Bisfenol A'nın fotokimyasal ileri oksidasyon prosesleri ile arıtımında toksisite ve östrojenik aktivite değişimleri
Toxicity and estrogenic activity changes during treatment of bisphenol A by photochemical advanced oxidation processes
Yazar: DUYGU DURSUN
Danışman: DOÇ. DR. TUĞBA ÖLMEZ HANCI
İstanbul Teknik Üniversitesi / Fen Bilimleri Enstitüsü / Çevre Bilimleri Ana Bilim Dalı / Çevre Bilimleri ve Mühendisliği Bilim Dalı
Derece: Yüksek Lisans, 2014
Konu: Çevre Mühendisliği = Environmental Engineering

Özet:
Endokrin bozucular, endokrin sistem tarafından sentezlenen endojen kimyasalların aktivitelerini bir şekilde taklit ettikleri, blokladıkları ya da değiştirdikleri için özel ilgi konusudurlar. Diğer birçok organın yanında, özellikle üriner sistemi ve tiroid bezlerini etkilemektedirler. Endokrin bozucu kimyasallar östrojen ve androjen reseptörleri ile reaksiyona girip, endojen hormonların agonist ya da antagonistleri olarak etki gösterebilirler. Son on yılda reprodüktif organ anomalikleri, testiküler kanser, erkek doğum oranlarında azalma ve semen kalitesinde düşme rapor eden birçok çalışma yayınlanmıştır. Endokrin bozucu bileşiklere örnek olarak gösterilebilen Bisfenol A (BPA) kimyasalı yıllık 1,7 milyar kg civarındaki üretim miktarı ile son yıllarda dikkatleri üzerine çekmektedir. Epoksi reçineler, deniz ürünleri, sebzeler, bira, alkolsüz içecekler, süt tozu gibi gıda ve içeceklerin ambalajlanmasında kullanılan metal kutuların iç yüzeyinin kaplanmasında, şarap ve su gibi sıvıların bulunduğu depolama kapları ile değişik tiplerdeki gıda taşıma kaplarının yapılmasında kullanılan BPA'nın düşük dozlarda bile endokrin sistemi olumsuz yönde etkileyebildiği, merkezi sinir sistemi ve immün sistem üzerinde olumsuz etkilere neden olabileceği bilinmektedir. 
Bu deneysel çalışmanın amacı endokrin bozucu özellikleri, besin zinciri içinde birikmesi ve özellikle kanserojenik etkiye sahip olması nedeni ile tehlikeli kirleticiler arasında yer alan BPA model kirleticisinin etkin arıtımını (ana madde giderimini ve mineralizasyonunu) sağlamak için sülfat radikali (SO4•-) bazlı persülfat (PS) /UV-C ve hidroksil radikali (HO•) bazlı H2O2/UV-C fotokimyasal ileri oksidasyon proseslerinin kullanılabilirliğinin araştırılmasıdır. Bu ileri oksidasyon proseslerinin etkinliğinin ortaya konması ve karşılaştırma yapılabilmesi amacı ile BPA'nın UV-C fotolizi ile de giderimi araştırılmıştır. Çalışmada aynı zamanda arıtım esnasında ve sonunda toksisite ve östrojenik aktivite de meydana gelen değişimlerin belirlenmesi amaçlanmıştır. 
