巴西东北部地区土地退化对土壤微生物量和活性的影响

Land degradation causes great changes in the soil biological properties.The process of degradation may decrease soil microbial biomass and consequently decrease soil microbial activity.The study was conducted out during 2009 and 2010 at the four sites of land under native vegetation(NV),moderately degraded land(LDL),highly degraded land(HDL) and land under restoration for four years(RL) to evaluate changes in soil microbial biomass and activity in lands with different degradation levels in comparison with both land under native vegetation and land under restoration in Northeast Brazil.Soil samples were collected at 0-10 cm depth.Soil organic carbon(SOC),soil microbial biomass C(MBC) and N(MBN),soil respiration(SR),and hydrolysis of fluorescein diacetate(FDA) and dehydrogenase(DHA) activities were analyzed.After two years of evaluation,soil MBC,MBN,FDA and DHA had higher values in the NV,followed by the RL.The decreases of soil microbial biomass and enzyme activities in the degraded lands were approximately 8-10 times as large as those found in the NV.However,after land restoration,the MBC and MBN increased approximately 5-fold and 2-fold,respectively,compared with the HDL.The results showed that land degradation produced a strong decrease in soil microbial biomass.However,land restoration may promote short-and long-term increases in soil microbial biomass.     

Changes in soil free-living diazotrophic community and co-occurrence patterns along desert wetland degradation gradient in the Mu Us Desert, northern China

Climate change and human activity have led to the degradation of desert wetlands. Free-living diazotrophs are vital for soil nitrogen input. However, a comprehensive understanding of how soil free-living diazotrophic communities and their co-occurrence patterns respond to desert wetland degradation is lacking. Here, quantitative polymerase chain reaction (qPCR), amplicon sequencing targeting nitrogenase gene (nifH), and network analysis were used to investigate the abundance, diversity, community composition, and co-occurrence patterns of soil free-living diazotrophs along the wetland degradation gradient, i.e., non-degraded (ND), lightly degraded (LD), moderately degraded (MD), and severely degraded (SD), in the southeastern Mu Us Desert, northern China. The abundance and Shannon, Simpson, Chao 1, and ACE indexes decreased (P < 0.05) by 14.6%, 20.7%, 2.1%, 46.5%, and 45.0%, respectively, in SD wetland, whereas no significant difference (P > 0.05) was observed between ND and LD wetlands. The relative abundance of Proteobacteria generally decreased (by 53.5%–19.7%) across the different degradation levels, while the relative abundance of Cyanobacteria increased (by 6.2%–40.1%) from ND to MD levels. The abundance, diversity, and community composition of diazotrophs were most strongly related to soil organic carbon, followed by total nitrogen, moisture, and pH. The least number of network nodes and edges and the lowest density were observed for MD and SD wetlands, indicating that the complexity of free-living diazotrophic networks was reduced by continued degeneration. Overall, severe desert wetland degradation affected the abundance, diversity, and network complexity of soil free-living diazotrophs more negatively than light degradation. This degradation promoted the growth of autotrophic diazotrophs and inhibited the growth of heterotrophic diazotrophs. These changes were mostly related to the loss of soil organic carbon.     

从土壤中分离获得的五氯硝基苯降解菌株降解五氯硝基苯特性研究

A bacterial strain,pcnb-21,capable of degrading pentachloronitrobenzene(PCNB) under aerobic and anoxic conditions,was isolated from a long-term PCNB-polluted soil by an enrichment culture technique and identified as Labrys portucalensis based upon its morphological,physiological and biochemical properties,as well as 16S rRNA gene sequence analysis.Effects of different factors,such as temperature and pH,on PCNB biodegradation were studied.Strain pcnb-21 efficiently degraded PCNB at temperatures from 20 to 30 ℃ and initial pH values from 4 to 7,which might be the first time that a Labrys strain was found capable of efficiently degrading PCNB.The degradation of PCNB was affected by oxygen,and the degradation decreased with increasing aeration.Exogenous electron donors such as glucose,lactic acid and succinic acid promoted the biodegradation of PCNB,while electron acceptors such as sodium nitrite,sodium sulfate,sodium nitrate and sodium sulfate inhibited PCNB biodegradation.The degradation of PCNB in sterile and non-sterile soils by a green fluorescent protein(GFP)-labeled strain,pcnb-21-gfp,was also studied.Cells of pcnb-21-gfp efficiently degraded 100 mg kg -1 PCNB in sterile and non-sterile soils and could not be detected after 42 days.Strain pcnb-21 might be useful in bioremediating PCNB-polluted soils and environment.     

