DOI: 10.5285/e28ffc01-880d-423f-acb6-879b9fd4603a
title: Micro-organic herbicides data from rivers [LOIS]

description: Micro-organic herbicide levels in river water for various sites within the Humber and Tweed catchments collected as part of the Land Ocean Interaction Study project (LOIS). The dataset contains data for Phenyl urea and Phenoxy acid herbicides, measured as 2,4-Dichlorophenoxyacetic acid, 4-(4-Chloro-O-tolyloxy) butyric acid, 4-Chloro-O-tolyloxyacetic acid, Chlorotoluron dissolved, Diuron dissolved, Isoproturon dissolved, Linuron dissolved, Mecoprop dissolved. Phenyl urea herbicide data is available for twelve sites in the Humber catchment within 1994 to 1995 and 1994 to 1997 and for three sites on the Tweed catchment within 1995. Phenoxy acid herbicide data is available for six sites (S1, U3, N4, W5 and O6) over the period December 1994 to September 1995, for 7 sites (S2, D7, A8, C9, D10, T11 and O12) over the period December 1994 to February 1997 and 3 sites (TW13, TW14 and TW15) over the period January 1995 to September 1995. Attempts were made to sample the sites at weekly intervals. However sampling was halted for short periods when it was not possible to process the samples quickly. Linuron dissolved was only measured from April 1994 - October 1994. Samples were collected in chromic acid-washed 1 litre glass bottles. Herbicide levels were concentrated before being measured using High Performance Liquid Chromatography for Phenyl urea herbicides and Gas Chromatography for Phenoxy acid herbicides. Until November 1994, analysis was completed by the York University and the Institute for Freshwater Ecology, Wareham, laboratories. From December 1994 onwards the samples were dispatched to the Institute for Hydrology, Wallingford, for extraction and analyses.
description: Phenyl urea herbicides were concentrated by using one of the following methods: solid phase extraction (SPE) using C18 (1gm, 6ml) (EC) (ISOLUTE) cartridges and eluting with ethyl acetate; as previous method except that the dried cartridge after loading was washed with 6ml of methanol: water:: 1:1 (to remove the impurities) before eluting the herbicides with methanol; liquid-liquid extraction with dichloromethane. Phenoxy acid herbicides were concentrated using liquid-liquid extraction with dichloromethane. Phenyl urea herbicides were measured by High Performance Liquid Chromatography (HPLC) with detection by a UV/VIS detector and phenoxy acid herbicides by Gas Chromatography (GC) with detection by a mass selective detector (GS-MS). One sample from each batch was randomly spiked with a mixed standard of urea and acid herbicides for comparison purposes. For all determinands certified grade standards of purity >99% were used. The laboratory at Wallingford takes part in WRC's AQUACHECK inter-laboratory harmonisation exercise for urea and acid herbicides. Data quality for both groups of herbicides is variable because of the nature of samples (Aire, Calder, Don and Trent were found to be highly polluted resulting in complex chromatograms), the level of herbicides present (mostly they are close to the detection limit) and difficulties in extraction especially in liquid-liquid extraction where they formed emulsions. A zip file of box-and-whisker plots are available for each determinand, showing the range of values (median, inter-quartile range, 1.5 * inter-quartile range, outliers) recorded at each site to enable prospective users to understand data quality.