城市土壤Pb污染特征及影响因素分析

以乌鲁木齐市和上海市中心城区为研究区域，按不同功能区对城市土壤采样并进行Pb含量及形态分析，结果表明：两市土壤Pb的平均值含量均超出相应土壤Pb的背景值。上海市土壤Pb的含量远远高于乌鲁木齐市；两市土壤Pb在各功能区的分布均存在明显差异，但两市土壤Pb在功能区的分布规律并不相同；两市土壤Pb的形态分布规律趋于一致，乌鲁木齐市土壤Pb活性要大于上海市。造成上述城市土壤Pb污染特征的影响因素有很多。     

Spatial variability of fallout-137Cs in the soil of a cultivated field

To obtain information on the spatial variability of fallout ¹³⁷Cs in the soil of a small area, the activity concentration of this radionuclide was determined in 100 soil samples, taken along the two diagonals of a cultivated field (150×100 m). The results show that the spatial distribution of ¹³⁷Cs in this field is at random. The frequency distribution of the values is skewed to the right, but not log-normal. The median activity concentration observed was 7.45 Bq kg^-1 dry soil, the values ranging from 4.8–15 Bq kg^-1. The spatial variability, as characterized by the relative decile deviation was 26%. If one tolerates for the establishment of baselines of global fallout ¹³⁷Cs in the soil an error in the mean activity concentration of 10% (20%) at the 95% confidence level, the minimum number of soil samples to be taken can be estimated as 14 (4). The total deposition of ¹³⁷Cs on the soil surface by fallout was determined as 3.3±0.4 kBq m^-2.     

A field study of the influence of land management and soil properties on runoff and soil loss in central Spain

Since the 1950s afforestation of degraded land has been the principal means of combatting erosion in a seasonally arid area of central Spain. In the 1970s tree planting of steep hillsides and gully sides was preceded by bench terracing. Experimental sites have been established to monitor runoff and soil losses under mature Pinus forest, 12-year-old Pinus forest, and Cistus matorral. The experiment is being conducted at three scales: large gully or small watershed (c. 3.5 ha), runoff erosion plot (10–21.5 m²), and rainfall simulation plot (1 m²). Monitoring began in October 1992. Discharge was recorded continuously, while sediment loss and soil moisture content were measured on a storm basis. The paper presents summary data on runoff and soil erosion for the three scales and comments on relationships between land management, site characteristics, and these losses. We stress the crucial role of vegetation and its interrelationship with soil properties such as structure and aggregate stability. Matorral was effective in combatting water and soil loss, but we question the practice of afforesting seasonally arid, steeply sided areas that have highly erodible soils.     

Transforming Pinus pinaster forest to recreation site: preliminary effects on LAI,some forest floor,and soil properties

This study investigates the effects of forest transformation into recreation site. A fragment of a Pinus pinaster plantation forest was transferred to a recreation site in the city of Bart?n located close to the Black Sea coast of northwestern Turkey. During the transformation, some of the trees were selectively removed from the forest to generate more open spaces for the recreationists. As a result, Leaf Area Index (LAI) decreased by 0.20 (about 11 %). Additionally, roads and pathways were introduced into the site together with some recreational equipment sealing parts of the soil surface. Consequently, forest environment was altered with a semi-natural landscape within the recreation site. The purpose of this study is to assess the effects of forest transformation into recreation site particularly in terms of the LAI parameter, forest floor, and soil properties. Preliminary monitoring results indicate that forest floor biomass is reduced by 26 % in the recreation site compared to the control site. Soil temperature is increased by 15 % in the recreation site where selective removal of trees expanded the gaps allowing more light transmission. On the other hand, the soil bulk density which is an indicator of soil compaction is unexpectedly slightly lower in the recreation site. Organic carbon (C_org) and total nitrogen (N_total) together with the other physical and chemical parameter values indicate that forest floor and soil have not been exposed to much disturbance. However, subsequent removal of trees that would threaten the vegetation, forest floor, and soil should not be allowed. The activities of the recreationists are to be concentrated on the paved spaces rather than soil surfaces. Furthermore, long-term monitoring and management is necessary for both the observation and conservation of the site.     

