Relationship between heavy metal concentrations of herbaceous plants and soils at four Pb-Zn mining sites in Yunnan, China

This paper studied the relationship between heavy metal concentrations of herbaceous plants and soils at four Pb-Zn mining sites in Yunnan, China. 50 herbaceous plant samples of 9 plant species from 4 families and 50 soil samples were collected and then ana1yzed for the tota1 concentrations of Pb, Cd, and Zn. The results showed that the average concentrations of Pb, Cd, and Zn in soil samples were 3772.83, 168.81, and 5385.65 mg/kg, respectively. The average concentrations of Pb, Cd, and Zn were 395.68, 28.14, and 1664.20 mg/kg in the shoots, and 924.12, 57.25, and 1778.75 mg/kg in the roots, respectively. Heterospecific plants at the same site and conspecific plants at various sites had different average levels of Pb, Cd, and Zn, both in the shoots and the roots. Enrichment coefficients of Pb, Cd, and Zn were greater than 1 in 2, 3, and 9 herbaceous plant samples, respectively. Translocation factors of Pb, Cd, and Zn were greater than 1 in 10, 17, and 25 herbaceous plant samples, respectively. In all 50 samples, the concentrations of Pb, Cd, and Zn between the shoots and the roots, the shoots, and the soils, and the roots and the soils had significant positive relationships.     

3 forest simulation model

The 3 forest simulation model is a process model of tree growth, carbon and nitrogen dynamics in a single-species, even-aged forest stand. It is based on the model. Major changes include the computation of sun angle and radiation as a function of latitude and day of the year, the closed-form integration of canopy production as a function of day and hour, the introduction of tree number, height, and diameter as separate state variables, and different growth strategies, mortalities, and resulting self-thinning as function of crowding competition.The tree/soil system is described by a set of nonlinear ordinary differential equations for the state variables: tree number, base diameter, tree height, wood biomass, nitrogen in wood, leaf mass, fine root mass, fruit biomass, assimilate, carbon and nitrogen in litter, carbon and nitrogen in soil organic matter, and plant-available nitrogen. The model includes explicit formulations of all relevant ecophysiological processes such as: computation of radiation as a function of seasonal time, daytime and cloudiness, light attenuation in the canopy, and canopy photosynthesis as function of latitude, seasonal time, and daytime, respiration of all parts, assimilate allocation, increment formation, nitrogen fixation, mineralization, humification and leaching, forest management (thinning, felling, litter removal, fertilization etc.), temperature effects on respiration and decomposition, and environmental effects (pollution damage to photosynthesis, leaves, and fine roots). Only ecophysiological parameters which can be either directly measured or estimated with reasonable certainty are used. 3 is a generic process model which requires species- and site-specific parametrization. It can be applied to deciduous and coniferous forests under tropical, as well as temperate or boreal conditions.The paper presents a full documentation of the mathematical model as well as representative simulation results for spruce and acacia.     

treedyn3 forest simulation model

The treedyn3 forest simulation model is a process model of tree growth, carbon and nitrogen dynamics in a single-species, even-aged forest stand. It is based on the treedyn model. Major changes include the computation of sun angle and radiation as a function of latitude and day of the year, the closed-form integration of canopy production as a function of day and hour, the introduction of tree number, height, and diameter as separate state variables, and different growth strategies, mortalities, and resulting self-thinning as function of crowding competition.The tree/soil system is described by a set of nonlinear ordinary differential equations for the state variables: tree number, base diameter, tree height, wood biomass, nitrogen in wood, leaf mass, fine root mass, fruit biomass, assimilate, carbon and nitrogen in litter, carbon and nitrogen in soil organic matter, and plant-available nitrogen. The model includes explicit formulations of all relevant ecophysiological processes such as: computation of radiation as a function of seasonal time, daytime and cloudiness, light attenuation in the canopy, and canopy photosynthesis as function of latitude, seasonal time, and daytime, respiration of all parts, assimilate allocation, increment formation, nitrogen fixation, mineralization, humification and leaching, forest management (thinning, felling, litter removal, fertilization etc.), temperature effects on respiration and decomposition, and environmental effects (pollution damage to photosynthesis, leaves, and fine roots). Only ecophysiological parameters which can be either directly measured or estimated with reasonable certainty are used. treedyn3 is a generic process model which requires species- and site-specific parametrization. It can be applied to deciduous and coniferous forests under tropical, as well as temperate or boreal conditions.The paper presents a full documentation of the mathematical model as well as representative simulation results for spruce and acacia.     

