Extensive Soil Survey Research Articles

Soil water storage capacity and soil nutrients drive tree ring growth of six European tree species across a steep environmental gradient

Tree growth depends on tree-intrinsic attributes, synecological interactions, atmospheric conditions and soil properties. While the influence of tree factors and climate are analysed in detail in many studies, the effect of soil properties is less investigated and compensatory soil effects are often not quantified. In this study, we use a comprehensive dataset of 1659 tree increment cores from six common Central European tree species (Abies alba, Fagus sylvatica, Larix decidua, Picea abies, Pinus sylvestris, Quercus spp.) sampled at 1562 locations across large environmental gradients in the Eastern Alps. Soil data was available from an extensive soil survey including soil pits, laboratory analysis and the application of pedotransfer-functions. Up to three main tree species per site were sampled and the tree ring widths were dendrochronologically measured and synchronized. Topographic information from a high-resolution Digital Terrain Model, high-resolution climate data and biometric measures were available at each site. To determine the influence of soil water storage capacity and soil nutrient status, we used generalized additive models to expand standard models of well-known drivers of tree growth, including age, climatic water balance and temperature. For the time span of 38 years from 1981 until 2018, we found species-specific impacts of soil properties on tree ring growth. Specifically, soil water storage acted as a buffer to overcome drought periods, in particular for deep rooting tree species like Quercus spp. and Abies alba. In addition, we found species-specific growth reactions to soil nutrient status for nutrient-demanding species likes Fagus sylvatica but no effects for less demanding tree species like Pinus sylvestris. Our results show the magnitude of the effects of soil properties in relation to other growth factors on radial growth of six Central European tree species. Therefore, we posit that, while age and climate do have a stronger influence on tree growth, it is important to consider soil as a growth factor, particularly at the distribution margins along climatic gradients.

Assessing natural versus anthropogenic horizons through deposit modelling strategies at the Medieval Site of Santa Margarida (Martorell, Barcelona, Spain)

AbstractGeophysical surveys have been one of the most useful tools for non‐invasive archaeological field assessment. Whereas they have been regularly put into practice at the archaeological site of Santa Margarida (Martorell, Barcelona, Spain), the particular features of the site required a more specific strategy to identify the contact interface between anthropogenic and natural deposits and, therefore, to conclude the archaeological excavation. As the archaeological site is settled on Quaternary alluvia at the confluence of two rivers, and in the absence of built structures in some areas, it was extremely difficult to distinguish between anthropic layers and those silty or sandy natural deposits during fieldwork. Extensive soil survey by means of borehole logging, full‐coring, and Dynamic Penetrometer Super Heavy testing within this site has proved to be a useful strategy to identify the geological horizon and to map the original relief of past landscape before excavation tasks. This enabled us to plan our fieldwork better and to interpret particular features of the site. This paper aims at summarising the results of recent surveys and discussing the potential of this approach for the study of rural settlements and agrarian landscapes in the Middle Age.

Edaphic status along altitudinal gradients of Bagale hills forest reserve, Adamawa State, Nigeria

An extensive soil survey of the Bagale Forest Reserve, an old reserve in North East Nigeria was conducted, to ascertain its soil status because of exposure and vulnerability to various anthropogenic activities which have been exacerbated by climate change over time. Five fragments within the altitudinal gradients were selected using LANDSAT ETM+ satellite imagery from Google earth. The fragments selected as samples include Tudunwada (500m) above sea level. Composite soil samples were collected and sent to the laboratory for analysis. Physical properties of the soil revealed a preponderance of sand (84%), and low percentages of silt (4%), clay (6%) while pores spaces ranged between 28.80-39.49% in both surface and sub-surface. Chemical properties revealed low pH (5.4-6.09), EC (0.06-.10m3m-1), percentage base saturation ranged between (54.08-85.38). The results showed variations in soil properties in the lower, mid and high elevations of the gradient. However, the ANOVA revealed no significant difference in same. The soil of this area will require adjustments and interventions to be able to sustain this forest reserve.

