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1.
Background, Aims, and Scope  More frequent occurrence of stronger floods in Europe as well as in other parts of the world in recent years raises major concern about the material damages, but also an important issue of contamination of the affected areas through flooding. The effects of major floods on levels and distribution of contamination with hydrophobic organic pollutants were examined from the continuous set of data for floodplain soils and sediments from a model industrial area in the Czech Republic where a 100-year flood occurred in 1997. The goal of this study was to evaluate the risk related to contamination associated with such extensive natural events and characterize the spatial and temporal distribution and dynamics of pollutants related to a major flooding shortly after the floods and also in the time period several years after floods. Methods  Sediments and alluvial soils from fourteen sites each were repeatedly sampled during the period from 1996 until 2005. The sampling sites represented five regions. Collected top-layer sediment and soil samples were characterized and analyzed for hydrophobic organic pollutants PCBs, OCPs and HCB using GC-ECD and PAHs using a GC-MS instrument. Spatial and temporal differences as well as the relative distribution of the pollutants were examined in detail by statistical analysis including multivariate methods with special emphases placed on the changes related to floods. Results  The organic pollutants levels in both alluvial soils and sediments exceeded the safe environmental limits at numerous sites. Pollutants concentrations and relative distribution as well as organic carbon content in both sediment and floodplain soils were significantly affected by the flooding, which resulted in a decrease of all studied contaminants in sediments and significant rise of the PAH pollution in the flooded soils. There was a unique and highly conserved PAH pattern in soils regardless of the floods and greater changes in PAH pattern in sediments related to floods. The relative distribution of individual PAHs reflected a combustion generated PAH profile. PAH levels in the river sediments rose again at the sites with continuous sources several years after floods. Discussion  The results showed different dynamics of PAHs and PCBs during the floods when PAHs were redistributed from the sediments to alluvial soils while PCBs have been washed out of the study regions. The data reveal longer contamination memory and consistent contamination pattern in soils, whereas sediments showed more dynamic changes responding strongly to the actual situation. The stable PAH pattern within the regions also indicates that a relative amount of all compounds is comparable across the samples and, thus, that the sources at different sites have similar character. Conclusions  Sediments have the potential to function as a secondary source of contamination for the aquatic ecosystem, but also for the floodplain soils and other flooded areas. The floods served as a vector of PAHs contamination from sediments to soils. The reloading of river sediments in time, namely with PAHs, due to present sources increases their risk as a potential source in the next bigger flood event both to the downstream river basin and affected alluvial soils. Recommendations and Perspectives  The results stress the importance of including the floodplain soil contamination in the risk assessment focused on flood effects. Floodplain soils have stable long-term environmental memory related to contamination levels, pattern and distribution, whereby they can provide relevant information on the overall contamination of the area. The sediments will continue to serve as a potential source of contaminants and alluvial soils as the catchment media reflecting the major flood events, especially until effective measures are taken to limit contamination sources. ESS-Submission Editor: Dr. Henner Hollert (Hollert@uni-heidelberg.de) This article is openly accessible!  相似文献   

2.
Contents of polycyclic aromatic hydrocarbons (PAH) and their distribution pattern in soils with different contamination levels In order to study the PAH-contamination of soils in North Rhine Westfalia, soil samples were taken at different sites and analysed for six PAH. The sites were selected with regard to different forms of land use such as arable land and pastures in rural areas and gardens in urban areas and with regard to varying immission situations. The results are valued according to reference (RW) and test values (PW) of the Netherlands Guidelines for soil restoration. The reference values of these guidelines characterizing normal contents are regularly and in part distinctly exceeded for fluoranthene and benzo(a)pyrene at some sites (coking plant, alluvial meadow soils, allotment gardens, close to a highway). The check values which imply more exact investigations are only exceeded at the most contaminated site, a coking plant. The PAH patterns at the different sites investigated depend on the number and kind of PAH sources. PAH typical for motor vehicle emission (benzo(b)fluoranthene, benzo(g,h,i)perylene) are dominating in soils close to a highway, whereas at the cokery site fluoranthene can be found in higher concentrations than the other PAH. In alluvial river soils and in soils of allotment gardens the pattern is more uniform because of diffuse sources with decreasing contents in the order fluoranthene > benzo(a)anthracene > benzo(b) fluoranthene > benzo(g,h,i)perylene > benzo(a)pyrene > benzo(k)fluoranthene. As a guide substance for a first risk assessment benzo(a)pyrene is suitable, since its content shows a strong correlation to the sum of five other PAH. In order to characterize the background contamination of soils with PAH new reference values are proposed.  相似文献   

