滇西北高原生态恢复过程中土壤侵蚀特征及其影响因子

滇西北高原由于地处生态脆弱的石灰岩区,水土流失严重,探讨该区生态恢复过程中土壤侵蚀的变化规律,为开展人工植被建设提供依据。以时空互代的方法,通过径流小区,对坡面的产沙产流特性及其影响因素进行研究。结果表明:天然次生林和人工混交林均有较好的调节径流和减少泥沙的作用,产沙量分别比坡耕地减少了51.46%、43.18%,产流量也相应降低了39.39%、24.24%。在最大次降雨条件下,荒草丛、坡耕地、次生林和混交林单次降雨的产沙量分别占试验期产沙总量的55.38%、55.58%、58.35%和58.05%,产流量相应占产流总量的64.72%、64.63%、73.85%和55.39%。而且,产流产沙量与土壤有机质质量分数均存在明显正相关,与乔、灌层植物多样性及均匀度指数等呈显著负相关性(P<0.05)。因此,乔灌草结合的群落结构配置模式是滇西北地区水土保持林营造的目标和方向。     

基于GIS与RUSLE的武陵山区小流域土壤侵蚀评价研究

以长江中下游武陵山区女儿寨小流域为研究区，基于数据观测积累及实地调查采样等方法，计算了研究区降雨侵蚀力、土壤可蚀性等因子，运用GIS与RUSLE评价了流域土壤侵蚀强度并分析了其与土地利用方式、海拔高度的关系。结果表明，流域平均土壤侵蚀强度为78844 t/（km2·a），属微度侵蚀，流域面积9518%的范围发生轻度以下的侵蚀，强烈以上侵蚀仅占1.19%。从土地利用类型来看，耕地、果园侵蚀强度较大，均达到中度侵蚀，有林地除竹林地为轻度侵蚀外均属微度侵蚀，耕地、果园、竹林地是今后水土流失防治的主要地类。不同海拔高度中，低海拔（200～400 m）区域侵蚀量占到流域侵蚀总量的6442%，是水土流失防治的重点地带。研究为应用修正通用土壤流失方程在武陵山区进行土壤侵蚀评价提供范例，为研究区防治土壤侵蚀和流域管理规划决策提供相应参考     

Streambank Soil and Phosphorus Losses Under Different Riparian Land‐Uses in Iowa1

Abstract: Phosphorus and sediment are major nonpoint source pollutants that degrade water quality. Streambank erosion can contribute a significant percentage of the phosphorus and sediment load in streams. Riparian land‐uses can heavily influence streambank erosion. The objective of this study was to compare streambank erosion along reaches of row‐cropped fields, continuous, rotational and intensive rotational grazed pastures, pastures where cattle were fenced out of the stream, grass filters and riparian forest buffers, in three physiographic regions of Iowa. Streambank erosion was measured by surveying the extent of severely eroding banks within each riparian land‐use reach and randomly establishing pin plots on subsets of those eroding banks. Based on these measurements, streambank erosion rate, erosion activity, maximum pin plot erosion rate, percentage of streambank length with severely eroding banks, and soil and phosphorus losses per unit length of stream reach were compared among the riparian land‐uses. Riparian forest buffers had the lowest streambank erosion rate (15‐46 mm/year) and contributed the least soil (5‐18 tonne/km/year) and phosphorus (2‐6 kg/km/year) to stream channels. Riparian forest buffers were followed by grass filters (erosion rates 41‐106 mm/year, soil losses 22‐47 tonne/km/year, phosphorus losses 9‐14 kg/km/year) and pastures where cattle were fenced out of the stream (erosion rates 22‐58 mm/year, soil losses 6‐61 tonne/km/year, phosphorus losses 3‐34 kg/km/year). The streambank erosion rates for the continuous, rotational, and intensive rotational pastures were 101‐171, 104‐122, and 94‐170 mm/year, respectively. The soil losses for the continuous, rotational, and intensive rotational pastures were 197‐264, 94‐266, and 124‐153 tonne/km/year, respectively, while the phosphorus losses were 71‐123, 37‐122, and 66 kg/km/year, respectively. The only significant differences for these pasture practices were found among the percentage of severely eroding bank lengths with intensive rotational grazed pastures having the least compared to the continuous and rotational grazed pastures. Row‐cropped fields had the highest streambank erosion rates (239 mm/year) and soil losses (304 tonne/km/year) and very high phosphorus losses (108 kg/km/year).     

