A review of surface water quality models.

Surface water quality models can be useful tools to simulate and predict the levels, distributions, and risks of chemical pollutants in a given water body. The modeling results from these models under different pollution scenarios are very important components of environmental impact assessment and can provide a basis and technique support for environmental management agencies to make right decisions. Whether the model results are right or not can impact the reasonability and scientificity of the authorized construct projects and the availability of pollution control measures. We reviewed the development of surface water quality models at three stages and analyzed the suitability, precisions, and methods among different models. Standardization of water quality models can help environmental management agencies guarantee the consistency in application of water quality models for regulatory purposes. We concluded the status of standardization of these models in developed countries and put forward available measures for the standardization of these surface water quality models, especially in developing countries.

Orthokeratology with increased compression factor in adolescent myopia control: a 2-year prospective randomized clinical trial.

AIM: To explore the long-term efficacy, safety, and optical mechanism of orthokeratology with increased compression factor in adolescent myopia control. METHODS: A prospective, double-masked, and randomized clinical trial was performed from May 2016 to June 2020. Subjects aged between 8 and 16y, with myopia (-5.00 to -1.00 D), low astigmatism (≥-1.50 D) and anisometropia (≤1.00 D), were stratified into low (-2.75 to -1.00 D) and moderate (-5.00 to -3.00 D) myopia groups. Then they were randomly assigned to wear either increased compression factor (ICF; 1.75 D) orthokeratology or conventional compression factor (CCF; 0.75 D) orthokeratology. The data were recorded including axial length (AL), spherical equivalent (SE), best corrected visual acuity (BCVA), near visual acuity (NVA), corneal staining (using Efron grading scales), corneal hysteresis (CH), corneal resistance factor (CRF), higher-order aberrations (HOAs, expressed as root mean square, RMSh), and subfoveal choroidal thickness (SFChT) in the 2-year follow-up period. Pearson's correlation coefficient was conducted to analyze the association between the changes in AL and RMSh, SFChT. RESULTS: At the 2-year visit, there were no statistical differences in all the parameters between the ICF group and the CCF group in low myopia subjects (P>0.05). For the moderate myopia subjects, the ICF group had shorter AL elongation (0.23±0.08 vs 0.30±0.11 mm, P=0.015), higher RMSh (1.94±0.50 vs 1.65±0.51 µm, P=0.041), and higher SFChT (279.04±35.72 vs 254.08±29.60 µm, P=0.008) than those in CCF group. The change in AL was negatively correlated with RMSh (r=-0.687, P<0.001) and SFChT (r=-0.464, P=0.013). CONCLUSION: ICF orthokeratology can control the progression of moderate myopia more effectively, which might be related to greater RMSh and SFChT.

[Source Profiles and Impact of VOCs Based on Production Processes in Foundry Industries].

The characteristics of the VOCs species in foundry industries based on the production processes were analyzed through gas chromatography-mass spectrometry (GC-MS) after sampling the emissions of VOCs in 9 typical foundry enterprises using air packages and absorption tubes. The source profiles of the VOCs species in foundry industries based on production processes were established for the first time in China. In addition, the emission characteristics of VOCs and the contribution of VOCs emitted by various production processes to ozone generation were also studied. The results showed that the characteristic components of the VOCs in foundry industries were predominantly aromatic hydrocarbons, halogenated hydrocarbons, and oxygenated hydrocarbons. The average concentrations were 50.9%, 20.8%, and 12.6%, respectively. In general, aromatic hydrocarbons, such as toluene, benzene, and m/p-xylene; halogenated hydrocarbons, such as trichloroethylene and dichloromethane; oxygenated hydrocarbons, such as acetone, ethyl acetate, cyclopentanone, and some alkanes, were the primary VOCs species of the foundry industries. The emission characteristics of different production processes were related to the solvents and surface treating agents used by each process. The results also demonstrated that painting was the largest contributor of VOCs concentrations among all the production processes, followed by the modeling procedure and the silica sol and pouring processes. The OFP values for the different production processes ranged from 0.29-96.09 mg·m-3. Painting was the largest contributor to OFP, followed by the modeling procedure and the melting and pouring processes. Aromatic hydrocarbons and oxygenated hydrocarbons were the dominant contributors to OFP, and 1,3,5-trimethylbenzene, 1,2,4-trimethylbenzene, toluene, and m/p-xylene were the main active components in the foundry industry, with a total contribution to the ozone generation potential of nearly 60%. It is suggested that the painting process should be prioritized regarding control measures to reduce its emissions and impact, while the waste gas from the modeling procedure and the melting and pouring processes should be collected efficiently and treated properly before being discharged to the environment.

Air pollution emissions from Chinese power plants based on the continuous emission monitoring systems network.

