Evaluation of the saturated–unsaturated groundwater conditions of a thickened tailings deposit

The method of thickened tailings disposal has been in use at an active copper–zinc mine near Timmins, Ontario, for approximately 25 years. The thickened tailings deposit that has been formed was investigated. Field and laboratory tests were conducted to determine particle-size distribution at various horizontal locations, in situ values of hydraulic conductivity, moisture-retention characteristics, groundwater levels, and in situ water contents. The results of the investigation show that the thickened tailings deposit is relatively homogeneous. Shallow groundwater levels were also observed to follow the gently sloping topography of the tailings surface. Upward-seepage analyses were conducted for various steady-state evaporative fluxes. The analyses showed the tailings tend to maintain saturated conditions for the highest potential rate of evaporation observed. The ability of the tailings to maintain saturation is attributed to the shallow groundwater levels and the high air-entry value of the tailings. The tendency to saturated conditions at the tailings surface is a positive result. Saturated conditions in the tailings minimize the diffusion of atmospheric oxygen into the tailings. This aids in the prevention of acid generation in these tailings, which have the potential to oxidize and produce acid drainage. Key words : tailings, saturation, evaporation, acid generation.

Download Full-text

Numerical simulations to investigate moisture-retention characteristics in the design of oxygen-limiting covers for reactive mine tailings

Canadian Geotechnical Journal ◽

10.1139/t91-054 ◽

1991 ◽

Vol 28 (3) ◽

pp. 446-451 ◽

Cited By ~ 29

Author(s):

Festus F. Akindunni ◽

R. W. Gillham ◽

R. V. Nicholson

Keyword(s):

Numerical Simulations ◽

Mine Tailings ◽

Atmospheric Oxygen ◽

Pressure Head ◽

Moisture Retention ◽

Residual Saturation ◽

Acid Generation ◽

Water Influx ◽

Protective Cover ◽

Retention Characteristics

Acid generation in reactive mine tailings is an oxidation process that is dependent on availability of molecular oxygen. As a consequence of the diffusion coefficient of oxygen being several orders of magnitude higher in air than in water, influx of atmospheric oxygen into a material at depth can theoretically be minimized by maintaining a protective cover layer at high moisture content. Such oxygen-limiting covers are generally of finer texture than the material being protected. A numerical model was used to investigate the importance of moisture-retention characteristics in the transient drainage of such two-layer systems. The results show that the effectiveness of a material as a moisture-retaining cover is dependent on the magnitude of its air-entry value. The thickness of the cover maintained at full saturation after prolonged drainage also depends on the pressure head at which the underlying material approaches residual saturation. Key words: geologic covers, tailings, numerical simulations, air-entry value, residual saturation, textural layering.

Download Full-text

Localization of copper-zinc superoxide dismutase mRNA in human hippocampus by in situ hybridization

Neuroscience Letters ◽

10.1016/0304-3940(89)90008-6 ◽

1989 ◽

Vol 105 (1-2) ◽

pp. 41-46 ◽

Cited By ~ 22

Author(s):

Irène Ceballos ◽

France Javoy-Agid ◽

Etienne C. Hirsch ◽

Sylvie Dumas ◽

Pierre P. Kamoun ◽

...

Keyword(s):

Superoxide Dismutase ◽

In Situ Hybridization ◽

Copper Zinc Superoxide Dismutase ◽

Zinc Superoxide Dismutase ◽

Human Hippocampus ◽

Copper Zinc

Download Full-text

The measurement of groundwater temperature in shallow piezometers and standpipes

Canadian Geotechnical Journal ◽

10.1139/t05-061 ◽

2005 ◽

Vol 42 (5) ◽

pp. 1377-1390 ◽

Cited By ~ 14

Author(s):

Matthew D Alexander ◽

Kerry TB MacQuarrie

Keyword(s):

