Photodegradation of rotenone in soils under environmental conditions

An environmental fate study was performed to analyze the effects of soil components on the photochemical behavior of rotenone. Photodegradation experiments were carried out on three types of soil collected in southern Italy, Valenzano (VAL), Turi (TUR), and Conversano (CON), from April to June 2006. Soil thin-layer plates (1 mm thick) were spiked with 1.5 mg/kg of rotenone and exposed under natural conditions of sunlight and temperature. The plates were removed from the sunlight at predetermined intervals of continuous irradiation. Other soil samples, control and sterilized, were kept in the dark to evaluate possible effects of chemical and microbiological degradation during the irradiation experiment. The time for 50% loss of the initially applied rotenone varied from 5 to 7 h, following the order TUR < CON < VAL. In environmental studies, changes in temperature and/or moisture affected the degradation rate and caused deviations from first-order kinetics. The photolysis reaction fit the two compartment or the multiple compartment model pathways better. A fast initial decrease during the first 5 h of rotenone irradiation was followed by a much slower decline, which clearly indicates the rather complex chemical process of rotenone photodegradation on soil surfaces. Also, the degradation was shown to be directly related to the soil concentration of clay and organic matter. Rotenolone (12abeta-hydroxyrotenone) was detected by HPLC/DAD/MS analysis as the only photodegradation byproduct of rotenone in soil thin layers. Results provide additional insights on the rates and the mechanisms of rotenone degradation, aiming to describe more clearly the degradation performance of chemical residues in the environment.     

Some specific features of the biochemical properties of soils

Soil can be perceived as a matric system with certain compartments. The mineral, organic, and organomineral matrices can be distinguished in it. The synthesis of humus in the soil is a continuous process with an abiotic final stage. The synthesis of polymers takes place on mineral and organomineral matrices. The development of humus horizon considerably reduces the migration of organic substances in the soil. Three different types of element associations can be distinguished in the soil: the geochemical association inherited from the parent material, the biochemical association inherited from the remains of living organisms entering the soil, and the biogeochemical (or proper pedogenic) association appearing in the course of interaction between the first two element associations under the given type of the soil water regime. The inhibitors and, probably, stimulators of plant growth also exist in the soil.     

液体培养研究不同土壤中硝化活性

A red soil, a fluvo-aquic soil and a permeable paddy soil were used in a long-term investigation to study changes in nitrification with treatments: 1) soil incubation, 2) liquid incubation inoculated with soil samples, and 3) liquid incubation inoculated with ammonia-oxidizing bacteria (AOB) from the soils. There were significant differences (P < 0.001) in nitrification rates among the three soils when measured for 28 days by adding (NH4)2SO4 at the rate of 154 mg N kg-1 dry soil to fresh soil. However, the amounts of nitrifying bacteria in the three soils were not related to soil nitrification capacity. When the soil samples or the isolates of AOB enriched from the corresponding soil were incubated in liquid with pH 5.8, 7.0 and 8.0 buffers and 10 mmol L-1 ammonium nitrogen, there were no significant nitrification differences in the same soil type at each pH. The ability to oxidize ammonia through AOB from different types of soils in a homogeneous culture medium was similar, and the soil nitrification capacity could reflect the inherent properties of a soil. Altering the culture medium pH of individual soil type also showed that acidification of an alkaline fluvo-aquic soil decreased nitrification capacity, whereas alkalinization of the acidic red soil and permeable paddy soil increased their nitrification. For a better insight into factors influencing soil nitrification processes, soil properties including texture and clay composition should be considered.     

