首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 31 毫秒
1.
采集草海流域周边成熟期整株农作物及土壤样品,分析测试其中DDTs和HCHs的含量,对比研究了土壤和作物中DDTs和HCHs污染水平及其在作物中富集能力。结果表明:研究区域土壤中HCHs和DDTs残留检出率均为100%,残留范围分别为0.06~16.66μg·kg^-1和0.08-39.77μg·kg^-1,土壤中HCHs和DDTs的残留量均小于国家土壤环境质量一级标准;三种农作物中DDTs、HCHs及∑(DDTs,HCHs)残留量差异显著,HCHs含量最高的是玉米,DDTs和(DDTs,HCHs)最高的是马铃薯;三种农作物中HCHs和DDTs残留的风险系数均为1.1,属于低度风险,农作物中DDTs、HCHs及∑(DDTs,HCHs)的安全指数IFSc均小于1,DDTs和HCHs残留量对三种农作物安全影响的风险是可以接受的。  相似文献   

2.
Crop performance and yield are the results of genotypic expression as modulated by continuous interaction with the environment. Among environmental factors, water is globally one of the most limiting for crop production. Water resources in the world are steadily diminishing and in many areas, including Poland, more frequent periods of drought are being observed. The aim of the study was to compare the yields and gas exchange parameters of Festulolium hybrid (Festulolium braunii (K. Richt) A. Camus) and alfalfa (Medicago?×?varia T. Martyn) under different levels of soil moisture (well-watered conditions and drought stress) and cultivation method (pure stand and mixture). The study has shown that all the measured parameters were affected by drought stress. Net photosynthetic rate, transpiration rate, stomatal conductance and dry mass yield were significantly lower under drought stress than under well-watered conditions in all treatment types. Alfalfa grown in a pure sowing showed the strongest reaction to stress, while hybrid Festulolium grown in mixture showed the weakest. It was also found that under stress, grass assimilated CO2 and evaporated water much more intensively in mixture cultivation than in pure sowing. Higher water use efficiency (WUE) was observed in alfalfa and Festulolium growing in mixture only in the first year of the study.  相似文献   

3.
当前,肯尼亚和中国在生产足够粮食以保障粮食安全方面都面临着严峻的挑战。尤其是对于肯尼亚而言,因为其2100年预测的人口将达到2018年的1.4倍,且其粮食生产在过去并没有大幅度的改善。而中国近些年粮食生产能力显著提高。本文系统分析了肯尼亚和中国农业资源投入、种植业和畜牧业单产水平的历史变化,以及农业资源投入与产量之间的关系,为肯尼亚粮食危机和消灭贫困提供更多的理论支撑。研究结果表明,在20世纪60年代,肯尼亚耕地、草地和降水等自然资源人均占有量比中国高2~3倍,且人均食物能量和蛋白质供应显著高于中国。当前,肯尼亚人均资源拥有量仍高出中国约30%,但是其人均食品供应和粮食自给率却远低于中国平均水平。这是由于与肯尼亚相比,中国在种植业和畜牧业长期持续的投入,大幅度地增加了种植业和畜牧业能量或蛋白质单产水平。1961-2017年,中国和肯尼亚作物蛋白的平均单产分别增加282%和44%。中国的数据表明,种植业和畜牧业单产水平与肥料、精饲料、机械和农药的投入具有显著正相关性;农牧业生产结构对单产水平的变化影响也很大,如种植业中蔬菜和水果播种面积占比,畜牧业中单胃动物饲养占比等。总的来说,农业资源投入和农业结构对生产力的提高都有很大的影响,这可能是肯尼亚提高农业生产力的潜在选择。  相似文献   

4.
Fungal abundance and diversity in earthworm casts and in uningested soil   总被引:1,自引:0,他引:1  
Earthworm casts and adjacent uningested soil from 30 different locations were compared to determine the abundance and diversity of fungal species. The casts contained larger fungal populations (g-1 dry soil weight) and numbers of fungal species than the soil. Variations in these parameters between casts and soil were statistically significant (P=0.05). Fungal populations and the number of fungal species in casts and soil also varied significantly (P=0.05) between samples from different locations. A total of 27 fungal species were recorded from the casts and soil. Indices of dominance (0.084 casts; 0.14 soil) and general diversity (2.53 casts; 2.02 soil) demonstrated that the casts displayed more diverse fungal flora than the soil. The diversity of fungal species increased in earthworm casts after passing through the earthworm gut.  相似文献   