To meet the growing electricity demand, China's power generation sector has become an increasingly large source of air pollutants. Specific control policymaking needs an inventory reflecting the overall, heterogeneous, time-varying features of power plant emissions. Due to the lack of comprehensive real measurements, existing inventories rely on average emission factors that suffer from many assumptions and high uncertainty. This study is the first to develop an inventory of particulate matter (PM), SO2 and NOX emissions from power plants using systematic actual measurements monitored by China's continuous emission monitoring systems (CEMS) network over 96-98% of the total thermal power capacity. With nationwide, source-level, real-time CEMS-monitored data, this study directly estimates emission factors and absolute emissions, avoiding the use of indirect average emission factors, thereby reducing the level of uncertainty. This dataset provides plant-level information on absolute emissions, fuel uses, generating capacities, geographic locations, etc. The dataset facilitates power emission characterization and clean air policy-making, and the CEMS-based estimation method can be employed by other countries seeking to regulate their power emissions.

[Contribution of Emissions from Cement to Air Quality in China].

This study analyzed the concentrations of exhaust gas in the process (kiln head and kiln tail) of China's cement industry, based on data from continuous emission monitoring systems network in 2018. The cement emission inventory for China with high resolution (high resolution cement emission inventory for China, HCEC), using the bottom-up approach, was established. The results indicated that during 2018, the total emissions of PM, SO2, and NOx were 72893, 92568, and 878394 t, respectively. In terms of temporal evolution, the exhaust concentration of flue gas in the main process gradually decreased, with obvious emission reduction from the Blue Sky Protection Campaign. Regionally, the exhaust concentrations of flue gas of the kiln head and kiln tail in Beijing-Tianjin-Hebei and surrounding areas, and the Yangtze River Delta and Fenwei Plain, showed a considerable decline, with a high to average level in China. The flu concentrations of each city differed; the cement industry in Anhui Province generated the largest emission in the country, while Beijing and Tianjin showed the highest emission intensity per unit area.

[Inventory and Distribution Characteristics of China's Thermal Power Emissions Under Ultra-Low Reconstruction].

This study updates a bottom-up high-resolution emission inventory and estimates the concentrations, emission factors, emissions, and performance values of China's power plants, based on the data from continuous emission monitoring systems and environmental statistics in 2018. The results show that the ultra-low emission policy has significant effects: the average concentrations of SO2, NOx, and PM in thermal power plants were 37.57, 56.71, and 7.41 mg ·m-3, respectively in 2018, which were 58.71%, 43.12%, and 60.79% lower than those in 2015. The average emission factors of SO2, NOx, and PM from coal-fired units in China were 0.3, 0.48, and 0.06 g ·kg-1, respectively, which were 55.2%, 36.84%, and 62.5% lower than those in 2015. The total emissions of SO2, NOx, PM, and PM2.5in thermal power plants were 721.4, 1183.8, 149.0, and 135.9 kt ·a-1, respectively, down by 41.32%, 19.29%, 48.12%, and 40.39% from 2015.

[Contribution of Emissions from the Iron and Steel Industry to Air Quality in China].

Based on the data from a continuous emission monitoring systems network in 2015, this study analyzed the compliance rates of exhaust gas in the processes of China's iron and steel industry, and established a high-resolution steel plant emission inventory for China (HSEC, 2015), based on the bottom-up method. The contribution of emissions from the iron and steel industry to regional air quality was quantitatively simulated using a CAMx model. The results showed that in 2015, the total emissions of SO2, NOx, PM10, PM2.5, PCDD/Fs, VOCs, CO, BC, OC, EC, and F were 374800 t, 720500 t, 334800 t, 150300 t, 1.91 kg, 842900 t, 34788500 t, 6400 t, 8300 t, 800 t, and 7700 t, respectively. From a regional perspective, the iron and steel industry in Shanghai and Tianjin has the highest emission intensity per unit area and contributes a high proportion to regional air pollution. From a process perspective, in 2015, the exhaust concentration of flue gas in the main process gradually decreased, with a high compliance rate, and the emission factor significantly decreased to lower than that in the existing research results. From a species perspective, in 2015, NOx emission from the steel industry contributed the most to regional air quality, and there is therefore a great emission reduction potential for NOx.

Characteristics of PCDD/Fs and metals in surface soil around an iron and steel plant in North China Plain.