Genetic features of soils on sorted sand deposits of different origins in the Kola Peninsula

Differences in the chemical composition of soils developed from sorted sands of different origins are revealed. The iron-illuvial podzols on rich glaciofluvial and marine sands are characterized by well-pronounced Al-Fe-humus differentiation of the Si, Al, and Fe in the soil profile. These soils are relatively similar in their bulk elemental composition. The difference between them is seen in the degree of differentiation of the soil profiles; it is stronger in the soils developed from glaciofluvial deposits. This is particularly true with respect to the oxalate-soluble iron and aluminum hydroxides. The deposits derived from the red-colored Tersk sandstone and processed by the sea (in the coastal zone of the White Sea) have the poorest chemical composition. In the soils developed from them, the differentiation of oxalate-soluble compounds is slightly pronounced (for Fe) or completely absent (for Si and Al). These soils can be classified as podzolized ferruginous red-colored psammozems (within the order of poorly developed soils) with the following horizons: O-Ce-Cf-C. The Ce horizon has the features of podzolization, and the Cf horizon has some features attesting to the illuvial accumulation of Fe. The profile of these soils inherits a reddish tint from the parent material.     

Microbial activity in pig slurry-amended soils under semiarid conditions

Soil amendment with manures from intensive animal industries is nowadays a common practice that may favorably or adversely affect several soil properties, including soil microbial activity. In this work, the effect of consecutive annual additions of pig slurry (PS) at rates of 30, 60, 90, 120 and 150 m³ ha⁻¹ y⁻¹ over a 4-year period on soil chemical properties and microbial activity was investigated and compared to that of an inorganic fertilization and a control (without amendment). Field plot experiment conducted under a continuous barley monoculture and semiarid conditions were used. Eight months after the fourth yearly PS and mineral fertilizer application (i.e. soon after the fourth barley harvest), surface soil samples (Ap horizon, 0-15 cm depth) from control and amended soils were collected and analysed for pH, electrical conductivity (EC), contents of total organic C, total N, available P and K, microbial biomass C, basal respiration and different enzymatic activities. The control soil had a slightly acidic pH (6.0), a small EC (0.07 dS m⁻¹), adequate levels of total N (1.2 g kg⁻¹) and available K (483 mg kg⁻¹) for barley growth, and small contents of total organic C (13.2 g kg⁻¹) and available P (52 mg kg⁻¹). With respect to the control and mineral fertilized soils, the PS-amended soils had greater pH values (around neutrality or slightly alkaline), electrical conductivities (still low) and contents of available P and K, and slightly larger total N contents. A significant decrease of total organic C was observed in soils amended at high slurry rate (12.3 g kg⁻¹). Compared with the control and mineral treatments, which produced almost similar results, the PS-amended soils were characterized by a higher microbial biomass C content (from 311 to 442 g kg⁻¹), microbial biomass C/total organic C ratio (from 2.3 to 3.6%) and dehydrogenase (from 35 to 173 μg INTF g⁻¹), catalase (from 5 to 24 μmol O₂ g⁻¹ min⁻¹), BAA-protease (from 0.7 to 1.9 μmol  g⁻¹ h⁻¹) and β-glucosidase (from 117 to 269 μmol PNP g⁻¹ h⁻¹) activities, similar basal respirations (from 48 to 77 μg C-CO₂ g⁻¹ d⁻¹) and urease activities (from 1.5 to 2.2 μmol  g⁻¹ h⁻¹), and smaller metabolic quotients (from 6.4 to 7.7 ng C-CO₂ μg⁻¹ biomass C h⁻¹) and phosphatese activities (from 374 to 159 μmol PNP g⁻¹ h⁻¹). For example, statistical analysis of experimental data showed that, with the exception of metabolic quotient and total organic C content, these effects generally increased with increasing cumulative amount of PS. In conclusion, cumulative PS application to soil over time under semiarid conditions may produce not only beneficial effects but also adverse effects on soil properties, such us the partial mineralization of soil organic C through extended microbial oxidation. Thus, PS should not be considered as a mature organic amendment and should be treated appropriately before it is applied to soil, so as to enhance its potential as a soil organic fertilizer.     

Microbial destruction of chitin in soils under different moisture conditions

The most favorable moisture conditions for the microbial destruction of chitin in soils are close to the total water capacity. The water content has the most pronounced effect on chitin destruction in soils in comparison with other studied substrates. It was found using gas-chromatographic and luminescent-microscopic methods that the maximum specific activity of the respiration of the chitinolytic community was at a rather low redox potential with the soil moisture close to the total water capacity. The range of moisture values under which the most intense microbial transformation of chitin occurred was wider in clayey and clay loamy soils as compared with sandy ones. The increase was observed due to the contribution of mycelial bacteria and actinomycetes in the chitinolytic complex as the soil moisture increased.     

