Contaminant mobility as a result of sediment inundation : literature review and laboratory scale pilot study on mining contaminated sediments

This report presents a literature review of soil and sediment inundation methodologies and describes a pilot scale laboratory inundation study. Changing weather conditions, subsequent flooding events, and the increased frequency of such events both in the UK and worldwide is highlighting the need to research the area of contaminant mobility from soils and sediments under inundated conditions. The findings of such investigations impact on a wide variety of sectors, including human and ecological health, agriculture, building, transport, world economy and climate change. Standardised methodologies for the investigation of contaminant mobility resulting from soil/sediment inundation episodes are not available. Most research has been conducted in the agricultural sector for nutrient transport, as part of soil fertility and plant nutrition studies. Only recently has work been undertaken for studying potentially harmful element transport in inundated sediments/soils. A pilot scale laboratory study was undertaken using contaminated bank sediment samples collected from the Rookhope Burn catchment, Northern England, UK, with the aim to examine the extent of contaminant mobilisation from flooded sediments. The catchment has been affected by historical mining and processing of lead and zinc ore and is representative of several catchments affected by the environmental legacy related to mining in the Northern Pennine Orefield. Bank sediment Pb and Zn concentrations were found significantly above both the TEL and PEL sediment quality criteria, posing potentially a significant hazard to aquatic organisms. The source of the Pb and Zn in the sediments is related to the underlying mineralisation, mining activities and mine water discharges in the catchment. Abundances of original sulphide ore and authigenic metal-bearing phases were expected to vary through the catchment. The study design simulated rising flood water, a slow saturation of the sediment in order to induce a slow change in physico-chemical properties, followed by a 3 month (88 day) stagnation period. Natural day-night cycles were simulated by undertaking the study on the bench top during the winter of 2009/2010 (November to February). The chemical changes in the inundation water during the experiment were monitored and the sediment pore water at the end of the inundation period analysed. The inundation water pH remained alkaline to neutral, while redox measurements indicated oxic conditions in the water column throughout the inundation period. The pilot study showed that inundation of river bank sediments from the Rookhope Burn may be a significant pathway for contaminants in the catchment and that mobilisation from the sediments may pose a hazard to environmental receptors in the area, particularly with respect to Pb and Zn contamination. The different degrees and different rates of metal losses to the overlying water column observed during the flooding of the Rookhope Burn bank sediments demonstrated that the significance of metal mobilisation was dictated by the sediment composition. The inundation water composition monitored during the sediment flooding was used to indirectly infer possible processes that control contaminant fluxes from the sediments to the overlying water. Dissolved Pb concentration in the inundation water reflected the original concentration in the solid material and in sediments that had XRD-detectable galena and cerussite the dissolved Pb concentration reached a maximum value of 395 μg l-1. Cerussite, which is commonly formed as coatings on galena during the sulphide weathering, was close or supersaturated in those solutions, suggesting that the lead carbonate mineral phase provided a continuous source of Pb to these solutions. The initial dissolved Zn in the inundation waters was independent of the original concentration in the sediments. Sediments downstream a mine water discharge showed a greater availability of easily mobilised Zn, producing high initial Zn concentration in the inundation water, despite the relatively low Zn concentration in the inundated sediment. The Zn/SO4 and Cd/Zn molar ratios were both consistent with sphalerite mineral oxidation. The final inundation water solutions had the highest Zn concentrations for those sediment samples where sphalerite was detected by XRD. Redox sensitive elements such as Fe and Mn could not unequivocally indicate the presence of reducing conditions within the flooded sediments and the redox measurements were carried out only in the overlying water column (ORP above 200-350 mV). Low organic matter content and sandy texture would not have favoured the rapid formation of an anoxic layer. Yet, only extending the ORP measurements to the submerged sediment would determine the presence of flooding-induced reducing conditions. Reductive dissolution of Mn oxyhydroxides would result in release of Mn into solution, along with other trace metals, such as Pb and Zn. Mn increased in the inundation water throughout most or all the inundation period for some of the studied sediments. Their final pore water composition was significantly enriched in Mn (1300- 6500 μg l-1). Saturation indices indicated both rhodocrosite (MnCO3) and Mn oxides reached saturation. Therefore, it was not possible to preclude either the role of rhodocrosite as solubility controlling solid phase or the reductive dissolution of Mn oxides for accounting the enhanced Mn concentrations in the pore water and overlying water column without a better characterisation of the solid phase and monitoring of the sediment redox conditions. Amendments to the inundation test design have been recommended, which comprise: set-up to allow for the continuous monitoring of pore water dynamics and allow for the collection of pore water at the different times and measurement of pore water pH and Eh; inclusion of a blank test cell, to test the influence of the properties and the volume of the inundation water; inclusion of flow-cell tests to assess the influence of moving or stagnant inundation water; the inclusion of abiotic blanks to identify the role microbes play in the solubilisation of contaminants. complementary characterisation of the solid phase material and metal distribution in the sediment before and after the inundation experiment

