A Clean and Health-Care-Focused Way to Reduce Indoor Airborne Bacteria in Calf House with Long-Wave Ultraviolet.

Long-term exposure to a relatively high concentration of airborne bacteria emitted from intensive livestock houses could potentially threaten the health and welfare of animals and workers. There is a dual effect of air sterilization and promotion of vitamin D synthesis for the specific bands of ultraviolet light. This study investigated the potential use of A-band ultraviolet (UVA) tubes as a clean and safe way of reducing airborne bacteria and improving calf health. The composition and emission characteristics of airborne bacteria were investigated and used to determine the correct operating regime of UVA tubes in calf houses. Intermittent exceedances of indoor airborne bacteria were observed in closed calf houses. The measured emission intensity of airborne bacteria was 1.13 ± 0.09 × 107 CFU h-1 per calf. Proteobacteria were the dominant microbial species in the air inside and outside calf houses. After UVA radiation, the indoor culturable airborne bacteria decreased in all particle size ranges of the Anderson sampler, and it showed the highest reduction rate in the size range of 3.3-4.7 µm. The results of this study would enrich the knowledge of the source characteristics of the airborne bacteria in intensive livestock farming and contribute to the environmental control of cattle in intensive livestock production.

Estimating airborne trichloramine levels in indoor swimming pools using the well-mixed box model.

Exposure to airborne disinfection by-products, especially trichloramine (TCA), could cause various occupational health effects in indoor swimming pools. However, TCA concentration measurements involve specialized analysis conducted in specific laboratories, which can result in significant costs and time constraints. As an alternative, modeling techniques for estimating exposures are promising in addressing these challenges. This study aims to predict airborne TCA concentrations in indoor swimming pools using a mathematical model, the well-mixed box model, found in the IHMOD tool, freely available on the American Industrial Hygiene Association website. The model's predictions are compared with TCA concentrations measured during various bather load scenarios. The research involved conducting 2-hr successive workplace measurements over 16- to 18-hr periods in four indoor swimming pools in Quebec, Canada. TCA concentrations were estimated using the well-mixed box model, assuming a homogeneous mixing of air within the swimming pool environment. A novel approach was developed to estimate the TCA generation rate from swimming pool water, incorporating the number of swimmers in the model. Average measured concentrations of TCA were 0.24, 0.26, 0.14, and 0.34 mg/m3 for swimming pools 1, 2, 3, and 4, respectively. The ratio of these measured average concentrations to their corresponding predicted values ranged from 0.51 to 1.30, 0.67 to 1.04, 0.57 to 1.14, and 0.68 to 1.49 for the respective swimming pools. In a worst-case scenario simulating the swimming pool at full capacity (maximum bathers allowed), TCA concentrations were estimated as 0.23, 0.36, 0.14, and 0.37 mg/m3 for swimming pools 1, 2, 3, and 4. Recalculated concentrations by adjusting the number of swimmers so as not to exceed the recommended occupational limit concentration of 0.35 mg/m3 gives a maximum number of swimmers of 63 and 335 instead of currently 80 and 424 for swimming pools 2 and 4, respectively. Similarly, for swimming pools 1 and 3, the maximum number of swimmers could be 173 and 398 (instead of the current 160 and 225, respectively). These results demonstrated that the model could be used to estimate and anticipate airborne TCA levels in indoor swimming pools across various scenarios.

Theoretical Threshold for Estimating the Impact of Ventilation on Materials' Emissions.

In new buildings, nonoccupant VOC emissions are initially high but typically decrease within months. Increased ventilation is commonly used to improve indoor air quality, assuming it speeds up VOC off-gassing from materials. However, previous research presents inconsistent results. This review introduces a simplified analytical model to understand the ventilation-emission relationship. By combining factors such as diffusivity, emitting area, and time, the model suggests the existence of a theoretical ventilation threshold beyond which enhanced ventilation has no further influence on emission rates. A threshold of approximately 0.13 L s-1 m-2 emitting area has been found for various VOCs documented in the existing literature, with which the conflicting results are explained. It is also shown that the threshold remains notably consistent across different boundary conditions and model resolutions, indicating its suitability for real-world applications.

Characteristics of second-hand exposure to aerosols from e-cigarettes: A literature review since 2010.

