Long-term TNT and DNT contamination: 1-D modeling of natural attenuation in the vadose zone: case study, Portugal

The vadose zone of a trinitrotoluene (TNT) and dinitrotoluene (DNT) contaminated site was investigated to assess the mobility of those explosives under natural conditions. Located in the left margin of the River Tejo Basin, Portugal, the site is located on unconsolidated sediments. Wastewaters associated with the 50-year explosives production were disposed in excavated ponds, from where water would infiltrate and pollute the unsaturated and saturated parts of the local aquifers. Two boreholes were drilled to 9 m depth in such a former waste pond to investigate the contaminant's fate in the vadose zone. Sediment samples were taken every 1-2 m for analysis of the polynitroaromatics (p-NACs) and organic volatile compounds, pH, organic carbon content, cation exchange capacity and grain size analysis. The main contaminant was TNT representing >70 % of the total p-NACs concentration that peaked approximately 7 mg/kg in one borehole, even if the median in both boreholes was of similar to 1 mg/kg. DNT was 4-30 % of the total p-NACs and nitrotoluene (NT), up to 5 %. No other (volatile) organic compound was detected. The predominance of TNT as the main contaminant implies that any natural mass reduction has been inefficient to clean the site. Several 1-D model simulations of p-NACs cleaning of the vadose zone under natural conditions indicated that the most probable scenario of combined advection and partitioning will only remove TNT after 10's of years, whereas DNT and NT will hardly be removed. Such low concentrations and long times for the p-NACs removal, suggest that by now those compounds have been washed-out to a level below standard limits

Temporal Changes in Air Quality during a Festival Season in Kannur, India

This study looked at the variation in air quality during the periods of fireworks as assessed from the change in ambient concentrations of air pollutants like particulate matter (PM10), O3, and NO2 for pre-, post-, and Vishu days for four consecutive years in 2015, 2016, 2017, and 2018 in Kannur, India. Enhanced levels of O3, NO2, NO, and PM10 were observed during the intense usage of fireworks. The concentration of metals in PM10 increased and the percent increase was found to be different for metal traces. A pronounced increase in the aerosol optical depth (AOD) in the lower wavelength region of solar radiation reveals the abundance of fine mode particles. The concentrations of O3 and NO2 were observed to increase by more than 100% on Vishu day than the control days for the observational period. Simulation using the National Center for Atmospheric Research (NCAR) Master Mechanism photochemical box model indicates a more than 100% enhancement in NO2 photolysis rates during the fireworks episode, which leads to a 100% increase in the surface ozone production. Observations as well as model simulations indicate that the enhanced photochemical ozone production from NO2 photolysis is possibly the main driver of ozone production during the Vishu at this site. The air quality index (AQI) revealed the deterioration of air quality at the observational site during the period of Vishu