Date palm (Phoenix dactylifera L.) leaves as biomonitors of atmospheric metal pollution in arid and semi-arid environments

The leaves of date palms were evaluated as a possible biomonitor of heavy metal contamination in Ma’an city, Jordan. Concentrations of (Fe), (Pb), (Zn), (Cu), (Ni), and (Cr) were determined in washed and unwashed leaves and soil samples collected from different sites with different degrees of metal contamination (urban, suburban, industrial, highway and rural sites); separate leaves were taken from outside the city to be used as a control sample. Samples collected from industrial sites were found to have high concentrations of all metals except those of Cu, Ni and Pb, which were found at high levels in the highway site samples which is associated with the road traffic. The difference between unwashed and washed samples showed that metal pollutants exist as contaminants, particularly Pb, Zn and Ni, which varied in concentration, depending on the source of the metal.     

The effect of mercury on trees and their mycorrhizal fungi

The Oak Ridge Reservation, established in 1942, was the designated site for the construction of the atomic bomb. During a 20-year period from 1944 to 1963 radioactive and toxic chemical pollutants, especially mercury compounds were released into the surrounding waterways. Tree diversity and mycorrhizal presence and abundance were analyzed in the mercury-contaminated floodplains of East Fork Poplar Creek Oak Ridge (EFPC) (Tennessee). A subsequent greenhouse study was conducted to assess the phytotoxic effects of different mercuric solutions on Platanus occidentalis (American Sycamore), inoculated with soils from EFPC. Total soil mercury in the field had no effect on tree diversity. Organic species of mercury proved to be more toxic than inorganic species of mercury and soil inoculants from EFPC had no protective effects against Hg toxicity in our greenhouse study. Comparison of the effects of mercury contamination in our field and greenhouse studies was difficult due to uncontrolled factors.     

植物作为反硝化碳源

研究得到一种新型的筛选反硝化碳源的方法:可以通过比较材料浸出液的C/N值,筛选出有效的反硝化碳源;对芦苇秸秆、梧桐黄叶、梧桐绿叶、橘树叶、玉米秸秆和玉米芯6种材料浸出液的C/N值进行了研究,其中当以叶片作为反硝化固相碳源时,应该选取新鲜叶片作为研究对象。橘树叶和玉米芯均属于良好的反硝化碳源。以驯化后的河泥作为反硝化污泥,可以利用橘树叶或者玉米芯作为反硝化固相碳源,进行持续脱氮除磷反应,其中橘树叶脱氮效果强于玉米芯,而玉米芯除磷能力强于橘树叶。扫描电镜实验表明,橘树叶和玉米芯均适合作为生物膜载体。     

Elemental levels in tree-bark and epiphytic-lichen transplants at a mixed environment in mainland Portugal, and comparisons with an in situ lichen

Samples of Platanus hybrida Brot. bark and Flavoparmelia caperata (L.) Hale thalli, from a clean area in northern Portugal (Bai?o), were transplanted into an exposure location at the south-western Atlantic coast, impacted by urban-industrial emissions (Sines), for a 10-month long experiment. Bark pieces were confined into nylon bags (2-mm mesh), and lichen thalli kept with their bark substrate (Pinus pinaster (Ait.) Sol.). Every two months, a double set of transplants (one for bark, one for lichens) was brought back into the laboratory, together with native samples of Evernia prunastri (L.) Ach. Following suitable cleansing and preparation procedures, field samples were put through INAA for elemental assessment. The results indicate that, regardless of signal magnitude, (1) concentrations in bark and lichen transplants are significantly correlated with atmospheric deposition for an appreciable number of elements; (2) there are a number of significant correlations between transplanted and native samples, and again between the latter and the deposition; and (3) the elements with biological patterns that follow the deposition in either transplanted or native samples (Co, V) are the very ones whose bioaccumulation seems to benefit from an alternation of wet-dry periods, which fits the precipitation record of the test site during the exposure term.     

Mercury distribution around the Spolana chlor-alkali plant (central Bohemia, Czech Republic) after a catastrophic flood, as revealed by bioindicators

The current mercury concentrations in moss Hypnum cupressiforme, in forest floor humus and in oak and pine bark were determined in a 10-km radius around a chlor-alkali plant affected by a flood in 2002. Similar distribution patterns of Hg had accumulated in four bio-indicators, irrespective of different Hg concentrations in the analysed biological matrices. No accumulation of extremely Hg-contaminated materials was found in the flooded parts. The bio-indicators, used alone or in combination, can be recommended for effective and reliable determination of Hg contamination levels around Hg sources.     

