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1.
Soils and sediments around gold ore deposit and mining sites in the Iron Quadrangle present positive As anomalies (median concentrations > 100 mg kg-1) and wide ranges (< 20 to > 2000 mg kg-1) even in densely populated areas. These anomalies can be related to geological structures, to hydrothermal ore deposits and to their continuous exploitation over the past three centuries. The paper presents new data on both As geochemistry and soil and sediment geochemistry in general, and discusses consequences of the encountered anomalies, their reasons and potential effects and how they compare with current screening and threshold values. While surface soil As-values are reproducible at a given site, sediment anomalies show a strong seasonal variation that can be explained by tropical hydrological variances. Suggestions are presented on how to minimize the As-load in densely populated areas that might otherwise pose a potential health risk.  相似文献   

2.
Soils and sediments around gold ore deposit and mining sites in the Iron Quadrangle present positive As anomalies (median concentrations > 100 mg kg-1) and wide ranges (< 20 to > 2000 mg kg-1) even in densely populated areas. These anomalies can be related to geological structures, to hydrothermal ore deposits and to their continuous exploitation over the past three centuries. The paper presents new data on both As geochemistry and soil and sediment geochemistry in general, and discusses consequences of the encountered anomalies, their reasons and potential effects and how they compare with current screening and threshold values. While surface soil As-val-ues are reproducible at a given site, sediment anomalies show a strong seasonal variation that can be explained by tropical hydrologicai variances. Suggestions are presented on how to minimize the As-load in densely populated areas that might otherwise pose a potential health risk.  相似文献   

3.
This paper investigates the pollution load of selected trace elements in 32 soil samples collected around 21 different mining areas of the Iberian Pyrite Belt (Southwest Spain), integrating chemical data with soil parameters to help understand the partitioning and mobility of pollutants. The minesoils are depleted in acid neutralising minerals and show limiting physicochemical properties, including low pH values and very high anomalies of potentially hazardous metals. The total concentrations of As (up to 1,560 mg kg?1) and certain heavy metals (up to 2,874 mg kg?1 Cu, 6,500 mg kg?1 Pb, 6,890 mg kg?1 Zn, 62 mg kg?1 Hg and 22 mg kg?1 Cd) are two orders of magnitude above the soil background values. The close association of Cd and Zn with the carbonate content in lime-amended minesoils suggests metal immobilisation through adsorption and/or co-precipitation mechanisms, after acid neutralisation, whereas As and Pb are similarly partitioned into the soil and mostly associated with iron oxy-hydroxides.  相似文献   

4.
The environmental impact of arsenic and heavy metals on a 105 km2 area of the historical and recent mining site of Villa de la Paz-Matehuala, San Luis Potosí (Mexico) was evaluated. Results of soil samples reported concentrations between 19–17 384 mg kg-1 As, 15–7200 mg kg-1 Cu, 31–3450 mg kg-1 Pb and 26–6270 mg kg-1 Zn, meanwhile, the concentrations in dry stream sediment samples were found to vary between 29–28 600 mg kg-1 As, 50–2160 mg kg-1 Pb, 71–2190 mg kg-1 Cu, and 98–5940 mg kg-1 Zn. The maximum arsenic concentration in pluvial water storage ponds (265 μg L-1), near the main potential sources of pollution, exceed by 5 times the Mexican drinking water quality guideline (50 μg L-1). The arsenic concentrations in water storage ponds and stream sediments decrease as distance from the potential sources increase. A special case is the `Cerrito Blanco' area located 5 km east of Matehuala, where the highest arsenic concentration in water was found (>5900 μg L-1), exceeding by 100 times the established guideline, thus representing a severe health risk. The results suggest that arsenic and heavy metal dispersion from their pollution sources (historical and active tailings impoundments, waste rock dumps and historical slag piles), is mainly associated in this site with: (1) fluvial transportation of mine waste through streams that cross the area in W–E direction; and (2) aeolian transportation of mineral particles in SW–NE direction. Finally, control measures for pollution routes and remediation measures of the site are proposed.  相似文献   

