Abstract. Samples of forty sewage sludges taken in England during 1979 were analysed for ten heavy metals using a rapid flameless atomic absorption spectroscopic technique. For all metals the mean concentrations were influenced by a small number of sludges containing exceptionally high concentrations. Typically, the concentration ranges showed approximately a 100-fold spread. Calculations based on U.K. guidelines for limiting the addition of toxic metals in sludge to agricultural soils indicated that application rates would theoretically be limited for more than 75% of the sludges by the concentrations of Zn, Cu and Ni, expressed additively as the Zn equivalent. Calculations of the theoretical maximum quantities of sludges which could be applied to land on an annual basis suggested that a significant proportion of the sludges would be unsuitable for application to agricultural land at rates of more than 2 t ha('-1) yr('-1).

Laboratory experiments were conducted to determine the effects of Kepone on the larval development of the mud-crab, Rhithropanopeus harrisii, and the commercial blue-crab, Callinectes sapidus, from the time of hatching until the 1st crab stage was reached. Differential survival of R. harrisii from hatching to 1st crab stage occurred in a range of 35 to 125 ppb Kepone, whereas differential survival of C. sapidus over the same period of development occurred in a range of 0.1 to 1.0 ppb. Statistical analysis indicated that, for every 10 ppb Kepone added, duration from hatching to 1st crab stage of R. harrisii was increased by 0.391+/-0.043 days; whereas for each increase of 0.1 ppb, the duration from hatching to 1st crab stage of C. sapidus is prolonged by 0.38+/-0.10 days. The 1st and 2nd zoeal stages of R. harrisii were the most sensitive developmental stages to Kepone, but the 1st zoeal stage of C. sapidus was not sensitive, statistically, to any concentration of Kepone tested. In zoeal stages II, III and IV, there were significant increases in mortality of C. sapidus over the previous stage in all media tested.