Daily Carbon Research Articles

Transport most likely to cause air pollution peak exposures in everyday life: Evidence from over 2000 days of personal monitoring

BackgroundAir quality standards are typically based on long term averages – whereas a person may encounter exposure peaks throughout the day. Exposure peaks may contribute meaningfully to health impacts beyond their contribution to long term averages, and therefore should be considered alongside longer-term exposures. We aim to define and explain peak exposure to black carbon air pollution and look at the relationship between short peak exposures and longer term personal exposure. MethodsA peak detection algorithm was applied to pooled data from two independent studies. High-resolution personal black carbon monitoring was performed in 175 healthy adult volunteers for a minimum of two 24-h periods per person. At the same time, we retrieved information on the time-activity pattern. Data covered Belgium, Spain, and the United Kingdom. In total, 2053 monitoring days were included. ResultsExposure profiles revealed 2.8 ± 1.6 (avg ± SD) peaks per person per day. The average black carbon concentration during a peak was 4206 ng/m³. On 5.5% of the time participants were exposed to peak concentrations, but this contributed to 21.0% of their total exposure. The short time in transport (8%), was responsible for 32.7% of the peaks. 24.1% of the measurements in transport were categorized as peak exposure; while sleeping this was only 0.9%. When considering transport modes, participants were most likely to encounter peaks while cycling (34.0%). Most peaks were encountered at rush hour, from Monday through Friday, and in the cold season. Gender and age had no impact on the presence of peaks. Daily average black carbon exposure showed only a moderate correlation with peak frequency (r = 0.44). This correlation coefficient increased when considering longer term exposure to r > 0.60 from 10 days onward. ConclusionsThe occurrence of peaks varied substantially over time, across microenvironments and transport modes. Daily average exposure was moderately correlated with peak frequency. Real-time air pollution alerting systems may use the peak detection algorithm to support citizens in self-management of air pollution health effects.

Physiological tipping points to light reduction underlie seagrass population collapse and abrupt shift in a shallow coastal lagoon

Physiological tipping points to light reduction underlie seagrass population collapse and abrupt shift in a shallow coastal lagoon

Degradable Carbon Dots from Cigarette Smoking with Broad-Spectrum Antimicrobial Activities against Drug-Resistant Bacteria.

Infection of pathogenic bacteria and the abuse of antibiotics are the main factors in worldwide health issues. A number of nanomaterials have been fabricated to directly battle drug-resistant bacteria. However, few studies have referred to the relation between common daily carbon nanoparticles (e.g., automobile exhaust and cigarette smoke) and antimicrobial activities. Herein, carbon dots (CDs) extracted from cigarette smoke are introduced, showing low in vivo and in vitro toxicity. These CDs show broad-spectrum antimicrobial activities that originate from the destruction of the double helix structure of DNA. CDs can degrade to smaller particles and organic fragments with the existence of horseradish peroxidase (HRP) and H2O2 in 7 days, during which CDs can function as an effective antibiotic within the early days and then gradually degrade and lose the antimicrobial effects until finally being eliminated through metabolism. Our findings relate common daily carbon nanoparticles from cigarette smoke with antimicrobial activities, suggesting that the CDs can function as an effective broad-spectrum antibiotic, even against drug-resistant bacteria.

Similarity and heterogeneity of price dynamics across China’s regional carbon markets: A visibility graph network approach

Similarity and heterogeneity analysis of price dynamics across the region provide experiences for China’s national carbon emission trading scheme. This study examines the dynamic behavior of carbon prices from the visibility graph network point of view, notably introducing the Jaccard coefficient to measure the similarity. By mapping daily carbon trading prices onto visibility graph networks, we analyze the characteristics of the carbon prices by topological measures of the networks. For the next step, we evaluate the similarity between pilots by the Jaccard similarity coefficient of the constructed visibility graph networks. Consequently, we cluster the pilots based on topology measures of the networks. Results show that the seven carbon markets in China have different patterns of similarity in visibility network properties: They are all small-world networks and are scale-free except for Chongqing pilot. Only Hubei and Shenzhen pilots are assortative, indicating a weak degree of market efficiency. At the same time, the two pilots have the highest value of Jaccard similarity coefficients and Shenzhen pilot presents the highest similarity to the supposed integrated market. According to the structure measures of the networks, the pilots are clustered into four groups which can be seen as sub-markets. Findings in this study indicate that inequalities across those groups should be sufficiently considered in the future national carbon market with particular emphasis on the Hubei pilot. Some sub-markets are suggested to be built according to the similarity in price dynamics.

