RESEARCH OF PHOTODEGRADATION OF PHENANTHRENE, PYRENE

AND CHRYSENE ADHERING TO POLYETHYLENE IN THE WATER

A Thesis Presented By ZHIPIN MAO

To

The Department of Civil and Environmental Engineering

in partial fulfillment of the requirement for the degree of

Master of Science in the field of CIVIL ENGINEERING

Northeastern University Boston, Massachusetts April 2018

II ABSTRACT

Polycyclic aromatic hydrocarbons (PAHs) play an important role in the manufacturing industry. However, some PAHs are carcinogenic or mutagenic. Aqueous PAH contamination is widespread. Due to the low solubility in the water, they are likely to be absorbed in plastics. Phenanthrene, pyrene, and chrysene are three PAHs with different structures. In this project, there are two existing states of phenanthrene, pyrene, and chrysene: dissolved in water and adsorb on PE circle. Each existence state of phenanthrene, pyrene, and chrysene was irradiated using a UV lamp for 2 hours respectively. The total mass of irradiated PAHs was detected by GC-MS to identify the photodegradation ratio of each chemical. The sorption of pyrene on the

PE circles increases the photodegradation. However, obvious photodegradation ratio cannot be detected on chrysene.

III ACKNOWLEDGEMENT

I would like to thank my advisor, Loretta A. Fernandez, for providing me the opportunity to work in her group. I have a deep gratitude to her for her patience, encouragement, guidance, help and advice for my master’s research, coursework and my future career development. Thanks to Professor Philip

Larese-Casanova providing me UV lamp to finish the research. Thank you to all my thesis readers and your precious advice and encouragement. Besides, this project would not be possible without the support of

Northeastern University to provide me facilities for conduction experiment.

Thanks to all my lab friends: Magdalena, Yuwei, Yumeng and Wenjie who gave me support in experiment.

Thanks to my parents, my fiancé, and my friends, who always be my supporter to encourage me when I met the problems.

IV TABLE OF CONTENT

ABSTRACT ...... II

ACKNOWLEDGEMENT ...... III

CHAPTER 1 INTRODUCTION ...... 1

1.1 Characteristics of Polycyclic Aromatic Hydrocarbons ...... 1

1.2 Environmental Hazards of PAHs ...... 2

1.3 PAHs and PE ...... 2

1.4 Phenanthrene, pyrene and chrysene ...... 3

1.5 GC-MS method detect trace organic compound ...... 4

1.6 Objectives and hypothesis ...... 5

CHAPTER2 EXPERIMENTAL METHOD ...... 6

2.1 Chemicals and reagents ...... 6

2.2 Methanol-PAHs Samples Preparation ...... 6

2.3 Photo-irradiation ...... 6

2.4 Samples extraction ...... 7

2.5 GC-MS sample preparation ...... 7

2.6 Standard samples preparation ...... 7

2.7 GC-MS setting ...... 8

CHAPTER 3 RESULTS AND DISCUSSION ...... 9

3.1 Pyrene results ...... 9

3.2 Chrysene results ...... 13

3.3 Discussion ...... 14

CHAPER 4 CONCLUSION ...... 16

REFERENCES ...... 17 1

CHAPTER 1 INTRODUCTION

1.1 Characteristics of Polycyclic Aromatic Hydrocarbons

Polycyclic aromatic hydrocarbons, abbreviated as PAHs, refers to hydrocarbons which contain two or more benzene rings in the molecule. PAHs can be classified into aromatic fused rings and aromatic non-fused rings. The aromatic fused ring refers to the hydrocarbon compound in which at least two carbon atoms are shared by adjacent benzene rings in one molecule, such as naphthalene, anthracene, phenanthrene, pyrene, etc.; the aromatic non-fused ring refers to that the hydrocarbon compound in which only one carbon atoms connected adjacent benzene rings in one molecule, such as biphenyl and terphenyl. The natural source of polycyclic aromatic hydrocarbons in the environment is mainly synthesized by microorganisms and higher plants, which can promote plant growth. Besides, a certain amount of PAHs are also produced along with the volcanic activity, forest fires, and grassland fires. While present naturally in the environment in low concentrations, they are primarily produced by anthropogenic activities such as incomplete combustion of organic materials (Rubio-Clemente et al. 2013). The major sources of PAHs in the environment are man-made, which are mainly caused by the incomplete combustion of coal, petroleum, wood, and organic polymer compounds, most of them come from the chemical industry, transportation, and daily life.

