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1.
The long-term impact of irrigation on a Mediterranean sandy soil irrigated with treated wastewater (TWW) since 1980 was evaluated. The main soil properties (CEC, pH, size distribution, exchangeable cations and chloride, hydraulic conductivity) as well as the organic matter and Cu, Cr and Pb speciation in an irrigated soil and a non-irrigated control soil at various soil depths were monitored and compared during a 2 year experiment. In this second part, we focused on Cu, Cr and Pb behaviour in relation with soil organic carbon (SOC). Soil samples were collected every 3 months during 2 years at the depths 0–20, 20–40 and 40–60 cm and were analysed for exchangeable and total metals, organic carbon content, metal sequential extraction and humic substances – Humic Acids (HA), Fulvic Acids (FA) and Non-Humified Fraction (NHF). Long-term irrigation with a domestic treated wastewater (TWW) may be considered safe with regard to trace metal accumulation in soil. Irrigation lowered the HA and NHF fractions of SOC and made the FA fraction more mobile. Cu bound preferentially to the SOC fraction, Cr was found mainly in the reducible fraction and Pb was bound to all fractions indiscriminately. Cu exhibited a high affinity for the HA fraction, while Pb and Cr had a high affinity for the FA fraction, which indicates a greater mobility of the organically-bound Pb and Cr than of the organically-bound Cu. Evaluation of the potential metal mobility has to take into account not only the usual speciation between labile, reducible and oxidisable fractions, but also the nature of the SOC responsible for the oxidisable fraction.  相似文献   

2.
Irrigation by treated wastewater (TWW) can pollute the soil by different organic and inorganic compounds. The pollution level can depend on the irrigation period, soil nature, and wastewater characteristics. Since 1989, the Zaouit Sousse area (central Tunisian) has been irrigated by treated wastewater. The irrigation period and the mineralogy of soil composition change from one locality to another in Zaouit Sousse area. In this work, we are interested in organic compounds, polycyclic aromatic hydrocarbons (PAHs), and heavy metals (HMs) evolution. One control soil (S1) and four irrigated areas soil (S2, S3, S4, and S5) were chosen. The soil samples differ by the irrigation period and soil characteristics. Total PAHs content in control soil was 66.2 ng?g?1 and in irrigated areas were between 46.23 and 129.51 ng?g?1. The PAHs content in irrigated soil, except S5 which has been irrigated with wastewater for 20 years and contains the highest clay fraction percent, decreased with the irrigation period (from 0 to 20 years). The microbial degradation may decrease the PAHs concentrations in the soil thanks to bacterium brought by TWW and the important soil permeability. Concentration of heavy metals ranged from 24 to 1,320 μg?L?1. The HMs (Cu, Cr, Zn, Fe, Ni, Pb, and Cd) contents decreased with the irrigation period (from 10 to 20 years). So, following the PAHs aerobic bio-degradation, this organic compound discharges their absorbed heavy metals which leached to deeper levels. The Cr, Cu, Al, Zn, and Cd mobility depend on the clay yield too. However, the PAHs and Pb mobility are also related to humic substance quantities. Cr and Cu have affinities both to clay and humic substance quantities.  相似文献   

3.
郭晓明  马腾  陈柳竹  刘林 《地球科学》2015,40(11):1896-1903
污水中的悬浮物、盐分和有机营养物对土壤孔隙状况产生了深刻的影响.通过室内模拟和CT(computed tomography)扫描的方法, 定量研究污水灌溉条件下土壤孔隙数、孔隙度及形态特征.结果表明: 与对照点相比, 污水灌溉区上层土壤总孔隙数和大孔隙数(当量直径≥1.00 mm)均显著升高, 而下层土壤总孔隙数、大孔隙数、粗孔隙数(当量直径为0.26~1.00 mm)、总孔隙度、大孔隙度和粗孔隙度均显著降低(p＜0.05);在模拟悬浮液和盐液灌溉条件下, 土壤总孔隙数、粗孔隙数和粗孔隙度均有所升高, 而大孔隙数、总孔隙度、大孔隙度和孔隙成圆率均有所降低; 在模拟营养液灌溉条件下, 土壤总孔隙数、大孔隙数、粗孔隙数和粗孔隙度均有所增加, 而孔隙成圆率有所降低; 对于研究区土壤来说, 悬浮液灌溉对土壤孔隙的影响效应强于盐液灌溉; 对于同种性质的污水灌溉来说, 污灌对对照点土壤孔隙的影响效应强于污灌区土壤.   相似文献   

