Effects of Land‐Use and Land‐Cover Change on Evapotranspiration and Water Yield in China During 1900‐20001

Abstract: China has experienced a rapid land‐use/cover change (LUCC) during the 20th Century, and this process is expected to continue in the future. How LUCC has affected water resources across China, however, remains uncertain due to the complexity of LUCC‐water interactions. In this study, we used an integrated Dynamic Land Ecosystem Model (DLEM) in conjunction with spatial data of LUCC to estimate the LUCC effects on the magnitude, spatial and temporal variations of evapotranspiration (ET), runoff, and water yield across China. Through comparisons of DLEM results with other model simulations, field observations, and river discharge data, we found that DLEM model can adequately catch the spatial and seasonal patterns of hydrological processes. Our simulation results demonstrate that LUCC led to substantial changes in ET, runoff, and water yield in most of the China’s river basins during the 20th Century. The temporal and spatial patterns varied significantly across China. The largest change occurred during the second half century when almost all of the river basins had a decreasing trend in ET and an increasing trend in water yield and runoff, in contrast to the inclinations of ET and declinations of water yield in major river basins, such as Pearl river basin, Yangtze river basin, and Yellow river basin during the first half century. The increased water yield and runoff indicated alleviated water deficiency in China in the late 20th Century, but the increased peak flow might make the runoff difficult to be held by reservoirs. The continuously increasing ET and decreasing water yield in Continental river basin, Southwest river basin, and Songhua and Liaohe river basin implied regional water deficiency. Our study in China indicates that deforestation averagely increased ET by 138 mm/year but decreased water yield by the same amount and that reforestation averagely decreased ET by 422 mm/year since most of deforested land was converted to paddy land or irrigated cropland. In China, cropland‐related land transformation is the dominant anthropogenic force affecting water resources during the 20th Century. On national average, cropland expansion was estimated to increase ET by 182 mm/year while cropland abandonment decreased ET by 379 mm/year. Our simulation results indicate that urban sprawl generally decreased ET and increased water yield. Cropland managements (fertilization and irrigation) significantly increased ET by 98 mm/year. To better understand LUCC effects on China’s water resources, it is needed to take into account the interactions of LUCC with other environmental changes such as climate and atmospheric composition.     

Removal of organic compounds during treating printing and dyeing wastewater of different process units

Wastewater in Shaoxing wastewater treatment plant (SWWTP) is composed of more than 90% dyeing and printing wastewater with high pH and sulfate. Through a combination process of anaerobic acidogenic [hydraulic retention time (HRT) of 15h], aerobic (HRT of 20h) and flocculation-precipitation, the total COD removal efficiency was up to 91%. But COD removal efficiency in anaerobic acidogenic unit was only 4%. As a comparison, the COD removal efficiency was up to 35% in the pilot-scale upflow anaerobic sludge bed (UASB) reactor (HRT of 15h). GC-MS analysis showed that the response abundance of these wastewater samples decreased with their removal of COD. A main component of the raw influent was long-chain n-alkanes. The final effluent of SWWTP had only four types of alkanes. After anaerobic unit at SWWTP, the mass percentage of total alkanes to total organic compounds was slightly decreased while its categories increased. But in the UASB, alkanes categories could be removed by 75%. Caffeine as a chemical marker could be detected only in the effluent of the aerobic process. Quantitative analysis was given. These results demonstrated that GC-MS analysis could provide an insight to the measurement of organic compounds removal.     

Innovative PCDD/F-containing gas stream generating system applied in catalytic decomposition of gaseous dioxins over V2O5-WO3/TiO2-based catalysts

Development of effective PCDD/F (polychlorinated dibenzo-p-dioxin and dibenzofuran) control technologies is essential for environmental engineers and researchers. In this study, a PCDD/F-containing gas stream generating system was developed to investigate the efficiency and effectiveness of innovative PCDD/F control technologies. The system designed and constructed can stably generate the gas stream with the PCDD/F concentration ranging from 1.0 to 100ng TEQ Nm(-3) while reproducibility test indicates that the PCDD/F recovery efficiencies are between 93% and 112%. This new PCDD/F-containing gas stream generating device is first applied in the investigation of the catalytic PCDD/F control technology. The catalytic decomposition of PCDD/Fs was evaluated with two types of commercial V(2)O(5)-WO(3)/TiO(2)-based catalysts (catalyst A and catalyst B) at controlled temperature, water vapor content, and space velocity. 84% and 91% PCDD/F destruction efficiencies are achieved with catalysts A and B, respectively, at 280 degrees C with the space velocity of 5000h(-1). The results also indicate that the presence of water vapor inhibits PCDD/F decomposition due to its competition with PCDD/F molecules for adsorption on the active vanadia sites for both catalysts. In addition, this study combined integral reaction and Mars-Van Krevelen model to calculate the activation energies of OCDD and OCDF decomposition. The activation energies of OCDD and OCDF decomposition via catalysis are calculated as 24.8kJmol(-1) and 25.2kJmol(-1), respectively.     

新型微生物菌剂在生活污水处理中的应用研究

对利用新的微生物源抗菌除臭剂去除生活污水中的COD、NH4 -N、TP及臭气的效果进行了评价.结果表明:(1)在好氧的条件下,当V菌液/V污水的比值为5/10 000～1/1 000时,COD的去除率提高幅度较大,为10%左右;当V菌液/V污水的比值为5/1 000时,对污水中NH4 -N的去除效果最好,增幅达37.62%;只有V菌液/V污水达到5/1 000以上时,对除磷才有较显著的促进作用,增幅约7%.(2)对污水除臭有很好的效果,不同嗅阈值的污水应选择适宜浓度的菌液.     

