Climate change 2014 - Synthesis Report

Impacts of climate change on surface water quality in relation to drinking water production.

Remote sensing for agricultural applications: A meta-review

s should clearly state the purpose, brief statement of procedure, results and conclusions. Please include your name, full address and topic on all submissions. At least one author of each abstract should register for the conference. All accepted abstracts will be published as symposium proceedings. Additionally, commended abstracts may be published in a journal after they are expanded to a manuscript followed by extensive reviewing. The language of the conference will be English.

An international symposium

http://www.nurserycropscience.info/water/managing-runoff/technical-pubs/reichenberger-et-al.-2007.-mitigation-strategies-to-reduce-pesticide-inputs-into-ground-and-surface-water-and-their-effectiveness-a-review

Mitigation strategies to reduce pesticide inputs into ground- and surface water and their effectiveness; A review

The assessment of field-like sorption behaviour is critical to predict the fate and transport of organic compounds, especially when long time periods are considered. We compared field-derived sorption isotherms for diuron from a 4-year database collected in a Mediterranean catchment with adsorption and desorption isotherms from classical batch studies. In addition, a new technique of drying the slurry samples in-between various desorption steps was applied in order to reflect the recurrent drying of the topsoil under Mediterranean climate conditions. Our results show first that the field-derived isotherms indicated a larger sorption capacity of the soil at small diuron concentrations (larger Kf and smaller exponent for the Freundlich parameters) than those derived from standard batch experiments. Second, when the soil was dried before desorption, chemical release was reduced by up to 29% as compared with normal desorption, resulting in isotherms that were in line with results from the field experiment. These results suggest that the drying-wetting cycles are a key factor in the long-term adsorption and desorption processes under field conditions. Third, the new approach of batch desorption experiments that allow the fast and careful complete drying of soil suspensions appears to be an appropriate method to assess sorption behaviour of herbicides over a long time period.

https://hal.archives-ouvertes.fr/hal-00886270/document

Sorption behaviour of diuron under a mediterranean climate

The variation in the availability of diuron to transport by overland flow was studied in a vineyard field under a Mediterranean climate during three years. The availability of diuron decreased with time due to the dissipation of diuron in the topsoil and the decrease of its accessibility by runoff water, which is not represented in pesticide transfer modelling. Thus, calculated concentrations of diuron with simple and actual relations are always greater than those measured in the overland flow.

Dynamique de la mobilisation et du transfert du diuron par ruissellement

The contamination of soil and runoff water by diuron was monitored over several years at the field and the catchment level in a Mediterranean vineyard zone Several aspects of pesticide behaviour in semiarid environments were observed Pesticide dissipation in the soil was largely influenced by periods of drought, and large temporal changes in pesticide desorption properties occurred The main pathway of pesticide losses at the field scale was the intense overland flow generated by heavy Mediterranean rainfalls Soil treatment had a major influence on herbicide losses Conventional tillage limited the contamination of surface waters in comparison to no-tillage, since it increased infiltration and restricted the use of herbicides At the catchment scale the concentrations in pesticides of surface waters were similar to those at the field scale, due to the dominant Hortonian behaviour of the catchment However, over a season the pesticide losses by runoff water were much smaller at the catchment scale because of important channel losses

Processes of pesticide dissipation and water transport in a Mediterranean farmed catchment

Temporal Variation In The Availability of Diuron To Transport By Overland Flow

The availability of pesticides in the soil is one of the factors that determine their mobilization and transport in runoff and groundwaters. In this paper, we aim to better understand the change in pesticide availability with increasing residence time in the soil. The relative contributions of degradation and sorption to the overall fate of molecules were examined, as was the remobilization of residues from the topsoil in water. The experiment was undertaken in undisturbed soil micro-lysimeters under natural climatic conditions for 1 year. We applied 14 C-diuron to the soil surface to trace its residues in water-extractable (W), methanol-only-extractable (MO) and non-extractable (N) fractions and in runoff waters. Mass-balance calculations were fitted to the observed data to determine the quantities degraded or transferred within and between each of the compartments studied. Losses of diuron residues in runoff declined exponentially from 473 to 4 μg l -1 in 1 year. After 80 days, sorption of diuron residues in the soil was significant, as was degradation in the W and MO pools. Losses in runoff were small because of sparse rainfall. The following 140 days corresponded to a humid period with increased degradation in both W and MO pools. A redistribution from the MO towards the W pool occurred, probably because of intense rainfall at that time, leading to an apparent desorption of diuron residues. This was the most important result, suggesting that ageing processes should not be considered irreversible over time. The last phase of change, which occurred during winter, was slow. Leaching processes appeared to be of minor importance for diuron, with the surface layer containing more than 84% of diuron residues.

Xavier Louchart

Papers

Sorption behaviour of diuron under a mediterranean climate

Dynamique de la mobilisation et du transfert du diuron par ruissellement

Processes of pesticide dissipation and water transport in a Mediterranean farmed catchment

Temporal Variation In The Availability of Diuron To Transport By Overland Flow

Evidence of the role of climate control and reversible aging processes in the fate of diuron in a Mediterranean topsoil