Fluvial metal transport near sources of acid mine-drainage: Relationships of soluble, suspended and deposited metal

Abstract

The Afon Goch (Anglesey, UK) is a short (12 km source to estuary) stream highly contaminated by acid mine drainage (AMD) throughout its length, due to past-mining at the head of the stream. Metal distribution is strongly controlled by the pH, which increases downstream particularly at confluences with two unpolluted tributaries. A pH increase causes precipitation of metals, primarily Fe as hydroxide, thus altering the transport of the metal load, potentially allowing storage of metal within the river as deposited material. However, further work suggests that the controls on whether metal can behave non-conservatively, and therefore the controls on metal distribution, are more complicated than being purely pH dependent. This is because much of 3+ the Fe load, even at the low pH at the head of the stream, is not soluble Fe but colloidal Fe hydroxide. Consequently, coagulation is a requisite intermediate step between precipitation and potential for settling. It is possible that in reaches of the stream away from tributary confluences, the process of coagulation is the predominant influence on metal distribution. Furthermore, because much of the metal load in the water column is very fine, its deposition results in a sediment in which the metals can be intimately associated with a biofilm at the sediment/water interface. Such associations change both deposition and erosion characteristics of the sediment and have implications for subsequent diagenesis and mineral morphology.

Stratification and water quality of an abandoned opencast coal pit lake at Raniganj Coalfield Area, West Bengal, India

“…The chromium and manganese concentrations, however, were high (Table ). The mobilization of trace metals depends on the pH of the water (Black & Dave ), with a high pH resulting in co‐precipitation or adsorption of these metals, followed primarily by Fe‐hydroxide minerals (Boult ; Banks et al . ,b; Younger ).…”

Physical and Chemical Parameters Determining Bacterial Growth of Acid Mine Drainage Sites in Southeast Ohio

“…The correlation between pH and sediment precipitation was examined by Boult (1996) who looked at fluvial metal transport in the Afon Goch, a highly contaminated acid mine drainage (AMD) tributary in the United Kingdom. Boult highlighted variations in the composition of the headwaters of the Afon Goch.…”

Water Management at Abandoned Flooded Underground Mines

“…At the Mynydd Parys mine site in Anglesey/Wales, the Afon Goch stream is highly polluted by acid mine drainage with pH values between 2 and 3 (Boult 1996) and elevated concentrations of metals (e.g. At the Mynydd Parys mine site in Anglesey/Wales, the Afon Goch stream is highly polluted by acid mine drainage with pH values between 2 and 3 (Boult 1996) and elevated concentrations of metals (e.g.…”

“…It has also been commonly used in Europe since medieval Times, and in the USA since the 19 th century (Lung 1986). The Mynydd Parys mine site in Anglesey/Wales (compare section 5.7.4) is another mine where metals were extracted from the mine water (Boult 1996). Wright et al (1995) also describe a successful on-site experiment with unsupported liquid emulsion membranes for the extraction of copper in an Arizona/USA copper mine.…”