Sampling strategies for water quality monitoring in lakes: the effect of sampling method.

Five different water sampling techniques have been compared in a series of lakes. In deep lakes, no significant differences were observed between mean summer nutrient concentrations measured in (i) a tube sample integrating over the photic zone taken from the deepest point; (ii) a surface dip sample taken at the deepest point; (iii) a surface dip sample taken by wading into the water's edge; (iv) a dip sample taken slightly further off shore by suspending a bottle below a buoy thrown out about 30 m from the shore; and (v) a sample taken along a short transect out from the shore using a model boat to transport the sample bottle. In shallower lakes the integrating tube sampler gave significantly higher estimates of mean concentrations than other methods due to the increase in volume of the unmixed hypolimnion which reduced the depth of the well mixed epilimnion to less than the tube length. For national survey purposes samples taken from the edge of the lake are the most cost effective.

Reversal of acidification in tributaries of the River Duddon (English Lake District) between 1970 and 1998.

Long-term changes in stream water chemistry in the upper Duddon catchment (southwest Lake District, UK) were investigated. Ten streams were sampled and analysed weekly during 1998, and the results compared with data for the early 1970s and 1986. The waters exhibited a range of pH, average values for 1998 being 5.04-7.04. For all the streams, the average pH in 1998 was greater than that during 1971-73. Statistical analysis was carried out, using the 1970s data to estimate the magnitude of inter-annual variation, and taking discharge into account on the basis of antecedent rainfall. The results showed that for two of the streams the pH increase was significant at the 2.5% level, while for a further three it was significant at the 10% level. Comparison of the 1998 concentrations of nitrate and non-marine sulphate with data obtained for five streams in 1973-74 showed that average nitrate concentration had increased from 11 to 20 microeq dm(-3) while that of non-marine sulphate had decreased from 94 to 50 microeq dm(-3). For four of the streams, comparisons were also made between the 1998 data and those for 1986. In three cases, pH in 1998 was generally higher, and Al generally lower, than the values for 1986, but in the fourth case little difference was evident. The present results support observations for five nearby standing waters, strengthening the evidence for a general reversal of acidification in the southwest part of Lake District, due to a decline in the deposition of pollutant sulphur.

Reasons for late detection of hip dislocation in childhood.

A retrospective study of 56 children with dislocation of the hip presenting late found that the mean age at which the parents first noticed that something was wrong (including hip abnormalities found at birth in 10 patients) was 11 months, but that at diagnosis was 26 months, a mean delay of 15 months. The reasons for delay were failure to examine the hips at birth (13 cases), failure to follow up abnormalities at birth (7), failure of symptoms noticed by the parents to alert the health-care professional to the possibility of a dislocated hip (36), failure to check the hips routinely after 3 months (27), and failure of the parents to appreciate the significance of abnormalities and to act on them (28). Hip screening should continue beyond the neonatal period and should include routine checks on all children until they are walking normally. A greater awareness in health-care professionals of the features of hip dislocation and further health education for parents are needed.