4.
Toxicity of heavy metals adversely affects environment and human health. Organic materials derived from natural matters or wastes have been applied to soils to reduce the mobility of contaminants such as heavy metals. However, the application of cow bone powder (CB), biochar (BC), and eggshell powder (ES) is rarely investigated for the reduction of Pb bioavailability in soils irrigated with saline water. The objective of this study was to assess the effectiveness of CB, BC, and ES additions as immobilizing substances on Pb bioavailability in shooting range soil irrigated with deionized and saline water. Each additive of CB, BC, and ES at 5 % (w/w) was mixed with soils and then the deionized and saline water were irrigated for 21 days. With deionized water irrigation, the soils treated with CB, BC, and ES exhibited higher pH when compared with saline water irrigation. With saline water irrigation, the electrical conductivity, water-soluble anions, and cations were significantly increased in soils treated with CB, BC, and ES. The water-soluble Pb in soils treated with CB, BC, and ES was significantly decreased with saline water irrigation. On the other hand, the water-soluble Pb in soil treated with CB was increased with deionized water irrigation. Only BC with saline water irrigation decreased the Pb concentration in maize shoots.  相似文献   

5.
Sodium (Na+) in poor quality irrigation water participate in ion-exchange processes results in the displacement of base cations into solution and a raised concentration in groundwater. Knowledge of the rate of decrease of nutrients from soils resulting from poor water quality application is essential for long-term planning of crop production while minimizing the impact on groundwater quality. In this study, we examined the effect of sodium adsorption ratio (SAR) of irrigation water on nutrients leaching and groundwater quality in columns of sandy soil. Three types of irrigation waters at three NaCl–CaCl2 solutions with the following levels of SAR (5, 15, and 30) were synthesized in laboratory. With the application of solutions, exchange occurred between solution Na+ and exchangeable cations (Ca2+, Mg2+, and K+), resulting in the displacement of these cations and anions into solution. Increasing the level of SAR from 5 to 15 and 30 resulted in increase in the average exchangeable sodium percentage (ESP) of the soil from 10.4 to 20.3, and 32.5, respectively. Adverse effect of high Na+ concentration in the solutions on raising ESP was less pronounced in solution having low SAR. Leaching of Ca2+, Mg2+, K+, and P from soil with the application of solutions represents a significant loss of valuable nutrients. This sandy soil showed the high risk for nutrients transfer into groundwater in concentrations exceeding the groundwater quality standard. Irrigation with poor quality water, which is generally more sodic and saline than regional groundwater, increases the rate of sodification and salinization of shallow groundwater.  相似文献   

6.
To evaluate the effect of olive mill wastewater (OMW) application on soil hydraulic and transport properties, two treatment sites, which had been irrigated with OMW for 5 and 15 years, and one control site being irrigated with freshwater were compared. The transport and leaching experiment results showed that a portion of the total soil water was available for transport processes while the remaining of the soil water was considered immobile and not readily accessible for solutes. The separation in water fractions of different mobilities was surprisingly consistent among OMW treatments. The bromide recovery rate decreased with the application of OMW showing that tracer molecules became trapped within immobile water phases. The application of OMW increased significantly the soil water-holding capacity, whereas the soil hydraulic conductivity in the near saturation range decreased significantly with long-term OMW application. The soil irrigated with OMW had significantly higher organic matter content, lower bulk density and relatively higher total porosity, but lower macroporosity than that of control sites. We concluded that the soil was increasingly coated with complex organic molecules originating from OMW, as a result, solute exchange between inter- and intrasoil aggregate water was hindered. Although OMW could cause soil and water pollution, its use in agriculture is promoted because of high nutrients and organic matter contents.  相似文献   