5.
自 1991年长江上游水土保持重点防治区滑坡、泥石流预警系统运作以来 ,陇南陕南片成功预报和处理滑坡、泥石流险情 10 3处 ,保护人口 11 6 8万 ,避免经济和财产损失 11879 6 5万元 ,取得了良好的社会效益。主要做法及经验是 :依靠各级政府 ,健全预警网络 ;广泛深入宣传 ,增强防灾意识 ;健全管理制度 ,落实岗位职责 ;强化技术培训 ,提高业务技能 ;加强检查指导 ,现场解决问题 ;及时调查险情 ,做好技术服务 ;预防治理结合 ,注重减灾实效。  相似文献   

6.
大棚和露地环境下,分别对番茄植株一次性喷洒推荐剂量的百菌清(CHT)和毒死蜱(CHP),研究喷药后两周内农药在番茄根、茎、叶和果实中分布的持久性及其动态降解规律。实验结果表明,百菌清在大棚番茄中的残留浓度分布呈现为叶片垌果实〉茎〉根;毒死蜱呈现为叶片〉果实垌茎〉根。大棚番茄各部位的最高残留浓度出现时间滞后于喷药时间8~60h;空间浓度分布上表现为大棚中间区域浓度高于两侧,这与棚内的空气对流有关。大棚番茄果实中百菌清和毒死蜱的残留半衰期分别为5.8d和7.2d,明显高于文献报道。  相似文献   

7.
Hydrocarbons (aliphatic and aromatic) and metals (heavy metals and major elements) were measured in both atmospheric deposition and roof runoff in central Paris (France). Atmospheric deposition (wet and dry) was collected from December 2001 to October 2002 and roof runoff was sampled on three buildings with different covering materials, i.e., slate tiles and zinc sheets. This paper gives an overview of the results on the flux and distribution points of view for both atmospheric deposition and roof runoff. Results show that atmospheric fluxes of hydrocarbons and major elements increase during cold seasons, due to residential heating occurrence, while heavy metals, whose major sources have constant emission fluxes, exhibit steady atmospheric loads throughout the year. Moreover, hydrocarbon fingerprints reveal mainly biogenic and pyrolytic origins for aliphatic and aromatic hydrocarbons, respectively. The results about roof runoff contamination suggest that the scavenging processes for hydrocarbons and metals are dependent on rainfall amount rather than on the rain event characteristics (number, intensity, duration), and dry deposition weakly contributes to the pollutant loads in roof runoff. Results also highlight that both metallic and slate roofs do not act as a source of hydrocarbons and major elements—exclusively originating from atmospheric deposition—while they act as a source of some heavy metals. Zinc-covered roofs largely release Zn and Ti, while slate roofs mainly release Pb, Ti and Cu. Whatever the material used for roof covering, roof runoff presents high Ni and V loads due to the vicinity of the chimney stacks of heating boilers.  相似文献   

8.
黑钙土烤烟氮素积累、分配的研究   总被引:3,自引:1,他引:3  
通过对黑钙土上烤烟氮素积累与分配研究,结果表明,从烟株全生育期内氮素含量与积累结果可看出,不施氮肥处理,烤烟氮积累总量为96.97 kghm-2,黑钙土土壤供氮能力强;施氮处理N1(52.5 kghm-2)和N2(67.5 kghm-2)氮积累总量分别为117.94和121.59 kghm-2,烟株氮积累量同施氮量成正比,各部位烟叶氮素含量范围适中,从不同部位烟叶氮积累表明,N1和N2处理上部叶氮积累量分别为42.93 kghm-2和43.90 kghm-2,下部叶、茎花氮积累量相差不大,增加氮肥用量,烟株氮素主要集中在上部烟叶。从烤烟经济效益角度考虑,黑钙土上施氮量应控制在52.5~67.5 kghm-2之间比较适宜。  相似文献   