Global Patterns of Mammalian Diversity, Endemism, and Endangerment

To assess the conservation status of the world's land mammals, we compiled data on the number of total species, endemic species, recently extinct species, and currently endangered species for 155 countries. Total species richness was significantly correlated with territorial land area, whereas number of endemic species was only weakly correlated with both area and total number of species. The large amount of variation left unexplained by species-area regressions reflects the influence of other factors, such as latitude, topographic and habitat heterogeneity, and historical biogeography, on species richness and especially on patterns of endemism. Countries of particular conservation concern, because they have rich mammalian faunas containing many endemic species, are the large islands of Australia, Madagascar, Indonesia, and the Philippines, as well as continental Mexico. Patterns of recent extinctions and the current endangered status of species were difficult to interpret, largely because of inadequate and inconsistent data. The majority of officially listed endangered species are large, well known, and popular mammals, such as primates, ungulates, and carnivores, whereas the majority of species known to have gone recently extinct and likely to be currently threatened are small and inconspicuous, such as rodents and bats. Our work not only illustrates the role of ecological, evolutionary, and biogeographic processes in the origin and maintenance of land mammal diversity, it also presents the information at the level of biogeographic regions and political units where management and policy must be applied in order to slow the loss of this diversity.     

Geochemical baselines of heavy metals in the sediments of two large freshwater lakes in China: implications for contamination character and history

The aim of this study was to estimate the geochemical baseline concentrations of various heavy metals in the surface sediments of two large freshwater lakes in Taihu and Dianchi, China, and to assess the character and history of heavy metal contamination around the two lakes. Heavy metal concentrations in the sediments were obtained by field surveys and were supplemented with published data. The statistical methods of cumulative frequency and normalization were employed to obtain the baselines. The respective baseline concentrations for As, Sb, Hg, Co, Cr, Cu, Ni, Pb and Zn were 9.92, 1.67, 0.14, 22.62, 100.56, 31.63, 31.97, 33.05 and 97.01?mg/kg, respectively, in Taihu, and 24.60, 4.29, 0.25, 36.78, 135.68, 90.05, 50.76, 73.56 and 208.76?mg/kg, respectively, in Dianchi. The baseline concentrations of these heavy metals in Lake Taihu were equivalent to the pre-industrial concentrations determined from lakes in Sweden and Europe. Conversely, those in Lake Dianchi were much higher than the pre-industrial values. Li, Fe, Sc, Ti, V and Al were found to be the suitable reference elements for normalization, and one of these elements could be used to predict the baseline concentrations of heavy metals except Hg. Most of the heavy metals had one inflexion, and only Cu and Pb in Taihu, Sb, Pb and Zn in Dianchi, were found to have two inflexions in the cumulative curves, suggesting remarkable anthropogenic inputs of Cu and Pb in Taihu, Sb, Pb and Zn in Dianchi, which are generally consistent with the respective industrial structure around Taihu and Dianchi.     

Nanosensors and nanobiosensors in food and agriculture

The food and agriculture sector controls the economic growth of a developing country. The food industries have practices of growing crops, raising livestock and sea foods, food processing and packaging, regulating production and distribution with quality and safety. The process control and monitoring quality are crucial steps. Here we review nanosensors and nanobiosensors as alternative of classical quantification methods. Nanoscale dimensions of metal nanoparticles, metal nanoclusters, metal oxide nanoparticles, metal and carbon quantum dots, graphene, carbon nanotubes, and nanocomposites expand the sensitivity by signal amplification and integrate several novel transduction principles such as enhanced electrochemical, optical, Raman, enhanced catalytic activity, and superparamagnetic properties into the nanosensors. The electrochemical nanosensors, optical nanosensors, electronic nose and electronic tongue, nanobarcode technology, and wireless nanosensors have revolutionized the sensing in food and agriculture sectors with multiplex and real-time sensing capabilities. Despite previous success stories of the remunerative health sector, the approaches are transferred subsequently to food and agriculture sector; with potential application in detection of food contaminants such as preservatives, antibiotics, heavy metal ions, toxins, microbial load, and pathogens along with the rapid monitoring of temperature, traceability, humidity, gas, and aroma of the food stuff.     

