Influences of sampling methodologies on pesticide-residue detection in stream water.

Traditional grab sampling (GS) used widely in the study of water quality has been found lacking in spatial and temporal resolution for pesticide residue monitoring in stream water. The objectives of this article are to present a hydrograph-based sampling approach and compare it with traditional GS according to sensitivity at temporal and spatial scales and maximum concentrations of pesticide residues detected in-stream. Data collected from streams receiving water from three nested watersheds located in northwestern New Brunswick, Canada, were used in this study. The results showed that the hydrograph-based sampling method detected 20 to 30 % more pesticide cases than GS for rainfall events causing runoff. Grab sampling significantly underestimated average concentrations of pesticide residues by 50 % and maximum concentrations by 1 to 3 orders of magnitude. Using a modified sampler design, the spatial and temporal variability of pesticide residues was more accurately captured by hydrograph-based sampling, and therefore its use in monitoring programs is recommended.

Pesticide application and detection in variable agricultural intensity watersheds and their river systems in the maritime region of Canada.

Applications of pesticides in areas of agricultural production have been an environmental concern for the past several decades. Varying-sized watersheds draining regions of intense agriculture in the Maritime Provinces of Canada were monitored between 2003 and 2007 to determine the major in-use pesticides and to gain an understanding of the risks posed to aquatic ecosystems. A questionnaire collected from farmers in one watershed intensively cropped with potato indicated that 43 pesticides were applied with 18 of them being detected in that watershed. Our results across the Maritime region suggested that detection frequencies ranged from 0.0 to 22 % during the study period. Chlorothalonil, linuron, metalaxyl, and metribuzin were detected in 17-22 % of samples collected during rainfall events every year. Other pesticides, such as azinphos-methyl, atrazine, cypermethrin, permethrin, fonofos, and ß-endosulfan were detected in ≤17 % of the samples during some years of the study. Concentrations of several pesticides were found to exceed their Canadian Council of Ministers of the Environment (CCME) aquatic life water-quality guidelines in pulses after rain events. The highest proportion of detections exceeding a CCME guideline was for chlorothalonil at 12.9 %, ß-endosulfan at 6.0 %, and linuron at 3.4 %. Despite indications that remedial measures offer protection to aquatic environments, spatial and temporal gaps in the data prevented a full evaluation. A dedicated long-term multiple-watershed monitoring program for this region of Canada is therefore recommended.

Field performance of nine soil water content sensors on a sandy loam soil in new brunswick, maritime region, Canada.

An in situ field test on nine commonly-used soil water sensors was carried out in a sandy loam soil located in the Potato Research Center, Fredericton, NB (Canada) using the gravimetric method as a reference. The results showed that among the tested sensors, regardless of installation depths and soil water regimes, CS615, Trase, and Troxler performed the best with the factory calibrations, with a relative root mean square error (RRMSE) of 15.78, 16.93, and 17.65%, and a r(2) of 0.75, 0.77, and 0.65, respectively. TRIME, Moisture Point (MP917), and Gopher performed slightly worse with the factory calibrations, with a RRMSE of 45.76, 26.57, and 20.41%, and a r(2) of 0.65, 0.72, and 0.78, respectively, while the Gypsum, WaterMark, and Netafim showed a frequent need for calibration in the application in this region.

Validating Evapotranspiraiton Equations Using Bowen Ratio in New Brunswick, Maritime, Canada.

Three methods including the Penman-Monteith (PM), Priestley-Taylor (PT), and 1963 Penman equation (PE) for calculating daily reference evapotranspiration (ETo) were evaluated in the Maritime region of Canada with the data collected from 2004 to 2007. An automatically operated meteorological station located on the Potato Research Centre, Agriculture and Agri-Food Canada, Fredericton, New Brunswick, Canada, was used to collect required meteorological data for evapotranspiration modeling. A Bowen Ratio system (BR) was setup near the Environment Canada grade one weather station to provide evapotranspiration observations for the validation research of reference evapotranspiration models. The results showed that the prediction from each of the tested models had a certain degree of offset in comparison with the observations obtained by the BR method. All of the tested models slightly overestimated evapotranspiration compared to the BR system by 5-14%, depending on the method. However, the PM generated a better fit to the pooled dataset while the PT produced the best prediction for the 2007 validation dataset. The PM generated the best estimation of evapotranspiration for year 2004 during a inter-annual comparison. The BR revealed that the average daytime ET for the site was around 2.5 mm day-1(±0.1) averaged for Julian day 157-276 in 2004 to 2006 and possible condensation was 0.16 mm day-1 for the same period. Crop coefficient (Kc) varied with different models, for example, 0.42 for the PM, 0.44 for the PT, and 0.67 for the PE with a slight yearly variation. With this set of Kc values, a validation with additional dataset collected in 2007 indicated that all three equations achieved a good fit with observations using the above Kc values. The PT performed slightly better than the other two models. A single factor analysis did not show any statistically significant difference between predicted and measured ET. With a consideration of simplicity and application for scaling up to landscape, this research suggested that the PT is the preferable method for estimating ET values in this region.