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磷酸盐对污染土壤中Pb·Cd·Zn的钝化效果 总被引：1，自引：0，他引：1
[目的]研究磷酸盐对重金属Pb、Cd、Zn的钝化作用。[方法]以磷酸盐作为钝化剂,添加量设为50~1 200 g/m~2,考察Pb、Cd、Zn的有效态浓度随着钝化剂添加量的变化。[结果]随着磷酸盐添加量的增大,Pb、Cd、Zn有效态浓度均呈下降趋势,Pb从280 mg/kg下降到123 mg/kg,Zn从14.20 mg/kg下降到7.18 mg/kg,Cd从1.50 mg/kg下降到1.27 mg/kg,最终得到最佳添加量为500 g/m~2,并且30 d后Pb、Cd、Zn有效态浓度达到稳定状态。添加磷酸盐后土壤pH从5.62增加到7.57。[结论]磷酸盐可使土壤中的Pb、Cd、Zn浓度明显降低,达到预期的土壤修复效果。 相似文献
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Plants grown in aquaponics frequently develop iron deficiency, which is generally corrected via supplementation with iron chelates. However, the solid waste excreted by fish contains considerable amounts iron, which are lost in the system by precipitation of insoluble iron oxides. Thus, the present study proposed the use of fulvic acid (FA), a humic substance with metal complexing capacity, to prevent iron precipitation and enhance its bioavailability in the aquaculture wastewater. An aquaponic solution was added with levels of fulvic acid (0, 69, 138, 345, and 690 mg L−1), and analyzed for dissolved iron after incubation and centrifugation. Visual MINTEQ was used to characterize and quantify the effect of fulvic acid levels on iron precipitation, species of possible solid forms, and concentration of dissolved bioavailable iron forms. Dissolved iron concentration increased with the inclusion of fulvic acid in the nutrient solution, and the highest iron concentration (22.4 μM) was obtained by treating the solution with 690 mg L−1 of fulvic acid. Visual MINTEQ simulations demonstrated that, in the absence of fulvic acid, iron precipitated in the form of αFe2O3, and the concentration of available iron increased with the inclusion of FA due to its complexing properties. Solution pH had no effect on iron availability with the absence of fulvic acid; in its presence, the effect of pH was only significant at values below 4.5. This study shows that fulvic acid seems to play an important role in transporting low-soluble iron from fish tanks to plant roots in aquaponic systems. 相似文献
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Sndor Hornok 《Veterinary parasitology》2009,163(4):366-369
Hard ticks (Acari: Ixodidae) were collected from the vegetation at monthly intervals in 2008 on six places of three different biotopes in Hungary. Except for Haemaphysalis concinna and H. punctata, predominance of females was observed in the questing population. From among the species with biphasic activity period, metastriate ticks (Dermacentor spp. and H. inermis) had higher prevalence of host-seeking males in the autumn than in the spring, as opposed to prostriate Ixodes ricinus. In comparison with the permanently mild weather experienced at the beginning of 2007, sharply rising temperatures during consecutive winter days in January and February of 2008 appeared to be more efficient in triggering a 1–2 month earlier spring peak activity of hard ticks, except for I. ricinus. Regarding seasonality, D. marginatus was most numerous in February and March, whereas D. reticulatus in September and October; H. punctata showed peak activity in March–April, H. concinna in May, and H. inermis in November–December. Within these genera such a temporal difference (allochrony) between seasonal peak activities of sympatric species under continental climate is described for the first time. 相似文献
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[目的]对我国巢湖东部水源区及入湖河流无机氮的形态特征及其影响进行研究。[方法]研究巢湖东部水源区及入湖河流溶解性无机氮(DIN)的形态组成和分布特征,并探讨它们对水质的影响。[结果]NH3-N、NO2--N平均浓度在汛期较高,非汛期较低,NO3--N正好相反;双桥河口NH3-N浓度远高于其他各点,污染最为严重。柘皋河口、小柘皋河口DIN主要为生活污水及工业废水污染所致;双桥河口地表径流、船舶污染等对DIN含量贡献较大。[结论]该研究为巢湖富营养化控制和治理提供了基础数据和理论依据。 相似文献
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Tobin L. Peever 《European journal of plant pathology / European Foundation for Plant Pathology》2007,119(1):119-126
Ascochyta/legume interactions are attractive systems for addressing evolutionary questions about the role of host specificity in fungal
speciation because many wild and cultivated cool season food legumes are infected by Ascochyta spp. and most of these fungi have described teleomorphs (Didymella spp.) that can be induced in the laboratory. Recent multilocus phylogenetic analyses of a worldwide sample of Ascochyta fungi causing ascochyta blights of chickpea (Cicer arietinum), faba bean (Vicia faba), lentil (Lens culinaris), and pea (Pisum sativum) have revealed that fungi causing disease on each host formed a monophyletic group. Host inoculations of these fungi demonstrated
