scholarly journals CO<sub>2</sub> and CH<sub>4</sub> fluxes are decoupled from organic carbon loss in drying reservoir sediments

2019 ◽  
Author(s):  
Tricia Light ◽  
Núria Catalán ◽  
Santiago Giralt ◽  
Rafael Marcé
Keyword(s):  
Organic Carbon ◽  
Sediment Cores ◽  
Carbon Mineralization ◽  
Organic Carbon Content ◽  
Co2 Efflux ◽  
Carbon Loss ◽  
Organic C ◽  
Reservoir Sediments ◽  
Organic Carbon Burial ◽  
Organic Carbon Mineralization

Abstract. Reservoirs are a prominent feature of the current global hydrological landscape, and their sediments are the site of extensive organic carbon burial. Meanwhile, reservoirs frequently go dry due to drought and/or water management decisions. Nonetheless, the fate of organic carbon buried in reservoir sediments upon drying is largely unknown. Here, we conducted a 45-day-long laboratory incubation of sediment cores collected from a western Mediterranean reservoir to investigate carbon dynamics in drying sediment. Drying sediment cores emitted more CO2 over the course of the incubation than sediment cores incubated with overlaying water (206.7 ± 47.9 vs. 69.2 ± 18.1 mmol CO2 m−2 day−1, mean ± SE). Organic carbon content at the end of the incubation was lower in drying cores, which suggests that this higher CO2 efflux was due to organic carbon mineralization. However, the apparent rate of organic C reduction in the drying sediments (568.6 ± 247.2 mmol CO2 m−2 day−1, mean ± SE) was higher than C emission. Meanwhile, sediment cores collected from a reservoir area that had already been exposed for 2+ years displayed net CO2 influx from the atmosphere to the sediment (−136.0 ± 27.5 mmol CO2 m−2 day−1, mean ± SE) during the incubation period. Sediment mineralogy suggests that this CO2 influx was caused by a relative increase in calcium carbonate chemical weathering. Thus, we found that while organic carbon decomposition in newly dry reservoir sediment causes measurable organic carbon loss and carbon gas emissions to the atmosphere, other processes can offset these emissions on short time frames and compromise the use of carbon emissions as a proxy for organic carbon mineralization in drying sediments.

scholarly journals Response of organic carbon mineralization and bacterial communities to soft rock additions in sandy soils

PeerJ ◽  
2020 ◽  
Vol 8 ◽  
pp. e8948 ◽  
Author(s):  
Zhen Guo ◽  
Jichang Han ◽  
Juan Li
Keyword(s):  
Organic Carbon ◽  
Sandy Soil ◽  
High Throughput Sequencing ◽  
Carbon Mineralization ◽  
Soft Rock ◽  
Available Phosphorus ◽  
Organic Carbon Content ◽  
K Value ◽  
Organic Carbon Mineralization ◽  
Richness Index

Bacteria play a vital role in biotransformation of soil organic carbon (SOC). However, mechanisms of bacterium and organic carbon mineralization remain unclear during improvement of sandy soil using soft rock additions. In this study, four treatments with differing ratios of soft rock to sand of 0:1 (CK), 1:5 (C1), 1:2 (C2) and 1:1 (C3) were selected for mineralization incubation and high-throughput sequencing. The results showed that SOC, total nitrogen (TN), available phosphorus (AP), nitrate nitrogen (NO${}_{3}^{-}$-N), and mass water content (WC) of sandy soil increased significantly after addition of soft rock (P < 0.05). Compared with the CK treatment, cumulative mineralization and potential mineralized organic carbon content of C1, C2 and C3 increased by 71.79%–183.86% and 71.08%–173.33%. The cumulative mineralization rates of organic carbon treated with C1 and C2 were lower, 16.96% and 17.78%, respectively (P > 0.05). The three dominant bacteria were Actinobacteria, Proteobacteria and Chloroflexi, among which Proteobacteria was negatively correlated with mineralization of organic carbon (P < 0.01). The mineralization rate constant (k) was positively correlated and negatively correlated with Cyanobacteria and Nitrospirae, respectively. Under C2 treatment, Proteobacteria and Nitrospirae had the largest increase, and Cyanobacteria had the largest decrease. Compared with other treatments, C2 treatment significantly increased bacterial diversity index, richness index and evenness index, and the richness index had a negative correlation with k value. In conclusion, when the ratio of soft rock to sand was 1:2, the k of SOC could be reduced. In addition, the retention time of SOC can be increased, and resulting carbon fixation was improved.

scholarly journals The mineralization characteristics of organic carbon and particle composition analysis in reconstructed soil with different proportions of soft rock and sand

PeerJ ◽  
2019 ◽  
Vol 7 ◽  
pp. e7707 ◽  
Author(s):  
Zhen Guo ◽  
Jichang Han ◽  
Yan Xu ◽  
Yangjie Lu ◽  
Chendi Shi ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Soil Structure ◽  
Carbon Mineralization ◽  
Soft Rock ◽  
Composition Analysis ◽  
Organic Carbon Content ◽  
Mineralization Process ◽  
Particle Composition ◽  
Decline Phase ◽  
Organic Carbon Mineralization

