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 < 0.05) in MPs-amended treatments than those without MPs and increased with MPs age. The addition of virgin PE did not affect soil DOC content, whereas aged PE and all PLA additions significantly increased soil DOC content on day 0, probably because UV irradiation caused the degradation of MPs to smaller molecules. In addition, aged MPs addition altered DOC spectral characteristics on day 7, possibly because aged PE and PLA promote microbial decomposition of organic matter by altering soil properties. Changes in soil DOC content and specific ultraviolet absorbance (SUVA) by aged PE and PLA probably promoted the emissions of CO2 and N2O compared to virgin MPs or soil only. Our study revealed that aged PE and PLA promote GHG emissions from soil by changing DOC contents and qualities. en-copyright= kn-copyright= en-aut-name=ZhangTian en-aut-sei=Zhang en-aut-mei=Tian 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=AkaoSatoshi en-aut-sei=Akao en-aut-mei=Satoshi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=NakaharaNozomi en-aut-sei=Nakahara en-aut-mei=Nozomi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= en-aut-name=PereraGamamada Liyanage Erandi Priyangika en-aut-sei=Perera en-aut-mei=Gamamada Liyanage Erandi Priyangika kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=5 ORCID= en-aut-name=NakanoChiyu en-aut-sei=Nakano en-aut-mei=Chiyu kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=6 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=7 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=Faculty of Science and Engineering, Doshisha University kn-affil= affil-num=4 en-affil=Environmental Management Center, Okayama University kn-affil= affil-num=5 en-affil=Graduate School of Environmental and Life Science, Okayama University kn-affil= affil-num=6 en-affil=Graduate School of Natural Science and Technology, Okayama University kn-affil= affil-num=7 en-affil=Graduate School of Environmental and Life Science, Okayama University kn-affil= en-keyword=Aged MPs kn-keyword=Aged MPs en-keyword=biodegradable plastics kn-keyword=biodegradable plastics en-keyword=microplastics kn-keyword=microplastics en-keyword=nitrogen transformation kn-keyword=nitrogen transformation en-keyword=organic carbon decomposition kn-keyword=organic carbon decomposition END start-ver=1.4 cd-journal=joma no-vol=69 cd-vols= no-issue=2 article-no= start-page=137 end-page=147 dt-received= dt-revised= dt-accepted= dt-pub-year=2023 dt-pub=20230110 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Greenhouse gas emissions from agricultural soil amended with kitchen compost of varying ages en-subtitle= kn-subtitle= en-abstract= kn-abstract=Although the use of kitchen waste compost is very common, GHG emissions from soil amended with kitchen waste compost have not been studied. This study aimed to determine the effects of kitchen compost age and application rates on GHG emissions to identify optimal compost management. Soil samples mixed with kitchen waste compost at three different ages: 1 month (1M), 2 months (2M), and 3 months (3M) at two application rates (1% and 2% w/w) were incubated at 25 degrees C for 28 days under aerobic conditions. Emissions of nitrous oxide (N2O), carbon dioxide (CO2), and methane (CH4) were determined on days 3, 7, 14, 21, and 28. Results showed that N2O and CO2 emissions decreased with compost age (p < 0.05). Increased application rates of compost led to increased CO2 emissions and suppression of N2O emissions. Furthermore, CH4 was emitted from soil amended with kitchen compost even under aerobic conditions. This study suggests that 3M kitchen waste compost is optimal in terms of GHG emissions upon application to soil under aerobic conditions. en-copyright= kn-copyright= en-aut-name=ChauTran Thi Minh en-aut-sei=Chau en-aut-mei=Tran Thi Minh kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=SomeyaTakashi en-aut-sei=Someya en-aut-mei=Takashi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=AkaoSatoshi en-aut-sei=Akao en-aut-mei=Satoshi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=NakamuraMasato en-aut-sei=Nakamura en-aut-mei=Masato kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= en-aut-name=OritateFumiko en-aut-sei=Oritate en-aut-mei=Fumiko kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=5 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=6 ORCID= en-aut-name=YamaneShinzo en-aut-sei=Yamane en-aut-mei=Shinzo kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=7 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=8 ORCID= affil-num=1 en-affil=Graduate School of Environmental and Life Science, Okayama University kn-affil= affil-num=2 en-affil=Faculty of Agriculture, Saga University kn-affil= affil-num=3 en-affil=Faculty of Science and Engineering, Doshisha University kn-affil= affil-num=4 en-affil=Institute for Rural Engineering, NARO kn-affil= affil-num=5 en-affil=Institute for Rural Engineering, NARO kn-affil= affil-num=6 en-affil=Graduate School of Environmental and Life Science, Okayama University kn-affil= affil-num=7 en-affil=Faculty of Agriculture and Marine Science, Kochi University kn-affil= affil-num=8 en-affil=Graduate School of Environmental and Life Science, Okayama University kn-affil= en-keyword=Aerobic conditions kn-keyword=Aerobic conditions en-keyword=greenhouse gas emissions kn-keyword=greenhouse gas emissions en-keyword=kitchen waste compost kn-keyword=kitchen waste compost END