Geochemical studies of arsenic and some heavy metals in South-East England

The soils of the Weald of South-East England are derived from a complex variety of sedimentary materials, which exhibit strong geochemical variation. This thesis describes detailed research into the biogeochemistry of Arsenic and other heavy metals of the Weald. A short review and introduction to the geology and soil types of the area is presented. The importance of As and human health is emphasised.

Soil samples were taken along eight transects at various points across the geological boundaries and two other specific Wealden areas. The "total"concentration of As , Cu , Zn , Mn , and Fe;DTPA - extractable Cu , Mn , Zn and Fe; Bray P-1 extractable As; LOI (%) and pH were all determined using the fine earth fraction.

To perform analysis for As a sensitive method of detection in the range 0-1.0 yg/g by hydride generation coupled to atomic absorption spectrophotometry was developed and refined. The majority of the Wealden soils have As contents typical of the published data for these soil types. Romney Marsh soils exhibited the highest levels of (x=15 yg/g). An examination of stream sediments indicated that localized pollution had occurred. This anomaly is rationalised in terms cf drainage and soil chemistry. A strong correlation was found for Fe-As (p<0.001).

Trials performed with various plant types in As-spiked soils show a relationship between soil concentration and plant uptake. Yield decreases and plant uptake vary with soil type and crop. The effects were found to be most marked in a calcareous soil with low phosphate content.

Extractions indicated Bray P-1 to be useful in determining plant availability.

Abundance levels for Cu , Mn , Zn and Fe are presented. Argillaceous deposits usually contain greater concentrations than arenaceous. A strong positive correlation was found between Zn and Cu (p<0.001) for all soils.

The DTPA extractions are discussed with regard to soil parent material Generally increased levels of total elements imply increases in available concentrations.

A statistical analysis of the results is reported.