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排序方式: 共有123条查询结果,搜索用时 187 毫秒
1.
Effects of atmospheric mercury pollution on terrestrial ecosystem in Chongqing, China 总被引:1,自引:0,他引:1
1 IntroductionMercury(Hg)asaglobalpollutanthascausedconcernworldwidesincetheendof 1980s.Itisemittedtotheatmospherefrombothanthropogenicandnaturalsources.Importantsourceoftheformeristhedischargefrom productionanduseofHgaswellasthecombustionoffossilfuels(Nri… 相似文献
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Bio-accumulation and distribution of heavy metals in black mustard (Brassica nigra Koch) 总被引:1,自引:0,他引:1
There has been carried out a comparative research, which to allow us to determine the quantities and the depots of accumulation of Pb, Cu, Zn and Cd in the vegetative and reproductive organs of Brassica nigra, as well as to identify the possibilities of growing on soils, contaminated by heavy metals and its use for the purposes of the phytoremeditation. Experiments have been implemented in field and in controlled conditions. B. nigra is tolerant towards the heavy metals and could be successfully grown in regions of low and moderate level of contamination with heavy metals, without lowering of the quantity and quality of the manufactured production. The depots for accumulation, in case it is being grown on contaminated soils without Cu follows the order: roots > fruit's shells > stems > seeds. In the case of its growing on non-contaminated soils the order roots > fruit's shells > seeds > stems preserves for the Pb, while the order for the Cu, Zn, and Cd is: fruit's shells > seeds > stems > roots. A relation is determined between the quantity of the total and the mobile forms of metals on one hand, and their total quantity in the plants in the field, as well as, in the pot experiments, on the other. A drastic exclusion is made by the Pb in the pot experiments, as its basic part is blocked in compounds that are hardly soluble. Its absorption by the plants is almost entirely blocked, which is almost a degree lower than that obtained in the field experiments and is commensurable with the results obtained in non-contaminated soils. Clarification of the reasons causing this effect requires additional examinations and above all, fractionation of the soil and determination of the forms and depots of localization of Pb compounds. 相似文献
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The horizontal distribution and quantitative characteristics of macrozoobenthos were studied in small lakes of the Darwin Nature Reserve (southern Vologda oblast). The aggregation index varied in the open areas of acid lakes, which indicated that communities of small acid water bodies were unstable. The aggregation was the lowest in the open area of a neutral lake. In acid lakes, the number and biomass of macroinvertebrates were the highest near the coasts. In the neutral lake, conversely, these values were maximum in open areas and low near the coast due to a strong pressure of predatory invertebrates and fish. An aggregating effect of invertebrate predators was observed near the coasts of lakes of different types. 相似文献
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Pitois A Ivanov PI Abrahamsen LG Bryan ND Taylor RJ Sims HE 《Journal of environmental monitoring : JEM》2008,10(3):315-324
The distribution of 152Eu between magnesium hydroxide bulk, colloids and solution has been assessed under alkaline conditions, such as those in nuclear fuel storage ponds. The colloidal phase has been characterised by two complementary methods: coupled ultrafiltration-ICP-AES and scanning electron microscopy. The quantity and the size distribution of the colloidal phase is strongly ionic strength-dependent. A decrease of the quantity of colloids, in particular the larger size ranges, has been observed with increasing ionic strength. Small colloids (1 kDa-10 kDa fraction) are predominant at all ionic strengths. The morphology of colloids, observed by field-emission gun scanning electron microscopy, appears to change from hexagonal prismatic (characteristic to the mineral) to spherical (energetically more favourable) as size decreases. The distribution of 152Eu between the solid and liquid/colloidal phases has been investigated at carbonate concentrations ranging from 0 to 10(-2) M by coupled ultrafiltration and gamma-spectrometry. Mg(OH)2 bulk appears to be a very strong sorbent for 152Eu, since complete sorption onto the bulk happens for carbonate concentrations as high as 10(-3) M. Scavenging of 152Eu by Mg(OH)2 colloids is negligible in the presence of Mg(OH)2 bulk. The distribution of 152Eu between liquid and colloidal phases has been investigated in the absence of bulk at various carbonate concentrations. A significant uptake of 152Eu by the colloids in solution has been observed, which decreases with increasing carbonate concentration. 152Eu appears to be mainly associated to the smallest colloids (1 kDa-10 kDa fraction). There is a strong correlation between the sorption properties and the surface area of the colloids. 相似文献
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2012年4~10月采用自制沉降颗粒收集装置收集主养草鱼和黄颡鱼池塘生态系统中沉降颗粒物,开展了颗粒物质的垂直沉降量以及沉降颗粒中碳氮磷等营养物质的组成及沉降通量的季节变化特征的研究。结果表明:养殖可以显著提高池塘颗粒物质的垂直沉降量,主养草鱼池塘中颗粒物质垂直沉降量显著高于主养黄颡鱼池塘(p0.01),且两种养殖模式池塘颗粒物质沉降量随着养殖时间推进有显著增加的趋势。主养草鱼的池塘中颗粒物质垂直沉降量在100.39~414.66g/(m2·d)之间变化,平均为224.46g/(m2·d),主养黄颡鱼池塘中沉降颗粒物质垂直沉降量在34.14~272.91g/(m2·d)之间变化,平均为155.18g/(m2·d)。两种养殖模式沉降颗粒的碳氮磷成分在养殖周期内的变化规律不明显但具有相似的变化趋势,主养黄颡鱼池塘沉降颗粒中TN、TC、TOC和TON的含量均比同时期主养草鱼高,且均随着养殖时间的推进,沉降颗粒中碳氮磷的总量呈增加趋势。两种养殖模式池塘沉降颗粒中的C/N比值与沉积物中的C/N比值较为接近,表明沉降颗粒与沉积物营养物质来源具有一定的相似性,同时养殖系统内养殖对象与其所处环境的相互依存和相互影响对颗粒物质的产生以及沉降具有重要作用。 相似文献