3.
Conversion of meadow and forest ecosystems to agricultural land generally leads to changes in soil structure. This comparative study presents the composition and stability of structural aggregates in humus horizons (0–30 cm) of noncarbonate silty‐clay Fluvisols in the Kolubara River Valley, W Serbia. Aggregates collected from under a native forest were compared to aggregates from meadows and arable fields which underwent crop rotation for > 100 y. The results show that size distribution and stability of structural aggregates in the humus horizons of arable soil are significantly impaired due to long‐term anthropogenization. In the humus horizons, the content of the agronomically most valuable aggregates (0.25–10 mm) decreased by a factor of ≈ 2, from 68%–74% to 37%–39%, while the percentage of cloddy aggregates (>10 mm) increased by a factor of ≈ 2, from 23%–31% to 48%–62%, compared to forest aggregates. The long‐term‐arable soil had significantly (p < 0.05) lower aggregate stability, determined by wet sieving, than meadow and forest soils. The lowest aggregate stability was found in aggregates > 3 mm. Their content is ≈ 2.5–3 times lower in arable soil (13%–16%) than in forest soil (32%–42%) at a depth of 0–20 cm. The largest mean weight diameters of dry aggregates (dMWD) with a range between 12.6 and 14.7 mm were found in arable soil, vs. 9.5–9.9 mm in meadow and 6.5–8.3 mm in forest. The arable soil had significantly lower mean weight diameters of wet‐stable aggregates (wMWD) and a lower structure coefficient (Ks) than forest and meadow soils. The dispersion ratio (DR) of arable soil was significantly higher than that of forest and meadow soils. Forest and meadow showed a significantly higher soil organic‐matter content (SOM) by 74% and 39%, respectively, compared with arable soil, while meadow uses decreased the SOM content by 57% compared with forest at a depth of 0–10 cm. In conclusion, the results showed that long‐term conventional tillage of soils from natural forest and meadow in the lowland ecosystems of W Serbia degraded soil aggregate–size distribution and stability and reduced SOM content, probably resulting in lower productivity and reduced crop yields.  相似文献   

4.
中国几种主要土壤的持水性质   总被引：35，自引：0，他引：35  
陈志雄  汪仁真 《土壤学报》1979,16(3):277-281
土壤的持水性是指土壤吸持水分的能力。在对植物的有效范围内,土壤所吸持的水分是由土壤孔隙的毛管引力和土壤颗粒的分子引力所引起的,这两种力现在统称为土壤吸力,或基质吸力,它相当于土壤总水势中的基质势。  相似文献   

5.
Abstract

Higher rates of nitrification often reported in fine than in coarse textured soils may not be a direct effect of soil texture because in most of the earlier studies, soil water content has been usually expressed as gravimetric, volumetric or soil's water‐holding capacity without consideration of differences in density/ porosity for soils of varying texture. The same water content in texturally different soils could provide very different conditions of soil aeration and associated nitrifying activity. Effects of soil texture on nitrification was studied by incubating three semiarid subtropical soils having sandy loam, loam, and silty clay textures at 35°C for 30 days using water‐filled pore space (WFPS) as the criterion of soil aeration. Upland or aerobic soil conditions, simulated by incubating soil at 60% WFPS, exhibited very fast nitrification of added fertilizer nitrogen (N) and most of the applied 100 mg of ammonium‐nitrogen (NH4+‐N/kg soil) was nitrified within 10 days of incubation in all three soils irrespective of the differences in texture. Under flooded soil conditions (120% WFPS), nitrification was slow and only 84 to 92% of the applied NH4+‐N was nitrified even after 30 days. Nitrification could be described by first‐order kinetics for both the upland and flooded moisture regimes, thus nitrification rate depended upon NH4+ concentration. At similar gravimetric water contents, rates of nitrification differed greatly in soils of varying texture, but when varying water‐holding capacity and bulk density were accounted for using WFPS, all the soils behaved similarly at 60% WFPS. Under impeded aeration (flooded conditions), however, substantial differences were observed in nitrification in soils of varying texture, the largest in fine‐textured Chamror silty clay followed by Habowal loam and the smallest in Tolewal sandy loam soil. These results illustrate the utility of WFPS, compared with soil water content, and its reliability as an indicator of aeration dependent nitrification for soils of varying texture.  相似文献   

6.
Demonstration of the soil development in high flood loam of the Lower Rhine using multiple correlations, regressions and cluster analysis Several characteristics have been examined for 26 soils on high flood loam aged from 500 to 12000 years. Main results of discovered relations between duration of development and degree of characteristics are: Using multiple regression analysis continuous soil development could be stated and quantified. Square regression is better than a linear one. Employing regression being determined among some characteristics and age by means of absolutely dated soils, age of other soils in the same region can be estimated. With cluster analysis it is possible to demonstrate soil development from late pleistocene to youngest holocene too, but the relationship in ages is relative.  相似文献   

