广东省粮食供需时空格局

粮食供需差真实反映粮食供需的状况,对于保障粮食安全有着重要意义.研究以广东省为例,利用1994-2009年粮食生产及常住人口数据,构建空间集聚-扩散度和贡献指标,分析粮食供需差的空间分异,并采用格兰杰因果检验探析城市化与粮食供需差的因果关系.研究结果表明,1994-2009年,广东省的粮食供需差总体呈现上升的趋势和扩散的特征,粮食短缺从局部现象转变为普遍现象;21个地级市的粮食供需差趋于平稳、缓慢增长,且增长差异呈现变小的趋势.主导粮食需求和高贡献率地级市的空间分布特征分别是集聚→扩散→集聚与扩散;粮食供需差贡献存在显著的空间差异性,可以将所有的地级市划分为高增长指数、高贡献率,高增长指数、低贡献率,低增长指数、高贡献率,低增长指数、低贡献率4种不同的类型;而格兰杰因果检验表明,在城市化水平较低地区,城市化水平的提升将直接引起人均粮食供需差的变大.     

基于SWAT-WEAP联合模型的西辽河支流水资源脆弱性研究

气候变化与人类活动对水循环及水资源安全的影响是近代水科学面临的主要科学问题。以西辽河支流老哈河流域为研究区,探索了一种水文模型耦合方法(SWAT-WEAP),以水短缺量为指标,同等考虑水资源供给端与需求端,对气候变化与不同人类利用情景下水资源系统脆弱性进行定量分析,结果表明:①暖干化气候情景比暖湿化气候情景明显加剧了老哈河流域水资源系统的脆弱性,降水减少10%导致的水短缺量比降水导致10%所缓解的短缺量要多31.17%;②气候变化对流域农业灌溉用水影响最大,对城乡生活用水和工业用水影响相对很小;③老哈河流域水资源系统脆弱性的主要驱动力之一源自农业不合理灌溉,发展畜牧业、 改变种植结构与高效节水灌溉是缓解水短缺、 降低水资源系统脆弱性最为有效的措施,也是应对气候变化最为有效的方式;④基于供水端的措施(如水库)在暖干化气候时由于水资源供给来源受限,其缓解作用有所减弱。     

基于水资源供需平衡机制的安徽省干旱时空分布

基于目前大多数干旱研究偏于气象、水文和农业干旱,不能较好地反映供求矛盾,论文根据水资源供需成因的旱情评价方法,对安徽省2001-2005年的旱情时空分布进行了综合分析。研究发现,在时间上,安徽省2001和2005两年同为中度干旱,但差别甚大,平水年份的2005年的旱情等级数(Drought Index,DI)(1.485 9)却远高于偏枯的2001年(DI 0.890 9);在空间上,平水年份的2005年总体为中度干旱,但各地市区域差异明显,经济发展水平较高、用水量大的城市干旱严重(如合肥、淮南、马鞍山、芜湖市等)。淮北(DI -0.146 1,无旱)与芜湖(DI 2.466 2,严重干旱)两市水资源自然量和人口数量都相当,但旱情迥异。研究发现,造成上述旱情差异的根本原因是由于社会经济发展水平的差异而引起的水资源供需量的巨大差别。研究认为,在现代的社会背景下,单独的气象干旱、农业干旱和水文干旱已不能全面反映旱情状况,而社会经济干旱对旱情的描述更为直观,采用水资源供需平衡机制对旱情的评价也更符合实际。     

基于Logistic回归和NFCA的水资源供需风险分析模型及其应用

我国城市水资源供需研究多从需水的角度考虑供需平衡,而忽略了供需风险的研究。针对这一问题,论文从危险性、暴露性和脆弱性的角度构建水资源供需风险指标体系,建立了基于Logistic回归和非线性模糊综合评价(NFCA)的供需风险分析模型。考虑供水的随机不确定性,以北京市为例,研究多种不同来水条件下的风险,结果表明:在1956-2007年的来水条件下,2020年固有风险均为一级风险;利用外调水和再生水后,现实风险中三级和四级风险占75%,一级和二级风险仍然占了25%。因此在降水量很小的情况下,水资源供需风险仍然处于较高水平。     

Trace element concentration in wheat grain: results from the Swedish long-term soil fertility experiments and national monitoring program

