J.M. Bubb

Metal accumulation within salt marsh environments: a review

A comprehensive assessment of the chemical and physical factors affecting metal accumulation and cycling within salt marshes is presented. The effects that changes in physico-chemical properties (redox potential, salinity, pH, etc.) have upon metal mobility, speciation and consequent biological availability are described together with the implications for salt marsh habitat loss. Salt marshes act as very efficient sinks for metal contaminants although metal concentrations in halophytes do not generally reflect environmental contamination levels. Marine angiosperms, particularly Zostera marina, do however, reflect external metal concentrations and can therefore be used as biomonitors. Evidence suggests that the concentration of heavy metals in the sediments of most estuaries is not sufficiently high to cause ill effects to salt marsh plants although further investigations are necessary to assess potential threats of pollutants upon the health of these intertidal ecosystems.

Temporal distribution of organotins in the aquatic environment: Five years after the 1987 UK retail ban on TBT based antifouling paints☆

Abstract In 1987 the UK government introduced legislation to control the sale of tributyltin (TBT) based paints. Between 1990–1992, a monitoring programme of waters and surficial sediments from six estuarine river systems was undertaken for TBT and its degradation products; dibutyltin (DBT) and monobutyltin (MBT). Despite the retail ban on tributyltin based antifouling paints for use on vessels

Organotin distribution in sediments and waters of selected east coast estuaries in the UK

An extensive spatial survey of butyl- and methyltin compounds in the sediments and water column of seven Suffolk and Essex estuaries was undertaken between June and August 1990 to determine the main areas of organotin contamination. A number of these estuaries contain important shellfisheries and all have a high degree of boating activity. Speciation of organotins was performed by a purge and trap/boiling point separation method and detected by Atomic Absorption Spectrometry. Despite the implementation of the 1987 UK retail ban on tributyltin (TBT) based antifouling paints on vessels <25 m in length, 7 of the 17 sites sampled exhibited TBT water concentrations above the Environmental Quality Target (EQT) set in 1987. Water column concentrations ranged from <3–71.2 ng l−1. Dredging had occurred at some of these sites indicating that desorption of TBT from the sediment may occur following sediment disturbance. Surficial sediment organotin concentrations displayed high spatial variability with TBT levels ranging from <3–3935 ng g−1. The highest organotin concentrations occurred at sites with high levels of boating activity.

Anthropogenic heavy metal inputs to lowland river systems, a case study. The River Stour, U.K.

Surface waters, sediments and interstitial waters were collected from 9 sites of the River Stour, UK, during June 1987. The aim was to identify the sources of EC List I (Hg, Cd) and List II (As, Cr, Cu, Ni, Pb, Zn) metals and metalloids to this lowland river system and to assess the magnitude of metal enrichment. The study reach spanned some 60 km, traversing rural and urban landscapes. Results indicate that the larger municipal sewage treatment works (STW), which receive industrial effluents, were the major source of metals, but smaller rural works also exerted some contaminative influences. Metal concentrations in bottom sediments, displayed 2–11 fold increases over catchment background levels with maximum loadings coinciding with discharges from the Great Cornard and Sudbury STWs. Elevations in water column metal concentrations were also apparent downstream of point source inputs, but concentrations were consistently below designated ‘Water Quality Standards’. Distance from the point source, sediment texture and hydrology appeared to be the main factors responsible for the observed distribution of metals within this river system.

The occurrence and distribution of trace metals in halophytes

Abstract Sediments and selected halophytic plants from two salt marshes in Essex (UK) were analysed for the occurrence of a variety of metals including arsenic (As), calcium (Ca), cadmium (Cd), chromium (Cr), copper (Cu), iron (Fe), mercury (Hg), potassium (K), magnesium (Mg), manganese (Mn), sodium (Na), nickel (Ni), lead (Pb), selenium (Se) and zinc (Zn). The majority of metals occurred in the sediments at concentrations lower than or approaching the shale standard. This, however, was not the case for Cd, Hg and Pb at Two Tree Island salt marsh which is situated on the Thames Estuary. At this more industrialized site these non essential elements were enriched in the sediments and halophytic plants but at concentrations that did not appear to affect the well being of the plants. Only Zn concentrations in plant material reflected levels within the sediment. The occurrence and distribution of metals within different halophytic species was compared by analysing roots and aerial parts from Salicornia spp., Spartina spp., Aster tripolium and Atriplex portulacoides (Halimione portulacoides syn. ) . In general, the metals accumulated mainly in the roots and were not transported to the aerial parts with the exception of the chemically mobile elements; Cd, Mn and Zn which were more evenly distributed. The halophytes chosen in this study did not reflect the concentration of metals within the surficial sediments and are, therefore, not suitable as indicators for sediment pollution.

