Root studies on grass species in a semi-arid South Africa along a degradation gradient

Understanding changes in hydrological characteristics of rangeland ecosystems with degradation is essential when making rangeland management decisions in arid and semi-arid areas to ensure sustainable animal production. The impact of rangeland degradation on root production, root/shoot ratio and water-use efficiency was therefore determined for a semi-arid rangeland, over a 7-year period (1999/00 to 2005/06 growing seasons).Water-use efficiency (WUE) is defined as the quantity of above- and/or belowground phytomass produced over a certain period of time per unit of water evapotranspired. Sampling was from rangeland artificially maintained in three different rangeland conditions, viz. good, moderate and poor.As much as 86, 89 and 94% of the roots for rangelands in good, moderate and poor conditions, respectively, occurred at a depth of less than 300 mm. Root mass was strongly seasonal with the most active growth taking place during March and April. Root mass appears to be greater than aboveground phytomass for this semi-arid area, with an increase in roots in relation to aboveground phytomass production with rangeland degradation. The mean monthly root/shoot ratios for rangelands in good, moderate and poor conditions were 1.16, 1.11 and 1.37, respectively. Rangeland degradation significantly lowered above- and belowground phytomass production as well as the water-use efficiency. The mean WUE (root production included) were 4.79, 3.54 and 2.47 kg ha⁻¹ mm⁻¹ for rangelands in good, moderate and poor conditions, respectively. These water-use efficiency observations are among the few also including root production in its calculation. As a proportion of annual phytomass, litter fall of 7.17, 4.64 and 3.41% was obtained for rangelands in good, moderate and poor conditions, respectively. Increasing rangeland degradation increased the replacement of total root system by about 10 months and decomposition time of litter by 6 months.The importance of a well-established root system for sustainable production in the semi-arid rangelands cannot be overemphasized.     

甘蔗糖蜜酒精生产废水治理——论酒糟的循环使用

将酒精发酵系统看成是一个由许多相互关联的化学和生物化学反应构成的复杂反应网络系统，并应用平衡和平衡移动原理，对有糟液参与二次发酵的系统进行分析，指出：发酵系统中所有副反应都有一个反应极限，当达到或超过极限时，副反应将受到抑制，因此，副产物在发酵系统不会形成累积．不会影响正常发酵，以此为酒糟循环使用提供理论支持。     

Effects of load carriage and work boots on lower limb kinematics of industrial workers

Load and footwear condition are two crucial elements varying the kinematic responses during walking, which probably lead to chronic injury. Fifteen healthy male individuals with no obvious gait abnormalities participated in this study. Apart from a no-load condition, four external load conditions with two load levels were investigated. Work boots were compared with running shoes to determine footwear effects. Significant impacts were found for lower limb range of motion at certain joints when carrying loads. A greater hip and ankle flexion–extension while wearing the work boots indicated that participants needed to lift the leg higher to complete toe clearance off the walking surface. Work boots also increased the vertical excursion of the center of body mass, which may impact body balance and induce falling. No significant influencing pattern of carrying modes was found, which was probably due to the light load and relatively stable mode of shoulder carrying.     

Estimating Annual Groundwater Evapotranspiration from Phreatophytes in the Great Basin Using Landsat and Flux Tower Measurements

Escalating concerns about water supplies in the Great Basin have prompted numerous water budget studies focused on groundwater recharge and discharge. For many hydrographic areas (HAs) in the Great Basin, most of the recharge is discharged by bare soil evaporation and evapotranspiration (ET) from phreatophyte vegetation. Estimating recharge from precipitation in a given HA is difficult and often has significant uncertainty, therefore it is often quantified by estimating the natural discharge. As such, remote sensing applications for spatially distributing flux tower estimates of ET and groundwater ET (ET_g) across phreatophyte areas are becoming more common. We build on previous studies and develop a transferable empirical relationship with uncertainty bounds between flux tower estimates of ET and a remotely sensed vegetation index, Enhanced Vegetation Index (EVI). Energy balance‐corrected ET measured from 40 flux tower site‐year combinations in the Great Basin was statistically correlated with EVI derived from Landsat imagery (r² = 0.97). Application of the relationship to estimate mean‐annual ET_g from four HAs in western and eastern Nevada is highlighted and results are compared with previous estimates. Uncertainty bounds about the estimated mean ET_g allow investigators to evaluate if independent groundwater discharge estimates are “believable” and will ultimately assist local, state, and federal agencies to evaluate expert witness reports of ET_g, along with providing new first‐order estimates of ET_g.     

上海城区PM2.5中有机组分及硝基芳香化合物分布特征

硝基芳香化合物（NACs）是细颗粒物中含氮化合物的重要组成部分,研究其在大气中的污染特征和季节变化,有助于表征大气细颗粒物中含氮有机化合物特性,并为城市氮氧化物削减提供科学支撑.采集并分析了上海城区2018年3月～2019年2月大气PM_2.5样品,采用超高效液相色谱-轨道阱质谱（UPLC-Orbitrap MS）在PM_2.5样品中定性检测到了2 439～3 695个有机物,内标法定量了9种NACs,春季ρ（NACs）范围为3.12～16.8 ng·m^-3,平均值为9.31 ng·m^-3;夏季ρ（NACs）范围为1.05～9.70 ng·m^-3,平均值4.16 ng·m^-3;秋季ρ（NACs）范围为2.87～36.27 ng·m^-3,平均值9.84 ng·m^-3,冬季ρ（NACs）范围为4.83～56.23 ng·m^-3,平均值为22.37 ng·m^-3. 9种硝基芳香化...     

