The Yellow River(YR),China’s second-longest river,remains understudied regarding its greenhouse gases(GHGs)emissions,particularly the impacts of urban drainage ditches and wastewater treatment facilities on regional ...The Yellow River(YR),China’s second-longest river,remains understudied regarding its greenhouse gases(GHGs)emissions,particularly the impacts of urban drainage ditches and wastewater treatment facilities on regional GHGs dynamics.This study investigated methane(CH_(4))and carbon dioxide(CO_(2))concentrations,fluxes and stable carbon isotopes(δ^(13)C-CH_(4)and δ^(13)C-CO_(2))across six main stream,three ditches,and one wastewater treatment site along the upper Lanzhou section of the YR,spanning from the urban entrance(36.176°N,103.449°E)to the exit of Lanzhou city(36.056°N,104.020°E).Measured CH_(4)diffusion fluxes in mainstem sites ranged from 0.01 to 2.58 mmol·m^(−2)·d^(−1)(mean:0.36 mmol·m^(−2)·d^(−1)),while ebullitive fluxes(gas bubbles)ranged from 0.01 to 18.89 mmol·m^(−2)·d^(−1)(mean:0.90 mmol·m^(−2)·d^(−1)).CO_(2)diffusion fluxes varied between 9.16–92.80 mmol·m^(−2)·d^(−1)(averaged:39.11 mmol·m^(−2)·d^(−1))at these locations.Ebullition(bubble)fluxes accounted for 53.1%±22.4%(range:9.0%to 98.4%)to total CH_(4)emissions(diffusion plus ebullition),with peak fluxes occurring during summer,indicating its significance as a CH_(4)transport mechanism.Notably,both diffusion CH_(4)and CO_(2)fluxes and ebullitive CH_(4)rates at ditch sites substantially exceeded those in mainstream reaches.The lowest CH_(4)and highest CO_(2)concentrations were observed at a wastewater treatment site,likely resulting from the removal of high organic loads.Acetoclastic methanogenesis—the process converting acetate-derived methyl groups to CH_(4)—was identified as the dominant production pathway in both mainstream and ditch environments.CH_(4)and CO_(2)flux magnitudes in the upper YR(Lanzhou section)were comparable to those observed in subtropical Yangtze River tributaries.These results demonstrate that anthropogenic influences significantly enhance CO_(2)/CH_(4)emissions,and the lateral exports of dissolved carbon(DIC and DOC)in the main stream site was quantified.,which cannot be overlooked.The findings emphasize the critical need to account for pronounced spatiotemporal variations in arid-region GHG fluxes to improve basin-scale estimates for the YR.展开更多
Rice planting(RP)is significant to methane(CH4_(4))emissions from paddy fields,but its effect on the relative contribution of the acetoclastic methanogenesis to total CH4_(4) production(F_(ac))and the fraction of CH4_...Rice planting(RP)is significant to methane(CH4_(4))emissions from paddy fields,but its effect on the relative contribution of the acetoclastic methanogenesis to total CH4_(4) production(F_(ac))and the fraction of CH4_(4) oxidized(Fox)is poorly understood.To quantify the responses of the F_(ac) and Fox to RP,we investigated CH4_(4) fluxes,CH4_(4) production and oxidation potentials,dissolved CH4_(4) concentrations,and their stable carbon isotopes in a flooded paddy soil.The mcrA and pmoA gene copies were also determined by quantitative polymerase chain reaction(qPCR).Compared with the unplanted soil(control,CK),the seasonal CH4_(4) emissions from the planted soil were significantly enhanced,13.6 times,resulting in large decreases in the CH4_(4) concentrations in the soil solution.This indicated that much more CH4_(4) was released into the atmosphere by the RP than was stored in the soils.Acetoclastic methanogenesis became more important from the tillering stage(TS)to the ripening stage(RS)for the CK,with F_(ac) values increased from 17%-20% to 46%-55%.With RP,the F_(ac) values were enhanced by 10%-20%,and it significantly increased the copy numbers of the mcrA gene at the four rice stages(TS,booting stage(BS),grain-filling stage(GS),and RS).Furthermore,the effect of the RP on the abundance of the mcrA gene was highly concurrent with the effect on the F_(ac) values.At the TS,the Fox values at the soil-water interface were around 50%-75% for the CK,being 15%-20% lower than those of the RP in the rhizosphere.It increased to 65%-100% at the GS,but was reduced by 20%-30% after the RP.These differences might be because the copy numbers of the pmoA gene were significantly raised at the TS while lowered at the GS by the RP.This was further demonstrated by the strong correlations between the effect of the RP on the abundance of the pmoA gene and the effect on the Fox values.These findings suggest that RP markedly impacts on the abundances of the mcrA and pmoA genes,affecting the pathway of CH4_(4) production and the fraction of CH4_(4) oxidization,respectively.展开更多
基金funded by the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB0950000)the NSFC(Grant No.42201155+2 种基金4240114742201137)the State Key Laboratory of Cryospheric Science and Frozen Soil Engineering(CSFSE-ZQ-2410).