休耕对抚仙湖周边农田土壤剖面和浅层地下水中氮累积的影响

减少外源氮投入能有效降低农田土壤氮累积和地下水氮污染,休耕是减少外源氮投入的重要措施之一.为探讨农田休耕对土壤剖面和浅层地下水中氮累积的影响,以抚仙湖周边农田土壤剖面和浅层地下水为研究对象,分析了休耕前（2017年12月）和休耕后（2020年8月和2021年4月）农田0~100 cm土壤剖面氮累积和浅层地下水中氮浓度的变化及其两者的关系.结果表明:休耕显著降低了土壤剖面氮含量和储量,休耕后0~30、30~60和60~100 cm土壤剖面TN、ON、DTN、NO₃ ^--N和NH₄ ⁺-N含量分别降低18.4 %~36.5 %、16.1 %~26.8 %、54.0 %~130.2 %、59.5 %~90.8 %和60.1 %~110.6 %.休耕前0~100 cm土壤TN、ON、DTN、 NO₃ ^--N和NH₄ ⁺-N储量分别为（17.20 ±0.97）t·hm^-2、（15.50 ±1.23）t·hm^-2、（0.68 ±0.06）t·hm^-2、（266.8 ±31.17）kg·hm^-2和（18.7 ±3.04）kg·hm^-2,休耕后各形态氮储量分别下降了25.5 %、23.3 %、44.7 %、80.1 %和59.9 %.休耕也改变了浅层地下水中氮浓度和形态构成,休耕后地下水中TN、ON、NO₃ ^--N和NH₄ ⁺-N浓度分别下降了88.4 %、82.7 %、92.1 %、65.8 %,ON/TN和NH₄ ⁺-N/TN从休耕前的26 %和6 %升高至休耕后的39 %和17 %,而NO₃ ^--N/TN从休耕前的61 %降至休耕后的41 %.地下水氮浓度和形态变化与休耕前后土壤中DTN、NH₄ ⁺-N、NO₃ ^--N和地下水中pH、ORP、DO等因素密切相关.可见,休耕有效降低了农田土壤剖面氮累积,缓解了浅层地下水氮污染,有利于防止高原湖泊的水质恶化.     

基于地理探测器的中国陆地生态系统土壤有机碳空间异质性影响因子分析

中国陆地生态系统土壤有机碳库对全球生态系统碳平衡具有显著影响.为揭示土壤碳库空间分布的潜在主控因子并为今后建立碳库空间分布模型提供依据,利用地理探测器对中国陆地生态系统表层土壤(0—20 cm)有机碳密度的影响因子(气温、降水量、DEM、NDVI、陆地生态系统类型、人口密度)进行空间分异性探测和定量归因.结果表明:自然...     

高浓度有机废水处理过程中单宁、木质素的降解机理

采用UASB 接触氧化工艺对亚麻沤制废水进行了试验研究 ,结果表明 :COD去除率可达 95 %～ 97% ,BOD5去除率为 96 %～ 99%。生物难降解的单宁、木素类物质去除率为 75 %～ 86 %。对单宁、木素类物质的生物化学特性和降解机理进行了系统的分析和阐述     

炼铁厂高炉原料矿槽槽上除尘分析及应用

叙述了炼铁厂原料矿槽槽上扬尘污染的特点,及“移动式除尘通风口装置”技术在槽上除尘的应用实例。     

钢框架侧板加强型梁柱节点滞回性能研究

提出一种改进型侧板加强型梁柱节点,加强板由矩形柱侧板和直角梯形梁侧板组成,以现有的梁端翼缘侧板加强型节点试验为基础,运用有限元软件ABAQUS对11个不同细部尺寸的改进型侧板加强型节点进行循环加载作用下的模拟分析。研究结果表明,采用上下两块小矩形柱侧板加强的节点模型在循环加载作用下并未出现加强板末端梁截面的屈曲变形,但该截面的应力集中有所减小,塑性变形仍集中在节点域柱腹板上;将上下两块小矩形柱侧板更换为一整块柱侧板后,其承载能力大幅提高,且塑性变形集中在梁侧板加强末端的梁翼缘和腹板上,而节点域处于弹性工作状态,说明该种节点形式可以更好地满足"强节点弱构件"的抗震设计思想;建议柱侧板两端各伸出柱翼缘表面50mm,柱侧板的高度与钢梁截面高度相同,柱侧板厚度取6mm,梁侧板宽度边缘与柱翼缘边缘平齐,端部三角形部分长宽比可取为1∶2~1∶3,梁侧板矩形部分长度可与三角形部分长度相同,或稍大于三角形部分长度。     

Moisture distribution in sludges based on different testing methods

Moisture distributions in municipal sewage sludge, printing and dyeing sludge and paper mill sludge were experimentally studied based on four different methods, i.e., drying test, thermogravimetric-differential thermal analysis (TG-DTA) test, thermogravimetricdifferential scanning calorimetry (TG-DSC) test and water activity test. The results indicated that the moistures in the mechanically dewatered sludges were interstitial water, surface water and bound water. The interstitial water accounted for more than 50% wet basis (wb) of the total moisture content. The bond strength of sludge moisture increased with decreasing moisture content, especially when the moisture content was lower than 50% wb. Furthermore, the comparison among the four different testing methods was presented.The drying test was advantaged by its ability to quantify free water, interstitial water, surface water and bound water; while TG-DSC test, TG-DTA test and water activity test were capable of determining the bond strength of moisture in sludge. It was found that the results from TG-DSC and TG-DTA test are more persuasive than water activity test.