Higher Carbon Dioxide Research Articles

Seasonal indoor air quality, self-reported health and comfort amongst tenants living at Danish multi-family social housing sites

Studies have identified seasonal differences between the indoor environment and residents’ comfort, as well as an association between indoor air quality (IAQ) and residents’ overall health. Furthermore, measured IAQ is not always aligned with perceived IAQ. The HOME-Health study is a cross-sectional study with seasonal measurements of IAQ amongst residents living in social housing. The aim is to describe and analyse measured and perceived IAQ, and residents’ health symptoms. We found a lower relative humidity, temperature (TP) and air change level (h−1) level, and a higher carbon dioxide (CO2) level during winter compared to summer. In general, higher IAQ levels were measured in apartments with increased crowdedness. The inability to be able to create cross ventilation increased TP, and a larger number of rooms decreased TP. Overall, there was no clear alignment between measured and perceived IAQ, but we found a trend that higher CO2-levels led to a perception of poor IAQ especially during summer. Overall, draught and thermal discomfort were the most common complaints. Self-reported humidity was increased during winter and was associated with nasal and respiratory symptoms, whereas self-reported humidity during summer was associated with fatigue and dermal symptoms. Findings show challenges with IAQ in Danish social housing that are associated with negative health issues.

The Role of Macronutrients in Chronic Obstructive Pulmonary Disease: A Review

The incidence of chronic obstructive pulmonary disease (COPD) is rising and is still regarded as one of the challenging medical issues. Regardless of the main relationship between tobacco smoking and toxic particle exposure with COPD, factors like nutritional status also play an important role in COPD progression and outcome, as the factor is an adaptable aspect. Malnutrition, sarcopenia, and obesity are nutritional problems that are often encountered in COPD patients. Macronutrients, namely carbohydrates, fat, and protein, support the adjunctive treatment options for COPD. The ideal dietary pattern includes low carbohydrates, medium fats preferably polyunsaturated fatty acids (PUFA), and high proteins to improve COPD symptoms, preserve muscle mass, and delay disease progression. High carbohydrate intake might also increase the respiratory quotient (RQ) which results in higher carbon dioxide (CO2) production and oxygen (O2) demand compared to fat and protein intake. Daily calorie intake should be adjusted to personal nutritional status. Higher calories in malnourished, sarcopenic patients and targeted weight loss in obese patients show improvements in lung function, frequency of exacerbations, and hospitalization rate. In obese individuals with COPD, however, maintaining a slightly higher body mass index (BMI) of 25-30 kg/m2 was associated with lower mortality. This literature review summarized the significant role of macronutrients in COPD patients and the practical approach to macronutrient intervention in individuals with different nutritional statuses.

Part-load thermal efficiency enhancement in gas turbine combined cycles by exhaust gas recirculation

Gas turbine power plants are popular for offshore power generation due to high power density and their reliability. However, growing usage of renewable energies put gas turbines in a load following backup operation. These power plants suffer part-load efficiency losses when operating at less than full capacity, resulting in higher carbon dioxide (CO2) emission from natural gas combined cycles or higher consumption of carbon-free fuels in decarbonized gas turbines. In this article, a solution is proposed for enhancement of power plant part-load thermal efficiency based on exhaust gas recirculation in the gas turbine cycle. Recirculating exhaust gas into the gas turbine have been studied by several researchers and engineers due to its benefit for carbon-free combustion and carbon capture mechanisms. The proposed operation strategy is evaluated for single-spool and two-spool gas turbines operating jointly with a steam bottoming cycle harvesting the waste heat for further power production. In the suggested strategy, eliminating the necessity to cool down the recirculated gas resulted in less equipment footprint for the power plant which makes it more favorable for offshore applications. An in-house design and simulation tool is developed for evaluating gas turbines with modern gas recirculating systems and a flexibility in operation with carbon-free fuel mixtures. The enhancement in efficiency boost, emission reduction, and fuel consumption is quantified demonstrating the improvements with the proposed solution.

