The spatial distribution and source of arsenic, copper, tin and zinc within the surface sediments of the Fal Estuary, Cornwall, UK

Abstract

Estuarine sediments commonly form major sinks for contaminants released during industrial activity. Many industrial processes lead to the release of metals initially in solution, which can then be adsorbed on to, for example, Fe hydroxides or clay minerals. However, in the mining industry, there are two major contaminant waste streams: (1) metals discharged in solution via mine drainage; and (2) particulate grains of the ore-forming or related minerals released after ore processing. The release of particulate waste can have a major long-term impact on environmental geochemistry. In this study, we have mapped the distribution of arsenic, copper, tin and zinc within the surficial sediments of the Fal Estuary, Cornwall, UK, an area that drains a historically important polymetallic mining district. There are clear spatial variations in the contaminants, with the highest levels (> 2800 p.p.m. As, > 5000 p.p.m. Cu, > 3000 p.p.m. Sn and > 6000 p.p.m. Zn) within Restronguet Creek on the western side of the estuary. Mineralogical studies show that small (< 20 lm) grains of detrital arsenopyrite, chalcopyrite, cassiterite and sphalerite are very abundant within the surface sediments. Most of the sulphide grains are fractured, but mineralogically unaltered, although some grains show alteration rims caused by oxidation of the sulphides. The geochemistry and mineralogy are indicative of sediment supply from the discharge of particulate waste into the estuary during historical mining activity. Subsequently, this particulate waste has been largely physically and biologically reworked within the surface sediments. Although considerable effort has been made to minimize contaminants released via mine drainage into the estuary, the potential flux of contaminants present within the intertidal and subtidal sediments has not been addressed. Benthic invertebrates living within the area have adapted to be metal tolerant, and it is likely that the dominant source of bioavailable metals is a result of alteration of the particulate mine waste present within the intertidal and subtidal sediments.

Characterization of harbor sediments from the English Channel: assessment of heavy metal enrichment, biological effect and mobility

“…Previous authors (Hughes, 1999;Pirrie et al, 1997Pirrie et al, , 2002Pirrie et al, , 2003 reported the presence of As, Cu, Hg, Pb and Zn in estuarine areas of Falmouth and Fowey due to mining activities. Sediments from estuaries of the Thames, Stour and Orwell also present significant enrichments of Cd, Cu, Hg, Pb and Zn (Wright and Mason, 1999).…”

Appropriate sampling strategy and analytical methodology to address contamination by industry: Part 1. Conceptual model of a sampling design and sampling types

“…Many river basins in the world are seriously affected by heavy metals released into the environment from mining and industrial activities as shown by Wolfenden and Lewin [43]; Swennen et al [44]; Hursthouse et al [45]; Hudson-Edwards et al [46]; and Pirrie et al [47]. Polluted particles are transported and deposited into the floodplains and wetlands, which act as a temporary sink for heavy metal deposition and storage in river basins [48].…”

“…Although originally developed for mineral exploration, actual river sediment reconnaissance surveys have subsequently been found to be of great value for highlighting geochemical anomalies, as well as for showing the regional patterns of nearby soils [54]. Spread of contaminants can occur along rivers which drain industrial areas as shown by Wolfenden and Lewin [43], HudsonEdwards et al [46], Hursthouse et al [45,55], Pirrie et al [47] and Sullivan and Taylor [56]. Moreover sediments become enriched with many heavy metals due to continuous deposition of suspended particles from the overlying water [57], or by dust particles [29].…”

Impact of metallurgy on the geochemical signature of dusts, soils and sediments in the vicinity of Elbasan complex (Albania)

“…Spread of contaminants can occur along rivers which drain the industrial areas as shown by Wolfenden and Lewin [24], Hudson-Edwards et al [25], Hursthouse et al [26], Pirrie et al [27]. The sediments become enriched with many heavy metals due to continuous deposition of suspended particles from the overlaying water [28], or by dust particles [29].…”