Trophic Characteristics of Mnemiopsis leidyi and Its Impact on the Plankton Community in Black Sea Coastal Waters

The quantitative development of Mnemiopsis leidyi, the species structure of mesoplankton, and the food spectrum of ctenophores were studied in the shelf zone off the Crimean coast of the Black Sea during the summer seasons of 2013 and 2014. The feeding rate of the M. leidyi population and its predation pressure on the entire zooplankton community and certain species populations have been estimated from data on the diet composition, digestion time, and abundance of ctenophores. The volume of water cleared by M. leidyi varies by more than an order of magnitude depending on the systematic affiliation of the organisms consumed: it is maximum in the case of preying on Cladocera and Bivalvia veligers (up to 12 L ind.–1 h–1) and significantly lower for Copepoda (0.4–2.0 L ind.–1 h–1). The relationship between the value of the specific daily ration and carbon content in a M. leidyi body in the summer months of 2013 and 2014 is described by a parabolic equation with an exponent of –0.346 to –0.852. In 2014, the highest predation pressure, compared to other groups, was exerted on Copepoda and veligers of Bivalvia (on average 2.9 ± 1.5 and 2.2 ± 0.7% of biomass per day). The mean daily rate of predation on zooplankton in the Black Sea coastal zone was lower in 2014 (1.54 ± 0.58%) than in 2013 (3.94 ± 1.2% of zooplankton biomass) due to the low abundance of ctenophores. A comparative analysis of long-term data on the trophic role of the ctenophore in the plankton community has shown that the food spectrum, as well as the rate of predation on certain groups, varies from year to year. The low rate of predation on forage zooplankton by the M. leidyi population in recent years (2–5% of biomass per day) does not influence the interannual zooplankton dynamics in Black Sea coastal waters.

Traffic-related air emissions in Houston: Effects of light-rail transit

Recent studies have suggested that automobile pollution poses significantly more harmful health impacts than previously realized. Light-rail transit (LRT) is a major type of transportation infrastructure, but there has been little research assessing the air quality effects of LRT based on the actual air pollution data. This study aimed to assess the effects of LRT on automobile-related air emissions in Houston. Specifically, we examined the effects of LRT on key tailpipe pollutants-carbon monoxide and acetylene-as well as other traffic pollution surrogates referred to as BTEX (benzene, toluene, ethylbenzene, and xylene), measured from ambient air monitoring stations.An interrupted time series design and analysis was used to determine the impact of an intervention, where the intervention was the opening of an LRT on January 1, 2004, with two years (2002−2003) of before and two years (2004–2005) of after period data. We found that, after controlling for weather, the opening of the LRT was associated with statistically significant reductions in traffic-related air emissions. Specifically, at the exposure sites, the daily maximum carbon monoxide level was reduced roughly by 24%, and the daily level of toluene was reduced roughly by 60% (33% after accounting for the reduction at the comparison site). Our findings lend support to the air quality benefits of LRT by providing suggestive evidence of positive effects of LRT based on actual air pollution monitoring data. This study's findings also emphasize the importance of developing effective measures to assess traffic-related pollution and call for advanced data collection strategies of additional data, including traffic volume and speed data.

