Oana Cadar

Preparation of CoFe2O4/SiO2 Nanocomposites at Low Temperatures Using Short Chain Diols

The preparation of 70% CoFe2O4/30% SiO2 (wt%) nanocomposites by sol-gel method using three short chain diols (1,2-ethanediol, 1,3-propanediol, and 1,4-butanediol) as chelators was studied. The Fourier transformed infrared spectra and X-ray diffraction patterns were used to confirm the formation of nanocomposites. The X-ray diffraction analysis showed that the chain length of the carboxylates embedded in the silica matrix influences the formation of crystallized cobalt ferrite as single phase at low temperatures. The influence of the methylene groups number in the precursors and annealing temperature on the nanocrystallite size was revealed. The stability of the obtained compounds was determined by calculation of thermodynamic parameters.

Assessment of Availability and Human Health Risk Posed by Arsenic Contaminated Well Waters from Timis-Bega Area, Romania

Mobilization of As from geological materials into ground and drinking water sources may represent an important threat to human health. The objective of this study was to assess the As concentration and availability in underground water used as drinking water sources. Water samples were collected from public and private wells in Timis-Bega area of Pannonian Basin, West Romania. Total-dissolved As measured after “classical” filtration of water samples was in the range of 0.10–168 μg L−1, thus exceeding the guideline value in majority of the samples. The aim of this study was also to assess the “truly dissolved” concentrations of As considered as available concentrations, in well waters, after passive sampling by Diffusive Gradients in Thin-films (DGT). The results showed that over 70% of total-dissolved As is in available forms. The obtained data were used to evaluate the risks of using the wells as drinking water source. Hazard quotients for ingestion and dermal pathways and hazard index (HI) for exposure to As were calculated. The HI values > 1 found that majority of samples indicated a health risk for local residents.

Chemical modeling of groundwater in the Banat Plain, southwestern Romania, with elevated As content and co-occurring species by combining diagrams and unsupervised multivariate statistical approaches.

The study proposes a combined model based on diagrams (Gibbs, Piper, Stuyfzand Hydrogeochemical Classification System) and unsupervised statistical approaches (Cluster Analysis, Principal Component Analysis, Fuzzy Principal Component Analysis, Fuzzy Hierarchical Cross-Clustering) to describe natural enrichment of inorganic arsenic and co-occurring species in groundwater in the Banat Plain, southwestern Romania. Speciation of inorganic As (arsenite, arsenate), ion concentrations (Na+, K+, Ca2+, Mg2+, HCO3-, Cl-, F-, SO42-, PO43-, NO3-), pH, redox potential, conductivity and total dissolved substances were performed. Classical diagrams provided the hydrochemical characterization, while statistical approaches were helpful to establish (i) the mechanism of naturally occurring of As and F- species and the anthropogenic one for NO3-, SO42-, PO43- and K+ and (ii) classification of groundwater based on content of arsenic species. The HCO3- type of local groundwater and alkaline pH (8.31-8.49) were found to be responsible for the enrichment of arsenic species and occurrence of F- but by different paths. The PO43--AsO43- ion exchange, water-rock interaction (silicates hydrolysis and desorption from clay) were associated to arsenate enrichment in the oxidizing aquifer. Fuzzy Hierarchical Cross-Clustering was the strongest tool for the rapid simultaneous classification of groundwaters as a function of arsenic content and hydrogeochemical characteristics. The approach indicated the Na+-F--pH cluster as marker for groundwater with naturally elevated As and highlighted which parameters need to be monitored. A chemical conceptual model illustrating the natural and anthropogenic paths and enrichment of As and co-occurring species in the local groundwater supported by mineralogical analysis of rocks was established.

Metal contents and potential health risk assessment of crops grown in a former mining district (Romania)

ABSTRACT The Cd, Cu, Pb and Zn contents in home-grown crops in a former mining district were determined in order to evaluate the non-carcinogenic long-term potential health risk related to crop consumption. The potential health risk was investigated by estimating the daily intake and the hazard quotients. For all crop categories, the daily intake and the target hazard quotient were below the threshold values for Cd, Cu, and Zn. The daily intake of Pb exceeded the oral reference dose, while the target hazard quotient for vegetables was above 1, indicating a potential health risk. The total target hazard quotient for the individual metals decreased in the following order: Pb>Cd>Cu>Zn. This study confirmed that the daily consumption of crops grown in contaminated soils could pose health risks to humans.