摘要：矿产资源是经济社会发展的重要物质基础，不合理开采、利用、消费不仅会影响产业链和供应链的安 全，而且会对生态环境造成严重污染。新一轮科技革命和碳中和战略正在重塑全球创新版图和技术格局，伴 随着我国经济社会发展进入后疫情阶段，战略性金属的供需结构正发生深刻变化。一方面，其产业链和供应 链面临的安全挑战从传统的资源产品获取能否得到保障，蔓延至开采、加工、应用、循环利用等全产业链 条。另一方面，我国固体废物产生量迅速增长，但其作为二次金属的循环利用率仍然不高，这将导致大量资 源损失。面向未来，国家（政府） 应尽快建立二次金属的资源量和储量精细分类分级管理体系，健全二次金 属的收集和资源化体系，促进制订资源高效利用制度及标准，保障国内战略性金属的高效内循环及自给自 足，彻底摆脱战略性金属受制于人的局面。
摘要：城市空间结构是城市可持续发展治理及规划的重要抓手。如何科学认识新时期城市空间结构是深化城 市认知并进行人与自然和谐调控的基础。文章简要回顾传统城市空间结构理论的时代背景，通过对新时期技 术革命、政策和社会经济环境的分析，指出城市空间结构在组织原则、组织方式、优化目标及要素成分方面 的变革性转向，阐明传统理论用于解释新时代城市治理的局限性。提出从人地地域系统理论出发重构城市空 间结构研究范式、重新认识城市空间结构载体空间、强化城市空间结构关系解析，以及革新城市空间结构测 度体系等新时代认识路径。未来应对城市空间结构认知方面挑战的关键举措，即重构城市空间结构理论、集 成城市空间结构解析关键技术、融合应用多源数据、建设城市空间结构优化调控的数字孪生平台。
摘要：有机碳埋藏作用是碳循环过程的重要环节，但迄今关于珊瑚礁沉积物中有机碳的研究却很少，影响着对珊瑚礁碳循环的准确评估。本文以南海西沙群岛永乐环礁礁外坡的现代表层沉积物为材料，分析了其总有机碳(total organic carbon, TOC)含量、总氮(total nitrogen, TN)含量、有机碳同位素(δ13C)值以及沉积物粒度、叶绿素含量等指标。永乐环礁礁外坡的生态状况相对较好，具有代表健康珊瑚礁生态系统沉积物中有机碳特征的潜力。结果表明：1）永乐环礁礁外坡沉积物中的TOC含量在0.71~1.66mg·g-1之间，平均为1.23±0.31mg·g-1；TN含量在0.12~0.28mg·g-1之间，平均为0.20±0.05mg·g-1。2）C/N比值在6.16~7.59之间，平均为6.75±0.34；δ13C值在-17.49~-15.85‰之间，平均为-16.61±0.49‰，表明沉积物中的有机碳以海洋自生来源为主，且主要来自底栖植物。3）有机碳含量与水深负相关，与叶绿素a含量和脱镁叶绿素含量正相关，表明底栖植物控制的初级生产力是礁外坡有机碳含量的主要来源。结合该区表层沉积物近3500年的平均沉积速率(1.27mm·a-1)，推测永乐环礁礁外坡有机碳埋藏通量介于1.12~2.61g·m-2·a-1之间，平均为1.93±0.49g·m-2·a-1。本研究为评估南海珊瑚礁对碳循环的贡献提供了新的信息。
摘要：快速预测和评估海啸是预防海洋灾害工作中的重要部分，对于海洋工程和人民生命财产安全具有重要意义。本文以一维卷积神经网络(1-Dimensional Convolutional Neural Network, CONV1D)为基础,构建岛礁地形的类海啸波水动力特性演变模型。通过输入类海啸波波高时程曲线的观测值，得到岛礁指定地点的水位淹没时程曲线，实现时间序列到时间序列的预测，达到预防海洋灾害的目的。结果显示，对类海啸波到达时间预测的平均误差为0.71%，最大水位高度预测的平均误差为6.99%，CONV1D得到的岛礁地形类海啸波水动力特性与数值结果吻合较好。
摘要：Water risk early warning systems based on the water environmental carrying capacity (WECC) are powerful and effective tools to guarantee the sustainability of rivers. Existing work on the early warning of WECC has mainly concerned the comprehensive evaluation of the status quo and lacked a quantitative prejudgement and warning of future overload. In addition, existing quantitative methods for short-term early warning have rarely focused on the integrated change trends of the early warning indicators. Given the periodicity of the socioeconomic system, however, the water environmental system also follows a trend of cyclical fluctuations. Thus, it is meaningful to monitor and use this periodicity for the early warning of the WECC. In this study, we first adopted and improved the prosperity index method to develop an integrated water risk early warning framework. We also constructed a forecast model to qualitatively and quantitatively prejudge and warn about the development trends of the water environmental system. We selected the North Canal Basin (an essential connection among the Beijing- Tianjin-Hebei region) in China as a case study and predicted the WECC in 25 water environmental management units of the basin in 2018–2023. We found that the analysis of the prosperity index was helpful in predicting the WECC, to some extent. The result demonstrated that the early warning system provided reliable prediction (root mean square error of 0.0651 and mean absolute error of 0.1418), and the calculation results of the comprehensive early warning index (CEWI) conformed to the actual situation and related research in the river basin. From 2008 to 2023, the WECC of most water environmental management units in the basin had improved but with some spatial differences: the CEWI was generally poor in areas with many human disturbances, while it was relatively good in the upstream regions with higher forest and grass covers as well as in the downstream areas with larger water volume. Finally, through a sensitivity analysis of the indicators, we proposed specific management measures for the sustainability of the water environmental system in the North Canal Basin. Overall, the integrated water risk early warning framework could provide an appropriate method for the water environmental administration department to predict the WECC of the basin in the future. This framework could also assist in implementing corresponding management measures in advance, especially for the performance evaluation and the arrangement of key short-term tasks in the River Chief System in China.
