保护层开采工作面采空区瓦斯分层治理

为实现保护层开采工作面生产过程中瓦斯不超限,在分析工作面瓦斯来源的基础上,提出了保护层开采工作面竖向分层治理瓦斯的思路。根据相似模拟结果,分析了采空区瓦斯流动范围和流动范围内孔隙率、风阻分布特征。采用数值模拟分析了Y型通风、Y型通风+采空区埋管及Y型通风+采空区埋管+高抽巷+高位钻场3种瓦斯治理方式下采空区瓦斯体积分数场,结果表明:采空区瓦斯体积分数在竖直方向和水平方向均具有典型的递变特征,距工作面越远,距煤层越高,瓦斯体积分数越大;合适位置的煤层顶板高抽巷对抽采来自上邻近层的瓦斯具有较好的效果,试验条件下高抽巷抽采瓦斯量达到了总量的36.4%~63.6%;沿充填墙的采空区埋管不能完全拦截下层采空区进入沿空巷的采空区瓦斯,随沿空巷长度增加,瓦斯体积分数增大,建议沿空巷长度控制在250 m范围内。     

强化曝气对潜流人工湿地堵塞物分布规律的影响

构建曝气及未曝气潜流人工湿地小试实验系统,研究曝气对人工湿地堵塞物组分及分布规律的影响.结果表明:两系统中堵塞物组成均以无机物为主,曝气对堵塞物累积总量影响不大,但对堵塞物化学组分影响较大,使堵塞物中有机物组分比例降低.未曝气及曝气系统堵塞物平均累积量分别为5.18 mg·g~(-1)及5.21 mg·g~(-1),有机物所占比例分别为28.4%和15.6%.曝气对堵塞物在水平及深度方向的分布影响不大,两系统均表现为底层累积物含量略高于表层,出水端累积物含量略高于进水端.电镜及能谱分析结果显示,受溶解氧因素的影响,两系统中表层填料元素种类均较底层丰富,且曝气系统较未曝气系统丰富.     

酸性矿井水的治理方法研究进展

酸性矿井水污染已成为全球范围内较为严重的环境污染问题之一,其污染范围广泛,诱因复杂,性质多变,危害深远。酸性矿井水未经处理排放造成江湖河流酸化,地表土壤板结,水中及土壤中的重金属含量超标,导致生物体内重金属过量富集,作物死亡,从而严重地危害了人类的健康和生命安全。对于酸性矿井水的治理意义重大,刻不容缓。讨论了目前国内外常见的酸性矿井水污染的治理技术方法,并对各种方法进行了比较。     

ESTIMATION OF REGIONAL EVAPOTRANSPIRATION FROM ARID AND SEMI-ARID SURFACES1

ABSTRACT: Evapotranspiration (ET) from oasis and Gobi surfaces in the Heihe River region of China was estimated by Kotoda (1986) and Advection-Aridity (Brutsaert and Stricker, 1979) models. The ET estimates were compared with eddy-correlation ET estimates. The ET estimated by both models are in good agreement with ET obtained by means of eddy-correlation method for the oasis surface while underestimating ET as compared to the eddy-correlation method. For the Gobi surface, the models yielded obviously overestimates of evapotranspiration. In order to estimate evapotranspiration from arid surfaces, the Kotoda model was modified by introducing the surface moisture availability parameter a from Barton (1979). The modified Kotoda model yielded ET estimates that were very close to that from the eddy-correlation method for the Gobi surface. The modified Kotoda model was used to estimate evapotranspiration from the Heihe River watershed, an area with complicated topography and land use, and the results compared with those from a water balance method. A sensitivity analysis of the modified model was performed. The results show that the modified Kotoda model can reflect the relationship between the actual evapotranspiration and the main controlling factors on it for both wet and arid surfaces reasonably. From this study, it can be concluded that the modified Kotoda model is applicable fro the estimation of regional evapotranspiration from areas with complicated topography and land use.     

EFFECTS OF CONTROLLED DRAINAGE ON STORM EVENT HYDROLOGY IN A LOBLOLLY PINE PLANTATION1

ABSTRACT: A paired watershed approach was utilized to study the effects of three water management regimes on storm event hydrology in three experimental watersheds in a drained loblolly pine (Pinus taeda L.) plantation in eastern North Carolina. The regimes were: (1) conventional drainage, (2) controlled drainage (CD) to reduce outflows during spring fish recruitment, and (3) controlled drainage to reduce outflows and conserve water during the growing season. Data from two pit‐treatment years and three years of CD treatment with raised weirs at the watershed outlet are presented. CD treatment resulted in rises in water table elevations during the summer. But the rises were small and short‐lived due to increased evapotranspiration (ET) rates as compared to the spring treatment with lower ET demands. CD treatment had no effect on water tables deeper than 1.3 m. CD treatments, however, significantly (α= 0.05) reduced the stoning outflows for all events, and peak outflow rates for most of the events depending upon the outlet weir level. In some events, flows did not occur at all in watersheds with CD. When event outflows occurred, duration of the event was sharply reduced because of reduced effective ditch depth. Water table depth at the start of an event influenced the effect of CD treatment on storm event hydrology.     