农田土壤重金属污染状况及修复技术研究

重金属污染因具有毒性、易通过食物链在植物,动物和人体内累积,对生态环境和人体健康构成严重威胁。随着工业快速发展、农药及化肥的广泛使用,农田土壤重金属污染越来越严重,研究农田土壤重金属污染现状及修复技术对农产品安全具有重要意义。综合国内外农田土壤重金属污染状况,农田土壤重金属污染主要来源于固体废弃物堆放及处置、工业废物大气沉降、污水农灌和农用物质的不合理施用。该文综述了国内外有关农田重金属污染土壤修复技术（物理修复、化学修复、生物修复、农业生态和联合修复）的研究进展,并针对各种修复方法,阐述了其原理、修复条件、应用实例及其优缺点,重点论述了植物修复的机理和应用,提出了草本与木本联合修复可有效提高农田土壤重金属复合污染的修复效率,为农田土壤土壤重金属复合污染修复提出了新的途径。最后在对已有研究分析的基础上,提出了联合修复技术（如生物联合技术、物理化学联合技术和物理化学-生物联合技术）可以在一定程度上克服使用单一修复手段存在的缺点,可提高复合污染的修复效率、降低修复成本,未来应深入探索联合修复技术间的相互作用机理,以期为农田土壤重金属综合治理与污染修复提供科学依据。     

生态城市建设与城市超循环体系的构建

生态城市的设计、建设和评价,应从人、社会、自然3个层次和城市的结构、功能、协调和目标4个方面来进行定位,最终达到完善结构、提升功能、增进协调、城市优美和谐的目标。城市超循环体系是生态城市社会结构的重要组成部分,城市超循环体系的具有企业、产业、城市、区域4个基本层次,其循环体系、模式、功能和目标均各不相同。生态城市建设与城市超循环体系构建具有在理念上的一致性、结构和功能上的嵌套性、目标和发展机制上的同一性,在更深层次上表现为城市或国家整体中不同民族、不同宗教、多元文化的生态意识在生态理念方面的协调性。     

Influence of lead on growth and nutrient accumulation in canola (Brassica napus L.) cultivars

Canola (Brassica napus L.) is commonly used as a hyper-accumulator for phytoextraction of heavy metals from soil and water. Like many other heavy metals, lead (Pb) contaminates soil, water and air and thus it is a great problem. This study was conducted to investigate toxic effects of Pb on growth and nutrient uptake in four canola cultivars. Each of four cultivars of canola (Con-II, Con-III, Legend and Shiralee) was subjected to four levels of Pb (0, 30, 60 and 90 mg Pb kg(-1) of soil) from lead chloride [PbCl2]. Due to Pb toxicity, plant growth was adversely affected and relatively a severe reduction in root biomass (45.7%) was recorded. The Pb accumulation increased both in shoot and root, the highest being in root. The uptake of different nutrients, i.e., N, P, K, Ca, Mg, Zn, Cu and Mn was reduced (38.4, 32.8, 33.1, 49.6, 7.78, 52.0, 42.6 and 45.9%, respectively) in the shoots and that of N, Fe, Zn, and Cu in the roots (48.5, 33.2, 24.3 and 44.8%, respectively) of all canola cultivars. The root K, P, Zn and Mn and shoot P, Mg and Fe contents were less affected, the concentration of Pb, Ca and Mg in roots of all cultivars. Among canola cultivars Con-II and Con-III performed better than Legend and Shiralee in terms of growth (26.03%) and nutrient accumulation. Overall, plant growth and nutrient accumulation in the canola cultivars was hampered due to the presence of Pb.     

江苏省夏季浮萍种类及其生长水环境调查

对江苏省多个县（市）分布有浮萍的工业区、生活区、农田水体进行调查与采样,观测各地浮萍种类及其生长水体的富营养化状况,探讨水体pH值,铵态氮、硝态氮、总氮、总磷含量与浮萍分布的关系。调查结果表明,浮萍适宜生长在静止的水体中,流动的河流中较为少见;此外,浮萍适宜生长在农田和生活区水体中,工业区附近样本数较少。江苏省夏季浮萍的主要品种为紫萍（Spirodelapolyrrhiza）、青萍（Lemmaminor）、芜萍（Wolffiaarrhiza）和少根紫萍（Spirodelaoligorrhiza）,调查期间未发现稀脉浮萍（Lemmaperpusilla）与品藻（Lemmatrisulca）。紫萍和青萍在所调查的每个采样点均有分布,其生长水体的pH值变化范围（4．5～7．5）较大。浮萍生长水环境的氮、磷养分浓度范围很广,铵态氮、硝态氮、总氮、总磷质量浓度范围分别为0～42、0．2—2．0、0．2～45和0．02～13mg·L-1,尚未发现浮萍分布与水体氮、磷含量之间的必然联系。工业区附近水体中常见紫萍与青萍以共生形式存在,偶尔还伴有芜萍。在利用浮萍去除水中氮、磷营养物质时,应优先考虑利用各地当季优势浮萍品种及不同品种浮萍的共生复合系统,保障浮萍的最大生长量以及对水体氮、磷的最大去除率。     