In recent years, the use of electronic vaping products (also named e-cigarettes) has increased due to their appealing flavors and nicotine delivery without the combustion of tobacco. Although the hazardous substances emitted by e-cigarettes are largely found to be much lower than combustible cigarettes, second-hand exposure to e-cigarette aerosols is not completely benign for bystanders. This work reviewed and synthesized findings on the second-hand exposure of aerosols from e-cigarettes and compared the results with those of the combustible cigarettes. In this review, different results were integrated based upon sampling locations such as residences, vehicles, offices, public places, and experimental exposure chambers. In addition, the factors that influence the second-hand exposure levels were identified by objectively reviewing and integrating the impacts of combustible cigarettes and e-cigarettes on the environment. It is a challenge to compare the literature data directly to assess the effect of smoking/vaping on the indoor environment. The room volume, indoor air exchange rate, puffing duration, and puffing numbers should be considered, which are important factors in determining the degree of pollution. Therefore, it is necessary to calculate the "emission rate" to normalize the concentration of pollutants emitted under various experimental conditions and make the results comparable. This review aims to increase the awareness regarding the harmful effects of the second-hand exposure to aerosols coming from the use of cigarettes and e-cigarettes, identify knowledge gaps, and provide a scientific basis for future policy interventions with regard to the regulation of smoking and vaping.

Evaluation of particle generation due to deterioration of flooring in schools.

Particulate matter is harmful to humans. An important indoor source of such particles is the deterioration of floor materials brought about by occupants walking. Accordingly, an experiment was conducted to simulate the deterioration of floor material spacing. Considering a school schedule with repeated semesters and vacations, the experiment was conducted by repeating heat-and-rest cycles. Similar results were obtained for particle emission rates under each condition during the first and second deterioration periods. The PVC tiles generated more particles under aged conditions than under non-aged conditions, whereas the wood generated fewer particles under aged conditions. In addition to the quantitative results, a study was conducted on the characteristics of the generated particles, and the particulate matter found in plastic was confirmed in the PVC tiles. Schools where children are present for more than 6 h a day may be exposed to more particulate matter. Therefore, replacing plastic-based materials with eco-friendly building materials is expected to have long-term health benefits for children.

Effect of farm Hazard Analysis and Critical Control Point (farm HACCP) certification efforts on emissions of volatile organic compounds from livestock sheds in Japan.

"Farm HACCP" incorporates the concept of Hazard Analysis and Critical Control Points (HACCP) into farm animal husbandry and sanitation management to ensure the safety of livestock products and improve productivity. Implementing farm HACCP may reduce the emission of volatile organic compounds (VOCs), which are derived from livestock manure and are responsible for odors, PM2.5 , and photochemical oxidants. In this study, the effects of implementing farm HACCP on the emissions, composition, and environmental impact of VOCs from sheds were evaluated. VOCs in swine, dairy cattle, and hen sheds were measured before and after implementing farm HACCP. After implementing farm HACCP, the concentrations in the sheds were 55%-80% lower than the concentration in the sheds before. Odor activity values decreased in the cattle and hen sheds, whereas they increased in the swine shed. In addition, OH radical reactivity, an indicator of reactivity with OH radicals, decreased in all sheds. Finally, the emission rates of VOCs from each shed were estimated to be 42%-97% lower. These results suggest that implementing farm HACCP can reduce emissions of VOCs from livestock industries.

Variation of PM2.5 and PM10 in emissions and chemical compositions in different seasons from a manure-belt laying hen house.

Particulate matter (PM) emissions from animal houses and the corresponding hazard have raised increasing attention during recent years. In this study, a large-scale manure-belt laying hen house located in Beijing, China was selected as the experimental site for the study of the emission rates (ER) and chemical compositions of PM2.5 and PM10 in 3 seasons, namely, summer, autumn, and winter, to investigate their possible influences on ambient air quality and human health. The results showed that the mean ER from the hen house in summer, autumn, and winter were 9.0 ± 1.7, 2.4 ± 0.7, and 1.9 ± 0.7 mg hen-1 d-1 for PM2.5 (P < 0.05), and 30.7 ± 1.1, 12.8 ± 1.5, and 10.9 ± 0.9 mg hen-1 d-1 for PM10 (P < 0.05), respectively. Moreover, large amounts of secondary inorganic aerosols (SIA) were observed inside the house in summer, accounting for 11.4 and 9.6% of indoor PM2.5 and PM10 mass, respectively, compared with the value of <1.4% in autumn and winter. Among the 31 detected elements in indoor PM, arsenic concentration exceeded the threshold set in legislation. Zn had a notably high concentration of 3,403 to 4,432 ng m-3 in indoor PM10, which was 28 to 71 times higher than that in ambient PM10. The findings suggest that the poultry-raising house emit PM2.5 and PM10 containing SIA and toxic heavy-metal elements such as As and Zn to the ambient with much more emissions in summer than in autumn and winter. Considering the increasing development of poultry-raising farming in China, the potential hazard derived from the exhaust of PM2.5 and PM10 should be focused on, especially during summer.

