Pretreatment with H2O2 Alleviates the Negative Impacts of NaCl Stress on Seed Germination of Tartary Buckwheat (Fagopyrum tataricum)

Soil salinization is one of the main abiotic stress factors impacting the growth of crops and the agricultural industry today. Thus, we aimed to investigate the effects of H2O2 pretreatment on seed germination in Tartary buckwheat (Fagopyrum tataricum) seeds under salt stress and to evaluate this species’ salt tolerance. Through the preliminary experiment, this study used 50 mmol L−1 NaCl solution to induce seed stress. After soaking for 12 h in different H2O2 concentrations, seeds were laid in Petri dishes with 50 mmol L−1 NaCl for seven days and the germination parameters and physiological indicators were measured to screen the optimal H2O2 pretreatment concentration and the salt tolerance index. Our results indicated that pretreatment with 5–10 mmol L−1 H2O2 was most effective in alleviating NaCl’s impacts on the seeds’ germination parameters. Furthermore, the growth and material accumulation of seedlings was promoted; catalase, superoxide dismutase activity, and proline content were enhanced; and malondialdehyde content was reduced. Principal component analysis and stepwise regression revealed six key indicators that had a significant impact on the salt tolerance characteristics of F. tataricum, namely, germination potential, shoot fresh weight, root surface area, root average diameter, catalase activity, and superoxide dismutase activity.

Comparative Analyses Reveal Peroxidases Play Important Roles in Soybean Tolerance to Aluminum Toxicity

Aluminum (Al) toxicity is an important barrier to soybean (Glycine max (L.) Merr.) production in acid soils. However, little is known about the genes underlying Al tolerance in soybean. We aim to find the key candidate genes and investigate their roles in soybean tolerance to Al toxicity in this study. Comparative transcriptome analyses of the Al-tolerant (KF) and Al-sensitive (GF) soybean varieties under control and Al stress at 6, 12, and 24 h were investigated. A total of 1411 genes showed specific up-regulation in KF or more up-regulation in KF than in GF by Al stress, which were significantly enriched in the GO terms of peroxidase (POD) activity, transporter activity (including the known Al tolerance-related ABC transporter, ALMT, and MATE), and four families of transcription factors (AP2, C3H4, MYB, WRKY). The expression levels of seven POD genes were up-regulated by Al stress for at least one time point in KF. The H2O2 pretreatment significantly improved Al tolerance of KF, which is likely due to increased POD activity induced by H2O2. Our results suggest that PODs play important roles in soybean tolerance to Al toxicity. We also propose a list of candidate genes for Al tolerance in KF, which would provide valuable insights into the Al tolerance mechanisms in soybean.

Efficient Malathion Removal in Constructed Wetlands Coupled to UV/H2O2 Pretreatment

Intensive agriculture has led to the increasing application of pesticides, such as malathion, thus generating large volumes of untreated cropland wastewater (CropWW). In this work, a hybrid system constructed wetlands (CW) coupled in continuous with an optimized UV/H2O2 pretreatment was evaluated for the efficient removal of malathion contained in CropWW. In the first stage, 90 min UV irradiation time (UV IR) and 65 mM hydrogen peroxide (H2O2) were identified as optimal operation parameters through a central composite design. The second stage consisted of CW planted with Phragmites australis collected from the agricultural discharge area and operated as a piston flow reactor. Furthermore, CW hydraulic residence times (HRT) of 1, 2 and 3 days, including hydraulic coupling, were evaluated. The removal efficiencies obtained in the first stage (UV/H2O2) were 94 ± 2.5% of malathion and 45 ± 2.5% of total organic carbon (TOC). In stage two (CW) 65 ± 9.6% TOC removal was achieved during the first 17 days, from which around 24% was associated to the biosorption of malathion byproducts. Subsequently, and until the operation ends, CW removed about 80% of TOC for 2 and 3 days HRT, with no significant differences (p > 0.2), which is higher than those reported in several studies involving only advanced oxidation processes (AOP) with UV IR times above 240 min and even for systems using catalysts. The results obtained indicate that the system UV/H2O2-CW is a technically suitable option for the treatment of CropWW with a high content of malathion mainly found in developing countries. Moreover, the hybrid system proposed also represent significant reduction in the size of the treatment plant.

Impact of Alkaline H2O2 Pretreatment on Methane Generation Potential of Greenhouse Crop Waste under Anaerobic Conditions

This paper intended to explore the effect of alkaline H2O2 pretreatment on the biodegradability and the methane generation potential of greenhouse crop waste. A multi-variable experimental design was implemented. In this approach, initial solid content (3–7%), reaction time (6–24 h), H2O2 concentration (1–3%), and reaction temperature (50–100 °C) were varied in different combinations to determine the impact of alkaline H2O2 pretreatment. The results indicated that the alkaline H2O2 pretreatment induced a significant increase in the range of 200–800% in chemical oxygen demand (COD) leakage into the soluble phase, and boosted the methane generation potential from 174 mLCH4/g of volatile solid (VS) to a much higher bracket of 250–350 mLCH4/gVS. Similarly, the lignocellulosic structure of the material was broken down and hydrolyzed by H2O2 dosing, which increased the rate of volatile matter utilization from 31% to 50–70% depending on selected conditions. Alkaline H2O2 pretreatment was optimized to determine optimal conditions for the enhancement of methane generation assuming a cost-driven approach. Optimal alkaline H2O2 pretreatment conditions were found as a reaction temperature of 50 °C, 7% initial solid content, 1% H2O2 concentration, and a reaction time of six h. Under these conditions, the biochemical methane potential (BMP) test yielded as 309 mLCH4/gVS. The enhancement of methane production was calculated as 77.6% compared to raw greenhouse crop wastes.

Biofouling control by UV/H2O2 pretreatment for brackish water reverse osmosis process

UV applied with H2O2 is a well-known advanced oxidation process (AOP) for degradation of trace organic compounds. In this study, the UV/H2O2 process was applied as a pre-treatment step to control reverse osmosis biofouling.