Abstract: Sand fences made of punched steel plate (PSP) have recently been applied to control wind-blown sand in desertified and Gobi areas due to their strong wind resistance and convenient in situ construction. However, few studies have assessed the protective effect of PSP sand fences, especially through field observations. This study analyzes the effects of double-row PSP sand fences on wind and sand resistance using field observations and a computational fluid dynamics (CFD) numerical simulation. The results of field observations showed that the average windproof efficiencies of the first-row and second-row sand fences were 79.8% and 70.8%, respectively. Moreover, the average windproof efficiencies of the numerical simulation behind the first-row and second-row sand fences were 89.8% and 81.1%, respectively. The sand-resistance efficiency of the double-row PSP sand fences was 65.4%. Sand deposition occurred close to the first-row sand fence; however, there was relatively little sand on the leeward side of the second-row sand fence. The length of sand accumulation near PSP sand fences obtained by numerical simulation was basically consistent with that through field observations, indicating that field observations combined with numerical simulation can provide insight into the complex wind-blown sand field over PSP sand fences. This study indicates that the protection efficiency of the double-row PSP sand fences is sufficient for effective control of sand hazards associated with extremely strong wind in the Gobi areas. The output of this work is expected to improve the future application of PSP sand fences.
Abstract: During aeolian processes, the two most critical factors related to dust emissions are soil particle and aggregate saltation, which greatly affect the vertical profiles of near-surface dust concentrations. In this study, we measured PM10 concentrations at four different heights (0.10, 0.50, 1.00 and 2.00 m) with and without continuous and simultaneous aeolian saltation processes on a Gobi surface in northwestern China from 31 March to 10 April, 2017. We found that the vertical concentration profiles of suspended PM10 matched the log-law model well when there was no aeolian saltation. For the erosion process with saltation, we divided the vertical concentration profiles of PM10 into the saltation-affected layer and the airflow-transport layer according to two different dust sources (i.e., locally emitted PM10 and upwind transported PM10). The transition height between the saltation-affected layer and the airflow-transport layer was not fixed and varied with saltation intensity. From this new perspective, we calculated the airflow-transport layer and the dust emission rate at different times during a wind erosion event occurred on 5 April 2017. We found that dust emissions during wind erosion are primarily controlled by saltation intensity, contributing little to PM10 concentrations above the ground surface compared to PM10 concentrations transported from upwind directions. As erosion progresses, the surface supply of erodible grains is the most crucial factor for saltation intensity. When there was a sufficient amount of erodible grains, there was a significant correlation among the friction velocity, saltation intensity and dust emission rate. However, when supply is limited by factors such as surface renewal or an increase in soil moisture, the friction velocity will not necessarily correlate with the other two factors. Therefore, for the Gobi surface, compared to limiting dust emissions from upwind directions, restricting the transport of suspended dust in its path is by far a more efficient and realistic option for small areas that are often exposed to dust storms. This study provides some theoretical basis for correctly estimating PM10 concentrations in the Gobi areas.
Abstract: Dust emission and wind erosion are widespread phenomena in arid and semi-arid regions, which have far-reaching harmful effects to the environment. This study aimed to use microbial induced carbonate precipitation (MICP) method with Bacillus sphaericus to reduce soil losses that occur in a dust-producing area due to wind erosion in the Ilam Province, Iran. Soil samples at the 0–30 cm depth were used and sterilized in an autoclave for 2 h at 121°C and 103 kPa. Approximately 3 kg soils were weighed and poured in the 35 cm×35 cm×3 cm trays. Different treatments included two levels of B. sphaericus (0.0 and 0.5 OD), three levels of suspension volume (123, 264, and 369 mL), two levels of urea-chloride cementation solution (0.0 and 0.5 M), and two levels of bacterial spray (once and twice spray). After 28 d, soil properties such as soil mass loss, penetration resistance, and aggregate stability were measured. The results showed a low soil mass loss (1 g) in F14 formulation (twice bacterial spray+264 mL suspension volume+without cementation solution) and a high soil mass loss (246 g) in F5 formulation (without bacteria+264 mL suspension volume+0.5 M cementation solution). The highest (42.55%) and the lowest (19.47%) aggregate stabilities were observed in F16 and F7 formulations, respectively, and the highest penetration resistance (3.328 kg/cm2) was observed in F18 formulation. According to the final results, we recommended the formulation with twice bacterial spray, 0.5 M cementation solution, and 269 mL suspension volume as the best combination for soil surface stabilization. Furthermore, this method is environmentally friendly because it has no adverse effects on soil, water, and plants, thus, it would be an efficient approach to stabilize soil surface.
