**5. Conclusions**

Pesticides, fertilizers, herbicides, and animal waste are sources of contamination of groundwater of agricultural origin. These sources of agricultural pollution are very varied and numerous: spillage of fertilizers and pesticides during handling, runoff by loading and washing spray pesticides or other application equipment, and the use of chemicals up the slope and a few 100 meters of wells or well-feeding waters. Contamination can also occur when chemicals are stored in uncovered areas, which are not protected from wind and rain, or stored in places where groundwater flows from chemical storage to wells.

The movement of water in the soil is the main mechanism for the transfer of pollutants to surface and groundwater [25]. The physics of water in the soil and the movement of solutes can be used to determine the behavior of these materials.

The movement of solutes through the unsaturated, vadose zone is particularly important in relation to environmental and agronomic contamination [26].

The limited availability of data obtained from field studies represents the main limitation to assess the degree of contamination of groundwater against the effects of herbicide applications, especially in agricultural areas.

On the other hand, the scarcity of measurements makes it difficult to validate the mathematical models for determining the content of herbicides and fertilizers in groundwater and in the vadose zone. However, isolated data from groundwater in agricultural areas under the application of herbicides and fertilizers in recent years show that the waters of unconfined aquifers are contaminated by herbicides. In the medium and long term, this pollution will affect the environment in agricultural areas.

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To minimize the environmental damage caused by the application of herbicides, its application must be carried out taking into account, strictly, the conditions of the plants, the soil and the environment, as well as the doses and proper procedures for use, but this is not enough.

The current challenge is to advance in the knowledge of solute transport processes and determine the contamination that can be submitted if continued or continued with the current application methodologies and their concentrations.

But what is more important is that we must not forget that the purification possibilities of an aquifer are limited and that the best method of protection is, therefore, prevention. Do not contaminate; control sources of contamination to know the effects well and avoid contaminants.
