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681.
为了研究湿地不同退水时间条件下土壤种质资源与地表植被关系的特征,在三个不同的水位条件下,通过幼苗萌发法对野鸭湖湿地近十年来退水湿地面积中土壤种子资源的分布格局进行了研究,同时,对该区域的地表植被在不同退水时间条件下进行了春、夏、秋三次统计。结果表明,土壤中的种子与地表植被在不同的退水时间条件下,差异显著。文章同时还分析了在不同退水时间条件下,土壤种质资源与地表植被产生差异的原因,为今后利用土壤种子资源在湿地恢复和湿地保护过程中的应用提供理论参考。 相似文献
682.
为研究土地利用方式对川芎镉累积及与人体健康的关系,以彭州川芎种植区的菜-药、稻-药(翻耕)、稻-药(免耕)和旱地种植方式下土壤和川芎为研究对象,采用统计分析法和靶标危害系数法(THQ)研究了川芎地上部分和地下根茎镉累积的特征及其对人体的健康风险贡献,结果表明:四种土地利用方式下,川芎种植土壤中Cd含量平均为0.73mg/kg,超过国家二类土壤标准(GB 15618—1995);川芎植株中镉的含量由高到低依次为菜-药免耕翻耕旱地方式,均超过《川芎地理标志保护产品》标准。菜-药种植中土壤镉含量显著高于其他三种方式,在该方式下,川芎植株中地上部分镉含量是根茎的1.67倍,超过《地理标志保护产品》标准9.46倍,超过《食品污染限量标准》1.62倍,根茎中镉含量超过《绿色行标》0.11倍。本研究中,川芎地上部分与种植土壤在镉含量上呈显著线性相关,而川芎根茎与土壤在镉含量上相关性不明显;川芎地上部分对人体镉的健康风险贡献(THQ)值平均为63.18%,是根茎(11.50%)的5.49倍。 相似文献
683.
684.
应用AFS-9530型双道原子荧光光谱法研究土壤样品中砷和汞的联合测定技术,将土壤样品置于(1+1)王水的微波消解体系中进行消解,加入1m L 5%的重铬酸钾溶液保护汞,加入5m L(5%硫脲+5%抗坏血酸)混合液将五价砷还原为三价,以硼氢化钾为还原剂在5%盐酸介质中测定砷和汞,最低检出限为砷0.55μg/L,汞0.30μg/L,回收率砷在93.5%—105.8%之间,汞在85.5%—104.9%之间,满足准确度要求。 相似文献
685.
Soil organic carbon decomposition and carbon pools in temperate and sub-tropical forests in China 总被引:2,自引:0,他引:2
Yang L Pan J Shao Y Chen JM Ju WM Shi X Yuan S 《Journal of environmental management》2007,85(3):690-695
Decomposition of soil organic carbon (SOC) is a critical component of the global carbon cycle, and accurate estimates of SOC decomposition are important for forest carbon modeling and ultimately for decision making relative to carbon sequestration and mitigation of global climate change. We determined the major pools of SOC in four sites representing major forest types in China: temperate forests at Changbai Mountain (CBM) and Qilian Mountain (QLM), and sub-tropical forests at Yujiang (YJ) and Liping (LP) counties. A 90-day laboratory incubation was conducted to measure CO(2) evolution from forest soils from each site, and data from the incubation study were fitted to a three-pool first-order model that separated mineralizable soil organic carbon into active (C(a)), slow (C(s)) and resistant (C(r)) carbon pools. Results indicate that: (1) the rate of SOC decomposition in the sub-tropical zone was faster than that in the temperature zone, (2) The C(a) pool comprised approximately 1-3% of SOC with an average mean residence time (MRT) of 219 days. The C(s) pool comprised approximately 25-65% with an average MRT of 78 yr. The C(r) pool accounted for approximately 35-80% of SOC, (3) The YJ site in the sub-tropical zone had the greatest C(a) pool and the lowest MRT, while the QLM in the temperature zone had the greatest MRT for both the C(a) and C(s) pools. The results suggest a higher capacity for long-term C sequestration as SOC in temperature forests than in sub-tropical forests. 相似文献
686.
The integrated terrestrial ecosystem C-budget model (InTEC) developed by Chen and co-workers has been used successfully to predict carbon dynamics of forests in Canada. It was tested here for forest soil organic carbon (SOC) density of China's northern temperate zone and southern subtropical zone. The results show that the simulated SOC density is highly correlated and in broad agreement with observations in Liping and in Changbaishan, representing the southern subtropical zone and the northern temperate zone in China, respectively. SOC density ranged from 2.2 to 11.2 kg/m(2) in Liping and from 3.4 to 14.8 kg/m(2) in Changbaishan. The correlation coefficients (r(2)) are 0.63 (N=16) and 0.76 (N=14) between the simulated and measured data in Liping and Changbaishan, respectively. The SOC densities under different vegetation types in Liping decrease in the order of mixed forest, broadleaf forest, Chinese fir, couch grass, and Chinese redpine, and in Changbaishan in the order of mixed forest, silver fir, larch forest, and birch forest. 相似文献
687.