7.
Though irrigation with sewage water has potential benefits of meeting the water requirements, the sewage irrigation may mess up to harm the soil health. To assess the potential impacts of long-term sewage irrigation on soil health and to identify sensitive soil indicators, soil samples were collected from crop fields that have been irrigated with sewage water for more than 20 years. An adjacent rain-fed Leucaena leucocephala plantation system was used as a reference to compare the impact of sewage irrigation on soil qualities. Soils were analyzed for different physical, chemical, biological and biochemical parameters. Results have shown that use of sewage for irrigation improved the clay content to 18–22.7%, organic carbon to 0.51–0.86% and fertility status of soils. Build up in total N was up to 2,713 kg ha−1, available N (397 kg ha−1), available P (128 kg ha−1), available K (524 kg ha−1) and available S (65.5 kg ha−1) in the surface (0.15 m) soil. Long-term sewage irrigation has also resulted a significant build-up of DTPA extractable Zn (314%), Cu (102%), Fe (715%), Mn (197.2), Cd (203%), Ni (1358%) and Pb (15.2%) when compared with the adjacent rain-fed reference soil. Soils irrigated with sewage exhibited a significant decrease in microbial biomass carbon (−78.2%), soil respiration (−82.3%), phosphatase activity (−59.12%) and dehydrogenase activity (−59.4%). An attempt was also made to identify the sensitive soil indicators under sewage irrigation, where microbial biomass carbon was singled out as the most sensitive indicator.  相似文献   

8.
Soil salinity and sodicity are escalating problems worldwide, especially in arid and semiarid regions. A laboratory experiment was conducted using soil column to investigate leaching of soluble cations during reclamation process of a calcareous saline–sodic soil (CaCO3?=?20.7%, electrical conductivity (EC)?=?19.8 dS m?1, sodium absorption ratio (SAR)?=?32.2[meq L?1]0.5). The amendments consisted of control, cattle manure (50 g kg?1), pistachio residue (50 g kg?1), gypsum (5.2 g kg?1; equivalent of gypsum requirement), manure + gypsum and pistachio residue + gypsum, in three replicates which were mixed thoroughly with the soil, while sulfuric acid as an amendment was added to irrigation water. To reflect natural conditions, after incubation period, an intermittent irrigation method was employed every 30 days. The results showed that EC, SAR, and soluble cations of leachate for the first irrigation step were significantly higher than those of the subsequent leaching runs. Moreover, the concentration of removed soluble cations was lower for the control and gypsum-treated soils. It was found that among applied amendments, treatments containing cattle manure showed higher concentrations of sodium, calcium, and magnesium in the leachate, while due to pistachio residue application, further amount of potassium was removed out of soil column. The addition of pistachio residue resulted in the highest reduction in soil salinity and sodicity since the final EC and exchangeable sodium percentage dropped to 18.0% and 11.6% of their respective initial values, respectively. In the calcareous soil, solubility of gypsum found to be limited, in contrast, when it was added in conjunction with organic amendments, greater amounts of sodium were leached.  相似文献   

9.
土-膨润土系竖向隔离墙广泛应用于工业污染场地和地下水修复工程。通过坍落度和一维压缩固结试验研究添加沸石对黏性土-膨润土竖向隔离墙材料的工作性,以及压缩和渗透特性。黏性土选用高岭土,沸石-高岭土-膨润土试样中沸石掺量为2%～40%。试验结果与以往沸石-砂-膨润土竖向隔离墙材料以及击实沸石-膨润土混合土研究结果进行对比,明确沸石掺量和粒径对压缩和渗透特性的作用规律。试验结果显示,满足隔离墙材料施工要求的含水率范围随沸石掺量增加而增大,并处于液限的0.96～1.18倍。添加细颗粒沸石对试样的压缩指数和渗透系数影响较小,渗透系数小于10-9 m/s。相反,添加粗颗粒沸石将导致微孔隙尺寸增大,并形成水能够通过的沸石网架结构,将显著增大渗透系数。试样渗透系数能够通过考虑孔隙比和液限的经验公式进行良好的预测。  相似文献   

10.
《Comptes Rendus Geoscience》2014,346(9-10):255-261
We studied the transport of a pesticide at field scale, namely carbofuran molecule, which is known for its high mobility, especially in sandy soils with high hydraulic conductivity and low organic matter. To add to our knowledge of the future of this high-mobility molecule in this type of soils, we developed a mechanistic numerical model allowing the simulation of hydric and solute transfers (bromide and carbofuran) in the soil. We carried out this study in an agricultural plot in the region of Mnasra in Morocco. Confrontation of the measured and simulated values allowed the calibration of the parameters of hydric transfer and carbofuran. The developed model accurately reproduces the measured values. Despite a weak irrigation and precipitation regime, carbofuran was practically leached beyond the root zone. Prospective simulations show that under a more important irrigation regime, carbofuran reaches a 100-cm depth, whereas it does not exceed 60 cm under a deficit regime.  相似文献   

