Herbicides and Environment

MONTAGNA STAIB, CRISTINA MÓNICA; PECHEN DE D`ANGELO, ANA MARÍA; ANDRES VENTURINO,

InTech

Lugar: Rijeka; Año: 2011 p. 16

978-953-307-476-4

Submersed weeds on irrigation systems reduces water delivery capacity, clogs pumps and structures, ruptures canals, increases leakages and loss of water, increases water costs, etc. Herbicides are a commonly used procedure to control submersed weeds in irrigation canals because of its practicability, efficacy and cost. Acrolein, currently registered under the trade name MAGNACIDE® H by Baker Petrolite Corporation, has been used for many years in Argentina. Acrolein is a cell toxicant that reacts with several molecules containing sulfhydryl groups, including proteins, exerting direct cytotoxic effects or interrupting cell signalling pathways. Acrolein is acutely toxic to aquatic organisms. There are no generally accepted quantitative criteria for evaluating ecological significance and expert judgement is always required. We have shown here evidences from literature data and from risk assessment with native species that acrolein used for weed control in irrigation canals is extremely toxic for most of the living organisms at the recommended treatment concentrations and conditions. Nevertheless, its presence in the canals is transient and it has been observed a natural recovery process, mainly operating through the introduction of species from outside the treated area that minimizes the ecological risk. Populations of species with a high intrinsic rate of increase, such as zooplankton, may rapidly recover after an acute toxicity event. Species with lower intrinsic rate of growth rate, such as amphibians and fish will require longer periods for recovery of populations. One advantage in the protection of higher organisms such as birds and mammals is the irritating odour of the herbicide. The odour prevents them from getting close to the treated area, so these species are not endangered by the compound. Taking into account the fact that most population effects of the use of acrolein as an aquatic herbicide are temporary, we conclude that this use is ecologically acceptable because recovery occurs within a reasonable period of time. In order to minimize the risk on the ecological receptors, a strict control on the treatment regime, concentration applied, timing and frequency of application must be ensured. Treated channels must be controlled during the treatments, water release must be prevented until the product has dissipated, and it must be ensured that water is used only for irrigation purposes.