Mark P. Taylor

2000 years of sediment-borne heavy metal storage in the Yorkshire Ouse basin, NE England, UK

Floodplain overbank sediments are often used to evaluate the influence of environmental change on sediment and chemical fluxes within river basins. This paper presents the results of an investigation of heavy metal storage in seven floodplain reaches in the Yorkshire Ouse basin in north-east England. Floodplain heavy metal storage has been greatest since c. 1750, and many of the post-1750 sedimentary units exhibit heavy metal values that exceed recommended trigger and guideline values for contaminated land. Relatively high heavy metal storage occurs from ad 1250–1750 in most of the reaches. These patterns are related to 2000 years of Pb and Zn mining in the Yorkshire Dales and c. 250–300 years of industrial and urbanization activity around Leeds and Bradford, and increased delivery of fine-grained sediment during the last millennium, possibly owing to factors such as population growth and agricultural expansion during the Middle Ages, and climate change during the Little Ice Age. Copyright

Historic metal mining inputs to Tees river sediment

Historic metal mining has greatly influenced sediment delivery and metal contamination in the Tees River Basin. Investigations of metal-contaminated overbank river sediment show that sediment-borne metal concentrations decrease downstream of mining areas. Metalliferous mineralogy also changes: sulphides and carbonates are abundant in the upstream part of the basin, and both decline and disappear downstream where iron oxyhydroxides dominate. Mineral compositional and textural information can be used to trace sources of mining-related contaminated sediment. Sulphides, carbonates, and oxyhydroxides which pseudomorph ore deposit minerals, are interpreted to be derived from outcropping ore bodies and mine-waste tips. The relative abundance of these grains suggests that the ore bodies and mine-waste tips are still important sources of metal pollutants. This is corroborated by morphological mapping and coring of Tees floodplain sequences, which also suggests that metal-contaminated alluvium downstream has experienced limited re-working.

The variability of heavy metals in floodplain sediments: A case study from mid Wales

Abstract A series of vertical alluvial profiles from the upper River Severn floodplain at Welshpool ranging in age from Late Pleistocene to the present have been examined for their Ni, Cu, Zn, Cd, Ba and Pb concentrations. The floodplain deposits have been variably contaminated with heavy metals following extensive metalliferous mining in the upper catchment during the mid-19th century. The data are used to establish whether vertical increases in concentrations can be used to indicate a younging-upwards of the sediments. The data show that grain size and organic content do not influence heavy metal concentrations. Although some of the most recent alluvial profiles contain the highest levels of contamination, a great deal of variation exists, not only between the general vertical distribution of individual metals but also between the absolute values themselves. There was no consistent age-concentration relationship in the vertical profiles. Pb displays the least complex picture with predominantly increasing values towards the top of the alluvial profiles in the historically sedimented sites, indicating a younging-upwards. Rapid sedimentation and post-depositional processes such as leaching, particle translocation or the lateral migration of groundwaters enriched in heavy metals result in different vertical heavy metal distributions at superficially similar sites. It is recommended that sampling strategies for contaminated floodplain sediments utilise a multiple profile approach including the whole range of sediment types, ages and depositional forms that are known to exist at a study site.

The spatial distribution of heavy metal contaminated sediment across terraced floodplains

Abstract Deposits of fine alluvial sediment contaminated by heavy metals derived from mining provide an opportunity to reconstruct the alluvial histories of mineralised catchments. Field data were collected to identify the spatial distribution of heavy metal contamination in surficial floodplain sediments and establish the relationships between terrace height, terrace age and metal concentrations. Floodplain terrace morphology was mapped and terrace heights were measured for three separate study reaches in the upper Sevem Basin, mid-Wales. Concentrations of Pb, Ba and Zn were determined in 97 samples taken from fine overbank units capping these terrace surfaces. Between the three study reaches, element concentrations showed wide ranges (Pb 11–964ppm; Ba 141–1118 ppm; Zn 73–1134 ppm). They also exhibited significant spatial variation across the floodplain at each study reach (e.g. at Llandinam, Pb 36–964ppm, Ba 141–1118 ppm and Zn 173–1134 ppm). Peak metal concentrations at Morfodion (Pb 399 ppm, Ba 474 ppm) and Welsh-pool (Pb 149 ppm, Ba 558 ppm) were found on terrace surfaces 1.5–2.5m and 2.0–3.0 m, above present river level, respectively. Lower concentrations reflect natural background levels of contaminants (higher terraces) and post-mining reworking of spoil heaps and floodplains (lower terraces). In general, the spatial distribution of floodplain contaminants is more significantly correlated with terrace height than with terrace age. Different flooding mechanisms and styles of channel instability in relation to the timing and mode of sedimentation have resulted in different patterns of floodplain contamination. Focused deposition, particularly in palaeochannels, is also an important mechanism for creating strongly contaminated sites within the floodplain environment.

River behaviour and Holocene alluviation: The River Severn at Welshpool, mid-Wales, U.K.