Effects of climatic data low-pass filtering on the ICBM temperature- and moisture-based soil biological activity factors in a cool and humid climate

The air temperature (T_air), total precipitation (TP) and potential evapotranspiration (PET) are standard input data for soil carbon dynamic models, i.e., for calculating temperature and moisture effects on soil biological activity. The resolution needed depends on objectives, the complexity of models and inbuilt pedotransfer functions. The Introductory Carbon Balance Model (ICBM) soil climate front end model calculates a multiplicative soil-temperature (r_{e_temp}) and -moisture (r_{e_wat}) factor with a daily time-step to estimate soil biological activity, i.e., r_{e_crop} = r_{e_temp} × r_{e_wat}. Our objective was to determine how much r_{e_temp}, r_{e_wat} and r_{e_crop} are affected by low-pass filtering of the climatic input data for a cool, humid temperate region. To achieve this we conducted spectral analysis on T_air, TP, PET and r_{e_crop} in the frequency domain. Thereafter we applied Fourier low-pass filters of 5, 15, 30, 60 and 180 days on T_air, TP, PET and tracked their effects through the soil climate model's state variables and outputs. This was done using a sandy and a heavy clay soil and an 89-year daily time-series from a meteorological station in Quebec (Canada). The Fourier spectra showed that the variance for T_air, PET and r_{e_crop} was dominated by an annual cycle, as could be expected. There was no yearly cycle for TP. The variation in r_{e_temp} explained most of the variance in r_{e_crop}. The soil climate module outputs were not sensitive to low-pass filtering of PET. A daily time-step was needed to avoid overestimating r_{e_crop} for the sandy soil. Using a weekly time-step for TP and T_air allowed us to explain about 80% of the variance in r_{e_crop} for the heavy clay soil. This study also indicates that the standard leaf (and green) area index functions for calculating transpiration should receive more attention, since they have significant effects on the state and output variables.     

龙川江楚雄站碳侵蚀通量的动态分析

选取龙川江楚雄水文站进行了为期3年的采样,分析了水体中各形式碳的含量,并估算各碳的输送通量.结果表明:楚雄站3年的碳通量(FTC)分别为27.12×106g·km-2·a-1、24.87×106g·km-2·a-1和10.34×106g·km-2·a-1,分析流域在对碳输送过程中,以输送无机碳为主,分别占输送总量的89.7%、90.3%及91.9%;而汛期碳输送量分别占全年总量的90.9%、84.9%和83.8%,表现出流域汛期对碳的搬运量远远高于非汛期;溶解性有机碳通量(FDOC)与颗粒有机碳通量(FPO C)平均比为0.82,不同季节表现情况不一,非汛期溶解性有机碳(DOC)与颗粒有机碳(POC)含量相当,汛期机械侵蚀作用增强,导致FPO C远远大于FDOC,反映汛期对流域侵蚀作用以机械剥蚀为主,化学侵蚀为辅.研究期内恰遇2008年一场洪水,11月碳的侵蚀通量为8.53×106g·km-2·a-1,其中溶解性无机碳(DIC)、溶解性有机碳(DOC)和颗粒有机碳(POC)的输送量分别为7.37×106、0.36×106、0.80×106g·km-2·a-1,分别占2008年全年相应形式碳总量的33.3%、34.4%和59.9%,为当年非汛期碳侵蚀总量的2.3倍,反映洪水期的碳输出量对流域碳输出总量及构成存在不可忽略的贡献.     

潜流人工湿地基质堵塞的研究进展

潜流人工湿地是城市污水深度处理和农村污水分散处理的有效技术,但存在的基质堵塞问题因可缩短其使用寿命而极大降低了该技术的经济优势,成为制约其发展的瓶颈和研究的重点.在分析潜流人工湿地基质堵塞影响因素的基础上,探讨了其堵塞的机理和模型,提出了预防措施和恢复对策.前期进水预处理、进行湿地数值模拟和强化运行管理等能有效解决人工湿地堵塞问题.     

Identifying and Evaluating a Suitable Index for Agricultural Drought Monitoring in the Texas High Plains

Drought is a complex and highly destructive natural phenomenon that affects portions of the United States almost every year, and severe water deficiencies can often become catastrophic for agricultural production. Evapotranspiration (ET) by crops is an important component in the agricultural water budget; thus, it is advantageous to include ET in agricultural drought monitoring. The main objectives of this study were to (1) conduct a literature review of drought indices with a focus to identify a simple but simultaneously adequate drought index for monitoring agricultural drought in a semiarid region and (2) using the identified drought index method, develop and evaluate time series of that drought index for the Texas High Plains. Based on the literature review, the Standardized Precipitation‐Evapotranspiration Index (SPEI) was found to satisfy identified constraints for assessing agricultural drought. However, the SPEI was revised by replacing reference ET with potential crop ET to better represent actual water demand. Data from the Texas High Plains Evapotranspiration network was used to calculate SPEIs for the major irrigated crops. Trends and magnitudes of crop‐specific, time‐series SPEIs followed crop water demand patterns for summer crops. Such an observation suggests that a modified SPEI is an appropriate index to monitor agricultural drought for summer crops, but it was found to not account for soil water stored during the summer fallow period for winter wheat.     

Specific Yield Functions for Estimating Evapotranspiration from Diurnal Surface Water Cycles

The White method has been routinely used to estimate evapotranspiration using diurnal variations in groundwater levels. Applications to surface water systems (e.g., wetlands) are less common. For applications to surface water systems, a stage‐dependent specific yield function must be defined. This is especially important for small wetlands formed in topographic depressions with bowl shaped bathymetries. Existing formulations of the specific yield function include weighting factors that impact the relative importance of the soil and open water specific yields on the composite value. Three formulations of the specific yield function from the literature were compared and found to produce varied results. Based on a comparison with empirical estimates of specific yield based on observed ratios of net precipitation to water level rise, one of the existing formulations is generalized and recommended for general use. The recommended function is dependent on wetland bathymetry, magnitude of the diurnal fluctuation, spatial extent of the equilibration area, and soil‐specific yield. A sensitivity analysis was conducted to examine the relative importance of these variables. The specific yield function is independent of wetland size and is strongly dependent on the basin profile coefficient (p), an indication of wetland shape. For most natural wetlands, bathymetry strongly influences specific yield.