Finite Element ◽

Statistical Analysis ◽

Transport Model ◽

Shallow Groundwater ◽

Subsurface Temperature ◽

Groundwater Temperature ◽

Monitoring Well ◽

Laboratory Results ◽

The Impact

Accurate measurements of in situ groundwater temperature are important in many groundwater investigations. Temperature is often measured in the subsurface using an access tube in the form of a piezometer or monitoring well. The impact of standpipe materials on the conduction of heat into the subsurface has not previously been examined. This paper reports on the results of a laboratory experiment and a field experiment designed to determine if different standpipe materials or monitoring instrument configurations preferentially conduct heat into the shallow sub surface. Simulations with a numerical model were also conducted for comparison to the laboratory results. Statistical analysis of the laboratory results demonstrates that common standpipe materials, such as steel and polyvinylchloride (PVC), do not affect temperature in the subsurface. Simulations with a finite element flow and heat transport model also confirm that the presence of access tube materials does not affect shallow groundwater temperature measurements. Field results show that different instrument configurations, such as piezometers and water and air filled and sealed well points, do not affect subsurface temperature measurements.Key words: groundwater temperature, temperature measurement, conduction, piezometers, piezometer standpipes, thermal modelling.

Download Full-text

Shallow groundwater in sub-Saharan Africa: neglected opportunity for sustainable intensification of small-scale agriculture?

10.5194/hess-2015-549 ◽

2016 ◽

Cited By ~ 3

Author(s):

John Gowing ◽

Geoff Parkin ◽

Nathan Forsythe ◽

David Walker ◽

Alemseged Tamiru Haile ◽

...

Keyword(s):

Groundwater Resources ◽

Climatic Variability ◽

Shallow Groundwater ◽

Sustainable Intensification ◽

Sub Saharan Africa ◽

Small Scale ◽

Groundwater Levels ◽

Sub Saharan ◽

Small Scale Irrigation

Abstract. There is a need for an evidence-based approach to identify how best to support development of groundwater for small scale irrigation in sub-Saharan Africa (SSA). We argue that it is important to focus this effort on shallow groundwater resources which are most likely to be used by poor rural communities in SSA. However, it is important to consider constraints, since shallow groundwater resources are likely to be vulnerable to over-exploitation and climatic variability. We examine here the opportunities and constraints and draw upon evidence from Ethiopia. We present a methodology for assessing and interpreting available shallow groundwater resources and argue that participatory monitoring of local water resources is desirable and feasible. We consider possib le models for developing distributed small-scale irrigation and assess its technical feasibility. Because of power limits on water lifting and also because of available technology for well construction, groundwater at depths of 50 m or 60 m cannot be regarded as easily accessible for small-scale irrigation. We therefore adopt a working definition of shallow groundwater as < 20 m depth. This detailed case study in the Dangila woreda in Ethiopia explores the feasibility of exploiting shallow groundwater for small-scale irrigation over a range of rainfall conditions. Variability of rainfall over the study period (9 % to 96 % probability of non-exceedance) does not translate into equivalent variability in groundwater levels and river baseflow. Groundwater levels, monitored by local communities, persist into the dry season to at least the end of December in most shallow wells, indicating that groundwater is available for irrigation use after the cessation of the wet season. Arguments historically put forward against the promotion of groundwater use for agriculture in SSA on the basis that aquifers are unproductive and irrigation will have unacceptable impacts on wetlands and other groundwater-dependent ecosystems appear exaggerated. It would be unwise to generalise from this case study to the whole of SSA, but useful insights into the wider issues are revealed by the case study approach. We believe there is a case for arguing that shallow groundwater in sub-Saharan Africa represents a neglected opportunity for sustainable intensification of small-scale agriculture.

Download Full-text

In Situ Hypochlorous Acid Generation for Treatment of Tannery Wastewaters

Journal of Environmental Engineering ◽

10.1061/(asce)0733-9372(1998)124:9(887) ◽

1998 ◽

Vol 124 (9) ◽

pp. 887-891 ◽

Cited By ~ 12

Author(s):

K. Vijayaraghavan ◽

T. K. Ramanujam ◽

N. Balasubramanian

Keyword(s):

Hypochlorous Acid ◽

Acid Generation

Download Full-text

Groundwater recharge processes in an Asian mega-delta: hydrometric evidence from Bangladesh

Hydrogeology Journal ◽

10.1007/s10040-020-02238-3 ◽

2020 ◽

Vol 28 (8) ◽

pp. 2917-2932

Author(s):

Sara Nowreen ◽

R. G. Taylor ◽

M. Shamsudduha ◽

M. Salehin ◽

A. Zahid ◽

...