The significance of sediment metal concentrations in two eroding Essex salt marshes

Abstract Two eroding salt marshes, at Dengie and Little Oakley, situated along the Essex coast (UK) were monitored for concentrations of As, Ca, Cd, Cr, Cu, Fe, Hg, K, Mg, Mn, Na, Ni, Pb, Se and Zn in bulk sediment and in the

The effectiveness of the 1987 retail ban on TBT based antifouling paints in reducing butyltin concentrations in East Anglia, UK

Abstract Butyltin concentrations were measured at twelve freshwater sites in the Norfolk Broads, UK during July 1992 at sites previously found to be contaminated with tributyltin (TBT). Only 1 site revealed detectable butyltin concentrations in the water column. Surficial sediment TBT concentrations ranged from −1 and were markedly lower than in 1989. Elevated loadings were found in the vicinity of marinas and boatyards and where TBT was present, dibutyltin (DBT) and monobutyltin (MBT) were usually found. The present study illustrates that controls instituted in the UK in 1987 on the use of TBT based paints have been effective in reducing water column and, to a lesser extent, surficial sediment concentrations in freshwater reaches of the Norfolk Broads.

Depositional profiles and relationships between organotin compounds in freshwater and estuarine sediment cores

A range of organotin compounds including tributyltin (TBT), dibutyltin (DBT) and monobutyltin (MBT) were measured in sediment cores collected from contaminated freshwater and estuarine sites in Essex and Suffolk, U.K. Butyltin compounds were found in significant quantities at depths of up to 60 cm within the sediments of marina and boatyard complexes with TBT concentrations ranging from <3 ng g−1 (the detection limit) to >3000 ng g−1. In general sediment TBT concentrations decreased with depth, but maximum enrichment tended to occur just below the surface. It was evident from these core profiles that the accumulation of organotins in surface deposits was on the decline and coincided approximately, with the implementation in 1987 of the UK retail ban on the sale of TBT based antifouling paints for application on vessels <25 m in length. The degradation rate for TBT in sediments was found to exhibit first order kinetics with half lives ranging from 0.9–5.2 years between different sites. Estimated degradation rates have also been determined for DBT and MBT. These ranged from 1.5–3.0 years for DBT and 1.8–3.7 years for MBT.

Spatial distribution of organotins in sediments of lowland river catchments.

A method is described for the measurement of nanogram quantities of a range of methyl and butyltin compounds. The method utilises a modified purge and trap/boiling point separation technique for the determination of organotin compounds in sediment samples. A spatial survey of sediment samples within 5 river systems in the East Anglia region of the United Kingdom was undertaken and identified a range of organotin compounds with concentrations of tributyltin (TBT) ranging from <3.9 ng g(-1) up to 1291 ng g(-1). The highest values were found in areas connected with boating activities. Wherever TBT was present, dibutyltin and monobutyltin were most commonly found along with small concentrations of certain methyltins.

Magnitude and distribution of anthropogenic contaminants in salt marsh sediments of the Essex coast, UK. II. Selected metals and metalloids

Abstract Total concentrations of selected metals and metalloids; As, Ca, Cd, Cu, Cr, Fe, Hg, K, Mg, Mn, Na, Ni, Pb, Se and Zn were determined in the sediments of five salt marsh sites along the Essex coast of the UK. A fairly ubiquitous degree of metal and metalloid contamination was found within the sediments of all the salt marshes investigated. The extent of contamination by individual metal species was dependent upon the nature of the site-specific inputs. The enrichment of industrially derived metals, such as Hg and Cd, for example, occurred at sites adjacent to urban areas; Two Tree Island (situated on the outer Thames Estuary) and to a lesser extent South Woodham Ferrers (situated on the River Crouch). Lead concentrations were elevated at all five sites inferring that a significant input was derived from a common generic source, such as atmospheric deposition. The distribution of metals and metalloids within individual salt marsh sites was dependent upon a number of factors including sediment type, the hydrological regime, the presence of vegetation, redox potential and organic matter content.