Hydrolysis of ammonium polyphosphate in soils under aerobic and anaerobic conditions

Summary The hydrolysis of fertilizer-grade solid and liquid ammonium polyphosphate (APP) was studied on an aluvial (Entisol, Typic Ustifluvent), a sodic (Entisol Aquic Ustifluvent), and a laterite (Oxisol, Aquox) soil under aerobic and anaerobic conditions. The hydrolysis rate was the fastest on laterite, intermediate on sodic, and slowest in the alluvial soil. Ammonium polyphosphate hydrolyzed more rapidly under anaerobic than under aerobic conditions. The hydrolysis of liquid ammonium polyphospahte was faster than that of solid ammonium polyphosphate in all soils. The half-life values for the polyforms of P in liquid ammonium polyphosphate ranged from 1.6 to 2.0 days under anaerobic and from 5.2 to 8.7 days under aerobic conditions. The corresponding values for solid ammonium polyphosphate were 3.9 to 9.2 days under anaerobic and 12.5 to 27.0 days under aerobic conditions.     

Specific features of the development of soils of hydromorphic ecosystems in the northern taiga of Western Siberia under conditions of cryogenesis

Differently directed and heterochronous cryogenic processes have contributed to the contrasting soil cover patterns and spatial heterogeneity of the properties of soils in hydromorphic ecosystems of the discontinuous permafrost zone of the northern taiga in Western Siberia. Frost heave and permafrost thawing within ecosystems of highmoor bogs have led to the development of specific cryogenic landforms, such as flat-topped and large peat mounds. A set of cryogenic soils is developed in these ecosystems; it includes different variants of cryozems, gleyzems (Cryosols), and peat soils (Histosols). The distribution of these soil types is controlled by the local topography and thawing depth, other factors being insignificant. Alternation of peat horizons of different types and ages, whirl-like patterns of horizon boundaries, considerable variations in the thickness of soil horizons, and inversions of soil horizons under the impact of frost cracking, frost heave, and cryoturbation are typical of the considered soils. Thawing depth is the most significant factor affecting the thickness of organic horizons, the soil pH, and the degree of decomposition of peat. As a result of the upward movement of bog ecosystems under the impact of frost heave, peat soils are subjected to considerable transformation: peat horizons undergo mineralization, and the thickness of organic horizons decreases; in some cases, eluvial–illuvial differentiation of the mineral horizons takes place, and peat podzols are developed. However, the opposite process of the return of the soils to the bog stage of pedogenesis with peat accumulation may take place in any time in the case of activation of thermokarst processes.     

黄土区工程堆积体陡坡坡面径流调控工程措施的减沙效应

定量分析减少径流和改变水沙关系在泥沙调控中的不同作用,对于深刻理解径流调控措施的水土保持效益具有重要意义。以黄土区工程堆积体陡坡坡面(36°)为例,探讨了野外模拟径流冲刷试验条件下,不同工程措施及其组合调控坡面径流的水沙效应及其作用效率。结果表明:1)不同工程措施均能较好地调控坡面径流侵蚀过程,不同情形下的产流时间控制比为2～20,径流量控制比为0.45～0.78,产沙量控制比为0.20～0.59;平均含沙量控制比为0.38～0.79;2)减流控沙作用是工程措施调控坡面侵蚀产沙的主要原因,水沙关系调沙作用则受减流控沙作用的制约;3)水平阶类措施的水沙关系调沙量与减流控沙量呈线性正相关,当减流控沙量超过一定临界值时,水沙关系才开始发挥调沙作用;水平沟类措施的水沙关系调沙量与减流控沙量呈二次函数关系,水沙关系调沙量存在极大值;4)水平沟类措施调控泥沙的作用效率高于水平阶类措施,水平沟+鱼鳞坑的组合可很好地发挥减流控沙和水沙关系调沙作用的潜力(55%),使二者在较高的水平上维持相对平衡;因此,不同工程措施与组合的实际应用应以具体的水土保持效益和防治目标为布设依据。研究可为堆积体陡坡治理的工程措施优化提供理论参考。     