The PAHs in water can be in three states: adsorbed on suspended solids; dissolved in water, or emulsified.

The pentacyclic or higher polycyclic aromatic hydrocarbons are mainly colorless or yellowish crystals, some of which have a dark color. Those polycyclic aromatic hydrocarbons have high melting point and boiling point, which means the vapor pressures of PAHs are low. Polycyclic aromatic hydrocarbons are mostly insoluble in water, and the octanol-water partition coefficient is relatively high. Most PAHs have a large conjugation system, so their solution has some fluorescence. Its chemical properties are stable and difficult to hydrolyze. The most prominent characteristics of PAHs are carcinogenic, teratogenic and mutagenic.

When PAHs interact with –OH、-NH2、-NO2, they would produce more carcinogenic derivatives. In addition, 2 PAHs easily absorb light in the visible (400-760mm) and ultraviolet (290-400mm) regions of sunlight, and are particularly sensitive to photochemical reactions caused by UV radiation.

1.2 Environmental Hazards of PAHs

Although the presence of PAHs in the environment is trace, it is continuously generated, migrated, transformed and degraded, and enters humans and other organisms through the respiratory tract, skin, and digestive tract. Chemical carcinogenesis refers to the process by which chemical substances cause normal cells to transform and develop into tumors. Chemical carcinogenesis can be divided into direct carcinogens and indirect carcinogens, and polycyclic aromatic hydrocarbons belong to the latter. The carcinogenic effects of polycyclic aromatic hydrocarbons have seriously affected human health. In recent years, the incidence of lung cancer and mortality have risen significantly in various countries. The facts indicate that

PAHs are an important cause of the increase in the incidence of lung cancer. Due to its high toxicity, PAHs have a strong effect on the central nervous system and blood, especially polycyclic aromatic hydrocarbons with alkyl side chains, which are highly irritating to the mucosa and highly anaesthetic. Therefore, PAHs have mainly been studied in the past concentrated on the body's metabolic active productions working on the organism's toxic effects and carcinogenic activity. However, more and more studies have shown that the real danger of PAHs is their phototoxic effects when they are exposed to UV light in sunlight. Scientists defined the phototoxic effect of PAHs as a significant effect of UV irradiation on the toxicity of PAHs. Experiments have shown that simultaneous exposure to PAHs and UV irradiation accelerates free radicals that have the ability to damage cells.

1.3 PAHs and PE

Due to the low water solubility of PAHs, they are likely to accumulate in plastics. There is thought to be tens of thousands of tons of plastic on the open ocean surface, much of which is composed of particles<1 cm, 3 referred to as microplastics (Cozar et al. 2014). Once organic contaminants enter the plastics, they may be transported on the plastics for large distances (Zarfl and Matthies 2010). The photodegradation mechanisms and kinetics of PAHs in plastics have not been determined, as most studies have been conducted in aqueous systems (Sigman et al. 1998, Miller and Olejnik 2001, Clark et al. 2007). Some studies have investigated

PAH photodegradation absorbed on various substrates, such as mangrove leaves (Wang et al. 2014) and microcrystalline cellulose (Oliveira et al. 2004), but little research exists concerning polyethylene or other common ocean debris plastics. The only related study is Chen and Chen 2005, in which LDPE was irradiated by UV. Only PAH concentrations were measured, leaving degradation products and partitioning undetermined.

1.4 Phenanthrene, pyrene and chrysene

Phenathrene, C14H10, ball-and-stick model of the phenanthrene is shown as Figure 1. The chemical nature of phenathrene is between naphthalene and quinone. The reactions are mainly in the 9 and 10 positions (L. F.

Fieser and M. Fieser,). The phenanthrene can be separated from the olein from coal tar. It is a shiny, colorless crystal. Insoluble in water, soluble in ethanol, benzene and ether, the solution has blue fluorescence.

Phenanthrene can be used in synthetic resins, plant growth hormone, vat dyes, etc. The invasive routes of phenanthrene to the people and animals are inhalation, ingestion, and percutaneous absorption. Phenanthrene belongs to a group of chemicals that exhibit micro-toxicity, and is carcinogenic to animals.

Pyrene is a PAH consisting of four fused benzene rings, the ball-stick model of pyrene is shown as figure 1.