Keyword(s):

Groundwater Recharge ◽

Conceptual Models ◽

Shallow Groundwater ◽

Depositional Environments ◽

Series Data ◽

Groundwater Depletion ◽

Bengal Basin ◽

River Channels ◽

Groundwater Levels ◽

Pleistocene Aquifer

AbstractGroundwater is used intensively in Asian mega-deltas yet the processes by which groundwater is replenished in these deltaic systems remain inadequately understood. Drawing insight from hourly monitoring of groundwater levels and rainfall in two contrasting settings, comprising permeable surficial deposits of Holocene age and Plio-Pleistocene terrace deposits, together with longer-term, lower-frequency records of groundwater levels, river stage, and rainfall from the Bengal Basin, conceptual models of recharge processes in these two depositional environments are developed. The representivity of these conceptual models across the Bengal Basin in Bangladesh is explored by way of statistical cluster analysis of groundwater-level time series data. Observational records reveal that both diffuse and focused recharge processes occur in Holocene deposits, whereas recharge in Plio-Pleistocene deposits is dominated by indirect leakage from river channels where incision has enabled a direct hydraulic connection between river channels and the Plio-Pleistocene aquifer underlying surficial clays. Seasonal cycles of recharge and discharge including the onset of dry-season groundwater-fed irrigation are well characterised by compiled observational records. Groundwater depletion, evident from declining groundwater levels with a diminished seasonality, is pronounced in Plio-Pleistocene environments where direct recharge is inhibited by the surficial clays. In contrast, intensive shallow groundwater abstraction in Holocene environments can enhance direct and indirect recharge via a more permeable surface geology. The vital contributions of indirect recharge of shallow groundwater identified in both depositional settings in the Bengal Basin highlight the critical limitation of using models that exclude this process in the estimation of groundwater recharge in Asian mega-deltas.

Download Full-text

Spatial variability of shallow groundwater level in the Northern Kathmandu Valley

Journal of Nepal Geological Society ◽

10.3126/jngs.v55i1.22788 ◽

2018 ◽

Vol 55 (1) ◽

pp. 45-54

Author(s):

Manish Shrestha ◽

Naresh Kazi Tamrakar

Keyword(s):

Groundwater Level ◽

Shallow Groundwater ◽

Soil Surface ◽

Northern Region ◽

Dry Season ◽

Kathmandu Valley ◽

Wet Season ◽

Geological Material ◽

Groundwater Levels ◽

Shallow Groundwater Level

Groundwater is the water which is present in pore spaces and in the fractures of the geological materials beneath earth surface. Water is incompressible substance and presence of small amount of water in geological material modifies the behavior of geological material under stresses. Determination of engineering behavior of the geological material is almost impossible skipping the role of water. The objective of this study was to map and evaluate shallow groundwater level of the northern Kathmandu Valley covering main rivers such as the Bagmati River, Bishnumati River, Dhobi Khola and the Manahara Khola. These rivers flow from the North to the South across the sand rich sediment zone. Static groundwater levels of 239 wells were measured from different locations of the study area in April/March 2017 (Dry Season) and in August 2017 (Wet Season). Shallow groundwater level was measured from soil surface to water level using well water depth logger (Qin and Li, 1998). The result showed that groundwater level ranged from 0.6 m to 12.5 m in dry season and 0.1 m to 13 m in wet season. The groundwater level increased by average of 34.68% (n = 235) as compared to that in dry season. Increase in the groundwater level suggests recharge of groundwater in wet season of the study area. The flow pattern of groundwater levels from the study shows flow of shallow groundwater towards the major rivers of that particular river watershed. As a consequence, seepage flow and piping erosion is likely along the riverbank slopes. Increase in recharge of groundwater during wet season exhibits that the northern region of the Kathmandu Valley is potential for groundwater recharge and can be used to manage water for the dry period.

