Efficacy of urban road salt reduction strategies on public supply well quality

Long-term road salt application has increased chloride (Cl-) concentrations in public drinking water wells in many cold climate communities. A range of Best Management Practices (BMPs) have been adopted to mitigate the impact of road deicing compounds on groundwater quality. Chronic increases in chloride levels have been observed in several municipal well fields within the southern Ontario Regional Municipality of Waterloo (RMOW). In response, the RMOW and City of Kitchener implemented a plan to reduce salt application on roads by 25% within the local capture zones of one of the impacted well fields, the Greenbrook Well Field. Here the influence of salt reduction BMPs on subsurface water quality are examined by documenting changes in pore water Cl- concentrations and stored salt mass in vadose zone core samples collected at sites near the well field both before and after the implementation of the BMPs. The data indicate that ~6 years after salt reduction measures were initiated, average pore water Cl- concentration and average cumulative stored chloride mass in the vadose zone had decreased by approximately 60% and 40%, respectively. Groundwater samples collected from shallow monitoring wells installed at each field site showed similar post-BMP reductions in shallow groundwater Cl- concentration (~35%). Long-term (1973-2022) trends in raw water Cl- concentration data from the deeper public drinking water supply wells clearly demonstrate a slow, time-lagged response of the municipal supply wells to the salt reduction BMPs. The combined results suggest that controlled reductions in road salt applications within vulnerable, capture zone regions of public supply wells can reduce the impact of road salt deicing practices on municipal groundwater supplies over time.

Anti-malarial drug use among preschool children in an area of seasonal malaria transmission in Kenya

The aims of this study were to estimate the proportion of asymptomatic Kenyan preschool children using anti-malarial drugs, to identify factors associated with chloroquine use, and to assess the validity of frequency of febrile episodes and drug use reported by mothers or carers. Of 318 children studied, 38% (95% confidence interval [CI] = 30-47%]) tested positive for chloroquine or sulfadoxine. Of chloroquine-positive children, 15% had concentrations exceeding the estimated minimum therapeutically effective values. Among those testing negative for sulfadoxine, chloroquine-positive children were more frequently parasitemic (odds ratio = 2.6, 95% CI = 1.3-5.2), and had lower mean hemoglobin concentrations (6.1 g/L, 95% CI = 2.1-10.1) than chloroquine-negative children. Mothers over-reported the frequency of malaria or fever episodes as usually defined in medical studies, and underreported anti-malarial drug use. We conclude that anti-malarials are frequently given for treatment of malaria or malaria-associated illness, rather than prophylactically or for symptoms unrelated to malaria. Questionnaire surveys cannot replace biochemical markers to obtain information on anti-malarial drug use.

Liquid Chromatographic Determination of Bendiocarb in Technical Materials and Wettable Powder Formulations: Collaborative Study

A liquid chromatographic method for determination of bendiocarb in technical materials and wettable powders was tested by 12 collaborators. Bendiocarb is dissolved in acetonitrile containing 0.1% propiophenone as internal standard. This solution is analyzed on a liquid chromatograph utilizing a reverse phase (C18) column. The compound is detected at 254 nm and peak area is used for quantitation. The 3 different materials studied contained 20, 80, and nominally 100% bendiocarb. Each was examined in duplicate to provide the necessary matched pairs. Collaborators approved of the ease and simplicity of the method and, in particular, the way the method can be applied to automatic injection assemblies. The statistical data show acceptable precision of the method: Reproducibility coefficients of variation were 20% material, 2.04%; 80% material, 1.02%; and nominal 100% material (technical product), 0.64%. The method has been adopted official first action.

Gas Chromatographic Determination of Metribuzin in Formulations: Collaborative Study

A collaborative study was conducted on a gas chromatographic method for determining metribuzin. Two 75% dry flow able and two 42% liquid flowable formulations were analyzed by 18 laboratories. Formulations were extracted by shaking or ultrasonic mixing for 1-5 min with methylene chloride which contained di-n-butyl phthalate as an internal standard. The extracts were injected into a gas chromatograph equipped with an OV-225 column. Peak area ratios and peak height ratios showed no significant difference. The reproducibility coefficient of variation was 0.75% for the 75% formulation and 1.41% for the 42% formulation. This GC method has been adopted official first action.

Liquid Chromatography of Liquid Formulations Containing 2,4-D, Dicamba, and MCPP as Their Salts: Collaborative Study

A liquid chromatographic method for any liquid mixture of the 3 herbicides 2,4-D, MCPP, and dicamba, found in commercial formulations, has been collaboratively studied. Each collaborator received 4 samples, 3 of which were ternary formulations and one a binary formulation of amine salts. Concentrations in the formulations range from 0.02 to 2.32% for dicamba, 0.32 to 21.7% for 2,4-D, and 0.22 to 11.6% for MCPP. A binary solvent system and the use of a specified 25 cm column of RP 10 μm in the reverse phase ion suppression mode will selectively quantitate each herbicide, separating many impurities found in the technical products. Standard deviations in each of 11 columns of results obtained indicate good precision. The method has been adopted official first action.