中国亚热带不同种植制度下的土壤侵蚀

In order to optimise land use systems, to prevent erosion-induced degradation and to restore the degraded red soils in subtropical China, five cropping systems and four agroforestry systems were conducted in red soils with a slope of 7° from 1993 to 1995. The results showed that erosion risk period occurred from April to June, and the annual runoff and the losses of soil and nutrients with sediment were alarming for two conventional farming systems, whereas they were negligible for the farming systems with ridge tillage. Enrichment ratios of the lost soils from erosion were more than 1.20 for all nutrients with much higher values for hydrolysable N and organic matter. Compared with the control, the alley cropping systems also distinctly decreased runoff by 30% or 50%. However, the coverage of soil surface varied with alley cropping systems for the competition of nutrients and soil water, which made a profound difference in runoff. The cropping systems of sweet potato intercropped with soybean, the alley cropping systems and the measures of mulching and ridge tillage were the alternatives for red soil reclamation so as to prevent erosion-induced degradation.     

茶树种植对中国东部黄棕壤酸化的影响

Soil acidification is an important process in land degradation around the world as well as in China. Acidification of Alfisols was investigated in the tea gardens with various years of tea cultivation in the eastern China. Cultivation of tea plants caused soil acidification and soil acidity increased with the increase of tea cultivation period. Soil pH of composite samples from cultivated layers decreased by 1.37, 1.62 and 1.85, respectively, after 13, 34 and 54 years of tea plantation, as compared to the surface soil obtained from the unused land. Soil acidification rates at early stages of tea cultivation were found to be higher than those at the later stages. The acidification rate for the period of 0-13 years was as high as 4.40 kmol H⁺ ha^-1 year^-1 for the cultivated layer samples. Soil acidification induced the decrease of soil exchangeable base cations and base cation saturation and thus increased the soil exchangeable acidity. Soil acidification also caused the decrease of soil cation exchange capacity, especially for the 54-year-old tea garden. Soil acidification induced by tea plantation also led to the increase of soil exchangeable Al and soluble Al, which was responsible for the Al toxicity to plants.     

十氯酮污染土壤上根茎作物收割部分的污染状况

A bacterial strain, Arthrobacter oxydans (B4), capable of degrading benzo[a]pyrene (BaP) in water body, was isolated from a polycyclic aromatic hydrocarbons-contaminated site. Effects of different factors, such as reaction time, pH value, temperature and organic nutrients, on BaP biodegradation by the strain B4 were studied. After 5 d treatment, the concentration of BaP in mineral salts medium was reduced to 0.318 mg L-1 , compared to the initial concentration of 1.000 mg L-1 . There was a process of acid formation during the degradation with pH falling from initial 7.01 to 4.61 at 5 d, so keeping the water body under slightly alkaline condition was propitious to BaP degradation. Strain B4 efficiently degraded BaP at 20 to 37 ℃ with addition of organic nutrients. The biodegradation and transformation of BaP mainly occurred on cell surfaces, and extracellular secretions played an important role in these processes. Fourier transform infrared spectroscopy and gas chromatograph-mass spectrometer analyses of metabolites showed that ring cleavage occurred in the BaP degradation process and the resulting metabolically utilizable substrates were generated as sole carbon sources for B4 growth. Furthermore, mineralization extent of metabolites was verified by determining the total organic carbon and inorganic carbon in the degradation system.     