9.
Mechanisms preventing oxidative burst in cells exposed to high metal concentrations are crucial for cell survival. In this report, sunflower (Helianthus annuus L.) was used as a model species to investigate: (a) how cadmium (Cd) affects plant defense pathways (in particular, those involved in preventing oxidative stress), and (b) whether antioxidative enzymes of plants and of in vitro cell culture (calluses) have similar responses to Cd exposure. For this experiment, plants (grown hydroponically on Long Ashton medium) and calluses (grown on Murashige and Skoog medium) were exposed for three weeks to different Cd concentrations (0, 5, 50, and 500 μ M). Solute and electrolyte leakage increased significantly with the increase in Cd concentration in the external medium and in exposed leaves, and less in exposed calluses. Cadmium exposure also reduced significantly soluble protein contents in both leaves and calluses. The activities of catalase and peroxidase decreased significantly in 50 and 500 μ M-exposed leaves compared with the control, but increased in 5 μ M-exposed calluses, decreasing in the calluses exposed 500 μ M Cd. The decrease in antioxidative enzymes activities is congruent with the decrease in membrane integrity and suggests that calluses develop antioxidant mechanisms that respond better to Cd stress than do leaves. On average, 100% of plants exposed for 21 d to 500 μ M and 95% of plants exposed for 45 d to 50 μ M Cd were dead. After 45 d, only 53% of 50 μ M-exposed calluses had died. These surviving calluses were maintained on 50 μ M for six months. Six-month-old exposed calluses had higher activities of peroxidase and catalase when compared with control calluses, as well as lower membrane degradation. These data show that calluses are more tolerant than plants to Cd exposure, and that antioxidant mechanisms under Cd exposure may differ between the two cell systems and vary with time.  相似文献   

10.
小黑麦氮素吸收利用的基因型差异研究   总被引:1,自引:1,他引:0  
以69个小黑麦品种为材料,研究了同一供N水平下,不同小黑麦品种在分蘖、抽穗和成熟期对N素吸收利用的基因型差异,考查了单株籽粒产量、地上部N积累量、地上部N收获指数、N运转率和N利用效率等指标。结果表明:①在3个时期,不同品种小黑麦对N素的吸收利用均存在着显著的基因型差异,其中地上部N积累量和N利用效率与单株籽粒产量呈极显著正相关(r = 0.84,r = 0.63),是决定小黑麦经济产量的重要因子。②通过聚类分析,在供试的69个小黑麦品种中,具有较高籽粒产量、N素吸收总量和N素利用效率的共4个品种,分别为Clxt75、P1428736、P1429227和P1466703。  相似文献   

11.
12.
云南省各级党政领导重视和支持水土保持 ,积极出台有关法规、政策 ,为搞好水土保持工作提供了保障。治理中坚持高起点要求 ,有力地推动了水保产业化建设。适应市场经济要求 ,大力发展水土保持专业户、重点户 ,调动社会各方面力量参与水土流失治理开发。介绍了具体的做法、成效及今后做好水保工作的思路。  相似文献   

13.
More than 50% of global soil organic carbon stocks are stored below 20 cm of soil depth capable of massively altering global C cycle and climate. However, subsoil C dynamics are largely overlooked implicitly assuming that surface and subsoil C dynamics are similar. Here, we compared the soil C dynamics in surface and subsurface soil layers in response to nitrogen and maize leaf litter additions. Soils, sampled from 0 to 5, 15 to 35, 35 to 55 and 55 to 75 cm depths, were incubated at 25°C after adding litter, nitrogen (NH4NO3) or litter plus nitrogen. Soil respiration (C mineralization) was measured throughout the incubation period. Litter addition significantly increased C mineralization in all the soil layers. However, the soil CO2 release relative to control was more than twofold higher in 15–35 and 35–55 cm soil layers than the surface layer. Nitrogen additions significantly decreased C mineralization in 0–15 cm soil, increased in 35–55 cm and had minimal effects in the 15–35 and 55–75 cm layers. Different soil C dynamics in surface and subsurface soil layers found in our study contradict the general assumption that soil C dynamics may be treated similarly along different soil depths.  相似文献   

14.
干旱区农田灌溉前后土壤水盐时空变异性研究   总被引:5,自引:0,他引:5  
通过田间土壤剖面取样,测定了新疆奇台县干旱区农田灌溉前、灌溉后1 周和3 周土壤水盐的时空变异特征。结果表明: 灌溉前, 剖面各层土壤含水量较低(15.25%~16.70%), 且呈中等(偏弱)变异性; 剖面上部(40 cm 以上)土壤盐分呈强变异性, 而下部为中等(偏强)变异性。灌溉后1 周, 除0~20 cm(弱变异性)外, 其他土层水分及剖面下部盐分变异性未变, 但变异系数均减小, 上部土壤盐分转为中等(偏强)变异性; 剖面平均土壤含水量升高10.51%, 脱盐率达8.94%, 其中, 表层(0~20 cm)土壤水分增加率(118.48%)及脱盐率(20.86%)最大, 底层(100~120 cm)水分增加率(40.54%)及脱盐率(-6.93%)最小。灌溉后3 周与1 周相比, 各层(除80~100 cm 土层)水分及盐分的变异性保持不变, 但水分的变异系数增大, 而盐分的变异系数减小; 剖面平均含水量减少5.20%, 表层(0~20 cm)失水率(36.47%)最大, 80~100 cm 失水率(7.31%)最小; 表层土壤积盐率(4.55%)约为20~40 cm 土层的12 倍; 而40 cm 土层以下仍处于脱盐阶段, 40~80 cm 土壤脱盐率减小, 80~120 cm 土层脱盐率(9.03%)增大。  相似文献   