11.
文章对西宁第四纪黄土-古土壤序列L9以来的黄土和古土壤层进行了土壤化学分析,揭示出剖面中含有大量的可溶盐。古土壤层中的可溶盐含量远高于黄土层,且二者所含可溶盐类型的相对比例存在明显差异。黄土层中Na2CO3和NaHCO3的相对比例较高,表现出更多的碱化特性,而古土壤中含有较多的NaCl和Na2SO4,表现出更多的盐化特性。从剖面所处的地貌-水文条件及土壤微形态特征来看,这些可溶盐主要来自大气降尘。研究揭示,约900ka以来,该区周边地区一直存在较多的干盐湖,是形成粉尘物质的重要源区之一,且间冰期粉尘比冰期粉尘可溶盐含量高得多。这些粉尘中含有较多的、包括对气候有影响的硫酸盐在内的可溶盐类。  相似文献   

12.
以现有的4种土壤转换函数(Pedotransfer Functions, PTFs)(包括ROSETTA、RAWLS、CAMPBELL和VAUCLIN)为例,将其用于土壤水力性质数据库UNSODA中56个典型砂土样本的非饱和导水率预测,对4种PTFs的预测结果进行了误差分析,探讨了饱和导水率对非饱和导水率预测的影响。结果表明,当同种PTFs预测的饱和导水率作为输入时,在4种PTFs中VAUCLIN的预测精度最高,其次为ROSETTA和RAWLS,CAMPBELL的误差最大;当实测饱和导水率作为输入时,RAWLS、CAMPBELL和ROSETTA的预测精度有了不同程度提高,但VAUCLIN的预测误差反而有所增大;饱和导水率对非饱和导水率预测的影响较大,实测饱和导水率作为输入时CAMPBELL预测的非饱和导水率与实测值最为接近。  相似文献   

13.
采用间歇灌溉进行土壤盐分淋洗的适用性   总被引：1，自引：0，他引：1       下载免费PDF全文
为比较一次性灌溉和间歇灌溉在盐分淋洗效率方面的优劣,采用HYDRUS-1D两区模型模拟分析了不同频次灌溉条件下的土壤水盐运移过程。结果表明存在一个间歇灌溉具有更高淋洗效率的最大深度,并将其称为临界深度。对砂土的模拟显示在灌水总量为20 cm时,随着潜在蒸发强度从0 mm/d升高至6 mm/d,临界深度从60 cm以上降为0 cm;而在潜在蒸发强度为2 mm/d时,随着灌水总量从10 cm增加至40 cm,临界深度相应从20 cm增加至接近80 cm。比较而言,透水性好、不动水体占比高、两部分孔隙之间水分和溶质交换能力差的土壤,临界深度更大;对黏土、黏壤土、壤土、砂壤土和砂土分别进行模拟显示偏砂性土壤具有更大的临界深度,在灌水总量和潜在蒸发强度分别为30 cm和2 mm/d时,黏土和砂土的临界深度分别为56 cm和大于100 cm。总的来看,对于间歇灌溉是否能提高盐分淋洗效率不能一概而论,引入临界深度可以在一定程度上解释研究者们对于间歇灌溉是否能提高盐分淋洗效率的不同认识。  相似文献   

14.
Irrigated agriculture allows for the increase of agrarian yields and stability in food supply and raw materials, being, at the same time, responsible for the reduction of water resources availability and for the pollution by salts and nitrate. This work aims to analyze the impact of changes in irrigation management (establishment of an on-demand flood irrigated system, assignment of irrigation allowances and water payment for surface and irrigation water consumption) in a traditional irrigated land on drainage flow, electrical conductivity and nitrate concentration in irrigation return flows between the year 2001 and the period 2005–2008. Changes in water management significantly modified quantity (lower drainage) and quality (electrical conductivity and nitrate) of irrigation return flows, keeping similar evolution paths during the year with water ameliorants in summer due to the use of good irrigation water quality. Salinity in irrigation return flows is not a current problem in the area as electrical conductivity values in water did not exceed the limit established for water used in irrigation or intended for human consumption. Despite the fact that changes in irrigation management and crop distribution have reduced nitrate concentrations in irrigation return flows by 43 %, the water still presents nitrate values exceeding the 50 mg NO3 ?/l. Thus, nitrate remains as the main agro-environmental problem in this irrigation area. However, the nitrate concentration trends detected in this work mark the possibility of reaching nitrate values below 50 mg NO3 ?/l in the case of maintenance of the conditions in this agricultural system.  相似文献   