Estimating Grazing Potentials in Sudan Using Daily Carbon Allocation in Dynamic Vegetation Model

Livestock production is important for local food security and as a source of income in sub-Saharan Africa. The human population of the region is expected to double by 2050, and at the same time climate change is predicted to negatively affect grazing resources vital to livestock. Therefore, it is essential to model the potential grazing output of sub-Saharan Africa in both present and future climatic conditions. Standard tools to simulate plant productivity are dynamic vegetation models (DVMs). However, as they typically allocate carbon to plant growth at an annual time step, they have a limited capability to simulate grazing. Here, we present a novel implementation of daily carbon allocation for grasses into the DVM Lund-Potsdam-Jena General Ecosystem Simulator (LPJ-GUESS) and apply this to study the grazing potential for the Kordofan region in Sudan. The results show a latitudinal split in grazing resources, where the northern parts of Kordofan are unexploited and southern parts are overused. Overall, we found that the modeled grazing potential of Kordofan is 16% higher than the livestock usage reported in the Food and Agricultural Organization of the United Nations, indicating a mitigation potential in the form of a spatial relocation of the herds.

Water-use efficiency is higher in green stems than in leaves of a tropical tree species

Stems have similar photosynthetic rates as leaves but higher water-use efficiency. Plants with green photosynthetic stems are common in sub-tropical and tropical dry woodlands worldwide, yet the benefits of photosynthetic stems in tropical species have not been studied before. Parkinsonia praecox (Ruiz & Pav. ex Hook.) Hawkins (Fabaceae) is a small tree found in the arid and semi-arid regions of northern Venezuela and has green stems. We evaluated ecophysiological traits and the role of the photosynthetic stem in the carbon gain of P. praecox in a tropical dry forest, by measuring seasonal changes in water status, gas exchange, water-use efficiency (WUE), photochemical activity of PSII, and biochemical, morphometric and functional traits of leaves and green stems. We found stem net photosynthesis with a rate of 17 µmol m−2 s−1, indicating that the stem contribution to the carbon balance of the species is positive. We also found 1.6 and 2.5 times higher instantaneous and intrinsic WUE, respectively, in green stems than in leaves during the rainy season, which has important implications for water balance. Drought had a negative effect on water potential, leaf PN and photochemical activity of the stem. A similar contribution to the daily whole-plant carbon gain by each photosynthetic organ was found during both seasons; however, when leaf loss is complete during the dry season, the stem contribution would increase up to 100%.

Spatial differentiation of daily travel carbon emissions in small- and medium-sized cities: An empirical study in Kaifeng, China

Abstract Issues relating to low-carbon transportation have received increasing attention in recent years for two competing reasons: the effort to slow down global warming and the upward trend in private vehicle ownership in China. Residential carbon emissions and the mechanisms influencing them have been adequately addressed by the published literature. However, both the built environment and socio-economic factors are spatially heterogeneous within cities, and this can be expected to lead to a corresponding spatial heterogeneity in residential carbon emissions. To better characterize spatial heterogeneity in the mechanisms influencing carbon emissions, this study collected fine-scale spatially-distributed data pertaining to carbon emissions arising from the travel activities of residents in Kaifeng City. The spatial characteristics of and factors influencing household travel carbon emissions were then investigated using spatial auto-correlation analysis and the geographical weighted regression (GWR) method. The results show that areas with high values of household travel carbon emissions were primarily in the new urban development zone and in the more rapidly-expanding built-up areas in the outer layer of the city. Additionally, a large average distance between working and living locations in the newly-built commercial housing communities in the rapidly urbanizing areas is a leading factor increasing resident travel carbon emissions. Meanwhile, the long average distances traveled for schooling on account of the currently imbalanced development of education resources is another leading factor for increasing residential travel carbon emissions. The conclusions of this research elucidate the spatial heterogeneity in the mechanisms influencing residential travel carbon emissions within the city. In particular, this study confirms that urban sprawl is a leading factor in driving residential travel behavior and thus carbon emissions. More importantly, this study demonstrates that the documented inequality in resident travel-related carbon emissions does not result from economic (e.g., household income) inequality. Instead, it is caused by the existence of inequality in the allocation of socioeconomic infrastructure (e.g., schools). It is our expectation that the results of this study can be used as a valuable reference for planning low-carbon cities.

Assimilation of nitrogen and carbon isotopes from fish diets to otoliths as measured by nanoscale secondary ion mass spectrometry.