5.
Agrichemical spills and discharges to soil can cause point-source contamination of surface and ground waters. When high contaminant concentrations inhibit natural attenuation in soils, chemical treatments can be used to promote degradation and allow application of treated soils to agricultural lands. This approach was used to remediate soil containing >650 mg atrazine, >170 mg metolachlor and >18,000 mg nitrate kg?1. Results indicated a decrease in metolachlor concentration to <1 mg kg?1 within 95 days of chemical treatment with zerovalent iron (Fe0, 5% w/w) and aluminum sulfate (Al2(SO4)3, 2% w/w) but after one year >150 mg atrazine and >7000 mg nitrate kg?1 remained. Laboratory experiments confirmed that subsequent additions of sucrose (table sugar) to the chemically pretreated soil promoted further reductions in atrazine and nitrate concentrations. Field-scale results showed that adding 5% (w/w) sucrose to windrowed and pretreated soil significantly reduced atrazine (<38 mg kg?1) and nitrate (<2,100 mg kg?1) concentrations and allowed for land application of the treated soil. These results provide evidence that zerovalent iron in combination with Al2(SO4)3 and sucrose can be used for on-site, field-scale treatment of pesticide- and nitrate-contaminated soil.  相似文献   

6.
砂质土壤积累的铜和锌的可提取性与移动性研究   总被引：7，自引：0，他引：7  
An investigation was conducted to study problems of determining a reasonable percentage for ecological water-use in the Haihe River Basin of China. Three key aspects for the ecological water requirement （EWR） were analyzed, involving i） the EWR for river system, ii） the EWR for wetlands and lakes, and iii） the EWR for discharge into the sea to maintain the estuary ecological balance of the Haihe River. The Montana method and related water level-flow relationships, and the statistic approach based on hydrological records were applied to estimate different components of EWR. The results showed that the total ecological water demand in the region, was about 3.47-14.56 billion m^3. Considering flow regime change and uncertainty, the ecological water demand could be estimated by the hydrological frequency approach. Preliminary analysis showed that for different annual runoff under the frequencies of 20%, 50%, 75% and 95%, the ecological water demand approached 12%-50%, 18%-74%, 24%-103%, 35%-148% and 16%-66%, respectively. By further analysis to balance ecological water-use and socioeconomic water-use, the rational percentage of ecological water-use was estimated as 35%-74%, that provides useful information to judge whether the allocation of water resources is reasonable, and was proved to be satisfactory by comparing with the practical condition.  相似文献   

7.
Soil arsenic (As) pollution from mining and industrial sources is a serious issue in China. Earthworms are considered ecosystem engineers and contribute to soil fertility development and maintenance of soil physico-chemical properties. In this study, earthworms were exposed to soils with different sodium arsenite concentrations (0, 5, 20, and 80 mg As kg-1) for 60 d to investigate the changes in soil properties and the responses of the earthworms (e.g., burrowing activity and respiration). Earthworm burrowing activity decreased with increasing arsenite concentrations, and earthworm respiration was significantly lower in soils with 20 and 80 mg As kg-1 compared to 0 mg As kg-1. Changes in soil properties were also observed after incubation of As-amended soil with earthworms. Specifically, soil pH decreased, while soil electrical conductivity and contents of soil NH3--N, Olsen-P, and available K increased. Our results suggest that arsenite negatively impacts the metabolic activity of earthworms, leading to reduced burrowing activity, which in turn modifies the effects of earthworms on soil fertility and remediation.  相似文献   