Carbon balance in the soils of abandoned lands in Moscow region

A quantitative assessment of the carbon balance was performed in gray forest soils of the former agricultural lands abandoned in different time periods in the southern part of Moscow oblast. It was based on the field measurements of the total and heterotrophic soil respiration and the productivity of biocenoses. Geobotanical investigations demonstrated that the transformation of the species composition of herbs from weeds to predominantly meadow plants occurred in five–ten years after the soil was no more used for farming. The amount of carbon assimilated in the NPP changed from 97 g C/m² year in the recently abandoned field to 1103 g C/m² year in the 10-year-old fallow, and the total annual loss of carbon from the soil in the form of CO₂ varied from 347 to 845 g C/m² year. In five years, the former arable lands were transformed into meadow ecosystems that functioned as a stable sink of carbon in the phytomass and the soil organic matter.     

Evolution of organic matter added to soils under cultivation conditions

The development of an organic matter (OM) based on mixed sheep manure and peat, when it was incorporated into soils as fertilizer, was studied. The experiment was carried out in soils under almond tree culture, with drip irrigation and non irrigation regimes. Two doses, 10 and 4.5 kg tree^–1, were assayed. Changes in the humic acid fraction one year after incorporation into soils showed oxidation and enrichment in condensed structures, as observed by an increase of the O*:H* ratio and a decrease of the H*:C* ratio, and also by FTIR spectra. The oxidative process was more significant in the coarser textured and also in the non‐irrigated soil. The evolution of the ratios C_ext:C_ox and C_HA:C_FA throughout the culture cycle was followed by sampling and chemical analysis of different forms of organic carbon. Evolution of C_ext:C_ox showed a uniform humification state in the irrigated soil, and a significant decrease in the non‐irrigated soil, at the beginning of the experiment. Curves of C_HA:C_FA evolution showed changes attributed to mineralization or drainage of the fulvic acids fraction, giving a maximum in spring in both soils and a final increase at the end of the cycle by drainage only in the irrigated soil.     

Microbial biomass and activity in salt affected soils under arid conditions

The effects of salinity on the size, activity and community structure of soil microorganisms in salt affected arid soils were investigated in Shuangta region of west central Anxi County, Gansu Province, China. Eleven soils were selected which had an electrical conductivity (EC) gradient of 0.32–23.05 mS cm⁻¹. There was a significant negative exponential relationship between EC and microbial biomass C, the percentage of soil organic C present as microbial biomass C, microbial biomass N, microbial biomass N to total N ratio, basal soil respiration, fluorescein diacetate (FDA) hydrolysis rate, arginine ammonification rate and potentially mineralizable N. The exponential relationships with EC demonstrate the highly detrimental effect that soil salinity had on the microbial community. In contrast, the metabolic quotient (qCO₂) was positively correlated with EC, and a quadratic relationship between qCO₂ and EC was observed. There was an inverse relationship between qCO₂ and microbial biomass C. These results indicate that higher salinity resulted in a smaller, more stressed microbial community which was less metabolically efficient. The biomass C to biomass N ratio tended to be lower in soils with higher salinity, reflecting the bacterial dominance in microbial biomass in saline soils. Consequently, our data suggest that salinity is a stressful environment for soil microorganisms.     