Emissions and Exposures Associated with the Use of an Inconel Powder during Directed Energy Deposition Additive Manufacturing.

Additive manufacturing (AM) has been linked to potential exposure-related health risks, however, there is a paucity of sufficient research. This study aimed to supply information regarding emissions and exposure during directed energy deposition (DED) AM using inconel 718, with the main constituents being nickel, chromium, and cobalt. By using standardized occupational hygiene methods, the measurement strategy consisted of a combined approach, including powder characterization, particle emission monitoring, and personal exposure monitoring of AM operators. Powder characterization of virgin and used powder indicated no significant difference in particle size, shape, or elemental composition. Particle number emissions ranged between 102 and 105 p/cm3 for submicron particles (<1 µm in size). There was no significant difference in the particle emission rate between the three phases of AM or the two types of DED machines (p > 0.05). The particle emission rate for submicron particles peaked at 2.8 × 109 p/min. Metals of concern to human health were detected during the AM process but were considerably lower than the relevant exposure limits. This study confirms particle emissions, predominantly in the submicron range, above the background concentration during DED AM and, although insignificant in terms of potential health effects, AM operators are exposed to detectable concentrations of the metal constituents of inconel.

Temperature-dependent particle number emission rates and emission characteristics during heating processes of edible oils.

The goal of this research is to investigate the temperature-dependent emission rates of particle numbers and emission characteristics during oil heating. Seven regularly used edible oils were studied in a variety of tests to attain this objective. First, total particle number emission rates ranging from 10 nm to 1 µm were measured, followed by an examination within six size intervals from 0.3 µm to 10 µm. Following that, the impacts of oil volume and oil surface area on the emission rate were investigated, and multiple regression models were developed based on the results. The results showed that corn, sunflower and soybean oils had higher emission rates than other oils above 200 °C, with peak values of 8.22 × 109#/s, 8.19 × 109#/s and 8.17 × 109#/s, respectively. Additionally, peanut and rice oils were observed to emit the most particles larger than 0.3 µm, followed by medium-emission (rapeseed and olive oils) and low-emission oils (corn, sunflower and soybean oils). In most cases, oil temperature (T) has the most significant influence on the emission rate during the smoking stage, but its influence was not as pronounced in the moderate smoking stage. The models obtained are all statistically significant (P < 0.001), with R2 values greater than 0.9, and the classical assumption test concluded that regressions were in accordance with the classical assumptions regarding normality, multicollinearity, and heteroscedasticity. In general, low oil volume and large oil surface area were more recommended for cooking to mitigate UFPs emission.

Country-specific riverine contributions to marine plastic pollution.

Marine plastic debris are mainly derived from land-based sources, and the transport of plastics via global rivers is of great concern. Ample efforts have been made in estimating the land-based contributions of plastic to the global oceans, but quantifying country-specific (and per capita) riverine outflows is an important step toward the development of a globally integrated framework to mitigate marine plastic pollution. To estimate the country-specific riverine contributions to global marine plastic pollution, we built a River-to-Ocean model framework. In 2016, the median annual country-specific riverine plastic outflows and related per capita values for 161 countries varied between 0.76 and 103,000 metric tons (MT) and 0.83-248 g, respectively. India, China, and Indonesia were the top three contributors to riverine plastic outflows, whereas Guatemala, Philippines, and Colombia had the highest per capita riverine plastic outflows. The total riverine plastic outflow from 161 countries was in the range of 0.15-0.53 million MT annually, accounting for 0.4 %-1.3 % of the 40 million MT plastic waste generated yearly by more than seven billion humans. Population, plastic waste generation, and Human Development Index are the dominant factors influencing riverine plastic outflows to global oceans from individual countries. Our findings provide an important basis for launching effective plastic pollution management and control measures in global countries.