Pyrene is a colorless, prismatic crystal that is insoluble in water. The main use of pyrene is in the preparation of synthetic resins, vat dyes, and disperse dyes. Long-term exposure to 3~5 mg/m3 of pyrene, will lead to symptoms including headache, fatigue, poor sleep, loss of appetite

Chrysene is a PAH that consists of four fused benzene rings. It is a natural constituent of coal tar. Chrysene can be used as non-magnetic metal surface detection fluorescent agent, chemical instrument UV filter, 4 photosensitizer, it also can be used in dye production, instead of washing oil as a solvent for pesticides and synergists. Chrysene is suspected to be a carcinogen for humans. Some evidence suggests that it causes cancer in laboratory animals (Talhout, Reinskje,2011), but chrysene is often contaminated with more strongly carcinogenic compounds. Chrysene is estimated to have about 1% of the toxicity of benzopyrene

(Ian C.T. Nisbet, Peter K. LaGoy, 1992).

Figure 1. Ball and stick models of phenanthrene, pyrene and chrysene

1.5 GC-MS method detect trace organic compound

GC-MS is an analytical method that combines the features of gas-chromatography and mass spectrometry to identify different substances within a test sample. GC-MS chromatography consists of two major components: the gas chromatograph and the mass spectrometer.

Typical mass spectrometry detection has two ways: full scan and selective ion monitoring (SIM).

When data is collected in a full scan, a mass segment target range is determined and entered into the instrument. The full scan is useful for determining unknown compounds in the sample. When a selected ion monitoring (SIM) ion fragment is entered in the instrument method, only those mass fragments are monitored by the mass spectrometer. The advantage of SIM is that due to the fact that the instrument only looks for a small number of fragments (for example, three fragments) at each scan, its monitoring limit is lower. In this research, SIM method is the mainly method to detect the mass distribution in the samples.

5 1.6 Objectives and hypothesis

The objective of this project is to explore the effects of photodegradation of phenanthrene, pyrene and chrysene when they are adsorbed on PE circle. The hypothesis in this project are summarized as follows:

Hypothesis 1: UV irradiation would promote the phenanthrene, pyrene and chrysene transformations to other compounds.

Hypothesis 2: Sorption of PAHs to PE circle would lead to higher photodegradation percentage of phenanthrene, pyrene and chrysene.

Hypothesis 3: Photodegradation rates of PE sorbed PAHs will be compound specific.

6 CHAPTER2 EXPERIMENTAL METHOD

2.1 Chemicals and reagents

All stock solutions used for the experiment and chemical analysis were prepared using deionized water and

the following high purity chemicals: phenanthrene (Ultra Scientific, C14H10), pyrene (Ultra Scientific,

C16H10), chysene (Ultra Scientific, C18H12), dichloromethane (DCM) (Ultra Scientific, C2H2Cl2), sodium

sulfate (Ultra Scientific, CH2Cl2), methanol (Ultra Scientific, CH3OH), US-106N-1 PAHs mixture (Ultra

Scientific).

2.2 Methanol-PAHs Samples Preparation

There are 4 samples as one set in the experiment. 24 milligrams of phenanthrene, 8 milligrams of pyrene and

6mg of chrysene were added into a 150ml volumetric flask containing 128 mL methanol. After that, stirring bar was added into the volumetric flask, then, put the flask on the magnetic platform to be stirred for 24 hours for equilibrium. When PAHs totally dissolved in the methanol, 32 mL solution was added into a 40 mL amber glass vial, and 8 mL DI water was added into the vial at the meantime. These four 40 mL vials have been shaken for one weeks to get the equilibrium between methanol-water solvent and PE circle. After that, these PE circles were added to 1000 mL goundmouth jar separately which was covered by tinfoil for shading. Then, those glass jars was shaken for 5 weeks to guarantee the equilibrium.

2.3 Photo-irradiation

Following equilibration, those fours glass jars were marked as “1”, “2”, “3” and “4”. The exposure conditions is shown as Table 1. The “1” was exposed to UV irradiation and air, “3” jar to air but not UV.

The “2” jar, was expose the to the UV and air without the PE circle. And the “4” jar were exposed to neither air nor UV as the blank control sample. The course of irradiation was 2 hours. Each experiment was repeated 7 three times, replicates are labeled a, b, and c, therefore, samples are marked a1-a4, b1-b4, and c1-c4. The irradiation intensity of UV light is 1.6 mW/cm2.