15.
A novel indole glucosinolate, 1,4-dimethoxyglucobrassicin (1,4-dimethoxyindol-3-ylmethylglucosinolate), was isolated as the desulfo derivative from roots of the P-type of Barbarea vulgaris ssp. arcuata, and its structure was determined by spectroscopy including 2D NMR spectroscopy. 4-Hydroxyglucobrassicin (4-hydroxyindol-3-ylmethylglucosinolate) was isolated as the desulfo derivative from green siliques (fruits) of Arabidopsis thaliana and identified by comparison of its (1)H NMR spectrum with the spectrum of the known desulfoglucosinolate from Brassica napus. The delayed elution of desulfo indole glucosinolates from the DEAE Sephadex column used in sample preparation was examined, and the diode-array UV spectra of desulfo indole glucosinolates were measured, to ensure a reliable determination of 1,4-dimethoxyglucobrassicin and 4-hydroxyglucobrassicin with the existing analysis method based on the HPLC of desulfoglucosinolates. 1,4-Dimethoxyglucobrassicin was not detected in 10 other Arabidopsis, Brassica, and Barbarea species, indicating an evolutionarily recent mutation in the indole glucosinolate biosynthesis in B. vulgaris ssp. arcuata type P.  相似文献   

16.
The aim of this investigation was to compare the liver and aorta changes in rats fed cholesterol-containing diets and the possible improvement when diets would be supplemented with frequently used raw vegetables. The phenolic compounds of three vegetables in methanol-water (1:1) fraction were characterized using electrospray ionization mass spectra (ESI-MS). Results showed that the content of polyphenols, flavonoids, quercetin, flavanols, tannins, and ascorbic acid varied for garlic and white and red onions ranging from 6.68 to 18.08 mg GAE/g DW, 490.4-701.0 μg CE/g DW, 281.2-1100.0 μg, 32.40-41.30 μg CE/g DW, 2.88-3.12 mg CE/g DW, 1.87-2.33 mg AA/g DW, 1388.2-1442.3 μg CGE/g DW, respectively. The radical scavenging capacities (μM TE/g DW) for the same investigated vegetables for ABTS, FRAP, CUPRAC, and DPPH assays ranged from 48.78 to 92.42, 9.41-28.56, 3.06-10.41, and 6.49-23.42, respectively. Good correlations were observed between the phenolic contents and the radical scavenging capacities of the vegetables. The interaction between BSA and quercetin, BSA and garlic and onions extracts was measured by 3-dimensional fluorescence (3D-FL) and Fourier transform infrared (FT-IR) spectroscopy. The highest polyphenol content was found in methanol/water fraction of onions and garlic; therefore, for the investigation of in vitro interactions with BSA only polyphenols of this fraction were used. For in vivo studies, 30 male Wistar rats were divided into 5 groups each of 6 and named Control, Chol, Chol/Garlic, Chol/OnionRed, and Chol/OnionWhite. During 6 weeks, the rats of all 5 groups were fed a basal diet (BD). The rats of the Control group were fed the BD only. The BD of the Chol group was supplemented with 10 g/kg of nonoxidized cholesterol (NOC). Each of the other three groups was supplemented with 10 g/kg of NOC and 500 mg of raw fresh garlic, 500 mg of raw fresh red onion, and 500 mg of raw fresh white onion on 1 kg of body weight for Chol/Garlic, Chol/OnionRed, and Chol/OnionWhite diet groups, respectively. In order to detect the changes in the liver and aorta, a histological procedure was applied, and the liver enzymes were determined and compared. It was found that the main changes vs the Control group were in the liver of rats fed the cholesterol-containing diet without vegetable supplementation. Significantly less histological changes in the liver and lower level of liver enzymes vs those of the Chol group were detected in rats of the Chol/Garlic group (P < 0.05). The interaction between the polyphenol extract of garlic and BSA in vitro showed its strong ability comparable with that of quercetin to quench the intrinsic fluorescence of BSA. In conclusion, all studied vegetables showed protective effects, but raw garlic supplemented with cholesterol-containing diets significantly prevented the aorta and liver damages of rats.  相似文献   