The organic carbon mineralization process reflects the release intensity of soil CO2. Therefore, the study of organic carbon mineralization and particle composition analysis of soft rock and sand compound soil can provide technical support and a theoretical basis for soil organic reconstruction (soil structure, materials and biological nutrition). Based on previous research, four treatments were selected: CK (soft rock:sand=0:1), C1 (soft rock:sand=1:5), C2 (soft rock:sand=1:2) and C3 (soft rock:sand=1:1), respectively. Specifically, we analyzed the organic carbon mineralization process and soil particle composition by lye absorption, laser granulometer, and scanning electron microscope. The results showed that there was no significant difference in organic carbon content between C1, C2 , and C3 treatments, but they were significantly higher than in the CK treatment (P < 0.05). The organic carbon mineralization rate in each treatment accords with a logarithmic function throughout the incubation period (P < 0.01), which can be divided into a rapid decline phase in days 1 to 11 followed by a steady decline phase in days 11 to 30. The cumulative mineralization on the 11th day reached 54.96%–74.44% of the total mineralization amount. At the end of the incubation, the cumulative mineralization and potential mineralizable organic carbon content of the C1, C2 and C3 treatments were significantly higher than those of the CK treatment. The cumulative mineralization rate was also the lowest in the C1 and C2 treatment. The turnover rate constant of soil organic carbon in each treatment was significantly lower than that of the CK treatment, and the residence time increased. With the increase of volume fraction of soft rock, the content of silt and clay particles increased gradually, the texture of soil changed from sandy soil to sandy loam, loam , and silty loam, respectively. With the increase of small particles, the structure of soil appear ed to collapse when the volume ratio of soft rock was 50%. A comprehensive mineralization index and scanning electron microscopy analysis, when the ratio of soft rock to sand volume was 1:5–1:2, this can effectively increase the accumulation of soil organic carbon. Then, the distribution of soil particles was more uniform, the soil structure was stable (not collapsed), and the mineralization level of unit organic carbon was lower. Our research results have practical significance for the large area popularization of soft rock and sand compound technology.

scholarly journals The mineralization characteristics of organic carbon and particle composition analysis in reconstructed soil with different proportions of soft rock and sand

2019 ◽  
Author(s):  
Zhen Guo ◽  
Jichang Han ◽  
Yan Xu ◽  
Chang Tian ◽  
Chendi Shi ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Carbon Mineralization ◽  
Soft Rock ◽  
Composition Analysis ◽  
Organic Carbon Content ◽  
Mineralization Process ◽  
Particle Composition ◽  
Decline Phase ◽  
Organic Carbon Mineralization

AbstractThe organic carbon mineralization process can reflect the release intensity of soil CO2. Therefore, the study of organic carbon mineralization and particle composition analysis of soft rock and sand compound soil can provide technical support and theoretical basis for the theory of soil organic reconstruction. Based on the previous research, this paper mainly selected four typical treatments of 0:1 (CK), 1:5 (C1), 1:2 (C2) and 1:1 (C3), respectively, and analyzed the soil organic carbon mineralization process and particle composition by lye absorption method, laser particle size meter and scanning electron microscope. The results showed that there was no significant difference in organic carbon content between C1, C2 and C3 treatments, but they were significantly higher than CK treatment (P < 0.05). The organic carbon mineralization rate of each treatment accords with a logarithmic function throughout the culture period (P < 0.01), which can be divided into a rapid decline phase of 1-11 days and a steady decline phase of 11-30 days. The cumulative mineralization amount on the 11th day reached 54.96%-74.44% of the total mineralization amount. At the end of the culture, the cumulative mineralization and potential mineralizable organic carbon content of C1 and C2 treatments were significantly higher than those of CK treatment, and the cumulative mineralization rate was also the lowest with C1 and C2 treatment. The turnover rate constant of soil organic carbon in each treatment was significantly lower than that of CK treatment, and the residence time increased. With the increase of volume fraction of soft rock, the content of silt and clay particles increases gradually, the texture of soil changes from sandy soil to sandy loam, loam and silty loam, and because of the increase of small particles, the structure of soil appears to collapse when the volume ratio of soft rock was 50%. In summary, the ratio of soft rock to sand volume was 1:5-1: 2, which can effectively increased the accumulation of soil organic carbon. At this time, the distribution of soil particles was more uniform, the soil structure was stable, and the mineralization level of unit organic carbon was lower. The research results have practical significance for the large area popularization of soft rock and sand compound technology.

Carbon, nitrogen and phosphorus storage in subtropical seagrass meadows: examples from Florida Bay and Shark Bay

2012 ◽  
Vol 63 (11) ◽  
pp. 967 ◽  
Author(s):  
James W. Fourqurean ◽  
Gary A. Kendrick ◽  
Laurel S. Collins ◽  
Randolph M. Chambers ◽  
Mathew A. Vanderklift
Keyword(s):  
Organic Carbon ◽  
Carbon Content ◽  
Primary Productivity ◽  
Florida Bay ◽  
Organic Carbon Content ◽  
Nitrogen And Phosphorus ◽  
Organic C ◽  
Shark Bay ◽  
Seagrass Meadows ◽  
C Storage

Seagrass meadows in Florida Bay and Shark Bay contain substantial stores of both organic carbon and nutrients. Soils from both systems are predominantly calcium carbonate, with an average of 82.1% CaCO3 in Florida Bay compared with 71.3% in Shark Bay. Soils from Shark Bay had, on average, 21% higher organic carbon content and 35% higher phosphorus content than Florida Bay. Further, soils from Shark Bay had lower mean dry bulk density (0.78 ± 0.01 g mL–1) than those from Florida Bay (0.84 ± 0.02 mg mL–1). The most hypersaline regions of both bays had higher organic carbon content in surficial soils. Profiles of organic carbon and phosphorus from Florida Bay indicate that this system has experienced an increase in P delivery and primary productivity over the last century; in contrast, decreasing organic carbon and phosphorus with depth in the soil profiles in Shark Bay point to a decrease in phosphorus delivery and primary productivity over the last 1000 y. The total ecosystem stocks of stored organic C in Florida Bay averages 163.5 MgCorg ha–1, lower than the average of 243.0 MgCorg ha–1 for Shark Bay; but these values place Shark and Florida Bays among the global hotspots for organic C storage in coastal ecosystems.

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