Persistent Organic Pollutants (POPs) including organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) are important group of chemicals that may be released into the environment accidently or as a result of intentional anthropogenic activities and can cause various ecotoxicological and human health hazards. Their long range atmospheric transport potential could lead them to reach high altitude cold regions where they become deposited and trapped on surface media. Intriguingly, another pollutant, black carbon (BC) shows strong association with these trace chemicals and could sturdily affect the environmental distribution of these contaminants. The Himalaya is globally highest mountain range of 2400 km2 with an altitude of < 100-8844 masl that separates the Indian Subcontinent from the Tibetan Plateau (TP). Of particular importance is its proximity to industrialized regions of China, India and Pakistan. Due to influence of wind patterns (monsoon and westerlies) and anthropogenic activities, lower stretch of the Himalaya is at direct exposure to POPs. Current study was designed to monitor soil, sediment, water and atmospheric concentrations of long lived OCPs and PCBs in the Lesser Himalayan Region (LHR) of Pakistan. Polyurethane foam passive air samplers (PUF-PAS) were deployed for air samples, while soil, sediment and water samples were collected according to the defined protocols. Further, total organic carbon (TOC) and BC were analyzed in soils and sediments. Chemo-Thermal Oxidation (CTO-375) method was used for BC analysis, whereas OCs were analyzed by Gas Chromatography-Mass Spectrometry (GC-MS) system. Soil BC and TOC ranged between 0.16– 1.77 and 6.8−41.3 mg g-1, while sedimentary BC and TOC varied between 0.3−43.5 mg g−1 and 1.7−65.4 mg g−1, respectively. OCPs in soil, air, sediment and water samples from the LHR ranged between 0.69−5.77 ng g−1, 3.77−247 pg m−3, 0.59−3.64 ng g−1 and 0.07−41.4 ng L−1, respectively. PCBs concentrations ranged between 0.12–2.55 ng g-1, 8.49–458 pg m–3, 0.01−1.31 ng g−1 and 0.671−84.5 ng L−1, respectively. Spatially, Zone C (altitude range of 737−975 masl) have shown higher OCs levels in case of all matrices. Though, air mass trajectories over the LHR indicated long range transport as atmospheric source input, which was further explained by Clausius– Clapeyron plots between ln P and inverse of temperature (1000/T; K) where all OCPs and most of the PCBs have shown insignificant relationship (r2 = 5E-06–0.41; p-value = 0.06–0.99). However, local source emissions and valley transport may also implicate based on spatial distribution and altitudinal patterns. The results of linear regression analysis revealed potential input of BC in soil distribution of OCs concentrations in the region. Additionally, soil-air partitioning of OCs was assessed using octanol-air partition (KOA) and black carbon-air partition (KBC) based models. Regression results indicated combined influence of both organic matter (r2 = 0.3−0.85) and black carbon (r2 = 0.31−0.86) via absorption and adsorption, respectively in soil-air partitioning of OCs in the LHR. The relationship of sedimentary BC and TOC with OCPs and PCBs was evaluated using Principal Component Analysis (PCA) and Pearson Correlation Analysis that indicated higher sorptive influence of BC over TOC in distribution status of OCs in the LHR. Sedimentwater partitioning of OCPs and PCBs were deduced using field data by employing one carbon (fOCKOC) and two carbon Freundlich model (fOCKOC + fBCKBC-WCWnF−1). Results suggested improved measured vs predicted model concentrations when BC was induced in the model and suggested adsorption to be the dominant mechanism in phase partitioning of OCs in the LHR. The results of this study sheds light on the environmental concentrations of OCs in lower stretch of the Himalaya and help in better understanding of the processes involved in fate and transport of organic pollutants in the Himalayan region. Further investigations are required to understand the role of carbon fractions in fate and transport of other groups of organic pollutants at higher altitudes of the Himalayan region.
History comes to us from various agencies not just academics in schools and colleges; but diverse inputs to all those who haven’t studied history, like popular history, through cinema, poetry, folklore, myths, theatre; history has several modes of percolation to society. Also, a kind of history is propagated in an organised manner as is done by organisations as RSS which is a practical approach to history as differentiated from an academic approach to history; the former is more political than the latter though both come with an aspect of politics. History thus has much wider reach than what is taught in schools or colleges.
This experimental and simulation study investigates the potential of using a solar assisted hybrid desiccant cooling system (SHDCS) for air conditioning applications for Pakistan. A review of literature reveals that compared to the conventional vapour compression cycle this cycle could offer saving in overall primary energy. Since the cycle is based on supply of conditioned ventilation air it has significantly lower environmental impact. A gas fired hybrid desiccant cooling test rig has been installed at the Energy Conservation Laboratory NED to study the performance of various components. These experiments enabled understanding of the system and helped develop effect of individual components on the system performance. Important parameters of system components established from the experiments were used as input to the TRNSYS simulation model. The simulation studies have been based on a well established transient energy software TRNSYS. Specific to this work a mathematical model of Modified Cooler was prepared from basic principles and added as module to TRNSYS. Addition of this component resulted in an increases of the COPp-s by a factor of 1.065 for the weather of Lahore. Besides COP; all system parameters showed an improvement due to the addition of this component. Six case studies based on SHDCS have been performed for Karachi and Lahore. The results so obtained established that the advantage of using SHDCS depends on the climatic conditions. SHDCS offers considerable promise for Lahore i. e., it shows that of the seven month summer cooling season the desiccant cooling system alone suffices for three month – April, May and October. However for Karachi summer, characterized by high humidity, SHDCS does not provide acceptable temperature and humidity conditions without auxiliary air conditioning. The source of thermal energy needed for regeneration plays an important part in the overall success of the desiccant cooling scheme. To reduce the use of conventional energy, in this case natural gas, a solar collector has been included in the study. Micro analysis of the flow and heat transfer phenomenon taking place inside inclined solar air collector was studied using CFD software, which demonstrated that low heat transfer between air and absorber can be improved by using staggered fins. It was also shown that the fin configuration coupled with low flow velocity helped increase heat transfer in the absorber duct by increasing heat transfer area, mixing and residence time. Energy, economic and environmental impact of the solar collectors was also studied and payback periods for energy, Carbon emission and monetary investment have been found to be 1.5 years, 1 year and 14 years respectively. The success of the desiccant cooling system is strongly associated with cost of the thermal energy. Combined heat and power systems offer an opportunity of providing this energy at no additional cost. The latter study has been suggested to be taken up as future work.