Modeling soil water dynamics in a drip-irrigated intercropping field under plastic mulch

Intercropping, drip irrigation, and the use of plastic mulch are important management practices, which can, when utilized simultaneously, increase crop production and save irrigation water. Investigating soil water dynamics in the root zone of the intercropping field under such conditions is essential in order to understand the combined effects of these practices and to promote their wider use. However, not much work has been done to investigate soil water dynamics in the root zone of drip-irrigated, strip intercropping fields under plastic mulch. Three field experiments with different irrigation treatments (high T1, moderate T2, and low T3) were conducted to evaluate soil water contents (SWC) at different locations, for different irrigation treatments, and with respect to dripper lines and plants (corn and tomatoes). Experimental data were then used to calibrate the HYDRUS (2D/3D) model. Comparison between experimental data and model simulations showed that HYDRUS (2D/3D) described different irrigation events and SWC in the root zone well, with average relative errors of 10.8, 9.5, and 11.6 % for irrigation treatments T1, T2, and T3, respectively, and with corresponding root mean square errors of 0.043, 0.035, and 0.040 cm³ cm^?3, respectively. The results showed that the SWC in the shallow root zone (0–40 cm) was lower under non-mulched locations than under mulched locations, irrespective of the irrigation treatment, while no significant differences in the SWC were observed in the deeper root zone (40–100 cm). The SWC in the shallow root zone was significantly higher for the high irrigation treatment (T1) than for the low irrigation treatment, while, again, no differences were observed in the deeper root zone. Simulations of two-dimensional SWC distributions revealed that the low irrigation treatment (T3) produced serious severe water stress (with SWCs near the wilting point) in the 30–40 cm part of the root zone, and that using separate drip emitter lines for each crop is well suited for producing the optimal soil water distribution pattern in the root zone of the intercropping field. The results of this study can be very useful in designing an optimal irrigation plan for intercropped fields.     

Sensitivity analysis of optimal operation of irrigation supply systems with water quality considerations

A model for optimal operation of water supply/irrigation systems of various water quality sources, with treatment plants, multiple water quality conservative factors, and dilution junctions is presented. The objective function includes water cost at the sources, water conveyance costs which account for the hydraulics of the network indirectly, water treatment cost, and yield reduction costs of irrigated crops due to irrigation with poor quality water. The model can be used for systems with supply by canals as well as pipes, which serve both drinking water demands of urban/rural consumers and field irrigation requirements. The general nonlinear optimization problem has been simplified by decomposing it to a problem with linear constraints and nonlinear objective function. This problem is solved using the projected gradient method. The method is demonstrated for a regional water supply system in southern Israel that contains 39 pipes, 37 nodes, 11 sources, 10 agricultural consumers, and 4 domestic consumers. The optimal operation solution is described by discharge and salinity values for all pipes of the network. Sensitivity of the optimal solution to changes in the parameters is examined. The solution was found to be sensitive to the upper limit on drinking water quality, with total cost being reduced by 5% as the upper limit increases from 260 to 600 mg Cl l^–1. The effect of income from unit crop yield is more pronounced. An increase of income by a factor of 20 results in an increase of the total cost by a factor of 3, thus encouraging more use of fresh water as long as the marginal cost of water supply is smaller than the marginal decrease in yield loss. The effect of conveyance cost becomes more pronounced as its cost increases. An increase by a factor of 100 results in an increase of the total cost by about 14%. The network studied has a long pipe that connects two distinct parts of the network and permits the supply of fresh water from one part to the other. Increasing the maximum permitted discharge in this pipe from 0 to 200 m³ h^–1 reduces the total cost by 11%. Increasing the maximum discharge at one of the sources from 90 to 300 m³ h^–1 reduces the total cost by about 8%.     

“WaterMan”: an on-farm water management game with heuristic capabilities

A modern computer-based simulation tool (WaterMan) in the form of a game for on-farm water management was developed for application in training events for farmers, students, and irrigators. The WaterMan game utilizes an interactive framework, thereby allowing the user to develop scenarios and test alternatives in a convenient, risk-free environment. It includes a comprehensive soil water and salt balance calculation algorithm. It also employs heuristic capabilities for modeling all of the important aspects of on-farm water management, and to provide quantitative performance evaluations and practical water management advice to the trainees. Random events (both favorable and unfavorable) and different strategic decisions are included in the game for more realism and to provide an appropriate level of challenge according to player performance. Thus, the ability to anticipate the player skill level, and to reply with random events appropriate to the anticipated level, is provided by the heuristic capabilities used in the software. These heuristic features were developed based on a combination of two artificial intelligence approaches: (1) a pattern recognition approach and (2) reinforcement learning based on a Markov decision processes approach, specifically the Q-learning method. These two approaches were combined in a new way to account for the difference in the effect of actions taken by the player and action taken by the system in the game world. The reward function for the Q-learning method was modified to reflect the suggested classification of the WaterMan game as what is referred to as a partially competitive and partially cooperative game.     