Bu amaç doğrultusunda yapılan çalışmalarda optimum arıtma koşulları olarak belirlenen 2,5 mM oksidan konsantrasyonu; 20 mg/L BPA=88 μM model kirletici konsantrasyonu ve 6,5 başlangıç pH değerinde BPA model kirleticisinin PS/UV-C ve H2O2/UV-C deneylerinin yürütülmesi ve zamana bağlı olarak ana madde, toplam organik karbon (TOK) ve teorik olarak hesaplanan ara ürün toplam organik karbon parametrelerin değişimleri incelenmiştir. Çalışmanın ikinci aşamasında ise reaksiyon esnasında belirli dakikalarda alınan numunelerde üç farklı test organizması (Vibrio fischeri, Daphnia magna, Pseudokirchneriella subcapitata) kullanılarak toksisite (zehirlilik) ölçümleri, maya hücreleri (yeast) kullanılarak östrojenik aktivite ölçümleri gerçekleştirilmiştir. Yürütülen bu denesel çalışmalar ile BPA'nın belirtilen koşullardaki arıtımı sırasında oluşan oksidasyon ürünlerinin toksik ve östrojenik etkiye sahip olup olmadığı ve reaksiyon süreleri sonunda gözlemlenen toksisite ve östrojenik aktivite giderim seviyeleri belirlenmiştir. 
Bu çalışmada elde edilen sonuçlar doğrultusunda sadece UV-C fotolizinin kullanıldığı deneysel çalışmalarda etkin bir ana madde ve TOK giderimi sağlanamazken PS/UV-C ve H2O2/UV-C fotokimyasal ileri oksidasyon proseslerinde BPA model kirleticinin yedi dakikadan daha kısa sürelerde (PS/UV-C için beş dakika, H2O2/UV-C için yedi dakika) etkin bir şekilde arıtıldığı görülmüştür. TOK parametresi ile ifade edilen organik madde giderimlerine bakıldığında ise 120 dakikalık arıtım sonucunda PS/UV-C ve H2O2/UV-C prosesleri için sırasıyla %70 ve %85 mertebelerinde mineralizasyonun sağlandığı belirlenmiştir. 
BPA model kirleticisinin Vibrio fischeri, Daphnia magna, Pseudokirchneriella subcapitata test organizmaları kullanılarak belirlenen, test organizmasında % 50 inhibisyona neden olan etkin konsantrasyon değerleri sırası ile; 5,13±0,34, 11,83±0,23, 18,41±3,65 mg/L, olarak tespit edilmiştir. Elde edilen sonuçlar ışığında BPA model kirleticisinin farklı test organizmalarına karşı toksisitesi azalan hassasiyete göre Vibrio fischeri > Daphnia magna > Pseudokirchneriella subcapitata şeklinde bulunmuştur. 
BPA'nın UV-C fotolizi ile arıtımında organik madde için olduğu gibi toksisite ve östrojenik aktivite parametrelerinde de etkin bir giderim sağlanamamıştır. PS/UV-C ve H2O2/UV-C prosesleri ile BPA arıtımında reaksiyon süresi boyunca oluşan ara ürünlere bağlı olarak toksisite parametresinde test organizmasının hassasiyetine göre değişiklikler gözlenmiştir. PS/UV-C prosesi için çalışılan test organizmalarından sadece Daphnia magna'nın toksisitesi reaksiyonun sonunda tamamen giderilirken, H2O2/UV-C prosesi için ise Daphnia magna toksisitesinin yanı sıra Vibrio fischeri toksisitesinin de giderimi sağlanmıştır. Pseudokirchneriella subcapitata toksisitesi ise çalışılan arıtma prosesleri ile etkin bir şekilde giderilememiştir. Her iki proses için de (PS/UV-C ve H2O2/UV-C) maya test organizmaları ile ölçülen numunelerin östrojenik aktiviteleri reaksiyonun ilk dakikalarında BPA giderimi ile orantılı olarak azalmış ve ortamdaki BPA'nın giderilmesi sonrasında östrojenik etki de tamamen giderilmiştir.

Abstract:
Endocrine disruptors are of special interest because they mimic, block, or in some way alter the activity of endogenous chemicals that are synthesized by the endocrine system. Besides many other organs, they especially affect the urinary system and the thyroid glands. Endocrine-disrupting chemicals are typically identified as compounds that can interact with oestrogen or androgen receptors and thus act as agonists or antagonists of endogenous hormones. During the last decade, numerous studies have been published, reporting an increase in reproductive organ anomalies, as well as in testicular cancer, and a decline in the relative number of male births, and in semen quality. 
