Comparison of foliar spray and soil irrigation of biogenic CuO nanoparticles (NPs) on elemental uptake and accumulation in lettuce.

Nanoparticles (NPs) can be used in several ways in agriculture, including increasing production rates and improving nutritional values in plants. The present study aims to clarify how biogenic copper oxide nanoparticles (CuO NPs) applied by two routes of exposure (foliar spray and soil irrigation) affect the elemental uptake by lettuce. In vivo experiments using lettuce (n = 4) were performed with CuO NPs in comparison with copper salt (CuSO4), considering a final mass added of 20 mg of CuO per plant. The elemental composition of roots was mostly affected by the soil irrigation exposure for both Cu forms (NPs and salt). Neither Cu form added by soil irrigation was translocated to leaves. Copper concentration in leaves was mainly affected by foliar spray exposure for both Cu forms (NPs and salt). All Cu forms through foliar spray were sequestered in the leaves and no translocation to roots was observed. Foliar spray of CuO NPs caused no visual damage in leaves, resulted in less disturbance of elemental composition, and improved dry weight, number of leaves, CO2 assimilation, and the levels of K, Na, S, Ag, Cd, Cr, Cu, and Zn in leaves without causing significant changes in daily intake of most elements, except for Cu. Although Cu concentration increased in leaves by foliar spray of CuO NPs, it remained safe for consumption.

Effect of Amoxicillin on Nitrogen Oxidation Bacteria Present in Activated Sludge: Respirometry Investigation.

Amoxicillin (AMX) is one of the most widely used antibiotics in the world and its presence in wastewater is of great concern for its potential to bacteria selection. However, there is still a gap about the toxicity effect of AMX in nitrifier biomass from activated sludge (AS). This study is based on the implementation of respirometric tests in batches in order to evaluate the toxic effluent toxicity in the nitrification process of AS. The tests were conducted by comparing respiration rates with effluent containing ammonia nitrogen (NH4+-N) and nitrite nitrogen (NO2--N) called "reference" and batches containing toxic effluent doped with different concentrations of AMX here called "process." Results with effluent containing concentrations greater than 100 mg L-1 showed that AMX negatively affected the specific growth rate (µm) of ammonia-oxidizing bacteria (AOB) (from 0.50 d-1 to 0.13 d-1) and nitrite-oxidizing bacteria (NOB) (from 0.64 d-1 to 0.15 d-1). Although there is no total inhibition of populations, these µm values are limiting for a feasible development of the nitrification process in AS systems. The removal of AMX decreased from 99 to 37% (liquid phase) when the concentration of AMX increased (20 mg L-1 to 200 mg L-1). A decrease in the microbial community AOB and NOB was observed through fluorescent in situ hybridization (FISH), corroborating the results of respirometry. In summary, the study showed that the inhibition of the AS nitrification process occurs in the presence of high concentrations of AMX and the most susceptible group are the NOB.

Effects of copper oxide nanoparticles on growth of lettuce (Lactuca sativa L.) seedlings and possible implications of nitric oxide in their antioxidative defense.

Copper oxide nanoparticles (CuO NPs) have been extensively explored for use in agriculture. Previous studies have indicated that application of CuO NPs might be promising for development and conservation of plants, pest control, and for the recovery of degraded soils. However, depending on the applied concentration copper can cause phytotoxic effects. In this work, biosynthesized CuO NPs (using green tea extract) were evaluated on their effects on lettuce (Lactuca sativa L.) seedling growth, which were exposed at concentrations ranged between 0.2 and 300 µg mL-1. From the biosynthesized were obtained ultra-small CuO NPs (~ 6.6 nm), with high stability in aqueous suspension. Toxicity bioassays have shown that at low concentrations (up to 40 µg mL-1), CuO NPs did not affect or even enhanced the seed germination. At higher concentrations (higher than 40 µg mL-1), inhibition of seed germination and radicle growth ranging from 35 to 75% was observed. With the increase of CuO NPs concentrations, nitrite and S-nitrosothiols levels in radicles increased, whereas superoxide dismutase and total antioxidant activities decreased. The nitrite and S-nitrosothiols levels in lettuce radicles showed a direct dose response to CuO NP application, which may indicate nitric oxide-dependent signaling pathways in the plant responses. Therefore, the results demonstrated that at low concentrations (≤ 20 µg mL-1) of CuO NPs, beneficial effects are obtained from seedlings, enhancing plant growth, and the involvement of nitric oxide signaling in the phytotoxic effects induced by high concentration of this formulation. Graphical abstract.