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61.
Patrick A.W. van Hees David L. Jones Sara J.M. Holmström Ulla S. Lundström 《Soil biology & biochemistry》2005,37(3):517-531
Low molecular weight organic acids such as citrate and oxalate have been hypothesized to play a key role in rhizosphere ecology and pedogenesis. A mathematical site-specific model, DYNLOW, was constructed to describe the temporal and spatial dynamics of these organic acids in coniferous forest soils using the modelling software STELLA®. Experimentally derived values for biodegradation, adsorption, and daily values of soil temperature, moisture and hydrological flow were used to parameterize the model. The model describes the dynamics and downward movement of oxalate and citrate through the horizons (O, AE, E, Bhs, Bs) of three podzolic soil profiles in Sweden. After calibration, the model predicted average soil solution organic acid concentrations ranging from <1 to 90 μM, which was in agreement with experimental measurements (<1 to 116 μM). The model results indicated that microbial degradation of organic acids was in quantitative terms the biggest process regulating soil solution concentrations. Primary production rates of organic acid in the soil were predicted to be high (<1 to 1250 nmol g−1 soil d−1) in comparison to the amount present at steady state in the soil solution pool (<0.1 to 240 nmol g−1 soil). The downward transfer of organic acids between soil horizons due to mass flow was predicted to be a small flux (<0.1 to 3% of the total loss) compared to that lost by microbial biodegradation. The model predicted that the amount of basal soil respiration that could be attributable to the microbial turnover of organic acids was on average 19±22% of the basal CO2 production across all sites and horizons for citrate and 7±7% for oxalate. The model results are discussed in the context of pedogenesis, forest soil respiration and organic matter production. 相似文献
62.
以农药阿特拉津为研究对象,通过在北京郊区一个面积为72 9m2 (2 7m×2 7m)的田间采集10 0个土壤样品,分别测定其主要理化特性,由土壤的机械组成和干容重测试数据,采用土壤传递函数生成了vanGenuchten型的水力学参数,并进一步间接计算得到阿特拉津运移的弥散度,同时,由实测的土壤有机碳含量估算了阿特拉津的吸附参数。在此基础上,根据柱模型假设,运用HYDRUS 1D软件,就所设计的由实际背景概化而来的降雨入渗—重分布算例,对阿特拉津在农田尺度非饱和土壤中的淋溶动态进行了数值模拟。结果表明:对一场雨量为90mm、雨强为30mmd-1的降雨,在连续3d降雨接着重分布2 0d的情况下,若忽略蒸散作用对土壤水分和阿特拉津运动的影响,则降雨入渗和降雨入渗—重分布过程结束时,通过土壤2 0cm耕层的阿特拉津的最大累积淋溶量分别占施用量的17.87%和75 .4 1% ;采样区域内阿特拉津淋溶通量的空间分布存在较大差异。所探明的阿特拉津易淋溶带,不仅为合理使用该农药、保护土壤环境提供了定量的依据,而且为预防该农药对浅层地下水的污染提供了重要的信息 相似文献
63.
Kati?VaajasaariEmail author Anneli?Joutti Eija?Schultz Salla?Selonen Henrik?Westerholm 《Journal of Soils and Sediments》2002,2(4):194-202
Background Petroleum products are widely used in various sections of industry and they are one of the most abundant sources of environmental
contamination. These products are classified by their physico-chemical properties such as boiling point, density and viscosity.
Oil contamination in the environment is primarily evaluated by measuring the chemical concentrations of petroleum products
in the solid or water phase. The results of chemical analyses do not correspond directly with the harmful environmental effects
of petroleum products on the soil flora and fauna, because the interactions between oil compounds and the production of their
methabolites in soil are not measured in chemical assessments. These kinds of effects of complex chemical mixtures in soil
can be estimated by bioassays. Therefore, ecotoxicological tests are important for estimating soil quality in the risk assessment
of oil-contaminated soil sites.
Objectives The objective of this study was to examine the oil-contaminated soil site of a closed petrol station with both chemical and
ecotoxicological methods. The goals of this study were to compare the sensitivity of the terrestrial and aquatic bioassays
and to compare the toxicity responses of aquatic bioassays determined from three different extraction procedures. In addition,
our aim was to characterise a cost-effective battery of bioassays that could be applied to a comparison of oil-contaminated
soils. It was in our interest to investigate oil-contaminated soil with oil concentrations of 2500–12000 mg/kg and to find
out the possible differences between terrestrial and aquatic toxicity tests.