氮对土壤中氯氰菊酯及其降解产物3-苯氧基苯甲酸降解的影响

Increasing use of pyrethroid insecticides has resulted in concerns regarding potential effects on human health and ecosystems. Cypermethrin and its metabolite 3-phenoxybenzoic acid （PBA） have exerted adverse biological impacts on the environment; therefore, it is critically important to develop different methods to enhance their degradation. In this study, incubation experiments were conducted using samples of an Aquic Inceptisol supplied with nitrogen （N） in the form of NH4NO3 at different levels to investigate the effect of nitrogen on the degradation of cypermethrin and PBA in soil. The results indicated that appropriate N application can promote the degradation of cypermethrin and PBA in soil. The maximum degradation rates were 80.0% for cypermethrin after 14 days of incubation in the treatment with N at a rate of 122.1 kg ha^-1 and 41.0% for PBA after 60 days of incubation in the treatment with N at a rate of 182.7 kg ha^-1. The corresponding rates in the treatments without nitrogen were 62.7% for cypermethrin and 27.8% for PBA. However, oversupplying N significantly reduced degradation of these compounds. Enhancement of degradation could be explained by the stimulation of microbial activity after the addition of N. In particular, dehydrogenase activities in the soil generally increased with the addition of N, except in the soil where N was applied at the highest level. The lower degradation rate measured in the treatment with an oversupply of N may be attributed to the microbial metabolism shifts induced by high N.     

除草剂莠去津和灭草松单用和混用在土壤中的降解

The application of a mixture of bentazone （3-isopropyl-1H-2,1,3-benzothiadiazin-4（3H）-one-2,2-dioxide） and atrazine （6-chloro-N2-ethyl-N4-isopropyl-1,3,5-triazine-2,4-diamine） is a practical approach to enhance the herbicidal effect. Laboratory incubation experiments were performed to study the degradation of bentazone and atrazine applied in combination and individually in maize rhizosphere and non-rhizosphere soils. After a lag phase, the degradation of each individual herbicide in the non-autoclaved soil could be adequately described using a first-order kinetic equation. During a 30-d incubation, in the autoclaved rhizosphere soil, bentazone and atrazine did not noticeably degrade, but in the non-autoclaved soil, they rapidly degraded in both non-rhizosphere and rhizosphere soils with half-lives of 19.9 and 20.2 d for bentazone and 29.1 and 25.7 d for atrazine, respectively. The rhizosphere effect significantly enhanced the degradation of atrazine, but had no significant effect on bentazone. These results indicated that biological degradation accounted for the degradation of both herbicides in the soil. When compared with the degradation of the herbicide applied alone, the degradation rates of the herbicides applied in combination in the soils were lower and the lag phase increased. With the addition of a surfactant, Tween-20, a reduced lag phase of degradation was observed for both herbicides applied in combination. The degradation rate of bentazone accelerated, whereas that of atrazine remained nearly unchanged. Thus, when these two herbicides were used simultaneously, their persistence in the soil was generally prolonged, and the environmental contamination potential increased.     

温度对硼在土壤中吸附－解吸动力学的影响

The effect of temperature on the properties of boron adsorption-desorption in brown-red soil,yellowbrown soil and calcareous alluvial soil of Hubei Province was investigated with the mobile displacement technique.The experimental data of B adsorption-desorption amounts and reaction time at 25 and 40℃ were fitted by the zero-order,first-order and parabolic diffusion kinetic equations.The adsorption process was in conformity with the parabolic diffusion law at both the temperatures,and the values of rate constant of the parabolic diffusion equation in B adsorption were 0.138,0.124 and 0.105 mg kg^-1 min^-1/2 at 25℃,and 0.147,0.146and 0.135mg kg^-1 min^1/2 at 40℃ for the brown-red soil,yellow-brown soil,and calcareous alluvial soil,respectively,The relationship between amount of B desorption and reaction time could be well described by the first-order kinetic equation,and the corresponding values of rate constant were 0.0422,0.0563 and 0.0384min^-1 at 25℃,and 0.0408,0.0423 and 0.0401min^-1 at 40℃ for the brown-red soil,the yellow-brown soil and the calcareous alluvial soil,respectively.Therefore,the desorption process of B might be related to the amount of B adsorbed in soil,The higher th temperature,the lower the amount of B adsorption of the same soil in the same reaction time,The values of the apparent activation energy of B adsorption in the three soils calculated with the rate constants of parabolic diffusion equation were 3.27,8.44 and 12.99 kJ mol^-1,respectively,based on the experimental data of B adsorption amounts and reaction time at and 40℃.     