Bioreclamation of coalmine overburden dumps—with special empasis on micronutrients and heavy metals accumulation in tree species

Major environmental impacts of opencast mining are degradation of landscape and aesthetics of the area by creating huge overburden dumps and deep voids at the mining sites. These overburden dumps are characterised by high rock fragment contents, low moisture retention capacity, higher bulk density, low nutrients, lower pH and elevated metal concentrations. Overburden dumps are reclaimed by tree species for stabilising as well as pollution control and overall improvement of the visual aesthetics. A field study was carried out in the old reclaimed coal mine overburden dumps at KD Heslong project, Central Coalfields, India to study the physico-chemical changes in the reclaimed overburden dumps and determines the magnitude of trace elements accumulation in the planted tree species. Total, bioavailable and acid extractable trace metals concentration in minesoils of overburden dump and topsoil in the mining areas was compared with undisturbed soil. The study showed that tree plantation improves the moisture contents, bulk density, pH and overall nutrient contents of minesoils. The study revealed that lower pH in the minesoils increases the bioavailabity of metals but concentration were found within toxic limits. However, ratio between total and bioavailable metals was found lower in overburden dumps than topsoil due to low pH and lack of organic matter. Out of six tree species studied, Bambusa shows highest accumulation of Fe and Cr. Bioaccumulation coefficient for Cr and Zn was found 74 times in Bambusa and 83 times in Dalbergia sissoo. The results of the study underscore the need for close monitoring of trace elements in reclaimed overburden dumps. Tree species like Dalbergia sissoo, Eucalyptus, Cassia seamea, Acaccia mangium and Peltaphorum were found to be the best species for bioreclamation of overburden dumps.     

Accumulation and distribution of90Sr and137Cs in birch in the zone affected by liquid discharge from the Beloyarskaya Nuclear Power Plant

The data are presented that concern the accumulation and distribution of artificial radionuclides (⁹⁰Sr and¹³⁷Cs) in the aboveground organs of birch growing in the vicinity of the Beloyarskaya Nuclear Power Plant (NPP) in the permanently inundated part of the Ol'khovka swamp, on its banks periodically flooded with water, and in watershed areas not influenced by the swamp (control). Concentrations of both radionuclides in birch trees from the swamp and its banks were several times as high as in trees from the watershed. The distribution of⁹⁰Sr in birch trunk proved to be acropetal. Trees growing on the inundated part of the swamp and on dry land significantly differed in the distribution of¹³⁷Cs. The factors controlling the distribution and accumulation of both radionuclides in birch trees growing in these areas are discussed.     

Tree and stand growth of mature Norway spruce and European beech under long-term ozone fumigation

In a 50- to 70-year-old mixed stand of Norway spruce (Picea abies (L.) Karst.) and European beech (Fagus sylvatica L.) in Germany, tree cohorts have been exposed to double ambient ozone (2×O₃) from 2000 through 2007 and can be compared with trees in the same stand under the ambient ozone regime (1×O₃). Annual diameter growth, allocation pattern, stem form, and stem volume were quantified at the individual tree and stand level. Ozone fumigation induced a shift in the resource allocation into height growth at the expense of diameter growth. This change in allometry leads to rather cone-shaped stem forms and reduced stem stability in the case of spruce, and even neiloidal stem shapes in the case of beech. Neglect of such ozone-induced changes in stem shape may lead to a flawed estimation of volume growth. On the stand level, 2×O₃ caused, on average, a decrease of 10.2 m³ ha⁻¹ yr⁻¹ in European beech.     

Congener-specific egg contribution of polychlorinated biphenyls to nestlings in two passerine species

Quantifying polychlorinated biphenyl (PCB) residues in nestlings of avian species is a common method for assessing trophic transfer and risk at PCB-contaminated sites. The proportion of nestling PCB mass due to maternal transfer is often accounted for by subtracting total PCB mass in eggs from nestlings. However, variation in physicochemical properties and metabolism among congeners may lead to differences between egg contribution based on total PCBs and dioxin-like congeners. We examined congener-specific variation in contribution of PCBs from eggs to nestlings in tree swallows and European starlings. Egg contribution of total PCB mass was 14.3 and 16.2%, respectively, whereas contribution based on dioxin-like congeners was 14.8 and 13.6%, respectively. These data suggest that using total PCB mass in eggs to adjust estimates of PCB accumulation in nestlings may not reflect patterns for dioxin-like congeners, potentially over or under-estimating the risk of toxicity of PCBs.     

Soil acidity reconstruction based on tree ring information of a dominant species Abies fabri in the subalpine forest ecosystems in southwest China

To assess the suitability of dendrochemistry as an indicator of soil acidification, soil chemistry and tree ring information of Abies fabri were measured at two distinct sites (severe acid deposition site-Emei Mountain and clean site-Gongga Mountain) of the subalpine forest ecosystems of western Sichuan, southwest China. The actual soil acidity (pH) was significantly correlated with some of the recent xylem cation (Ca, Mg, Mn, Al, Sr and Ba) concentrations and their molar ratios. Xylem Ca/Mg and Ca/Mn of A. fabri were ultimately selected to reconstruct the historical changes of soil pH in Emei Mountain and Gongga Mountain, respectively. The validity of those rebuild was also verified to a certain extent. We conclude that xylem cation molar ratios of A. fabri were superior to the single cation concentrations in soil acidity rebuild at the study sites due to normalizing for concentration fluctuations.