Table 1. Exposure conditions of each sample

Exposure Condition 1 2 3 4

UV light √ √ × ×

√ × Air √ √ with PE circle √ × √ √

2.4 Samples extraction

After irradiation, PE circles were added into the 40ml vials. Each PE was extracted by DCM three times, total volume of DCM was 40 mL. DI water was added into separatory funnel from the top, then, 200 mL of

DCM was added into the separatory funnel. Once the stopper was securely on, the funnel was manually shaken for 5 minutes. The funnel was shaken repeatedly and the pressure relieved until no further visible or audible evidence of gas release occurs. The funnel was then placed back in the iron rings. Two layers formed when contents in the funnel have settled. Then transferred lower layer, the DCM layer, into a round bottom flask. This operation was repeated three times. After that, drying agent (pre-combusted sodium sulfate) was added into the round bottom flask to remove the water from the organic solvent.

2.5 GC-MS sample preparation

In order to increase signal strength for GC-MS analysis, the extracted solvent was concentrated to a final volume of 2 mL or less using a rotary evaportator (Buchi, Flawil, Switzerland). Water bath was setting as 35 degrees Celsius, the vacuum pump was controlled as 400~600 mbar, in this condition, samples were distillated to about 2 mL. After distillation, 100 uL recovery standard compound (1 ug/ml, d-anthracene, d-fluoranthene, and benzo(a)anthracene) was added to each sample respectively.

2.6 Standard samples preparation 8 In order to identify the concentration and mass of PAHs in the samples, standard samples were made for

GC-MS detecting. 100 uL, 50 uL, 25 uL and 10 uL of a 2000 ug/mL standard PAHs mixture (US-106N-1) containing 16 PAHs, including phenanthrene, pyrene, and chrysene, were added to 10 mL volumetric flask separately, then the DCM was added into the flask to the calibration tail. Thus, the concentrations of standard series of PAHs mixture are 20 ug/mL, 10 ug/mL, 5ug/mL and 2 ug/mL for each PAH.

2.7 GC-MS setting

All extracts were analyzed on a GC/MS (Thermo Scientific Trace 1300, TSQ Quantum XLS Ultra, Thermo

Electron, Waltham, MA, USA). Splitless 1µL injections were made onto a 30 m Phenomenex Zebron ZB-5 capillary column (0.25 mm internal diameter with a 0.50 µm film thickness). The injection port temperature was 280º C. The column temperature began at 80º C and was raised 12º C/min until a temperature of 210º C was reached. The temperature was then raised at 6º C/min until a temperature of 320º C was reached and remained there for 2 minutes. The MS was operated in selected ion monitoring (SIM) mode at a resolution of 500 in EI+ mode.

There are three segments of SIM method. The segment 1 sustains 13.5 min, and detected center mass are

178.05, 188.05. The segment 2 sustains 4.5 min, and detected center mass are 202.05 and 212.12. The segments 3 sustains 15.5 min, and detected center mass are 228.07 and 240.110.

9 CHAPTER 3 RESULTS AND DISCUSSION

Due to some problem with the GC-MS, peak area of phenanthrene can not be read clearly. Thus, this part would put the emphasis on the pyrene and chrysene.

3.1 Pyrene results

Before running the extraction samples in the GC-MS, standard solutions of PAHs mixture in different concentrations have been run in the GC-MS, the results of standard pyrene solutions shows in the Figure 2.

Mass of Pyrene(ng)

2 4 5 8 10 20 0.00E+00 2.17E+07 5.91E+07 1.00E+08 7.77E+07 1.59E+08 2.00E+08 2.40E+08 3.00E+08 y = 6E+07x

Peak Area 4.00E+08 R² = 0.66506

5.00E+08 5.65E+08 6.00E+08

Figure 2. Pyrene Peak Area with Injection Mass

Pyrene standard curve shows that the peak area is generally linear dependence with concentration. The poor

R2 observed on this calibration curve indicated that the instrument was not running under optimal conditions.

The samples will be re-run in the future under improved conditions, however, the data obtained under current conditions are discussed in a preliminary analysis below. The response factor of pyrene is equal to peak area divided by injected mass. Each injection volume to the GC-MS was setting as 1ug per time. From the peak areas of standard solutions of pyrene, the response factor (r.f.) of pyrene is 18871220 area units.