利用地统计学研究土壤有机质空间分布：评估意大利中部地区土地退化的重要指标

Soil organic matter (SOM) content is one of the main factors to be considered in the evaluation of soil health and fertility. As timing, human and monetary resources often limit the amount of available data, geostatistical techniques provide a valid scientific approach to cope with spatial variability, to interpolate existing data and to predict values at unsampled locations for accurate SOM status survey. Using geostatistical and geographic information system (GIS) approaches, the spatial variability of some physical and chemical soil parameters was investigated under Mediterranean climatic condition in the Abruzzo region of central Italy, where soil erosion processes accelerated by human induced factors are the main causes of soil degradation associated with low SOM content. Experimental semivariograms were established to determine the spatial dependence of the soil variables under investigation. The results of 250 soil sampling point data were interpolated by means of ordinary kriging coupled with a GIS to produce contour maps distribution of soil texture, SOM content related to texture, and C/N ratio. The resulting spatial interpolation of the dataset highlighted a low content of SOM in relation with soil texture in most of the surveyed area (87%) and an optimal C/N ratio for only half of the investigated surface area. Spatial location of degraded area and the assessment of its magnitude can provide decision makers with an accurate support to design appropriate soil conservation strategies and then facilitate a regional planning of agri-environmental measures in the framework of the European Common Agricultural Policy.     

不同类型表面活性剂增效去除焦化厂污染土壤中多环芳烃的研究

Surfactant enhanced remediation is thought to be an effective method for the remediation of soils polluted with hydrophoblc organic compounds. Desorption of polycyclic aromatic hydrocarbons （PAHs） from an abandoned manufactured gas plant （MGP） soil was evaluated using four eluting agents including Triton X-100 （TX100）, sodium dodecylbenzene sulfonate （SDBS）, rhamnolipid water solution （RWS） and rhamnolipid fermentation broth （RFB）. The weight solubilization ratios for acenaphthene and fluorene were in the order of TX100 〉 SDBS 〉 RWS 〉 RFB. The Sm value, which indicates the maximum amounts of surfactants adsorbed in the soil, was in the order of RWS 〉 RFB 〉 SDBS 〉 TX100. By using 8 g L-1 of TX100, SDBS and RWS and 100% of RFB, the T-PAHs removal for the MGP soil contaminated with 207.86 mg T-PAHs kg-1 dry soil was 48.0%, 45.7%, 1.9%, and 8.6%, respectively, while that decreased to 41.6%, 37%, 0.38%, and 1.3% for the soil contaminated with 3494.78 mg T-PAHs kg-1 dry soil. Only 8 g L-1 TX100 could remove all types of the 16 PAHs partly in the MGP soil, and the removal efficiencies of different PAHs ranged from 13% to 77.8%. The results of this study herein provide valuable information for the selection of TX100 surfactant for remediating PAH-contaminated soils in MGP.     

海藻酸钠固定化细菌对毒死蜱的降解特性

毒死蜱的生产和使用日趋广泛,由其造成的环境污染和危害不容忽视。微生物是影响有机磷农药在环境中降解的最主要因素,也被认为是降解有机磷农药最可靠而高效的途径。固定化技术是提高微生物降解农药效率的有效方法之一。本研究以海藻酸钠为载体,采用注射器滴定法将蜡状芽孢杆菌(Bacillus cer-eus)HY-1用海藻酸钠溶胶包埋,研究了反应时间、固定化菌接入量、pH和毒死蜱初始浓度对毒死蜱降解的影响以及固定化菌的重复使用效果。结果表明:海藻酸钠固定化菌能够高效降解基础培养基中的毒死蜱,制备固定化小球海藻酸钠溶胶的最适浓度为2.5%(w/v),小球的平均粒径为3 mm。在培养时间为60 h时,固定化菌对100 mg·L-1毒死蜱的降解率达到最大。固定化小球接入量为160 g·L-1时,对100 mg·L-1毒死蜱的降解率最高。固定化菌对毒死蜱的降解有着较宽泛的pH适应范围,碱性环境更有利于其对毒死蜱的有效降解。当毒死蜱初始浓度为80 mg·L-1和100 mg·L-1时,固定化菌对毒死蜱的降解率较高,达90%左右。固定化菌可重复利用降解毒死蜱,当利用4次后,固定化小球虽已发生崩解,但对100 mg·L-1毒死蜱的降解率仍高达47%。因此,海藻酸钠固定化蜡状芽孢杆菌对水体中毒死蜱的降解率较高,环境适应性较强,固定化菌可在毒死蜱污染的净化去毒方面发挥重要作用。     