8.
 This study focuses on a comparison of the microbial toxicity of nine metals, including As as a metalloid and two species of Cr. A loess soil [Ap horizon, clay 15.2%, organic C 1.12%, pH(CaCl2) 7.02] was spiked with 8–12 geometrically increasing doses of the metals. The dehydrogenase assay (2-p-iodophenyl-3-p-nitrophenyl-5-phenyltetrazoliumchloride method) was combined with sorption and solubility experiments. The resulting dose-response curves and sorption isotherms were used to derive total doses that caused definite percentage inhibitions [i.e. effective doses (ED) causing a 10–90% reduction in dehydrogenase activity (dha)] as well as the corresponding toxic solution concentrations causing the same reductions in dha (i.e. effective concentrations; EC10–EC90). Based on total doses, the toxicity decreased in the following order with ED50 values (mg kg–1) given in brackets: Hg (2.0)>Cu (35)>Cr(VI) (71)>Cr(III) (75)>Cd (90)>Ni (100)>Zn (115)>As (168)>Co (582)>Pb (652). With regard to solution concentrations, toxicity decreased in the order (EC50 in mg l–1): Hg (0.003)>Pb (0.04)>Cu (0.05)>Cd (0.14)>Zn (0.19)>Cr(III) (0.62)>Ni (0.69)>Co (30.6)>As (55.5)>Cr(VI) (78.1). The retention of the metals by the soil differed strongly. Pb, Cu, and Hg exhibited the highest and Ni, As, and Cr(VI) the lowest sorption constants (Freundlich K values: 2455, 724, 348, 93, 13, and 0.06 mg kg–1, respectively). The sorptivity of the metals and their microbial toxicity in the aqueous phase were characteristically related: metals with a strong toxic action in the soil solution were adsorbed by the soil to a high degree and vice versa. Therefore, especially for metals with a high inherent toxicity, sorption is an effective way of immobilizing them and temporarily detoxifying soil. Received: 2 July 1998  相似文献   

9.
This study evaluated the effect of competing copper, zinc, cadmium and nickel ions in 0.01 M Ca(NO3)2 on heavy metal sorption and desorption by soil clay fractions. Initial Cu addition levels varied from 99 mg kg-1 to 900 mg kg-1 and Zn, Cd and Ni levels were 94, 131 and 99 mg kg-1, respectively. Sorption of Cu conformed to a Freundlich equation. The amounts of metals not displaced by successive 48 h desorption cycles with 0.01 M Ca(NO3)2 were considered ‘specifically adsorbed’. Total sorption of Zn and Cd generally decreased in the order: Vertisol > Gleyic Acrisol > Planosol clay. More than 70% of the copper was specifically sorbed. Specific sorption of Zn was depressed by competition with Cu in the three clays investigated. At surface coverages higher than 200 mg Cu per kg of soil clay, zinc sorption in the Planosol and Gleyic Acrisol clays took place at low affinity sites. The exchangeable component of sorbed cadmium accounted for >:60% of the sorption in the Vertisol clay, >70% in the Gleyic Acrisol clay and was almost 100% in the Planosol clay. Nickel was not retained by the Planosol and Gleyic Acrisol clays and was ionexchangeably adsorbed by the Vertisol clay. At the conditions studied, Ni and Cd remain a ready source of pollution hazard.  相似文献   

10.
The study of the soil properties and geochemistry of vineyard soils of the Méntrida Protected Designation of Origin (PDO) (central Spain) was performed to better understand the role of soil as a terroir component and to contribute to sustainable vineyard management. Soil physico-chemical characteristics were determined, along with the content of trace elements (by placing emphasis on rare earths) in topsoils and subsoils. The dominant soil types were Inceptisols, Alfisols and Entisols (USDA soil classificacion), i.e., Cambisols, Luvisols and Regosols in the World Reference Base for Soil Resources (WRB) system. They were all deep and well-structured. Our findings reveal that soil-available nitrogen (N) ranged from 0.03 to 0.21 (%), with soil-available phosphorus (P) ranging from 0.20 to 40.50 (mg·kg−1). pH had a mean of 6.33 (range: 4.4–8.7) in the ten observations, and a degree of mesotrophic saturation in bases (V%), except in one that had a 100% value (soils where carbonates were absent, save exceptional cases). A medium to high cation exchange capacity (CEC) was found (range: 9.8–38.3 cmol·kg−1). The mean values of elements' contents were (mg·kg−1): Sc 14.8, V 32.13, Cr 23.09, As 4.01, Ni 8.57, Cu 6.43, Zn 30.13, Rb 143.49, Sr 63.03, Y 15.39, Ba 374,44, La 25.87, Ce 43.77, Pb 22.25, Nd 21.28. They decreased in this order: Ba > Rb > Sr > Ce > V > Zn > La > Cr > Pb > Nd > Y > Sc > Cu > As. The results confirm the importance of soils for the PDO, with an optimum condition to produce grapevine quality laying the foundations to obtain a good wine. Our findings provide insights into the importance of pedological properties for regulating soil nutrient availability across soil types, and support soil resource utilization management in regional viticulture.  相似文献   