Review of the Spatial Distribution, Source and Extent of Heavy Metal Pollution of Soil in China: Impacts and Mitigation Approaches.

Background.China has undergone a rapid industrial revolution and urbanization during the past three decades. This expansion is largely responsible for the release of a large amount of heavy metals into soils and is increasingly raising concerns over the potential effects on human health and the environment. The problem is drawing increasing attention, especially after an extensive nationwide soil survey report in 2014. A number of studies have examined soil contamination by heavy metals in China. However, most of these studies have been small in scale and it is therefore challenging to get a general overview of the level of contamination across the entire country.Objectives.The present study is aimed at presenting a synthesized overview of the extent, pattern, and impact of heavy metal contamination of soils in China, including mitigation approaches.Methods.Eighty-six journal articles and other literature such as reports, internet sources, and statistical yearbooks were narratively and critically synthesized to compile a holistic summary of sources of heavy metals, the extent of pollution, spatial distribution and impact of heavy metal contamination in China. The major findings from these studies are presented, along with mitigation approaches applicable to China.Discussion.A synthesis of major findings from recent scientific journals shows that about 10.18% of farmland soils which supports 13.86% of grain production in China is affected by heavy metals. The main sources of pollution are anthropogenic activities. Even though the spatial distribution of pollution is highly variable owing to natural and human factors, provinces with intensive industrial activities such as Henan, Shandong, and Sichuan are more highly polluted than others. These regions are top grain producing areas and hence require close follow-up for development of feasible approaches to mitigating crop contamination and associated health risks emerging in parts of China. The government recently launched a program aimed at determining sound reclamation strategies.Conclusion.Mitigation of heavy metal contamination in China requires coordination of different actors and integration of all feasible reclamation approaches.Competing Interests.The authors declare no competing financial interests.

The Role of Legumes in Plant Community Succession of Degraded Grasslands in Northern China

AbstractLegume species were more and more commonly introduced to degraded grassland for human‐aided restoration. This study aimed to test whether the natural spread of legume contributes to reversal of grassland degradation through making an extensive grassland vegetation and soil survey in Inner Mongolia of China. The results showed that legume biomass increased along a gradient of soil coarsening that was also a gradient of grassland degradation. The total biomass rather than legume biomass was limited by mean annual precipitation at plot level. The presence of legumes increased species richness in degraded steppe vegetation. Constancy of intermediate and climax species of vegetation succession at sites with legumes was higher than that at sites without legumes, implying that legumes might contribute positively to the reversal of grassland degradation. Our study suggests that naturally distributed legumes could benefit the reversal of grassland degradation through promoting plant community succession rather than total plant biomass. Planting legumes would be an effective measure to accelerate the recovery process of degraded grassland with coarsened soil in regions similar to our study region. Copyright © 2015 John Wiley & Sons, Ltd.

Actual soil conditions of tsunami-hit farmland : 4. Fertility of tsunami deposits revealed by the extensive soil survey in coastal areas of Miyagi Prefecture(Progress Review: Tsunami affected farmland)

Actual soil conditions of tsunami-hit farmland : 4. Fertility of tsunami deposits revealed by the extensive soil survey in coastal areas of Miyagi Prefecture(Progress Review: Tsunami affected farmland)

Applications of stochastic models and geostatistical analyses to study sources and spatial patterns of soil heavy metals in a metalliferous industrial district of China