Concentrations of trace elements in wheat grain sampled between 1967 and 2003 from the Swedish long-term soil fertility experiments were analyzed using ICP-MS. The long-term effect of inorganic and organic fertilization on trace metal concentrations was investigated including the impact of atmospheric deposition and myccorhiza, whereas other factors such as soil conditions, crop cultivar, etc. are not discussed in this paper. Mean values derived from 10 experimental sites were reported. Significantly declining Pb and Cd concentrations in wheat grain could be explained by lower atmospheric deposition. Mean Se contents in all samples were 0.031 mg kg⁻¹ grain dry weight. No samples had sufficiently high Se concentrations for human (0.05 mg Se kg⁻¹) or animal demand (0.1 mg Se kg⁻¹). Concentrations of Co in wheat grain were extremely low, 0.002–0.005 mg Co kg⁻¹ grain dry weight, and far below the minimum levels required by animals, which applied to all fertilizer treatments. A doubling of Mo concentrations in grain since 1975 resulted in Cu/Mo ratios often below one, which may cause molybdenosis in ruminants. The increase in Mo concentrations in crops correlated with the decline in sulfur deposition. Concentrations of Cu and Fe declined in NPK-fertilized wheat as compared to unfertilized or manure-treated wheat. Very low concentrations of Se and Co and low concentrations of Fe and Cu require attention to counteract risks for deficiencies. The main characteristic of the study is that there are few significant changes over time between different fertilizer treatments, but throughout there are low concentrations of most trace elements in all treatments. In general, good agreement between concentrations in wheat from the long-term fertility experiments and the national monitoring program indicate that values are representative.     

美国金融危机的影响与扩大内需

随着全球经济一体化的不断深入,此次美国金融危机给世界各国带来了广泛的影响．对于外贸依存度超过60％的中国经济来说,在微观和宏观上受到了较大的冲击,随着我国融入世界经济的程度不断加深,由投资和出口驱动的经济增长模式,使我国经济运行的风险越来越大．因此,扩大国内消费需求,促进经济增长由主要依靠投资、出口拉动向依靠消费、投资、出口协调拉动的转变,将是我国经济增长的努力方向．参5．     

感潮河流环境需水量预测及敏感性分析--以深圳河为例

以深圳河为研究区域,应用～维非恒定水质模型计算了感潮河流的环境需水量,并针对污染负荷、补水水质、潮汐和污水厂尾水处置等因素对环境需水量的影响进行敏感性分析．结果表明,随着污染负荷和补水本底污染物浓度的增加,环境需水量分别成近似线性和指数函数增加;大、小潮时深圳河的环境需水量差别不大,但涨、落潮的影响却不能忽略;将污水厂尾水输送到流域外排放或将尾水资源化后作为河道补水可以大大减少环境需水量因此,掌握环境需水量的变化规律,对于感潮河流水环境综合治理中截污、补水、污水厂尾水处置等方案的决策具有重要的指导意义．     

中国化肥资源供需矛盾及调控策略

鉴于中国化肥供需形势不清给产业调控带来不确定性影响,论文分析了化肥资源供需矛盾,并提出了相关调控策略。结果表明,中国化肥供需总量已经接近平衡,氮磷钾化肥的自给率分别达到100%、95%和29%。少部分产品存在缺口,其中氯化钾的自给率为23%,是当前我国惟一紧缺的化肥产品。随着化肥生产向资源产地集中,中国化肥供需时空不平衡有扩大的趋势。部分时间段的供需不平衡异常尖锐,其中10月份至来年3月份全国化肥供应过剩超过900×10⁴t,而部分月份却极端不足,例如7月份两广、东北等地的尿素缺口达200×10⁴t左右,10月份华北地区的磷酸二铵缺口达到100×10⁴t左右,而5、7、8三个月中两广地区的钾肥缺口也超过100×10⁴t。建议国家加强储备工作,储备化肥消费量的15%,其中10%储备在淡季,以减少过剩的压力,而5%储备在旺季,以应对市场供不应求。     

WATER USE DATA – WHO NEEDS IT?1

ABSTRACT: This paper addresses problems in the design of a water use data base and valuation of water use data. An examination of the economic efficiency and distributional aspects of selected water management problems indicates that there are benefits to be obtained from water use information and, thus, there is a potential value to water use data. Water use information is viewed as being produced by combining water use data with other data in a modeling context suggested by theory relevant to the problem at hand, and a well designed water use data base will facilitate this synthesis. Data “needs” in the production of water use information via economic modeling are described to illustrate the relationship between theory and data. Some of the desirable characteristics of a water use data base and inadequacies of the existing water use data “base” are described. The fugitive nature of the water use data resource and a lack of understanding of both the information “production function” and the role of water use information in decisionmaking complicates the water use data valuation problem.     

IMPACTS OF WATER QUALITY IMPROVEMENT ON SITE VISITATION: A PROBABILISTIC MODELING APPROACH1

ABSTRACT: The influence of perceptions of water quality on the likelihood of recreating at a particular recreation site is investigated using a logit model. The model is estimated for St. Albans Bay, Vermont. A hypothetical improvement in water quality was shown to greatly increase the probability of at least one visit to the bay during a season. This implies that many recreationists who do not use the bay at present will do so if water quality improves. A demand model for predicting site visitation must, therefore, include current nonusers in the sample. Failure to do so would result in misleading predictions about future demand for the bay.