that they were host-specific, causing disease only on the host species from which they were isolated. In contrast to the strict
association between monophyletic group and host observed for pathogens of cultivated legumes, Ascochyta fungi causing disease on wild bigflower vetch (Vicia grandiflora) were polyphyletic. Genetic crosses between several pairs of closely related, host-specific, and phylogenetically distinct
Ascochyta fungi were fully sexually compatible. Progeny from these crosses had normal cultural morphology and segregation of molecular
markers indicating a lack of intrinsic, post-zygotic mating barriers between the parental taxa. However, when progeny from
a cross between a faba bean-adapted isolate (A. fabae) and a pea-adapted isolate (A. pisi) were assessed for their pathogenicity to the parental hosts, almost all progeny were non-pathogenic to either faba bean
or pea. These results suggest that although these fungi have retained the ability to mate and produce progeny with normal
saprophytic fitness, progeny are severely compromised in parasitic fitness. The host specificity of these fungi, coupled with
the inability of hybrid progeny to colonize and reproduce on a host, may constitute strong extrinsic, pre-zygotic and post-zygotic
mating barriers in these fungi and promote the genetic isolation and speciation of host-specific taxa. A phylogeny of the
host plants is also being developed, and with more extensive sampling of pathogens and hosts from sympatric populations in
the centre of origin, the hypothesis of cospeciation of pathogens and hosts will be tested. The objectives of this review
are: (1) to summarize recent phylogenetic, host specificity and speciation studies of Ascochyta fungi, and (2) to suggest how current and future research using these pathosystems may lead to a better understanding of
the role of host specificity in the speciation of plant-pathogenic fungi and the cospeciation of pathogens and their hosts. 相似文献
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Shinjiro Sato Eduardo G. Neves Dawit Solomon Biqing Liang Johannes Lehmann 《Journal of Soils and Sediments》2009,9(3):194-205
Background, aim, and scope Changes in bioavailability of phosphorus (P) during pedogenesis and ecosystem development have been shown for geogenic calcium
phosphate (Ca-P). However, very little is known about long-term changes of biogenic Ca-P in soil.
Materials and methods Long-term transformation characteristics of biogenic Ca-P were examined using anthropogenic soils along a chronosequence from
centennial to millennial time scales.
Results and discussion Phosphorus fractionation of Anthrosols resulted in overall consistency with the Walker and Syers model of geogenic Ca-P transformation
during pedogenesis. The biogenic Ca-P (e.g., animal and fish bones) disappeared to 3% of total P within the first ca. 2,000 years
of soil development. This change concurred with increases in P adsorbed on metal-oxides surfaces, organic P, and occluded
P at different pedogenic time. Phosphorus K-edge X-ray absorption near-edge structure (XANES) spectroscopy revealed that the
crystalline and therefore thermodynamically most stable biogenic Ca-P was transformed into more soluble forms of Ca-P over
time. While crystalline hydroxyapatite (34% of total P) dominated Ca-P species after about 600–1,000 years, β-tricalcium phosphate increased to 16% of total P after 900–1,100 years, after which both Ca-P species disappeared. Iron-associated
P was observable concurrently with Ca-P disappearance. Soluble P and organic P determined by XANES maintained relatively constant
(58–65%) across the time scale studied.
Conclusions Disappearance of crystalline biogenic Ca-P on a time scale of a few thousand years appears to be ten times faster than that
of geogenic Ca-P. 相似文献
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选取包头市区4个有代表性公园分别采集表层土样,测定重金属含量。结果显示,重金属富集非常明显。Cu、Zn、Pb和Cd的含量分别是内蒙古土壤均值的2.9、6.2、2.1和4.9倍;全国土壤几何平均值的1.2、4.4、1.9和2.4倍。相对于北京公园土壤,包头公园土壤Pb含量略低,Zn、Cu和Cd含量分别是北京公园土壤均值的3.7、1.2和1.5倍。重金属富集程度依次为Zn〉Cu〉Pb〉Cd。采用Tessier的五步连续提取法,测定了土壤中重金属各形态含量水平。结果表明,重金属大都以有机结合态和残留态形式存在,有效态含量低,生物可利用性小。Zn的可交换态和碳酸盐结合态占总量的11%,具有一定的生物有效性和潜在生态危害性。 相似文献