酸性土壤磷分级新方法建立与生物学评价

土壤磷分级方法可用于估算土壤有效磷数量、不同土壤磷组分库数量及其对土壤有效磷的补充能力。以云南赤红壤、黄红壤及湖北棕红壤为供试材料,运用张守敬方法、蒋柏藩方法及本文提出的新方法,对三种酸性土壤和其石灰改良后的土壤磷进行分级研究,探讨石灰改良对酸性土壤磷组分数量及其生物有效性的影响。结果表明:Ca2-P、Al-P和Fe-P是酸性土壤主要的有效磷源,O-P(闭蓄态磷)也是潜在有效磷源,土壤中活性有机磷库相对比较稳定,可转化为高活性有效磷源供植物吸收利用。与两种经典磷分级方法相比,新方法将O-P划分为O-Al-P和O-Fe-P,O-Fe-P较好地反映了石灰处理与对照之间的土壤磷植物有效性差异。     

Photo-Assisted Degradation,Toxicological Assessment,and Modeling Using Artificial Neural Networks of Reactive Gray BF-2R Dye

This work investigates the degradation of Reactive Gray BF-2R dye (a blend of reactive yellow 145, reactive orange 122 and reactive black 5 dyes) using UV/H₂O₂, Fenton, and photo-Fenton-advanced oxidative processes, with artificial sunlight and UV-C radiations. The photo-Fenton process employing UV-C radiation was the most efficient under the conditions studied. The ideal conditions for the degradation of the dye, determined using a factorial design 2³ and a study of the concentration of hydrogen peroxide ([H₂O₂]), were [H₂O₂] equal to 40 mg L^?1, iron concentration [Fe] of 1 mg L^?1, and pH between 3 and 4. The Chan and Chu non-linear kinetic model predicted the kinetic data with a degradation of over 98% for color and 68% for aromatics after 60 min. The behavior of the chemical oxygen demand fitted the first-order kinetic model well, with a degradation of 64% after 60 min. The Multilayer Perceptron 7-11-2 artificial neural network model enabled to model the degradation process of the aromatics and accurately predict the experimental data. Toxicity tests indicated that the post-treatment samples were non-toxic for Escherichia coli bacteria, and Portulaca grandiflora and Basil sabory seeds. However, they inhibited the growth of Lactuca sativa seeds and Salmonella enteritidis bacteria. The photo-Fenton process with UV-C radiation degraded the dye studied efficiently and the degradation percentages were, on average, 7% and 5% higher for color than those observed when employing the Fenton and UV/H₂O₂ processes, respectively. With the aromatic, however, they were 84% and 62% higher, thus justifying the use of this process.     

Enhanced dissipation of DEHP in soil and simultaneously reduced bioaccumulation of DEHP in vegetable using bioaugmentation with exogenous bacteria