15.
Heavy grazing is recognized as one of the main causes of vegetation and soil degradation and desertification in the semiarid Horqin sandy grassland of northern China. Soil physical and chemical properties were examined under continuous grazing and exclusion of livestock for 8 years in a representative desertified sandy grassland. Exclosure increased the mean soil organic C, total N, fine sand and silt + clay contents, inorganic C (CaCO3), electrical conductivity, and mineral contents (including Al2O3, K2O, Na2O, Fe2O3, CaO, MgO, TiO2, MnO), microelements (Fe, Mn, Zn, B, Cu, Mo), and heavy metals (Pb, Cr, Ni, As, Hg, Cd, Se), and decreased the coarse sand content, bulk density, and SiO2 in the top 100 cm of the soil. Livestock exclusion also improved available N, P, K, Fe, Mn, and Cu, exchangeable K+, and the cation exchange capacity, but decreased pH, exchangeable Na+, and available S, Zn, and Mo in the top 20 cm of the soil. The greatest change in soil properties was observed in the topsoil. The results confirm that the desertified grassland is recovering after removal of the livestock disturbance, but that recovery is a slow process.  相似文献   

16.
Spatial distribution of the salinity in groundwater used for irrigation and irrigated soil was investigated on Gammouda Plain, an important agricultural area in central Tunisia. Samples from 188 wells and irrigated fields were obtained in November 1988. Groundwater salinity ranges from 2 to 30 dS/m, and 50 percent of the sampled wells have a salinity higher than 3.5 dS/m. In most cases the soil samples have a salinity higher than 4 dS/m. Maps of salinity and leaching were produced by a geostatistical interpolation method based on ordinary kriging. In a great part of the plain, the estimated salinity levels indicate that there is a considerable risk for reduced yield potential for several of the most important crops grown. A rough estimation of the leaching fraction was computed from the soil and water salinity. Computer-based models of salinity ought to facilitate the general planning of irrigation management and crop selection.  相似文献   

17.
Monitoring general variability of soil attributes is a fundamental requirement from the point of view of understanding and predicting how ecosystems yield. In order to monitor impact of different land use types on the combination of morphological, clay mineralogical and physicochemical characterizes, 42 soil samples (0–30 cm) were described and analyzed. Soil samples belonging to Cambisols and Vertisols reference soil groups collected from three neighboring land use types included cropland (under long-term continuous cultivation), grassland, and forestland. The soils were characterized by high pH (mean of 7.1–7.5) and calcium carbonate equivalent (CCE) (mean of 35–97 g kg?1) in the three land use types. The weakening in soil structure, hardening of consistency, and lighting of soil color occurred for the cropland under comparable condition with grassland and forest. Changes in land use types produced a remarkable change in the XRD patterns of clay minerals containing illite and smectite due the dynamic and removal of potassium. Continuous cultivation resulted in an increase in sand content up to 35 % while silt and clay content decreased up to 22 and 18 %, respectively, as compared to the adjoining grassland and forest mainly as a result of the difference of dynamic alterational and erosional process in the different land use. Long-term cultivation caused a negative and degradative aspects on soil heath as is manifested by the increasing in soil pH (a rise of 0.3–0.46 unit), electrical conductivity (EC) (a rise of 1.78–5.5 times), sodium absorption ration (SAR) (a rise of 10–51 %), exchangeable sodium percentage (ESP) (a rise of 3–46 %), and the decrease in soil organic C (a drop of 12–41 %), along with soil fertility attributes. Overall, the general distribution of soil organic C, total N, available P and K, cation exchange capacity (CEC), and exchangeable cations (Ca, Mg, and K) followed the order: forestland > grassland > cropland. The general distribution of EC, SAR, ESP, and exchangeable Na, however, followed the order: cropland > grassland > forestland. Soil quality index (SQI), calculated based on some physicochemical properties, specified that cultivation led to a negative effect in SQI for both Cambisols (a drop of 10–17 %) and Vertisols (a drop of 17 %) as compared to those of under grassland and forestland.  相似文献   