Propellant sidefeed-short pulse discharge thruster studies

The technique of feeding a solid propellant into the discharge from the sides of the discharge was evaluated. The thrust/power ratio could be significantly effected by the included angle of V-shaped propellants and by the electrode length. This result implies that when results are compared at the same specific impulse it is possible to obtain higher thrust efficiencies. In particular, it was found that for a given discharge energy the thrust/power ratio correlated with propellant mass. Increasing the integral simultaneously increases both the gas dynamic and electromagnetic thrust. An analytic expression was formulated for ablated mass which comprehensively describes experimental data in terms of geometry and electrical parameters. The correlation of the product impulse x specific impulse with discharge energy was also described. It is suggested that the reliability of dry energy storage capacitors does not equal the reliability of liquid impregnated units when the comparison is made at the same joules/Kg rating

Tracing sources and fate of zinc in a mining-impacted river catchment: insights from flow measurements, synoptic sampling, and zinc isotopes

This paper reports on the comprehensive monitoring of the Rookhope Burn catchment in the Weardale valley, northern Pennines (Uk), which has been subject to lead, zinc, and fluorspar mining for over two centuries. Zinc is the major contaminant in surface waters, exceeding the Environmental Quality standard value for salmonid fish. synoptic flow monitoring and water sampling have been carried out, including both inflow and instream sampling points along the Rookhope Burn, with the purpose of tracing both point and diffuse sources of Zn throughout the catchment. The Zn load profile suggests an important role for Zn-rich groundwater contributions to the stream bed and has also established the existence of Zn sinks. Evidence from hyporheic zone sampling suggests Zn reaction or surface complexation with Mn oxide surfaces forming on stream bed sediments as a potential mechanism responsible for the observed metal attenuation. Current work is focused on testing the potential of Zn isotopes to fingerprint sources and pathways of Zn in the aquatic system. Preliminary results show significant variation in the stream water Zn isotopic signature from the headwaters to the base of the catchment

Poetical Ponders

The fill-in poem is a type of literary amusement popular in the late eighteenth century. Note that the fourth line in each quatrain does not rhyme with the second line, but if you substitute the appropriate word for each parenthesized word or phrase, it will rhyme and scan. Place the answers under each other, and you will have created an acrostic whose first and last letters reading downward generate the name of a famous soccer player

Nautical Creativity

There is a tremendous amount of creativity in the naming of one\u27s boat. Hang around any dock and you will see names of nautical significance (Trafalgar) to family fun (All Smiths). My two favorites, Naughty Naughty (with a rowboat, Just A Little Bit Naughtyon its deck) and Bermuda Schwartz, led to the linguistic activity of creativity naming boats. The rules are simple

Impact of the earthworm Lumbricus terrestris (L.) on As, Cu, Pb and Zn mobility and speciation in contaminated soils

To assess the risks that contaminated soils pose to the environment properly a greater understanding of how soil biota influence the mobility of metal(loid)s in soils is required. Lumbricus terrestris L. were incubated in three soils contaminated with As, Cu, Pb and Zn. The concentration and speciation of metal(loid)s in pore waters and the mobility and partitioning in casts were compared with earthworm-free soil. Generally the concentrations of water extractable metal(loid)s in earthworm casts were greater than in earthworm-free soil. The impact of the earthworms on concentration and speciation in pore waters was soil and metal specific and could be explained either by earthworm induced changes in soil pH or soluble organic carbon. The mobilisation of metal(loid)s in the environment by earthworm activity may allow for leaching or uptake into biota

Path integrals and degrees of freedom in many-body systems and relativistic field theories

The identification of physical degrees of freedom is sometimes obscured in the path integral formalism, and this makes it difficult to impose some constraints or to do some approximations. I review a number of cases where the difficulty is overcame by deriving the path integral from the operator form of the partition function after such identification has been made.Comment: 15 pages, volume in honor of prof.Yu.A.Simono

Boson Dominance in nuclei

We present a new method of bosonization of fermion systems applicable when the partition function is dominated by composite bosons. Restricting the partition function to such states we get an euclidean bosonic action from which we derive the Hamiltonian. Such a procedure respects all the fermion symmetries, in particular fermion number conservation, and provides a boson mapping of all fermion operators.Comment: 12 page