An extensive soil survey was conducted to study pollution sources and delineate contamination of heavy metals in one of the metalliferous industrial bases, in the karst areas of southwest China. A total of 597 topsoil samples were collected and the concentrations of five heavy metals, namely Cd, As (metalloid), Pb, Hg and Cr were analyzed. Stochastic models including a conditional inference tree (CIT) and a finite mixture distribution model (FMDM) were applied to identify the sources and partition the contribution from natural and anthropogenic sources for heavy metal in topsoils of the study area. Regression trees for Cd, As, Pb and Hg were proved to depend mostly on indicators of anthropogenic activities such as industrial type and distance from urban area, while the regression tree for Cr was found to be mainly influenced by the geogenic characteristics. The FMDM analysis showed that the geometric means of modeled background values for Cd, As, Pb, Hg and Cr were close to their background values previously reported in the study area, while the contamination of Cd and Hg were widespread in the study area, imposing potentially detrimental effects on organisms through the food chain. Finally, the probabilities of single and multiple heavy metals exceeding the threshold values derived from the FMDM were estimated using indicator kriging (IK) and multivariate indicator kriging (MVIK). The high probabilities exceeding the thresholds of heavy metals were associated with metalliferous production and atmospheric deposition of heavy metals transported from the urban and industrial areas. Geostatistics coupled with stochastic models provide an effective way to delineate multiple heavy metal pollution to facilitate improved environmental management.

Geomorphological, pedological and dendrochronological signatures of a relict landslide terrain, Mt Garbatka (Kamienne Mts), SW Poland

In the Kamienne Mountains the largest concentration of apparently relict landslides in the Sudetes range occurs. On the northern slopes of Mt Garbatka mass movements re-shaped two adjacent slope hollows and a wide depositional area is located down the valley. The main landslide body is nearly 1km long and 200–300m wide. Its flattened surface morphology and the occurrence of large dispersed allochtonous boulders in the distal part suggests a flow-like movement, initiated by shallow translational slides in the upper slopes. The thickness of colluvium, determined by an ERT survey, may reach 10m. Geomorphic signatures of mass movement are subdued, suggesting that considerable time has elapsed since the origin of the landslide and that large-scale mass movements are likely pre-Holocene in age. This is consistent with the results of an extensive soil survey within the landslide body and on the surrounding slopes. Similarity of soil properties and well-developed horizonation of profiles both within the landslide and outside it shows that no major disturbance has taken place during the soil formation period. Dendrogeomorphological research, in turn, yielded evidence of numerous growth disturbances recorded in tree rings of Norway spruce growing on the landslide body. These signals are interpreted that the slope surface is not entirely stable under current environmental conditions. Flow or creep of landslide material is not very likely, given the characteristics of cover materials, and it is hypothesized that dendrochronological signals develop in response to ground deformation through piping and throughflow. Landslide hazard in the valley below Mt Garbatka appears low at present but to claim complete stability would be premature.

Heavy Metal Contamination of Soil in Zhuzhou Smelting

To date, environmental issues become increasingly prominent, especially heavy metal (Pb and Zn) pollution of soil. This paper describes the procedure of detecting heavy metal content in soil from Zhuzhou Smelting in order to understand the contamination degree of heavy metals. An extensive soil survey was conducted in the plant include lead and zinc major production areas. Microwave digestion and ICP-AES technology were used to test metal content in soil. The results revealed that the soil in the area had been polluted by Pb and Zn, however, the pollution degree of each type of metals was not identical. In general, the Smelting was slightly polluted by heavy metals, with the highest concentration being in the Zinc sulfide plant. The heavy metal content in deep soil was a little bit higher than surface except for the Zinc sulfide plant. The reason may related to its particular location.

A Land Suitability Study for the Sustainable Cultivation of the Halophyte Salicornia bigelovii: The Case of Abu Dhabi, UAE

A land suitability study covering an area of 56,655 square kilometers was carried out for the cultivation of a halophytic bioenergy crop, Salicornia bigelovii, in the Emirate of Abu Dhabi using data collected from an extensive soil survey (scale of 1:100,000). Two simple limitation methods (referred to in the paper as the conservative and weighted methods) were used to interpolate soil map unit data for qualitative evaluation of the land. Land suitability was assessed based on a set of criteria developed in accordance with specific plant requirements and two policy scenarios regarding the use of arable land for saline agriculture. Both methods showed similar suitability outcomes, but the weighted method using weighted averages of soil components within a soil map unit produced more realistic results that reflect on the inherent heterogeneous properties of Abu Dhabi soils. Up to 69% of the examined land is found to be moderately suitable for S. bigelovii cultivation but the most suitable areas are located on the coastal zone of Abu Dhabi, and the most limiting factors are predominantly soil salinity and drainage.