等离子体辅助玉米醇溶蛋白自组装纤维化的工艺

植物蛋白纤维由于其独特的结构和极高的纵横比可作为良好的疏水性生物活性物质的递送载体。为了提高玉米醇溶蛋白在酸热诱导下的纤维化程度,该研究采用低温等离子体技术辅助完成玉米醇溶蛋白自组装纤维化,探究诱导过程中各因素对玉米醇溶蛋白纤维化程度的影响机制,并通过单因素和响应面试验获得最优纤维化工艺。硫黄素T（ThT）荧光强度结果显示,采用等离子体辅助酸热诱导可以有效提高玉米醇溶蛋白的纤维化程度。通过单因素和响应面优化试验获得了制备纤维化玉米醇溶蛋白的优化工艺为等离子体处理功率64 W,处理时间61 s,加热时间为10 h,加热温度70 ℃,蛋白质量浓度30 mg/mL。在此条件下纤维化玉米醇溶蛋白ThT荧光强度可达2 272±23,显著高于未经等离子体处理的纤维化玉米醇溶蛋白（1 239±19）（P＜0.05）。对傅里叶变换红外光谱中酰胺I 区结果分析表明,等离子体处理使玉米醇溶白中β-折叠结构增加,α-螺旋结构减少。透射电子显微镜观察到玉米醇溶蛋白经过纤维化后颗粒粒径明显下降,其纤维结构是由球状蛋白颗粒沿水平方向线性聚集而成,采用等离子体辅助可诱导形成更多的玉米醇溶蛋白纤维体结构。研究结果为疏水性植物蛋白实现高效自组装纤维化提供参考。     

滋味物质在不同交联度鱼糜凝胶中的释放动力学分析

为探讨滋味物质在不同交联度鱼糜凝胶中的释放规律并揭示其释放机制,该研究以氯化钠、蔗糖和谷氨酸钠分别为鱼糜凝胶咸味、甜味和鲜味的代表滋味物质,通过感官评价、释放动力学模型拟合和模拟咀嚼释放等方法,分析滋味物质在不同交联度鱼糜凝胶中的释放规律。结果表明,随着交联度的增加,人体对咸味的感知逐渐降低而对鲜味的感知逐渐增强,并当交联度大于42.2%时,咀嚼破碎显著提高了鱼糜凝胶咸味和鲜味的感知（P<0.01）。氯化钠和蔗糖的释放动力学曲线符合准一级动力学模型,而谷氨酸钠的释放则符合准二级动力学模型。随着交联度的增加,鱼糜凝胶在模拟咀嚼过程中氯化钠和蔗糖的释放量先降后升,分别在交联度为42.2%和51.5%时取得最小值（4.54和3.38 mg/g）;而谷氨酸钠的咀嚼释放量则逐渐增加。相关性分析结果表明,氯化钠和蔗糖在鱼糜凝胶中的释放主要与网络结构和化学作用力相关,谷氨酸钠的释放主要与凝胶质地、凝胶持水性和化学作用力相关。综上,滋味物质在鱼糜凝胶中的释放行为受滋味物质种类、凝胶质地以及凝胶与滋味物质的相互作用等多方面的影响,且凝胶在咀嚼过程中较高的破碎程度增强了滋味物质的释放与感知。     

西藏“一江两河”流域生态系统服务变化及权衡与协同关系研究

为使环境资源得到高效配置,明晰生态系统服务间权衡关系是重要前提。以一江两河流域为对象,基于InVEST模型对该区1990—2018年的土壤保持、水源涵养和固碳服务进行动态评估,并采用相关分析法探讨了流域、县域尺度下各服务间的权衡关系。结果表明:(1)1990—2018年,土壤保持量和碳储量呈波动增加趋势,产水量呈减少趋势。单位面积土壤保持量、产水量和碳储量的高值区均分布在流域东部的拉萨河河谷地区。(2)流域尺度下,2010年水源涵养服务与固碳服务间表现出权衡关系,其余年份各服务间均呈现出协同关系; 县域尺度下,各服务间关系也多为协同关系,但具有较强的空间异质性。(3)热点制图显示,1990—2018年1类区占比最大且呈增加趋势,主要地类为低植被覆盖草地; 0类和2类区占比增加,主要地类分别为沙地和高植被覆盖草地; 3类区占比有所减少,主要地类为高植被覆盖草地和灌木林。由此可得,研究区3种生态系统服务具有较强的时空异质性,各服务间以协同关系为主,且随时空变化而发生着强弱变化。     