Abstract: Deserts are sensitive to environmental changes caused by human interference and are prone to degradation. Revegetation can promote the reversal of desertification and the subsequent formation of fixed sand. However, the effects of grazing, which can cause the ground-surface conditions of fixed sand to further deteriorate and result in re-desertification, on the greenhouse gas (GHG) fluxes from soils remain unknown. Herein, we investigated GHG fluxes in the Hobq Desert, Inner Mongolia Autonomous Region of China, at the mobile (desertified), fixed (vegetated), and grazed (re-desertified) sites from January 2018 to December 2019. We analyzed the response mechanism of GHG fluxes to micrometeorological factors and the variation in global warming potential (GWP). CO2 was emitted at an average rate of 4.2, 3.7, and 1.1 mmol/(m2•h) and N2O was emitted at an average rate of 0.19, 0.15, and 0.09 µmol/(m2•h) at the grazed, fixed, and mobile sites, respectively. Mean CH4 consumption was as follows: fixed site (2.9 µmol/(m2•h))>grazed site (2.7 µmol/(m2•h))>mobile site (1.1 µmol/(m2•h)). GHG fluxes varied seasonally, and soil temperature (10 cm) and soil water content (30 cm) were the key micrometeorological factors affecting the fluxes. The changes in the plant and soil characteristics caused by grazing resulted in increased soil CO2 and N2O emissions and decreased CH4 absorption. Grazing also significantly increased the GWP of the soil (P<0.05). This study demonstrates that grazing on revegetated sandy soil can cause re-desertification and significantly increase soil carbon and nitrogen leakage. These findings could be used to formulate informed policies on the management and utilization of desert ecosystems.
In semi-arid lands, vegetation is distributed in shrub patches immersed in a less vegetated interpatch matrix. Grazing affects perennial grass seed bank through a decrease in seed rain and an increase in seed predation and soil compaction. Nevertheless, some species with anchorage mechanisms in their seeds might overcome this, such as Nassella tenuis (Phil.) Barkworth. This is an important species in grazing paddocks because it has an intermediate palatability and its relatively tolerant to grazing. These characteristics allow N. tenuis to increase its abundance in grazed sites. Our objective was to assess how grazing affects the key palatable species from seeds to seedlings: i.e., seed rain, soil seed bank, and seedling recruitment in different microsites along a windward-leeward transect across shrub canopy. We hypothesized that: (1) the negative effects of grazing on N. tenuis fructification are reflected in its seed rain, soil seed bank, and seedling recruitment, especially in interpatches; (2) Nassella tenuis seed rain reduction, soil compaction by cattle in grazed sites, and removal of seeds by wind decrease its soil seed bank, especially in microsites exposed to the predominant wind; and (3) the decrease in N. tenuis soil seed bank and cover increase in annual species in grazed sites have negative effects on its seedling recruitment, especially in microsites exposed to predominant wind. We placed seed traps, collected soil samples, and monitored seedling recruitment in different locations around shrub canopy to address our hypotheses. Also, we established a manipulative experiment in which we sow N. tenuis seeds and followed its recruitment in different microsites. We compared the seed rain, soil seed bank, natural seedling recruitment, and sown seeds recruitment of N. tenuis between grazed and ungrazed sites. We analyzed differences between microsites along a windward-leeward transect across shrubs patches. Seed rain and soil seed bank had the same density in patches and interpatches both in ungrazed and grazed sites. But seed rain was higher, and soil seed bank was lower in ungrazed sites than in grazed sites. Almost all under-canopy microsites showed greater soil seed bank abundance and natural seedling recruitment in ungrazed sites. Sown seeds recruitment was the same between grazed and ungrazed sites, but it showed protective effects of shrubs in leeward microsites under grazed sites. As a conclusion, seed rain and soil seed bank are complementary under grazed sites.
及权重，计算出6种供试材料的抗旱性综合评价值（D 值），得到供试材料的抗旱性能力顺序为：长穗偃麦草> 披碱
年，流域建设用地、林地呈现增长趋势，增长面积分别为1350.90 km2、85.50 km2，增长率分别为92.83%、0.96%；耕地、
草地出现小幅下降趋势，缩减面积分别为729 km2、674.10 km2，缩减率分别为-5.02%、-7.63%；水域及未利用土地维
持多年平均水平，平均面积为297 km2、7.92 km2。空间格局呈现建设用地、耕地集中于流域核心区，草地、林地集中
Sensing Ecological Index，RSEI），对流域生态环境质量的时空变化进行分析和评价，利用CA-Markov模型对2022年
1200~1800 m的区域，生态环境质量变化主要受自然因素影响；而海拔低于1200 m的区域，则主要受人类活动影