18.
目前对影响土壤饱和渗透系数规律的机理缺乏深刻认识.以不同沉积环境、不同岩性及不同土地利用方式的江汉平原汉江下游浅层土壤为对象,采用改进的TST-55型土壤渗透仪开展室内变水头达西实验.结果表明,研究区内土壤饱和渗透系数平均值为4.94×10-5cm/s,服从对数-正态分布;粉砂壤土冲积物和湖积物的饱和渗透系数平均值为3.53×10-5cm/s和1.98×10-5cm/s,粉砂质粘壤土中,两者分别为8.13×10-7cm/s和5.88×10-7cm/s,同一岩性冲积物的饱和渗透系数较湖积物大;冲积物中,砂壤土、粉砂壤土和粉砂质粘壤土饱和渗透系数平均值为1.98×10-5 cm/s、3.53×10-5 cm/s和8.13×10-7 cm/s,表现为砂壤土>粉砂壤土>粉砂质粘壤土;耕作土壤中,粉砂壤土、粉砂质粘壤土的饱和渗透系数平均值为3.75×10-5 cm/s和8.11×10-7cm/s,非耕作土壤中,两者分别为1.88×10-6cm/s、5.93×10-7cm/s,同一岩性耕作土壤饱和渗透系数较非耕作土壤大.   相似文献   

19.
The reuse of nutrients and organic matter in wastewater sludge via on agricultural lands application is a desirable goal. However, trace or heavy metals present in sludge pose the risk of human or phytotoxicity from land application. The aim of this research is possibility of ground water pollution of south of Tehran because of ten years irrigation with Ni, Cd and Pb borne waste water. For this purpose, 6 soil samples from southern parts of Tehran city and 2 ones from Zanjan city without lime and organic matter were selected. The soils differed in their texture from sandy to clayey. Each soil sample in duplicate and uniformly packed into PVC columns. Soil samples were irrigated with Cd, Pb and Ni-added wastewater. After irrigating, the columns were cut and the soils separated from sectioned pieces and their heavy metal concentrations (Pb, Cd and Ni) were measured by atomic absorption spectrophotometer by use of HNO3 4N solution. Because of high sorption capacity of these elements by soils, these metals were accumulated in surface layer of the soils. Movement in the soils without lime and organic matter were as low as other samples. Ni has had the most accumulation or the least vertical movement, and Pb the opposite ones.  相似文献   

20.
In order to understand the hydrothermal activity mechanism of active layers to rainfall in permafrost regions caused by humidification of climate, the differences of ground surface energy balance and hydrothermal activity in different types of shallow soil with the consideration of rainfall were discussed. Based on the meteorological data in 2013 observed at Beiluhe observation station of Tibet Plateau, three types of shallow ground soil (i.e., sandy soil, sandy loam and silty clay) were selected to compare the differences in the water content and energy balance at the ground surface, dynamic processes of water and energy transport in active layers and coupling mechanism under rainfall condition in the plateau using a coupled water-vapor-heat transport model. The results show that the increase of soil particle size leads to the increase of surface net radiation and latent heat of evaporation, but the decrease of soil heat flux. The difference of surface energy balance, especially the sensible heat flux and latent heat of evaporation, are larger in the warm season but smaller in the cold season. The liquid water transport under hydraulic gradient and the water-vapor transport under thermal gradient are obvious as the particle size in soil increases. However, the water-vapor flux under thermal gradient increases but the liquid water flux under hydraulic potential gradient decreases. As a result, the water content in shallow soil decreases accordingly but it increases slightly at the depth of 25 ~75 cm. Moreover, with the increase of soil particle size, the thermal conductivity of soil, convective heat transfer under rainfall and surface evaporation increase, but the soil heat conduction flux and soil temperature gradient decrease. Thus, soil temperature in sandy soil is much higher than that of sandy loam and silty clay at the same depth. The permafrost table declines with the increase of the thickness of active layer, which is unfavourable to permafrost stability. The results can provide theoretical reference for stability prediction and protection of permafrost caused by humidification of climate.  相似文献   

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