Assessing and comparing a DDPG model and GA optimization for a heat and power virtual power plant operating in a power purchase agreement scheme

This paper proposes a deep deterministic policy gradient (DDPG) model for the operation management of a solar power-based virtual power plant (VPP) having a PPA with the grid and supplying power and thermal energy to consumers. The VPP serves to balance the solar power intermittency, cover the demand whenever solar power is absent, and ensure an efficient supply of energy. The literature in this field has introduced optimization algorithms to determine the power plant's output power or heat on a rolling-horizon basis. Using the function approximation category, which involves reinforcement learning with neural networks, to solve the simultaneous thermal and power operation management of VPPs is still not well developed. The challenges imposed in this model are sourced from the non-linearity of the CCHP, the power and thermal balance constraints, and the consideration of continuous variables rather than discrete ones. A case study is simulated in Egypt to assess and compare the models. Compared to the genetic algorithm optimization, the proposed DDPG model achieved 3% more profit, 12% higher carbon dioxide (CO2) emissions, and 9% lower natural gas consumption. The DDPG solution was 57% faster than the GA. The results of the DDPG model proved that machine learning methods could outperform optimization in terms of optimality achievement and speed of solution. The DDPG improved the operation of energy storage units and was able to recognize the supply-demand operational pattern, ensuring the scalability of the VPP to cope with different energy demand levels.

Examination of carbon dioxide emissions and renewables in Southeast Asian countries based on a panel vector autoregressive model

Recently, the increasing energy consumption for economic growth has resulted in higher carbon dioxide (CO2) emissions. In this regard, the reduction of such emissions has become one of the main targets of economic planning for both developed and developing countries. Thus, this study determines whether economic growth and increased energy consumption can have a significant impact on CO2 emissions and whether this relationship is mutual, bidirectional, or unidirectional. For this purpose, we employ a panel autoregressive (VAR) model and focus on a group of developing countries in Southeast Asia in which their economic and population growth are expected to increase CO2 emissions in the future. Additionally, we examine their difficulties in meeting the CO2 emission targets and consider modern renewable energy sources (RES) in our quantitative research. Based on the results, there have been various rebound effects and rising expenses for modern RES in these countries, which have hampered their long-term goal of reducing CO2 emissions. The implication of the findings is that it is important to tailor subsidy schemes and energy policies to the specific needs of developing countries and their respective populations.

Performance analysis of a hybrid system combining cryogenic separation carbon capture and liquid air energy storage (CS-LAES)

Cryogenic separation carbon capture is a promising green carbon emission reduction approach, which is rarely applied due to its high cold energy requirement. This work proposes a hybrid system combining cryogenic separation carbon capture and liquid air energy storage (CS-LAES), comprehensively utilizing low-temperature and high-pressure conditions of LAES to reduce the energy consumption of cryogenic CO2 separation. Flue gas with higher carbon dioxide (CO2) concentrations from coal-fired power plants is compressed in the charging process of CS-LAES instead of air. The CO2 is captured, and the CO2-free air is liquefied and stored for later use. The results demonstrate that the carbon capture energy consumption of the CS-LAES system is 1.12 GJ/ton, which is 0.68 GJ/ton lower than that of conventional cryogenic capture technology (1.80 GJ/ton). The CO2 capture rate of 99.97 % is higher than that of most existing cryogenic CO2 capture technologies. Moreover, the standalone total exergy efficiency (S_TEE) for energy storage of the CS-LAES system was 63.40 %, which is 5.22 % higher than the baseline LAES. Meanwhile, the dynamic payback period of the CS-LAES system is 5.82 years, which is more economical than that of baseline LAES (12.89 years) due to avoiding expensive carbon tax.