In this study, the level of 18 species of metals and 17 species of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) were monitored in surface soil samples around an iron and steel plant in the North China Plain. The concentration of PCDD/Fs and metals in the soil ranged from 0.16 to 4.5 ng I-TEQ/kg and 1.2 to 24,182.2 mg/kg, respectively. Furthermore, the prevailing winds were confirmed to influence the spatial distribution of PCDD/Fs and metals concentrations. The highest concentration of PCDD/Fs was located in downwind soil sample 4 (S4), which showed more than 50% of PCDFs in the total PCDD/Fs, and high levels of lower chlorinated PCDFs. Moreover, the highest Cd and Zn concentrations of 18.1 and 2647.8 mg/kg, respectively, were observed in soil collected from S4, which were significantly above the government guidelines for metals in farmland soil. Our results show that a group of metals (Mg, Al, K, Fe, Cu, Zn, Se, Cd, Sb and Pb) was well correlated with all PCDD/Fs except three (OCDD, 1,2,3,4,6,7,8-HpCDD and 1,2,3,7,8,9-HxCDD), which likely originated from iron and steel processes. Additionally, Pb, Zn, Cd and all polychlorinated dibenzofurans showed a good correlation and grouped in one cluster, suggesting anthropogenic sources from sintering process. Therefore, the metallic characteristics in soil, especially the Pb, Zn and Cd tracers, implied evidence of the accumulation of PCDD/Fs from sinter plants.

[CALPUFF Modeling of the Influence of Typical Industrial Emissions on PM2.5 in an Urban Area Considering the SOA Transformation Mechanism].

120 main industrial installations were screened based on the emissions inventory of 2016 in Cangzhou City, and the air pollution effect of PM2.5, PM10, SO2, NO2, sulfates, nitrates, and secondary organic aerosol (SOA) was simulated for 2017 autumn-winter season for different levels of pollution using the CALPUFF model after code recompilation. The results showed that the ratios of the modelled and measured concentrations of PM2.5, PM10, SO2, and NO2 were 3.3%, 5.7%, 5.6%, and 2.9%, respectively. The areas most affected by pollution from primary PM10 were the southwest and southeast part of Cangzhou, while sulfate, nitrate, and SOA pollution mainly affected the southeast part. The proportion of SOA in the PM2.5 was around 27.3%, and rose to 29.0% during heavily polluted periods. The aerosols of alkenes, tolune, xylene, and PAH in PM2.5 accouted for 12.1%, 6.0%, 7.0%, and 2.2% of the total aerosols respectively. The result of the simulation of individual enterprises showed that their total contribution to PM2.5 during heavily polluted periods was 3.02 µg·m-3, accounting for 50% of the requirements in the "Three-year Plan" for Cangzhou City (6.00 µg·m-3). The top 5 contributors were 1 Petrochemical industry in Cangzhou (0.41 µg·m-3), 2 Carbon Co. Ltd. (0.29 µg·m-3), 3 Petrochemical industry in Juhai (0.26 µg·m-3), 4 Fertilizer Company (0.23 µg·m-3), 5 Dahua Co. Ltd. (0.19 µg·m-3). These industrial installations were mainly located in Xinhua District, Cangxian, and Bohai New District. This research can provide a scientific ground for production restrictions and limitations and emissions reduction of each industry during heavily polluted periods.

Focal atrial tachycardia surrounding the anterior septum: strategy for mapping and catheter ablation.

BACKGROUND: Focal atrial tachycardias (ATs) surrounding the anterior atrial septum (AAS) have been successfully ablated from the right atrial septum (RAS), the aortic cusps, and the aortic mitral junction. However, the strategy for mapping and ablation of AAS-ATs has not been well defined. METHODS AND RESULTS: Of 227 consecutive patients with AT, 47 (20.7%; mean age, 56.3±11.6 years) with AAS-ATs were studied; among them, initial ablation was successful at RAS in only 5 of 14 patients and at noncoronary cusp (NCC) in 28 of 33 patients. In 45 of the 47 patients, the 46 of 48 AAS-ATs were eliminated at RAS in 8 patients, NCC in 35 patients (earliest activation time at NCC was later than that at RAS by 5-10 ms in 6 patients), and aortic mitral junction in 3 patients (all with negative P wave in lead aVL and positive P wave in the inferior leads), including 1 patient whose 2 ATs were eliminated separately from the NCC and the aortic mitral junction. CONCLUSIONS: Most of the ATs surrounding the AAS can be eliminated from within the NCC, which is usually the preferential ablation site. Ablation at the RAS and aortic mitral junction should be considered when supported by P-wave morphologies on surface ECG and results of activation mapping and ablation.

[Health risk assessment of coke oven PAHs emissions].

Polycyclic aromatic hydrocarbons (PAHs) produced by coke oven are with strong toxicity and carcinogenicity. Taken typical coke oven of iron and steel enterprises as the case study, the dispersion and migration of 13 kinds of PAHs emitted from coke oven were analyzed using AERMOD dispersion model, the carcinogenic and non-carcinogenic risks at the receptors within the modeling domain were evaluated using BREEZE Risk Analyst and the Human Health Risk Assessment Protocol for Hazardous Waste Combustion (HHRAP) was followed, the health risks caused by PAHs emission from coke oven were quantitatively evaluated. The results indicated that attention should be paid to the non-carcinogenic risk of naphthalene emission (the maximum value was 0.97). The carcinogenic risks of each single pollutant were all below 1.0E-06, while the maximum value of total carcinogenic risk was 2.65E-06, which may have some influence on the health of local residents.