Potential CO
leakage is a major concern for carbon capture and storage (CCS). The effects of high soil CO
concentration on microbes is a major element of impact assessments of CO
leakage on ...terrestrial ecosystems. We conducted a field experiment to investigate the responses of microbial functional groups of ammonia-oxidizers, methanogens, and methanotrophs in high soil CO
conditions. A single-point injection gassing plot (2.5 m × 2.5 m in size), which had 52.2% CO
in the center (radius = 0.5 m) and 5.5% in the edge (radius = 1.7 m) at 10 cm depth, was employed. N
O and CH
emissions increased after 1 day of injection because injected CO
was instantly utilized by nitrifiers and methanogens. This suggests that the activities of the selected microbes could be stimulated by high soil CO
concentrations. Prolonged CO
injection has toxic effects on aerobic nitrifiers, but may favor anaerobic methanogens. However, the early stimulatory effects of high soil CO
on N
O and CH
production did not last to the end of injection. These results imply that increased N
O and CH
emissions could be the minor side effects of high soil CO
. Microbes responded faster than plants to high soil CO
, with responses observed as late as 7 days after injection. The inhibition of plant absorption of soil water and nutrients by high soil CO
concentrations may also influence microbial responses. Moreover, high soil water content could retard underground CO
diffusion, which would magnify CO
impacts on plants and microbes. Our results suggest that microbial response could be used as an early indicator of the impact assessments of CO
leakage on soil ecosystems. An understanding of the interaction among soils, plants, and microbes would be helpful in assessing the biological risks of potential CO
leakage.
Carbon capture and storage (CCS) technology, a process consisting of the separation and capture of CO sub(2) from point sources and injection into deep geological reservoirs for long-term isolation ...from the atmosphere, is considered to be a promising technology that can mitigate global climate change. However, the risk of CO sub(2) leakage from storage sites exists, and thus its impact on ecosystem functions needs to be understood for safe implementation of CCS. Plant and microbial parameters were monitored in artificial CO sub(2) release experiments in the field and in greenhouses. In addition, plants and microorganisms were monitored in CO sub(2) storage sites. We review the findings from these studies and suggest directions of future research for determining the impact of potential CO sub(2) leakage from CCS sites on plants and microorganisms. Our review showed that under high levels of soil CO sub(2), (i) plant stress response was visible within short period of time; (ii) dicots were more sensitive than monocots in most studies; and (iii) the responses of microorganisms were more diverse and harder to generalize than those of plants. Only a limited number of field and greenhouse experimental studies have been conducted so far, and thus more field and greenhouse experimental studies are needed to better understand the plant and microbial response to elevated soil CO sub(2) levels and elucidate specific mechanisms underlying these responses. Determining the ecological impacts of geological CO sub(2) storage and ensuring its environmental safety via such research will make CCS a more viable technology. copyright 2016 Society of Chemical Industry and John Wiley & Sons, Ltd
Nutrient removal from artificial wastewater in autotrophic condition by the co-culture consortium of
Scenedesmus dimorphus
and nitrifiers was investigated. The batch experiments of co-culture,
S. ...dimorphus
- and nitrifiers-only treatments were conducted and compared for 9 days. As a result, the co-culture system showed enhancement in both nitrogen (N) and phosphorous (P) removal compared to each single culture. Especially, total N removal efficiency and P removal efficiency in co-culture reactor were enhanced 3.4 and 6.5 times compared to nitrifiers-only reactor, respectively. This result implies that post-treatment systems such as denitrification of nitrate and luxury uptake of P can be deducted by using the co-culture consortium of
Scenedesmus dimorphus
and nitrifiers. In addition, unlike nitrifiers-only reactor, the co-culture maintained high Dissolved Oxygen (DO) without external aeration. Thus it is suggested that co-culture of
Scenedesmus dimorphus
and nitrifiers is an efficient and economic method to removal nutrient from wastewater.
Carbon (C) sequestration potential of biochar should be considered together with emission of greenhouse gases when applied to soils. In this study, we investigated CO2 and N2O emissions following the ...application of rice husk biochars to cultivated grassland soils and related gas emissions tos oil C and nitrogen (N) dynamics. Treatments included biochar addition (CHAR, NO CHAR) and amendment (COMPOST, UREA, NO FERT). The biochar application rate was 0.3% by weight. The temporal pattern of CO2 emissions differed according to biochar addition and amendments. CO2 emissions from the COMPOST soils were significantly higher than those from the UREA and NO FERT soils and less CO2 emission was observed when biochar and compost were applied together during the summer. Overall N2O emission was significantly influenced by the interaction between biochar and amendments. In UREA soil, biochar addition increased N2O emission by 49% compared to the control, while in the COMPOST and NO FERT soils, biochar did not have an effect on N2O emission. Two possible mechanisms were proposed to explain the higher N2O emissions upon biochar addition to UREA soil than other soils. Labile C in the biochar may have stimulated microbial N mineralization in the C-limited soil used in our study, resulting in an increase in N2O emission. Biochar may also have provided the soil with the ability to retain mineral N, leading to increased N2O emission. The overall results imply that biochar addition can increase C sequestration when applied together with compost, and might stimulate N2O emission when applied to soil amended with urea.