Impact of El Niño Southern Oscillation on CO2 and Solar‐Induced Fluorescence Over the Indo‐Pacific Region

AbstractOver the tropical Indo‐Pacific, we explore the variations of Solar‐Induced Fluorescence (SIF), CO2, and precipitation during El Niño Southern Oscillation (ENSO) events verse other times. Based on various data sets, we analyze the time series of deseasonalized precipitation, vertical velocity, SIF, and CO2 across the Indo‐Pacific region. Our analysis reveals that there is less precipitation, more sinking air, lower SIF, and higher carbon dioxide over the Indo‐Pacific region during the El Niño events compared to other times. We also explore the spatial patterns of different variables to gain a deeper understanding of their relationships. The spatial analysis suggests that less precipitation resulting from predominant sinking air not only leads to lower SIF values by reducing photosynthetic activities but also triggers more biomass burning, which contribute to an increase in atmospheric CO2 levels across most areas of the Indo‐Pacific region. The comparative study between observational analyses and numerical simulation by the NOAA CarbonTracker model indicates that the model can simulate the increase of atmospheric column CO2 during the El Niño event, although there are some difficulties in capturing the correct spatial pattern. The results of this study can significantly enhance our understanding of the spatial‐temporal variabilities of atmospheric CO2 concentration and the observational characteristics can be used to enhance models. Furthermore, the complex interactions between ENSO and other variables revealed in this study improve our understanding of how ENSO influences the biosphere and carbon cycle.

Exploration of microbial signature and carbon footprints of the Nilgiri Hill Region in the Western Ghats global biodiversity hotspot of India

Land use change (LUC), alters the multifarious biodiversity hotspots directly and indirectly through the loss of soil quality. A comparative study on soil carbon status and soil microbiome in undisturbed natural forest ecosystems with that of other land uses which gradually altered over time can serve as a suitable indicator for understanding LUC impact on carbon cycles. With this aim, the current investigation was initiated to infer the cyclic effects of LUC on the soil carbon status under six major ecosystems viz., cropland (CL), deciduous forest (DF), evergreen forest (EF), forest plantation (FP), scrubland (SL) and tea plantation (TP) of the Nilgiri Hill Region (NHR) (India's first biosphere reserve). The total organic carbon (TOC) and carbon stocks were highest in evergreen forest (10.25 %, 322.06 t ha−1) and they decreased with increasing depth of the soil profile across the pools of varying carbon lability. The proportion of active carbon pools (AP) in total carbon was higher in crop land and tea plantation (57.47 %, 58.38 %), however, in the case of evergreen forest, deciduous forest, forest plantation and scrub land the passive carbon pools (PP) (54.99 %, 61.28 %, 59.43 % and 60.70 %) was higher. We discovered LUC has altered the proportion of soil carbon pools, and the efficiency of soil microbiome and has resulted in higher carbon dioxide (CO2) emissions in tea plantation (71.87 t ha−1) and crop land (82.39 t ha−1). However, the native ecosystems (evergreen forest and deciduous forest) with higher recalcitrant carbon pools (46.96 g kg−1 and 34.89 g kg−1) prevent such carbon degradation and thereby hinder the soil carbon emissions as recorded in evergreen forest (48.43 t ha−1) and deciduous forest (56.47 t ha−1). Conclusively, our study demonstrates that LUC has substantially influenced the carbon cycle by altering the carbon stocks and CO2 emissions in relation to soil microbes. Henceforth, in order to maintain carbon footprints and attain carbon net neutrality under the current climate change scenario, suitable carbon management measures must be implemented in carbon-degraded ecosystems (crop land and tea plantation) of NHR.

Deciphering large-scale spatial pattern and modulators of dissolved greenhouse gases (CO2, CH4, and N2O) along the Yangtze River, China