Nitrogen and carbon stable isotope ratios (δ15 N and δ13 C values) of carbonate-bound organic materials in otoliths can provide information to address the biological and ecological functions of fish. Correct interpretation of otolith δ15 N and δ13 C profiles requires knowledge of the metabolic routes of nitrogen and carbon isotopes. However, the isotopic assimilation of δ15 N and δ13 C compositions from diets to otoliths has rarely been investigated. This study traced the daily nitrogen and carbon isotopic assimilation between diets and otoliths using nanoscale secondary ion mass spectrometry (NanoSIMS). Isotopically labeled algae (Tetraselmis chui) were fed to tilapia (Oreochromis niloticus) for 14-17days. NanoSIMS and conventional isotope ratio mass spectrometry were used to measure δ15 N and δ13 C variations in the otoliths and fish muscle, respectively. Otolith δ15 N values abruptly surged from natural abundance levels by 1000-2300‰ after the fish ate 15 N-spiked algae with δ15 N values of approximately 2200‰. However, the δ15 N values of fish muscle increased to only approximately 500‰ at the end of the feeding experiment. Much higher δ15 N values (3700-14 000‰) and moderate δ13 C values (60-200‰) were detected in the otoliths after the tilapia ate 15 N- and 13 C-spiked algae with a δ15 N value of 36667‰ and a δ13 C value of 272‰. Mapping analysis showed sub-micrometer-scale distribution of 15 N embedded in the otolith growth increments with a low-to-high δ15 N signal after the tilapia shifted diets from non-spiked to 15 N-labeled algae. These results suggest that otolith nitrogen and carbon isotopes from food were directly assimilated on the same day. Food is the major and in some cases only source of otolith nitrogen isotopes but makes only a partial contribution to otolith carbon isotopes. Therefore, the δ15 N values recorded in the sclerochronological layers of the otoliths can be used to determine the trophic levels, food sources and diet changes of fish.

Effects of Light Quality and Intensity on Diurnal Patterns and Rates of Photo-Assimilate Translocation and Transpiration in Tomato Leaves.

Translocation of assimilates is a fundamental process involving carbon and water balance affecting source/sink relationships. Diurnal patterns of CO2 exchange, translocation (carbon export), and transpiration of an intact tomato source leaf were determined during 14CO2 steady-state labeling under different wavelengths at three pre-set photosynthetic rates. Daily patterns showed that photosynthesis and export were supported by all wavelengths of light tested including orange and green. Export in the light, under all wavelengths was always higher than that at night. Export in the light varied from 65–83% of the total daily carbon fixed, depending on light intensity. Photosynthesis and export were highly correlated under all wavelengths (r = 0.90–0.96). Export as a percentage of photosynthesis (relative export) decreased as photosynthesis increased by increasing light intensity under all wavelengths. These data indicate an upper limit for export under all spectral conditions. Interestingly, only at the medium photosynthetic rate, relative export under the blue and the orange light-emitting diodes (LEDs) were higher than under white and red-white LEDs. Stomatal conductance, transpiration rates, and water-use-efficiency showed similar daily patterns under all wavelengths. Illuminating tomato leaves with different spectral quality resulted in similar carbon export rates, but stomatal conductance and transpiration rates varied due to wavelength specific control of stomatal function. Thus, we caution that the link between transpiration and C-export may be more complex than previously thought. In summary, these data indicate that orange and green LEDs, not simply the traditionally used red and blue LEDs, should be considered and tested when designing lighting systems for optimizing source leaf strength during plant production in controlled environment systems. In addition, knowledge related to the interplay between water and C-movement within a plant and how they are affected by environmental stimuli, is needed to develop a better understanding of source/sink relationships.

Urban daily travel carbon emissions accounting and mitigation potential analysis using surveyed individual data

Abstract Our study focuses on the carbon emission and mitigation potential in the domain of daily travel in Beijing. Using a sample with the focus on working class, the average individual carbon emissions from daily travel are computed as 1.46 kg/day•person and 2.40 kg/day•person for weekday and weekend. Except for residents who need to conduct more long-distance trips, the main contributor to the emissions of the rest high emitters are not the need of longer daily travel distances or the need to conduct more long distance trips, but the need to use cars more intensively for trips with similar distances compared with low emitters. High emitters are associated with the characteristics of being male, having higher income, owning cars, and being in the age between 30s and 40s. On the other hand, living within fifth ring and having good accessibility to public transport are associated with lower emissions. We innovatively use trip-based information to obtain a more relevant and realistic assessment of mitigation potential through mode shift under the current transport system. The mitigation percentage can be as high as 20%–25% if only travel time is considered, but will be substantially constrained by practical barriers. Therefore mitigation policy for daily transport should not only focus on improving travel time of low emission modes to comparable levels with cars but also tackle practical barriers for car drivers to use low emission modes.

