start-ver=1.4 cd-journal=joma no-vol=19 cd-vols= no-issue=1 article-no= start-page=36 end-page=43 dt-received= dt-revised= dt-accepted= dt-pub-year=2025 dt-pub=2025 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Evaluation of the temporal behavior of fulvic acid iron in Asahi River, Okayama, Japan en-subtitle= kn-subtitle= en-abstract= kn-abstract=Iron is essential for biogeochemical processes in aquatic ecosystems, but its riverine concentration can be affected by environmental conditions. This study assessed weekly fulvic acid iron (FAFe) concentration at a single sampling site in Asahi River from 2022?2023 to explore the differences in the temporal scales. The objectives of this study were to evaluate the effects of physicochemical properties of the river on the concentration of FAFe, analyze the concentration of FAFe in spring, summer, autumn and winter, and assess the relationship between FAFe concentration and land use types of the watershed. The results indicated that physicochemical parameters, such as pH and surface water temperature (SWT) seemed to influence FAFe concentration (p < 0.05). Hydrological dynamics influenced FAFe concentration and transport, revealing an increasing trend during spring (p < 0.001) and summer (p = 0.05), with non-significant trends during autumn and winter (p > 0.05). FAFe exhibited a strong positive correlation with total organic carbon (TOC) (p < 0.001). Upland fields significantly influenced FAFe concentration (p < 0.01) through runoff with abundant NO3? and PO43? into the river. Thus, FAFe concentration in Asahi River was influenced by pH, SWT, TOC, hydrological regime, and agricultural runoff. en-copyright= kn-copyright= en-aut-name=YengehRohdof Lactem en-aut-sei=Yengeh en-aut-mei=Rohdof Lactem kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=SomuraHiroaki en-aut-sei=Somura en-aut-mei=Hiroaki kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=MoroizumiToshitsugu en-aut-sei=Moroizumi en-aut-mei=Toshitsugu kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=MoriYasushi en-aut-sei=Mori en-aut-mei=Yasushi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= en-aut-name=MaedaMorihiro en-aut-sei=Maeda en-aut-mei=Morihiro kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=5 ORCID= affil-num=1 en-affil=Graduate School of Environmental and Life Science, Okayama University kn-affil= affil-num=2 en-affil=Graduate School of Environmental and Life Science, Okayama University kn-affil= affil-num=3 en-affil=Graduate School of Environmental and Life Science, Okayama University kn-affil= affil-num=4 en-affil=Graduate School of Environmental and Life Science, Okayama University kn-affil= affil-num=5 en-affil=Graduate School of Environmental and Life Science, Okayama University kn-affil= en-keyword=dissolved iron kn-keyword=dissolved iron en-keyword=seasonal variation kn-keyword=seasonal variation en-keyword=dissolved organic matter kn-keyword=dissolved organic matter en-keyword=fulvic acid iron kn-keyword=fulvic acid iron END start-ver=1.4 cd-journal=joma no-vol= cd-vols= no-issue= article-no= start-page= end-page= dt-received= dt-revised= dt-accepted= dt-pub-year=2024 dt-pub=20241214 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Effects of aged microplastics on paddy soil properties and greenhouse gas emissions under laboratory aerobic conditions en-subtitle= kn-subtitle= en-abstract= kn-abstract=Microplastics (MPs) formed after changes in chemical or physical properties may alter soil properties, which in turn may affect microbial activities and greenhouse gas (GHG) emissions. However, few studies have focused on the effects of aged MPs changes on soil properties and greenhouse gas emissions. Therefore, we aimed to investigate the impact of MPs with different aging times on soil GHG emissions and dissolved organic carbon (DOC). Low-density polyethylene (PE) and polylactic acid (PLA) were treated with ultraviolet (UV) irradiation for 0?2?weeks. Soil was incubated with PE or PLA 1% (w/w) concentration at 60% water holding capacity (WHC) for 35?days. Emissions of nitrous oxide (N2O) and carbon dioxide (CO2) were measured on days 0, 1, 3, 5, 7, 14, 21, 28, and 35. Results showed that CO2 and N2O emissions were higher (p?