The Yangtze River, the third largest river around the globe, has been heavily engineered with a series of hydroelectric dams. Meanwhile, it receives elevated organic matter and nutrient loads from its densely populated catchment, subsequently altering dissolved greenhouse gas (GHG) concentrations along the river. However, the large-scale longitudinal patterns and drivers of GHG concentrations in the Yangtze River remain poorly understood. Using longitudinal sampling design in a 2400 km section, we report dissolved carbon dioxide, methane, and nitrous oxide concentrations along the Yangtze River at 145 sites. We observe significant spatial clustering with higher carbon dioxide and nitrous oxide concentrations in the middle reach of the Yangtze River. The results of nonlinear regression reveal that riverine GHGs are high when wetland coverage is high and dissolved oxygen is low. Wetlands and oxygen, not the Three Gorges Dam and tributaries, are the primary correlates of spatial variations of CO2 and CH4 concentrations, respectively. N2O is surprisingly well predicted by CO2, implying their common drivers or sources. We strongly recommend that wetland contribution to GHG budgets and its sensitivity to environmental change be considered when estimating riverine GHGs in the Yangtze River. In light of our study, future control of GHG emissions from large rivers may largely depend on how external inputs and internal metabolism are regulated by decreasing nutrient loading.

Solar-driven Photocatalyzed Hydrogen Production from Water cleavage: Evaluation and Process Life Cycle Assessment

Hydrogen is proper chemical storage for solar energy and is considered a green and non-pollution energy. The feasibility of solar-driven hydrogen generation from water cleavage is investigated using commercial TiO2 nanoparticles, and the process of life cycle assessment (LCA) is estimated. TiO2 is fully characterized. The results confirm the efficacy of TiO2 for solar-driven photocatalytic water splitting with the same production rate of H2. The maximum calculated photocatalytic rate of hydrogen over PC was 4.76 µmole/h under sunlight. As well the rate of produced H2 is dependent PC dose. There is a signification corelation between Kapp with PC dose with r2 of 0.96. Reaction rate constant for hydrogen production is significantly dependent concentration of TiO2. The outcome emphasized the practical application of solar-driven, cost-effective technology for production renewable energy. Also, LCA study of solar-driven H2 production is showed that higher carbon dioxide and as well as global warming potential with lower climatic change impact originated from operation of system.

Does a Long-Run Relationship Exist between Trade Openness and Carbon Dioxide Emissions in Sri Lanka?

In recent years, the process of globalization has provided a great deal of support to international trade, which has led to the increase in global trade volume. However, as far as the negative characteristics of international trade flows are concerned, the extensive production and trade needed to meet global demands have led to higher energy consumption and higher carbon dioxide (CO¬2) emissions. Sri Lanka has been trading since 1977, so the objective of this study is to investigate the existence of the relationship between trade and carbon dioxide emissions in Sri Lanka. Using annual time series data running from 1980 to 2014, this study employs Johansen’s cointegration method for econometric analysis. The findings of the study derived from the analysis revealed that the intended variables are likely to move together in the long run. The study suggests that reprocessing emissions, pollution prevention actions, and the introduction of low carbon technology in trade can mitigate carbon dioxide emissions.

Does Economic Development Impact CO2 Emissions and Energy Efficiency Performance? Fresh Evidences From Europe

Data from a survey of 21 European nations from 2006 to 2018 investigates the relationship between economic development and carbon dioxide emissions. The PCA of normalised factors is used to create three quantitative measures for financial intermediation dependent on the results of the study. When estimating the framework, we used the Hoechle method, which generates systematic deviation for linear panel styles that really are not homoskedasticity coherent and moreover resistant to broad types of cross-sectional dependency. We observe that earnings, resource utilization, industrialization, urbanisation, foreign direct investment, and the banking system all seem to have contributed to increased carbon dioxide emissions in the area. However, greater economic access appears to have resulted in a reduction in greenhouse gas emissions. In terms of quality, the results are resilient to a variety of alternative proxies for financial inclusions as well as acceptable changes to the conceptual framework. According to the empirical findings, there are currently no regulatory interactions linking increasing economic development and reducing carbon dioxide emissions at the national level. As a result, economic growth should be incorporated into the implementation of sustainable green economy plans at the municipal, provincial, and city levels, particularly to counteract the documented detrimental impact of higher carbon dioxide emissions associated with increased financial inclusion.

