Moreover, the beach is a distinctive space where visitors simultaneously come into contact with air, water and sand while beach bathing. Visitors are then indiscriminately exposed to phthalates in the beach environment. This study includes the phthalate determination of the spring and summer seasons in 2017 to observe seasonal differences in phthalate concentrations on the beaches. Phthalates in the beach seawater were extracted by stir bar sorption extraction (SBSE), desorbed and concentrated by thermal desorption (TD) and automatically injected into the analytical instrument, a gas chromatograph coupled to a mass spectrometer (GC/MS).
As a result, in general, the total concentration of each phthalate in beach seawater was similar or slightly lower than in other studies conducted in China, Spain, and other countries. It appears that seasonal high rainfall during the summer may have reduced phthalate concentrations in seawater at the beach. We tried to determine the content of phthalates in beach sand in order to observe the distribution of phthalates in the beach environment.
It was expected that phthalates with high Kow would migrate to sand, which is more hydrophobic than water, so that phthalate concentrations in the sand would be higher than in the beach seawater. The occurrence of phthalates and the trend in the 5 beaches cannot be generalized only with the results of 2 seasons.
Why Phthalates and Beaches?
History of Phthalates
Phthalates were introduced in the perfume industry in the 1910s for the base solvent5) and the plasticizer industry for cellulose nitrate in the 1920s6). As phthalate uses increased, users began to wonder about the safety issues of phthalates, such as likelihood of exposure to phthalates and the toxicity of phthalates. Consequently, researchers investigated physicochemical characteristics of phthalates, the migration of phthalates from phthalate-containing packaging to products, human exposure to phthalates, toxicity of phthalates and phthalate concentrations in environmental matrices.
In the case of South Korea, phthalates did not seem to be well known until the mid-1990s. From 1971 to 1995, the number of newspaper articles on phthalates was reported as infrequently as 0.5 newspaper articles per year (Figure 6). The number of articles has gradually increased since 1996 and peaked in 2015 with the discovery of phthalates in several products such as milk powder, cosmetics, IV bags, perfumes and toys. Number of newspaper articles on phthalates in South Korea from 1970 to present (November 2017).
Phthalates in Our Surroundings
Throughout the water cycle, most of the water is stored in the ocean and organic compounds follow the water cycle (Figure 8). Phthalates also circulate and follow the water cycle by volatilization into the atmosphere, dissolution in water, and deposition. The beach is an interface between people and the ocean and a distinctive space where people contact the atmosphere, seawater and sand at the same time.
Humans emit phthalates to the beach, just as they are exposed to the phthalates in the beach. In addition, rivers convey the traces of human life from the land to the beach. That is, the beach can be a representative space to show the exchange of phthalates between nature and people and its impacts.
Research Aim
It is difficult to determine phthalates in environmental matrices as they are easily contaminated by the environment and have lower concentration compared to other synthetic organic chemicals. Despite these facts, the reason I targeted phthalates is based on the thought that phthalates are the closest chemicals to humans. Therefore, the observation of phthalates can be a window showing the interactions and communications between nature and humans.
For the first step to uncover the 'ping pong', phthalate concentrations were determined in beach seawater and sand. Through the analyses, the impact of human activities on phthalate concentrations on the beaches was observed (Figure 9). The target beaches were five beaches: Ilsan and Jinha beaches in Ulsan, Imnang, Songjeong, and Dadaepo beaches in Busan, Korea (Figure 10).
At the five beaches, samples of superficial beach seawater and superficial beach sand were collected at the marked location in Figure 10. The phthalates in the seawater and sand on the beach were analyzed using a gas chromatograph in combination with a mass spectrometer (GC/MS) using of sorption extraction with stir bars. (SBSE) and/or thermal desorption (TD) as pretreatment.
Determination of Phthalates
Overview of Phthalates Determination
Principles of Pretreatment Methods – SBSE and TD
In addition, phthalates have a relatively high hydrophobicity, so phthalates are sometimes adsorbed on the surface of the container wall. Thus, stir bar sorption extraction (SBSE) and thermal desorption (TD) were proposed as pretreatment methods due to their convenience and higher recovery rate. These methods are known as green technologies because organic solvents are not required during the pretreatment process32) (Table 7). SBSE is a method of extracting organic compounds in a liquid matrix by stirring with a polydimethylsiloxane (PDMS)-coated stir bar33) (Figure 12).
Organic compounds are not adsorbed on the surface, but absorbed into the hydrophobic PDMS matrix during mixing. Therefore, it can be assumed that the partition coefficient between PDMS and water (KPDMS/w) is proportional to the octanol-water partition coefficient (Kow) at equilibrium. Based on the relationship between KPDMS/w and Kow, it can be argued that the theoretical SBSE recovery is in equilibrium.