Bisphenol A (BPA) is considered as an anthropogenic type endocrine disruptor and it is primarily used in the production of epoxy resins and polycarbonate products. Polycarbonates have many applications in the manufacturing of many consumer products, such as food and drink packaging, compact disks, automotive lenses, medical devices, motorcycle helmets, and safety glasses. Crosslinked epoxy resins are used as protective coatings for food and beverage cans, anti-corrosion coatings for floors, heat resistance aerospace vehicles, PVC pipes and car.
BPA has escaped into the environment through a number of routes, including discharge of wastewater and wastewater generated from BPA production facilities or consumer product manufacturing facilities that utilize BPA, discharge of effluent from wastewater treatment plant, leaching from consumer products containing BPA at hazardous waste landfill sites, deposition of particulates or dust from BPA production, processing, or storage facilities, and accidental discharge. Studies on humans and laboratory animals indicated that BPA causes adverse health effects: estrogenic potency, liver damage, pancreatic β-cell function disruption, thyroid hormone disruption, obesity-promoting effects, and increases the prevalence of cardiovascular disease, diabetes, and liver-enzyme abnormalities. Bisphenol A is an endocrine disruptor, which can mimic estrogen and may lead to negative health effects. Therefore, BPA must be removed from water before it can be used for domestic applications. 
Children may be more susceptible to BPA exposure than adults. A recent study found higher urinary concentrations in young children than in adults under typical exposure scenarios. In adults, BPA is eliminated from the body through a detoxification process in the liver. In infants and children, this pathway is not fully developed so they have a decreased ability to clear BPA from their systems. It is also estimated that from food consumption, infants and young children have higher BPA-exposure than adults.
Studies have found that fetuses and young children exposed to BPA are at risk for secondary sexual developmental changes, brain and behavior changes and immune disorders.
The efficient treatment of micropollutants including environmental estrogen has become an important priority task to protect terrestrial and aquatic environments from ecotoxicological impacts of these pollutants. In order to solve this pollution problem, a variety of different advanced treatment processes have so far been proposed and developed. Advanced Oxidation Processes (AOPs) are among the most promising chemical treatment technologies for the treatment of organic pollutants of different chemical composition. AOPs are based on the generation of very reactive free radicals which react almost indiscriminately with most organic contaminants. For this reason, AOPs are anticipated to play a crucial role in water/wastewater treatment as stand-alone processes or in combination with conventional technologies. Recently, chemical oxidation processes involving the production of sulfate radicals (SO4•−) have been explored.
This relatively less studied treatment system may be an attractive alternative to the well-known and established hydroxyl radical (HO•) based AOPs, whose limitations and drawbacks such as nonselectivity, high electrical energy consumption, harsh operation conditions that have considerably hindered their full-scale application. The SO4•− is strongly oxidizing and has shown high efficiency in degrading organic pollutants in aqueous medium. However, the information regarding the process performance, reaction kinetics, degradation mechanisms, identification of oxidation products and their ecotoxicologic effects by SO4•− is very limited.
Advanced oxidation processes (AOPs) have been widely used in water and wastewater treatment for the removal of organic and inorganic contaminants as well as to improve biodegradability of industrial wastewater. Unfortunately, the partial oxidation of organic contaminants may result in the formation of intermediates more toxic than parent compounds. In order to avoid this drawback, AOPs are expected to be carefully operated and monitored, and toxicity tests have been used to evaluate whether effluent detoxification takes place. 
In this experimental study, BPA, which was regulated world wide due to its carcinogenic and endocrine disrupting effects, was chosen as the model compound. The performance of UV-C photolysis, persulfate (PS)/UV-C and hydrogen peroxide (H2O2)/UV-C oxidation processes in the degradation and mineralization of aqueous BPA solutions was investigated and the toxicity of the photochemical degradation products was evaluated in accordance with the Vibrio fischeri, Daphnia magna, Pseudokirchneriella subcapitata inhibition test and yeast estrogen screen assay (YES). In addition, the changes in advanced oxidation rates, parent compound and TOC removal efficiencies were also investigated. Within the aim of this study, monitoring and comparing the reaction according to its mother compound, TOC and toxicity levels and to identfy their relationship and by this way, clarify the mother compounds and intermadiate compounds inhibition potentials. 
