Response to the comments of Zhang et al. (2014) on "heavy metals and polycyclic aromatic hydrocarbons: pollution and ecological risk assessment in street dust of Tehran"

Occurrence of heavy elements in street dust from sub/urban zone of Tianjin: pollution characteristics and health risk assessment

Main purpose of this study was to determine the concentrations of selected heavy elements (As, Cd, Pb, Cu, Co, Cr and Ni) in the street dust samples (n = 49) collected from seven districts located in suburban/urban zone of Tianjin in order to estimate their possible sources and degree of environmental pollution as well as human health risk. Mean concentrations (mg kg^-1) of As (19.3), Cd (0.60), Pb (28.4) and Cu (62.7) were above their corresponding soil background values. According to the results of multivariate statistical analysis, the accumulation of As, Cd, Pb, Cu and Cr in street dust was affected by anthropogenic activities, while the contents of Ni and Co were associated with natural sources. Pollution degree by geo-accumulation index had the following trend: Cd > Cu > As > Pb > Cr > Ni > Co. Dust contamination with Cd ranged from unpolluted to highly polluted. Potential ecological risk indicated low (Pb, Cu, Cr, Co and Ni) to high (Cd) risk, while potential risk index showed moderate and very high risks. Non-carcinogenic risk of the studied elements was below safe level (<1). Data obtained in this investigation gave the additional values to the knowledge needed for future monitoring and risk assessment, relating the presence of heavy elements studied in suburban/urban areas.

Seasonal, spatial variations and risk assessment of heavy elements in street dust from Novi Sad, Serbia

This is the first study carried out to determine the levels, spatial and temporal variations and risk indices of street dust in Serbia. Sixty street dust samples representing four functional areas: school, recreational, residential and industrial were collected from Novi Sad during summer and winter. The purpose was to obtain the concentration of seven heavy elements, evaluate the possible sources and degree of environmental pollution and human health risks. The average concentration of As, Cd, Co, Cr, Cu, Ni and Pb (mg/kg) during winter was: 7.96, 0.40, 7.73, 12.1, 57.6, 14.0 and 70.6, while in summer it was: 1.88, 0.54, 4.31, 60.1, 42.7, 28.1, and 62.5, respectively. Interpolation method together with the correlation matrix and the results of multivariate statistics supported anthropogenic origin of Pb, Cr and Cu, natural origin of Ni, Cd and As and mix origin of Co. Pollution indices such as geoaccumulation index (I_geo) indicated existence of unpolluted to extreme risk regarding to environmental pollution. Moreover, the potential pollution index (Er) showed low (Pb) to moderate (Ni) risk while potential risk index (RI) and modified potential risk index (mRI) indicated considerable and very high risks. Health risk assessment showed no non-carcinogenic risk of heavy elements for adults and children.

Integrating hierarchical bioavailability and population distribution into potential eco-risk assessment of heavy metals in road dust: A case study in Xiandao District, Changsha city, China

Modified eco-risk assessment method (MEAM) integrated with the hierarchical bioavailability determined by the fraction detection of Cd, Pb, Zn, Cu, Cr in road dust samples and the local population distribution derived from the local land use map, was proposed to make the hierarchical eco-risk management strategy in Xiandao District (XDD), China. The geo-accumulation index (Igeo), the original potential eco-risk index (Er(i)) and the modified eco-risk assessment index (MEAI) were used to identify the priority pollutant. Compared with the Hunan soil background values, evaluated metal concentrations were found to different extent. The results of mean Igeo, Er(i) and bioavailability of studied metals revealed the following orders: Cd>Pb ≈ Zn>Cu ≈ Cr, Cd>Pb>Cu>Cr>Zn and Cd>Zn>Cu ≈ Pb>Cr, respectively. Therefore, Cd was regarded as the priority pollutant. To identify the priority areas taking into account cost consideration, the hierarchical risk map based on the results of the modified eco-risk assessment index with overlay of the population density map was needed and made. The west and partly south areas of XDD were under higher eco-risk generally. Moreover, the whole XDD area was divided into 4 area categories with different management priorities based on the possibility of occurrence of eco-risk, and the hierarchical risk management strategy associated with protecting local population was suggested to facilitate allocation of funds for risk management.