Recent Primary Production and Small Phytoplankton Contribution in the Yellow Sea during the Summer in 2016

The high nutrient concentration associated with the mixing dynamics of two warm and cold water masses supports high primary production in the Yellow Sea. Although various environmental changes have been reported, no recent information on small phytoplankton contribution to the total primary production as an important indicator for marine ecosystem changes is currently available in the Yellow Sea. The major objective of this study is to determine the small (< 2 μm) phytoplankton contribution to the total primary production in the Yellow Sea during August, 2016. In this study, we found relatively lower chlorophyll a concentrations in the water column than those previously reported in the central waters of the Yellow Sea. Moreover, the overall contribution of small phytoplankton (53.1%) to the total chlorophyll a concentration was considerably higher in this study than that (10.7%) observed previously. Based on the N/P ratio (67.6 ± 36.6) observed in this study, which is significantly higher than the Redfield ratio (16), we believe that phytoplankton experienced P-limiting conditions during the study period. The average daily carbon uptake rate of total phytoplankton in this study was 291.1 mg C m-2 d-1 (± 165.0 mg C m-2 d-1) and the rate of small phytoplankton was 205.7 mg C m-2 d-1 (± 116.0 mg C m-2 d-1) which is 71.9% (± 8.8%) of the total daily carbon uptake rate. This contribution of small phytoplankton observed in this study appears to be higher than that reported previously. Our recent measured primary production is approximately 50% lower than the previous values decades ago. The higher contributions of small phytoplankton to the total chlorophyll a concentration and primary production might be caused by P-limited conditions and this resulted in lower chlorophyll a concentration and total primary production in this study compared to previous studies.

Size-related shifts in carbon gain and growth responses to light differ among rainforest evergreens of contrasting shade tolerance.

Recent work suggests that plant size affects light requirements and carbon balance of juvenile trees, and such shifts may be greater in light-demanding species than in their more shade-tolerant associates. To explore the physiological basis of such shifts, we measured juvenile light interception, carbon gain and growth of four subtropical Australian rainforest trees differing in shade tolerance, comparing individuals ranging from 13 to 238cm in height, across a wide range of understory environments. We hypothesized that even in a standardized light environment, increasing sapling size would lead to declines in net daily carbon gain of foliage and relative growth rates (RGR) of all species, with declines more pronounced in light-demanding species. Crown architecture of individuals was recorded using a 3-dimensional digitizer, and the YPLANT program was used to estimate the self-shaded fraction of each crown and model net carbon gain. Increased sapling size caused a significant increase in self-shading, and significant declines in net daily carbon gain and RGR of light-demanding species, while such ontogenetic variations were minimal or absent in shade-tolerant species. Additionally, differences in the slope of the relationship between light and RGR led to crossovers in RGR among shade-tolerant and light-demanding species at low light. Our results show that the magnitude of ontogenetic variation in net daily carbon gain and RGR can be substantial and may depend on successional status, making it unsafe to assume that young seedling performance can be used to predict or model responses of larger juvenile trees.

Interactions between the Newly Described Small- and Fast-Swimming Mixotrophic Dinoflagellate Yihiella yeosuensis and Common Heterotrophic Protists.