资源性供给紧约束条件下的消费理论研究述评

通过对国内外关于资源性供给紧约束条件下的消费理论研究的文献回顾,认为在资源环境问题日益严峻的现代社会,深入分析和探寻人与自然和谐共处的居民消费行为,客观上要求我国必须从伦理学、社会学、生态学和法学等多学科领域进行探讨和研究,而不能仅局限于经济学学科研究领域。加快构建生态文明型消费模式,不仅是目前消费理论创新研究的重要方向,而且也是我国贯彻落实科学发展观,实现人口消费与社会、经济、资源和环境全面协调可持续发展的必然选择。     

长期不同施肥条件下红壤小麦和玉米季CO2、N2O排放特征

基于中国农业科学院红壤实验站红壤旱地小麦-玉米轮作长期定位试验,采用静态箱/气相色谱法,研究红壤旱地连续施肥16 a后,不同施肥条件下小麦季和玉米季土壤CO2和N2O的排放特征。结果表明,CO2和N2O排放具有明显的季节性,施肥对土壤CO2和N2O排放有明显影响,且有机肥的施用显著促进了土壤CO2和N2O排放。不施肥对照（CK）、氮磷配施（NP）、氮钾配施（NK）、氮磷钾配施（NPK）和有机无机肥配施（NPKM）处理小麦季和玉米季土壤CO2累积排放量分别为5 904、8 062、4 298、9 235、14 098和4 708、7 530、5 435、7 089、15 472 kg.hm-2,土壤N2O累积排放量分别为0.34、0.63、0.44、0.62、1.00和0.25、0.39、0.35、0.52、1.73 kg.hm-2,小麦休闲期土壤CO2和N2 O累积排放量平均占小麦生长季的63.52%和28.43%,玉米休闲季平均占玉米生长季的49.98%和32.72%,说明休闲期土壤CO2和N2O累积排放量不容忽视。除玉米季NP、NK、NPK处理外,其他各处理小麦季和玉米季土壤CO2排放通量与5 cm深处土壤温度显著相关;而土壤N2O排放通量与土壤温度间均未表现出显著相关性;除NPKM处理外,其他各处理土壤CO2或N2O排放通量与土壤水分间相关性均未达显著水平。     

Toxicology of arsenic in fish and aquatic systems

Arsenic (As) is found in waters such as seawater, warm springs, groundwater, rivers, and lakes. In aquatic environments, As occurs as a mixture of arsenate and arsenite, with arsenate usually predominating. The unrestricted application of As pesticides, industrial activities, and mining operations has led to the global occurrence of soluble As above permissible levels of 0.010 mg/L. Continuous exposure of freshwater organisms including fish to low concentrations of As results in bioaccumulation, notably in liver and kidney. As a consequence As induces hyperglycemia, depletion of enzymatic activities, various acute and chronic toxicity, and immune system dysfunction. Here we review arsenic chemistry, the occurrence of arsenic in aquatic system, the transformation and metabolism of arsenic; arsenic bioaccumulation and bioconcentration; behavioral changes; and acute and other effects such as biochemical, immunotoxic, and cytogenotoxic effects on fish.     

Metal contamination of surface soils of industrial city Sialkot,Pakistan: a multivariate and GIS approach

In this study concentrations of selected metals viz., Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Na, Ni, Pb and Zn in surface soils of Sialkot city known worldwide for tanneries and pharmaceutical industries were measured to assess the status of urban soil pollution and to identify sources of contamination. Hierarchical cluster analysis (HACA) indicated concentrations of Mg and Ca related to parent rock material, Cd, Co, and Pb with traffic related activities, Cr, Cu, Ni and Zn either associated with automobiles activities or industrial pollution and Fe, K and Na related with anthropogenic activities or lithogenous materials. Correlation analyses and principal component analysis based on factor analysis confirmed the results of HACA. Spatial distribution maps exhibited relatively higher concentrations of Cd, Co, Cu, Ni, Pb, Cr and Zn along traffic routes in the city and streams. The results highlighted concentration of Cd, Ni, Cr, Zn, and Pb measured in urban soil exceeded the permissible limit of surface soils and advocated an imperative need for detailed baseline investigations of spatial distribution of heavy metals and other contaminants for the formulation of geochemical database that should be made available to stakeholder involved in monitoring, assessment and conservation of soil contamination for future planning and management of the Sialkot city.     

