Long-term evolution of highly alkaline steel slag drainage waters

Abstract

The disposal of slag generated by the steel industry can have negative consequences upon the surrounding aquatic environment by the generation of high pH waters, leaching of potentially problematic trace metals, and rapid rates of calcite precipitation which smother benthic habitats. A 36-year dataset was collated from the long-term ambient monitoring of physicochemical parameters and elemental concentrations of samples from two steel slag leachate-affected watercourses in northern England. Waters were typified by elevated pH (>10), high alkalinity, and were rich in dissolved metals (e.g. calcium (Ca), aluminium (Al), and zinc (Zn)). Long-term trend analysis was performed upon pH, alkalinity, and Ca concentration which, in addition to Ca flux calculations, were used to highlight the longevity of pollution arising as a result of the dumping and subsequent leaching of steel slags. Declines in calcium and alkalinity have been modest over the monitoring period and not accompanied by significant declines in water pH. If the monotonic trends of decline in alkalinity and calcium continue in the largest of the receiving streams, it will be in the region of 50–80 years before calcite precipitation would be expected to be close to baseline levels, where ecological impacts would be negligible.Electronic supplementary materialThe online version of this article (doi:10.1007/s10661-015-4693-1) contains supplementary material, which is available to authorized users.

What Causes Carbonates to Form “Shrubby” Morphologies? An Anthropocene Limestone Case Study

“…Our case study, Consett in the United Kingdom, exhibits pH even higher than in the ophiolite springs (9-13), and supports exceptional rates of calcite precipitation (up to 100 g m −2 day −1 ) (Mayes et al, 2008). The diversity and extremely good preservation of the crystals from these carbonates, exceptionally well constrained local hydrochemical environment (Mayes et al, 2008(Mayes et al, , 2018Riley and Mayes, 2015) and the possibility to directly observe the co-occurrence of specific growth-forms and microbial components at sites of deposition provides a unique opportunity to test hypotheses concerning the mechanics of exotic calcium carbonate crystal growth patterns in nature. This study is the first report of carbonate petrography from this "accidental laboratory" and raises the following question: What carbonate fabrics can emerge from extreme alkaline conditions?…”

“…Samples were taken during May 2013 along pre-established calcite saturation index transects (Mayes et al, 2008(Mayes et al, , 2018Riley and Mayes, 2015) within Dene Burn and Howden Burn (Figure 1) for further analyses in the laboratory. In these streams, calcite saturation is enhanced by four alkaline discharges within the former Consett Iron and Steelworks.…”

Comparison of Hydration Properties of Cement‐Carbon Steel Slag and Cement‐Stainless Steel Slag Blended Binder

“…Furthermore, W n for SS was lower than that for CS at the same replacement ratios at all ages. 2 . For pure cement, calcium hydroxide (CH) content increases with increasing curing age.…”

“…Carbon steel slag and stainless steel slag are the by-products of iron and steel production. Large amounts of steel slags are released every year that also occupies farmlands and consequently leads to serious pollution risks [2,3]. erefore, the utilization of steel slags as mineral admixture can develop the ecological consciousness of both cement and steel production sectors.…”

Main and Trace Element Distribution in Slag-Leachate-Tufa System Precipitate

“…Highly alkaline waters (pH>11) are commonly formed during weathering of iron and steel slags [6]. Due to reaction of the slag material with slightly acidic to neutral rain or runoff waters, lime is hydrolysed to produce hydroxyl ions, which increase the leachate pH: CaO (lime) + H 2 O (l) → Ca 2+ (aq) + 2(OH -Alkaline waters are commonly observed to emerge from slag dumps [e.g., [7][8][9] and also from construction and transportation structures (e.g., road beds, fill material), where the slag material was used [10].…”