In this research, the volume of water sample is 25 mL and the volume of PDMS is 0.165 mL when the polymer coating is assumed to be 100 % PDMS. In this case, the theoretical recovery rate of the 6 phthalates can be expected according to their Kow (Figure 13). The TD instrument desorbs volatile or semi-volatile organic compounds in the solid matrix by heating, concentrates the desorbed compounds, and injects the concentrate into a gas chromatograph coupled with mass spectrometer (GC/MS).
Optimization of SBSE Conditions
If reproducibility for extraction recovery is guaranteed, it is reasonable to use a shorter extraction time. From the optimization, 6 phthalates are divided into 2 groups which are the less hydrophobic phthalates (DMP and DEP) having lower Kow and the more hydrophobic phthalates (DnBP, BBP, DEHP and DnOP) having higher Kow. The higher Kow group shows higher recovery rates as the stirring speed increases, while there are no significant differences in the case of the lower Kow group.
It appears that compaction of interface layer between PDMS and water as stirring speed is increased34) so that mass transfer of phthalates has high. Furthermore, water salinity, which was adjusted in the same way as seawater, may aid the migration of the more hydrophobic phthalates. In particular, the salting-out effect means that more hydrophobic molecules are easily absorbed in PDMS, so DEHP and DnOP should have higher recoveries than DnBP or BBP.
However, DnBP and BBP had the highest recovery rate because they are contaminated from the laboratory environment. DnBP is used for the production of paints, cosmetics and food packages, while BBP is used for building materials and vinyl products38). The period when we run the optimization experiment was right after the laboratory moved to a new building, so evaporation from the building would be one of the reasons.
In addition, sealing materials such as aluminum foil and parafilm were other reasons that could be in contact during sample preparation or mixing. Optimization experiments for stirring sorption extraction conditions in terms of stirring time and speed.
Phthalates in Real Beach Seawater
In terms of sampling sites, the beaches appeared to be divided into 3 categories based on the median of each phthalate (Figure 16). DnBP is lower than DEHP in group 2, but DnBP is similar or higher than DEHP in other groups. Group 1 beaches are located in Busan, but Group 2 beaches are located in Ulsan.
The regional differences may affect the phthalate concentration in beach seawater, and additional factors will be needed to find the relationship between region and phthalate concentrations.
Phthalates in Real Beach Sand
In spring, the total concentration of 4 phthalates was about 0.2 μg/L at Ilsan beach, and it was the lowest concentration among the 5 beaches (Figure 18). The decrease in phthalate concentration appears to be due to more precipitation in summer than in spring. The total concentrations of the 4 phthalates ranged from 0.17 μg/L to 0.69 μg/L, and the mean total concentration of the 5 beaches in 2 seasons is about 0.42 μg/L.
The impact of phthalates in seawater can be considered negligible due to their trace concentration. This amount is more than 5 times of "The Great Pacific Garbage Patch", i.e. the plastic island in the Pacific Ocean, which is estimated at 0.1 billion tonnes43) and has an area 7 times larger than the Korean Peninsula. It's just an assumption, but the mass of phthalates in the seas, oceans and bays of the earth is quite meaningful considering other toxic organic compounds.
It is difficult to generalize the trend of phthalate occurrence through data from only 2 seasons. Additionally, it is hoped that worldwide phthalate mapping of beaches and oceans will be done with other researchers around the world. Salapasidou, M.; Samara, C.; Voutsa, D., Endocrine-disrupting compounds in the atmosphere of the urban area of Thessaloniki, Greece.
Tlili, K.; Labadie, P.; Blanchard, M.; Teil, M.; Desportes, A.; Bourges, C.; Alliot, F.; Chevreuil, M., Presence of phthalates and PBDE in air, atmospheric deposits and sludge from the Paris agglomeration. Hajmohammadi, M.; Fatemi, M.; Taneh, T., Coacervative extraction of phthalates from water and their determination by high-performance liquid chromatography. Huang, P.-C.; Tien, C.-J.; Sun, Y.-M.; Hsieh, C.-Y.; Lee, C.-C., Occurrence of phthalates in sediment and biota: relationship to aquatic factors and the accumulation factor of biota-sediment.
넷, S.; 델몬트, A.; 셈페레, R.; 팔루셀리, A.; Ouddane, B., 환경 매트릭스(공기, 물, 슬러지, 침전물 및 토양)에서 프탈레이트의 신뢰할 수 있는 정량화: 검토. 가오, D.-W.; Wen, Z.-D., 환경 내 프탈레이트 에스테르: 폐수 처리 과정 중 프탈레이트 에스테르의 발생, 생분해 및 제거에 대한 비판적 검토. 석사과정 동안 많은 도움을 주신 모든 분들께 감사의 말씀을 전하고 싶습니다.
Phthalate Maps – First Step to Changes
Significance and Value of the Research
