Nickel accumulation and its effect on biomass,protein content and antioxidative enzymes in roots and leaves of watercress(Nasturtium officinale R.Br.)

In order to understand its response towards nickel stress, watercress （Nasturtium officinale R. Br.） was exposed to nickel （1-25 mg/L） for 1, 3, 5 and 7 days. The accumulation and translocation of nickel were determined and the influence of nickel on biomass, protein content and enzymatic antioxidants was examined for both roots and leaves. It was determined that N. o fficinale could accumulate appreciable amounts of Ni in both roots and leaves. Nickel accumulated particularly in the roots of plants. Biomass increased at low nickel concentrations but certain measurable change was not found at high concentrations. Under stress conditions the antioxidant enzymes were up-regulated compared to control. An increase in protein content and enzyme activities was observed at moderate exposure conditions followed by a decline at both roots and leaves. The maximum enzyme activities were observed at different exposure conditions. Our results showed that N. officinale had the capacity to overcome nickel-induced stress especially at moderate nickel exposure. Therefore, N. officinale may be used as a phytoremediator in moderately polluted aquatic ecosystems.

Comprehensive chemical characterization of PM_(2.5) in the large East Mediterranean-Middle East city of Beirut,Lebanon

The chemical composition of PM_(2.5) at two sites in Lebanon,a country in the East Mediterranean-Middle East region,is investigated in the spring and summer seasons.The average PM_(2.5) concentrations were of(29±16)μg/m 3 for Beirut urban site and(32±14)μg/m 3 for Beirut suburban site.This study showed that the geographic location of the East Mediterranean region,such as its proximity to the Mediterranean Sea and the dust storm intrusion are a significant contributor to the high PM levels from natural sources,which cannot be mitigated,rendering the PM_(2.5) WHO annual Air Quality guideline unattainable due to high natural background,which also applies to the entire Middle East region.Turkey and Eastern Europe are the dominant origin of air masses throughout our sampling days,suggesting the long-range transport as an important potential contributor to the high observed concentrations of V,Ni,and sulfate in this region most probably in other East Mediterranean countries than Lebanon too.Main local sources determined through the chemical speciation including organics are road transport,resuspension of dust and diesel private generators.A health risk assessment of airborne metals was performed and the carcinogenic risk for all the metals exceeded by 42(adults)and 14(children)times the acceptable risk level(10^(-6))at both sites.Vanadium was the predominant carcinogenic metal,emphasizing the need to replace energy production with cleaner energy on a regional level and highlighting the severe impact of air pollution on the health of inhabitants in this region’s main cities.