海洋资源资产负债表的编制问题初探

编制海洋资源资产负债表是推动我国生态文明建设、促进我国国民经济发展的必要手段,因而受到学术界的广泛关注。通过对过往研究成果的梳理,可以看出目前我国海洋资源资产负债表的编制工作仍处于起步阶段。本文对我国编制海洋资源资产负债表的意义进行了研究,同时对海洋资源资产负债表编制工作当中的难点与重点问题进行了探讨,分析得出目前存在概念不清晰、分类不明确、核算不准确、数据不完备四大问题,并有针对性地提出了政策建议。     

改进二重源解析技术应用中需注意的几个重要问题

对改进二重源解析技术的计算步骤进行了介绍,并对计算中需要注意的几个主要问题进行了阐述,其中包括成分谱的建立、解析参数的范围以及独立源的选取原则。     

蜂蜜中氯霉素残留的检测及净化方法研究

建立了反相高效液相色谱-离子阱质谱法检测蜂蜜中氯霉素残留的方法.前处理采用改良的QuEChERS方法进行快速提取和净化.采用初级次级胺进行固相分散净化,可有效吸附蜂蜜中的糖类及有机色素等杂质.提取物在流动相甲醇:水(0.2%乙酸胺)=45:55(体积比)中,用整体色谱柱进行快速分离和质谱检测.并对MS检测中2种离子化方式(电喷雾ESI及大气压化学APCI)、各种离子化方式下正负离子模式及离子检测方法(总离子检测TIC和选择性离子监测MRM)进行了综合比较,最终确定采用电喷雾电离法(ESI)负离子模式、多反应离子监测(MRM)对氯霉素进行定性定量分析.在0.2～200μg/kgg添加浓度下,添加回收率水平在78%～93%间,变异系数在3.9%以下.该方法的检出限为0.1μg/kg,在0.1～100 μg/L浓度范围内,线性方程为y=58.753x 34867,相关系数R2=0.999 5.     

潜流湿地处理不同浓度有机污水的差异分析

通过供氧平衡及物质平衡理论分析和实证研究,探讨根系泌氧、水中自带溶解氧、植物吸收营养物在湿地净化中的贡献,并通过落空运行来启动大气复氧.结果表明,当处理Ⅳ类以下地表水时,根系泌氧和水中携氧可使基质内为好氧环境、出水DO>0;植物吸收和介质吸附可使N、P去除稳定.当处理生活污水时,植物供氧不足,基质内为缺氧/厌氧环境、铵氧化细菌和亚硝酸氧化菌数量只有氨化细菌的1/1 000～1/100,出水DO≈0,使基质易堵塞;植物吸收和介质吸附有限,氮去除率≤20%;磷去除率随介质吸附容量的饱和逐渐下降,运行前3个月去除率为54%,运行1a以后降低到5%.潜流湿地处理生活污水时污染负荷远大于植物供氧和吸收营养物的上限,是其存在技术局限的根本原因.启动大气复氧是湿地工艺改进的一个重要方向,预沉-常规湿地对COD、NH₄⁺-N、TN、TP的去除率为79%、34%、36%、34%,预沉-落空湿地则为79%、88%、14%、69%,必须合理利用大气复氧才能实现去除总氮的最终目的.     

Human Impacts on Land Cover and Water Balances in a Coastal Mediterranean County

We analyzed the effects of changes in land cover on the water balance in Spain’s Marina Baixa County, on the Mediterranean coast. To reveal how different land management strategies have affected the area’s environment, four municipalities within the same catchment were studied: Benidorm, Callosa d’en Sarrià, Beniardà, and Guadalest. In the municipalities of Callosa and Benidorm, the proportion of the area covered by woodland declined by 4.2% and 30.2%, respectively, and woodland was replaced by agriculture and urban development. The abandonment of farmland produced a 17% increase in the proportion of the area covered by vegetation in Guadalest and Beniardá, where frequent forest fires have exacerbated a decrease in the area of pine woodland. Tourism development in Benidorm has been accompanied by an increase in the transportation infrastructure and by an expansion of areas with an impermeable surface, with the lowest level of infiltration into the aquifer system. These changes have generated a net water deficit in Callosa and Benidorm of more than 6 Mm³/year, creating a high demand for water imported from other municipalities (Guadalest and Beniardá) or from outside of the county to maintain the sustainability of the current water management strategies. The Marina Baixa case study is representative of many of the world’s coastal areas that are undergoing rapid urban development based on an inappropriate understanding of human progress based mainly on economic development and thus provides insights into water management in other areas.