Microbial biomass and activity in alkalized magnesic soils under arid conditions

The effects of salinity and Mg²⁺ alkalinity on the size and activity of the soil microbial communities were investigated. The study was conducted along the border area of the alluvial fan of the Taolai River. Thirty soil samples were taken which had an electrical conductivity (EC) gradient of 0.93-29.60 mS cm⁻¹. Soil pH ranged from 8.60 to 9.33 and correlated positively with Mg²⁺/Ca²⁺ ratio, exchangeable Mg²⁺ percentage and HCO₃⁻+CO₃²⁻. Mg²⁺/Ca²⁺ varied considerably from 3.04 to 61.31, with an average of 23.03. Exchangeable Mg²⁺ percentage generally exceeded 60% and had a positive correlation with Mg²⁺/Ca²⁺. HCO₃⁻+CO₃²⁻ averaged 1.63 cmol kg⁻¹ and usually did not exceed 2.0 cmol kg⁻¹.Microbial biomass, indices of microbial activity and the activities of the hydrolases negatively correlated with Mg²⁺/Ca²⁺ or exchangeable Mg²⁺ percentage. Biomass C, biomass N, microbial quotient (the percentage of soil organic C present as biomass C), biomass N as a percentage of total N, potentially mineralizable N, FDA hydrolysis rate and arginine ammonification rate decreased exponentially with increasing EC. The biomass C/N tended to be lower in soils with higher salinity and Mg²⁺ alkalinity, probably reflecting the bacterial dominance in microbial biomass in alkalized magnesic soils. The metabolic quotient (qCO₂) positively correlated with salinity and Mg²⁺ alkalinity, and showed a quadratic relationship with EC, indicating that increasing salinity and Mg²⁺ alkalinity resulted in a progressively smaller, more stressed microbial communities which was less metabolically efficient. Consequently, our data suggest that salinity and Mg²⁺ alkalinity are stressful environments for soil microorganisms.     

Role of amendments on N cycling in Mediterranean abandoned semiarid soils

Soils found in semiarid areas of the Mediterranean Basin are particularly prone to degradation due to adverse climatic conditions with annual rainfall <300 mm and high temperatures being responsible for the scant vegetal growth and the consequent lack of organic matter. A three-year field experiment was conducted to test the potential of two organic amendments (sludge and compost) to improve soil quality and plant growth in a semiarid degraded Mediterranean ecosystem. Since little is known about N dynamics in such assisted ecosystems, we investigated the effects of this practice on key processes of the global N cycle. Besides soil chemical and biological parameters and vegetation cover, we measured absolute and specific potential nitrification and denitrification rates and quantified the size of the ammonia oxidising and denitrifying bacterial populations via quantitative PCR (amoA and nirS genes). At the end of the experiment soil fertility, microbial activity and plant growth had improved in treated plots. Amendments increased the amount of ammonia oxidisers and denitrifiers in soil, but the relative proportion of these groups varied in relation to the total microbial community, being higher in the case of ammonia oxidisers but not in the case of denitrifiers. As a consequence, significantly higher potential nitrification and denitrification rates were measured on a global basis in amended soils. Yet specific activities (potential rate/gene copy numbers) were lower for ammonia oxidisers in amended soils and for denitrifiers in sludge treated soils than those observed in control plots. Organic amendments influenced resource availability, the size and the activity patterns of microbial populations involved in long-term N dynamics. Therefore N cycling processes may play a key role to assist sustainable restoration practices in semiarid degraded areas.     

Temporal evolution of salts in Mediterranean soils transect under different climatic conditions