As first step of this examination, treatment processes have been occurred at the best monitoring and efficient conditions (20 mg/L BPA=88 μM, PS/H2O2=2,5 mM, pH=6,5). Saples had been taken at the 0, 1, 3, 5, 7, 10, 30, 60, 90 and 120 minutes.  As second step, chosen model pollutant's (BPA) toxicity effects and end products causing inhibition levels had been determined. This study consists of five chapters.
In the first chapter, the purpose and scope of the study was described briefly. Some basic information about advenced oxidation processes (PS/UV-C, H2O2/UV-C), sulfate radical (SO4∙-) and hydroxyl radical (HO∙) and toxicity test basis was given in this chapter.
In the second chapter, classification of endocrine disruptors, properties, toxicity, and treatability of BPA were defined. Also AOPs and photochemical oxidation fundamentals were defined. In the end of the chapter, sulfate radical (SO4•-) based photochemical AOPs were described (persulfate/UV-C), the fundamentals and basic reactions were explained. The metodology and applicability of AOPs on endocrine disruptors oxidation were also explained in this chapter.
In the third chapter, the materials and methods were introduced which were used during the experimental part of the thesis. Since three different processed were used, three different treatment methods were explained. For every process the same analytical analysis were applied to the sampes in order to follow the treatment efficiency such as BPA determination by HPLC and TOC analysis.
In the fourth chapter treatment of BPA, toxicity and estrogenic activity changes during the the treatment were investigated. Experimental results were also evaluated and discussed in this chapter.
In the last chapter of the study the results were briefly evaluated and the most important results were stressed by the explanation of importance and some suggestion was given for further investigation.
This experimental study showed that; with only UV-C process there was no efficient treatment on BPA, TOC and toxicity parameters. PS/UV-C as well as H2O2/UV-C processes were very effective for the treatment BPA. BPA was completely removed in less than seven minutes (five minutes for PS/UV-C, seven minutes for H2O2/UV-C). During PS/UV-C and H2O2/UV-C oxidation of BPA 70% and 85% TOC removal, was achieved with 120 minutes of treatment, respectively. To identify the inhibition effect of BPA chemical towards Vibrio fischeri, Daphnia magna, Pseudokirchneriella subcapitata test organizms, EC50 values had been calculated. The calculated EC50 values were 5,13 ± 0,34 mg/L, 11,83 ± 0,23 and  18,41 ± 3,65 mg/L for Vibrio fischeri Daphnia magna and Pseudokirchneriella subcapitata respectively. In light of the results obtained, BPA model compounds toxicity against different test organisms by decreasing the sensitivity of Vibrio fischeri> Daphnia magna> Pseudokirchneriella subcapitata as recorded. 
Results of this experimental study showed that, photolysis of BPA with UV-C treatment as for the organic material toxicity and estrogenic activity parameters has not been achieved in an efficient removal. During the treatment of BPA with PS/UV-C and H2O2/UV-C processes, there were observed some changes depending on intermediate products, according to the test organisms sensitivity. PS/UV-C process for the Daphnia magna test organism, toxicity parameter was completely removed at the end of the reaction. During the H2O2/UV-C process for the Daphnia magna toxicity as well as Vibrio fischeri toxicity the removal was provided too. Pseudokirchneriella subcapitata toxicity with the studied treatment processes could not be eliminated effectively. Pseudokirchneriella subcapitata toxicity with the studied treatment processes could not be eliminated effectively. For both processes (PS/UV-C and H2O2/UV-C) the estrogenic activiti that measured by using yeast cells decreace in the first minutes with the removal of BPA. After the removal of the BPA, the estrogenic activity have complately removed.