Methods Six soil samples from a closed petrol station were examined for toxicity with terrestrial and aquatic tests. Terrestrial tests
includedEnchytraeus albidus survival and reproduction assays and seed germination assays using wheat, cress, lettuce, and red clover seeds and growth
inhibition assays of onions. The toxicities of the water-extractable fractions of the soil samples obtained from three different
extractions were tested with aquatic bioassays based on plants (onion and duckweed growth inhibition tests), microbes (luminescent
bacteria test), and enzyme inhibition (reverse electron transport test, RET). Chemical analyses of the solid samples were
carried out simultaneously. Results. Oil concentrations ranged from 2500 to 12000 mg/kg, BTEX varied from 300 to 2800 mg/kg,
and fuel additives: MTBE and TAME from 0.0 1 to 260 mg/kg. Only the sample contain-ing 12000 mg/kg oil had a significant toxic
impact on all test organisms. Soil samples with oil concentrations 2500–6200 mg/ kg had no or only slight adverse effects
on the test organisms with one exception, theE. albidus reproduction test. TheE. albidus survival and reproduction tests were the most sensitive bioassays of the terrestrial tests, and the luminescent bacteria
test of the aquatic tests. 相似文献
64.
A combination of high input management systems, high annual rainfall and deep, permeable soils in northern Tasmania create conditions that are conducive to high drainage and nitrogen losses below the root zone. An understanding of the extent and mechanism of such losses will enable farm managers and their consultants to identify and implement more sustainable management practices that minimise potential adverse financial and environmental consequences. Analysing the fate of water and nutrients in farming systems is complex and influenced by a wide range of factors including management, soil characteristics, seasonal climate variability and management history of the paddock/farm in question. This paper describes a novel farm system modelling approach based on the model APSIM, for analysing the fate of nitrogen and water in mixed vegetable-based farming enterprises. The study was based on seven case farms across the Panatana catchment in northern Tasmania. Substantial simulated drainage losses (>100 mm average seasonal loss) were apparent for all crop and rotation elements across all farms in response to the surplus between crop water supply and crop water use. Crop nitrogen demand was found to be close to crop nitrogen supply for all crop and pasture rotation elements with the exception of potato, which had an average surplus nitrogen supply of 89 kg N/ha. This resulted in potato having much higher nitrate nitrogen leaching losses (32 kg N/ha) compared to other crops (<10 kg N/ha). Simulations suggest that practicable management options such as deficit-based irrigation and reduced N fertiliser rates will maintain current levels of productivity while reducing potential offsite N loss and generating significant financial savings via reduced input costs. 相似文献
65.
Kari Hyytiäinen Jarkko K. NiemiKauko Koikkalainen Taru PalosuoTapio Salo 《Agricultural Systems》2011,104(8):634-644
The study develops a bio-economic crop management model that internalizes the environmental cost of nitrate pollution, accounts for stochastic weather, and includes an option for split fertilization. The integrated model is designed to indicate whether a producer can benefit from applying fertilizer several times during the growing season, in response to crop needs, rather than a single time, at sowing. The model is parameterized for the cultivation of spring malting barley (Hordeum vulgare L.) in Southern Finland. The costs of negative externalities from nitrogen leaching are internalized in the landowner’s decision problem through a pollution tax. The results indicate that without a pollution tax a single application of fertilizer gauged to meet the needs of the entire season is optimal. With a tax, the benefits of split application - applying varying amounts of fertilizer at selected stages of the growing season - increase significantly. In comparison to a single application of fertilizer at sowing, split fertilization improves yields, increases the total amount of fertilizer used, and reduces nitrogen leaching. 相似文献
66.
67.
68.
