RESUMO
Both selenium (Se) and gibberellins (GA3) can alleviate cadmium (Cd) toxicity in plants. However, the application of Se and GA3 as foliar spray to against Cd stress on soybean and its related mechanisms have been poorly explored. Herein, this experiment evaluated the effects of Se and GA3 alone and combined application on soybean rhizosphere microenvironment, Cd accumulation and growth of soybean seedlings. The results revealed that both Se and GA3 can effectively decrease the accumulation of Cd in soybean seedlings. Foliar application of Se, GA3 and their combination reduced Cd contents in soybean seedlings respectively by 21.70 %, 27.53 % and 45.07 % when compared with the control treatment, suggest a synergistic effect of Se and GA3 in decreasing Cd accumulation. Se and GA3 also significantly increased diversity and abundance of the metabolites in rhizosphere, which consequently played an important role in shaping rhizosphere bacteria community and improve rhizosphere soil physicochemical properties of Cd contaminated soil, as well as decreased the Cd available forms contents but enhance the immobilized form levels. Overall, this study affords a novel approach on mitigating Cd accumulation in soybean seedlings which is attributed to Se and GA3 regulated interplay among rhizosphere soil metabolites, bacteria community and cadmium speciation.
RESUMO
Industrial emissions play a major role in the global methane budget. The Permian basin is thought to be responsible for almost half of the methane emissions from all U.S. oil- and gas-producing regions, but little is known about individual contributors, a prerequisite for mitigation. We use a new class of satellite measurements acquired during several days in 2019 and 2020 to perform the first regional-scale and high-resolution survey of methane sources in the Permian. We find an unexpectedly large number of extreme point sources (37 plumes with emission rates >500 kg hour-1), which account for a range between 31 and 53% of the estimated emissions in the sampled area. Our analysis reveals that new facilities are major emitters in the area, often due to inefficient flaring operations (20% of detections). These results put current practices into question and are relevant to guide emission reduction efforts.
RESUMO
Soil genesis is important for ecological restoration of red mud disposal area. Soil genesis of red mud and the microbial mechanism were studied by analyzing the change of physicochemical and biochemical characteristics of red mud. We analyzed the microbial community structure in a red mud disposal area without any human-induced restoration through a space for time substitution approach. The results showed that, with the increases of storage time, the physical parameters of porosity, water-stable aggregates content, and mean weight diameter increased, but the bulk density decreased. The chemical parameters, including pH, electrical conductivity, acid neutralizing capacity, and exchangeable sodium percentage, decreased with increasing storage time. The bio-chemical parameters of total organic carbon, total nitrogen, available phosphorus, microbial biomass carbon and basal respiration increased, but the metabolic quotient decreased. The Shannon diversity index increased, and the dominant microflora in red mud changed from the oxygenic photosynthetic bacteria Cyanobacteria and thanaerobic anoxygenic phototrophic bacteria Chlorobi and Chloroflexi to Proteobacteria, Actinobacteria and Firmicutes. The ratio between eutrophic and oligotrophic bacteria substantially increased. The micromorphology results showed that the microorga-nism-red mud aggregates were formed through adsorption, linkage, intertwinement and package between red mud particles, microbial cells and their metabolites. The red mud biotope changed spontaneously from extreme and oligotrophic into soil-like under natural stockpiling. The soil genesis process was mediated by microbes through increasing nutrient level, decreasing alkalinity and sali-nity, and improving soil structure.