The mixotroph Yihiella yeosuensis is a small- and fast-swimming dinoflagellate. To investigate its protistan predators, interactions between Y.yeosuensis and 11 heterotrophic protists were explored. No potential predators were able to feed on actively swimming Y. yeosuensis cells, which escaped via rapid jumps, whereas Aduncodinium glandula, Oxyrrhis marina, and Strombidinopsis sp. (approximately 150μm in cell length) were able to feed on weakly swimming cells that could not jump. Furthermore, Gyrodinium dominans, Luciella masanensis, and Pfiesteria piscicida were able to feed on heat-killed Yihiella cells, whereas Gyrodinium moestrupii, Noctiluca scintillans, Oblea rotunda, Polykrikos kofoidii, and Strombidium sp. (20μm) did not feed on them. Thus, the jumping behavior of Y.yeosuensis might be primarily responsible for the observed lack of predation. With increasing Yihiella concentration, the growth rate of O.marina decreased, whereas that of Strombidinopsis did not change. However, with increasing Yihiella concentration (up to 530ng C/ml), the ingestion rate of Strombidinopsis on Yihiella increased linearly. The highest ingestion rate was 24.1ng C per predator per d. The low daily carbon acquisition from Yihiella relative to the body carbon content of Strombidinopsis might be responsible for its negligible growth. Thus, Y.yeosuensis might have an advantage over its competitors due to its low mortality rate.

Food Waste Composting in a High Rate Continuous Feed Drum Reactor: Startup and Carbon Balance Analysis

The objective of this work is to investigate the composting of food waste in a continuous feed pilot scale reactor. Food waste, collected daily from university restaurants and canteens, are fed to the composting unit together with wood pellets. During the continuous process the maximum temperature reaches thermophilic levels. The carbon dioxide emission factor is 216 g C kg−1 total solids (TS) per day, while the average oxygen uptake rate is 1245 ± 957 g O2 kg−1 TS per day both based on the daily waste input. The average daily cumulative carbon closure is calculated as −12.5% (±35.2%) with ideal closure of 0%. Inoculation of the final product shows no formation of colonies for total coliforms, Escherichia coli, Enterococcus (E. faecalis, E. faecium, E. durans, and E. hirae) and Pseudomonas (P. aeruginosa). The average respiration activity (AT4) was 12.1 ± 2.14 mg O2 g−1 TS, indicating that the end product is not quite stable and some maturation time may be required, prior to its application as an organic fertilizer.

Estimating Forest Carbon Fluxes Using Machine Learning Techniques Based on Eddy Covariance Measurements

Approximating the complex nonlinear relationships that dominate the exchange of carbon dioxide fluxes between the biosphere and atmosphere is fundamentally important for addressing the issue of climate change. The progress of machine learning techniques has offered a number of useful tools for the scientific community aiming to gain new insights into the temporal and spatial variation of different carbon fluxes in terrestrial ecosystems. In this study, adaptive neuro-fuzzy inference system (ANFIS) and generalized regression neural network (GRNN) models were developed to predict the daily carbon fluxes in three boreal forest ecosystems based on eddy covariance (EC) measurements. Moreover, a comparison was made between the modeled values derived from these models and those of traditional artificial neural network (ANN) and support vector machine (SVM) models. These models were also compared with multiple linear regression (MLR). Several statistical indicators, including coefficient of determination (R2), Nash-Sutcliffe efficiency (NSE), bias error (Bias) and root mean square error (RMSE) were utilized to evaluate the performance of the applied models. The results showed that the developed machine learning models were able to account for the most variance in the carbon fluxes at both daily and hourly time scales in the three stands and they consistently and substantially outperformed the MLR model for both daily and hourly carbon flux estimates. It was demonstrated that the ANFIS and ANN models provided similar estimates in the testing period with an approximate value of R2 = 0.93, NSE = 0.91, Bias = 0.11 g C m−2 day−1 and RMSE = 1.04 g C m−2 day−1 for daily gross primary productivity, 0.94, 0.82, 0.24 g C m−2 day−1 and 0.72 g C m−2 day−1 for daily ecosystem respiration, and 0.79, 0.75, 0.14 g C m−2 day−1 and 0.89 g C m−2 day−1 for daily net ecosystem exchange, and slightly outperformed the GRNN and SVM models. In practical terms, however, the newly developed models (ANFIS and GRNN) are more robust and flexible, and have less parameters needed for selection and optimization in comparison with traditional ANN and SVM models. Consequently, they can be used as valuable tools to estimate forest carbon fluxes and fill the missing carbon flux data during the long-term EC measurements.