7.
洪水沉积物对长江中游洪泛区土壤钾素营养的影响   总被引：1，自引：0，他引：1  
陈世俭  马毅杰 《土壤通报》2002,33(5):343-345
本文对比研究了长江中游几类洪泛区 (江心洲、洲滩和圩垸等 )的洪水沉积物和剖面土壤的钾素营养状况。结果表明 ,相对于洪泛区耕层 (表层 )或剖面土壤的钾素状况 ,洪水沉积物的覆盖能丰富表土的钾素营养 ,显著增加表土的速效钾和缓效钾含量 ,且速效钾的增幅大于缓效钾 ,而对全钾无明显影响。沉积物对土壤钾素状况的影响与其颗粒组成、有机质含量、CEC和土地利用方式等因素有关。沉积物和土壤的钾素状况与粘粒含量 (<0 0 1mm)呈显著正相关 ,与砂粒部分呈负相关 ;有机质和CEC对土壤钾素的有效性有一定影响 ;而洪泛区土地利用方式与耕层土壤钾素的消耗有关  相似文献   

8.
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9.
Dissolved organic matter (DOM) has been recognised as a key carbon and nitrogen (N) pool involved with soil-plant-microbe interactions. Yet few studies have quantified this contribution in agricultural soils. In this study we leached DOM from a sandy loam and sandy clay loam soil under either grassland or arable cropping. Two weeks after DOM removal microbial respiration from soils was not altered. However, a significant (P<0.05) decline in microbial biomass-N, potentially mineralizable-N, gross N mineralization and gross nitrification occurred after leaching. This data illustrate that whilst DOM is a small component of the soil OM it contributed up to 25% of microbial N supply within these agricultural soils.  相似文献   

10.
Adverse changes in the physical and chemical properties of arable gray forest and soddy meadow soils (forest-steppe zone, Lake Baikal region) polluted with fluorides emitted by an aluminum smelter in Irkutsk are shown. The field experiments of the long-term (1997–2005) monitoring and laboratory incubation experiments revealed that the CO2 emission from the gray forest soil was higher than from the soddy meadow soil. Its intensity depended on the soil properties and buffering capacity of the soils to fluorides, as well as on the content of water-soluble fluorides and the hydrothermal factors.  相似文献   

11.
Annual potassium (K) balances have been calculated over a 40‐year period for five field experiments located on varying parent materials (from loamy sand to clay) in south and central Sweden. Each experiment consisted of a number of K fertilizer regimes and was divided into two crop rotations, mixed arable/livestock (I) and arable only (II). Annual calculations were based on data for K inputs through manure and fertilizer, and outputs in crop removal. Plots receiving no K fertilizer showed negative K balances which ranged from 30 to 65 kg ha?1 year?1 in rotation I, compared with 10–26 kg ha?1 year?1 for rotation II. On sandy loam and clay soils, the K yield of nil K plots (rotation I) increased significantly with time during the experimental period indicating increasing release of K from soil minerals, uptake from deeper soil horizons and/or depletion of exchangeable soil K (Kex). Significant depletion of Kex in the topsoil was only found in the loamy sand indicating a K supply from internal sources in the sandy loam and clay soils. On silty clay and clay soils, a grass/clover ley K concentration of ～2% (dry weight) was maintained during the 40‐year study period on the nil K plots, but on the sandy loam, loam and loamy sand, herbage concentrations were generally less than 2% K.  相似文献   

12.
Grinding more than doubled the respiration rate of two silt loam soils, one arable and one grassland. The increases were smaller when the grinding treatment was given to portions of soils that had previously been fumigated with CHCI3and incubated, a treatment that greatly decreased microbial biomass. The results indicate that the flush of decomposition caused by grinding was in part derived from killed organisms and in part from enhanced decomposition of non-biomass sections of the soil organic matter. Grinding killed about a quarter of the biomass in both soils. Carbon from killed organisms accounted for a quarter of the extra CO2–C evolved after grinding in the arable soil and almost half in the grassland soil. The extra non-biomass organic matter decomposing after grinding amounted to about 0.5% of the soil organic carbon in both soils. This non-biomass material rendered decomposable by grinding had a higher C/N ratio than the organic matter decomposing in unground soil.  相似文献   

