RESUMEN
Deserts are important components of the terrestrial ecosystem, and significantly affect the terrestrial carbon cycle. However, their carbon storage is poorly understood. To evaluate the topsoil carbon storage in Chinese deserts, we systematically collected topsoil samples (to a depth of 10 cm) from 12 deserts in northern China and analyzed their organic carbon storage. We used partial correlation and boosted regression tree (BRT) analysis to analyze the factors influencing the spatial distribution of soil organic carbon density based on climate, vegetation, soil grain-size distribution, and element geochemistry. The total organic carbon pool of Chinese deserts was 4.83 × 108 t, the mean soil organic carbon density was 1.37 ± 0.18 kg C m-2, and the mean turnover time was 16.50 ± 2.66 yr. With the largest area, the Taklimakan Desert had the highest topsoil organic carbon storage (1.77 × 108 t). The organic carbon density was high in the east and low in the west, whereas the turnover time showed the opposite trend. The soil organic carbon density was >2 kg C m-2 in the four sandy lands in the eastern region, and was greater than the values for the eight deserts (0.72 to 1.22 kg C m-2). Grain-size (i.e., the silt and clay contents) had the strongest influence on the organic carbon density in Chinese deserts, followed by element geochemistry. Precipitation was the main climatic factor that affected the distribution of organic carbon density in the deserts. Based on climate and vegetation cover trends during the past 20 years, Chinese deserts have a high potential for future organic carbon sequestration.
RESUMEN
The study evaluated the acute health damage effect of PM2.5 exposure in winter in Xi'an City, using the average concentration of PM2.5 (24 h) and the Average Poisson Regression Model for three consecutive years, from 2014 to 2016. The Corrected Human Capital Method was used to evaluate the economic loss from premature death. The cost of illness was used to assess the economic loss of hospitalization, illness and clinic. The results show that the economic loss in the study period (2014, 2015, 2016) caused by PM2.5 was about 33.523 billion yuan (95% CI: 24.961-36.975), 21.105 billion yuan (95% CI: 13.560-26.880), and 37.132 billion yuan (95% CI: 27.246-41.164). The proportions of GDP were as follows: 6.10% (4.54%-6.73%), 3.64% (2.34%-4.63%), and 5.91% (4.34%-6.55%) for each of the three years. The health economic loss was positively correlated with the average PM2.5 concentration in winter. PM2.5 pollutants have a significant impact on the health of residents in Xi'an. The number of reported cases was about 1071338 (95% CI: 646432-1385847), 438273 (95% CI: 246842-599989), and 1019503 (95% CI: 611407-1324547) for each of the three years. The effects on children with asthma were significantly higher than that on adults, while adults with chronic bronchitis were affected more significantly than children. This study can provide a scientific basis for cost-benefit analysis of the PM2.5 air quality standard in Xi'an, and provide a reference for the management of environment quality.