铜、锌污染对水稻土中油菜（Brassica chinensis L.）生长的影响及累积效应研究

通过盆栽试验,系统研究了Cu、Zn重金属污染对油菜（Brassica chinensis L.）生长、SOD保护酶活性、脯氨酸、可溶性糖及Cu、Zn在油菜体内吸收富集的影响。结果表明：Cu、Zn污染对油菜生物量和生理生化指标（SOD保护酶活性、脯氨酸和可溶性糖）均有影响。随着Cu、Zn质量分数的升高,植株干物重和SOD保护酶活性表现为先增后降;当Cu质量分数达到1 000 mg？kg-1时,油菜干物重和SOD酶活性分别比对照下降36.79%、66.67%;当Zn质量分数达到3 000 mg？kg-1时,油菜干物重和SOD酶活性分别比对照下降55.21%、82.05%。Cu污染下,油菜叶片脯氨酸质量分数逐渐下降,总可溶性糖质量分数表现为先增后降;Zn污染下,脯氨酸和总可溶性糖质量分数均表现为先增后降。Cu、Zn污染使油菜幼苗叶片及根中的Cu、Zn质量分数明显增加,根部的积累尤其明显。当Cu处理为1 000 mg？kg-1时,油菜茎叶和根中质量分数分别为57.6、424.162 mg？kg-1;当Zn处理为1 000 mg？kg-1时,油菜茎叶和根中质量分数分别为240、608.54 mg？kg-1。与Zn相比,Cu主要积累在油菜的根部,向茎叶迁移累积的量很少,并且随着添加质量分数的增加,茎叶吸收Cu的量变化不大。总之,重金属Zn相对于Cu更容易积累于油菜的地上部分,从而更易进入食物链,它们在油菜体内富集都对其生理生化和营养产生了明显毒害作用。     

Chemical elements in the aragonitic and calcitic microstructural groups of shell of the oysterCrassostrea virginica: A proton probe study

We report the results of a study with proton-induced X-ray emissions (PIXE) of the distribution and concentration of 15 chemical elements (Na to Sr in periodic chart) in four microstructural and two mineralogical regions of shell of rapidly growing adult oysters [Crassostrea virginica (Gmelin)]. Hatchery-raised oysters were grown in Broadkill Estuary, Delaware, USA, for 16 wk in summer 1978. Their valve edges were filed as a marker, and the oysters were replaced in the estuary, where they grew rapidly. Shell deposited after marking had a normal microstructure and mineralogy after a narrow zone of disturbance. After 17 d oysters were sacrificed, and different mineralogical and microstructural regions of valves of three oysters, and parts of valves of two oysters, were analyzed for the elements Na to Sr. Quadrats (2.5 × 0.45 mm) included three calcitic groups (prismatic, foliated, chalky) and one aragonitic (myostracal) microstructural group; four quadrats were on the exterior and five on the interior of right and left valves. Inhalant and exhalant margins of valves and ground right and left valves of one oyster were also analyzed. Elemental chemistry of different regions of shell varied among the three microstructural groups within the single calcitic polymorph, between aragonitic and calcitic regions, and between exhalant and inhalant margins of the valves. Elements were most concentrated in the prismatic region of the right valve. Element concentrations were similar in ground right and left valves, except for higher levels of Si, Fe, and Zn in the right valve (corresponding to their high contents in prismatic shell) and of Cl in the left valve (reflecting high concentration in chalky shell, abundant in this valve). Na, Mg, Cl, Cr, Cu, Zn and Br were more concentrated in prismatic than in foliated shell. Chalky shell contained higher concentrations of Na than did prismatic shell, and high concentrations (but lower than in prismatic shell) of Mg, Cl, Ti, Mn, Fe, Zn and Br. Element concentration in myostracum was approximately the same as, or lower than, in foliated shell, except for Sr, which was higher than that in any other shell group. In the right valve most elements were concentrated in inhalant margins, and on the left valve, in exhalant margins. With increased weathering of the exterior surface of prismatic shell, Mg, Si, and Mn increased in concentration and Na, Al, Cl, Ti, Cr, Fe, Br, and Sr decreased.     

