分类： 环境科学技术及资源科学技术 >> 环境科学技术基础学科 提交时间： 2023-11-13 合作期刊: 《干旱区科学》
摘要： Global ecosystems and public health have been greatly impacted by the accumulation of heavy metal(loid)s in water. Source-specific risk apportionment is needed to prevent and manage potential groundwater contamination with heavy metal(loid)s. The heavy metal(loid)s contamination status, water quality, ecological risk, and health risk apportionment of the Shule River Basin groundwater are poorly understood. Therefore, field sampling was performed to explore the water quality and risk of heavy metal(loid)s in the groundwater of the Shule River Basin in northwestern China. A total of 96 samples were collected from the study area to acquire data for water quality and heavy metal(loid)s risk. There was noticeable accumulation of ferrum in the groundwater of the Shule River Basin. The levels of pollution were considered to be moderately low, as evaluated by the degree of contamination, heavy metal evaluation index, heavy metal pollution index, and Nemerow pollution index. The ecological risks were also low. However, an assessment of the water quality index revealed that only 58.34% of the groundwater samples had good water quality. The absolute principal component scores-multiple linear regression model was more suited for this study area than the positive matrix factorization model. There were no obvious noncarcinogenic or carcinogenic concerns for all types of receptors according to the values of the total hazard index and total carcinogenic risk. The human activities and the initial geological environment factor (65.85%) was the major source of noncarcinogenic risk (residential children: 87.56%; residential adults: 87.52%; recreational children: 86.77%; and recreational adults: 85.42%), while the industrial activity factor (16.36%) was the major source of carcinogenic risk (residential receptors: 87.96%; and recreational receptors: 68.73%). These findings provide fundamental and crucial information for reducing the health issues caused by heavy metal(loid)s contamination of groundwater in arid areas.
分类： 核科学技术 >> 粒子加速器 提交时间： 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要： A proton therapy system is a large medical device to treat tumors. Its gantry is of large structure and high precision. A new half-gantry was designed in the Shanghai Advanced Proton Therapy (SAPT) project. In this paper, the weight of gantry in design is reduced significantly by size and structure optimizations, to improve its cost-effectiveness, while guaranteeing the functions and precision. The processes of physics optimization, empirical design optimization, topological optimization and size optimization, together with factors of consideration, are described. The gantry weight is reduced by 30%, with the same precision.
分类： 地球科学 >> 地理学 提交时间： 2021-08-06 合作期刊: 《干旱区科学》
摘要： Water resources are a crucial factor that determines the health of ecosystems and socio-economic development; however, they are under threat due to climate change and human activities. The quantitative assessment of water resources using the concept of blue water and green water can improve regional water resources management. In this study, spatiotemporal distributions of blue water and green water were simulated and analyzed under scenarios of climate change and land-use changes using the Soil and Water Assessment Tool (SWAT) in Ningxia Hui Autonomous Region, Northwest China, between 2009 and 2014. Green water, a leading component of water resources, accounted for more than 69.00% of the total water resources in Ningxia. Blue water and green water showed a single peak trend on the monthly and annual scales during the study period. On the spatial scale, the southern region of Ningxia showed higher blue water and green water resources than the northern region. The spatiotemporal distribution features of blue water, green water, and green water flow had strong correlations with precipitation. Furthermore, the simulation identified the climate change in Ningxia to be more influential on blue water and green water than land-use changes. This study provides a specific scientific foundation to manage water resources in Ningxia when encountered with climate change together with human activities.
分类： 地球科学 >> 地理学 提交时间： 2019-08-30 合作期刊: 《干旱区科学》
摘要： Soil tillage and straw retention in dryland areas may affect the soil aggregates and the distribution of total organic carbon. The aims of this study were to establish how different tillage and straw retention practices affect the soil aggregates and soil organic carbon (SOC) and total nitrogen (TN) contents in the aggregate fractions based on a long-term (approximately 15 years) field experiment in the semi-arid western Loess Plateau, northwestern China. The experiment included four soil treatments, i.e., conventional tillage with straw removed (T), conventional tillage with straw incorporated (TS), no tillage with straw removed (NT) and no tillage with straw retention (NTS), which were arranged in a complete randomized block design. The wet-sieving method was used to separate four size fractions of aggregates, namely, large macroaggregates (LA, >2000 μm), small macroaggregates (SA, 250–2000 μm), microaggregates (MA, 53–250 μm), and silt and clay (SC, <53 μm). Compared to the conventional tillage practices (including T and TS treatments), the percentages of the macroaggregate fractions (LA and SA) under the conservation tillage practices (including NT and NTS treatments) were increased by 41.2%–56.6%, with the NTS treatment having the greatest effect. For soil layers of 0–5, 5–10 and 10–30 cm, values of the mean weight diameter (MWD) under the TS and NTS treatments were 10.68%, 13.83% and 17.65%, respectively. They were 18.45%, 19.15% and 14.12% higher than those under the T treatment, respectively. The maximum contents of the aggregate-associated SOC and TN were detected in the SA fraction, with the greatest effect being observed for the NTS treatment. The SOC and TN contents were significantly higher under the NTS and TS treatments than under the T treatment. Also, the increases in SOC and TN levels were much higher in the straw-retention plots than in the straw-removed plots. The macroaggregates (including LA and SA fractions) were the major pools for SOC and TN, regardless of tillage practices, storing 3.25–6.81 g C/kg soil and 0.34–0.62 g N/kg soil. Based on the above results, we recommend the NTS treatment as the best option to boost soil aggregates and to reinforce carbon and nitrogen sequestration in soils in the semi-arid western Loess Plateau of northwestern China.
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