Aluminium speciation: Variations caused by the choice of analytical method and by sample storage

We have compared a new FIA method (M1) for aluminium speciation in natural waters and a manual one based on one of Driscoll's proposals (M2). In synthetic solutions, aluminium's fluoro complexes were measured as ‘labile monomeric AP (Al _i ) by M2, but not as ‘quickly reacting Al’ (Al _qr ) by M1. Aluminium's complexes with Nordic Reference Humic Acid were measured neither as Al _i nor as Al _qr , and the same result was obtained for Al's citrato complexes. After excluding aluminium's fluoro complexes from Al _i , the results of the two methods agreed well for soil leaching samples and fairly well for natural water samples. Detection limits: 10μg L^?1 (ca. 0.4 μM) for both methods. Sample throughputs: M1∶66 injections h^?1; M2∶5 samples h^?1. Repeatabilities (RSD) on natural water samples: M1∶0.6–5.8% and M2 0.7–4.6%. Sample storage studies on soil solutions (FIA method) indicated that storage effects were ‘sample type specific’. A sample with a low level of Al _qr and a high DOC level (P2A) was more sensitive to storage than one with a high [Al] _qr and a low [DOC] (P2B^*). The decrease in [Al] _qr was statistically significant after 10 h (P2A) and 24 h (P2B^*), respectively. After 3 days' storage, [Al] _qr had decreased by some 40% in P2A, while the decrease in P2B^* was less than 10% after 8 days. The results of this part of the study also emphasize the importance of careful method standardization in sample storage studies.     

Aluminium speciation in aqueous solutions

Water, Air, & Soil Pollution - An analytical scheme for the speciation of monomeric and polymeric forms of Al in aqueous solutions is presented. After monomer isolation by complexation with...     

Aluminium speciation and pH of an acid soil in the presence of fluoride

The aim was to determine whether the addition of F to an acid soil reduces the concentration of free Al³⁺ and other forms that have been shown to be toxic to plants. The ability of two different extracts to reflect Al speciation in the soil solution was also investigated. Addition of F (0-5.2μmolg⁻¹) to an acid soil (pH 4.15, soil solution) increased the pH and total concentrations of Al and F in the soil solution whereas Al³⁺ remained constant or decreased. Soil solution pH, total soluble Al and Al extracted by 0.01 m CaCl₂ are not good predictors of the likelihood of aluminium toxicity in soils containing soluble fluoride.     

Sorption of dissolved organic carbon in soils: effects of soil sample storage,soil-to-solution ratio,and temperature

Experiments on the sorption of dissolved organic carbon (DOC) in soils were mainly conducted in batch approaches. Because varying setups were used in these studies, comparison of the results requires knowledge on the effects that different experimental conditions may have on the sorption of DOC. This investigation evaluated the DOC sorption of soils using differently pretreated soil samples (field-fresh (two sampling dates), air-dried, stored at 3°C and −18°C), at different soil-to-solution ratios (1:40, 1:20, 1:10 and 1:5 w/v) and different temperatures (5°C, 15°C, 25°C and 35°C). The sorption of DOC was analyzed using the initial mass (IM) approach, which regressed the initial amount of sorbate (normalized to soil mass) against the sorbed amount (normalized to soil mass). The DOC release — when a solution without DOC was added — strongly increased with temperature and soil-to-solution ratio. Among the different types of sample storage and preparation, air-drying resulted in the largest DOC release. The smallest release was from the field-fresh samples. Freezing and storage at 3°C resulted in intermediate DOC release with freezing having the greater effect. The release from air-dried samples exceeded that of field-fresh samples by a factor of four at maximum. In contrast, none of the experimental setups influenced the slope of the IM isotherms. Thus, it seems possible to compare directly the binding affinity of DOC to different soils as determined at varying experimental conditions.     

Testing Sugarbush soils: Effects of sample storage and drying

Abstract

The need for an assessment of sampling effects on forest surface soils has followed the increased interest in the fertility status of northern hardwood forests, especially sugar maple stands. We sampled soils from a fertility research site in north‐central Vermont and measured the effects of drying (55°C) and moist, low temperature storage (4°C) on extractable aluminum (Al), calcium (Ca), potassium (K), magnesium (Mg), phosphorus (P), manganese (Mn), zinc (Zn), boron (B), iron (Fe), and pH. Drying induced large, significant increases in ammonium acetate (pH 4.8) extracted P, Mn, B, and Fe. Smaller, but statistically significant, changes were found in pH, Al, Ca, and Zn. Moist storage for 10 weeks resulted in small significant changes in only pH and K. The magnitude of these changes indicate that samples can be stored at low temperature for up to 10 weeks with little effect on soil test results. Drying should be avoided because of its drastic effect on the extractability of many soil test elements.     