13.
Cultivating grassland changes the physical state of the soil. The paper describes observations and measurements made in the field and the laboratory on a wide range of soils (with series names) in England over a period of 25 years. Dry sieving showed that natural weathering of grassland aggregates after three months'exposure was very considerable. The drawbar-pull on ploughing soil recently out of grass, as compared with old arable, increased with the number of years out of grass. The number of earthworms per hectare on old grassland was 6 to 9 times that on old arable of the same soil series: after three years'cultivation it was reduced by about a half. The possibility of erosion by wind increased with the number of years out of grass. Old arable land on gentle slopes had its resistance to flowing water (sheet erosion) much increased by as little as 2 years under grass. The apparent densities of soils were at a minimum under old grass and increased under cultivation. On some soils arable for many decades, the apparent densities were near those considered limiting for root penetration. The volurne of water per cent in the soil at the sticky point decreased as the years out of grass increased, suggesting a decrease in the number of days the soil could be cultivated without smearing. The water-stability of soil aggregates decreased as the number of years after ploughing old grassland increased. Whatever the texture, on ploughing old grassland, the water stability of air-dry aggregates feil sharply in the first – years and then approached the value corresponding to that of old arable soils more slowly, apart from soils of low clay content in which it differed little from old arable land after 2 years. Measurement of changes in water stability and field observations in a 6-course rotation (3 years ley, 3 years cereal) on a loam which had been in a similar rotation for about a decade after old grassland, suggested that this balance was probably right for maintaining such a soil at a good cropping level. Puddling (poaching) by animals of wet arable loam soils overlying clay resulted in gleying to the surface: ferrous iron was detected chemically. On putting down to grass there was little increase in water stability of the aggregates after 4 years. The reduction in the total pore space caused by harvesting machinery and also as a result of some years'cultivation of grassland was considerable. The ease of penetration of soils when taking cores was compared by counting the number of blows to drive in a corer: the number was much less in a soil recently out of old grass compared with old arable. The root development of cereals was poor in old arable silt soils very unstable to wetting and drying and with few visible biopores (> 10–00 μm). On soils with many visible pores, root development was much greater and yields with similar rates of nitrogen were double. The total N in the soils feil when old grassland was ploughed, sometimes by as much as 75 per cent in about 20 years. There was sometimes a significant corre-lation between total N and the reduction in water-stable aggregation during the years following ploughing grassland: the correlation coefficient was much higher on ploughing old grassland rather than leys. The N level dropped much more quickly in the first few years after ploughing old grassland than later. All single-property measurements give only a limited assessment of the physical state of a soil. Soils can be assessed satisfactorily only by making a range of measurements appropriate to the farming System.  相似文献   

14.
Measurements of apparent density (dry bulk density) have been used to monitor structural change in gleyed alluvial soils in Norfolk following drainage and cultivation. In Waveney series silty clay loam, drained for 9 years, soil ripening has been the dominant pedological process. Apparent density has increased throughout the drained profile due to loss of water and consequent structural rearrangement. In silty clay loam alluvium, reclaimed from the Wash over a 120-year period, soil ripening appears to be terminated after 40 years but, under continuous arable use, apparent density continues to increase in, and immediately below, the plough layer. This increase in density is accompanied by a decline in the organic-matter content of the plough layer.  相似文献   

15.
The parameters of the elemental composition, molecular weight distribution, infrared and proton spectroscopy, and hydrophilic-hydrophobic properties were determined for humic acids preparations isolated from arable horizons of soils from different natural zones (an ordinary chernozem, a soddy-podzolic soil, and a meadow sierozem). The general and specific properties of the humic acids from the three studied soils were revealed.  相似文献   

16.
开垦对草甸土有机碳的影响   总被引：14，自引：0，他引：14  
本文利用经典统计学和地统计学相结合的方法,选取科尔沁沙地东南缘草甸土两块10×10m的样地为例,分析了草地开垦8a后的耕地耕作层土壤有机碳含量和空间分布格局的变化,结果表明:草地与耕地表层(0～10cm)土壤有机碳含量差异不显著,草地亚表层(10～20cm)土壤有机碳含量低于耕地(p<0.05);草地与耕地表层和亚表层土壤有机碳空间分布格局具有明显差异,表现为草地的表层和亚表层的结构异质性分别大于耕地,分数维小于耕地,空间依赖性强于耕地,空间分布格局的破碎程度弱于耕地。耕地表层与亚表层土壤有机碳含量差异不显著(p<0.05),但空间结构特征和空间分布格局存在明显的差异;而草地表层与亚表层土壤有机碳含量差异显著(p<0.05),但空间结构特征和空间分布格局比较相似。因此,开垦不仅影响草甸土有机碳含量的高低,而且影响其空间结构特征和分布格局。这对进一步了解草地开垦对土壤有机碳及全球碳循环和气候变化的影响具有重要意义。  相似文献   