Enhancement of Fermentable Sugars Obtained from<i> Amorphophallus</i> Spp. Tuber for Bioethanol Production by Optimizing Temperature and Pretreatment Concentration

Biofuels have been regaining popularity due to the increasing price of non-renewable fuels and the higher carbon dioxide emissions. Biofuels are manufactured from plant products and are mainly composed of lignocellulose and starch materials. This investigation aims to produce increased fermentable sugars for enhanced bioethanol production from tubers procured from northern Thailand. Varying concentrations of H2SO4 is used to pretreat the tubers. Before hydrolyzing with cellulase enzymes, the tubers were chopped into small pieces (1-2 cm), dried in a solar oven, powdered. The obtained results confirmed that the fermentable/ reducing sugar content of Amorphophallus spp. (suweg) tuber increased from 2.6 g/L to 19.01 g/L after enzymatic hydrolysis. The enzymes act as an excellent way to speed up the hydrolysis process. The theoretical potential of bioethanol production was calculated under ideal conditions, with the highest bioethanol concentration obtained is 9.69 ± 0.12 g/L at 0.4 % H2SO4 (pretreatment conc.) and 75 °C. The enhanced fermentable sugars obtained from starchy tubers may be utilized for bioethanol production to overcome depleting fossil fuels.

Topological Analysis of the Carbon-Concentrating CETCH Cycle and a Photorespiratory Bypass Reveals Boosted CO2-Sequestration by Plants.

Synthetically designed alternative photorespiratory pathways increase the biomass of tobacco and rice plants. Likewise, some in planta–tested synthetic carbon-concentrating cycles (CCCs) hold promise to increase plant biomass while diminishing atmospheric carbon dioxide burden. Taking these individual contributions into account, we hypothesize that the integration of bypasses and CCCs will further increase plant productivity. To test this in silico, we reconstructed a metabolic model by integrating photorespiration and photosynthesis with the synthetically designed alternative pathway 3 (AP3) enzymes and transporters. We calculated fluxes of the native plant system and those of AP3 combined with the inhibition of the glycolate/glycerate transporter by using the YANAsquare package. The activity values corresponding to each enzyme in photosynthesis, photorespiration, and for synthetically designed alternative pathways were estimated. Next, we modeled the effect of the crotonyl-CoA/ethylmalonyl-CoA/hydroxybutyryl-CoA cycle (CETCH), which is a set of natural and synthetically designed enzymes that fix CO₂ manifold more than the native Calvin–Benson–Bassham (CBB) cycle. We compared estimated fluxes across various pathways in the native model and under an introduced CETCH cycle. Moreover, we combined CETCH and AP3-w/plgg1RNAi, and calculated the fluxes. We anticipate higher carbon dioxide–harvesting potential in plants with an AP3 bypass and CETCH–AP3 combination. We discuss the in vivo implementation of these strategies for the improvement of C3 plants and in natural high carbon harvesters.

Comparative Effectiveness of Biogas Residue Acidification and Nitrification Inhibitors in Mitigating CO2 and N2O Emissions from Biogas Residue-Amended Soils

Owing to their high carbon and nitrogen contents, biogas residues may lead to higher carbon dioxide (CO2) and nitrous oxide (N2O) emissions from soils. Acidification of biogas slurry and application of nitrification inhibitors (NIs) could mitigate the emission of these gases. An incubation experiment was therefore carried out to investigate the effect of NIs, DMPP (3, 4-dimethylpyrazole phosphate), and PIADIN (active ingredients: 3.00–3.25% 1,2,4-triazole and 1.50–1.65% 3-methylpyrazole), on CO2 and N2O emissions from soils fertilized with biogas residues and acidified biogas residues. Biogas residues produced higher ammonium-nitrogen (NH4+-N) and nitrate-nitrogen (NO3−-N) concentrations in soils which resulted in higher emissions of CO2-C and N2O-N than that from acidified biogas residues. Both DMPP and PIADIN significantly decreased the emissions of CO2-C (8.1–55.8%) and N2O-N (87–98%) and maintained lower NH4+-N and NO3−-N concentrations when compared to control (without nitrification inhibitors). However, the DMPP had a higher reduction capability for CO2-C emissions than PIADIN in acidified biogas residue applied soil. In conclusion, the acidification of biogas residues and application of NIs are effect in reducing gaseous emission from biogas residue fertilized soils and thus could improve the fertilizer effectiveness of the residues.

