Mechanistic Study of the Effects of Agricultural Amendments on Photochemical Processes in Paddy Water during Rice Growth

Abstract

The photochemical properties of paddy water might be affected by the commonly used amendments in rice fields owing to the associated changes in water chemistry; however, this important aspect has rarely been explored. We examined the effects of agricultural amendments on the photochemistry of paddy water during rice growth. The amendments significantly influenced the photogenerated reactive intermediates (RIs) in paddy water, such as triplet dissolved organic matter (3DOM*), singlet oxygen, and hydroxyl radicals. Compared with control experiments without amendments, the application of straw and lime increased the RI concentrations by up to 16.8 and 11.1 times, respectively, while biochar addition had limited effects on RI generation from paddy water in in situ experiments under sunlight. Fluorescence emission–excitation matrix spectroscopy, Fourier transform ion cyclotron resonance mass spectrometry, and structural equation modeling revealed that upon the addition of straw and lime amendments, humified DOM substances contained lignins, proteins, and fulvic acids, which could produce more RIs under irradiation. Moreover, the amendments significantly accelerated the degradation rate of 2,4-dichlorophenol but led to the 3DOM*-mediated formation of more toxic and stable dimeric products. This study provides new insights into the effects of amendments on the photochemistry of paddy water and the pathways of abiotic degradation of organic contaminants in paddy fields.

The Oxidation and Immobilization of As(III) by Colloidal Ferric Hydroxide in the Concomitant Pollution of Oxytetracycline

“…TEMP was selected as the spin-trapping agent for EPR measurement and furfuryl alcohol (FFA) was selected as the scavengers of 1 O 2 . 53 As shown in Figure S9a, the TEMPO signal (oxidation adducts of TEMP) was not significantly increased in the CFH/OTC system in oxic conditions. Furthermore, there was no insignificant difference in the transformation of OTC and As(III) after adding FFA (Figure S9b,S9c), which indicated that there might be no 1 O 2 formation in our study.…”

“…Additional experiments were conducted to explore the possible role of 1 O 2 . TEMP was selected as the spin-trapping agent for EPR measurement and furfuryl alcohol (FFA) was selected as the scavengers of 1 O 2 . As shown in Figure S9a, the TEMPO signal (oxidation adducts of TEMP) was not significantly increased in the CFH/OTC system in oxic conditions.…”

Photochemical Transformation of Dissolved Organic Matter in Surface Water Augmented the Formation of Disinfection Byproducts

“…The stronger photoactivity of DOM Re could be attributed to its more content of saturated molecules (Figure D), as the saturated compounds (high H/C) were positively correlated to f TMP and Φ 1O2 as indicated by previous observations. , Interestingly, although DOM Ri presented lower Φ •OH than DOM Re , the [•OH] ss and production rate of •OH for DOM Ri was higher than that of DOM Re (Table S6 and Figure S5). More generation of •OH in DOM Ri indicated that the •OH precursor (e.g., more low-MW substances) in DOM Ri was more photosensitive. , Moreover, model DOM isolates such as Suwannee River fulvic acid (SRFA) were commonly used in the studies on the DOM photoreactivity. , f TMP , Φ 1O2 , and Φ •OH of DOM Re and DOM Ri were 1 order of magnitude lower than that of SRFA, , and this was probably because SRFA (12.06 of HIX) contained more abundant humic components as the photosensitizer than DOM Re (1.84) and DOM Ri (0.70) …”

“…19,51 f TMP , Φ 1O2 , and Φ •OH of DOM Re and DOM Ri were 1 order of magnitude lower than that of SRFA, 19,51 and this was probably because SRFA (12.06 of HIX) contained more abundant humic components as the photosensitizer than DOM Re (1.84) and DOM Ri (0.70). 52 3.3. Photochemical-Induced Changes in Bulk Properties and Molecular Compositions of DOM.…”

Biochar-supported nano-scale zerovalent iron activated persulfate for remediation of aromatic hydrocarbon-contaminated soil: an in-situ pilot-scale study

“…Biochar (BC) is an excellent supporting material with high porous structures and surface areas, which has been frequently used as a soil amendment and loading of catalysts in recent years (Zeng et al 2022). It has been well demonstrated that biochar protects nZVI from agglomeration and rapid oxidation, and thus enhances the degradation of pollutants by PS activation with biochar supported nZVI (Shaheen et al 2022).…”