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ABSTRACT Groundwater is an important resource in the UK, with 45% of public water supplies in the Thames Water region derived from subterranean sources. In urban areas, groundwater has been affected by anthropogenic activities over a long period of time and from a multitude of sources. At present, groundwater quality is assessed using a range of chemical species to determine the extent of contamination. However, analysing a complex mixture of chemicals is time-consuming and expensive, whereas the use of an ecotoxicity test provides information on (a) the degree of pollution present in the groundwater and (b) the potential effect of that pollution. MicrotoxTM, EcloxTM and Daphnia magna microtests were used in conjunction with standard chemical protocols to assess the contamination of groundwaters from sites throughout the London Borough of Hounslow and nearby Heathrow Airport. Because of their precision, range of responses and ease of use, Daphnia magna and MicrotoxTM tests are the bioassays that appear to be most effective for assessing groundwater toxicity. However, neither test is ideal because it is also essential to monitor water hardness. EcloxTM does not appear to be suitable for use in groundwater-quality assessment in this area, because it is adversely affected by high total dissolved solids and electrical conductivity. [ABSTRACT FROM AUTHOR]

Sediment cores were collected from Lake Erhai, which is located on the Yunnan–Guizhou Plateau, a landform formed by the uplift of the Himalayas. These sediments were deposited up to about 697±15 years ago based on 210Pbex and 137Cs dating. δ13Cinorg, δ18Oinorg and δ13Corg values and concentrations of Cinorg, Corg, N and P within the sediment cores have been measured. Corg has an average deposition flux of 12.7 g/m2, and an accumulation flux of 7.20 g/m2. The calculated decomposition rate constant is 0.017 a−1 with a half life of 40 a. δ13Cinorg and δ18Oinorg values range from −1.6 to −7.9‰ and −5.7 to −13.6‰, respectively, and show similar trends over the past 700 years, which is interpreted to be controlled mainly by temperature, corresponding to climatic changes of two and half periods of a ‘warm–cold–warm’ cycle. δ13Corg ranges from −25 to −28‰, indicating that the organic matter originated mainly from land-derived plants, with overprinting from anthropogenic activities over the past 460 years (since 1537 ad). N and Porg concentrations show a similar vertical distribution to Corg. Atomic ratios of organic carbon and nitrogen (C/N) are 5.8 and 6.8 for the deposition and accumulation stages, respectively, similar to the Redfield ratio in the ocean. The C/P ratio, however, is higher than that in the ocean. The vertical distribution of carbon in the sediment cores indicates that Lake Erhai has the characteristics of both an inland lake (land-derived organic matter) and the ocean (similar C/N ratio). The lower C/N and C/P ratios in the lake Erhai sediments are characteristic for a lake at high altitude and in a subtropical region. This ‘low latitude–high altitude effect’ is probably related to the uplift of the Himalayas. [Copyright &y& Elsevier]

Groundwater is a complex mixture of chemicals that is naturally variable. Current legislation in the UK requires that groundwater quality and the degree of contamination are assessed using chemical methods. Such methods do not consider the synergistic or antagonistic interactions that may affect the bioavailability and toxicity of pollutants in the environment. Bioassays are a method for assessing the toxic impact of whole groundwater samples on the environment. Three rapid bioassays, Eclox, Microtox and ToxAlert, and a Daphnia magna 48-h immobilisation test were used to assess groundwater quality from sites with a wide range of historical uses. Eclox responses indicated that the test was very sensitive to changes in groundwater chemistry; 77% of the results had a percentage inhibition greater than 90%. ToxAlert, although suitable for monitoring changes in water quality under laboratory conditions, produced highly variable results due to fluctuations in temperature and the chemical composition of the samples. Microtox produced replicable results that correlated with those from D. magna tests.