Gas Chromatographic Determination of Fluazifop-butyl in Formulations: Collaborative Study

A method is described for the determination of butyl 2-(4-(5-trifluoromethyl- 2-pyridinyloxy)phenoxy) propanoate in technical and formulated material by gas chromatography (GC). Samples of technical or formulated material are dissolved in methylene chloride containing dibenzyl succinate as internal standard. The solution is injected into a gas chromatograph fitted with a flame ionization detector and a 6 ft × 2 mm glass column. The column is packed with 3% OV-17 on 100–120 mesh Chromosorb WHP and is maintained at 230°C. Peak areas obtained at the retention times of the internal standard and the active ingredient are measured with an integrator. The quantity of fluazifop-butyl is determined by comparing the internal standard and active ingredient peak areas with the peak areas obtained from a calibration solution containing known amounts of internal standard and pure active ingredient. Four samples were chosen for collaboration: technical fluazifop-butyl, a 4 lb/US gal. emulsifiable concentrate, a 560 g/L oil concentrate, and a 5% granular. Fourteen collaborators carried out replicate determinations on each sample. Coefficients of variation between laboratories were 0.80 for the technical, 0.88 for the emulsifiable concentrate, 1.03 for the oil concentrate, and 2.04 for the granular. Parallel peak height determinations showed substantially higher coefficients of variation for all except the granular sample. The method has been adopted official first action.

Liquid Chromatographic Determination of Propoxur in Technical and Formulated Products: Collaborative Study

A liquid chromatographic method for the determination of propoxur in technical and formulated products has been subjected to a collaborative study with 8 participating collaborators. Formulations are extracted with acetonitrile and analyzed by reverse phase chromatography, with n-butyrophenone as an internal standard. Collaborators were furnished with samples of technical, 70% wettable powder, 1.5 emulsifiable, and 2% bait. Coefficient of variation values obtained on the 4 samples were 0.34, 0.68, 3.25, and 5.41%, respectively. The method has been adopted official first action.

Liquid Chromatographic Assay for Dalapon Grasskiller Products: Collaborative Study

As a replacement for the present mercury reagent titration assay for dalapon grasskiller products, a liquid chromatographic method has been developed and collaboratively studied. The method separates the active ingredient, 2,2-dichloropropionic acid, from its related products by paired ion chromatography with UV detection at 214 nm. Statistical analysis of the data indicates that a single assay from one laboratory should not differ by more than 2.2% from the average assay of many laboratories, at the 95% confidence level, for products containing about 75% 2,2-dichloropropionic acid equivalent as the magnesium and/or sodium salt. The method has been adopted official first action.

High Pressure Liquid Chromatographic Determination of Brodifacoum in Formulations: Collaborative Study

A method is described for the determination of brodifacoum in technical and formulated material by high pressure liquid chromatography (HPLC). Samples of technical or formulation are dissolved in a solution of 1,3,5-triphenyl benzene in dichloromethane and methanol. The solution is injected into an HPLC system fitted with 25 cm Zorbax ODS column and an ultraviolet detector. The solution is eluted with a mixture of methanol, water, and acetic acid. Quantitative data are obtained by comparing peak areas of the compound and triphenyl benzene with those obtained by injecting a standard solution. Bait formulations are extracted into dichloromethane-formic acid, filtered, and concentrated by evaporation before chromatography. Nine collaborators made replicate determinations on 4 samples including technical material, a 0.1% powder, a 0.25% liquid, and a 0.005% pelleted bait formulation. They also carried out a recovery experiment on the bait product. Coefficient of variation (%) were 1.21 on the technical product, 13.49 on the powder, 2.40 on the liquid, and 11.06 on the bait. Insufficient data were generated to adequately quantitate the recovery factor. The method has been adopted official first action for the analysis of technical material, liquid, and bait formulations.

Gas-Liquid Chromatographic Method for the Analysis of Microencapsulated Diazinon Insecticide: Collaborative Study

The determination of diazinon insecticide in Knox Out 2FM formulation was studied collaboratively by 18 laboratories. Knox Out 2FM is a flowable microencapsulated insecticide formulation containing 23 wt% active ingredient. Analytical samples are first treated by grinding in a tissue grinder and then extracted in situ with acetonitrile. This preparative step breaks the capsules and allows the active ingredient to dissolve in the solvent. Single determinations on each of 2 closely matched samples were made by flame ionization gas-liquid chromatography. The standard deviation by analysts was 0.18 wt% and the coefficient of variation was 0.76%. The combined laboratory and analyst variation gave a standard deviation of 0.59 wt% and a coefficient of variation of 2.49%. The method has been adopted official first action.