Numerous studies have been carried out in the Fal Estuary examining the potential biological impact of the release of mine waste into the area. The Wheal Jane mine water pollution incident stimulated a number of studies looking into both the immediate and the long term uptake of metals by organisms living in the estuary. Much of this work has been carried out through the Plymouth Marine Laboratory (see www.pml.ac.uk) who pioneered the use of biological indicators in the assessment of the level of metal contamination, particularly in the estuaries of SW England (Bryan et al., 1980; Bryan et al., 1987; Bryan and Langston, 1992). One of the most difficult issues relating to the biological studies is the potential sources of metal contaminants which may be available for uptake by plants and animals. The Wheal Jane incident highlights this issue; whilst the plume of mine water which was discharged into the estuary was contaminated with heavy metals and was also very visual due to the presence of Fe hydroxides being carried in suspension in the water, the incident did not cause any change in either the animals living within the estuarine sediments or the sediment chemistry itself. There is still significant mine water discharge into the area despite the Wheal Jane treatment plant. However, it is likely that the majority of the metals in the estuary are not being discharged in solution in mine water drainage. Instead they are present as particulate mine waste, and their potential bioavailability is controlled by the chemistry of the sediments and the chemistry of the minerals which have been released into the estuary. If the particulate minerals are reactive in the chemical environment present in the estuary then they may either release metals into solution or, alternatively, lead to the growth of new minerals within the estuarine sediments. It is clear from previous work carried out both in the Fal Estuary and also in the Hayle and Gannel estuaries that new minerals containing copper, lead or zinc are actively growing within the sediments. Research has yet to be carried out to identify the relative contribution of metals in solution from the discharge of mine water into the estuary versus the flux of metals from the sediments which contain a significant volume of particulate mine waste.
During the Wheal Jane Incident there was concern that the metals released in the mine water would have a marked biological impact. However, several studies have shown that the pollution event actually had very little, if any, biological effect. A study by Somerfield et al. (1994a) sampled the sediments in several creeks around the Fal Estuary both prior to, and after, the Wheal Jane mine water discharge. The sediment samples were chemically analysed, and the number and diversity of copepods and nematodes in the sediments was examined. Samples from Restronguet Creek were more metal-rich than any of the other creeks studied and had a different community of nematodes and copepods. However, no changes in either the sediment chemistry or the faunal assemblage were recognised following the Wheal Jane event. The different copepod and nematode assemblage at Restronguet Creek was a consequence of the prolonged long term pollution of the creek rather than the short lived Wheal Jane event (Somerfield et al., 1994a). Other studies of copepods within streams in Cornwall have also shown that different assemblages are present in areas with significant metal contamination (Burton et al., 2001)
Other studies have also demonstrated enhanced uptake of metals by organisms living in Restronguet Creek when compared with other areas in the Fal Estuary. For example Williams et al. (1998) analysed both sediment samples and tissue samples from the polychaeta Nephtys hombergi which had elevated zinc and copper concentrations in samples collected from both Restronguet Creek and Mylor Creek. Other work has compared the overall macrobenthic community in the Fal Estuary with other estuaries in SW England. Warwick (2001) sampled five creeks in the Fal Estuary (Restronguet, Mylor, Pill, St. Just and Percuil) both before and after the Wheal Jane incident. Twenty cm deep sediment cores were recovered and the sediment samples were sieved on a 0.5 mm mesh. All of the invertebrates recovered were then identified and counted. The samples from the Fal Estuary were then statistically compared with data from 40 other estuary sites in SW England. Overall the Fal Estuary sediments have a distinctive faunal assemblage, lacking the common crustaceans Corophium volutator and Cyathura carinata, whilst having more abundant taxa such as small sabellid polychaetes (Manayunkia aestuarina and Fabrica sabella), small spionid polychaetes (Pygospio and Streblospio) and oligochaetes. Warwick (2001) suggests that the absence of these crustaceans in the Fal is a direct consequence of heavy metal contamination as is the higher abundance of the other taxa recognised. Pedersen and Lundebye (1996) showed that samples of the shore crab Carcinus maenas had elevated levels of Cd and Cu in the midgut glands in comparison with the same species from sites without heavy metal contamination. Nematodes also appear to be sensitive indicators of the level of metal contamination both in field based studies (Somerfield et al., 1994b; Millward and Grant, 2000) and also in experimental studies (Austen and Somerfield, 1997; Mutwakil et al., 1997). Austen and Somerfield (1997) took sediment samples from a number of sites around the Fal and removed any fauna from the samples. Nematodes collected from the Lynher Estuary which lacks metal contamination, were then introduced to the sediment samples which had variable metal concentrations and were then examined to see how the nematode communities changed over a two month period. In the experimental studies the nematode communities in sediments with different metal contents were clearly different by the end of the study, and the most likely cause of this is the original variation in metal content within the sediment samples. Some nematodes from metal contaminated sites have been shown to have small intestinal granules which contain copper, zinc and iron; it is possible that the formation of these granules is a mechanism to detoxify the sediments allowing colonisation of contaminated sites (Millward, 1996). Clearly, if there are metal tolerant invertebrate animals living within the Fal which take up bioavailable metals there are clear implications for other organisms, such as wading birds, which feed upon them.
Other studies in the Fal Estuary have examined the effect of the discharge of mine drainage, with generally an acidic pH, and also elevated metal concentrations on both the diversity and abundance of foraminifera and also the potential for the subsequent dissolution of foraminifera shells within the sediment profile (Stubbles et al., 1996).
In addition to studies examining the uptake of metals by invertebrates living within the Fal Estuary, there have also been a number of studies examining the potential impact of mine waste in Cornwall on human health. Much of this work has focussed on land areas which have significant mine waste contamination, as is the case in the Camborne-Redruth area, and has focussed in particular on health risks associated with arsenic. Exposure to mine waste contamination can potentially affect health, although a clear association between the incidence of disease and exposure to mine waste has not been proven. Arsenic from mine waste could either be inhaled as dust or ingested either in solution or as fine particulate grains. In other areas in the world, a clear association has been demonstrated between exposure to arsenic and lung, liver, bladder and kidney cancer. Preliminary work carried out in Devon and Cornwall reported on the analysis of urine from members of the public living in areas with known mine waste contamination compared against people living in areas without any known contamination. Many of the people living in the areas with mine waste contamination had significantly increased amounts of arsenic in their urine implying that they were ingesting arsenic from the mine waste (Kavanagh et al., 1998). In a similar study, Peach and Lane (1998) examined arsenic concentrations in human hair samples from both Cornish residents and also, for comparison, a control group from Oxfordshire. The Cornish residents had significantly higher arsenic concentrations in their hair, which is indicative of the uptake of arsenic, probably through the food chain. No studies have shown whether this arsenic exposure has led to any detrimental health effects in Cornwall.