Photodegradation of glyphosate in water and stimulation of by-products on algae growth

Glyphosate is the most widely used herbicide in global agricultural cultivation. However, little is known about the environmental risks associated with its migration and transformation. We conducted light irradiation experiments to study the dynamics and mechanism of photodegradation of glyphosate in ditches, ponds and lakes, and evaluated the effect of glyphosate photodegradation on algae growth through algae culture experiments. Our results showed that glyphosate in ditches, ponds and lakes could undergo photochemical degradation under sunlight irradiation with the production of phosphate, and the photodegradation rate of glyphosate in ditches could reach 86% after 96 h under sunlight irradiation. Hydroxyl radicals (•OH) was the main reactive oxygen species (ROS) for glyphosate photodegradation, and its steady-state concentrations in ditches, ponds and lakes were 6.22 × 10−17, 4.73 × 10−17, and 4.90 × 10−17 M. The fluorescence emission-excitation matrix (EEM) and other technologies further indicated that the humus components in dissolved organic matter (DOM) and nitrite were the main photosensitive substances producing •OH. In addition, the phosphate generated by glyphosate photodegradation could greatly promote the growth of Microcystis aeruginosa, thereby increasing the risk of eutrophication. Thus, glyphosate should be scientifically and reasonably applied to avoid environmental risks

Fate and Phytotoxicity of CeO₂ Nanoparticles on Lettuce Cultured in the Potting Soil Environment

<div><p>Cerium oxide nanoparticles (CeO₂ NPs) have been shown to have significant interactions in plants. Previous study reported the specific-species phytotoxicity of CeO₂ NPs by lettuce (<i>Lactuca sativa</i>), but their physiological impacts and vivo biotransformation are not yet well understood, especially in relative realistic environment. Butterhead lettuce were germinated and grown in potting soil for 30 days cultivation with treatments of 0, 50, 100, 1000 mg CeO₂ NPs per kg soil. Results showed that lettuce in 100 mg·kg^-1 treated groups grew significantly faster than others, but significantly increased nitrate content. The lower concentrations treatment had no impact on plant growth, compared with the control. However, the higher concentration treatment significantly deterred plant growth and biomass production. The stress response of lettuce plants, such as Superoxide dismutase (SOD), Peroxidase (POD), Malondialdehyde(MDA) activity was disrupted by 1000 mg·kg^-1 CeO₂ NPs treatment. In addition, the presence of Ce (III) in the roots of butterhead lettuce explained the reason of CeO₂ NPs phytotoxicity. These findings demonstrate CeO₂ NPs modification of nutritional quality, antioxidant defense system, the possible transfer into the food chain and biotransformation in vivo.</p></div

(A) Ce contents in roots (A) and leaves (B) of lettuce plants.

<p>Error bars stand for standard errors. Bar with the same letters show no statistically significant differences at p≤0.05. n = 8.</p

XANES Ce LIII-edge spectra (5723 eV) in roots of butterhead lettuce treated with CeO₂ NPs.

<p>The dotted line indicates the feature a, b and c.</p

NO_3^--N (A) and soluble sugar (B) contents content in the leaves Error bars stand for standard errors.

<p>Bar with this asterisk (*) symbol shows statistically significant differences at <i>p</i>≤0.05, n = 8.</p

(A) Root and shoot fresh biomass of lettuce plants grown for 30 days in potting soil, treated with 0 (control)-1000 mg·kg^-1 CeO₂ NPs. (B) Root and shoot dry biomass of lettuce plants grown for 30 days in potting soil treated with 0 (control)-1000 mg·kg^-1 CeO₂ NPs.

<p>Error bars stand for standard errors. Bar with this asterisk (*) symbol shows statistically significant differences at p≤0.05. n = 8.</p

SOD and POD activities and MDA levels in the roots and shoots of of lettuce plants

<p>Error bars stand for standard errors. Bar with this asterisk (*) symbol shows statistically significant differences at <i>p</i>≤0.05.</p