ENVIRONMENTAL AND ECONOMIC DAMAGE CAUSED BY SEDIMENT FROM AGRICULTURAL NONPOINT SOURCES1

Environmental and economic damages caused by agricultural nonpoint source inputs of sediment and associated pollutants are examined. Widespread water quality problems are identified in lakes, rivers, and estuaries in agricultural areas, and billions of dollars of on-site and offsite costs result from this eroded soil every year. Some water bodies have been irretrievably damaged, and expensive rehabilitation programs are needed to remedy in-place water pollution problems if Clean Water Act goals are to be achieved. Unless effective abatement and rehabilitation programs are established, billions of dollars of benefits to future generations will not be realized as more waters become irretrievably damaged, and billions more will continue to be spent by government to treat symptoms of these sediment-related problems.     

黄土高原坡耕地沟蚀土壤质量评价

黄土高原坡耕地沟蚀广泛而严重。科学评价沟蚀土壤质量是侵蚀环境下土壤保育和利用的重要基础。论文以沟间土壤为对照,分析了坡耕地沟蚀对土壤质量单因子的影响并建立了沟蚀土壤质量综合评价模型。利用加权和法对黄土高原坡耕地不同沟蚀深度下土壤质量进行综合评价。结果表明：①沟蚀对坡耕地不同土壤质量因子的影响有较大差异。沟蚀导致土壤硬化,pH值增加,而土壤团聚体和养分含量（除全磷）随着沟蚀深度增加表现出明显的层次性,近似呈＂W＂型变化规律。②沟蚀深度对土壤质量的影响可以用幂函数y=0.866 8 x-0.142（R2=0.877）较好地拟合。微度侵蚀（〈5 cm）、中度侵蚀（5～30 cm）和重度侵蚀（30～50 cm）的土壤质量指数较沟间土壤分别降低了10.6%、27.9%和36.5%。沟蚀深度5 cm和30 cm是土壤质量显著下降的两个关键点。③反映沟蚀土壤质量的指标可以归为肥力因子、质地因子和结构因子三类。土壤有机质、水稳性团聚体、土壤比表面积和容重4项指标能够很好地反映土壤质量状况,可作为坡耕地沟蚀土壤质量的表征指标。     

Properties of concrete paving blocks made with waste marble

Marble industry produces large amounts of waste marble - what causes environmental problems. In paving blocks based on two cement types we have partly replaced aggregate with waste marble. Physical and mechanical tests were performed on blocks so produced. The cement type turns out to be an important factor. Mechanical strength decreases with increasing marble content while freeze-thaw durability and abrasive wear resistance increase. Waste marble is well usable instead of the usual aggregate in the concrete paving block production.     

石墨烯薄膜原子氧剥蚀行为及电阻特性

目的研究石墨烯薄膜在原子氧空间环境的适应性,为其在航天器上应用提供参考。方法采用刮涂法制备石墨烯薄膜,将石墨烯薄膜材料及石墨烯电阻传感器置于微波源原子氧设备内开展原子氧试验,原子氧剂量分别为3.0×10^20 atoms/cm2和7.5×10^20 atoms/cm^2,研究薄膜表面形貌、结构、成分及电阻性能的变化。结果采用刮涂法可制备氧含量较低的石墨烯薄膜,原子氧剂量为7.5×10^20 atoms/cm^2情况下,石墨烯薄膜的厚度损失为5.3μm,原子氧反应率为7.14×10^-25 atoms/cm^3。原子氧作用后,石墨烯薄膜中碳原子无序程度增大,C—O、—COOH官能团含量降低,C=O官能团含量增加。石墨烯电阻传感器的R0/R比值随原子氧剂量增加线性降低,0.8μm厚度薄膜可探测最大原子氧剂量为5×10^19 atoms/cm^2,增加薄膜厚度有望提高传感器的使用寿命。结论得到了石墨烯薄膜厚度损失、原子氧反应率、微观结构及电阻特性的变化规律,可为石墨烯薄膜的空间应用提供技术支撑。     