17.
土壤水分状况和质地对稻田N2O 排放的影响   总被引：34，自引：0，他引：34  
１９９４年中国科学院封丘生态试验站通过小区试验研究了土壤质地和水分状况对稻田Ｎ２Ｏ排放的影响。结果表明稻田Ｎ２Ｏ排放主要受土壤水分状况的影响,淹水状态下,Ｎ２Ｏ排放很少,水分落于期间Ｎ２Ｏ排放量占水稻生长期Ｎ２Ｏ排放总量的８７．５０％～９８．６５％。土壤质地显影响稻田平均Ｎ２Ｏ排放通量,砂质土壤排放的Ｎ２Ｏ显或极显高于壤质和粘质土壤,水稻生长期砂质、壤质及粘质土壤的平均Ｎ２Ｏ排放通量分别为１３７．６３、８７．５４和６３．６μｇＮ２Ｏ－Ｎ／ｍ＾２．ｈ。  相似文献   

18.
《Geoderma》2005,124(1-2):181-192
Contents of soil organic matter (SOM) and total nitrogen (TN) in the surface soils and subsurface soils were measured in five types of floodplains classified with different flood frequencies in river marginal wetlands of Erbaifangzi, China, in 1999. Contour maps and profile maps were constructed to describe the spatial distribution of SOM and TN in order to identify the influences of flood frequency on them. Results showed that spatial distributions of both SOM and TN were very similar in soil profiles (0–120 cm) of the five areas, decreasing gradually with depth except an accumulation peak in the flooded floodplain (B area). Also, the accumulation peak in the soil profile of B area was relevant to water table, nitrogen leaching, denitrification and mineralization. However, their horizontal distributions in surface soils (0–10 cm) were different in the five areas. Although the flood could bring the deposit of nutrients and sands, the highest content of SOM or TN did not appear in B area but in the floodplain with certain flood frequency. For example, SOM content (6.76%) in 5-year floodplain wetland was highest, and the highest content of TN (3666.4 mg/kg) appeared in 1-year floodplain wetland. However, SOM and TN contents in soils of B area were 4.08% and 2605.4 mg/kg, respectively. Soil clay content, wetland plant (Phragmites australis) litter inputs, soil moisture and water table greatly affected the spatial distribution of SOM and TN in floodplain wetlands. The ratios of carbon to nitrogen of wetland soils in this region were relatively lower than those in paddy soils. SOM and TN contents were significantly correlated with total phosphorus (TP) contents in floodplain wetlands except the 100-year floodplain wetland, but they were significantly influenced by soil pH values only in B area. Denitrification and ammonia volatilization were the main mechanisms resulting in nitrogen loss of surface soils in B area. Flood frequency significantly influenced the ecological functions such as nutrient retention and water quality maintenance of floodplains.  相似文献   

19.
Uneven moisture patterns in water repellent soils   总被引：2，自引：0，他引：2  
In the Netherlands, water repellent soils are widespread and they often show irregular moisture patterns, which lead to accelerated transport of water and solutes to the groundwater and surface water. Under grasscover, spatial variability in soil moisture content is high due to fingered flow, in arable land vegetation and microtopography play a dominant role. Examples are given of uneven soil moisture patterns in water repellent sand, loam, clay and peat soils with grasscover, and in cropped water repellent sandy soils. In addition, the influence of fungi on inducing soil moisture patterns is illustrated as well.  相似文献   

20.
Soil organic matter, effects on soils and crops   总被引：4，自引：0，他引：4  
Abstract. Manurial treatments and cropping history have remained unchanged for many years in classical and long-term experiments at Rothamsted and Woburn, in some cases for more than 100 years. Soil samples taken periodically have been analysed to follow changes in organic carbon content with time and treatment. Data presented here clearly show effects of carbon input and soil texture on equilibrium organic matter content.
Until recently increasing amounts of soil organic matter had little effect on yields of arable crops especially if fertilizer nitrogen dressings were chosen correctly. However the yield potential of many crops has increased and various agronomic inputs have become available to achieve that potential. Yields of many crops are now larger on soils with extra organic matter both on the sandy loam at Woburn and the silty clay loam at Rothamsted. Some of the effect appears to be related to extra water holding capacity, some to availability of nitrogen in ways which cannot be mimicked by dressings of fertilizer N, and some to improved soil physical properties. Responses to fertilizer N have been larger on soils with more organic matter.  相似文献   

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