17.
In Austria, farm animals are estimated to produce about 20×106 ton of excrements annually. In order to predict possible changes of the inorganic compositions of the target soils from various organic fertilizers, mean compositions of excrements, composts and sewage sludges have been compiled on a dry weight basis. Although the high amounts of K and P were beneficial, there were some high concentrations of Na in biogas residues and pig manures. Intense additions of Cu, Zn, and Se are reflected in high loads in the respective excrements, and these amounts in some instances exceeded the threshold limits for soil contamination. Selenium addition to arable soils can be regarded as beneficial, however, as Austria is a low Se area. Composts and sewage sludges were higher in Al and lithophilic trace elements than were the excrements. Factor analysis traced phosphates as the main source of Cd. Cr in processed matrices was significantly higher, and abrasion from tools should be considered in future investigations. Other unwanted trace elements, like Ni, Pb, As and Hg, were found at a rather low concentration.  相似文献   

18.
In Kenya, traditional food crops play an important role in food and nutritional security, especially in the dry parts of Kenya. This study set out to document the most important traditional food crops in Kenya and highlight their production levels, production ecologies, as well as their nutritional value. The findings reveal that the relative importance of traditional food crops differs from one area to another and, while some are produced for subsistence use; others, like sweet potatoes, are grown for commercial purposes. Despite their potential contribution to food and nutritional security, production of traditional food crops is far below that of maize (the main staple food in Kenya). The authors recommend rigorous promotion to increase their production and consumption, since traditional food crops are grown in the arid and semi-arid parts of the country where maize does not perform as well.  相似文献   

19.
Summary Use of the N2-fixing grey alder, Alnus incana (L.) Moench, as a short-rotation crop for energy production is currently being explored. To evaluate the need for inoculation of alders, the distribution of infective propagules of Frankia in the soil at potential sites for alder plantations was examined. Uninoculated grey alder seedlings were grown in three types of soil. Frequent nodulation was found in a meadow soil which had been free from actinorhizal plants for nearly 60 years, but the alder seedlings failed to nodulate in peat soil from two different bog sites. One of these bogs had been exploited for peat and the surface layer of the peat had been removed, so that the soil samples were taken from deep layers of the peat. At the other site, an area of cultivated peat, there were no infective propagules of Frankia in plots without alders; the infective Frankia was present in plots only where it had been introduced by inoculated alders. There was no detectable air-borne dispersal of Frankia. Instead, water movement might account for the dispersal of Frankia in peat. Although the apparent absence of Frankia in these peat soils necessitates inoculation of alder seedlings before planting out, this makes it possible to introduce and maintain Frankia strains with selected beneficial characteristics, since there is no competition from an indigenous Frankia flora.  相似文献   

20.
除草剂莠去津和灭草松单用和混用在土壤中的降解   总被引:2,自引:0,他引:2  
The application of a mixture of bentazone (3-isopropyl-1H-2,1,3-benzothiadiazin-4(3H)-one-2,2-dioxide) and atrazine (6-chloro-N2-ethyl-N4-isopropyl-1,3,5-triazine-2,4-diamine) is a practical approach to enhance the herbicidal effect. Laboratory incubation experiments were performed to study the degradation of bentazone and atrazine applied in combination and individually in maize rhizosphere and non-rhizosphere soils. After a lag phase, the degradation of each individual herbicide in the non-autoclaved soil could be adequately described using a first-order kinetic equation. During a 30-d incubation, in the autoclaved rhizosphere soil, bentazone and atrazine did not noticeably degrade, but in the non-autoclaved soil, they rapidly degraded in both non-rhizosphere and rhizosphere soils with half-lives of 19.9 and 20.2 d for bentazone and 29.1 and 25.7 d for atrazine, respectively. The rhizosphere effect significantly enhanced the degradation of atrazine, but had no significant effect on bentazone. These results indicated that biological degradation accounted for the degradation of both herbicides in the soil. When compared with the degradation of the herbicide applied alone, the degradation rates of the herbicides applied in combination in the soils were lower and the lag phase increased. With the addition of a surfactant, Tween-20, a reduced lag phase of degradation was observed for both herbicides applied in combination. The degradation rate of bentazone accelerated, whereas that of atrazine remained nearly unchanged. Thus, when these two herbicides were used simultaneously, their persistence in the soil was generally prolonged, and the environmental contamination potential increased.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号