Analysis of PEM Water Electrolyzer Failure Due to Induced Hydrogen Crossover in Catalyst-Coated PFSA Membranes.

Polymer electrolyte membrane water electrolysis (PEMWE) is a leading candidate for the development of a sustainable hydrogen infrastructure. The heart of a PEMWE cell is represented by the membrane electrode assembly (MEA), which consists of a polymer electrolyte membrane (PEM) with catalyst layers (CLs), flow fields, and bipolar plates (BPPs). The weakest component of the system is the PEM, as it is prone to chemical and mechanical degradation. Membrane chemical degradation is associated with the formation of hydrogen peroxide due to the crossover of product gases (H2 and O2). In this paper, membrane failure due to H2 crossover was addressed in a membrane-focused accelerated stress test (AST). Asymmetric H2O and gas supply were applied to a test cell in OCV mode at two temperatures (60 °C and 80 °C). Electrochemical characterization at the beginning and at the end of testing revealed a 1.6-fold higher increase in the high-frequency resistance (HFR) at 80 °C. The hydrogen crossover was measured with a micro-GC, and the fluoride emission rate (FER) was monitored during the ASTs. A direct correlation between the FER and H2 crossover was identified, and accelerated membrane degradation at higher temperatures was detected.

Experimental evaluation on liquid area sources: Influence of wind velocity and temperature on the wind tunnel sampling of VOCs emissions from wastewater treatment plants.

The investigation of Volatile Organic Compounds (VOCs) emission from wastewater basins is a challenging issue. In particular, the quantification of an accurate emission rate appears quite tricky, since the release of VOC compounds from this type of source, and the subsequent dispersion into the atmosphere, is ruled by different complex phenomena, potentially affected by a variety of external chemical and physical parameters. In this regard, the wind velocity and the liquid temperature represent variables that are worth investigating. Given this, the present paper discusses an experimental study aimed at evaluating the influence of these variables on the emission rate of VOCs (i.e. acetone, toluene and butanol) in solution with water at low concentrations (0.5 mL/L and 5 mL/L). The experimental trials are conducted using a wind tunnel system, changing the sweep air flow from 0.02 m/s to about 0.06 m/s and the liquid temperature from 20 °C to 35 °C. This study reveals that while the wind velocity seems to slightly influence the emission rate of VOCs estimated by wind tunnel sampling, the effect of the temperature appears much more significant. This behaviour is also confirmed by experimental trials conducted on real-case industrial wastewater, coming from an equalization tank. In view of this, the approach commonly applied to evaluate the influence of wind velocity (i.e. a dependence of the odour emission rate on the square root of the wind velocity) appears not fully consistent with the experimental results obtained at low concentrations by wind tunnel sampling. Also, the influence of temperature seems more pronounced in the case of butanol, in accordance with the theoretical trend of Henry constant as a function of temperature.

Odor emission rate of a municipal solid waste sanitary landfill during different operation stages before final closure.

This study investigated the odor emission rate from different areas of a municipal solid waste landfill. The surface odor emission rate (SOER) of eight odorous compound groups were determined by flux chamber method. The SOER of working face, seams of daily cover, membrane surface of daily cover, seams of temporary cover, membrane surface of temporary cover, seams of intermediate cover, membrane surface of intermediate cover were 138.34, 49.83, 13.56, 90.35, 14.48, 4.05, and 8.14 µg/(m2·s), respectively. Therefore, odor emission hotspots were at seams of daily and temporary cover areas. Converting the odor emissions at emission hotspots to the entire membrane cover surface, the average SOER of working face, daily cover area, temporary cover area and intermediate cover area were 138.34, 17.95, 22.43, and 6.24 µg/(m2·s), respectively. Combined with the size of each landfill area, the total odor emissions of the four above areas of a landfill zone were 830, 108, 1346, and 5175 mg/s, respectively, suggesting the necessity to control the odor emission of membrane cover stages especially for large-scale landfills. In terms of odor components, alcohols (38.7 %), sulfur compounds (22.9 %) and aldehydes (15.7 %) were major odorous groups.

New dose-response model and SARS-CoV-2 quanta emission rates for calculating the long-range airborne infection risk.