青岛近海生物体内多环芳烃、多氯联苯和有机氯农药的含量和分布特征(Concentrations and Distribution Characteristic of PAHs, PCBs and OCPs in the Marine Organisms of Qingdao Coastal Area)

为初步了解青岛近海生物体内多环芳烃、多氯联苯和有机氯农药的含量和组成特征,于2007年10～11月采集了青岛近海13个站位的鱼、虾和软体类动物,分析了其肌肉中的多环芳烃、多氯联苯和有机氯农药的含量和组成.结果表明,多环芳烃、多氯联苯和有机氯农药更易在鱼类体内富集,其含量远大于软体类和虾类.高氯代联苯和高环芳烃在同系物中的比例在鱼类体内最小,这可能是由鱼类和虾类、软体类不同的生活习性造成的.有机氯农药中,滴滴涕的含量显著高于六六六.     

Ecotypes diversity in autumn olive (Elaeagnus umbellata Thunb): A single plant with multiple micronutrient genes

Elaeagnus umbellata, a member of the Elaeagnaceae family, is native to Pakistan, China, India, Korea, and Japan. It is found commonly at altitudes ranging from 1200 to 2100 m and thrives on eroded and degraded land due to its ability to fix nitrogen. The plant also grows under variable pH (4-8) and drought, and is used locally as fuel wood, fencing, fodder, basket making, and shelterbelts. The fruit of the plant is well known for its essential nutrients and medicinal compounds such as vitamins, minerals, essential fatty acids, carotenoids (lycopene), soluble solids, and sugars. Medicinally, it is widely believed to protect against myocardial infections, pulmonary infections, and various forms of cancers. Ten ecotypes from variable microclimatic conditions were investigated for their morphological, molecular and biochemical diversity improvement and commercialization purposes. Comparisons and disabilities indicated significant variability in terms of morphological (plant height, number of branches, thorn size and number, leaf area, fruit size, 100 fruit weight, and yield), molecular (SDS-PAGE), and micro- and macronutrient (vitamin C, Fe, mg, P, Na, K, essential oils, and sugar) bases among the ecotypes. This variability will be helpful in developing commercial varieties of the plant utilizing the conventional techniques of selection and hybridization for economic activities. The plant has ample quantities of multiple micronutrients, thus indicating their expression through a powerful promoter at one place (fruit mesocarp). Efforts to identify and isolate the micronutrient genes (vitamin A, C, E, and Fe), the deficiency of which causes malnutrition and disabilities within the population of developing countries. Micronutrient genes have also been initiated for their characterization and future transformation into staple food crops for stable bio-fortification.     

Partitioning of cadmium,copper, lead and zinc amongst above-ground parts of seed and grain crops grown in selected locations in the USA

The distribution of Cd, Cu, Pb and Zn in above-ground parts of corn, small grains and pulse crops was investigated. Sampled parts included grain or seed, leaves, stems, silk and husks of corn-ears, rachilla and chaff of small grains and pods of bean plants. The distribution of these elements was variable and reflected, primarily, their relative mobility between plant parts including transfer into the grain. Generally, Zn and Cu were preferentially transferred into the seed or grain, while Cd and Pb were selectively excluded from these organs. For example, the distribution pattern in ears of corn was: for Cd, husks > silk > grain; for Zn, silk > grain > husks. The selective transfer of Zn and Cu into seed or grain, in contrast to the restricted movement of Cd and Pb into these organs, may be the result of selective absorption of Zn and Cu over Cd and Pb by vascular transfer cells within the plant's reproductive tissues. The effect of soil type on Cd, Cu, Pb and Zn levels in cereal grain or pulse seed was small compared to the differences found in the concentrations of these elements between different plant organs. Thus, grain and seed crops serve as natural barriers to the movement of the potentially toxic heavy metals, Cd and Pb, into the animal/human food chain, minimising their transfer from soils while conserving Zn and Cu levels in edible portions of these crops.Soil Scientist, USDA, Soil Conservation Service, Retired.     

产业转型的生态系统工程

在产业结构调整、优化过程中 ,必须从观念、管理和技术 3个层次上 ,加快传统产业改造、转型、升级及新兴产业发展 ,大力推进产业生态转型和建立生态产业。结合大量案例 ,论述了发展生态产业的原则和策略 ,主要有 :以市场为导向 ,生态与整体最优 ,竞争、共生、自生、再生相结合 ,减量化、再利用、资源化的循环经济 3原则 ,发挥区域优势 ,加强结构与功能的弹性和自我调节 ,硬件、软件和心件的耦合 ,创造更多就业机会