Download Full-text

In situ observation of atmospheric oxygen and carbon dioxide in the North Pacific using a cargo ship

Atmospheric Chemistry and Physics ◽

10.5194/acp-18-9283-2018 ◽

2018 ◽

Vol 18 (13) ◽

pp. 9283-9295 ◽

Cited By ~ 1

Author(s):

Yu Hoshina ◽

Yasunori Tohjima ◽

Keiichi Katsumata ◽

Toshinobu Machida ◽

Shin-ichiro Nakaoka

Keyword(s):

Carbon Dioxide ◽

Mole Fraction ◽

North Pacific ◽

Atmospheric Oxygen ◽

The United States ◽

In Situ Observation ◽

Airflow Rate ◽

The North ◽

The North Pacific

Abstract. Atmospheric oxygen (O2) and carbon dioxide (CO2) variations in the North Pacific were measured aboard a cargo ship, the New Century 2 (NC2), while it cruised between Japan and the United States between December 2015 and November 2016. A fuel cell analyzer and a nondispersive infrared analyzer were used for the measurement of O2 and CO2, respectively. To achieve parts-per-million precision for the O2 measurements, we precisely controlled the flow rates of the sample and reference air introduced into the analyzers and the outlet pressure. A relatively low airflow rate (10 cm3 min−1) was adopted to reduce the consumption rate of the reference gases. In the laboratory, the system achieved measurement precisions of 3.8 per meg for δ(O2 ∕ N2), which is commonly used to express atmospheric O2 variation, and 0.1 ppm for the CO2 mole fraction. After the in situ observation started aboard NC2, we found that the ship's motion caused false wavy variations in the O2 signal with an amplitude of more than several tens of ppm and a period of about 20 s. Although we have not resolved the problem at this stage, hourly averaging considerably suppressed the variation associated with ship motion. Comparison between the in situ observation and flask sampling of air samples aboard NC2 showed that the averaged differences (in situ–flask) and the standard deviations (±1σ) are −2.8 ± 9.4 per meg for δ(O2 ∕ N2) and −0.02 ± 0.33 ppm for the CO2 mole fraction. We compared 1 year of in situ data for atmospheric potential oxygen (APO; O2 +1.1×CO2) obtained from the broad middle-latitude region (140∘ E–130∘ W, 29∘ N–45∘ N) with previous flask sampling data from the North Pacific. This comparison showed that longitudinal differences in the seasonal amplitude of APO, ranging from 51 to 73 per meg, were smaller than the latitudinal differences.

Download Full-text

Impact of Long-Term Reclaimed Water Irrigation on the Distribution of Potentially Toxic Elements in Soil: An In-Situ Experiment Study in the North China Plain

International Journal of Environmental Research and Public Health ◽

10.3390/ijerph16040649 ◽

2019 ◽

Vol 16 (4) ◽

pp. 649 ◽

Cited By ~ 2

Author(s):

Xiaomin Gu ◽

Yong Xiao ◽

Shiyang Yin ◽

Honglu Liu ◽

Baohui Men ◽

...

Keyword(s):

Toxic Elements ◽

Reclaimed Water ◽

Soil Layer ◽

Shallow Groundwater ◽

Potentially Toxic Elements ◽

In Situ Experiment ◽

The North ◽

Reclaimed Water Irrigation

The widespread use of reclaimed water has alleviated the water resource crisis worldwide, but long-term use of reclaimed water for irrigation, especially in agricultural countries, might threaten the soil environment and further affect groundwater quality. An in-situ experiment had been carried out in the North China Plain, which aimed to reveal the impact of long-term reclaimed water irrigation on soil properties and distribution of potentially toxic elements (As, Cd, Cr, Hg, Zn and Pb) in the soil profile as well as shallow groundwater. Four land plots were irrigated with different quantity of reclaimed water to represent 0, 13, 22 and 35 years’ irrigation duration. Pollution Load Index (PLI) values of each soil layer were calculated to further assess the pollution status of irrigated soils by potentially toxic elements (PTEs). Results showed that long-term reclaimed water irrigation caused appreciable increase of organic matter content, and might improve the soil quality. High soil organic matter concentrations conduced to high adsorption and retention capacity of the soils toward PTEs, which could reduce the risk of PTEs leaching into deep layers or shallow groundwater. Highest levels of Cr, Pb and Zn were observed at 200–240 cm and 460–500 cm horizons in plots. Longer irrigation time (35 years and 22 years) resulted in a decreasing trend of As, Cd, Hg, Pb and Zn in lower part of soil profiles (>540 cm) compared with that with 13-years’ irrigation years. Long-term reclaimed water irrigation still brought about increases in concentrations of some elements in deep soil layer although their content in soils and shallow groundwater was below the national standard. Totally speaking, proper management for reclaimed water irrigation, such as reduction of irrigation volume and rate of reclaimed water, was still needed when a very long irrigation period was performed.

Download Full-text