11.
A sensitivity-resistance index was developed, and proved to be a very sensitive biomonitor of soil pollution with heavy metals. The index was developed by a step-by-step approach. Ultimately, the bacterial soil microflora was divided into three groups, senstivive, tolerant, and resistant microflora. Zn and Cd sensitivity was defined as no growth occurring in the presence of 5 and 0.5 mg l-1 of these metals, respectively, while resistance was defined as distinct growth in the presence of 50 and 16 mg l-1, respectively. The sensitivity: resistance ratio of a referent clay soil (0.57 mg Cd kg-1 and 140 mg Zn kg-1) was 0.53, but for polluted (6 mg Cd kg-1 + 670 mg Zn kg-1) clay soil, the ratio was 0.24. For a referent (0.06 mg Cd kg-1 + 12 mg Zn kg-1) sandy soil the sensitivity: resistance ratio was 1.50 whereas polluted (2.3 mg Cd kg-1 + 252 mg Zn kg-1) sandy soil had a ratio 0.19. The ecological value of the sensitivity-resistance lies in its capacity to reflect potential deradation of aromatic compounds. It has been shown repeatedly that sensitive bacteria grow significantly better on a range of selected aromatic compounds. It has been speculated that resistance fo heavy metals may reduce the bioremediation capacity of soil towards chlorinated aromatics and polyaromatic hydrocarbons.  相似文献   

12.
水稻品种和砷污染对土壤溶解性有机碳氮的影响   总被引：2，自引：0，他引：2  
选取有机质含量和pH不同的2种水稻土(黄泥田和红泥田),通过盆栽实验研究砷(As)污染条件下,种植9个水稻品种对土壤溶解性有机碳(DOC)和溶解性有机氮(DON)含量的影响,分析水稻品种、As污染和土壤类型的相对影响与交互作用.结果表明,水稻品种显著影响了土壤DOC和DON的变化,在水稻收获后,DOC平均含量的大小顺序为杂交稻(41.09±0.92 mg kg-1)＞籼稻(38.10±1.53 mg kg-1)＞粳稻(37.74± 1.37 mg kg-1);DON平均含量的大小顺序为粳稻(2.94± 0.40 mg kg-1)＞杂交稻(2.61±0.42 mg kg-1)＞籼稻(1.45± 0.17 mg kg-1).As污染降低了土壤DOC和DON的含量,但不同品种水稻的响应不同.与对照相比,As污染条件下,黄泥田和红泥田中DOC平均含量分别下降了14.4％和11.1％,DON平均含量分别下降了65.0％和44.7％;DOC在种植杂交稻后降幅最小,而DON在种植籼稻后降幅最小.在两种水稻土中,黄泥田的DOC和DON平均含量高于红泥田,在没有As污染条件下,分别高22.4％和45.8％,这与黄泥田有机质含量和pH高有关.水稻品种、As污染和土壤类型对DOC和DON变化的影响不同,3个因子对DOC变化的相对贡献率分别为7.7％、15.5％和27.6％,对DON变化的相对贡献率分别为14.7％、24.2％和2.0％.  相似文献   

