Heavy metal pollution,phosphatase activity,and mineralization of organic phosphorus in forest soils

Industrial Cu and Zn pollution reduces the decomposition rate, phosphatase activity, and P mineralization rate in the mor horizon of conifer forest surrounding a brass mill in Sweden. There is statistical evidence for Cu being more responsible for this effect than Zn at about equal concentrations. A negative influence on the phosphatase activity is measurable already at a low degree of pollution. A higher pH of the soil may counteract the heavy metal effect to some extent.     

Cycling of nitrogen by surface-casting earthworms in a pasture ecosystem

Production of surface casts and the removal of plant litter from the soil surface by earth-worms had similar seasonal variations, with maximum values in May and minimum values occurring in July and August. Seasonal variations in the total nitrogen (TN) and oxidizable carbon contents of casts were closely related to variations in litter production. The C:N ratio of casts (10.7) was consistently smaller than that of underlying soil material (15.0 and 14.2 for the 0–5 and 18–22 cm depths, respectively), which is probably due to the mineralization of plant-derived organic material during passage through earthworms and utilization of low C:N ratio litter. Seasonal changes in the amounts of inorganic N forms in casts showed a build-up of NH₄⁺N in the cooler winter months (July and August), attaining a maximum of 112 μg.g^?1. with a decrease in autumn (April and May) and early spring (September and October), reaching a minimum of 54 μg.g^?1. The opposite trend existed for seasonal variations in the NO₃^?-N content of the casts. Because only minor fluctuations in the amounts of N forms were obtained for underlying soil material during the casting period, the more dramatic changes observed in the casts could not be explained by soil variations. Seasonal variations in urease enzyme activity, associated with fluctuations in organic matter content, were more important than the effect of temperature on enzyme activity in accounting for seasonal variations in the NH₄⁺-N content of casts. It was calculated that 73% of the TN content of litter removed from the surface by earthworms was accumulated in casts, indicating both the importance of earthworms in incorporating litter N with soil material and the inefficiency of N digestion by earthworms.     

Transport of metal cations through a nutrient-poor forest ecosystem

Metal cations were analyzed in bulk precipitation, soil water, and stream flow in a southeastern U.S. lower Coastal Plain pine flatwoods for 6 yr. Extractable ions in mineral soil and total amounts in herbaceous vegetation were also determined. Concentrations for all ions were higher in soil water than in bulk precipitation, but especially Na⁺ and Mg⁺⁺. There were smaller concentration differences between soil water and stream flow, except for three-fold higher Ca⁺⁺ in stream flow. Base saturation in the mineral soil was less than 10%, with Al dominating cation exchange sites. Of all cations, only K showed a significant relationship between exchangeable amounts in the soil and total amounts in herb layer vegetation. Soils in the watershed-ecosystem are experiencing minimal mineral weathering, although this can be spatially quite variable. We conclude that the chemistry of such soils is susceptible to change over several forest harvest rotations and continued acid deposition.

     

Heavy metal pollution of urban soils

The chemical properties of urban soils (southeastern administrative district, Moscow) affecting the behavior of heavy metals were studied. The current heavy metal pollution level of the soils was assessed. The use of different approaches for the pollution standardization is shown to produce different results. The fractional composition of the metal compounds in the soils and the factors affecting its formation under technogenic pollution were investigated. In the district studied, the distribution of heavy metals by the fractions primarily depended on the chemical properties of the heavy metals themselves; the pollution level; and, to a lesser degree, on the soil properties. Zinc and cadmium were the most mobile metals in the soils studied.     

Plant availability of phosphorus in superphosphate and a phosphate rock as influenced by earthworms

The effect of earthworms on the plant availability of phosphorus (P) in superphosphate and Chatham Rise phosphorite (CRP) was evaluated in a glasshouse experiment using perennial ryegrass over seven harvests. A mixed earthworm population of Lumbricus rubellus (Hoff.) and Allolobophora caliginosa (Savigny) was used. Increases in the yield of ryegrass in the presence of earthworms varied from 2 to 32%, whereas increases in P uptake by ryegrass ranged from 0 to 40% over seven harvests. With superphosphate, the initial increases in both ryegrass yield and P uptake by ryegrass in the presence of earthworms ranged from 20 to 40% at first harvest to less than 10% by the seventh. In marked contrast, earthworms increased the agronomic performance of pelletized CRP by 15 to 30% throughout the trial period. An increase in plant-available soil N concentrations due to earthworm activity probably explains the initial difference in the performance of superphosphate. The increased agronomic effectiveness of CRP appears to result from the incorporation and intimate mixing of the PR with the soil by earthworms. The implications of the results obtained in the present study to the interpretation of glasshouse and field trials evaluating P fertilizers are also discussed.     

