Supporting Information for:

Long term evolution of highly alkaline steel slag drainage waters.

Alex L. Riley1* and William M. Mayes1

1Centre for Environmental and Marine Sciences, University of Hull, Scarborough, YO11 3AZ, UK.*Corresponding Author’s E-mail: ; Phone: +44 (0)1723 357258

Prepared for Environmental Monitoring and Assessment, 11 December 2014

This section consists of 1 table, 4 figuresand associated commentary.

Table S1: Number of samples (N) and date ranges of measured parameters at the Dene Burn (DB) and Howden Burn (HB), “-“= no data.

Determinant / DB / HB
N / Date Range / N / Date Range
pH / 145 / 1978 / 2014 / 180 / 1978 / 2014
Alkalinity / 107 / 1978 / 2014 / 140 / 1978 / 2014
Temperature / 50 / 1980 / 2014 / 74 / 1978 / 2014
Al / 64 / 1985 / 2014 / 88 / 1981 / 2014
As / 4 / 1990 / 2014 / 5 / 1990 / 2012
Ca / 87 / 1978 / 2014 / 100 / 1978 / 2014
Cd / 64 / 1985 / 2014 / 98 / 1979 / 2014
Cr / 62 / 1985 / 2014 / 98 / 1979 / 2014
Cu / 65 / 1985 / 2014 / 100 / 1979 / 2014
Fe / 2 / 2014 / 2014 / 18 / 1978 / 2014
Li / 2 / 2014 / 2014 / 4 / 2010 / 2014
Mg / 23 / 1994 / 2014 / 4 / 2004 / 2014
Mn / 2 / 2014 / 2014 / 3 / 2010 / 2014
Mo / - / - / - / 3 / 2010 / 2014
Ni / 50 / 1985 / 2014 / 99 / 1979 / 2014
Pb / 52 / 1985 / 2014 / 97 / 1979 / 2014
Sb / - / - / - / 1 / 2012 / 2012
V / 2 / 2014 / 2014 / 4 / 2010 / 2014
Zn / 56 / 1985 / 2014 / 101 / 1979 / 2014

Fig.S1: Drainage channel extent of Dene Burn (sample prefix DB) and Howden Burn (HB) through time - 1899, 1994 (before break in data (Fig.4), and 2014 (after break in data (Fig.4)).

The infilling of headwater areas of the Dene and Howden Burn with slag has led to a drastic reduction in the overall extent of these streams over time (Fig.S1). The fact that slag has been infilled in areas of previous surface water leads to significant volumes of water being stored and transmitted through the slag, which ultimately generates the hyperalkaline waters upon resurgence via the drainage systems. The streams have also become more fragmented with sections of previously continuous surface-flow now sinking and re-emerging downstream. Comparisons of the Howden Burn stream network between 1994 and 2014 can give explanation to the observed breakpoint in Fig.4. Although spatial changes were marginal over this time period, a large pipeline was installed directly over the Howden Burn, shown on Fig.S1. This was installed to redirect a Combined Sewer Overflow (CSO) at the top of the system that previously drained into the Howden Burn to a treatment works to the north of the site. While there are still occasional overflow events (as evidenced by field observations on sewage-related pollution and documented incidents: EA 2014), this redirection of surface waters away from the Howden Burn leads to a relative increase in the proportion of slag leachate in the stream. As such the break in data reported in Fig.4 is apparent with an increase in pH, Total Alkalinity and Ca concentration at the time of pipeline installation, and fewer major dilution events that are apparent in the earlier record.

Reference:

EA. (2014). What’s in your backyard? [online] Available at: <

Fig.S2: Emergence of Howden Burn from subterranean drainage network beneath slag deposits. Calcite precipitation (brown) visible on stream bed and tunnel walls.

Fig.S3: Example of amorphous calcite deposits smothering stream bed and debris in an area of low flow in the Dene Burn.

Fig.S4: Example of calcite precipitate formations within a high-flow cascade. In-stream debris acts as nuclei for the generation of irregular nodules.

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