Although a meta-analysis on biochar's effects on N
O emission reported an overall reduction in N
O emission by adding biochar to the soils, there are still variations in the changes in N
O emission, ...especially from field results. The objectives of this study are 1) to compare the effects of biochar addition on N
O emission between three agricultural upland field experiments, where soil water status was dry favoring nitrification and 2) to identify main factors explaining biochar's variable effects on N
O emission. Three field experiments were conducted: Exp A in the cultivated grassland treated with rice husk biochar at 2 ton ha
+ urea (CHAR) and with urea only (CON); Exp B in the cabbage field with CHAR and CON treatments; and Exp C in the pepper field with CHAR, CON, and CHAR + DCD (dicyandiamide, nitrification inhibitor) treatments. In Exp A and C, cumulative N
O emissions significantly increased by 82.5% and 55.8% in the CHAR than CON treatments, respectively, while in Exp B, there was no difference in cumulative N
O emission between the CHAR and CON. Based on results from using nitrification inhibitor and soil % water filled pore space (WFPS), we assumed that the main N
O production mechanism was nitrification. Our results suggest that soil water status right after urea application is the primary determinant of different effects of biochar on N
O emission in addition to soil C status and biochar's adsorption. Principal component analysis using the 25 compiled data also supported our results. This study identified the specific field conditions under which biochar could have stimulating effects on N
O emission. Mitigation potential of biochar application should be reconsidered if biochar and urea were amended to dry soils with low C contents.
Atmospheric carbon dioxide (CO
) concentrations is continuing to increase due to anthropogenic activity, and geological CO
storage via carbon capture and storage (CCS) technology can be an effective ...way to mitigate global warming due to CO
emission. However, the possibility of CO
leakage from reservoirs and pipelines exists, and such leakage could negatively affect organisms in the soil environment. Therefore, to determine the impacts of geological CO
leakage on plant and soil processes, we conducted a greenhouse study in which plants and soils were exposed to high levels of soil CO
. Cabbage, which has been reported to be vulnerable to high soil CO
, was grown under BI (no injection), NI (99.99% N
injection), and CI (99.99% CO
injection). Mean soil CO
concentration for CI was 66.8-76.9% and the mean O
concentrations in NI and CI were 6.6-12.7%, which could be observed in the CO
leaked soil from the pipelines connected to the CCS sites. The soil N
O emission was increased by 286% in the CI, where NO
-N concentration was 160% higher compared to that in the control. This indicates that higher N
O emission from CO
leakage could be due to enhanced nitrification process. Higher NO
-N content in soil was related to inhibited plant metabolism. In the CI treatment, chlorophyll content decreased and chlorosis appeared after 8th day of injection. Due to the inhibited root growth, leaf water and nitrogen contents were consistently lowered by 15% under CI treatment. Our results imply that N
O emission could be increased by the secondary effects of CO
leakage on plant metabolism. Hence, monitoring the environmental changes in rhizosphere would be very useful for impact assessment of CCS technology.
Background: Soil microorganisms play key roles in nutrient cycling and are distributed throughout the soil profile. Currently, there is little information about the characteristics of the microbial ...communities along the soil depth because most studies focus on microorganisms inhabiting the soil surface. To better understand the functions and composition of microbial communities and the biogeochemical factors that shape them at different soil depths, we analyzed microbial activities and bacterial and fungal community composition in soils up to a 120 cm depth at a fallow field located in central Korea. To examine the vertical difference of microbial activities and community composition, ${\beta}$-1,4-glucosidase, cellobiohydrolase, ${\beta}$-1,4-xylosidase, ${\beta}$-1,4-N-acetylglucosaminidase, and acid phosphatase activities were analyzed and barcoded pyrosequencing of 16S rRNA genes (bacteria) and internal transcribed spacer region (fungi) was conducted. Results: The activity of all the soil enzymes analyzed, along with soil C concentration, declined with soil depth. For example, acid phosphatase activity was $125.9({\pm}5.7({\pm}1SE))$, $30.9({\pm}0.9)$, $15.7({\pm}0.6)$, $6.7({\pm}0.9)$, and $3.3({\pm}0.3)nmol\;g^{-1}\;h^{-1}$ at 0-15, 15-30, 30-60, 60-90, and 90-120 cm soil depths, respectively. Among the bacterial groups, the abundance of Proteobacteria (38.5, 23.2, 23.3, 26.1, and 17.5% at 0-15, 15-30, 30-60, 60-90, and 90-120 cm soil depths, respectively) and Firmicutes (12.8, 11.3, 8.6, 4.3, and 0.4% at 0-15, 15-30, 30-60, 60-90, and 90-120 cm soil depths, respectively) decreased with soil depth. On the other hand, the abundance of Ascomycota (51.2, 48.6, 65.7, 46.1, and 45.7% at 15, 30, 60, 90, and 120 cm depths, respectively), a dominant fungal group at this site, showed no clear trend along the soil profile. Conclusions: Our results show that soil C availability can determine soil enzyme activity at different soil depths and that bacterial communities have a clear trend along the soil depth at this study site. These metagenomics studies, along with other studies on microbial functions, are expected to enhance our understanding on the complexity of soil microbial communities and their relationship with biogeochemical factors.