Deposition of gold mining tailings in tropical soils: metal pollution and toxicity to earthworms

Journal of Soils and Sediments - This study consists of the evaluation of metals acute toxicity levels taking into consideration a hypothetic scenario of dam breaking and land deposition of two...     

Role of air pollution in forest decline in Eastern North America

Evidence for and against three general mechanisms by which air pollution stress may cause or contribute to forest decline in eastern North America is examined. These mechanisms are (1) soil acidification, cation nutrient depletion, and subsequent Al toxicity, (2) direct and indirect effects of gaseous pollutants on the physiology and growth of forest trees; and (3) excess nitrogen deposition and subsequent soil acidification or physiological injury. Recent studies have revealed reductions in base saturation in some sites (both polluted and pristine), but the consequences of these changes to forest health and nutrition are not resolved. Aluminum toxicity may contribute to forest decline in red spruce (Picearubens L.) in high-elevation sites, but the data are contradictory. In forested landscapes in which regional decline (reduced tree growth and/or dieback) is reported, O₃ is the only gaseous pollutant documented as a contributing factor in the eastern North America. Whereas this secondary pollutant exhibits a regional distribution and occurs at potentially phytotoxic levels, a linkage between O₃ and forest decline is substantive only for loblolly pine (Pinustaeda Sarg.) in the southeast. Studies in high elevations do not support the hypothesis that O₃ or hydrogen peroxide directly affects the growth of red spruce or fraser fir (Abiesfraseri Poir.).However, preliminary data link chronic-level O₃ exposure with indirect effects, principally changes in drought tolerance in low-elevations (e.g., P. taeda) nd winter hardiness in high elevations (e.g., P. rubens).The emerging data on the role of air pollution as an environmental stress indicate that indirect effects (i.e., responses in which pollution alters the plant's ability to compete for limited resources or withstand other environmental stresses) are more important than direct effects (e.g., foliar necrotic lesions). Nitrogen saturation has been offered as an hypothesis for P. rubens decline, but no experimental data exist supporting this hypothesis.     

Microbial activity and community structure of a soil after heavy metal contamination in a model forest ecosystem

We assessed the effects of chronic heavy metal (HM) contamination on soil microbial communities in a newly established forest ecosystem. We hypothesized that HM would affect community function and alter the microbial community structure over time and that the effects are more pronounced in combination with acid rain (AR). These hypotheses were tested in a model forest ecosystem consisting of several tree species (Norway spruce, birch, willow, and poplar) maintained in open top chambers. HMs were added to the topsoil as filter dust from a secondary metal smelter and two types of irrigation water acidity (ambient rain vs. acidified rain) were applied during four vegetation periods. HM contamination strongly impacted the microbial biomass (measured with both fumigation-extraction and quantitative lipid biomarker analyses) and community function (measured as basal respiration and soil hydrolase activities) of the soil microbial communities. The most drastic effect was found in the combined treatment of HM and AR, although soil pH and bioavailable HM contents were comparable to those of treatments with HM alone. Analyses of phospholipid fatty acids (PLFAs) and terminal restriction fragment length polymorphisms (T-RFLPs) of PCR-amplified 16S ribosomal DNA showed that HM treatment affected the structure of bacterial communities during the 4-year experimental period. Very likely, this is due to the still large bioavailable HM contents in the HM contaminated topsoils at the end of the experiment.     

Heavy metal pollution by long range atmospheric transport in natural soils of Southern Norway

Natural surface soils in Southern Norway are strongly contaminated by metals from atmospheric deposition. Except from local pollution with Cu, Ni and to a limited extent Pb around the town of Kristiansand, this large-scale contamination can be ascribed to long-range atmospheric transport from other parts of Europe. Zinc, As, Cu, and Pb are all found in excessive concentrations in the surface layer of natural soils throughout the region, and in particular within a zone of about 20 to 40 km from the coast. In this zone the elements appear at the following concentrations or higher in the A₀ layer (typical levels in other parts of Norway little affected by air pollution in parantheses): Zn, 120(30) mg kg^?1; As, 4(0.5) mg kg^?1; Cd, 2(0.2) mg kg^?1; Pb, 160(15) mg kg^?1. Possible harmful effects to soil biological processes of this contamination cannot be excluded.     

