scholarly journals Migration and Pollution Control of Chlorinated Hydrocarbons in Groundwater System of Eastern Jinan

2021 ◽  
Author(s):  
Zhang shuiaji ◽  
Du Wenfeng ◽  
Liu Zhengwen ◽  
Gu Xiaoyu
Keyword(s):  
Carbon Tetrachloride ◽  
Pollution Control ◽  
Treatment Time ◽  
Transport Model ◽  
Simulation Software ◽  
Pollutant Concentration ◽  
Control Field ◽  
Injection Wells ◽  
Groundwater System ◽  
Chlorinated Hydrocarbon

The groundwater system is polluted by chlorinated hydrocarbon pollution in eastern Jinan, Shandong province, China, exceeding the limit of pollutants concentration in class Ⅲ of Groundwater Quality Standards (GQS, GB/T 14848-2017). In order to improve the current situation of chlorinated hydrocarbon pollutants in groundwater system of eastern Jinan, the optimization study of the pollution control is carried out. In this paper, the pollutant of carbon tetrachloride in groundwater system is taken as the main research object. By using GMS numerical simulation software to establish the solute transport model of carbon tetrachloride. The simulation results illuminate that with the passage of time, the concentration of carbon tetrachloride decreases, but the acreage of pollution plume in groundwater still has little change, and it is hard to reach the limit standard of 2.0μg/L in class Ⅲ of GQS within a short time. Sequentially, on the basis of simulation model, the optimization of pumping and injection wells is conducted in the pollution control field of research region. The results turn out that the layout of 8 pumping and 5 injection wells has the best control effect of carbon tetrachloride in groundwater system, the pollutant concentration reached the limit standard of 2.0μg/L in only 1187d, and the acreage of pollution plume in control field reduced from 21.80km2 to 12.21km2. In summary, through the optimal pollution control scheme of carbon tetrachloride, the time for pollutant concentration to reach 2.0μg/L has been reduced, and the acreage of pollution plume has been effectively controlled. This work further investigates the promoting effect of injection wells on hydraulic control of groundwater pollution, which can accelerate the circulation of the groundwater system and save the treatment time, providing a relatively practical way for the prevention and control of chlorinated hydrocarbon pollutants.

scholarly journals Calibration of a transient transport model to tritium data in streams and simulation of groundwater ages in the western Lake Taupo catchment, New Zealand

2013 ◽  
Vol 17 (3) ◽  
pp. 1217-1227 ◽  
Author(s):  
M. A. Gusyev ◽  
M. Toews ◽  
U. Morgenstern ◽  
M. Stewart ◽  
P. White ◽  
...  
Keyword(s):  
New Zealand ◽  
Transport Model ◽  
Groundwater Age ◽  
Uniform Grid ◽  
Groundwater System ◽  
Small Surface ◽  
Streams And Rivers ◽  
Groundwater Levels ◽  
Transient Transport ◽  
Western Lake

Abstract. Here we present a general approach of calibrating transient transport models to tritium concentrations in river waters developed for the MT3DMS/MODFLOW model of the western Lake Taupo catchment, New Zealand. Tritium has a known pulse-shaped input to groundwater systems due to the bomb tritium in the early 1960s and, with its radioactive half-life of 12.32 yr, allows for the determination of the groundwater age. In the transport model, the tritium input (measured in rainfall) passes through the groundwater system, and the simulated tritium concentrations are matched to the measured tritium concentrations in the river and stream outlets for the Waihaha, Whanganui, Whareroa, Kuratau and Omori catchments from 2000–2007. For the Kuratau River, tritium was also measured between 1960 and 1970, which allowed us to fine-tune the transport model for the simulated bomb-peak tritium concentrations. In order to incorporate small surface water features in detail, an 80 m uniform grid cell size was selected in the steady-state MODFLOW model for the model area of 1072 km2. The groundwater flow model was first calibrated to groundwater levels and stream baseflow observations. Then, the transient tritium transport MT3DMS model was matched to the measured tritium concentrations in streams and rivers, which are the natural discharge of the groundwater system. The tritium concentrations in the rivers and streams correspond to the residence time of the water in the groundwater system (groundwater age) and mixing of water with different age. The transport model output showed a good agreement with the measured tritium values. Finally, the tritium-calibrated MT3DMS model is applied to simulate groundwater ages, which are used to obtain groundwater age distributions with mean residence times (MRTs) in streams and rivers for the five catchments. The effect of regional and local hydrogeology on the simulated groundwater ages is investigated by demonstrating groundwater ages at five model cross-sections to better understand MRTs simulated with tritium-calibrated MT3DMS and lumped parameter models.

