A dynamic model for uptake of pesticides in potatoes is presented and evaluated with measurements performed within a field trial in the region of Boyacá, Colombia. The model takes into account the time between pesticide applications and harvest, the time between harvest and consumption, the amount of spray deposition on soil surface, mobility and degradation of pesticide in soil, diffusive uptake and persistence due to crop growth and metabolism in plant material, and loss due to food processing. Food processing steps included were cleaning, washing, storing, and cooking. Pesticide concentrations were measured periodically in soil and potato samples from the beginning of tuber formation until harvest. The model was able to predict the magnitude and temporal profile of the experimentally derived pesticide concentrations well, with all measurements falling within the 90% confidence interval. The fraction of chlorpyrifos applied on the field during plant cultivation that eventually is ingested by the consumer is on average 10(-4)-10(-7), depending on the time between pesticide application and ingestion and the processing step considered.

A variety of plant-based materials can be used in innovative methods to treat water pollution through bio-adsorption. This work evaluated, under lab conditions, the presence of native microorganisms in orange peel (OP) and elodea (Egeria densa, ELO), the aerobic degradation and biostability of the bio-adsorbents, and the contribution of microorganisms to the bio-adsorption of Pb (II) and Cr (III). The microbial characterization and biostability of OP and ELO were conducted using 2 g of dried bio-adsorbent and a solution of the metallic ions at 450 mg/L. ELO had a larger number of bacteria, fungi, and yeast than OP. After 2 hours of contact with a 450 mg/L Pb (II) and Cr (III) solution, this value decreased by 80-86% in both bio-adsorbents. After 25 days, the microorganisms showed adaptation to the Pb (II) and Cr (III) concentrations. According to the bio-degradation test, OP had a stability of over 7,01 months, while that of ELO was 2,61 months, with a CO2 value of 1 439,9 mg after 46 days of incubation. The microorganisms tolerated a high metal concentration, but they did not contribute significantly to Cr (III) bio-adsorption in ELO. The microorganisms present in the adsorbents affect the stability of the materials, as the bio-adsorbents provide a nutrient-rich substrate. OP had higher bio-stability and could be used in pilot tests for the treatment of metal-polluted water.