RESUMEN
The consequence of carcinogenic and non-carcinogenic health risks of the heavy metal concentrations in street dust of North Cyprus is yet to be reported. This study is aimed at investigating the concentration of six different heavy metals' concentration explicitly: As, Cu, Zn, Ni, Cr, and Pb, along leading highways in Nicosia. The result obtained was analyzed using an X-ray fluorescent machine. Multivariate and statistical methods were applied for the data analysis using xlstat MS-excel; furthermore, index of geo-accumulation (Igeo) and human health risk assessment using exposure pathways as defined by United State Environmental Protection Agency (USEPA) pollution mode were also used for level assessment and health risk implications. The average (M ± SD) concentrations of the metals in the dust are as follows: As (17.48 ± 1.53 mg/kg), Cu (51.86 ± 8.60 mg/kg), Cr (321.14 ± 8.20 mg/kg), Pb (35.62 ± 8.54 mg/kg), Ni (64.79 ± 8.72 mg/kg), and Zn (136.13 ± 30.85 mg/kg). Variation coefficient, Vc, and principle component analysis (PCA) suggested that As, Cr, Ni, and Pb have same source of pollution emission from both natural and anthropogenic activities, Zn from traffic emission while Cu from natural source. However, the result was compared with other nearby towns bordering North Cyprus; all the metal shows similar pattern of pollution with the exception of Cr which is 5 and 11 times higher than street dust of Amman (Jordan) and Tokat (Turkey), respectively. Additionally, Igeo result has the following decreasing order: Zn > Cr > Pb > Ni > Cu > As and also revealed that the As, Cu, and Ni have originated from natural source. Cr has mix source: one from traffic and the other one from atmospheric deposition. Also, Pb is emitted from industrial pollution, whereas 80% of Zn are from traffic-related emissions. The non-carcinogenic health risk (hazard quotient (HQ) and hazard index (HI)) follows the order Cr > As>Ni > Pb > Zn > Cu for children and adults. It is found that the HI of As, Cu, Ni, Pb, and Zn is less one; hence, the street dust does not exhibit non-carcinogenic health risk. But that of Cr content is greater than one, with HI values of Cr 1.44E+02 and 1.55E+01 for children and adults, respectively. The result for carcinogenic health risk (total cancer risk (TCR)) has the following order: Pb (1.42E-05) > Cr (4.81E-09) > (Ni 1.35E-09) > As (1.96E-10). With all the values less than threshed hole limit of TCR ≥ 10-4, street dust does not possess carcinogenic health risk for the entire values of six heavy metals considered in this work.
Asunto(s)
Carcinógenos/análisis , Polvo/análisis , Contaminación Ambiental/análisis , Metales Pesados/análisis , Adulto , Carcinógenos/química , Niño , Ciudades , Chipre , Humanos , Industrias , Jordania , Metales Pesados/química , Medición de Riesgo , TurquíaRESUMEN
The present study is about the enhancement in ozone-mediated degradation and UV (254nm) photolysis of phenol in aqueous solutions by 300kHz acustic cavitation and the selection of operating parameters for optimum phenol removal efficiency. The method was based on monitoring of the concentration of phenol during 90min exposure to ozonation, sonication, UV photolysis, O(3)/ultrasound, UV/ultrasound and O(3)/UV/ultrasound operations. It was found that ozonation at alkaline pH was an effective method of phenol destruction, but it was considerably more effective when applied simultaneously with ultrasonic irradiation. The observed synergy particularly at alkaline pH was attributed to combined effects of: (i) increased ozone mass transfer (upon hydrodynamic shear forces created by ultrasonic bubbles) and (ii) excess hydroxyl radical formation (upon thermal decomposition of ozone in the gaseous cavity bubbles). Degradation of phenol by photolysis alone was negligible, while combination of UV-irradiation and ultrasound rendered considerable degrees of decay. The synergy here was explained by excess hydroxyl radicals that are formed by photolysis of ultrasound-generated H(2)O(2). Maximum rate of phenol degradation was observed in case of combined application of ozone, UV and ultrasound at basic pH.
Asunto(s)
Fenol , Ultrasonido , Eliminación de Residuos Líquidos/métodos , Contaminantes Químicos del Agua , Purificación del Agua/métodos , Catálisis , Concentración de Iones de Hidrógeno , Oxidantes Fotoquímicos/química , Oxidación-Reducción , Ozono/química , Fenol/química , Fenol/efectos de la radiación , Rayos Ultravioleta , Contaminantes Químicos del Agua/química , Contaminantes Químicos del Agua/efectos de la radiaciónRESUMEN
Ultrasonic removal of phenol under irradiation at 20, 300 and 520 kHz was investigated to assess the impacts of operating parameters on the efficiency of the systems. It was found under our experimental conditions that 20 kHz was the least effective frequency for ultrasonic decomposition of phenol, owing to the low volatility of phenol and the slow rate of OH radical ejection to the bulk solution at this frequency. Assessment of relative rates of destruction and ultrasonic yields showed that maximum efficiency was accomplished with 300 kHz employed in a reactor enclosed with an ultrasonic energy of 14.7 W. The same reactor and frequency was found to provide maximum ejection of hydroxyl radicals to the solution. Impacts of pH and initial concentration on the efficiency of phenol removal were such that acidic pH and high concentrations accelerated the process as related to the increased likelihood of phenol at these conditions to approach the cavity sheath. Separate injection of equivalent volumes of air and argon into the reactors showed that the decomposition was enhanced in the presence of air by virtue of the production of additional reactive species via the reaction of nitrogen with molecular oxygen.