scholarly journals Model sensitivity studies of the decrease in atmospheric carbon tetrachloride

2016 ◽  
Vol 16 (24) ◽  
pp. 15741-15754 ◽  
Author(s):  
Martyn P. Chipperfield ◽  
Qing Liang ◽  
Matthew Rigby ◽  
Ryan Hossaini ◽  
Stephen A. Montzka ◽  
...  
Keyword(s):  
Carbon Tetrachloride ◽  
Transport Model ◽  
Three Dimensional ◽  
Montreal Protocol ◽  
Chemical Transport Model ◽  
Uncertainty Range ◽  
The Past ◽  
Systematic Biases ◽  
Lifetime Uncertainty ◽  
The Impact

Abstract. Carbon tetrachloride (CCl4) is an ozone-depleting substance, which is controlled by the Montreal Protocol and for which the atmospheric abundance is decreasing. However, the current observed rate of this decrease is known to be slower than expected based on reported CCl4 emissions and its estimated overall atmospheric lifetime. Here we use a three-dimensional (3-D) chemical transport model to investigate the impact on its predicted decay of uncertainties in the rates at which CCl4 is removed from the atmosphere by photolysis, by ocean uptake and by degradation in soils. The largest sink is atmospheric photolysis (74 % of total), but a reported 10 % uncertainty in its combined photolysis cross section and quantum yield has only a modest impact on the modelled rate of CCl4 decay. This is partly due to the limiting effect of the rate of transport of CCl4 from the main tropospheric reservoir to the stratosphere, where photolytic loss occurs. The model suggests large interannual variability in the magnitude of this stratospheric photolysis sink caused by variations in transport. The impact of uncertainty in the minor soil sink (9 % of total) is also relatively small. In contrast, the model shows that uncertainty in ocean loss (17 % of total) has the largest impact on modelled CCl4 decay due to its sizeable contribution to CCl4 loss and large lifetime uncertainty range (147 to 241 years). With an assumed CCl4 emission rate of 39 Gg year−1, the reference simulation with the best estimate of loss processes still underestimates the observed CCl4 (overestimates the decay) over the past 2 decades but to a smaller extent than previous studies. Changes to the rate of CCl4 loss processes, in line with known uncertainties, could bring the model into agreement with in situ surface and remote-sensing measurements, as could an increase in emissions to around 47 Gg year−1. Further progress in constraining the CCl4 budget is partly limited by systematic biases between observational datasets. For example, surface observations from the National Oceanic and Atmospheric Administration (NOAA) network are larger than from the Advanced Global Atmospheric Gases Experiment (AGAGE) network but have shown a steeper decreasing trend over the past 2 decades. These differences imply a difference in emissions which is significant relative to uncertainties in the magnitudes of the CCl4 sinks.

Modelling of the Transport of Chlorinated Hydrocarbon Solvents in Groundwater: A Case Study

1985 ◽  
Vol 17 (9) ◽  
pp. 13-21 ◽  
Author(s):  
W K. H. Kinzelbach
Keyword(s):  
Transport Model ◽  
Model Parameters ◽  
Dispersive Transport ◽  
Transport Models ◽  
Chlorinated Hydrocarbon ◽  
First Order ◽  
Hydrocarbon Solvents ◽  
Simplifying Assumptions ◽  
Environmental Engineer

At present chlorinated hydrocarbon solvents rank among the major pollutants found in groundwater. In the interpretation of field data and the planning of decontamination measures numerical transport models may be a valuable tool of the environmental engineer. The applicability of one such model is tested on a case of groundwater pollution by 1,1,1,-trichloroethane. The model is composed of a horizontally 2-D flow model and a 3-D ‘random-walk' transport model. It takes into account convective and dispersive transport as well as linear adsorption and a first order decay reaction. Under certain simplifying assumptions the model allows an adequate reproduction of observed concentrations. Due to uncertainty in data and limited comparabili ty of simulated and measured concentrations the model parameters can only be estimated within bounds. The decay rate of 1,1,1-trichloroethane is estimated to lie between 0 and 0.0005 l/d.