Predictive models for airborne infection risk have been extensively used during the pandemic, but there is yet still no consensus on a common approach, which may create misinterpretation of results among public health experts and engineers designing building ventilation. In this study we applied the latest data on viral load, aerosol droplet sizes and removal mechanisms to improve the Wells Riley model by introducing the following novelties i) a new model to calculate the total volume of respiratory fluid exhaled per unit time ii) developing a novel viral dose-based generation rate model for dehydrated droplets after expiration iii) deriving a novel quanta-RNA relationship for various strains of SARS-CoV-2 iv) proposing a method to account for the incomplete mixing conditions. These new approaches considerably changed previous estimates and allowed to determine more accurate average quanta emission rates including omicron variant. These quanta values for the original strain of 0.13 and 3.8 quanta/h for breathing and speaking and the virus variant multipliers may be used for simple hand calculations of probability of infection or with developed model operating with six size ranges of aerosol droplets to calculate the effect of ventilation and other removal mechanisms. The model developed is made available as an open-source tool.

Effects of soil drought and nitrogen deposition on BVOC emissions and their O3 and SOA formation for Pinus thunbergii.

Soil drought and nitrogen (N) deposition can influence the biogenic volatile organic compound (BVOC) emissions and thereby their ozone (O3) and secondary organic aerosol (SOA) formation. This study addressed their single and combined effects on BVOC emissions of Pinus thunbergii by laboratory simulation experiments. The results showed that light drought (LD, 50% soil volumetric water content (VWC)) stimulated isoprene, monoterpene, sesquiterpene, and total BVOC emissions, while moderate drought (MD, 30% and 40% VWC) and severe drought (SD, 10% and 20% VWC) inhibited their emissions (except for sesquiterpene in 20% VWC). N deposition decreased other VOC emissions and increased isoprene and sesquiterpene emissions. Total BVOCs and monoterpene were stimulated in low N deposition (LN, 2 g N/(m2·yr)) and inhibited in moderate (MN, 5 g N/(m2·yr)) and high N deposition (HN, 10 g N/(m2·yr)). Under combined treatment of soil drought and N deposition, total BVOC, monoterpene, and other VOC emissions were inhibited, sesquiterpene had no significant change, and isoprene emission was inhibited in MD combined treatment but promoted in SD. The O3 formation potential (OFP) and SOA formation potential (SOAP) from the changed BVOC emissions were calculated, OFP and SOAP of BVOC emissions and their compositions varied significantly among the treatments. Our study provided theoretical basis for assessing the impact of climate change and atmospheric pollution on BVOC emissions and their contribution to the formation of secondary atmospheric pollution.

Prediction of exhaled carbon dioxide concentration using a computer-simulated person that included alveolar gas exchange.

Accurate prediction of inhaled CO2 concentration and alveolar gas exchange efficiency would improve the prediction of CO2 concentrations around the human body, which is essential for advanced ventilation design in buildings. We therefore, developed a computer-simulated person (CSP) that included a computational fluid dynamics approach. The CSP simulates metabolic heat production at the skin surface and carbon dioxide (CO2 ) gas exchange at the alveoli during the transient breathing cycle. This makes it possible to predict the CO2 distribution around the human body. The numerical model of the CO2 gas exchange mechanism includes both the upper and lower airways and makes it possible to calculate the alveolar CO2 partial pressure; this improves the prediction accuracy. We used the CSP to predict emission rates of metabolically generated CO2 exhaled by a person and assumed that the tidal volume will be unconsciously reduced as a result of exposure to poor indoor air quality. A reduction in tidal volume resulted in a decrease in CO2 emission rates of the same magnitude as was observed in our published experimental data. We also observed that the predicted inhaled CO2 concentration depended on the flow pattern around the human body, as would be expected.

Emission characteristics of formaldehyde from natural gas combustion and effects of hood exhaust in Chinese kitchens.

Formaldehyde (HCHO) is a well known carcinogen. While most studies investigate emission from wood-based materials, knowledge about releasing of HCHO by natural gas combustion is quite limited. This study conducted field measurements in 9 households to address this issue. We found that emission factor is mainly in the range of 50-200 mg_HCHO/m3_natural gas (median value is 85 mg/m3). Emission rate mainly falls into a range of 0.1-0.4 mg_HCHO/min (median value is 0.16 mg/min). It is also revealed that as the natural gas flow rate increases, the emission factor decreases with a statistically significant Spearman correlation coefficient of -0.46 (p < 0.05). The emission rate shows an opposite trend with a Spearman correlation coefficient of 0.48 (p < 0.05). Formaldehyde generated by natural gas combustion in kitchens can quickly disperse to an adjacent living room when kitchen door is open. A range hood can effectively remove formaldehyde in kitchens if kitchen window is open and kitchen door is closed. Its performance would decrease by half otherwise. These results imply a health co-benefit of reducing household usage of carbon-based natural gas in the age of carbon neutrality aiming climate change.