13.
Land pollution due to past mining activities is a major environmental issue in many European countries. The Aljustrel mine (SW Portugal), located in the western sector of the Iberian Pyrite Belt (IBP) presents a negative visual and environmental impact as a consequence of the mining activity that has developed since the Roman era. Its impacts are also a restraint on the life quality of the population. The exposure of pyrite and other sulphides to air are responsible for the pollution observed in soils, surface water and stream sediments. This paper investigates the pollution load of potential toxic elements in soil samples collected around the Aljustrel mining area. The aim is to assess the levels of soil contamination with respect to average concentrations of toxic elements in the region and to understand the partitioning and availability of pollutants in the area. The results showed severe soil contamination (mainly As, Cd, Cu, Pb and Zn). The concentrations of As (up to 3936 mg kg−1) and certain heavy metals (up to 5414 mg kg−1 Cu, 61·6 mg kg−1 Cd, 20 000 mg kg−1 Pb and 20 000 mg kg−1 Zn) are two orders of magnitude above the regional South Portuguese Zone (SPZ) background values. The median concentrations of As, Cd, Cu, Pb and Zn exceed the values established for world soils, the European Union, Portugal and Andalusia. The results suggest that the distribution patterns of Co, Cr and Ni element concentrations in the Aljustrel area are primarily influenced by the lithology and geochemistry nature of bedrock. The soil background of this geological domain is characterized by relatively high heavy metal contents, essentially derived from the parent rocks. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

14.
Foliar Cd and Zn concentrations in Salix, Populus and Zea mays grown on freshwater tidal marshes were assessed. Soil metal concentrations were elevated, averaging 9.7 mg Cd kg?1 dry soil, 1100 mg Zn kg?1 dry soil and 152 mg Cr kg?1 dry soil. Cd (1.1–13.7 mg kg?1) and Zn (192–1140 mg kg?1) concentrations in willows and poplars were markedly higher than in maize on impoldered tidal marshes (0.8–4.8 mg Cd kg?1 and 155–255 mg Zn kg?1). Foliar samples of maize were collected on 90 plots on alluvial and sediment‐derived soils with variable degree of soil pollution. For soil Cd concentrations exceeding 7 mg Cd kg?1 dry soil, there was a 50% probability that maize leaf concentrations exceeded public health standards for animal fodder. It was shown that analysis of foliar samples of maize taken in August can be used to predict foliar metal concentrations at harvest. These findings can therefore contribute to anticipating potential hazards arising from maize cultivation on soils with elevated metal contents.  相似文献   

15.
Sánchez  J.  Marino  N.  Vaquero  M. C.  Ansorena  J.  Legórburu  I. 《Water, air, and soil pollution》1998,107(1-4):303-319
Soil, aquatic biota (moss: Brachythecium rivulare; aquatic macrophytes: Juncus effusus, Potamogeton crispus; fish: Salmo trutta fario, Anguilla anguilla, Phoxinus phoxinus, Chelon labrosus) and sediment samples from the Urumea river valley were analysed for metals by acid digestion and atomic absorption spectroscopy. The sediments show the presence of metal pollution (Cd: 2.5–24 mg kg-1; Pb: 125–1,150 mg kg-1; Zn: 125–2,500 mg kg-1) because mining and industrial wastes. A selective retention of dense minerals in dam sediments contributes to the load of metal, but interstitial water analysis (Cd: <0.02–0.1 mg L-1; Pb: 0.3–1.0 mg L-1; Zn: <0.05–0.6 mg L-1) shows that precipitation equilibrium controls their mobilisation. Biota samples show evidence of metal accumulation, moss reaching 1,100 mg kg-1 in lead and 6,800 mg kg-1 in zinc. Soil from the valley is polluted by both, river carried material and industrial sources (Cd: 1.0–4.0 mg kg-1; Pb: 26–1,120 mg kg-1; Zn: 105–1,390 mg kg-1/math>), but they are used, indistinctly, for farming and pasture.  相似文献   

