Different Concentrations Of Dissolved Oxygen Research Articles

Impact of Aerated Drip Irrigation and Nitrogen Application on Soil Properties, Soil Bacterial Communities and Agronomic Traits of Cucumber in a Greenhouse System.

Root hypoxia stress and soil nutrient turnover have been related to reduced crop productivity. Aerated drip irrigation (ADI) can effectively enhance crop productivity and yield. However, the response of the soil bacterial community to different irrigation water dissolved oxygen (DO) concentrations remains elusive due to the extreme sensitivity of microorganisms to environmental variations. We investigated the effects of aerated irrigation with different concentrations of DO on soil properties and agronomic performance of cucumber, as well as the contribution of the bacterial community. We performed experiments on cucumber cultivation in Shouguang, China, including different irrigation methods (ADI: O2-10 and O3-20 mg L-1, non-aerated groundwater: O1-5 mg L-1) and nitrogen (N) application rates: 240 and 360 kg N ha-1. ADI (particularly O2) significantly improved soil properties, root growth, cucumber yields, and irrigation water use efficiency (IWUE), and appropriate DO concentrations reduced N fertilizer application and increased crop yields. Furthermore, these changes were associated with bacterial community diversity, aerobic bacteria abundance, and consolidated bacterial population stability within the network module. Environmental factors such as soil respiration rate (Rs), DO, and NO3--N have significant effects on bacterial communities. The FAPROTAX results demonstrated enhanced nitrification (Nitrospira) and aerobic nitrite oxidation by soil bacteria under ADI, promoting the accumulation of effective soil N and improved soil fertility and crop yield. Appropriate DO concentration is conducive to the involvement of soil bacterial communities in regulating soil properties and cucumber growth performance, which are vital for the sustainable development of facility agriculture.

Green optical dissolved oxygen sensor based on a chlorophyll–zinc complex extracted from the plant Brassica oleracea L

In this study, we present the development of a green and high-sensitivity optical dissolved oxygen (DO) sensor for measuring DO in water using spectrofluorimetry. For the development of the sensor element, an organometallic complex was synthesized from the “chlorophyll A” molecule, extracted from the plant Brassica oleracea L., with zinc insertion (Zn+2) replacing the magnesium (Mg+2). In the investigation, we evaluated the fluorescence suppression of the organometallic zinc complex for samples with different concentrations of DO. The complex has shown two absorption regions, 350–475 nm and 600–700 nm. We observed the fluorescence suppression of the complex, when excited at 440 nm and analyzed at 635 nm, by using the spinning oxygenation and air pump flow methods, respectively. The fluorescence suppression curves presented first-order decay with good correlation, resulting in R2=0.98282 and R2=0.83849 for the spinning and air pump flow methods, respectively. To validate the methodology, we developed a prototype of a bench sensor. For the relation between the fluorescence intensity and oxygenation time, we obtained a ratio curve with R2=0.9809. The methodology and prototype sensor developed in this work are presented as a new optical method for the measurement of DO.

Determination of dissolved oxygen based on photoinduced electron transfer from quantum dots to methyl viologen

A rapid colorimetric methodology based on photoinduced electron transfer from excited CdS quantum dots (CdS QDs) to methyl viologen (MV2+) has been developed for the sensitive determination of dissolved oxygen (DO) content. The reduction of MV2+ is initiated by light excitation of CdS QDs, which induces the electron transfer from sacrificial donor glutathione (GSH) to the photogenerated hole of CdS QDs. Due to the presence of oxygen, the reduced radical-cation of methyl viologen (MV+˙) could be rapidly reoxidized, thus turning into the original methyl viologen dication (MV2+). The existence of MV+˙ is confirmed by electron paramagnetic resonance technique. This proposed colorimetric methodology has been applied to quantify the concentration of DO in real water samples. The result is consistent with the value obtained while adopting the traditional standard Winkler's methodology. A linear response of the absorbance of CdS QDs-GSH-MV system to the different concentrations of DO is obtained in the range of 0.75∼7.95 ppm, with a detection limit of 0.23 ppm in pH 7.5.

Monitoring the impact of dissolved oxygen and nitrite on anoxic biofilm in continuous denitrification process.

An anoxic biofilm involved in continuous denitrification process was monitored to investigate the effect of different concentrations of influent dissolved oxygen (DO) or nitrite on the biofilm. Microelectrode measurements evidenced nitrate removal activity of biofilm. When different concentrations of DO were applied to the reactor, generally decreased concentrations of DO were observed as bed depth increased from the bottom of the reactor. Greatest decrease of the DO was observed in the lower 20% of the bed depth. Nitrate removal efficiency was inversely proportional to influent DO concentrations (8.3-11.9 DO mg L(-1)) or nitrite loading rates (0-5.5 N-NO2- kg m(-3) day(-1)) employed in this study. Nitrite loading rates to achieve more than 90% of nitrate removal efficiency were 1.46 N-NO2- kg m(-3) day(-1) or less at pH 7.5 and 0.34 N-NO2- kg m(-3) day(-1) or less at pH 6.8. Nitrate removal efficiency was 63% or more within the lower 20% of the bed depth at the nitrite loading rates that allowed more than 90% of nitrate removal efficiency of the reactor. The results of this study provide first quantitative data that nitrate removal performance of an anoxic biofilm is inhibited by DO or nitrite, reported to be a limiting factor in the suspended biological denitrification process.