Wolfgang Korth

Removal of geosmin and methylisoborneol from drinking water by adsorption on ultrastable zeolite-Y

Abstract Geosmin and 2-methylisoborneol (MIB) were removed from solutions in freshwater (100–180 ng/l) by adsorption on US-Y zeolite (SiO 2 /Al 2 O 3 = 80). The zeolite can be re-used by burning off the adsorbed organics. Adsorption efficiency for geosmin and MIB was not reduced by water hardness or the presence of low concentrations (5 mg C/l) of humic acid.

Chemical Ecology and BiologyIn situ production of volatile odour compounds by river and reservoir phytoplankton populations in Australia

The production of volatile odour compounds by freshwater phytoplankton was monitored weekly from November to April (summer period) 1990/91 at two sites: (1) Hay Weir pool on the Murrumbidgee River, NSW and (2) Carcoar Dam, near Blayney, NSW. During this period, the phytoplankton of the Murrumbidgee River was dominated by two species of the diatom Melosira , and the cyanobacterium Anabaena sp. Carcoar Dam was mostly dominated by the cyanobacteria Microcystis aeruginosa and Anabaena sp. The major odour compounds detected were geosmin, β-cyclocitral, β-ionone, geranylacetone, and 6-methylhept-5-en-2-one. Clmparison of multivariate statistical analyses of the volatile odour compound profiles and algal population data provided strong evidence for the hypothesis that the major source of many of these odour compounds was the phytoplankton. Total (intra+extracellular) geosmin concentration was strongly correlated with Anabaena abundance with no significant difference in geosmin production between sites. From the overall average of 10 fg geosmin cell−1 it is possible to predict that taste and odour problems, due to geosmin, may be experienced at Anabaena abundances of > 1,000-2,000 cells ml−1 in temperate Australian waters. β-cyclocitral concentration was correlated with Microcystis abundance at Carcoar Dam (10 fg β-cyclocitral cell−1), but with Anabaena sp. abundance at Hay Weir (2 fg cell−1).

New standards for the determination of geosmin and methylisoborneol in water by gas chromatography/mass spectrometry

Deuterium labelled geosmin and methylisoborneol (MIB) have been synthesized and evaluated as internal standards in the determination of geosmin and MIB in water by closed loop stripping followed by gas chromatography/mass spectrometry (GC/MS). The labelled standards were compared with chloroalkanes added as internal standards either at the time of sampling or immediately before closed loop stripping. When added at sampling time, the new standards enabled accurate determination of the geosmin and MIB present initially, even when the samples were analysed as much as 3 weeks later. The new standards gave better precision and accuracy than the chloroalkanes and overcame the underestimation of initial analyte concentration which usually results from losses of analyte through adsorption, volatilisation, biodegradation etc. during sample storage. Geosmin had a limit of detection of<0.1ng/l and 1 ng/lwas determined with a coefficient of variation (CV) of 1.2% (n = 5). MIB was determined at 1 ng/l with a CV of 3.5% (n = 5).

Quantification of the urea herbicide, diuron, in water by enzyme immunoassay.

Urea herbicides are widely applied to soil for total vegeta t ion control, or for preor postemergence treatment in crops. Uses include pre-plant treatment of fields in cotton, sugar cane, and vegetables; removal of annual weeds in citrus orchards; and for treatment of irrigation canal, road, and railroad rights of way. Several of the compounds are highly persistent in the environment; this can lead to damage to crops if contaminated water is used for irrigation and increase the possibility of unacceptable residues in drinking water. Diuron and related urea herbicides have rather simple chemical structures, being characterised by a substituted aryl moiety on one of the nitrogen atoms of urea, while two methyl groups are attached to the other urea nitrogen. Diuron has been one of the major urea herbicides in use since the 1950s. After simazine, it is the second most persistent herbicide in common agricultural practice (Hassall 1990). Its persistence in soil is due to a combination of three properties chemical stability, low aqueous solubility (EI-Dib and Aly 1976) and strong adsorption to soil (Kozak and Weber 1983; Alva and Singh 1990)o Urea herbicides can be difficult to detect instrumentally at low part-perbillion levels. HPLC of water extracts following concentration can typically detect down to only 0.5-1 ppb in water. While more sensitive gas-liquid chromatography (GC) methods have been developed, the low volatility of these compounds can lead to decomposition by use of high column temperatures before separation (Bowmer and Adeney 1978; Peterson and Batley 1991). A number of ELISAs for phenylurea herbicides, differing in the sensitivity and specificity for diuron, have been developed. These used either rabbit antisera (Newsome and Collins 1990, Liegeois et al. 1992; Schneider et al. 1994) or mouse monoclonal antibodies (Karu et al. 1994a). With the exception of analyses of groundwater samples using the monoclonal antibody assay (Karu et al. 1994b) these antibodies have only had limited application to water. We describe here an immunoassay for diuron based on use of sheep polyclonal antibodies to chlortoluron (Aherne 1991), and report the specificity and sensitivity properties of this assay and its application to detection of diuron in surface and sub-surface water.

Application of immunoassays for the herbicides, molinate and diuron, to field water analysis

Immunoassays based on microwells (for laboratory assay) and polystyrene tubes (for field assay) have been applied to the analysis of the herbicides, molinate and diuron, in field water samples. Development of a new immunoassay format for molinate, with detection limits of 0.5–1 ppb, enabled, for the first time, the direct analysis of molinate in water samples across the full range of usual field residue levels, without need for pre‐concen‐tration. A highly sensitive field assay for urea herbicides (diuron limit of detection of 0.15 ppb) has also been developed, based on a double‐layer coating with protein A and urea herbicide‐specific antibody. Each assay was only slightly affected by ions and turbidity, which are often problems in subsurface and surface water matrices respectively. For both formats of the molinate and diuron immunoassays, close correlations were obtained between herbicide levels determined by the immunoassay and by instrumental analysis, using field water samples.