IDENTIFYING AND MAPPING SALT-AFFECTED LANDS IN HAMBANTOTA DISTRICT, SRI LANKA: AN INTEGRATED GIS AND REMOTE SENSING APPROACH

Since available lands in Sri Lanka is decreasing every year mainly due to degradation oflands, it is very important to restore these lands for useful agricultural production. In thisregard, identification of salt-affected lands and differentiates into salinity levels wouldhelp to take necessary actions to restore these lands.An extensive soil survey was conducted throughout the Hambantota district in order to10 0 to to KA•••••.•.identify the salt-affected lands in the district The sampling was done at different depths(i.e. O-lOcm, IO-20cm, 20-30cm, 30-4Ocm and 40-50cm) by using a manual soil auger.The distance between sampling sites was approximately 3km. The exact position ofsampling points in latitude and longitl!c!~ ~ identified by GP~ (Global PositioningSystea), A total number of 100 points and 400 samples were collected. Topographicmaps of survey of Sri Lanka used in the study were Timbolketiya (82), Kataragama(83),Yala(l4), Hambantota(88) and Tissamaharama(89) of scale 1:50,000. Digital thematicmaps of same map sheets and Scale of I :25000 digital maps were also been used.The samples were taken to the laboratory of the Department of Crop Science, Faculty ofAgriallture, University of Ruhuna, where EC and pH measurements were taken using theEC meter and the pH meter. AIl the locational data taken using GPS system, entered intoa database. EC and pH data also been entered to the database. Using ArcView software, apoint map was generated using all the locational data including EC and pH values asattribstes. By applying interpolating techniques, salinity maps were produced.

Assessment of heavy metals contamination in urban topsoil from Changchun City, China

Due to the rapid urbanization and industrialization that has occurred in China over the last few decades, metals have been continuously emitted into the urban environment and now pose a serious threat to human health. Indeed, there is a growing concern over the potential for pollution of urban soils with heavy metals. Therefore, an extensive soil survey was conducted in urban areas of Changchun, China, to evaluate the current status of heavy metal contamination in soils and to evaluate its potential sources. A total of 352 samples of urban soils were collected from urban areas of Changchun using a systematic sampling strategy in which one sample per km 2 was taken (0 ~ 20 cm). The levels of Cu, Pb, Zn and the major elements (Mn, Al 2O 3, CaO, Fe 2O 3, MgO, SiO 2, K 2O and NaO) were then determined by X-Ray fluorescence spectrometry (XRF), while the level of Cd was determined by graphite furnace atomic absorption spectrometry (GF-AAS), and the Hg and As concentrations were determined by atomic fluorescence spectroscopy (AFS). The results indicated that, when compared with the background values of topsoil in the Changchun region, the topsoil in urban areas were enriched with metals, particularly Cu, Cd, Zn, Pb and Hg. The results of correlation coefficient analysis showed that Hg, As, Cd, Cu, Pb and Zn were significantly positive correlated with each other, while Cr and Mn formed another group. Moreover, significantly positive correlations were observed between pH and Zn, Pb, Cu, Cd, As and Hg, indicating that pH influences the distributions of these metals in urban soils in Changchun. Principal component analysis (PCA) was conducted to identify sources of heavy metals and the results revealed distinctly different associations among the trace metals and the major elements in the urban soils. The concentration of Cr appeared to be controlled by the parent material (natural sources), while Cu, Pb and Zn were mainly from vehicle emissions, with Zn primarily coming from vehicle tires. Additionally, Hg and As primarily originated from coal combustion, while Cd was mainly associated with industrial sources. According to the pollution index (PI) of each metal, the overall levels of metal pollution were not especially high, but there were clearly contaminated sites concentrated in the central and northeast portion of the studied region. The Nemerow integrated pollution index (NIPI) of the seven metals also indicated that urban soils in Changchun city were classified as having low level of pollution.

