series of benzene in S1, S2, S5 and S8 than S3 and S4, meanwhile S6 and S7 detected none. The reason was found that sample S6 and S7 were incinerated waste ash and waste mud from Daqing oil field burning workshop, while other samples were not undergo any treatments. Therefore, it was confirmed that the incineration pre-treatment was more optimal to remove the organic matter composition from HW. From this point of analysis, S6 and S7 could enter into landfill directly without pre-treatment.

4. Conclusions and suggestions

Determination of all relevant indicators was in accordance with the provisions of the HW Landfill Pollution Control Standards (GB 18598-2001), and Solid Waste Pollution Prevention Law of the People's Republic of China. Comparative analysis with the standards, the various indexes of eight kinds of HW

samples in this experiment overran in different degrees, and was not suitable for them to enter into the landfill directly. The HW wastes in the study must be solidified or incinerated before landfill.

(1) The leaching amount of each detection index was relatively low. The study further confirmed that using water as extractant which the same with the domestic general method, and extraction under a horizontal vibration. The amount and effect of the extraction were significantly lower than the foreign method which acid solutions were used as extraction, and extraction was conducted under a vertical flip vibration.

(2) The moisture contents of all the eight samples met with the standard. In terms of pH value, S1, S2, S5, and S7 were not within the control limits and needed for pre-treatment; The leaching amount of Fe, Zn, Mn, and Ni in S5 and Cr, Be in S1 were significantly higher than other elements in the samples, so they must be fully cured in order to reduce the potential pollution of heavy metals. The detectable amount of cyanide in all eight samples was more than the limit with 244.80 to 2692.76 times significantly, which resulted in a very significant impact or serious pollution on the surrounding environment, and must be fully solidified or stabilized before landfill. The detection of BTEX of all the samples except S6 and S7 was in different levels, so they were not suitable for landfill directly. Finally, in accordance with all the indicators, all of the eight samples were not suitable for landfill directly.

(3) The correlation of the content of heavy metals was analyzed with the SPSS 18.0 system. The correlations among Zn, Mn, and Ni were highly significant. The correlations between Be and Cu, between Ba and Cu, and between As and Cu were significant, which reveals that the sources of these kind of heavy metals were similar.

Acknowledgements

This work was finally supported by the National Public Benefit (Environmental) Research Foundation of China (Grant Nos.200909079 and 2011467010).

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