Minimum Daily Respiration of Maize: Relationship to Total Daily Respiratory Carbon Loss, and Effects of Growth Stage and Temperature

ABSTRACTSince crop respiration can only be measured in darkness, estimating total daily crop respiration (Rt) requires knowledge of the quantitative relationship between daytime and nighttime respiration, including the predicted effect of temperature. We measured minimum daily (early morning) respiration (Rmin) in maize (Zea mays L.) at four different temperatures during the night and at four different growth stages to estimate the respiration response to temperature. In a field experiment, respiration was measured every 2 to 5 h over a 24‐h period at five different growth stages to explore the relationship between Rt and Rmin. The fractional rate change with 10°C temperature increment (Q10) decreased as the temperature increased. A single function was proposed to describe the respiration response to temperature across all growth stages. The minimum respiration of the day was reached between midnight and 6:00 AM, and Rmin represented 89 to 57% of Rt. Modeling maize respiration assuming a constant Q10 is inadvisable, since Q10 varies with temperature. There was no effect of growth stage on Q10 until 26°C; above this temperature, respiration increased only in older plants. The Rt increased over the season as biomass accumulated, but the ratio of Rmin/Rt reached its highest value at silking.

Ambient carbon monoxide and cardiovascular mortality: a nationwide time-series analysis in 272 cities in China

Evidence of the acute health effects of ambient carbon monoxide air pollution in developing countries is scarce and mixed. We aimed to evaluate short-term associations between carbon monoxide and daily cardiovascular disease mortality in China. We did a nationwide time-series analysis in 272 major cities in China from January, 2013, to December, 2015. We extracted daily cardiovascular disease mortality data from China's Disease Surveillance Points system. Data on daily carbon monoxide concentrations for each city were obtained from the National Urban Air Quality Real-time Publishing Platform. City-specific associations between carbon monoxide concentrations and daily mortality from cardiovascular disease, coronary heart disease, and stroke were estimated with over-dispersed generalised linear models. Bayesian hierarchical models were used to obtain national and regional average associations. Exposure-response association curves and potential effect modifiers were evaluated. Two-pollutant models were fit to evaluate the robustness of the effects of carbon monoxide on cardiovascular mortality. The average annual mean carbon monoxide concentration in these cities from 2013 to 2015 was 1·20 mg/m3, ranging from 0·43 mg/m3 to 2·45 mg/m3. For a 1 mg/m3 increase in average carbon monoxide concentrations on the present day and previous day (lag 0-1), we observed significant increments in mortality of 1·12% (95% posterior interval [PI] 0·42-1·83) from cardiovascular disease, 1·75% (0·85-2·66) from coronary heart disease, and 0·88% (0·07-1·69) from stroke. These associations did not vary substantially by city, region, and demographic characteristics (age, sex, and level of education), and the associations for cardiovascular disease and coronary heart disease were robust to the adjustment of criteria co-pollutants. We did not find a threshold below which carbon monoxide exposure had no effect on cardiovascular disease mortality. This analysis is, to our knowledge, the largest study done in a developing country, and provides robust evidence of the association between short-term exposure to ambient carbon monoxide and increased cardiovascular disease mortality, especially coronary heart disease mortality. Public Welfare Research Program.

Production of Heterotrophic Bacterioplankton in a Large Meso-Eutrophic Reservoir: The Importance of Extracellular Organic Carbon Released by Phytoplankton

The spatial distribution and seasonal dynamics of heterotrophic bacterioplankton production have been studied and the value of autochthonous sources of substrates for bacteria has been evaluated in the pelagic zone of the meso-eutrophic Rybinsk Reservoir (the Upper Volga). During the vegetation period, the bacterial production ranges from 32 to 1352 (on average 444 ± 44) mg C/(m2 × day). The total input of organic carbon from the processes of extracellular production of phytoplankton, viral lysis of prokaryotic cells, and feeding of protists provides 9–64% (32 ± 3% on average) of the daily carbon demand for heterotrophic bacterioplankton.