Contamination risk by heavy metals and enzymatic stoichiometry in agricultural soils under intense use of pesticides.

Soil contamination by heavy metals (HM) from pesticides poses a serious environmental threat, affecting sustainability and agricultural productivity. Soil enzymes are essential for biochemical reactions such as organic matter decomposition and nutrient cycling and are vital for maintaining soil health. However, the effects of HM on soil enzyme activity are not yet well understood. This study examined the impact of HM contamination on enzymatic stoichiometry in regions with intensive pesticide use. We selected flower cultivation areas with 5 years (CA1) and 10 years (CA2) of pesticide exposure and a native forest area (NFA) as a reference during the dry and rainy seasons. We measured Cd, Cu, Mn, Pb, and Zn levels and employed ecological risk indices to assess contamination levels. We also analyzed enzyme activities (arylsulfatase, ß-glucosidase, acid phosphatase, urease) and enzymatic stoichiometry. CA2 exhibited the highest concentrations of Cd, Cu, and Mn in both periods, while Zn was highest in both CA1 and CA2. CA2 had higher values for all indices, indicating significant contamination. Compared with NFA, arylsulfatase activity was lower in cultivated areas during both periods, suggesting decreased soil quality. We found negative correlations between Cu, Mn, Zn, and arylsulfatase, as well as a reduction in urease with Cd; these elements also increased microbial C limitation. Our findings show that continuous pesticide input increases HM levels and that enzyme activity and stoichiometry are effective bioindicator of soil contamination. This study underscores the urgent need for guidelines to protect soils from prolonged HM buildup.

Study of the correlation between Covid-19 cases and deaths and basic sanitation in Brazil: Is this a possible secondary route of virus transmission?

People with COVID-19 may excrete viable SARS-CoV-2 virus through urine and faeces, which has raised concerns about the possibility of transmission of COVID-19 via water contaminated or sewage. These concerns are especially exacerbated in underdeveloped countries like Brazil, where untreated sewage is usually discharged to surface water or soil. Because of that, a hypothesis emerged that was addressed in this study, which seeks to understand whether access to basic sanitation services can influence the proliferation of the virus. A correlation study was carried out between the cases of COVID-19 and the indicators of basic sanitation from all regions of Brazil. The results showed that there was a correlation only with the water supply indicator. A hypothesis that would explain the presented correlation would be the inefficiency of the water treatment systems in Brazil, not totally inactivating the virus, or possible contamination of the water distribution networks by sanitary sewage. In general, the data presented reinforce the need to expand and monitor basic sanitation services, especially to ensure the effective and efficient disinfection of drinking water. This monitoring could be useful for early warning surveillance of the spread of the virus.