Effect of elevated carbon dioxide on the fitness traits of Plutella xylostella (L.) (Lepidoptera: Plutellidae)

The life history and fitness parameters of diamondback moth, Plutella xylostella, were studied under ambient (410 ppm) and elevated concentrations (460, 510, 560, and 610 ppm) of carbon dioxide in a Soil–Plant–Atmosphere–Research chamber. The results revealed that the egg and larval durations were significantly longer at 410 ppm and shortened at a higher carbon dioxide concentration of 610 ppm. At elevated concentrations of 560 and 610 ppm, the net reproductive rate (R0) increased to 99.90 and 88.00 numbers per female in a lifetime, respectively. The intrinsic rate of increased (rm ) value was 0.22 per day at 410 ppm; it increased linearly to 0.24, 0.26, 0.30, and 0.31 per day at 460, 510, 560, and 610 ppm, respectively. The fecundity rate increased from 150.86 ± 19.32 eggs (410 ppm) to 196.33 ± 8.63 eggs (560 ppm) on increasing carbon dioxide concentration but decreased to 171.46 ± 6.79 eggs at 610 ppm. These results suggest improved fitness of P. xylostella in the future scenario of global climate change with increasing carbon dioxide concentrations.

Effect of pre-main-post diesel injection strategy on greenhouse gas and nitrogen oxide emissions of natural gas/diesel dual-fuel engine at high load conditions

Natural gas/diesel dual-fuel (NDDF) engine technology is an interesting concept for decreasing greenhouse gas (GHG) emissions of heavy-duty diesel engines. One of the main limitations of this concept is the emissions of unburned methane which is estimated to have a GHG potential factor of 25 – 34 over a 100-year period. Our previous study has shown that a NDDF engine using pre-main-post diesel injection strategy can reduce unburned methane emissions, but yields lower indicated thermal efficiency (ITE) and higher carbon dioxide (CO2) and nitrogen oxides (NOx) emissions compared to that using single diesel injection strategy under high engine load conditions due to the advanced combustion phasing. In this study, the combustion phasing of pre-main-post diesel injection strategy is further optimized with the goal to improve the ITE and reduce the GHG and NOx emissions without compromising the unburned methane emissions when compared to single injection strategy. The results reveal that changing pre diesel injection timing gives more controllability of the combustion phasing than changing the main and post diesel injection timing. A more homogenous premixed mixture of pre injected diesel – natural gas – air retards the combustion phasing which allowed further improvement of the ITE and GHG emissions of NDDF engines while maintaining the low unburned methane emissions feature of the pre-main-post injection strategy. It is found that the optimized pre-main-post diesel injection strategy is able to reduce unburned methane, GHG, and NOx emissions by 13.4%, 1.5%, and 42%, respectively, and increase ITE by 0.37% compared to single injection strategy.

Black soldier fly reared on pig manure: Bioconversion efficiencies, nutrients in the residual material, greenhouse gas and ammonia emissions

