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2 Journal of Ecological Engineering

2 2021

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Rice Growth, Grain Zinc, and Soil Properties under Saline Irrigation Conditions

Thi Lan Phuong Dinh, Hang Nga Nguyen Thi, Nguyen Hoa Thanh, Nguyen Lien Thi

Journal of Ecological Engineering

2021

Vol. 22, nr 9

59--70

This research evaluated rice growth and yield as well as Zn accumulation in both soil and grain under saline water irrigation conditions. The experiment consisted of a series of pots containing rice plants and paddy soil, with the application of irrigation treatments of five different salinity levels (1.5, 2, 3, 4, and 5‰ with a drip irrigation system). The results show that the salinity accumulation levels in soil can increase by up to 2.8‰ following the application of 5‰ salinity irrigation water during the development stages. Besides, this study also aimed to evaluate the influences of saline water irrigation on the observed rice yields, plant height, leaf length, and leaf width. In the results, irrigation with 3‰ saline water reduced potential rice yield by 58.6% and the length of rice leaves by one-third. Higher salinity of 4‰ in the irrigation water produced only 24% of average potential productivity, and 5‰ water salinity resulted in no yield. Furthermore, salt stress limited the mobile Zn content in paddy soil, reducing the Zn accumulation in grains by between 36.27% and 83.21%. Thus, the study shows that controlling salinity in irrigation water management is essential for controlling the yield and nutrient Zn content in rice grains.

Removal of Nitramine Explosives in Aqueous Solution by UV-Mediated Advanced Oxidation Process in Near-Neutral Conditions

Khue Do Ngoc, Bach Vu Quang, Binh Nguyen Thanh, Minh Do Binh, Nam Pham Thi, Loi Vu Duc, Nguyen Hoa Thanh

Journal of Ecological Engineering

2021

Vol. 22, nr 6

232--243

Explosive compounds are hazardous to the environment, posing a serious risk to human and animal health and the ecosystem. The primary goal of research was to compare the efficiency of UV/H2O2, photo-Fenton, electro (EO)/ UV/H2O2 processes at near-neutral pH (pH=6) on the degradation of nitramine explosives (NAs), such as hexogen (RDX), octogen (HMX), and tetryl (TET), in an aqueous solution. The effect of operational conditions, likely pH of the solution, initial H2O2 concentration, initial Fe2+ concentration, and solution temperature, was observed. The removal kinetics fit with first-order kinetics and were in the order: photo-Fenton >EO/UV/ H2O2 > UV/ H2O2. The results showed higher rate constant values for TET, RDX and HMX removal by UV/ H2O2 (k = 0.07778, 0.03791 and 0.03786 min-1), EO/UV/ H2O2 (k = 0.16599, 0.1475 and 0.08674 min-1) and photo-Fenton (k = 0.18018, 0.1501 and 0.09336 min-1) processes. Furthermore, TET, RDX and HMX were mineralized at 59.7%, 45.1%, and 25.1 %, respectively, under optimum conditions after 60 min of the photo-Fenton process. From the economic perspective, photo-Fenton only requires 2.132–4.113 kWh m-3 to completely reduce NAs. Finally, acute toxicity towards Vibrio fischeri was defeated after usage of near-neutral photo-Fenton. Thus, photo-Fenton at circum-neutral is promising for low-cost, eco-friendly and efficient processes for treating nitramine explosives in aqueous solutions.