Aluminium speciation: comparison of two spectrophotometric analytical methods and observed concentrations in some acidic aquatic systems in Southern Norway

The toxicity of A1 to aquatic biota varies with speciation. Driscoll (1980) has developed a scheme for determining three A1 fractions using the ferron method (Smith, 1971) to detect Al. We have compared the results obtained with Driscoll's method with those obtained when pyrocatechol violet is the complexing agent. The agreement is generally satisfactory. The latter method is more sensitive and less influenced by interferences. Results for water samples, mainly from two streams in southern Norway, are discussed. For most samples the labile monomeric Al-fraction dominates, the major species being either A1³⁺ or AIF²⁺. Possible equilibria between A1³⁺ and some minerals and the temperature changes in these equilibria, are discussed.     

Carbon storage in low‐alpine grassland soils: effects of different grazing intensities of sheep

Grazing in outlying fields has a long history and is important in local communities worldwide. During the last few decades, grazing pressure has both decreased and increased in alpine ecosystems, but little is known about the effects on soil carbon storage. As part of a sheep grazing experiment with three sheep stocking rates of no sheep (control), 25 and 80 sheep km^?2, we tested effects of grazing on soil organic carbon storage, the form of soil organic matter (SOM) and its lability (potential carbon mineralization) in organic horizons of low‐alpine grasslands in southern Norway. After 7 years of grazing, the greatest sheep density reduced soil organic carbon concentration (% SOC) and carbon stocks at equivalent soil mass as compared with the control. In contrast, the low stocking rate caused no change or a slight increase. The form of SOM, expressed as ratios of particulate organic carbon to soil organic carbon, was only slightly affected by grazing, with a small decrease and moderate increase at the greater and smaller stocking rate, respectively. The lability of SOM was not affected by grazing directly, but was significantly related to the mineral content of the O‐horizons. In general, there were large differences between the plant communities of snowbed and willow‐shrub for several soil attributes. We concluded that 7 years of grazing had limited impacts on stocks, form and lability of SOM.     

Nutritional effects on sweetpotato storage root surface chemistry

Plant surface chemistry is known to have a pronounced effect on the behavior of many agriculturally important insects. We assessed the qualitative and quantitative effects of N and K nutrition on storage root surface chemistry of three sweetpotato [Ipomoea batatas (L.) Lam.] cultivars: two displaying moderate resistance (Jewel and Regal), and one susceptible (Centennial) to the sweetpotato weevil, Cylas formcarius (Summers). One field and one pot experiments were conducted, Boehmerol and boehmeryl acetate identified by GC‐MS were found on the surface of Centennial but not Jewel or Regal roots. Another compound, previously identified as “peak 4”;, was found on Regal with a retention time very close to that of boehmeryl acetate. In the field, boehmerol increased quadratically with increases in K rate (0, 112, or 224 kg K/ha); the same was true for boehmeryl acetate, but at 112 kg N/ha only. “Peak 4”; increased linearly (pot experiment) or quadratically (field experiment) with increases in the K rate, while N did not have a significant effect. Nutrition was found to affect storage root surface chemistry and may be a significant factor modulating differences in weevil susceptibility over location and time. The effect may in part explain inconsistencies in published estimates of field resistance to the weevil. Nitrogen and K nutrition should be taken into account when selecting progeny for boehmeryl acetate content in a breeding program.     

Freisetzung von Aluminium in mitteldeutschen sauren Braunerden aus Löß-Sandstein-Fließerden

Release of aluminium in Northwest-German Acid Brown soils on loess-sandstone solifluction deposits In soil and clay from root zones (50 resp. 80cm) of acid brown soils, the Si and Al released during weathering was determined by fractionated extraction with 0.5 N NaOH in order to arrive at a quantitative approximation of the possible clay and silicate destruction. Extracted Al was 4-10 times higher than Si, and showed a steep gradient between Ah- and B-horizon. The Al(clay)/Al(soil) ratio varied between 0.5 to 1 depending on the admixture of sandstone material to the loess. Assuming that the clay-extracted Al was derived from the destruction of clay, we arrived at a minimum value for affected clay of 1-4,5% of the soil mass or 10 to 40% of the present clay substance. Clay destruction is discussed as Al-release leaving behind a non-crystalline Si-O-OH lattice.     

