Volume 23 - 2021

Beijing-Tianjin-Hebei and the surrounding area (BTHS) experiences the most serious PM2.5 pollution in China. To investigate PM2.5 pollution characteristics in regional heavy air pollution, forty-three events in BTHS during 2015–2018 were selected in this study. These regional events generally lasted five days and covered nineteen cities, with an average PM2.5 concentration of 204 μg·m-3 and a maximum daily average concentration of 358 μg·m-3. The pollution events occurred mainly during October to March of the following year, which is the heating season in this region. The occurrence of pollution events and the PM2.5 concentration displayed a decreasing trend during 2015–2018. Of the forty-three events, thirteen started in Baoding city, and the peak PM2.5 concentration was recorded in Baoding city eleven times, indicating that it was the most polluted city in BTHS. A comprehensive classification method determined that southwest channel pollution was the main type of pollution event in BTHS. It occurred nine, seven, four, and eight times in 2015–2018, accounting for 56.3%, 53.8% 80.0%, and 88.9% of all pollution events, respectively. A typical regional heavy PM2.5 pollution event occurred in March 2016. The analysis revealed that it was initiated by pollutant transport from regions south of BTHS. Local pollutant emissions and regional pollutants accumulated, and secondary pollutant formation occurred in association with weak winds and a high relative humidity, which maintained the heavy pollution levels. Relative humidity had the most significant influence on the two most important stages of a heavy PM2.5 pollution event, which were the initial and high concentration stages, respectively.

The present study was carried out to understand the hydrological behavior of natural springs/streams in Semalta watershed, Kalsi block, Dehradun. The surface catchment areas of springs/streams were delineated using Survey of India Toposheet (1:50,000 scale) whereas drainage, slope, and land use maps of the watershed were prepared using open source ILWIS GIS software. The drainage map of the watershed indicated the ephemeral, intermittent and perennial nature of streams and the slope map of the watershed indicated that the majority of the area falls under scrubland. The discharge trend at different gauging sites from October 2015 to March 2016 indicated that the flow rate of the stream gradually decreased from post-monsoon to pre-monsoon period. The geohydrological and geomorphological study indicated that most of the springs/streamflow were controlled by fracture/joints with slate/phyllite/limestone/quartzite as country rock. The pH of most of the stream water was mildly alkaline (7.85-8.82) whereas EC was non-saline (0.087-0.425) and temperature varied from 14-23°C. Results on major ions indicated that a higher percentage of NH4+ together with NO3- was possible because of anthropogenic influence. In addition, the higher percentage of SO4- and F- was due to lithological pyrite whereas the higher percentage of HCO3- was due to pyrite weathering of slate. Results on the isotopic variation of δ18O showed that samples were collected with a total height difference of 700 m with a variation of -0.21‰ per 100 m for stream water and -0.5‰ for rainwater. On higher altitudes mainly narrow subsurface pathways are found and therefore only small size of structures are required for recharging and vice versa for the recharge of springs located in lower altitudes. The present study discusses various sampling techniques to ascertain the altitude of recharge of springs which would form the basis for taking appropriate on field activities for spring/stream rejuvenation.

Silver nanoparticles (GSNPs) were synthesized from extracellular metabolites of endophytic isolates of Fusarium verticillioides (KT587649) to evaluate their efficiency as new biosorbent agents for the exclusion of cadmium Cd (II) from aquatic systems. The GSNPs were characterized through X-ray diffraction (XRD) and transmission electron microscopy (TEM). Results show that the most efficient Cd (II) removal rate by both biosorbents was at pH 7.0. The optimal contact times were 30 and 40 min by F. verticillioides and GSNPs, respectively. Langmuir adsorption isotherms revealed that the highest calculated adsorption capacities of F. verticillioides and GSNPs for Cd (II) were 185±0.25 mg/g and 176±0.18 mg/g, respectively. The harmonized adsorption isotherms (between the Freundlich isotherm and Langmuir models) indicated a high correlation coefficient (r2 > 0.97). The kinetics of the biosorption process fitted well with the pseudo-second-order kinetic model. This study has thus confirmed the biosorbent capacity of F. verticillioides and its GSNPs for the exclusion of Cd (II) from any contaminated aquatic system and shows it is an eco-friendly method with great feasibility and potential to convey economic and other benefits in wastewater treatment technologies

Direct discharge of black water (BW) without treatment to the natural environment causes problems for the environment. The present research aimed to examine the impact of direct disposal of BW on the municipal wastewater (MWW) and surrounded soil characteristics in the BW disposal site in Erbil City- Kurdistan Region (KR), Iraq. To check the effect of BW on the boarded MWW and the soil; BW, MWW, BW mixed with MWW (BWMWW), polluted soil, and clean soil samples were collected and analyzed. Samples of BW, MWW, and BWMWW were tested for 32 physical-chemical and biological quality parameters such as pH, turbidity, solids, color, dissolved oxygen, five day biochemical oxygen demand (BOD5), chemical oxygen demand (COD), ammonia, oxidation-reduction potential (ORP), sulphate, oil and grease, phosphate, Most probable number (M.P.N.) of coliform, Thermo tolerant, M.P.N. E.Coli …etc. In contrast, soil samples were tested for 37 parameters, for instance pH, ORP, organic matter (OM), sulfite, Titanium, Vanadium, Chromium, Manganese, Iron, Cobalt, Nickel, Copper, Zinc, Gallium, Arsenic, Rubidium, Strontium, Yttrium, Zirconium, Molybdenum, Silver, Cadmium, Mercury, Lead, Thorium and Uranium. Results revealed that the direct disposal of BW without treatment commonly affected on the MWW and the surrounded soil characteristics. Potential treatment processes and solutions for BW disposal were presented.