When preparing the extracted samples, d10-fluoranthene was added into the extracted samples. According to the peak area of d10-fluoranthene in the extraction samples, the extract volume can be calculated by comparing with the recovery standard compound’s peak area. The pyrene peak area and total mass which calculated by peak area and extract volume is shown at Table 2, Table 3 and Table 4. 10

Table 2. Total mass of pyrene in the series of sample “a”

Total mass of Pyrene in the series of sample "a" (ng)

Exposure PE extraction Water extraction UV and Air 387.87 489.48 UV and Air without PE 407.28 502.62 no UV but Air 399.90 542.14 neither UV nor Air 452.02 557.25

Table 3. Total mass of pyrene in the series of sample “b”

Total mass of Pyrene in the series of sample "b" (ng)

Exposure PE extraction Water extraction

UV and Air 388.56 485.21 UV and Air without PE 487.82 519.03 no UV but Air 420.18 600.31 neither UV nor Air 422.66 591.62

Table 4. Total mass of pyrene in the series of sample “c”

Total mass of Pyrene in the series of sample "c" (ng)

Exposure PE extraction Water extraction UV and Air 392.49 501.08 UV and Air without PE 441.37 512.14 no UV but Air 428.91 588.19 neither UV nor Air 435.99 557.76

In the series of PE extraction, total mass of pyrene in the samples which exposed to the UV and air with PE circle are in the lowest level. The mass in the samples exposed to the air but no UV are the the second. And the quantity of pyrene in the samples exposed UV and air without PE circle are similar with the samples exposed to neither UV nor Air. In the series of water extraction samples, total mass of pyrene in the samples 11 exposed to UV and air are still at the lowest level, samples exposed to UV and air without PE circle at second while samples exposed to air but no UV are similar with control group.

Considering that the experiment setting of irradiation conditions, a4, b4 and c4 which samples exposed to neither UV nor air are blank control group, thus, total mass of pyrene of them are equal to original amount added to each system. The ratio of total mass of each samples to the original mass of pyrene, in each series are shown as Figure 3 and Figure 4.

In the series of PE circle extraction, the ratios of samples which irradiated by UV lamp are 5% lower than other samples, which means, photodegradation ratio of pyrene attached to PE circle in the water is higher than other samples which without UV irradiation. In the series of water extraction series, the photodegradation percentage of samples which irradiated by UV lamp are 8% lower than without irradiated samples. The differences of ratio between the samples exposed to UV and air with the samples exposed only to air illustrate that UV light is the accelerate the photodegradation of pyrene both in the water and adsorbed in PE.

Through comparing the ratios of samples exposed to UV and air with the samples exposed to UV and air without the PE circle in the water extraction series, the ratios are lower in the samples exposed to UV and air.

Which means when the PE adsorbed pyrene in the water is promote photodegradation of pyrene in the water.

1.1542 1.2 a1-a3 a5-a6 b1-b3 1.0124 0.9941 0.9838 1 0.9193 0.9002 0.9010 0.8581 0.8847 0.8

0.6

0.4 Ratio(sample to original) 0.2

0 1 2 3 Figure 3. The Ratios of PE Extraction Series 12 a1-a3 a5-a7 b1-b3 1.2 1.0545 0.9729 1.0147 1 0.8784 0.8984 0.9029 0.8773 0.9182 0.8201 0.8

0.6

0.4 Ratio(sample to original) 0.2

0 1 2 3 Figure 4. The Ratios of Water Extraction Series

13 3.2 Chrysene results

Before running the samples in the GC-MS, standard solution of PAHs mixture in different concentration has been run in the GC-MS, the results of chrysene standard solutions shows in the Figure 5.

Mass (ng)

2 4 5 8 10 0.00E+00 4.56E+06 1.00E+07 1.50E+07 1.57E+07 2.00E+07 3.00E+07 4.00E+07 Peakarea 4.42E+07 5.00E+07 y = 1E+07x 6.00E+07 R² = 0.7623 7.00E+07 7.56E+07 8.00E+07

Figure 5. Chrysene Peak Area with Injection Mass

The response factor of chrysene is equal to peak area divided by injected mass. Each injection to the GC-MS was setting as 1ug per time. From the peak areas of standard solutions of chrysene, the response factor (r.f.) of chrysene is 4451355. The poor R2 observed on this calibration curve indicated that the instrument was not running under optimal conditions. The samples will be re-run in the future under improved conditions, however, the data obtained under current conditions are discussed in a preliminary analysis below. Due to degrading instrument conditions, only two sets of data for chrysene concentrations were of sufficient quality to include in further analyses.