16.
小麦/玉米/大豆带状套作是四川省丘陵低山区主要旱地作物生产体系,了解该体系磷养分变化对优化磷肥管理和促进可持续生产有重要意义。本研究通过连续3年(2011—2013年)田间定位试验,设置P0、P1、P2、P3和P4共5个磷(P2O5)水平(玉米带分别为0 kg·hm-2、37.5 kg·hm-2、75 kg·hm-2、112.5 kg·hm-2、150 kg·hm-2,小麦-大豆带分别为0 kg·hm-2、45 kg·hm-2、90 kg·hm-2、135 kg·hm-2、180 kg·hm-2),探讨该体系中土壤全磷、速效磷、水溶性磷的变化规律和速效磷的年际变化。结果表明:在麦/玉/豆套作体系中施磷165 kg(P2O5)·hm-2(玉米带75 kg·hm-2,小麦-大豆带90 kg·hm-2),可以满足体系作物对磷的需求,基本达到磷的表观平衡,维持土壤速效磷含量在20 mg·kg-1左右。3年后5个磷水平下体系耕层土壤(0~20 cm)全磷变化量分别为-0.024 g·kg-1·a-1、-0.016 g·kg-1·a-1、0.016 g·kg-1·a-1、0.11 g·kg-1·a-1、0.15 g·kg-1·a-1,速效磷变化量依次为-1.2 mg·kg-1·a-1、-0.9 mg·kg-1·a-1、0.2 mg·kg-1·a-1、2.0 mg·kg-1·a-1和2.7 mg·kg-1·a-1。通过线性平台函数的模拟,该体系中玉米、小麦、大豆产量的土壤速效磷临界值分别为16.5 mg·kg-1、12.6 mg·kg-1和8.8 mg·kg-1。当土壤全磷含量低于0.55 g·kg-1时,土壤全磷每增加0.1 g·kg-1,土壤速效磷增加1.70 mg·kg-1;当土壤全磷大于0.55 g·kg-1,全磷每增加0.1 g·kg-1,土壤速效磷增加6.49 mg·kg-1。当土壤速效磷含量在40 mg·kg-1以下时,速效磷每增加1 mg·kg-1,水溶性磷增加0.017 mg·kg-1。综上,在麦/玉/豆体系磷肥管理中应该维持土壤全磷含量低于0.55 g·kg-1,同时速效磷含量在20 mg·kg-1左右,这样既可以保证作物产量和系统生产力又不会产生较大的环境威胁。  相似文献   

17.
A 12-week incubation experiment was conducted to determine the pattern and rate of N mineralized from organic materials. Treatments consisted of sheep manure (SM), cattle manure (CM), poultry manure (PM), sewage sludge (SS) at 1% (W/W) level, and unfertilized treatment with three replications. The concentrations of nitrate (NO3)- nitrogen (N) and ammonium (NH4)-N were determined in day 1 and 1, 2, 4, 8, and 12 weeks after the beginning of incubation. Results indicated that the magnitude of N mineralized during the incubation time periods was in the order of CM (134 mg kg?1) > PM (83 mg kg?1) > SS (56 mg kg?1) > SM (55 mg kg?1), and different management is required for obtaining optimum N-use efficiency. In conclusion, improving N-uptake efficiency in manure- and SS-amended soils depends on the pattern and rate of N mineralization to synchronize N released with crop N demand periods.  相似文献   

18.
The To Lich and Kim Nguu Rivers, laden with untreated waste from industrial sources, serve as sources of water for irrigating vegetable farms. The purposes of this study were to identify the impact of wastewater irrigation on the level of heavy metals in the soils and vegetables and to predict their potential mobility and bioavailability. Soil samples were collected from different distances from the canal. The average concentrations of the heavy metals in the soil were in the order zinc (Zn; 204 mg kg?1) > copper (Cu; 196 mg kg?1) > chromium (Cr; 175 mg kg?1) > lead (Pb; 131 mg kg?1) > nickel (Ni; 60 mg kg?1) > cadmium (Cd; 4 mg kg?1). The concentrations of all heavy metals in the study site were much greater than the background level in that area and exceeded the permissible levels of the Vietnamese standards for Cd, Cu, and Pb. The concentrations of Zn, Ni, and Pb in the surface soil decreased with distance from the canal. The results of selective sequential extraction indicated that dominant fractions were oxide, organic, and residual for Ni, Pb, and Zn; organic and oxide for Cr; oxide for Cd; and organic for Cu. Leaching tests for water and acid indicated that the ratio of leached metal concentration to total metal concentration in the soil decreased in the order of Cd > Ni > Cr > Pb > Cu > Zn and in the order of Cd > Ni > Cr > Zn > Cu > Pb for the ethylenediaminetetraaceitc acid (EDTA) treatment. The EDTA treatment gave greater leachability than other treatments for most metal types. By leaching with water and acid, all heavy metals were fully released from the exchangeable fraction, and some heavy metals were fully released from carbonate and oxide fractions. The concentrations of Cd, Cr, Cu, Ni, Pb, and Zn in the vegetables exceeded the Vietnamese standards. The transfer coefficients for the metals were in the order of Zn > Ni > Cu > Cd = Cr > Pb.  相似文献   

