Factors Influencing the Development and Accumulation of Heavy Metals in Hop Plants Grown in Tropical Regions

The aim of this study was to evaluate heavy metal contamination in an area of Humulus lupulus L. production, as well as to identify the main factors that help enrich the soil and plants with these elements. The study was conducted in one of the largest hop-producing properties in Brazil, located in a mountain agroecosystem. Samples of soil and plant tissue were collected at 42 points throughout the study area. Soil fertility and particle size were analyzed, in addition to determining the levels of heavy metals in the samples using acid digestion, as per EPA methods 3050 and 3050B. This was followed by atomic absorption spectrometry. The Pollution Index (PI) was then calculated, based on the results. The relationship between the variables was investigated using principal component analysis (PCA) and cluster analysis. Cadmium (Cd) was the only element that showed moderate to severe enrichment in the soil. The terrain, parent material and management practices adopted on the property had a significant influence on the enrichment of metals in both the soil and the plants, as well as impacting hop productivity. These factors were therefore mainly responsible for the transfer and accumulation of metals in the plants. Despite this, the levels of metals detected in hop inflorescences show no risk of being transferred to derivative products, such as beer.