Polycyclic aromatic hydrocarbon concentrations in urban soils representing different land use categories in Shanghai

An extensive soil survey was carried out in Shanghai to investigate the spatial distribution and possible sources of polycyclic aromatic hydrocarbons (PAHs) in urban soils. Soil samples were collected from highways, iron-smelting plants, steel-smelting plants, shipbuilding yards, coking plants, power plants, chemical plants, urban parks, university campuses and residential areas and were analyzed for 16 PAHs by gas chromatography with mass detection. High PAH concentrations were found in all locations investigated, with mean values of soil total PAH concentrations in the range 3,279–38,868 μg/kg DM, and the PAH concentrations were significantly influenced by soil organic matter content. Soil PAH profiles in all districts were dominated by PAHs with 4–6 rings. Principal components analysis and diagnostic ratios of PAHs indicate that they were mainly derived from coal combustion and petroleum but in soils from highways the PAHs were derived largely from vehicle exhaust emissions. The high concentrations of PAHs found indicate that many urban soils in Shanghai represent a potential hazard to public health.

Soil organic carbon dynamics at the regional scale as influenced by land use history: a case study in forest soils from southern Belgium

AbstractLand use change (LUC) is known to have a large impact on soil organic carbon (SOC) stocks. However, at a regional scale, our ability to explain SOC dynamics is limited due to the variability generated by inconsistent initial conditions between sample points, poor spatial information on previous land use/land management history and scarce SOC inventories. This study combines the resampling in 2003–2006 of an extensive soil survey in 1950–1960 with exhaustive historical data on LUC (1868–2006) to explain observed changes in the SOC stocks of temperate forest soils in the Belgian Ardennes. Results from resampling showed a significant loss of SOC between the two surveys, associated with a decrease in variability. The mean carbon content decreased from 40.4 to 34.5 g C kg−1 (10.6 to 9.6 kg C m−2), with a mean rate of C change (ΔSOC) of −0.15 g C kg−1 year−1 (−0.023 kg C m−2 year−1). Soils with high SOC content tended to loose carbon while conversely soils with low SOC tended to gain carbon. Land use change history explained a significant part of past and current SOC stocks as well as ΔSOC during the last 50 years. We show that the use of spatially explicit historical data can help to quantitatively explain changes in SOC content at the regional scale.

Potential risk of soil salinization in different regions of Central Asia with special reference to salt reserves in deep layers of soils

To analyze the potential risk of secondary soil salinization along with the development of irrigation agriculture, an extensive soil survey was conducted with special reference to the salt concentration in deeper layers of soils in different regions of Central Asia (Kazakhstan and Uzbekistan). In total, 41 soil profiles from different scales of distance, that is, from within respective farms to over different countries, were analyzed for soluble salt contents and particle size distribution. A regional trend was found in terms of the contents of soluble salts in the 100–200 cm layers of soils, which is considered to represent a potential risk of secondary soil salinization. The detailed findings were as follows. In the Ili watershed, the contents of soluble cations tended to be low. In the Fergana regions, the contents of soluble cations and sodium adsorption ratio (SAR) were relatively low, but increased in the lower watershed of the Syr-Darya River. It is considered, on a geochemical scale, that the most mobile species, such as Na+ and Cl−, tend to be removed from the upper regions and concentrated in the lower watershed. In northern Kazakhstan, soluble cations were usually high in subsoils with a high proportion of Na. These salts were considered to be derived from fluvial deposits that extensively cover this region. Therefore, although rainfed agriculture is most common in this area, the risk of secondary salinization is high with the introduction of irrigation agriculture in the future. Thus, the salt contents in deep soil layers are primarily determined by geochemical factors, with the accessory factors of soil texture and topography (or water regimes) affecting the salinization risk in certain regions. In contrast to non-irrigated conditions, under irrigated conditions, the upper layers of soils usually accumulate higher concentrations of soluble cations compared to the 100–200 cm or even deeper soil layers, and as a result SAR increases, indicating a process of secondary soil salinization. There is a higher fundamental risk (i.e. by geochemical factors) for secondary salinization in the lower watershed of the Syr-Darya River and in northern Kazakhstan than in the alluvial fans, such as the Ili and Fergana basins. For sustainable maintenance of irrigation agriculture, further extension in the lower watershed of large rivers should be reconsidered.

