Reconstructed cropland in the mid-eleventh century in the traditional agricultural area of China: implications of comparisons among datasets

Reconstructions of historical cropland area and spatial distribution are necessary for studying human effects on the environment due to agricultural development. To understand the current status of reconstructions of cropland area and its spatial distribution in the mid-eleventh century in the traditional agricultural area of China, we compared three available datasets: the historic cropland inventories-based HE dataset, the population-based History Database of the Global Environment (HYDE) dataset, and the PJ dataset. The results indicate that the HYDE and PJ datasets estimated the regional mean cropland area fraction (a ratio of cropland area to total land area, hereafter, CAF) for the study area to be 0.12 and 0.09, respectively, both of which were lower than the HE estimation of 0.18. Moreover, both the HYDE and PJ datasets have a poor ability to capture the spatial distribution of the historical CAF. The HYDE dataset overestimated the cropland area in North China and underestimated the cropland area in the Yangtze River reach. The HYDE dataset also overestimated the cropland area along the great rivers in North China. The PJ dataset underestimated the cropland area in the old agricultural area and overestimated the cropland area in the relatively new agricultural area. These incorrect spatial distributions from the HYDE and PJ datasets mainly resulted from the underestimation of the historical population and an incorrect approach for the spatial allocation of cropland within China. The incorrect approach was mainly derived from a poor understanding of the historic spatial distribution of cropland. Using the expert knowledge of local historians may be an effective method to reduce the uncertainties in the global historic cropland reconstruction.     

泾阳地磁台数字化与模拟资料的对比分析

本文选取泾阳地磁台2007年FHD-1核旋磁力仪和CB3磁变仪观测数据采用日变幅形态、日均值年变形态、总场21点值年变形态等方法做对比分析。结果表明:两种观测一致性较好,说明数字化仪器观测的数据是可靠的,但是数字化仪器还存在易受外界环境干扰,稳定性不好的问题,需要工作人员按规范调试仪器,认真维护与管理。     

“双碳”目标约束下农作物种植结构对农业绿色全要素生产率的影响研究：以陕西省为例

在“双碳”目标的约束下，探究农作物种植结构对农业绿色全要素生产率的影响程度能够有效促进农业农村高质量发展。基于2000—2019年陕西省10个地市的面板数据，运用方向距离函数和Global Malmquist-Luenberger指数对“双碳”目标约束下的农业绿色全要素生产率进行测算，采用Tobit回归模型分析农作物种植结构变化对农业绿色全要素生产率的影响因子，并探讨影响农业绿色全要素生产率的其他潜在因素。研究表明：陕西省农业绿色全要素生产率在“双碳”目标的约束下，总体有所提升，但各地市间存在地区差异性；粮食作物种植面积的增长对农业绿色全要素生产率具有显著的积极影响；农户生计保障对农业绿色全要素生产率有显著的正向作用，农业机械化水平和自然环境条件均对农业绿色全要素生产率有显著的负向作用。优化农作物种植结构、减少农业碳排放量以及提升农业绿色全要素生产率，是全面促进乡村振兴、加快农业高质量发展的关键。     

双酚A对豚鼠的免疫毒性

为了研究BPA(bisphenol A,双酚A)对豚鼠的免疫毒性,经口灌服,以不同剂量(500、1 000 mg/kg)染毒14 d后接种O型口蹄疫疫苗,通过分析脏器系数、淋巴细胞增殖能力、NK细胞(natural killer cell,自然杀伤细胞)活性、特异性抗体水平以及细胞免疫水平,评价BPA染毒剂量对豚鼠体液免疫和细胞免疫的影响.结果表明:与阴性对照组相比,BPA染毒后豚鼠体质量增加,心脏、肝脏、肾脏、脑、脾脏和卵巢体质量也增加,相应脏器系数升高；而胸腺、睾丸和附睾萎缩,相应脏器系数降低.NK细胞数量虽有增加,但变化不显著；BPA染毒引起NK细胞对靶细胞的杀伤能力显著下降,并且随着BPA染毒剂量的增加,其对靶细胞的杀伤能力显著下降；淋巴细胞刺激指数显著升高,并与染毒剂量呈正相关.BPA对豚鼠的特异性抗体水平有一定抑制作用,并且随着染毒剂量的增加该抑制作用愈发显著.IL-2(白介素2,interleukin-2)和IFN-γ(干扰素-γ,interferon)水平低于阴性对照组,而IL-4(白介素4,interleukin-4)水平高于阴性对照组；随着染毒剂量的增加,淋巴细胞增殖能力、IL-2和IFN-γ水平显著降低,而IL-4水平显著升高.研究显示,BPA会损伤豚鼠的免疫器官,抑制机体产生体液免疫和细胞免疫,导致免疫功能紊乱.      

Mobility and sulfidization of heavy metals in sediments of a shallow eutrophic lake, Lake Taihu, China

The technique of DGT (diffusive gradients in thin films) using three diffusive gel thicknesses was applied to estimate the mobility and bioavailability of heavy metals in sediments and porewater of Lake Taihu, China. The DGT results showed significantly positive correlations between Co, Pb, Cd and Mn, and Ni and Fe concentrations in porewater. Cu and Zn showed a significantly negative correlation with Mn, due to Cu combination with carbonates and Zn derived from agricultural pollution, respectively. The rank order of average concentrations of Co, Ni and Cd at each station was DGT_1.92 > DGT_0.78 > DGT_0.39, suggesting stronger resupply from sediments to porewater when using thicker diffusive gels. Comparing centrifugation and DGT measurements, Co, Ni and Cd are highly labile; Mn and Fe are moderately labile; and Cu, Zn and Pb are slightly labile. The variations of AVS concentrations in sediment cores indicate that metal sulfides in deeper layers are easily diffused into surface sediments.     

2014年11-12月国内环境事件

简要统计了2014年11-12月国内发生的各种环境事件63起,包括沙尘天气2起,污染事件16起,地震30起,山体滑坡和泥石流6起,以及其他自然灾害9起.