轮作条件下水稻-土壤系统多环芳烃的动态过程

探讨了在水稻收割-土地闲置-次年再种植水稻的轮作期间,水稻根系-土壤系统中多环芳烃的动态变化情况,尝试分析了轮作状态下水稻根系对水稻土多环芳烃的清除作用及影响因素.结果表明,在轮作期间,水稻根系中的ΣPAHs动态与空气、颗粒物等环境介质ΣPAHs相关性不明显(r0.7,p0.1),与根际土ΣPAHs呈负相关关系(r=0.7,p0.1),与根系表面积呈明显的正相关关系(r=0.8,p0.05).说明水稻根系中的ΣPAHs动态并未依赖于其它环境介质中ΣPAHs的改变,而是根据其生长状况直接吸附和吸收来自土壤的ΣPAHs.从水稻籽粒中ΣPAHs含量看,水稻对土壤多环芳烃的吸收并不影响人类的安全食用.水稻土中的ΣPAHs和活性有机碳含量在水稻进入收割期时都显著降低,经过轮作进入来年的再种植期后,又因为施用有机肥、外源输送等途径使土壤TOC和ΣPAHs增加.     

湖南烟区烤烟钾含量与土壤钾素的分布特点之间的关系

采用野外调查和室内分析相结合的方法,分析了湖南烟区烤烟钾含量与土壤钾含量的分布特点及相互关系,结果表明:湖南烟区土壤全钾质量比偏低,平均为14.92 g·kg-1,有19.90%的土样全钾质量比低于10 g·kg-1;土壤速效钾质量比较低(140.28 mg·kg-1),10.80%土壤样品中速效钾质量比≤80 mg·kg-1,63.04%土壤样品中速效钾质量比在80～160 mg·kg-1之间.不同产地间相比较,全钾质量比由高到低顺序为:凤凰、张家界、龙山、宁乡、常德、怀化、浏阳、永州、桂阳;速效钾质量比的高低顺序与全钾质量比有所不同.湖南烟区烤烟钾质量分数适中,平均为2.28%,不同等级烟叶钾质量分数的变化规律是X2F＞C3F＞B2F.各等级烟叶的钾质量分数在不同产地间差异均达到0.05显著水平.在对土壤速效钾质量比分组后,烟叶钾质量分数随着土壤速效钾质量比的增加而增加,其中在速效钾质量比较低时,烟叶钾质量分数增加速度较快.在相关分析基础上,建立了土壤养分与烤烟钾质量分数的逐步回归方程,所筛选得到的4个土壤因子(水溶性氯、有机质、交换性钙和速效钾)对烤烟钾质量分数的影响均达到极显著水平.     

基于Hydrus-1D模型的太湖流域农田系统水分渗漏和氮磷淋失特征分析

在土壤水分长期定位观测基础上,应用Hydrus-1D模型对太湖流域典型稻麦轮作农田土壤水分渗漏进行动态模拟,并结合深层土壤溶液取样及氮磷浓度测定,分析了当前耕作方式下农田水分渗漏和氮磷淋失特征。结果表明,土壤水渗漏与降雨、灌溉及前期土壤含水率有关;麦季深层渗漏量小但持续时间长,而稻季单次渗漏量大却持续时间短。模拟时段内铵态氮和可溶解性总磷的淋失主要发生在稻季,淋失量分别为2.62、0.49 kg/hm²,分别占稻麦轮作期总淋失量的96.0%、96.0%,而硝态氮淋失主要发生在麦季,淋失量为57.97 kg/hm²,占总淋失量的80.2%;无机氮淋失的主要形态为硝态氮,其淋失量占总淋失量的96.4%。综合看来,硝态氮应作为主要阻控对象,以减少农田面源污染对地下水及太湖水体的污染风险。此外,氮磷淋失在6、7月份即休耕期和水稻生长早期容易达到峰值,应得到重视。     

华北地区冬小麦干旱时空分布特征

根据作物气候指标距平,利用经验正交函数和小波分析方法,研究了华北地区冬小麦干旱的空间分布和时间演变特征。研究结果表明,主要有3种空间分布类型:以中西部为中心的全区一致型;西北、东南相反分布型,其正值中心分布在北京、霸州等区域,负值中心分布在济南、淄川、临沂等区域;东、西相反分布型,其正值中心分布在河北省东北部的唐山、秦皇岛和山东省的烟台、福山、海阳为等区域,负值中心分布在河北省的邢台、石家庄以及河南省的安阳和新乡等区域;3种空间分布型时间系数变化趋势都表明,20世纪90年代以后华北地区冬小麦干旱呈加重的趋势。     

The relationship between El Niño Southern Oscillations and cereal production in Sahel

The effect of drought on crop yield and water resources has been an important socio-economic concern in the Sahel region of Africa. The most severe droughts in the Sahel region occurred during the strong El Niño Southern Oscillation (ENSO) events. There is thus increased need to understand the stochastic relationship between such physical mechanism like ENSO and crop yield. In this paper, such a relationship is investigated using a wavelet approach. Our result shows that a statistically significant relationship exists between ENSO and cereal production in the region. In particular, El Niño events are devastation to millet yield with little or no impact on maize and sorghum production. This can be attributed to the lower length of growing period for maize and sorghum compared to millet. On the other hand La Niña events favor cereal production and mirrored sorghum yield during the La Niña years of 1973–1976. The potential value of ENSO-based rainfall forecast and socio-economic impact on local population in Sahel region are discussed.     