The widely used plastic film containing di(2-ethylhexyl) phthalate (DEHP) in agriculture has caused serious soil pollution and poses risks to human health through the food chain. An effective DEHP degradation bacteria, Microbacterium sp. J-1, was newly isolated from landfill soil. Response surface methodology was successfully employed for optimization resulting in 96% degradation of DEHP (200 mg L^?1) within 5 days. This strain degraded DEHP by hydrolysis of the ester bond and hydroxylation of the aromatic ring to form 2-ethyl hexanol, mono-(2-ethylhexyl) phthalate, phthalate acid, and protocatechuic acid, and subsequently transformed these compounds with a maximum specific degradation rate (q _max), half-saturation constant (K _s ), and inhibition constant (K _i ) of 1.46 day^?1, 180.2 mg L^?1, and 332.8 mg L^?1, respectively. Bioaugmentation of DEHP-contaminated soils with the strain J-1 greatly enhanced the DEHP dissipation rate (~88%). Moreover, this strain could efficiently colonize the rhizosphere soil of inoculated vegetables and further enhanced DEHP degradation (~97%), leading to a significant decrease (>70%) in DEHP accumulation in shoots and roots of the inoculated vegetables compared to uninoculated vegetables. The results highlighted the roles of the inoculated exogenous bacteria in simultaneously bioremediating contaminated soils and reducing bioaccumulation of DEHP in the edible part of the vegetable for food safety.     

Zusammensetzung und Speziierung der Bodenlösung eines mit Schwermetallen belasteten kalkreichen Bodens

Composition and Speciation of Soil Solution collected in a Heavy Metal polluted calcareous Soil Close to a brass foundry, which had emitted heavy metal containing dusts for over 80 years, soil water was collected in the topsoil (18 cm) and in the subsoil (40 cm) of a severely polluted Calcic Fluvisol by means of polyethylen suction cups over a period of 2 years. The total metal content of the topsoil (extracted with 2M HNO₃ at 100 °C for 2 hours) was 38 nmol g^?1, 24 μmol g^?1, and 25 μmol g^?1 for Cd, Cu, and Zn, respectively. The mean heavy metal concentrations of the soil solution were 0.5 mol L^?1, 300 nmol L^?1, and 200 nmol L^?1 in the topsoil and 0.6 nmol L^?1, 90 nmol L^?1, and 30 nmol L^?1 in the subsoil for Cd, Cu, and Zn, respectively. Solubility calculations showed that the soil solutions were undersaturated with respect to heavy metal carbonates as well as to hydroxides. It seems that the heavy metal concentration is determined by sorption processes rather than by precipitation. The composition of the soil solution has been shown to be governed by the presence, of calcite, by the soil temperature and by the partial pressure of CO₂ in the soil air. The pCO₂ in the soil air (in both depths) has been estimated at 2 mbar during the winter term and at 20 mbar during the summer term. A corresponding increase of the concentration of macroelements (Ca, Mg, Na) as well as of total dissolved carbonate and of dissolved organic matter (DOC) has been measured in the summer half year. No significant seasonal variations of the heavy metal concentrations were detected and no correlations with concentrations of other components could be found.     

Crop Residue Effects on Calcium,Magnesium, Potassium,and Sodium Runoff Losses from a Soil Prone to Crusting

In Galicia (northwestern Spain), cultivated soils developed on schists from the Ordenes series are susceptible to surface degradation, mostly when soil organic content decreases. Therefore, management systems that protect the soil and increase its organic-matter content should also improve its quality. However, tillage practices may cause crusting. Degraded soil surface conditions favor surface runoff, thus enhancing nutrient losses. This study examined the effect of applying crop residues to the soil surface on the basic cation nutrient [calcium (Ca), magnesium (Mg), potassium (K), and sodium (Na)] losses by runoff from a tilled soil with relatively low organic-matter content. Runoff and sediment yield were measured on 1-m² plots using a rainfall simulator with constant 65 mm h^?1 intensity. Four successive rainfall applications were performed, the first three at 25 mm each and the last at 65 mm. Added corn straw varied between 0 and 4 t ha^?1 in the five treatments studied. Total and dissolved concentrations of the elements studied showed a tendency to decrease due to the effect of corn straw on soil losses. After 140 mm cumulative rainfall, total nutrient losses were as follows: Ca from 12.32 to 28.94 mg L^?1, Mg from 20.81 to 148.90 mg L^?1, K from 14.20 to 35.17 mg L^?1, and Na from 14.99 to 23.41 mg L^?1. The relative contribution of the dissolved fraction to the total nutrient content loss was highly variable, being up to 90% for Na. The results confirm that corn residues applied to a degraded soil, with low structural stability, prevent cation nutrient losses.     

