ABSTRACT
El herbicida ácido 2,4 - diclorofenoxiacético (2,4-D) es un ácido selectivo y sistémico que, desde 1940, es ampliamente utilizado en suelo agrícolas, de todo el mundo. Su uso radica a su selectividad entre la vegetación de hoja ancha y cultivos de gramíneas y como regulador del crecimiento vegetal; sin embargo, este herbicida se puede acumular en el ambiente y, adicionalmente, puede ser transportado por lixiviación, a través del suelo, llegando a contaminar aguas subterráneas, lo que genera un alto riesgo para el ambiente y la salud del ser humano. El estudio de la movilidad del 2,4-D en suelos con alto contenido de materia orgánica permitió conocer, que no solo la materia orgánica se correlaciona indirectamente con la movilidad de este compuesto, sino que, también, influye la humedad, al reducir la lixiviación y el potencial de contaminación del recurso hídrico subterráneo, mientras que la conductividad hidráulica se relaciona, de manera directa, con la lixiviación de este herbicida.
The herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) is a selective and systemic acid that has been widely used in agricultural soils since 1940. Its use lies in its selectivity between broadleaf vegetation and grass crops, and as a regulator of plant growth. However, this herbicide can accumulate in the environment, and additionally, it can be transported by leaching through the soil, contaminating groundwater, which generates a high risk for the environment and human health. In this study, the mobility of 2,4-D in organic-matter-rich soils was assessed. The results revealed that not only the organic material is indirectly correlated with the mobility of this compound but also influences humidity and reduces leaching and potential pollution of groundwater resources, whereas hydraulic conductivity is directly related to herbicide leaching.
ABSTRACT
Although FEV, improvement is routinely used to define bronchodilator (BD) response, it correlates poorly with clinical effects. Changes in lung volumes (LV) have shown better correlation with exercise tolerance and might be more sensitive to detect BD effects. We assessed the additional contribution of measuring LV before and after BD to detect acute improvement in lung function not demonstrated by FEV, and the influence of the response criteria selected on this contribution. We analyzed 98 spirometries and plethismographies performed pre and post BD in patients with airflow obstruction (FEV,/FVC < 70%). BD response was defined for FEV, and FVC as per ATS guidelines and for other LV as o>_10% of baseline (4>_5 and >_15% were also analyzed). FEV, identified as responders 32% of patients. Greater proportions were uncovered by slow vital capacity (51 %, p<0.001), inspiratory capacity (43%, p<0.05) and residual volume (54%, p<0.001). Slow spirometry identified 11% of responders additional to those detected by FEV, and FVC. Plethismography added 9% more. The magnitude of volume responses correlated with the degree of baseline yperinflation. Percentages of responders varied greatly using different thresholds (A>5 and >_15%). Mean change and proportions of responders for each LV varied significantly (p<0.05) whether change was expressed as percent of baseline or predicted values. A considerable proportion of patients with airflow obstruction shows acute response to bronchodilato rs identified by changes in lung volumes but not detected by an improvement in FEV, The selection of LV response criteria has important influence on the magnitude of this additional detectìon.