Characteristics of CO2 release from forest soil in the mountains near Beijing

CO₂ release from forest soil is a key driver of carbon cycling between the soil and atmosphere ecosystem. The rate of CO₂ released from soil was measured in three forest stands (in the mountainous region near Beijing, China) by the alkaline absorption method from 2004 to 2006. The rate of CO₂ released did not differ among the three stands. The CO₂ release rate ranged from ??341 to 1,193 mg m^???2 h^???1, and the mean value over all three forests and sampling times was 286 mg m^???2 h^???1. CO₂ release was positively correlated with soil water content and the soil temperature. Diurnally, CO₂ release was higher in the day than at night. Seasonally, CO₂ release was highest in early autumn and lowest in winter; in winter, negative values of CO₂ release suggested that CO₂ was absorbed by soil.     

Acid soil indicators in forest soils of the Cherry River Watershed, West Virginia

Declining forest health has been observed during the past several decades in several areas of the eastern USA, and some of this decline is attributed to acid deposition. Decreases in soil pH and increases in soil acidity are indicators of potential impacts on tree growth due to acid inputs and Al toxicity. The Cherry River watershed, which lies within the Monongahela National Forest in West Virginia, has some of the highest rates of acid deposition in Appalachia. East and West areas within the watershed, which showed differences in precipitation, stream chemistry, and vegetation composition, were compared to evaluate soil acidity conditions and to assess their degree of risk on tree growth. Thirty-one soil pits in the West area and 36 pits in the East area were dug and described, and soil samples from each horizon were analyzed for chemical parameters. In A horizons, East area soils averaged 3.7 pH with 9.4 cmol_c kg^???1 of acidity compared to pH 4.0 and 6.2 cmol_c kg^???1 of acidity in West area soils. Extractable cations (Ca, Mg, and Al) were significantly higher in the A, transition, and upper B horizons of East versus West soils. However, even with differences in cation concentrations, Ca/Al molar ratios were similar for East and West soils. For both sites using the Ca/Al ratio, a 50% risk of impaired tree growth was found for A horizons, while a 75% risk was found for deeper horizons. Low concentrations of base cations and high extractable Al in these soils translate into a high degree of risk for forest regeneration and tree growth after conventional tree harvesting.     

Effect of vegetation change from native broadleaf forest to coniferous plantation on selected soil properties

The objective of this study was to examine the effects of vegetation change from a native broadleaf forest to a coniferous plantation on selected soil properties, including soil texture, pH, organic matter, total nitrogen (N), total phosphorus (P), exchangeable cations (Ca²⁺, K⁺, Na⁺), and cation exchange capacity (CEC). Results showed that the amount of clay particles, Ca²⁺, and K⁺ values significantly increased, whereas Na⁺, total N, and organic matter and soil pH values decreased on the treatment plot after vegetation change. Soil acidity also increased and soil textural group changed from moderately fine-textured soils (clay loam) to medium-textured soils (loam) under both control and treatment plots. Organic matter, total N, and Na⁺ values increased, whereas Ca²⁺ concentration decreased through time on the control plot. Soil pH, total P, K⁺, and CEC did not show significant changes through time on the control plot.     

Spatial variability of soil <Superscript>137</Superscript>Cs in the South Caspian region

In a comprehensive program of environmental radioactivity survey in South Caspian region,¹³⁷Cs inventories in soil has been measured at more than 50 sites in the Iranian northern province of Guilan. This has been the first wide-range survey of soil radionuclide inventories in the narrow band sensitive ecosystem of south Caspian shore. Radioactivity measurements were carried out using HPGe gamma-spectrometry system. The activity concentration of ¹³⁷Cs in surface soil exhibits a mean value of 17.6 ± 9.4 Bq kg⁻¹, with a range of 2.3–41.7 Bq kg⁻¹. In many sites, split-level sampling method has been applied down to a depth of 20 cm. There were found generally two profiles. Most profiles exhibit a negative exponential distribution, while others revealed a clear subsurface peak in 5–10-cm layer. Cesium deposition in the study area has been estimated to be in the range of 0.38–2.9 kBq m⁻² with a mean value of 1.7 kBq m⁻². Distribution patterns of ¹³⁷Cs concentration levels and deposition values have been estimated using Kriging interpolation method. Observed hotspots in deposition pattern coincide with areas of higher precipitation.     

