Assessment of water resource contamination by pesticides in vegetable-producing areas in Burkina Faso

This study proposes a comprehensive approach to investigate water resource contamination by pesticides under the specific climatic and hydrological conditions of the Sudano-Sahelian climate. Samples were collected from tradi- tional wells, boreholes, and a lake in Burkina Faso. A multiresidue analysis was developed for 25 pesticides identi- fied during field surveys. Polar organic chemical integrative samplers (POCIS) were used to confirm trends observed with grab samples. Uptake kinetics of POCIS were assessed by in situ calibration. The proposed use of nonlinear least squares regression proved to be a robust approach for estimating time- weighted average concentration in cases of nonlinear uptake. High sampling rates for triazines in a quasi-stagnant lake were attributed to warm water temperatures (30.8 ± 1.3 °C). The combination of sampling techniques during a 3-year monitor- ing period allowed for identifying potential interactions be- tween resources, seasonal patterns, and origins of contami- nants. Atrazine, azadirachtin, carbofuran, chlorpyrifos, cypermethrin, dieldrin, imidacloprid, and profenofos exceeded 0.1 μg L−1, indicating a potential risk for the con- sumers. Ecological risk assessment was performed using the Pesticide Tool Index for fish, cladocerans, and benthic inver- tebrates. Peak concentrations of cypermethrin and chlorpyri- fos were systematically associated with hazard to the studied taxa.

Pesticide application in gardening : assessment of resulting impact on water resources quality using grab samples and pocis, case study of Loumbila lake, Burkina Faso

Luiz Felippe De Alencastro, Morgan Fargues, Edouard René Gilbert Lehmann

This study proposes a comprehensive assessment of water resources contamination by pesticides in a gardening area. Multiresidue extraction procedure was developed to quantify 48 pesticides identified during field surveys. Drinking water samples were collected from traditional wells, boreholes and the lake. Levels of azadirachtin, chlorpyrifos, imidacloprid and profenofos in traditional wells exceed the threshold limit of 0.1 μg/l indicating a potential risk for the consumers. Residues of acetamiprid, atrazine, emamectin benzoate and imidacloprid were found in boreholes but in low concentrations. Levels in lake appeared to depend on seasons. Increase during the rainy season, in absence of gardening activity, suggests the contamination by other activities located upstream. In parallel, we conducted an in-situ calibration of Polar Organic Chemical Integrative Samplers (POCIS). Comparison with results from water samples shows that POCIS are suitable for measuring time weighted average concentration for atrazine and its metabolites, in environmental conditions of the study area.

2016

Stream temperature and discharge evolution in Switzerland over the last 50 years: annual and seasonal behaviour

Tristan Jonas Brauchli, Wolf Hendrik Huwald, Michael Lehning, Adrien Michel, Bettina Schaefli

Stream temperature and discharge are key hydro- logical variables for ecosystem and water resource management and are particularly sensitive to climate warming. Despite the wealth of meteorological and hydrological data, few studies have quantified observed stream temperature trends in the Alps. This study presents a detailed analysis of stream temperature and discharge in 52 catchments in Switzerland, a country covering a wide range of alpine and lowland hydrological regimes. The influence of discharge, precipitation, air temperature, and upstream lakes on stream temperatures and their temporal trends is analysed from multi-decadal to seasonal timescales. Stream temperature has significantly increased over the past 5 decades, with positive trends for all four seasons. The mean trends for the last 20 years are + 0.37 ± 0.11 ◦ C per decade for water temperature, resulting from the joint effects of trends in air temperature (+0.39 ± 0.14 ◦C per decade), discharge (−10.1 ± 4.6 % per decade), and precipitation (−9.3±3.4% per decade). For a longer time period (1979–2018), the trends are +0.33 ± 0.03 ◦ C per decade for water temperature, +0.46±0.03°C per decade for air temperature, −3.0 ± 0.5 % per decade for discharge, and −1.3 ± 0.5 % per decade for precipitation. Furthermore, we show that snow and glacier melt compensates for air temperature warming trends in a transient way in alpine streams. Lakes, on the contrary, have a strengthening effect on downstream water temperature trends at all elevations. Moreover, the identified stream temperature trends are shown to have critical impacts on ecological and economical temperature thresholds (the spread of fish diseases and the usage of water for industrial cooling), especially in lowland rivers, suggesting that these waterways are becoming more vulnerable to the increasing air temperature forcing. Resilient alpine rivers are expected to become more vulnerable to warming in the near future due to the expected reductions in snow- and glacier-melt inputs. A detailed mathematical framework along with the necessary source code are provided with this paper.

2020

Stream temperature and discharge evolution in Switzerland over the last 50 years: annual and seasonal behaviour

Tristan Jonas Brauchli, Wolf Hendrik Huwald, Michael Lehning, Adrien Michel, Bettina Schaefli

2020