There is an increased interest for using insects, such as the black soldier fly, to treat surplus manure and upcycle nutrients into the food system. Understanding the influence that BSFL have on nutrient flows and nutrient losses during manure bioconversion is key for sustainability assessments. Here we quantified and compared nutrient balances, nutrient levels in residual materials and emissions of greenhouse gases and ammonia between manure incubated with black soldier fly larvae (BSFL) and manure without BSFL, during a 9-day experimental period. We obtained high analytical recoveries, ranging between 95 and 103%. We found that of the pig manure supplied, 12.5% of dry matter (DM), 13% of carbon, 25% of nitrogen, 14% of energy, 8.5% of phosphorus and 9% of potassium was stored in BSFL body mass. When BSFL were present, more carbon dioxide (247 vs 148 g/kg of DM manure) and ammonia-nitrogen (7 vs 4.5 g/kg of DM manure) emitted than when larvae were absent. Methane, which was the main contributor to greenhouse gas emissions, was produced at the same levels (1.3 vs 1.1 g/kg of DM manure) in both treatments, indicating the main role that manure microbial methane emissions play. Nitrous oxide was negligible in both treatments. The uptake of nutrients by the larvae and the higher carbon dioxide and ammonia emissions modified the nutrient composition of the residual material substantially relative to the fresh manure. Our study provides a reliable basis to quantify the environmental impact of using BSFL in future life cycle assessments.

Rapid urbanization effects on partial pressure and emission of CO2 in three rivers with different urban intensities

Rapid urbanization has been reported to affect carbon biogeochemical cycle of waterways, contributing to even higher carbon dioxide (CO2) outgassing from rivers to the atmosphere. However, knowledge on the magnitude and extent of the urbanization influence on riverine CO2 dynamics is still limited. In this study, we investigated partial pressure of CO2 (pCO2) and CO2 degassing rate in the surface water of three rivers that drain land areas with varied urban coverages. Field sampling and measurements were conducted in the Taohua, Nan and Puli Rivers in China’s mountainous Three Gorges Reservoir (TGR) area during winter 2018 and summer 2019 to determine the effect of urbanization intensity on riverine CO2 degassing. We found that pCO2 level was significantly higher in the river with increased proportion of urban land. Both pCO2 level and CO2 flux rate of the Taohua River (3872 μatm and 574 mmol m−2 d−1) with the highest urban land coverage were significantly higher than those of the Nan River (1737 μatm and 218 mmol m−2 d−1) and Puli River (1218 μatm and 130 mmol m−2 d−1) that drain less urbanized land areas. No significant seasonal difference in pCO2 was found in these subtropical rivers (2402 ± 1421 vs 2112 ± 1254 μatm in the summer and the winter). Overall, pCO2 was positively correlated with the concentration of chlorophyll-a (Chl-a), nutrients (i.e., TDN and TDP), dissolved organic carbon (DOC) and colony-forming units (CFU), and was negatively correlated with pH and dissolved oxygen (DO). We found that pH and DOC loading were the better parameters for predicting pCO2 in the river draining more urbanized land area, and pH and Chl-a were the better parameters for predicting pCO2 in the river draining less urbanized area. These findings highlight the role that urbanization plays in increasing riverine pCO2 through increasing nutrient and DOC inputs from the drainage basin under urban development.

Mineral Nutrients, Organic Amendment, and Water Impact Decomposition of Biodegradable Containers Under Controlled Conditions

Laboratory studies were conducted to evaluate effect of soil water content, organic soil amendment, and mineral nutrient application on decomposition of three types of biodegradable containers: recycled paper, wood pulp fiber, and coconut coir over 182 days. Soil respiration was assessed through alkaline trap and titration method to determine decomposition of biodegradable containers. Percentage of carbon content remaining in the container material after 182 days was also quantified. Relative to soil water content, recycled paper containers under 40% water holding capacity (WHC) had higher carbon dioxide released than 60%WHC. Carbon analysis indicated that less carbon remained for all container types under 60% than 40%WHC. For recycled paper and coconut coir pots, treatments receiving container and soil amendment had significantly increased soil respiration. Post-experiment carbon analysis revealed less carbon remained in the recycled paper, wood pulp fiber, and coconut coir containers in the absence of organic soil amendment. For coconut coir, the interaction of container × mineral nutrients appeared to increase soil respiration with higher carbon dioxide released under biodegradable container × low mineral nutrient. This study suggests that cultural practices (i.e., irrigation and organic matter amendment) could facilitate degradation for certain biodegradable container types; however, to provide extensive cultural practice recommendations regarding biodegradable containers, more research is needed.