Microbial responses of forest soil to moderate anthropogenic air pollution

There is a need to introduce soil microbiological methods into long term ecological monitoring programs. For this purpose we studied the impact of moderate anthropogenic air pollution in polluted and less polluted area districts, forest site types Calluna (CT), Vaccinium (VT) and Myrtillus (MT) and the amount of organic matter, measured as carbon content on the soil respiration activity and the ATP content. The main sources of local air pollutants (SO₂ and NO_x) in the polluted area district were from the capital' region and an oil refinery. Humus (F/H-layer) and the underlying 0 to 5 cm mineral soil samples were collected from 193 study plots located in the 5300 km² study area. We found that the soil respiration rate in humus layer samples was lower in the polluted area district compared to the less polluted one (16.0 and 19.5 μL CO₂ h^?1g^?1 dw, respectively), but the difference occurred only in the dry, coarse-textured CT forest site type. The mineral soil respiration rate and the mineral soil and humus layer ATP content were not affected, by the air pollution. Most of the variations of the biological variables were explained primarily by the soil carbon content, secondly by the forest site type and thirdly by the area division.     

Carbon sequestration in Norway spruce in south Sweden as influenced by air pollution,water availability,and fertilization

Carbon sequestration in 30 yr old Norway spruce in south Sweden following manipulation of nutrient and water availability is presented. The site has an annual precipitation of 1100 mm and a deposition of about 20 kg N and 25 kg S per ha^?1 yr^?1. The soil type is a poorly developed podzol. Treatment include irrigation; artificial drought; ammonium sulphate addition; nitrogen-free-fertilization and irrigation with liquid fertilizers including a complete set of nutrients. The experiment has a randomized block design with four replicates per treatment. A comprehensive investigation of the above ground C storage on an areal basis was made at the start of the experiment and after 3 yr of treatment. After 3 yr of treatment with simulated N-S deposition using ammonium sulphate (100 kg N, 114 kg S ha^?1 yr^?1), C accumulation rates in the above ground compartments had increased by 37%. Similarly, irrigation caused increased C accumulation rates by 25%, whereas simulated drought during the vegetation period during 2 yr followed by 1 yr of recovery caused a 15% reduction of the C accumulation rates. Irrigation combined with liquid fertilization (100 kg N ha^?1 yr^?1), including all important nutrient elements, led to 65% increase in C accumulation rates compared to the control. The C sequestration of the latter treatment gradually increased and, during yr 5 of treatment, 8.6 Mg C ha^?1 accumulated in stems and branches, compared to 3.6 Mg ha^?1 for the control. It is concluded that there is a strong interaction between N-deposition and C accumulation rates in Norway spruce in south Sweden. The C accumulation rates are also sensitive to water availability. The study indicates a great potential to cultivate Norway spruce in south Sweden as a renewable energy source. A shift in energy source from fossil fuels to renewable energy sources will directly reduce the net emissions of CO₂ to the atmosphere.     

Heavy metal pollution of agricultural soils and sediments in Liaoning Province,China

Heavy metal pollution of soils and sediments in Liaoning Province, Northeast China, was investigated. Fifty seven samples of agricultural soils and 8 samples of sediments were collected in 1996 from paddy or upland fields and irrigation channels, respectively, in Shenyang, Fushun, Liaoyang, Anshan, and Tieling regions, and concentrations of total and 0.1 mol L^-1 HCI-extractable Cd, Cu, Pb, and Zn were analyzed using ICP spectrometry. Seventeen samples of unpolished rice were also collected from selected paddy fields and total concentrations of the four elements were determined.–

Both paddy and upland soils were polluted with Cd: average total concentration was 0.70, 0.57, and 0.53 mg kg^-1 in the western and southern parts of Shenyang, and Anshan, respectively, and significantly higher than the background level of 0.32 mg kg^-1. Cd concentrations of four samples exceeded even 1 mg kg^-1, which corresponds to the critical level of Cd contamination in China. About 65% of the total Cd was extracted with 0.1 mol L^-1 HCI, suggesting that Cd was relatively mobile compared with other metals. The level of Cd pollution was, however, lower than that previously reported and serious polIution was not observed for Cu, Pb, and Zn. Accordingly, Cd concentration in upland rice was within the range of the unpolluted level in this study. Nevertheless, Cd concentration in a sediment of irrigation channels in the western part of Shenyang exceeded 16 mg kg^-1, indicating the possibility of further contamination of agricultural soils. In conclusion, soils and sediments were still polluted with Cd in the southern part of Shenyang, Anshan, and especially in the western part of Shenyang, and further countermeasures are urgently required to ensure safe food production in these regions.     