Soil and water conservation (SWC) contests among farmer groups were organized in five rural villages in the Bolivian mountain
valleys. The contests were aimed at quickly achieving widespread sustainable results. This article analyzes the effectiveness
of these contests as an extension tool. Mixed results were obtained. In three villages, participation rates in the SWC activities
introduced in the contests were still high even 2 years after project withdrawal. These were all villages where a solid foundation
for sustainable development had been laid before the contests were held. Two years later, most families were still involved
in maintenance of the SWC practices introduced in the contests, and many farmers had started to experiment with different
soil management practices. However, replications of these SWC practices were not widespread, Conservation Leaders did not
continue with their training activities, and the quality of maintenance of the practices was often not satisfactory. In order
to become a more effective extension tool and achieve widespread impact, SWC contests must receive continued support by a
catalyst agency. Moreover, other SWC contests should also be organized in which practices are not predefined. Given that SWC
contests are a low-budget extension tool, local municipalities could become more actively involved. 相似文献
688.
The magnitude of the environmental and social consequences of soil erosion and land degradation in semiarid areas of the Mediterranean
region has long been recognized and studied. This paper investigates the interrelationship between land use/cover (LULC) changes
and land degradation using remotely sensed and ancillary data for southeastern Spain. The area of study, the Xaló River catchment
situated in the north of the Alicante Province, has been subjected to a number of LULC changes during the second half of the
20th century such as agricultural abandonment, forest fires, and tourist development. Aerial photographs dating back to 1956
were used for the delineation of historic LULC types; Landsat ETM+ data were used for the analysis and mapping of current
conditions. Two important indicators of land degradation, namely, susceptibility to surface runoff and soil erosion, were
estimated for the two dates using easily parametrizable models. The comparison of 1956 to 2000 conditions shows an overall
“recuperating” trend over the catchment and increased susceptibility to soil erosion only in 3% of the catchment area. The
results also identify potential degradation hot-spots where mitigation measures should be taken to prevent further degradation.
The readily implemented methodology, based on modest data requirements demonstrated by this study, is a useful tool for catchment
to regional scale land use change and land degradation studies and strategic planning for environmental management. 相似文献
689.
Papadopoulos A Prochaska C Papadopoulos F Gantidis N Metaxa E 《Environmental management》2007,40(4):719-726
The objective of this study was to determine the levels of major phytotoxic metals―including cadmium (Cd), copper (Cu), nickel
(Ni), and zinc (Zn)―in agricultural soils of Western Macedonia, Greece. We also wanted to determine the possible relationships
among elements and between soil properties and elemental concentrations. Surface soil samples, n = 570, were collected and
analyzed. The results of the elemental analysis showed that the mean metal concentrations were consistent with reported typical
concentrations found in Greek agricultural soils in the cases of Zn and Cu. Cd exhibited lower and Ni higher mean concentrations
than the typical levels reported in the literature. Metal concentrations in the majority of the examined samples (>69%) were
found to be higher than the respective critical plant-deficiency levels. However, only 0.4% and 0.2% of the analyzed soil
samples, respectively, exhibited Cd and Ni concentrations higher than the levels that cause plant toxicity, as referenced
by other investigators. These results suggest that the soils studied can be considered as unpolluted with respect to the examined
food-chain metal contaminants. However, the levels of the metal concentrations in some of the soil samples, and the low correlation
of the metals with soil properties, suggest an anthropogenic rather that lithogenic origin. 相似文献
690.
Environmental and health problems associated with the use of digested sewage sludge hinder its application and encourage the introduction of additional treatments such as composting and thermal drying. The aim of this paper is to assess the possibility of using three different types of sewage sludge (digested, composted and thermally dried) to improve soil fertility and enhance the transformation of an unproductive shrub land into a Mediterranean dehesa for grazing purposes and also to reduce wildfire risk. In total, 10t ha(-1) of dry matter of three types of sewage sludge were spread on the soil surface of 4x5m field plots, and then seeded with a mixture of grasses. Effects on soil fertility and plant growth were monitored over 2 years. The results show that all three types of sludge application had a significant effect on vegetation cover, herbaceous biomass (2767.7+/-716.1 and 1735.0+/-299.7kgha(-1) for digested sludge amended and control plots, respectively) and tree growth (0.41+/-0.108cmyear(-1) on amended trees, 14.6% more than control trees). This study proposes the use of multi-criteria analysis to identify the most suitable fertilization alternatives and to assist in the decision-making process of sludge recycling. Because of the high degree of uncertainty and conflicting objectives associated with these decisions, multi-criteria evaluation tools make a valuable contribution to decision-making processes concerning sewage sludge applications. According to multi-criteria results, the composted sludge alternative is the most suitable. This is because all the objectives are achieved: an improvement in the properties and functions of the soil with a positive vegetation response as well as minimal economic cost and risk of toxicity. 相似文献