Phosphorus speciation in cultivated organic soils revealed by P K‐edge XANES spectroscopy

Cultivated organic soils make a significant contribution to phosphorus (P) leaching losses from agricultural land, despite occupying a small proportion of cultivated area. However, less is known about P mobilisation processes and the P forms present in peat soils compared with mineral soils. In this study, P forms and their distribution with depth were investigated in two cultivated Histosol profiles, using a combination of wet chemical extraction and P K‐edge X‐ray absorption near‐edge structure (XANES) spectroscopy. Both profiles had elevated P content in the topsoil, amounting to around 40 mmol kg^?1, and P speciation in both profiles was strongly dominated by organic P. Topsoils were particularly rich in organic P (P‐org), with relative proportions of up to 80%. Inorganic P in the profiles was almost exclusively adsorbed to surface reactive aluminium (Al) and iron (Fe) minerals. In one of the pro‐files, small contributions of Ca‐phosphates were detected. A commonly used P saturation index (PSI) based on ammonium‐oxalate extraction indicated a low to moderate risk of P leaching from both profiles. However, the capacity of soil Al and Fe to retain P in organic soils could be reduced by high competition from organic compounds for sorption sites. This is not directly accounted for in PSI and similar indices. Accumulation of P‐org in the topsoil may be attributable by microbial peat decomposition and transformation of mineral fertiliser P by both microbiota and crops. Moreover, high carbon–phosphorus ratio in the surface peat material in both profiles suggests reduced net mineralisation of P‐org in the two soils. However, advancing microbial peat decomposition will eventually lead to complete loss of peat horizons and to mineralisation of P‐org. Hence, P‐org in both profiles represents a huge potentially mobilised P pool.     

Frozen storage effects on anthocyanins and volatile compounds of raspberry fruit

The quantitative and qualitative evolution of the anthocyanins and volatile compounds of four raspberry cultivars (cvs. Heritage, Autumn Bliss, Zeva, and Rubi) growing in Spain were analyzed raw, just frozen, and during long-term frozen storage at -20 degrees C for a 1 year period. HS-SPME coupled with GC-MS and HPLC techniques were employed to study the evolution of the volatile compounds and the individual anthocyanins, respectively. The volatile aroma composition changes produced by the freezing process and long-term frozen storage were minimal. Only a significant increase in extraction capacity was obtained for alpha-ionone (27%) and for caryophyllene (67%) in Heritage at 12 months of storage. The stability of anthocyanins to freezing and frozen storage depends on the seasonal period of harvest. Heritage and Autumn Bliss (early cultivars) were less affected by processing and long-term frozen storage (1 year), and the total pigment extracted showed the tendency to increase 17 and 5%, respectively. Rubi and Zeva (late cultivars) suffered a decreased trend on the total anthocyanin content of 4% for Rubi and 17.5% for Zeva. Cyanidin 3-glucoside most easily suffered the degradative reactions that take place during processing and the storage period.     

Management effects on soil C storage on the Canadian prairies

The Canadian prairie, which accounts for about 80% of Canada's farmland, has large reserves of soil organic carbon (SOC). Changes in the size of the SOC pool have implications for soil productivity and for atmospheric concentrations of CO₂, an important ‘greenhouse gas'. We reviewed recent findings from long-term research sites to determine the impact of cropping practices on SOC reserves in the region. From this overview, we suggest that: (1) the loss of SOC upon conversion of soils to arable agriculture has abated; (2) significant gains in SOC (typically about 3 Mg C ha⁻¹ or less within a decade) can be achieved in some soils by adoption of improved practices, like intensification of cropping systems, reduction in tillage intensity, improved crop nutrition, organic amendments, and reversion to perennial vegetation; (3) changes in SOC occur predominantly in ‘young' or labile fractions; (4) the change in SOC, either gain or loss, is of finite duration and magnitude; (5) estimates of SOC change from individual studies are subject to limitations and are best viewed as part of a multi-site network; and (6) the energy inputs into agroecosystems need to be included in the calculation of the net C balance. The long-term sites indicate that Canadian prairie soils can be a net sink for CO₂, though perhaps only in the short term. These sites need to be maintained to measure the effects of continued agronomic evolution and predicted global changes.     

Phosphorus speciation of forest‐soil organic surface layers using P K‐edge XANES spectroscopy

The phosphorus (P) speciation of organic surface layers from two adjacent German forest soils with different degree of water‐logging (Stagnosol, Rheic Histosol) was analyzed by P K‐edge XANES and subsequent Linear Combination Fitting. In both soils, ≈ 70% of the P was inorganic phosphate and ≈ 30% organic phosphate; reduced P forms such as phosphonate were absent. The increased degree of water‐logging in the Histosol compared to the Stagnosol did not affect P speciation.     