When preparing the extracted samples, d12-Benz(a)anhracene was added into the extracted samples to calculated the exactly extract volume through comparing with the recovery standard compound. The peak areas of chrysene in samples and total mass which calculated by peak areas and extract volumes are shown in the Table 5 and Table 6.

14 Table 5. Total mass of chrysene in series of sample “a”

Total mass of Chrysene in the series of sample "a"

Exposure PE extraction Water extraction UV and Air 1777.66 350.28 UV and Air without PE 1762.52 342.92 no UV but Air 1724.86 366.98 neither UV nor air 1765.40 351.99

Table 6. Total mass of chrysene in series of sample “c” Total mass of Chrysene in the series of sample "c"

Exposure PE extraction Water extraction UV and Air 1750.45 359.59 UV and Air without PE 1771.13 349.40 no UV but Air 1809.27 363.09 neither UV nor air 1778.97 358.86

Through comparing the total mass of different samples in one series, the effects of photolysis do not reveal obvious signs of photodegradation. The total mass of chrysene in the PE extraction samples are similar with the blank control group. While in the series of water extraction samples, the mass of chrysene in the sample which irradiated without PE circle is little lower, only 2% lower than blank control group.

3.3 Discussion

From the results of pyrene, UV irradiation promote the pyrene photodegradation. Three primary mechanisms have been proposed for photodegradation of PAHs: (1) direct photoionization or photolysis; (2) energy transfer from an excited PAH triplet state to molecular oxygen; and (3) charge or electron transfer from an excited singlet or triplet PAH state to molecular oxygen (M.P. Fasnacht, N.V. Blough,2002). Oxygen plays the important role in the photodegradaion of pyrene, however, the normal oxygen molecule can not trigger the photolysis of pyrene. UV irradiation is known to produce various reactive oxygen species, including

1 •−) singlet oxygen ( O2), superoxide (O2 , and hydroxyl radicals (•OH) (Z. Xu, C. Jing, F. Li, X. Meng, 2008).

So that the concentrations of these molecules have the impact on pyrene photodegradation. There is no doubt 15 that at the surface of the water, the concentration of singlet oxygen, superoxide and hydroxyl radicals would be much higher than in the water. These molecules would have higher possibility to combine with the pyrene when them floating on the water. When pyrene combined with superoxide would transfer to 1-hydroxypyrene, the photodegradation would start.

The outstanding photodegradation phenomenon did not exist in the chrysene samples in this project. Direct photolysis and photosensitized degradation of a trace chemical in well-mixed aqueous systems can be

described by the first-order rate law (H. Kawaguchi,1993): ln(Ct/C0) = −kt, where C0 and Ct are the reactant concentrations at irradiation time 0 and t, respectively, and k is the first-order rate constant. The rate of PAHs is determined by several conditions of irradiation, for example: PH, temperature and so on. In this project, the series of chrysene UV irradiation set was setting same as the series of other chemical sample. Photolysis rate of chrysene is slower than other chemicals may be the important reason for subtle difference, 2 hours was not enough for chrysene to finish the photodegradation as pyrene.

16 CHAPER 4 CONCLUSION

The following conclusion can be obtained by this project:

(1) The sorption of pyrene onto PE circle increases photodegradation.

(2) Measurable photodegradation of chrysene in water or PE are not observed following 2 hr exposures to

1.6 mW/cm2.

3 The effects of photodegradation caused by chemicals adhering to the PE circle are related to chemicals’ characteristics.

There are some aspects in this project that need improvement. Although the experiments were carried out in the laboratory where temperatures were 21 degree C, it is likely that the temperature at the irradiated surfaces increased during UV exposure. These temperature changes may have important effects on photodegradation rates of PAHs. In future experiments, the temperature at water and PE surfaces should be monitored. Then, the data of three or less sets can not be powerful evidence to ensure the conclusion. In the future experiment, irradiation duration could be set as 2 hr, 4 hr, and 8 hr to guarantee chemicals photodegraded. Last, by-products of PAHs’ photodegradation can be detected by GC-MS scan model in higher concentration, in the further experiment. Exploring the by-products of PE adsorbed PAHs in the water can be another aspect in the further experiment.

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