克拉玛依市空气质量特征分析

为研究克拉玛依市空气质量特征,对2015年克拉玛依市空气自动站监测数据进行分析。结果表明,克拉玛依市空气质量整体较为清洁,优良天数占有效监测天数的91.5%,PM_(2.5)平均浓度为31μg/m~3,PM_(10)平均浓度为64μg/m~3,PM_(2.5)在PM_(10)中占比近半;SO_2和NO_2浓度相对不高,NO_2/SO_2比值为2.4,流动源问题相对突出;对各项污染物的综合指数分担率分析发现,克拉玛依市PM_(10)和PM_(2.5)为综合指数分担率最高的因子,不足四分之一,O_3排第三位,超过五分之一,SO_2最低,仅为3.6%。     

Mobilization of metals and phosphorus from intact forest soil cores by dissolved inorganic carbon

Increased dissolved inorganic carbon (DIC) enhances the mobilization of metals and nutrients in soil solutions. Our objective was to investigate the mobilization of Al, Ca, Fe, and P in forest soils due to fluctuating DIC concentrations. Intact soil cores were taken from the O and B horizons at the Bear Brook Watershed in Maine (BBWM) to conduct soil column transport experiments. Solutions with DIC concentrations (～20–600 ppm) were introduced into the columns. DIC was reversibly sorbed and its migration was retarded by a factor of 1.2 to 2.1 compared to the conservative sodium bromide tracer, corresponding to a log K _D?=???0.82 to ?0.07. Elevated DIC significantly enhanced the mobilization of all Al, Fe, Ca, and P. Particulate (>0.4 μm) Al and Fe were mobilized during chemical and flow transitions, such as increasing DIC and dissolved organic carbon (DOC), and resumption of flow after draining the columns. Calcium and P were primarily in dissolved forms. Mechanisms such as ion exchange (Al, Fe, Ca), ligand- and proton-promoted dissolution (Al and Fe), and ligand exchange (P) were the likely chemical mechanisms for the mobilization of these species. One column was packed with dried and sieved B-horizon soil. The effluent from this column had DOC, Al, and Fe concentrations considerably higher than those in the intact columns, suggesting that these species were mobilized from soil’s microporous structure that was otherwise not exposed to the advective flow. Calcium and P concentrations, however, were similar to those in the intact columns, suggesting that these elements were less occluded in soil particles.     

Determination of radioactive elements and heavy metals in sediments and soil from domestic water sources in northern peninsular Malaysia

Soil serves as a major reservoir for contaminants as it posseses an ability to bind various chemicals together. To safeguard the members of the public from an unwanted exposure, studies were conducted on the sediments and soil from water bodies that form the major sources of domestic water supply in northern peninsular Malaysia for their trace element concentration levels. Neutron Activation Analysis, using Nigeria Research Reactor-1 (NIRR-1) located at the Centre for Energy Research and Training, Zaria, Nigeria was employed as the analytical tool. The elements identified in major quantities include Na, K, and Fe while As, Br, Cr, U, Th, Eu, Cs, Co, La, Sm, Yb, Sc, Zn, Rb, Ba, Lu, Hf, Ta, and Sb were also identified in trace quantities. Gamma spectroscopy was also employed to analyze some soil samples from the same area. The results indicated safe levels in terms of the radium equivalent activity, external hazard index as well as the mean external exposure dose rates from the soil. The overall screening of the domestic water sources with relatively high heavy metals concentration values in sediments and high activity concentration values in soil is strongly recommended as their accumulation overtime as a consequence of leaching into the water may be of health concern to the members of the public.     

Reuse of municipal effluent with drip irrigation and evaluation the effect on soil properties in a semi-arid area

Irrigation with municipal effluent was evaluated during 25 months in Southern Iran from 2003 to 2005 in which 14 tree species were irrigated with effluent and borehole water at an annual supply rate of 3,940 and 5,395 m(3) ha(-1), respectively. To mitigate the environmental effects, a drip irrigation system was designed and the amount of applied water based on pan evaporation was measured by flow meters and soil properties were monitored. The statistical results showed that the applied effluent had no adverse effect on soil properties. The soil salinity was reduced from 8.2, 6.8 and 7.0 dSm(-1) to 1.07, 1.12 and 3.5 dSm(-1 )in the soil layers 0-30, 30-60 and 60-90 cm, respectively. The SAR decreased significantly, while soil pH increased by 0.8 and 0.6 units in the layers 0-30 and 30-60 cm. A total application of 9,335 m(3)ha(-1 )of effluent with a nitrogen and phosphorus concentration of 7.9 and 10.3 mg l(-1), added 73 and 101 kg ha(-1) of nitrogen and phosphorus to the soil. Organic carbon also increased significantly. Twenty-five months irrigation with effluent caused a slight increase in soil bulk density and a slight decrease in mean permeability. Because of an efficient filtration and high discharge rate of bubblers (drippers), no considerable sign of clogging was observed.     