先进冷喷涂技术的应用及展望

首先介绍了冷喷涂技术的原理及特点,在此基础上,重点讨论了冷喷涂技术在不同领域的应用。最后,结合我国冷喷涂技术的发展现状,提出了冷喷涂技术的发展方向,并指出发展先进冷喷涂技术符合我国先进技术的发展需求,有助于提高我国制造业的综合水平。     

颗粒冲蚀对注射法制备C/C-ZrC-SiC复合材料 抗烧蚀性能的影响研究

目的采用ZrC和SiC复相陶瓷对C/C复合材料进行改性,研究改性后的复合材料受到颗粒冲蚀破坏的烧蚀行为。方法采用注射法将ZrC和SiC复相陶瓷前驱体引入到等温化学气相渗透法(ICVI)制备的低密度C/C复合材料中,再通过高温热处理、ICVI的方法制备出ZrC和SiC复相陶瓷改性的C/C(C/C-ZrC-SiC)复合材料,随后对制备的复合材料进行高速颗粒冲击实验破坏,并对破坏后的试样进行氧乙炔火焰烧蚀,研究其烧蚀行为。结果改性后的复合材料线冲蚀率和质量冲蚀率分别为253.1μm/s和79.8 mg/s,相较于同孔隙率的C/C复合材料分别降低了49.2%和61%。颗粒冲蚀破坏后C/C-ZrC-SiC复合材料的线烧蚀率和质量烧蚀率分别为4.26μm/s和1.44 mg/s,相比于同孔隙率的C/C复合材料,分别降低了37%和39%。结论由于引入的ZrC和SiC陶瓷相的硬度大于碳基体,C/C-ZrC-SiC复合材料在受到高速颗粒的冲击时,能通过硬质陶瓷相起到抗冲击作用,使得改性后的复合材料抗冲蚀性能大幅度提高。受到颗粒冲蚀破坏后的C/C-ZrC-SiC复合材料内部仍存在超高温陶瓷相,烧蚀过程中能够形成ZrO2骨架结构和SiO2球形颗粒,进而有效保护碳纤维和热解碳基体。     

Determination of Frequency for Remeasuring Ground and Vegetation Cover Factor Needed for Soil Erosion Modeling

Determining a remeasurement frequency of variables over time is required in monitoring environmental systems. This article demonstrates methods based on regression modeling and spatio-temporal variability to determine the time interval to remeasure the ground and vegetation cover factor on permanent plots for monitoring a soil erosion system. The spatio-temporal variability methods include use of historical data to predict semivariograms, modeling average temporal variability, and temporal interpolation by two-step kriging. The results show that for the cover factor, the relative errors of the prediction increase with an increased length of time interval between remeasurements when using the regression and semivariogram models. Given precision or accuracy requirements, appropriate time intervals can be determined. However, the remeasurement frequency also varies depending on the prediction interval time. As an alternative method, the range parameter of a semivariogram model can be used to quantify average temporal variability that approximates the maximum time interval between remeasurements. This method is simpler than regression and semivariogram modeling, but it requires a long-term dataset based on permanent plots. In addition, the temporal interpolation by two-step kriging is also used to determine the time interval. This method is applicable when remeasurements in time are not sufficient. If spatial and temporal remeasurements are sufficient, it can be expanded and applied to design spatial and temporal sampling simultaneously.