A combination of archaeological evidence, 14C dates, terrace mapping, heavy metal analysis, grain size analysis and historical maps is used in a detailed analysis of the alluvial history of the River Severn floodplain around Welshpool in mid-Wales, U.K. ‘Welshpool Gravels’ underlie a higher terrace surface up to 6–7 m above the present channel. They form a sequence of gravels at least 30 m in thickness. The upper surface is characterized by a series of braided palaeochannel patterns. These sediments were probably deposited at the end of the last glaciation as outwash, and are contemporaneous with other high, gravelly terrace deposits found in the Severn and other mid-Wales basins. Overlying the Welshpool Gravels on the contemporary floodplain are a variable thickness of finer sediments, the ‘Leighton Silts’. Morphological mapping and dating of two cut-offs to 2850 ± 60 a BP and 1190 ± 70 a BP indicates that a channel pattern similar to the present planform had formed by the mid to late Holocene. From this period, floodplain development has been dominated by a single-thread meandering channel with fine vertical sedimentation and limited lateral gravel accretion. Abandonment of extended lengths of channel formed by an avulsion mechanism is apparent. A combination of historical map data, 14C dates and the analysis for heavy metals in fine sediments, which were washed into the river system during mining, indicates that there has been at least 4 m of sedimentation since the early 17th century, but only in a central belt of varying width. Metal-rich waste, identified in the fine sediments of this zone of ‘Trehelig Silts’, indicates those areas which were most heavily sedimented during the peak of metalliferous mining in the 18th and 19th centuries. Although the near-channel margins appear to be superficially similar to the older floodplain, the spatial and vertical pattern of historic sedimentation is complex, and is not reflected in marked elevation differences. The division of sedimentation periods into these three broad time-spans (Late Quaternary Terraces, Late Holocene alluviation and avulsion, and the historical metal-mining period) shows that an apparently simple planar floodplain is in reality underlain by complex sedimentation units. Floodplain construction has involved the development of inset units, in cut-offs and adjacent to migrating channels, as well as the expected contrasts between in-channel and overbank environments. This has implications both for alluvial sedimentation modelling and for the identification of high-pollution zones on the floodplain. These cannot be predicted on the basis of simple ‘in-channel’ and ‘overbank’ environments given the historically complex evolution.

Non-synchronous response of adjacent floodplain systems to Holocene environmental change

Abstract Two adjacent upland floodplains are compared to establish the local response of floodplains to environmental change. Radiocarbon dating, the analysis of sedimentary exposures, terrace mapping, aerial photography and archaeological evidence are used to examine Late Quaternary valley fill sediments on the Afon Tanat and the Afon Vymwy in the Upper Severn Basin, Wales, UK. The alluvial stratigraphy of the two floodplain systems consists of Late Devensian (last glacial) fluvio-glacial sediments at the valley margins deposited under a braided outwash river regime. Holocene age terraces, with floodplain and palaeochannel deposits composed of gravels overlain by silty-sands, are inset into this older unit and were formed by meandering fluvial channel systems. A combination of field and laboratory data demonstrates that from the mid-late Holocene the two floodplain systems had divergent development. The Afon Vyrnwy has remained vertically stable for the last ca. 4000 yrs. whereas the adjacent Afon Tanat continued to be vertically and laterally active. Both floodplain systems have been affected by Late Quaternary climatic fluctuations and anthropogenic activity from the Bronze Age to the Roman period, but local geomorphic gradient controls, combined with a possibly greater focus of anthropogenic activity in the Tanat catchment, may explain the differential evolution of the two systems. The data demonstrate that multiple reach-scale studies are essential for revealing significant stages in the chronology and historical development of fluvial systems.

Substitution of PFAS chemistry in outdoor apparel and the impact on repellency performance

Intensifying legislation and increased research on the toxicological and persistent nature of per- and polyfluoroalkyl substances (PFASs) have recently influenced the direction of liquid repellent chemistry use; environmental, social, and sustainability responsibilities are at the crux. Without PFAS chemistry, it is challenging to meet current textile industry liquid repellency requirements, which is a highly desirable property, particularly in outdoor apparel where the technology helps to provide the wearer with essential protection from adverse environmental conditions. Herein, complexities between required functionality, legislation and sustainability within outdoor apparel are discussed, and fundamental technical performance of commercially available long-chain (C8) PFASs, shorter-chain (C6) PFASs, and non-fluorinated repellent chemistries finishes are evaluated comparatively. Non-fluorinated finishes provided no oil repellency, and were clearly inferior in this property to PFAS-finished fabrics that demonstrated good oil-resistance. However, water repellency ratings were similar across the range of all finished fabrics tested, all demonstrating a high level of resistance to wetting, and several non-fluorinated repellent fabrics provide similar water repellency to long-chain (C8) PFAS or shorter-chain (C6) PFAS finished fabrics. The primary repellency function required in outdoor apparel is water repellency, and we would propose that the use of PFAS chemistry for such garments is over-engineering, providing oil repellency that is in excess of user requirements. Accordingly, significant environmental and toxicological benefits could be achieved by switching outdoor apparel to non-fluorinated finishes without a significant reduction in garment water-repellency performance. These conclusions are being supported by further research into the effect of laundering, abrasion and ageing of these fabrics.