Visibility in the Sichuan Basin of China has long been at low levels due to topographic features and high pollution. This study produced trend maps tracking the spatial patterns and temporal trends of visibility in the Sichuan Basin based on 38 years of daily visibility data. Three major fluctuations in the visibility pattern were found: a period of decreasing visibility from 1973 to 1990, a period in which the visibility pattern remained stable from 1991 to 2000, and a period of the visibility recovery from 2001 to 2010. Data from 12 stations in the Sichuan Basin were further analyzed using cumulative percentiles, ridit analysis and days of visibility > 19 km and < 10 km. Hazy conditions were most prevalent in Chengdu and Chongqing, which had visibility less than 10 km and more than 200 low visibility days per year after 2000. Fengjie, Youyang and Langzhong showed consistent declines in visibility and in the number of days with visibility > 19 km whereas Liangping, Nanchong and Wanyuan experienced relatively small decreases but much variation. Upturn trends were observed in Daxian, Mianyang, Ya'an and Yibin after 1995. Although the specific trends differed among stations, a general trend of reduced visibility was found over Sichuan basin. Median visibilities in 2000s were approximately 4 to 38% lower than those during the 1970s, indicating that more efforts are needed for recovery. This study represents the first comprehensive analysis of long-term visibility patterns in the Sichuan Basin.
Lake Fuxian is the largest deep freshwater lake in China. Although its average water quality meets Class I of the China National Water Quality Standard (CNWQS), i.e., GB3838-2002, monitoring data indicate that the water quality approaches the Class II threshold in some areas. Thus it is urgent to reduce the watershed load through the total maximum daily load (TMDL) program. A three-dimensional hydrodynamic and water quality model was developed for Lake Fuxian, simulating flow circulation and pollutant fate and transport. The model development process consists of several steps, including grid generation, initial and boundary condition configurations, and model calibration processes. The model accurately reproduced the observed water surface elevation, spatiotemporal variations in temperature, and total nitrogen (TN), total phosphorus (TP), and chemical oxygen demand (COD) concentrations, suggesting a reasonable numerical representation of the prototype system for further TMDL analyses. The TMDL was calculated using two interpretations of the water quality standards for Class I of the CNWQS based on the maximum instantaneous surface and annual average surface water concentrations. Analysis of the first scenario indicated that the TN, TP and COD loads should be reduced by 66%, 68% and 57%, respectively. Water quality was the highest priority; however, local economic development and cost feasibility for load reduction can pose significant issues. In the second interpretation, the model results showed that, under the existing conditions, the average water quality meets the Class I standard and therefore load reduction is unnecessary. Future studies are needed to conduct risk and cost assessments for realistic decision-making.
Octupole properties in even®Ceven 220®C230 U isotopes have been investigated using improved total Routhian surface calculations with the inclusion of reflection-asymmetric deformations. We pay attention to the evolution of octupole properties with increasing nucleon and rotational frequency. 222 U is predicted to have static octupole deformation up to high spins. A shape transition from reflection-symmetry to reflection-asymmetry happens across 228 92 U 136 with decreasing neutron number in uranium isotopes or decreasing proton number in N = 136 isotones. Our calculations were compared with previous calculations and available experiments.
