**9. Preface on organochlorine chapters**

This compact book has some data on organochlorine compounds and their degradation products. Clarification of degradation processes for OC is important for polluted ecosystems. Reviews- on legislations for organochlorine compounds especially on persistent and toxic OC were shown also in this book. Analytical procedures (extraction techniques, clean-up procedures, equipment,- etc.) and experimental data for OC analysis are mentioned briefly on book chapters.-

Chapter I, "Service Sector-Based Dioxin and Furan Emissions and Management Techniques," describes PCDD/F as one of the important classes of organochlorine contaminants. This chapter presents the importance of study dioxins because they cause people's health problems. Through various studies that authors have used, this review is focused mainly on emission sources and monitoring of these contaminants in some countries in order to conclude to the situation in Ethiopia. PCDD/Fs are part of the POPs because of their persistence and toxicity. Also, in this chapter, are given data on other chlorinated compounds, classified as POPs, such as organochlorine pesticides, PCB, PBB, etc. The connection between PCDD/F and other POPs could have been clearly demonstrated.

Chapter II, "Mechanistic Considerations on the Hydrodechlorination Process of Polychloroarenes," is a review of different hydrodechlorination mechanisms for organochlorine pollutants such as PCDD/F and PCB.-These pollutants are persistent for many years because of their structure. Their presence could be for many years not only in environment but also in food chain because of bioaccumulation processes. Authors have considered different studies of hydrodechlorination mechanisms based on different redox mechanisms. These mechanisms of hydrodechlorination are important processes because degradation products usually are organic compounds with lower toxicity. Understanding these reaction mechanisms can lead to their efficient use in practice. The use of these reactions in incinerator filters and contaminated areas can bring a reduction of PCDD/PCDF and PCB pollution.-

Chapter III, "Application of Heterogeneous Catalysts in Dechlorination of Chlorophenols," is a review on heterogeneous catalysts for dechlorination of chlorophenols. These compounds are widely distributed especially in waste and surface waters because of household products, urban wastes and other chlorinated compounds such as pesticides. Heterogeneous catalyst can replace the homogeneous catalyst to solve the catalyst recycling problem, especially for the precious metal catalysts. The heterogeneous catalyst costs are more reduced than homogeneous catalyst. Dechlorination of chlorophenols using heterogeneous catalyst could be useful for dechlorination of other chlorinated compounds.