Modelling subalpine forest dynamics as influenced by a changing environment

FORSUM, a forest succession model of the JABOWA/FORET type was applied to simulate possible impacts of environmental changes on subalpine forest ecosystems and compared with the model FORECE (Kienast, 1987). The model used is based on approaches of Botkin et al. (1972), Shugart (1984) and Kienast (1987) and has been improved by implementing soil water movement calculations based on a user-defined one-dimensional nonhomogeneous soil profile. The influence of a possible climatic change on subalpine ecosystems was investigated for three different sites in the Grisons (Switzerland). The scenarios used are based on climate change predictions of General Circulation Models. A temperature increase of 3? C would cause important changes in species composition. Deciduous trees would invade today's subalpine belt causing a displacement of various conifers in this zone. Some coniferous species might eventually migrate into today's alpine zone which would consequently become afforested. Comparing the vegetation changes as predicted by the model FORSUM and FORECE we found that the models generate the main general patterns. However under global warming and a concurrent precipitation decrease total biomass production seems to be overestimated by FORECE. Information about seed dispersal rates (horizontal and vertical), seed availability and soil formation processes should be implemented in these models to improve the reliability of the predictions.     

小麦根际Cr(Ⅵ)的还原

Reduction of Cr(Ⅵ) to Cr(Ⅲ) was studied in a fresh wheat rhizosphere soil (kuroboku, high humic Andosol) pretreated with a basal fertilizer consisting of (NH₄)₂SO₄, P₂O₅ and KH₂PO₄ and with K₂Cr₂O₇ by using a rhizobox system. The rhizosphere exerted a positive effect on Cr(Ⅵ) reduction. Part of the reason was the decrease of pH in the rhizosphere due to application of (NH₄)₂SO₄, implying that application of physiologically acid fertilizers would reduce Cr(Ⅵ) toxicity to plants.     

Organic matter dynamics in a temperate forest as influenced by soil frost

In the future, climate models predict an increase in global surface temperature and during winter a changing of precipitation from less snowfall to more raining. Without protective snow cover, freezing can be more intensive and can enter noticeably deeper into the soil with effects on C cycling and soil organic matter (SOM) dynamics. We removed the natural snow cover in a Norway spruce forest in the Fichtelgebirge Mts. during winter from late December 2005 until middle of February 2006 on three replicate plots. Hence, we induced soil frost to 15 cm depth (at a depth of 5 cm below surface up to –5°C) from January to April 2006, while the snow‐covered control plots never reached temperatures < 0°C. Quantity and quality of SOM was followed by total organic C and biomarker analysis. While soil frost did not influence total organic‐C and lignin concentrations, the decomposition of vanillyl monomers (Ac/Ad)_V and the microbial‐sugar concentrations decreased at the end of the frost period, these results confirm reduced SOM mineralization under frost. Soil microbial biomass was not affected by the frost event or recovered more quickly than the accumulation of microbial residues such as microbial sugars directly after the experiment. However, in the subsequent autumn, soil microbial biomass was significantly higher at the snow‐removal (SR) treatments compared to the control despite lower CO₂ respiration. In addition, the water‐stress indicator (PLFA [cy17:0 + cy19:0] / [16:1ω7c + 18:1ω7c]) increased. These results suggest that soil microbial respiration and therefore the activity was not closely related to soil microbial biomass but more strongly controlled by substrate availability and quality. The PLFA pattern indicates that fungi are more susceptible to soil frost than bacteria.     

Heavy metal pollution of soil from industrial and municipal wastes in Chittagong,Bangladesh

Heavy metal pollution was assessed in soils collected from 0–15, 15–30 and 30–45-cm depths of three industrial (FMC, PMC and CMC), and two municipal (BSD and MLF) waste disposal sites around Chittagong city in 2008. Soils were analysed for pH, organic carbon, total nitrogen, available P, exchangeable Ca, Mg, K and Na, and total Cd, Pb, Cu, Mn and Zn. The pH, organic C, total N, available P, total Cd, Pb, Cu and Mn, and contamination indices for Cd and Pb varied significantly among sites. Mean Cd, Pb, Cu, Mn and Zn were in the range 0.5–1.9, 54–86, 25–50, 261–624 and 204–330 mg kg^?1, respectively. Contamination indinces for Cd, Pb, Zn and Cu were estimated by comparison with respective threshold values. Contamination indices showed that the sites MLF and FMC had low Cu contamination. Other sites were not contaminated with thisheavy metal. All sites except PMC were highly contaminated with Cd, FMC was moderately contaminated and the others had low Pb contamination. FMC was highly contaminated, but the others were moderately contaminated with Zn. The integrated contamination index revealed that PMC had low contamination and the other sites were highly contaminated with heavy metals.     