文摘The Yellow River(YR),China’s second-longest river,remains understudied regarding its greenhouse gases(GHGs)emissions,particularly the impacts of urban drainage ditches and wastewater treatment facilities on regional GHGs dynamics.This study investigated methane(CH_(4))and carbon dioxide(CO_(2))concentrations,fluxes and stable carbon isotopes(δ^(13)C-CH_(4)and δ^(13)C-CO_(2))across six main stream,three ditches,and one wastewater treatment site along the upper Lanzhou section of the YR,spanning from the urban entrance(36.176°N,103.449°E)to the exit of Lanzhou city(36.056°N,104.020°E).Measured CH_(4)diffusion fluxes in mainstem sites ranged from 0.01 to 2.58 mmol·m^(−2)·d^(−1)(mean:0.36 mmol·m^(−2)·d^(−1)),while ebullitive fluxes(gas bubbles)ranged from 0.01 to 18.89 mmol·m^(−2)·d^(−1)(mean:0.90 mmol·m^(−2)·d^(−1)).CO_(2)diffusion fluxes varied between 9.16–92.80 mmol·m^(−2)·d^(−1)(averaged:39.11 mmol·m^(−2)·d^(−1))at these locations.Ebullition(bubble)fluxes accounted for 53.1%±22.4%(range:9.0%to 98.4%)to total CH_(4)emissions(diffusion plus ebullition),with peak fluxes occurring during summer,indicating its significance as a CH_(4)transport mechanism.Notably,both diffusion CH_(4)and CO_(2)fluxes and ebullitive CH_(4)rates at ditch sites substantially exceeded those in mainstream reaches.The lowest CH_(4)and highest CO_(2)concentrations were observed at a wastewater treatment site,likely resulting from the removal of high organic loads.Acetoclastic methanogenesis—the process converting acetate-derived methyl groups to CH_(4)—was identified as the dominant production pathway in both mainstream and ditch environments.CH_(4)and CO_(2)flux magnitudes in the upper YR(Lanzhou section)were comparable to those observed in subtropical Yangtze River tributaries.These results demonstrate that anthropogenic influences significantly enhance CO_(2)/CH_(4)emissions,and the lateral exports of dissolved carbon(DIC and DOC)in the main stream site was quantified.,which cannot be overlooked.The findings emphasize the critical need to account for pronounced spatiotemporal variations in arid-region GHG fluxes to improve basin-scale estimates for the YR.
基金financially supported by the National Key Research and Development Program of China(No.2017YFD 0300105)the National Natural Science Foundation of China(Nos.41571232,41671241,and 41877325)+1 种基金the Youth Innovation Promotion Association of Chinese Academy of Sciences(CASmember No.2018349)。
文摘Rice planting(RP)is significant to methane(CH4_(4))emissions from paddy fields,but its effect on the relative contribution of the acetoclastic methanogenesis to total CH4_(4) production(F_(ac))and the fraction of CH4_(4) oxidized(Fox)is poorly understood.To quantify the responses of the F_(ac) and Fox to RP,we investigated CH4_(4) fluxes,CH4_(4) production and oxidation potentials,dissolved CH4_(4) concentrations,and their stable carbon isotopes in a flooded paddy soil.The mcrA and pmoA gene copies were also determined by quantitative polymerase chain reaction(qPCR).Compared with the unplanted soil(control,CK),the seasonal CH4_(4) emissions from the planted soil were significantly enhanced,13.6 times,resulting in large decreases in the CH4_(4) concentrations in the soil solution.This indicated that much more CH4_(4) was released into the atmosphere by the RP than was stored in the soils.Acetoclastic methanogenesis became more important from the tillering stage(TS)to the ripening stage(RS)for the CK,with F_(ac) values increased from 17%-20% to 46%-55%.With RP,the F_(ac) values were enhanced by 10%-20%,and it significantly increased the copy numbers of the mcrA gene at the four rice stages(TS,booting stage(BS),grain-filling stage(GS),and RS).Furthermore,the effect of the RP on the abundance of the mcrA gene was highly concurrent with the effect on the F_(ac) values.At the TS,the Fox values at the soil-water interface were around 50%-75% for the CK,being 15%-20% lower than those of the RP in the rhizosphere.It increased to 65%-100% at the GS,but was reduced by 20%-30% after the RP.These differences might be because the copy numbers of the pmoA gene were significantly raised at the TS while lowered at the GS by the RP.This was further demonstrated by the strong correlations between the effect of the RP on the abundance of the pmoA gene and the effect on the Fox values.These findings suggest that RP markedly impacts on the abundances of the mcrA and pmoA genes,affecting the pathway of CH4_(4) production and the fraction of CH4_(4) oxidization,respectively.