过磷酸钙与石灰混施对污染农田低累积玉米生长和重金属含量的影响

通过田间实验,研究了过磷酸钙和石灰混施对重金属污染农田上低累积玉米产量以及籽粒、茎叶重金属含量的影响,并分析了施用过磷酸钙和石灰后土壤pH和有效重金属含量的变化。结果表明,与单施过磷酸钙和单施石灰相比,过磷酸钙和石灰混施更能显著提高玉米生物产量,且过磷酸钙和石灰均有一定的后效。单施石灰处理、石灰与过磷酸钙混施处理都均显著降低玉米籽粒Cd、Zn和Cu含量,其中以中量(0.4 kg/m2)、高量石灰(0.6 kg/m2)+中量过磷酸钙(0.2kg/m2)处理效果最佳,其玉米籽粒Cd、Zn和Cu含量降低到了国家食品卫生标准允许的含量水平。石灰处理均不同程度地提高了玉米籽粒Pb含量,配施过磷酸钙也不能明显降低玉米籽粒Pb含量,但仍低于饲料卫生标准允许的含量水平。另外,单施石灰处理和石灰与过磷酸钙混施处理均显著降低了玉米茎叶Cd、Pb、Zn和Cu含量,可以安全用作有机肥。     

珠芽魔芋弥勒种——从低产到优质高产作物的希望之星

珠芽魔芋是东南亚地区的特色野生魔芋种,适宜在高温高湿环境生长。以珠芽魔芋人工诱导开花进行规模化无性育种,可将魔芋繁殖系数从1位数提高到约330倍。采用催苗技术让种子及叶面球茎提早出苗,可显著延长魔芋生长周期,使魔芋种植周期由3年缩短为1年,实现当年种植收获商品芋,从而避免魔芋种植过程中种植材料反复休眠的固有特性,可使魔芋从低产作物提升为优质高产作物,显著降低种植风险,使魔芋总量大幅增长,市场推广前景十分广阔。     

Improved SWAT Model Performance With Time-Dynamic Voronoi Tessellation of Climatic Input Data in Southern Africa1

Andersson, Jafet C.M., Alexander J.B. Zehnder, Bernhard Wehrli, and Hong Yang, 2012. Improved SWAT Model Performance with Time-Dynamic Voronoi Tessellation of Climatic Input Data in Southern Africa. Journal of the American Water Resources Association (JAWRA) 48(3): 480-493. DOI: 10.1111/j.1752-1688.2011.00627.x Abstract: In this study, we compared two approaches to obtain climatic time series for the Soil and Water Assessment Tool (SWAT), namely the conventional centroid method and time-dynamic Voronoi tessellation, and assessed the performance of SWAT in simulating discharge and smallholder maize yields in Southern Africa. Climatic time series were estimated with each method. The Voronoi method utilized all available precipitation and temperature data, but the centroid method used only 14.5 and 82.5%, respectively. After centroid processing, sub-basin time series were on average 42 and 63% incomplete, respectively. After Voronoi processing, all time series were complete. SWAT was fed with each climate dataset. Each model setup was independently calibrated and validated against discharge and maize yield. Similar model performance was obtained with both methods for yield. The root mean squared error during calibration was 0.26 and 0.27 t ha⁻¹ for the centroid and Voronoi methods, respectively (p-value: 0.80). However, daily discharge simulations improved significantly with the Voronoi method. The coefficient of determination increased from 0.24 to 0.39 in the calibration period (p-value: 9.6 × 10⁻¹³) and from 0.41 to 0.48 in the validation period (p-value: 3.1 × 10⁻³). The Voronoi method improved the simulation of the river flow regime. The largest improvements were obtained in data scarce situations, at high spatial and temporal resolution, and where the centroid method performed the worst.     

近50年辽宁省作物生长季气候条件变化及对农业生产的影响

利用辽宁省35个气象观测站点1956-2005年的逐月地面观测资料,对辽宁省近50年的农业气候条件的长期变化情况和空间分布特征进行了详细的分析,并初步分析了农业气候条件的变化对农业生产的影响。结果表明：近50年辽宁省生长季（4-9月）日照时数明显减少,每10年减少29.4 h;生长季日照百分率减少也很明显,平均每10年减少1.2%;生长季降水量呈微弱的减少趋势,蒸发量明显减少,平均每10年减少17.3 mm。潜在蒸发量也呈明显的减少趋势。生长季≥10℃界限温度的积温值在近50年明显增加,且全省≥10℃界限温度开始的日期明显提前,大部分地区近50年提前6 d左右。辽宁省生长季3 350℃积温等值线在最近的10年里有明显的北移和东移。     

Design of Optimal Noise Hazard Control Strategy With Budget Constraint

An analytical design procedure to determine optimal noise hazard control strategies for industrial facilities is presented. Its objective is to determine a set of appropriate noise controls to eliminate or reduce noise levels so that workers ‘ daily noise exposure does not exceed a permissible level. From a given noise control budget, engineering controls will be firstly implemented, followed by administrative controls, and then the use of hearing protection devices. Six optimization models are developed and sequentially applied to select appropriate noise controls without exceeding the budget. Numerical examples are presented to demonstrate the application of the proposed design procedure.