Polycyclic Aromatic Hydrocarbon Oxidation from Concentrates Issued from an Attrition Process of Polluted Soil Using the Fenton Reagent and Permanganate

This study was conducted to determine the optimal conditions for PAH degradation from highly contaminated attrition sludge (PAC) using a Fenton process or successive permanganate (KMnO₄) oxidation and Fenton processes. The following parameters were studied to optimize the Fenton oxidation process: the amounts of reactants based on the stoichiometric oxidant demand (SOD), the reactant addition protocol and number of doses, and the solid/liquid ratio (S/L). The results showed that the following conditions were optimum: TS?=?30%, 7.5 times SOD, H₂O₂/Fe²⁺ ratio?=?10, and added five times during 60 min, which allowed the degradation of 43% of total 27 PAHs from the PAC. Successive Fenton and KMnO₄ oxidation processes were also tested. PAH degradation using a sequential Fenton process followed by KMnO₄ oxidation (or KMnO₄ followed by Fenton) was higher than for the use of Fenton or KMnO₄ treatment alone. Up to 71% of the total 27 PAHs were degraded when using a combination of both processes. It appeared that the sequential treatment is a viable method for the significant degradation of 27 PAHs from PAC (t value?>?2.77).     

Comparison of Various Phosphate Stabilisation Agents for the Immobilisation of Ni and Zn in Sewage Sludge

This paper reports the results of the treatment of polychlorinatedbiphenyl (PCB) contaminated sandy soils (100 mg kg^-1 Aroclor 1242) with the Fenton advanced oxidation process (AOP). The results obtained in the various assays permitted the optimization of conditions as follows: 5% H₂O₂; 100 ppm of Fe³⁺; and a ratio of sandy soil mass/volume of oxidizing solution (m/V) of 1/3 g mL^-1. In addition, these tests established the need for agitation and dispensed with the need for heat. The results obtained confirm that the oxidation process occurs in solid phase (on the PCBs adsorbed to soil particles), producing 98% elimination of the original PCB structure and 82% dechlorination, all within a reaction time of 72 hr. The degree of elimination was found to be dependent on the level of congener chlorination and the process displays a pseudo first order kinetics. In addition, the Fenton chemical oxidation process may be complemented by subsequent aerobic biological degradation which, after 15 days, produces 72% mineralization of the products generated during the chemical oxidation process.     

Chemistry differences in two streams entering an acidic lake in the Adirondack Mountains,New York (U.S.A.)

Solution chemistry was measured in two major inlets, lake water column, lake outlet, and soils of the South Lake watershed in the Adirondack Mountains, New York. The east inlet had greater concentrations of H⁺, sulfate-S, and Al and smaller concentrations of base cations and silica than the west inlet (70, 116, 25, 90, 64 and 4, 99, 8, 228, 148 μeq L^?1 of H⁺ and sulfate-S, μmol L^?1 Al, μeq L^?1 total base cations and μmol L^?1 silica in east and west inlets, respectively). Concentrations of base cations in C horizon soil solutions (157 μeq L^?1 total base cations) were smaller and greater than west and east inlets, respectively. This suggests that water flowing into the west inlet contacted deeper mineral layers, whereas water reaching the east inlet did not. Lake and lake outlet concentrations were also intermediate between the two inlets, and the lake was acidic (pH 4.9 to 5.1) with relatively high total monomeric Al concentrations (8 to 9 μmol Al L^?1). The east inlet also had greater DOC concentrations than the west (0.38 and 0.24 μmol C L^?1, respectively), again indicating that soil solutions entering the east inlet passed through the forest floor but had more limited contact with deeper mineral layers in comparison with the west inlet. Differences between the streams are hypothesized to be related to contact of percolating solutions with mineral soil horizons and underlying glacial till, which provides neutralization of acidic solutions and releases base cations. This work indicates that processes controlling surface water acidification can be spatially quite variable over a small watershed.