Pollutants in Hong Kong soils: Polycyclic aromatic hydrocarbons

An extensive soil survey was carried out to study the polycyclic aromatic hydrocarbon (PAH) contaminations in 138 soil samples collected throughout Hong Kong. Results demonstrated that there were low levels of PAH contaminations (median of summation operator 16US EPA PAHs=140 microg kg(-1)) for all land uses (urban park, greening area, country park, rural area, restored landfill, agricultural farmland, orchard farm, crematorium, industrial and near highway area). However, localized hotspots were identified with summation operator 16PAH concentrations as high as 19,500 microg kg(-1) in one urban park. These findings were also confirmed by multivariate analysis. Comparison of PAH profiles showed a widespread domination of its 4-ring member. The major contribution was vehicular emissions from petroleum, and however at the hotspots, the improper disposal of used motor oils. In general, the pollution levels for all the land uses were below the recommended values for residential and general purposes stated in soil quality guidelines such as Netherlands and Denmark except certain identified hotspots. The potential health hazards imposed by these hotspots were alarming, and their existence (3 out of 138 samples) suggested that sole monitoring of atmospheric PAHs may not adequately address the hidden risks to human in urban city.

Elevations of sulfurous layers in acid sulfate soils: What do they indicate about sea levels during the Holocene in eastern Australia?

This study is the first large scale examination of the stratigraphic relationships of acid sulfate soils in Australia. Field and laboratory data from 346 excavated acid sulfate soil profiles for an extensive soil survey undertaken to map their extent were classified into non acid sulfate soil (NASS), potential acid sulfate soil (PASS), and actual acid sulfate soil (AASS) layers, and the elevation of these layers within different geomorphic environments was examined. Layers containing sulfurous materials were found at 0.35 m below mean sea level in intertidal swamps, around mean sea level in areas subject to intermittent water logging, and greater than 0.40 m above mean sea level in other areas. Sulfurous materials in intertidal swamps represent present day formation while in other landforms are evidence for a sea level that was once higher than at present. The division of sulfurous sediment elevations into two groups above present day sea level could be explained by two processes. Firstly, two periods of higher sea level during the Holocene could result in sulfurous materials at different levels. Secondly, the barrier system which developed along the NSW coast during the Holocene and impounded a series of estuarine mud basins could have resulted in the formation of sulfurous materials at higher elevations along the edge of the lakes and at lower elevations on the lake beds themselves.

Geochemical features of topsoils in the Gaza Strip: Natural occurrence and anthropogenic inputs

The aims of this study were to establish the current contents of trace metals and major elements in agricultural soils of the Gaza Strip and to identify the main anthropogenic inputs affecting trace metal contents. An extensive soil survey was conducted in agricultural and nonagricultural areas. One hundred and seventy sites that represent a broad range of soil types and locations were selected. The results revealed that soils in the Gaza Strip fall within the range of uncontaminated to slightly contaminated. Up to 90% of the tested soils had trace metal contents equal to the international background values. Ten percent showed slight contamination, primarily by Zn, Cu, As, and Pb, due to anthropogenic inputs, and the mean concentrations of these elements were 180, 45, 13, and 190 mg/kg, respectively. The trace metal contents varied, with the highest contents detected in the southern regions (where one finds clay soil and low precipitation) and the lowest in the northern areas (where are sandy soil and high precipitation). The soil geochemistry is dependent on soil type and location and to a lesser extent on crop pattern and fertilizer and fungicide application. Anthropogenic inputs lead to the enrichment of Zn, Pb, Cu, and Cd in the agricultural soils. The pollution of several investigated sites was found to be most severe for Zn, Pb, Cu, Cd, and, to a somewhat lesser extent, for As, whereas anthropogenic input of Hg, Ni, and Co seemed to be less important. The application of Cd-containing phosphate fertilizers coupled with Cu-containing fungicides may be an important source of Cd and Cu in several soils. High Zn levels (1000 ppm) in several soils may be caused by sewage sludge, which has an average Zn content of 2000 ppm. Saline-sodic soils were found in the central and southern regions, where the soils are characterized by high contents of Na and salty groundwater. Elevated Cl, Na, Zn, and Pb contents in some areas need further investigation to determine their ecological and health implications.