Soil organic carbon (SOC) mineralization is influenced by soil structure such as pore size distribution and aggregation, both of which result in heterogeneity in the distribution of soil water and ...microbial activity. This study investigated the effects of soil structure and its interaction with soil water content on C mineralization. Dry aggregate samples (0–2, 2–4, 4–8, 8–16 mm) obtained from agricultural field (AGRIC) and an adjacent less-disturbed area maintained under prairie vegetation (PRAIRIE) were subjected to a short-term incubation where soil water was maintained at four gravimetric water contents ranging from 5% to 50%. More water was needed to maximize C mineralization in larger sized aggregates supporting the notion that biological activity is located at the surface of aggregates or within pores located adjacent to their surface. Mean C mineralization rate was 54% greater from the PRAIRIE than the AGRIC soils, which contained 66.1 and 24.9 mg SOC g
−
1
soil, respectively. However, mean specific C mineralization rates (mg C–CO
2
/
mg-SOC ) were 45% lower from the PRAIRIE than from the AGRIC treatment, suggesting that physical protection of SOC was greater in that soil. The greater volume of macropores (>
300 μm) in the PRAIRIE aggregates may have contributed to its accumulation of humified SOC by limiting microbial usage of C in air filled pores. The volume of water holding pores (<
30 μm), which was lower in the aggregates from the PRAIRE than AGRIC treatment, was saturated in the PRAIRE aggregates at the wettest treatment. As a result, localized anaerobism restricted C mineralization in the PRAIRE but not in the AGRIC aggregates where water holding pores were not yet saturated. Differences in size distribution of pores in aggregates collected from the two soils considered affected the physical availability of substrates and optimum soil water conditions for biological activity. By considering macropores as regions of where C decay is restricted and by assessing the status of pores
<
30 μm (water held at −
10 kPa), we can better understand spatial constraints on C mineralization.
The influence of tillage practices on soil organic carbon (SOC) dynamics is manifested indirectly through the modification of soil structure. This study was conducted at two sites in Illinois where ...long-term use of conventional (CT) and no tillage (NT) practices has increased SOC at Monmouth, a silt loam, but not at DeKalb, a silty clay loam soil with higher SOC contents. We evaluated whether soil structural quality could be related to observed SOC mineralization and explain the inconsistent influence of tillage on SOC stocks. Soil physical parameters and soil CO2 evolution rates were measured in 2000, 2001, and 2002. At DeKalb, there was no difference in the mean (micromol m(-1) s(-1)) or specific (microgram CO2 s(-1)/microgram SOC) SOC mineralization rates of NT and CT soils. In Monmouth, mean and specific SOC mineralization rates were greater from soils under CT than NT management. This indicates use of NT practices had increased physical protection of SOC at that site. The Q10 equation, which is based on soil temperature and moisture, better explained CO2 efflux in DeKalb than in Monmouth. The poorer fit of the equation in Monmouth reflects its reliance on gravimetric moisture content, which inadequately describes the status of soil water influencing heterotrophic activity. The least limiting water range (LLWR), which integrates the affects of clay content, bulk density, and soil moisture on biological activity and predicted observed soil CO2 efflux patterns (R = 0.600, p = 0.0025) better than any other physical parameter, indicated use of NT practices at Monmouth increased soil compaction or strength enough to reduce C mineralization. In DeKalb, where soils have an inherently high capacity to protect SOC from decay, tillage has had no influence on SOC dynamics. The variable affect of tillage practices on C sequestration were explained by soil physical properties.
Rising levels of atmospheric CO sub(2) may stimulate forest productivity in the future, resulting in increased carbon storage in terrestrial ecosystems. However, heavy metal contamination may ...interfere with this, though the response is not yet known. In this study, we investigated the effect of elevated CO sub(2) and Pb contamination on microorganisms and decomposition in pine tree forest soil. Three-year old pine trees (Pinus densiflora) were planted in Pb contaminated soils (500 mg/kg-soil) and uncontaminated soils and cultivated for three months in a growth chamber where the CO sub(2) concentration was controlled at 380 or 760 mg/kg. Structures of the microbial community were comparatively analyzed in bulk and in rhizosphere soil samples using community-level physiological profiling (CLPP) and 16S rRNA gene PCR-DGGE (denaturing gradient gel electrophoresis). Additionally, microbial activity in rhizospheric soil, growth and the C/N ratio of the pine trees were measured. Elevated CO sub(2) significantly increased microbial activities and diversity in Pb contaminated soils due to the increase in carbon sources, and this increase was more distinctive in rhizospheric soil than in bulk soils. In addition, increased plant growth and C/N ratios of pine needles at elevated CO sub(2) resulted in an increase in cation exchange capacity (CEC) and dissolved organic carbon (DOC) of the rhizosphere in Pb contaminated soil. Taken together, these findings indicate that elevated CO sub(2) levels and heavy metals can affect the soil carbon cycle by changing the microbial community and plant metabolism.
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