19.
Contamination of grazed pasture gave 0–5 cm soil contents of 19–835 mg kg-1 Cu, 47–739 mg kg-1 Cr, and 12–790 mg kg-1 As. Soil Cu, Cr, As contents were correlated and declined with depth to 30 cm. In plots with medium and high contamination buried cotton strips retained most of their original tensile strength, indicating repression of decomposition processes.Lumbricus rubellus andAporrectodea rosea were absent in plots with medium and high contamination; there was no evidence of heavy metal accumulation in earthworm tissue; soil bulk density was greater in the absence of lumbricids. Enchytraeids and nematodes were most abundant with low contamination. Nematode diversity was greater with low (0–5 cm) or medium (5–10 cm) contamination than in control plots or those with high contamination; the proportion of predators increased with contamination. Basal soil respiration was less sensitive than substrate-induced respiration to contamination. Although contamination reduced the nitrification rate, all mineral N was found as NO inf3 sup- after 14 days. Sulphatase was the enzyme activity most sensitive to high contamination. Whereas contamination by 100 mg kg-1 of Cu, Cr, and As caused little depression of soil biological activity, there was some supperssion at 400 mg kg-1 and at 800 mg kg-1 normal processes were inhibited and herbage production was negligible. No single measurement adequately indicated the need for site remediation.  相似文献   

20.
Flooding an extremely alkaline（pH 10.6） saline soil of the former Lake Texcoco to reduce salinity will affect the soil carbon（C）and nitrogen（N） dynamics.A laboratory incubation experiment was done to investigate how decreasing soil salt content affected dynamics of C and N in an extremely alkaline saline soil.Sieved soil with electrical conductivity（EC） of 59.2 dS m-1 was packed in columns,and then flooded with tap water,drained freely and conditioned aerobically at 50%water holding capacity for a month.This process of flooding-drainage-conditioning was repeated eight times.The original soil and the soil that had undergone one,two,four and eight flooding-drainage-conditioning cycles were amended with 1000 mg glucose-14C kg-1 soil and 200 mg NH4+-N kg-1soil,and then incubated for 28 d.The CO2 emissions,soil microbial biomass,and soil ammonium（NE4+）,nitrite（NO2-） and nitrate（NO3-） were monitored in the aerobic incubation of 28 d.The soil EC decreased from 59.2 to 1.0 dS m1 after eight floodings,and soil pH decreased from 10.6 to 9.6.Of the added 14C-labelled glucose,only 8%was mineralized in the original soil,while 24%in the soil flooded eight times during the 28-d incubation.The priming effect was on average 278 mg C kg-1 soil after the 28-d incubation.Soil microbial biomass C(mean 66 mg C kg-1 soil) did not change with flooding times in the unamended soil,and increased 1.4 times in the glucose-NH4+-amended soil.Ammonium immobilization and NO2- concentration in the aerobically incubated soil decreased with increasing flooding times,while NO3- concentration increased.It was found that flooding the Texcoco soil decreased the EC sharply,increased mineralization of glucose,stimulated nitrification,and reduced immobilization of inorganic N,but did not affect soil microbial biomass C.  相似文献   

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