The research was conducted in Israel at three sites along a south–north axis, characterized by increasing annual rainfall, from 310 mm at site LAV in the south through 600 mm at site MAT (600), to 800 mm at site EIN in the north. At each site soil samples were taken during several seasons (September 2001 through April 2003), in three dominant microenvironments at 0–2 cm and 5–10 cm. The following microenvironments were selected at LAV and MAT: “Under Shrub” (US), “Between Shrubs” (BS), and “Under Rock fragments” (UR). At EIN the selected microenvironments were US, BS, and “Under Tree” (UT). In each soil sample electrical conductivity (EC), pH, and concentrations of several ions were determined. The objective was to analyze the effects of soil microenvironments and climatic conditions on the temporal dynamics of salt concentrations. In all microenvironments at all sites the minimal values of EC were found in the rainy season (January or April), and the maximal values in the dry season (September). In the rainy season the temporal variability of EC in the topsoil was regulated by: (1) clay, which restricted the leaching of salts from the topsoil when EC was low; and (2) surface features (microenvironment), when EC was high. In the UT, US, and UR microenvironments the rainy season could be divided into two periods with respect to their effect on salt movement in the topsoil: at the beginning of the rainy season (September–January) the reduction in EC was relatively moderate, especially with regard to ions involved in biotic activity (Mg⁺⁺ and K⁺), whereas, late in the rainy season (January–April) there was enhanced reduction in EC. In contrast, in BS the regulation of salt movement was weak at all sites. Hence, in this microenvironment the salts concentration (mainly Na⁺ and Cl⁻) responded rapidly to changes in rain amount and soil moisture and temperature. In the dry season (April–September) the temporal variation in EC varied not only between microenvironments but also between sites. In US, where local surface features were similar at all sites (the same shrub), the rise in EC was maximal at LAV (mainly Ca⁺⁺ and Na⁺), and gradually diminished toward EIN. Thus, the contribution of regional sources to the salts added to the soil diminished toward the humid site, EIN, where the EC hardly changed in any microenvironment. In BS and UR microenvironments the rise in EC (mainly in Ca⁺⁺, Na⁺, and K⁺) was greatest at site MAT, and decreased toward LAV and EIN. It seems that this pattern was affected also by changes in local biotic activity.     

Features of abandoned cemetery soils on sandy substrates in Northern Poland

Morphological and chemical features of cemetery soils (Necrosols and undisturbed cemetery soils) have been studied with Northern Poland as an example. Special attention has been given to the contents of the total phosphorus (as an indicator of the anthropogenic impact); the organic carbon; the total nitrogen; the calcium carbonate; and the changes in the acidity and total Ca, Na, K, Al, Fe, Mg, Zn, Cd, and Pb. The soil profiles have been compared to the control soil (a Brunic Arenosol according to the WRB classification) occurring beyond the cemetery area. The changes in the studied burial soils are mainly manifested in their morphology: the disturbance of the primary genetic horizons and the presence of mixed soil horizons and artifacts (bones, coffin remains, limestone-concrete debris of the cemetery infrastructure). Such changes in the chemical properties as an increase in the contents of the organic carbon and total nitrogen and the soil reaction were observed. Our studies have shown that the highest Ptotal concentration is observed in the A horizons of the anthropogenic burial horizons and undisturbed cemetery soils. The content of phosphorus in the Necrosols is significantly higher than that in the control soil profile, as is observed for the Cgrb layers of burial Necrosols. The morphology and chemistry of the undisturbed cemetery soils are very similar to those of the control profile.     

Characterization of mercury species in contaminated floodplain soils

The chemical form or speciation of mercury (Hg) in the floodplain soils of the East Fork Poplar Creek in Oak Ridge, Tennessee, a site contaminated from past industrial activity, was investigated. The speciation of Hg in the soils is an important factor in controlling the fate and effect of Hg at the site and in assessing human health and ecological risk. Application of three different sequential extraction speciation schemes indicated the Hg at the site was predominantly relatively insoluble mercuric sulfide or metallic Hg, though the relative proportions of each did not agree well between procedures. Application of X-ray and electron beam studies to site soils confirmed the presence of metacinnabar, a form of mercuric sulfide, the first known evidence of authigenic mercuric sulfide formation in soils.     

Carbon budget in arable gray forest soils under different land use conditions

The effect of different land-use practices on the carbon budget in old arable gray forest soils of Russia was studied in field experiments. A short-term (for 6–7 years) cessation of mineral fertilization had no negative effects on the carbon budget in the agrocenoses studied. Only the combination of zero fertilization with the return to monoculture and the introduction of black fallows created a negative budget of humus in the soil. The regrassing of the eroded arable soil for 24 years increased the humus reserve in the 0- to 60-cm layer by a factor of 1.6–1.7. The average annual accumulation of carbon and nitrogen after the restoration of the perennial vegetation was 106–128 g C/m² and 11–16 g N/m², respectively.