Phytoremediation by trees as a nature-based solution for mitigating metal contamination in urban soils.

Trace metals in the environment are important pollutants affecting human health, particularly in urban areas worldwide. Phytoremediation as a nature-based solution (NBS) and environmentally friendly technology may decrease high concentrations of trace metals in urban soils, protecting public health (especially children) and contributing to urban sustainability. This study examined trace metal contamination of urban soils and trees in six cities in the Republic of Srpska (RS), Bosnia and Herzegovina (BiH) and investigated the potential of selected tree species for phytoremediation as a NBS for metal-polluted urban soils. Contamination of urban soils was assessed by quantifying the concentrations of 11 trace metals (B, Ba, Cd, Co, Cr, Cu, Mn, Mo, Ni, Pb, and Zn). To estimate phytoremediation potential of urban tree species, concentration and bioconcentration factor of the 11 metals were quantified in leaves of three common and abundant tree species: Aesculus hippocastanum L. (horse chestnut), Platanus acerifolia Willd. (plane), and Tilia sp. (lime). The results showed that trace metal concentrations in leaf samples did not exceed toxicity threshold guideline values. Further assessments are needed to establish the true potential of the three species as NBS for urban soils.

Assessment of phytostabilization potential of two Salix L. clones based on the effects of heavy metals on the root anatomical traits.

Willow species (Salix L.) are a useful tool for assessing phytostabilization of the sites polluted by heavy metals. Phytostabilization potential of two willow genotypes (Salix alba L. clone '68/53/1' and Salix nigra Marshall clone '0408') has been evaluated in a 45-day hydroponic experiment, using stem cuttings (diameter 12 to 14 mm, length 20 cm) exposed to two concentrations (10-4 M and 10-5 M) of individually applied Cd, Ni, and Pb. Metals were diluted in 25% Hoagland's solution, in forms of CdCl2·H2O, NiSO4·6H2O, and Pb-EDTA. The control group of cuttings was grown in 25% Hoagland's solution without heavy metals. High Cd concentrations in willow roots, 8637 mg/kg (clone '68/53/1') and 6728 mg/kg of dry weight (clone '0408'), have indicated a high phytostabilization potential. However, detailed analyses of cross-sectional area of the root cortex and the central cylinder revealed that the excess concentration of Cd led to a significant reduction of measured anatomical root's traits of clone '68/53/1' in comparison with the control samples. Excessive concentration of Ni and Pb in nutrient solution increased the values of quantitatively measured root's traits of clone '0408', implying stimulatory effects of the applied concentrations. Concentration of 10-4 M of each metal had more negative effects on the roots' anatomical traits, notably on parenchymal and exodermal cells and vessels. Deposits of metals were observed in root tissues. Clone '0408' demonstrated an increased tolerance to heavy metals, which could potentially make this clone useful in phytostabilization.

A study of daily variations of the outdoor background radiation measured in continuous mode in Federation of Bosnia and Herzegovina.

Systematic monitoring of environmental radionuclides with the aim of early warning in emergency situations in Federation of Bosnia and Herzegovina (FB&H) was established in 2004. Environmental radiation monitoring network includes six automatic monitoring stations over the FB&H territory. This paper deals with the first study of ambient dose equivalent rates collected over the period of 2012-2017 with the main objective to investigate the temporal and spatial variations in the outdoor background radiation. The correlation analysis between the continuously acquired gamma dose rates and the simultaneous meteorological records on a daily basis contributed to a better interpretation of daily variations of the measured data. Derivation of the net ambient dose equivalent rates and the terrestrial radiation component from routine monitoring data was carried out as a prerequisite for adequate monitoring of background radiation. In addition, the terrestrial background component was estimated from the soil radionuclides at the same monitoring sites. The correlation analysis in a form of bivariation statistics between activity concentration of each pair of primordial radionuclides in the soil samples show that primordial radionuclides are not uniformly distributed over the FB&H territory. The mean values with the combined standard uncertainties for the terrestrial component evaluated from the soil radionuclides of (74.4 ± 12.5) nSv/h and from routine monitoring data of (81.8 ± 17.9) nSv/h are within the ranges reported for East and South European countries. The sources of statistical and systematic uncertainties were analyzed. The applied procedure of the terrestrial radiation component evaluation based on the daily monitoring data could be of complementary significance related to the existing evaluation procedures with a smaller sampling time of monitoring records. The results of the present study indicate that the acquired monitoring data are reliable enough to correctly assess the radiological situation in FB&H. In case of an emergency situation, the results obtained could be useful for a better identification of contaminated area.

Recent measurements of 234U/238U isotope ratio in spring waters from the Hadzici area.

The Hadzici area has become interesting for investigation since depleted uranium ammunition had been employed in 1995 during the NATO air strike campaign in Bosnia and Herzegovina. The purpose of this study is to determine uranium concentration and (234)U/(238)U activity ratio in the spring waters of this area and to investigate their relationship, as well as spatial variations. The spring water samples were taken at 18 sites in total. For the determination of uranium radioisotopes, radiochemical separation procedure followed by alpha-particle spectrometry was applied. Uranium concentration in analyzed waters range from 0.15 to 1.12 µg/L. Spring waters from carbonate based sediments have a lower uranium concentration of between 0.15 and 0.43 µg/L, in comparison to waters sampled within sandstone-based sediments ranging from 0.53 to 1.12 µg/L. Dissolved uranium shows significant spatial variability and correlation with bedrock type confirmed by Principal Component Analysis and Hierarchical Cluster Analysis. The majority of the analyzed waters have a (234)U/(238)U activity ratio ranging from 1.02 to 1.90, of which half of the results range between 1.02 and 1.16. No apparent depleted uranium (DU) contamination was observed, as (234)U/(238)U activity ratio is dependent on geochemical conditions in the environment. Even though the tested spring waters demonstrate significant variability in uranium concentration, (234)U/(238)U activity ratio and (234)U excess, waters with similar uranium isotopic signatures are observable within the region. The guidelines on the spatial redistribution of dissolved uranium (corresponding to (238)U mass concentration), along with (234)U/(238)U activity ratios were provided by the Inverse Distance Weighting (IDW) method. Waters having similar isotopic signature have been delineated.