A Time-Varying Model for Predicting Formaldehyde Emission Rates in Homes.

Recent studies have succeeded in relating emissions of various volatile organic compounds to material mass diffusion transfer using detailed empirical characteristics of each of the individual emitting materials. While significant, the resulting models are often scenario specific and/or require a host of individual component parameters to estimate emission rates. This study developed an approach to estimate aggregated emissions rates based on a wide number of field measurements. We used a multi-parameter regression model based on previous mass transfer models to predict formaldehyde emission rate for a whole dwelling using field-measured, time-resolved formaldehyde concentrations, air exchange rates, and indoor environmental parameters in 63 California single-family houses built between 2011 and 2017. The resulting model provides time-varying formaldehyde emission rates, normalized by floor area, for each study home, assuming a well-mixed mass balance transport model of the home, and a well-mixed layer transport model of indoor surfaces. The surface layer model asserts an equilibrium concentration within the surface layer of the emitted materials that is a function of temperature and RH; the dwelling ventilation rate serves as a surrogate for indoor concentration. We also developed a more generic emission model that is suitable for broad prediction of emission for a population of buildings. This model is also based on measurements aggregated from 27 homes from the same study. We showed that errors in predicting household formaldehyde concentrations using this approach were substantially less than those using a traditional constant emission rate model, despite requiring less unique building information.

α-Fe2O3 nanoparticles and hazardous air pollutants release during cooking using cast iron wok in a commercial Chinese restaurant.

Long-term exposure to fine particles (PM2.5), ultrafine particles (UFPs), and volatile organic compounds (VOCs) emissions from cooking has been linked to adverse human health effects. Here, we measured the real-time number size distribution of particles emitted when cooking two served food in Chinese restaurants and estimated the emission rate of UFPs and PM2.5. Experiments were conducted under a control hood, and both online measurement and offline analysis of PM2.5 were carried out. The measured emission rates of PM2.5 generated from deep-frying and grilling were 0.68 ± 0.11 mg/min and 1.58 ± 0.25 mg/min, respectively. Moreover, the UFPs emission rate of deep-frying (4.3 × 109 #/min) is three times higher than that of grilling (1.4 × 109 #/min). Additionally, the PM2.5 emission of deep-frying was comprised of a considerable amount of α-Fe2O3 (5.7% of PM2.5 total mass), which is more toxic than other iron oxide species. A total of six carcinogenic HAPs were detected, among which formaldehyde, acrolein, and acetaldehyde were found to exceed the inhalation reference concentration (RfC) for both cooking methods. These findings can contribute to future evaluation of single particle and HAPs emission from cooking to better support toxicity assessment.

Turnover of dissolved organic carbon fuels nocturnal CO2 emissions from a headwater catchment reservoir, Southeastern China: Effects of ecosystem metabolism on source partitioning of CO2 emissions.

Dam reservoirs in headwater catchments, as critical zones for their proximity to terrestrial sources, play important roles in dissolved organic carbon (DOC) cycling. However, the effects of ecosystem metabolism (EM) on DOC cycling are not well known. Here, in-situ diurnal and monthly observations were conducted to measure EM (including gross primary production (GPP), ecosystem respiration (ER) and heterotrophic respiration (HR)), DOC turnover and CO2 emissions in a headwater catchment reservoir in Southeastern China in 2020. Our study showed the nocturnal CO2 emission rate was about twice as high as in daytime, and was strongly driven by EM. The values for DOC turnover velocity ranged from 0.10 to 1.59 m/day, and the average DOC turnover rate was 0.13 day-1, with the average removal efficiency of 12%. The contribution of respired DOC to daily CO2 emissions ranged from 17% to 61%. The accumulated efficiencies were estimated to be 13% for the selected 15 reservoirs throughout the Changjiang River network, corresponding to about 0.34 Tg C/year of the respired DOC. The modified CO2 flux was 0.75 Tg C/year, and respired DOC accounted for about 45% of total emitted CO2 from the 15 larger reservoirs. Our research emphasizes the necessity of incorporating the effects of EM into studies of reservoir DOC removal and CO2 emissions.