Design Analysis of a-Si/c-Si HIT Solar Cells

2010 ◽  
Vol 74 ◽  
pp. 131-136 ◽  
Author(s):  
Muhammad Nawaz
Keyword(s):  
Solar Cells ◽  
Computer Aided Design ◽  
Defect Density ◽  
Transport Model ◽  
Design Analysis ◽  
Simulation Software ◽  
Design Tool ◽  
Physical Parameters ◽  
Photogenerated Carrier ◽  
Solar Cell Performance

A theoretical design analysis using numerical two dimensional computer aided design tool (i.e., TCAD) is presented for a-Si/c-Si based heterojunction (HJ) solar cells. A set of optical beam propagation models, complex refractive index models and defect models for a-Si material implemented (in-built) in the simulation software are first evaluated for single (SHJ) and double heterojunction (DHJ) devices. Assessment is further carried out by varying physical parameters of the layer structures such as doping, thickness of the c-Si and a-Si layers, defect density in the a-Si layer and bandgap discontinuity parameter. With varying bandgap discontinuity and using standard transport model in numerical device simulation, HJ solar cell performance is undervalued (η = 19.5%). This is the result of poor photogenerated carrier collection due to the presence of heterojunction at the respective n and p-contacts of the device. Implementing thermionic field emission tunneling model at the heterojunction, we obtained improved performance (η = 24 %) over large range of bandgap discontinuities. Keeping improved efficiency of HJ cell, implementing a step graded a-Si layer, further helps to widen the range of bandgap discontinuity parameter.

scholarly journals Fabricating rutile nanopins on an anatase hollow sphere structure with enhanced photoactivity performance

RSC Advances ◽  
2017 ◽  
Vol 7 (89) ◽  
pp. 56648-56654 ◽  
Author(s):  
Sheng-Cai Zhu ◽  
Ling Fu
Keyword(s):  
Renewable Energy ◽  
Hollow Sphere ◽  
Pollution Control ◽  
Promising Material ◽  
Control Field

TiO2 is a promising material for the renewable energy and pollution control field.

scholarly journals Coupled flow-geomechanics studies on the role of hydrofracturing and secondary fracturing in CO2-enhanced coalbed methane

2021 ◽  
pp. 014459872098527
Author(s):  
Chaobin Guo ◽  
Quanlin Feng ◽  
Tianran Ma ◽  
Siqi Wang ◽  
Rui Zhou ◽  
...  
Keyword(s):  
Coalbed Methane ◽  
Production Efficiency ◽  
Gas Production ◽  
Simulation Software ◽  
Fracture Density ◽  
Coupled Flow ◽  
Injection Wells ◽  
Mechanical Coupling ◽  
Fracturing Process ◽  
Enhanced Coalbed Methane

CO2-enhanced coalbed methane (CO2-ECBM) can improve coalbed methane production efficiency and simultaneously alleviate greenhouse gas emissions. In this paper, we integrated TOUGH2 and FLAC3D numerical simulation software to conduct hydro-mechanical coupling analysis for effects of hydrofracturing and secondary fracturing in CO2-ECBM. The simulation results show that the hydrofracturing and secondary fracturing treatments significantly increase the coal seam interconnectivity, enhancing overall injection and production. The reduction of the pore pressure near injection wells can effectively reduce the damage of gas injection well. Moreover, secondary fracturing can even increase cumulative gas production up to 32.5%. In addition to rising fracture density, increasing the fracture length is also considered an efficacious procedure for enhancing permeability in the secondary fracturing process.

Prediction of Pollutant Concentration for Air Pollution Control

1977 ◽  
Vol 10 (7) ◽  
pp. 645-653
Author(s):  
Y. Oshima ◽  
N. Mohri ◽  
H. Nose ◽  
K. Nakagawa
Keyword(s):  
Air Pollution ◽  
Pollution Control ◽  
Pollutant Concentration ◽  
Air Pollution Control
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