Effects of changing forest land definitions on forest inventory on the West Coast, USA

A key function of forest inventory is to detect changes in the area of forest land over time, yet different definitions of forest land are used in different regions of the world. Changes in the definition of forest intended to improve international consistency can affect the ability to quantify true changes over time. The objective of this study was to evaluate the effects of a definitional change from relative stocking to canopy cover on the area classified as forest land and its relationship to species and forest density in California, Oregon, and Washington. Both western Juniper and ponderosa pine will yield higher estimates of forest land area using a canopy cover definition in comparison to a stocking-based definition, with the difference being most pronounced where land is marginally forested. The change in definition may result in an additional 146,000 ha of forest land identified on the West Coast. Measuring marginal forest lands with both metrics for the first cycle after implementation should make it possible to distinguish real change from definitional change.     

Correlation between soil characteristics and lead and cadmium content in the aboveground biomass of Virginia tobacco

The study was conducted on alluvial-meadow, maroon-forest soils and vertisols with Virginia tobacco. The total content of lead and cadmium is measured through decomposition by HF, HClO₄, and HNO₃ acids. A solution of 0.005 M diethylentriaminepentaacetic acid + 0.1 M triethanolamine, pH 7.3 was used for extraction of the elements’ mobile forms from soils. The preparation of plant samples was made by means of dry ashing and dissolution in 3 M HCl. An atomic absorption spectrometer “Spektra AA 220” of the Australian company Varian was used for determination of Pb and Cd content in the soil and plant samples. Certified reference materials (three soils and tobacco leaves) were also analyzed for the verification of the accuracy of Pb and Cd determination. A correlation/regression analysis was conducted between pH, humus content, total and mobile forms of lead and cadmium in the soil, and the concentration of these elements in the aboveground biomass of Virginia tobacco. It was established that there are no statistically significant dependencies determined between soil pH and lead concentration in the plant organs of Virginia tobacco. Regressional dependencies of great significance were determined between the humus content, total and mobile lead and cadmium in the soil, and the element concentration in the leaves of the three harvesting zones.     

Analysis of urban effects on soil temperature in Ankara

In this study, data from two different meteorology stations were analyzed in order to reveal the effects of the urbanization on the soil temperature. These stations are the Ankara Meteorology Station (AMS), showing the urban effects, and the Esenbo?a Meteorology Station (EMS), showing the rural effects. The soil temperatures measured at depths of 5, 10, 20, and 50 cm at 0700, 1400, and 2100 hours between 1960 and 2005 were used in the analysis. Long-term mean monthly temperatures at each depth and at each time considered were calculated and analyzed using Sen’s slope and Mann–Kendall tests. The results showed that the mean monthly urban soil temperatures were generally higher than the rural soil temperatures. The differences between temperatures measured at 5, 10, 20, and 50 cm in urban and rural stations (ΔT _s(AMS???EMS)) ranged between 1.8°C and 2.1°C. As in the urban heat islands, the differences between the urban and rural soil temperatures are high at 2100 hours and low at 1400 hours. It was also observed that, due to the increasing number of buildings around the Esenbo?a Station in recent years, the difference between the urban and rural soil temperatures seems to have become smaller. These show that the factors affecting the urban heat islands and those affecting the soil temperatures are similar. Also, the temperature differences were observed to be higher during the warm season than in the cold season. The frequency distributions of the temperature differences (ΔT _s(AMS???EMS)) reveal both positive and negative values. However, the positive temperature differences are obviously prevalent.     

Re-construction and updating our understanding on the global weapons tests 137Cs fallout

Global nuclear weapons tests fallout of 137Cs in the northern hemisphere has been documented in the UNSCEAR (United Nations Scientific Committee on the Effect of Atomic Radiation) reports. However, many questions have arisen during the past three to four decades; e.g. the water column inventory of 137Cs in the North Pacific Ocean was two to three time higher than the cumulative decay corrected fallout at the same latitude as stated in the UNSCEAR reports. Here we show more precise spatial distribution of global 137Cs fallout primarily on the basis of global measurements in rain, seawater and soil, as data from 10 degrees x 10 degrees grids. A typical feature of geographical distribution is that two high global 137Cs fallout areas exist in the northern hemisphere, where the highest 137Cs fallout was observed in the globe. These areas correspond to crossovers of areas where larger precipitation amounts were expected and where higher stratosphere-troposphere exchange was expected. Our new estimate of 765 +/- 79 PBq as global 137Cs fallout for the northern hemisphere is 1.4 times higher than that of 545 PBq in the UNSCEAR reports.