RESUMEN
Although the effects of plastic residues on soil organic carbon (SOC) have been studied, variations in SOC and soil carbon-enzyme activities at different plant growth stages have been largely overlooked. There remains a knowledge gap on how various varieties of plastics affect SOC and carbon-enzyme activity dynamics during the different growing stages of plants. In this study, we conducted a mesocosm experiment under field conditions using low-density polyethylene and poly (butylene adipate-co-terephthalate) debris (LDPE-D and PBAT-D, 500-2000 µm (pieces), 0%, 0.05%, 0.1%, 0.2%, 0.5%, 1%, 2%), and low-density polyethylene microplastics (LDPE-M, 500-1000 µm (powder), 0%, 0.05%, 0.1%, 0.5%) to investigate SOC and C-enzyme activities (ß-xylosidase, cellobiohydrolase, ß-glucosidase) at the sowing, seedling, flowering and harvesting stages of soybean (Glycine Max). The results showed that SOC in the LDPE-D treatments significantly increased from the flowering to harvesting stage, by 12.69%-13.26% (p < 0.05), but significantly decreased in the 0.05% and 0.1% LDPE-M treatments from the sowing to seedling stage (p < 0.05). However, PBAT-D had no significant effect on SOC during the whole growing period. For C-enzyme activities, only LDPE-D treatments inhibited GH (17.22-38.56%), BG (46.7-66.53%) and CBH (13.19-23.16%), compared to treatment without plastic addition, from the flowering stage to harvesting stage. Meanwhile, C-enzyme activities and SOC responded nonmonotonically to plastic abundance and the impacts significantly varied among the growing stages, especially in treatments with PBAT-D (p < 0.05). These risks to soil organic carbon cycling are likely mediated by the effects of plastic contamination and degradation soil microbe. These effects are sensitive to plastic characteristics such as type, size, and shape, which, in turn, affect the biogeochemical and mechanical interactions involving plastic particles. Therefore, further research on the interactions between plastic degradation processes and the soil microbial community may provide better mechanistic understanding the effect of plastic contamination on soil organic carbon cycling.
RESUMEN
Intensive and widespread use of pesticides raises serious environmental and human health concerns. The presence and levels of 209 pesticide residues (active substances and transformation products) in 625 environmental samples (201 soil, 193 crop, 20 outdoor air, 115 indoor dust, 58 surface water, and 38 sediment samples) have been studied. The samples were collected during the 2021 growing season, across 10 study sites, covering the main European crops, and conventional and organic farming systems. We profiled the pesticide residues found in the different matrices using existing hazard classifications towards non-target organisms and humans. Combining monitoring data and hazard information, we developed an indicator for the prioritization of pesticides, which can support policy decisions and sustainable pesticide use transitions. Eighty-six percent of the samples had at least one residue above the respective limit of detection. One hundred residues were found in soil, 112 in water, 99 in sediments, 78 in crops, 76 in outdoor air, and 197 in indoor dust. The number, levels, and profile of residues varied between farming systems. Our results show that non-approved compounds still represent a significant part of environmental cocktails and should be accounted for in monitoring programs and risk assessments. The hazard profiles analysis confirms the dominance of compounds of low-moderate hazard and underscores the high hazard of some approved compounds and recurring "no data available" situations. Overall, our results support the idea that risk should be assessed in a mixture context, taking environmentally relevant mixtures into consideration. We have uncovered uncertainties and data gaps that should be addressed, as well as the policy implications at the EU approval status level. Our newly introduced indicator can help identify research priority areas, and act as a reference for targeted scenarios set forth in the Farm to Fork pesticide reduction goals.