PCB removal,soil enzyme activities,and microbial community structures during the phytoremediation by alfalfa in field soils

Purpose  

An in situ phytoremediation trial was developed in order to investigate the function of alfalfa during a 2-year bioremediation of an agricultural soil contaminated with polychlorinated biphenyls (PCBs). The study was conducted with the aim to better understand the application potential of PCB phytoremediation at field scale.     

Hydroxycinnamoylmalic acids and their methyl esters from pear (Pyrus pyrifolia Nakai) fruit peel

Two novel caffeoylmalic acid methyl esters, 2-O-(trans-caffeoyl)malic acid 1-methyl ester (6) and 2-O-(trans-caffeoyl)malic acid 4-methyl ester (7), were isolated from pear (Pyrus pyrifolia Nakai cv. Chuhwangbae) fruit peels. In addition, 5 known hydroxycinnamoylmalic acids and their methyl esters were identified: 2-O-(trans-coumaroyl)malic acid (1), 2-O-(cis-coumaroyl)malic acid (2), 2-O-(cis-coumaroyl)malic acid 1-methyl ester (3), 2-O-(trans-coumaroyl)malic acid 1-methyl ester (4), and 2-O-(trans-caffeoyl)malic acid (phaselic acid, 5). The chemical structures of these compounds were determined by spectroscopic data from ESI MS and NMR. Of all the isolated compounds, five hydroxycinnamoylmalic acids and their methyl esters (2-4, 6, 7) were identified in the pear for the first time.     

河南省降雨侵蚀力时空变异特征

利用河南省119个气象台站自建站始至2003年的逐日降雨量资料,计算其所代表县(市)的逐年与平均降雨侵蚀力,并利用GIS等工具分析河南省降雨侵蚀力的时空变异特征。结果表明:河南省多年年均降雨侵蚀力总体趋势是由北向南递增,最大值出现在南部的新县、鸡公山、商城与桐柏、平舆,其值均超过7 000 MJ.mm/(hm2.h.a);河南省多年年均降雨侵蚀力排序结果可分为5个区域等级,基本与等值线一致;河南省各地的降雨侵蚀力在不同年份变异较大,FFT(快速傅立叶变换)表明无明显的年际周期性规律;河南省降雨侵蚀力的年内变化趋势表现为单峰型,侵蚀主要发生在7—9月份,集中度在北部区域均超过60%;河南省降雨侵蚀力与年侵蚀性降雨量或年侵蚀性降雨量和逐日侵蚀性降雨量之间存在极显著的线性相关性,相关系数分别为0.967 2和0.994 2。     

稻田沟渠-湿地系统的碳氮稳定同位素组成特征

由于稳定同位素在特定污染源中具有特定的组成,在污染物质迁移转化过程中作为示踪剂而广泛应用。针对目前农业面源污染较为严重的现状,该文利用碳氮稳定同位素研究了灌区内外源物输入对稻田沟渠-湿地系统的贡献。结果表明,水中颗粒性有机物(particulate organic matter,POM)由于受到光照、营养物质不同导致POM在各采样点组成不同,δ13C变化范围较大,均值为-27.8‰,与大型水生植物和浮游植物接近,此类植物可能是POM的主要来源。水中δ13CDIC(dissolved inorganic carbon,DIC)与浮游植物呈线性相关,浮游动物δ13C与浮游植物存在一定相关性,而浮游植物与POM之间不存在显著性差异,说明研究区内浮游动物对內源有机碳的利用主要是取食浮游植物低持斜聿愠粱?δ13C值变化范围在-27.2‰～-21.8‰之间,明显高于水体POM含量,说明表层沉积物存在比颗粒有机物更富集碳的藻类与陆源碎屑等物质。各采样点颗粒有机物δ15N值的范围3.1‰～4.2‰,平均值为3.6‰,其中湿地δ15N高于其他采样点。沉积物δ15N平均值为-0.6‰,与大气中N2较为接近。