东莞石马河沿岸土壤重金属污染及生态毒性研究

为研究河水-地下水交互作用对河流沿岸土壤环境质量的影响,以东莞石马河沿岸土壤为研究对象,采集沿岸距离河道不等的6个土壤剖面共31个土样,测定土壤重金属(As、Cd、Cr、Cu、Fe、Mn、Ni、Pb和Zn)含量和土壤水提取液对发光菌的抑制率。结果表明,Cd、Cu、Ni和Zn的含量分别为2.80~11.2mg kg-1、9.70~298mg kg-1、11.4~69.7mg kg-1和40.4~465mg kg-1;Cd的地累积系数为6.06,达到极度污染水平;土壤重金属污染的地累积系数排序为CdZnCuNiCrMnAsPbFe;重金属含量差异与土壤有机质(SOM)含量和土壤微粒组分(63μm)有关,Cr、Cu、Ni、Zn、Mn和Cr、Ni与SOM含量和微粒组分分别呈显著正相关(p0.05或p0.01);土壤剖面毒性单位(∑TU)评价结果为剖面S3S2SbS1S4Sa,其中剖面S3的值最大,为5.51,属于中毒;土壤水提取液对发光菌的抑制率为2.45%~16.5%,为无毒或低毒。     

Effects of ventilation and air temperature on pollution levels in underground car parks

The relationship between the levels of CO and airborne Pb was evaluated against conditions of traffic flow, ambient air temperature and the ventilation rates in 3 underground car parks. During the study period significant variations were noted in the levels of the pollutants in each of the car parks which frequently exceeded the proposed Malaysian Air Quality Standard of 0.7 μg m^?3Pb and 9 μg L^?1 (8 hr average) CO for indoor environs. High correlation coefficient values were obtained between the levels of CO and traffic flow and Pb and traffic flow. High traffic flow also increased the mean air temperature inside the car parks. Reductions in the ventilation rates in the car parks caused an almost two-fold increase in the level of CO and vice versa. A simple mathematical model depicting the CO concentrations in relation to other parameters was formulated.     

Invasion of a deciduous forest by earthworms: Changes in soil chemistry, microflora, microarthropods and vegetation

Ecosystems of northern North America existed without earthworm fauna until European settlers arrived and introduced European species. The current extent of invasion by some of these species, Lumbricus terrestris L., Octolasion tyrtaeum Savigny and Dendrobaena octaedra Savigny, into an aspen forest in the Canadian Rocky Mountains and the effects of the invasion on soil chemistry, microflora, soil microarthropods and vegetation were investigated. Densities of earthworm species, soil structure, plant coverage and abundance were determined along three transects starting at the edge of the forest. At locations with L. terrestris, litter was incorporated into the soil, and where O. tyrtaeum was present, organic layers were mixed with mineral soil layers. Organic layers disappeared almost entirely when both species occurred together. Carbon and nitrogen concentrations were reduced in organic layers in the presence of L. terrestris and O. tyrtaeum. Microbial biomass and basal respiration were reduced when L. terrestris and O. tyrtaeum were present, presumably due to resource competition and habitat destruction. Microarthropod densities and the number of microarthropod species were strongly reduced in the presence of O. tyrtaeum (−75% and −22%, respectively), probably through mechanical disturbances, increasing compactness of the soil and resource competition. The coverage of some plant species was correlated with earthworm abundance, but the coverage of others was not. Despite harsh climatic conditions, the invasion of boreal forest ecosystems by mineral soil dwelling earthworm species is proceeding and strongly impacts soil structure, soil chemistry, microorganisms, soil microarthropods and vegetation.     

Soil acidification by atmospheric pollution and forest growth

In recent years concern has been expressed about the danger of harmful pollution deposits which affect areas at great distances from the emission sources. The investigation was so designed that a possible reaction in growth resulting from a supposed acidification could be observed as far as possible. A poorer growth development was observed in regions, which are suspected of being more susceptible to acidification than those regions which are presumed to be less susceptible in this respect. We have found no good reason for attributing the reduction in growth to any cause other than acidification.