Geoambientes do Parque Estadual do Ibitipoca, município de Lima Duarte-MG

Foram identificados, mapeados e caracterizados os geoambientes do Parque Estadual do Ibitipoca (PEI), Minas Gerais, com o objetivo de subsidiar o manejo ecológico da área. Para este fim, realizaram-se coletas de solos, em pontos georreferenciados por GPS (Global Positioning System), fotointerpretações a partir de ortofotos e uso de mapas planialtimétricos, além de intenso reconhecimento de solos no campo. Oito geoambientes foram identificados e caracterizados: (1) Patamares com Espodossolos, 2) Cristas Ravinadas, 3) Escarpas, 4) Grotas, 5) Mata Baixa com Candeia, 6) Mata Alta sobre Xisto, 7) Topos Aplainados e 8) Rampas com Vegetação Aberta. Em cada ambiente a vegetação associada é fortemente condicionada pela profundidade do solo e pelo tempo de permanência de água no sistema. Os ambientes de mata, tanto sobre xistos quanto sobre quartzitos, sofrem menor estresse hídrico, seja por melhores condições físicas do solo e maior retenção de água, seja pela presença de ambiente mais ombrófilo e úmido, como nas Grotas. Os geoambientes florestados possuem concentrações de P e K mais elevadas do que nos ambientes campestres abertos. No geoambiente de Mata Baixa com Candeia, a pobreza química do substrato parece ser o impedimento à ocorrência de uma floresta mais densa. Os Campos de Altitude ocorrem nas altitudes mais elevadas no PEI, sendo desenvolvidos sobre solos mais profundos do que sob campos rupestres, onde há freqüente exposição da rocha ou solos muito rasos.

Heavy metal contamination of urban soils and street dusts in Hong Kong

Due to rapid urbanisation and scarcity of land, most of the urban parks and recreational areas in Hong Kong are built close to major roads or industrial areas, where they are subject to many potential pollution sources, including vehicle exhaust and industrial emissions. An extensive soil survey was conducted in urban parks of Hong Kong to study the current conditions of heavy metals contamination in soils. Soil samples and associated street dusts were collected from more than 60 parks and public amenity areas in old urban districts, industrial areas and New Towns of the territory. Soils were also sampled in the remote country parks to establish the baseline conditions. The total concentrations of heavy metals and major elements in the samples were determined. The results indicate that urban soils in Hong Kong have elevated concentrations of Cd, Cu, Pb and Zn. The parks with high metal concentrations are located in old urban commercial districts and industrial areas, indicating that the major contamination sources in these soils are traffic emissions and industrial activities. In addition, the application of Cd containing phosphate fertilizers may be an important source of Cd in urban park soils. The street dusts have highly elevated Zn concentration, particularly along the main trunk roads. The high Zn content in the street dusts may come from traffic sources, especially vehicle tyres. Selective soil and road dust samples were also analysed for potential chemical speciation by a sequential chemical extraction method. The chemical partitioning results show that Pb and Zn are mainly in the carbonate/adsorbed and Fe–Mn oxide phases, while Cu is largely associated with the organic and sulphide fractions. The high exchangeable Cd in urban soils and high concentration of Zn in street dusts need further investigation for their ecological and health implications.