Heathlands are endangered by both atmospheric nutrient deposition and natural succession. High-intensity management measures are considered necessary, as low-intensity measures (e.g. mowing, prescribed burning) are not able to compensate for atmospheric nutrient loads. Choppering (i.e. the near-complete removal of the O-layer) has several advantages over sod-cutting, including less waste material, faster vegetation recovery and lower costs. This raises the question addressed in this study as to the extent to which choppering and sod-cutting affect nutrient budgets in dry heathlands.We compared the quantities of N, Ca, K, Mg, and P removed by choppering and sod-cutting in the Lueneburg Heath (NW Germany). Nutrient balances were calculated by analysing atmospheric inputs, elevated leaching rates following management, and output due to the removal of above-ground biomass and humus horizons.Nutrient loss was particularly high after removal of O- and A-horizons. In contrast, increased leaching after management was of minor importance for nutrient budgets. Although considerably more nutrients were removed by sod-cutting than by choppering (e.g. N: 1712/1008 kg ha−1), nutrient output by choppering was still sufficient to compensate for 60.7 years of net N-input. Choppering was able to remove more N per volume unit than sod-cutting due to higher N-contents in the organic layer than in the A-horizon. For this reason, choppering is more economical than sod-cutting and, thus, should be considered the preferable method at sites not dominated by Molinia caerulea. A combination of high-intensity measures with prescribed burning would appear to be suitable as this would ensure more selective removal of N. 相似文献
69.
溶解性富里酸对土壤中多环芳烃迁移的影响 总被引:6,自引:0,他引:6
多数多环芳烃(PAHs)因其水溶性低,且易被土壤有机质固持,曾经被认为其迁移能力十分微弱。但土壤中溶解性有机质可能影响PAHs的溶解、吸附等环境过程,进而影响其迁移性。本文旨在研究富里酸提取的溶解性有机质(FDOM)对PAHs在土-水间迁移的影响及其可能机制。溶液化学稳定性研究结果显示,FDOM在溶液pH 2.0~7.0、CaCl2浓度0~1 500 mmol L-1范围内均能保持较好的分散性,未发生絮凝沉淀。室内土柱淋溶试验结果表明,FDOM在土壤中具有较强的迁移能力,在FDOM持续淋溶条件下,菲、芘以及苯并[a]芘在淋出液中的浓度明显提高,并有少量二苯并[a, h]蒽淋出。FDOM淋溶处理的土柱表层土壤中菲、芘、苯并[a]芘和二苯并[a, h]蒽的淋失率分别为92.06%、92.07%、84.52%和23.27%,显著高于对照组(p<0.05)。以上研究结果表明,FDOM可作为载体提高PAHs在土壤中的迁移性,增加PAHs向深层土壤和地下水迁移的可能性。 相似文献
70.
Subsurface Drainage for Rehabilitation of Waterlogged Saline Lands: Example of a Soil in Semiarid Climate 总被引:1,自引:0,他引:1
In irrigated agriculture of arid and semiarid regions, soil salinity, coupled with waterlogging, is a serious problem. Provision of subsurface drainage seems to be a prerequisite for optimal crop production. A study was conducted to evaluate the long term (8-year) impact of a subsurface drainage system on soil properties and yields of wheat. The study was located in a severely affected, waterlogged, barren, sandy loamsaline soil (Comborthids). The subsurface drainage system was installed at a 1.75 m depth with three drain spacings (25, 50, and 75 m). The drains facilitated reclamation of the waterlogged saline land which had variations in salt removal with space and time. The removal of salts from the root zone varied initially with distance from the drain and with depth. However, after a few years, the variations were reduced and the land was reclaimed sufficiently to grow most of the crops of the region. Plots provided with a drain spacing of 75 m required more time for complete reclamation compared to plots provided with 25 m drain spacing. Leaching through subsurface drainage increased soil porosity, modulus of rupture, infiltration rate, organic carbon, available nitrogen, phosphorus, potassium, and available water, and decreased bulk density differently in the three drain spacings (20, 50, and 75 m). In the 75 m drain spacing plots, soil salinity (EC e ) and water content remained higher than in the 25 and 50 m drain spacing plots. Soil EC e and water content were less near the drains, were highest in areas midway between the drains, and the effects were more apparent in the summer season. Wheat grain yield decreased with increasing drain spacings in the initial years of reclamation. With the gradual improvement in soil salinity, yields from plots with a 75 m spacing reached those of the narrower drain spacing plots by the fourth year. It was concluded that by installing a subsurface drainage system in a monsoon climate, waterlogged saline soils can be reclaimed by the natural leaching that can take place from rainfall. The optimum yield can be attained with a drain spacing of 75 m, which is 50% more than the design spacing of 50 m. Faster reclamation and more yield were obtained with a 25 m drain spacing and was achieved at a higher cost for the more expensive drainage system. 相似文献