Background: Contamination of water resources with nitrate is a serious environmental problem in many regions of the world. In addition, this problem has been observed in some regions of Iran. As Nitrate is threatening for human health and environment, it must be decreased to standard levels in drinking water. Objectives: The purpose of this research was to model the nitrate removal from water by nano-scaled zero-valent iron (nZVI) using response surface methodology and to investigate the effects of the nZVI dose, nitrate concentration, contact time, and ionic strength on removal efficiency. Materials and Methods: Box-Behnken design was used. Response surface methodology was used for modeling nitrate removal. All experiments were conducted according to standard methods. Important assessed parameters included nZVI dose (0.5-2 g/L), nitrate concentration (50-150 mg/L), contact time (15-60 minutes), and ionic strength (1000-5000 μmho/cm). Results: Results indicated that there was a direct association between nitrate removal efficiency and time and nZVI dosage. Therefore, increasing of the contact time or nZVI dose would increase nitrate removal. On the other hand, the nitrate removal was decreased when ionic strength and initial concentration were increased. The analysis of variance revealed that the proposed regression model could be appropriately used to design experiments. The model correlation coefficient was 0.9992 and the adjusted value was 0.9982. Conclusions: Response surface methodology and Box-Behnken design were powerful statistical tools for navigating nitrate reduction process. The results showed that a high percentage of nitrate were reduced by nZVI and this method might be efficiently used for nitrate removal from water.

Context: The worldwide production and application of pesticides, especially organochlorine in agriculture can have adverse environmental pollution and human health risks. Thus, this review evaluated and summarized the toxicological data on the existence and concentrations of organochlorine compounds in Caspian sea fish tissues.Evidence Acquisition: The data were collected from published articles in PubMed, ISI, SID, Google Scholar and so on. Results: The review showed that nine studies were recorded in databases about pesticide residues in Caspian sea fish tissues. These studies reported that there is limited evidence of organochlorinated compounds in Caspian sea fishes. All researchers detected organochlorine contaminants in examined fishes in the studied area, however DDTs was the predominant pesticides. Heptachlor, Polychlorinated Biphenyls (PCBs) and Linden were ranked next, respectively. Conclusions:In conclusion, toxicological studies showed that, although contamination level in Caspian sea fishes was relatively low, the present status might pose a risk about food chain contamination.Keywords: Pesticide Residues, Fish, Environmental Toxicology, Systematic Review, DDTs Context Caspian SeaThe Caspian sea (CS) with a volume and surface area of 78000 km 3 and 380000 km 2 , respectively, is the biggest land body of water in the world and a unique system that is surrounded by five countries: Iran (900 km), Azerbaijan, Turkmenistan, Kazakhstan and Russia (1). The Caspian sea has about 130 river inputs, but no output (1-3). Various pollutants have accumulated in the Caspian sea due to many human activity sewages, agricultural and industrial waste flowing into the landlocked system, which threaten directly or indirectly environment and human health especially through the food chain (4, 5). Organochlorinated PesticideThe use of pesticides and fertilizers has been substantially increased to increase additional production of crops around the world as a consequence of increased human population (6-8). In spite of the potential to prevent and control insects, disease vector and weed, some pesticides such as Organochlorine pesticides (OCs) can be toxic to human health, wildlife and have deleterious impacts on the environment (9, 10). There is strong evidence on the association with a wide range of diseases and exposure to pesticides (11). Exposure to organochlorine pesticides may result in health-related complications including reproductive defects (12, 13), carcinogenic effects (14) breast cancer risk (15) and behavioral changes (16). Organochlorinated pesticides are chlorinated hydrocarbons that are composed primarily of carbon, hydrogen and several chlorine atoms per molecule (16,17). Due to their hydrophobic characteristics, resistance to degradation, toxicity, least solubility in water, bioaccumulative nature, low vapour pressures and long-range transport and trans-boundary dispersion, the control of OCs in the environment is a real necessity (6,(17)(18)(19). Some of the most representative compounds in this...