百合种球长期冷藏库的设计及应用效果

百合种球贮藏环境是根据百合种球生理特性所设计的,要达到这一要求,必须进行环境的合理布局,实现环境温度均衡、温差小、并保持较好的环境气体流动。因此,在冷库建设中,库内增设了内外气体交换系统,采用库顶中间均匀安装冷凝风扇设计,达到了双侧排风的效果,解决了通常冷库采用单侧面吹风所带来的库内温差较大,气流不均匀等问题。专用冷库的环境布局试验表明：通过CO2检测,控制库内气体交换,可使库内CO2 浓度维持在0.1%以内,各方位的温度差保持在≤±0.5℃,种球贮藏可达240 d,为百合种球贮藏创造了较为适宜的环境,实现了种球长期贮藏和调节花期的目的。     

Processing and storage effects on the ellagitannin composition of processed blackberry products

Changes in blackberry ellagitannin composition in response to juicing (clarified and nonclarified), pureeing, canning (in water or syrup), and freezing as well as changes in processed products during 6 months of storage were investigated. Canning, pureeing, and freezing had little effect on ellagitannins, but processing berries into nonclarified and clarified juices resulted in total ellagitannin losses of 70 and 82%, respectively, due to removal of ellagitannin-rich seeds in the presscake. Minimal changes in total ellagitannin content were observed during storage of thermally processed products, but compositional changes indicative of ellagitannin depolymerization were apparent. The ellagitannin content and composition of frozen berries remained stable over 6 months of storage. Ellagitannins are well retained in canned, pureed, and frozen blackberries, but methods are needed to prevent losses during juice processing and/or exploit the ellagitannin-rich coproducts.     

The effects of frozen storage conditions on lycopene stability in watermelon tissue

The purpose of this investigation was to evaluate the rate of deterioration of lycopene in watermelon tissue during frozen storage, because little is known about the stability of watermelon tissue lycopene under cold storage conditions. Heart tissue from each of nine individual watermelons was stored at -20 or -80 degrees C as either small chunks or puree and periodically sampled over a year's time. Initial freeze-thaw experiments indicated that a small percentage of lycopene, approximately 4-6%, degraded during an initial freeze-thaw. Analyses of the samples showed a loss of approximately 30-40% lycopene over a year's storage at -20 degrees C and a loss of approximately 5-10% over the same period at -80 degrees C. Lycopene was slightly more stable in pureed compared with diced watermelon tissue at -20 degrees C, but not at -80 degrees C. The kinetic data were best fitted by application of two simultaneous, first-order decay processes. HPLC analysis of the samples after a year's storage suggested that beta-carotene was more stable during storage at -20 degrees C than was lycopene.     

Processing and storage effects on orange juice aroma: a review

Freshly squeezed orange juice aroma is due to a complex mixture of volatile compounds as it lacks a specific character impact compound. Fresh hand-extracted juice is unstable, and thermal processing is required to reduce enzyme and microbial activity. Heating protocols range from the lightly heated not from concentrate, NFC, to the twice heated, reconstituted from concentrate, RFC, juices. Thermal processing profoundly effects aroma composition. Aroma volatiles are further altered by subsequent time-temperature storage conditions. Heating reduces levels of reactive aroma impact compounds such as neral and geranial, and creates off-flavors or their precursors from Maillard, Strecker, and acid catalyzed hydration reactions. Off-flavors such as 4-vinylguaiacol, p-cymene, and carvone are the products of chemical reactions. Other off-flavors such as butane-2,3-dione, guaiacol, and 2,6-dichlorophenol are indicators of microbial contaminations. Since most orange juice consumed worldwide is processed, the goal of this review is to summarize the widely scattered reports on orange juice aroma differences in the three major juice products and subsequent aroma changes due to packaging, storage, and microbial contamination with special emphasis on results from GC-O studies.     

Genetic evidence for speciation in <Emphasis Type="Italic">Cannabis</Emphasis> (Cannabaceae)

Sample populations of 157 Cannabis accessions of diverse geographic origin were surveyed for allozyme variation at 17 gene loci. The frequencies of 52 alleles were subjected to principal components analysis. A scatter plot revealed two major groups of accessions. The sativa gene pool includes fiber/seed landraces from Europe, Asia Minor, and Central Asia, and ruderal populations from Eastern Europe. The indica gene pool includes fiber/seed landraces from eastern Asia, narrow-leafleted drug strains from southern Asia, Africa, and Latin America, wide-leafleted drug strains from Afghanistan and Pakistan, and feral populations from India and Nepal. A third putative gene pool includes ruderal populations from Central Asia. None of the previous taxonomic concepts that were tested adequately circumscribe the sativa and indica gene pools. A polytypic concept of Cannabis is proposed, which recognizes three species, C. sativa, C. indica and C. ruderalis, and seven putative taxa.     

Rhizosphere reactions of Aluminium and manganese

Some aspects of the forms and reactions of Al and Mn in the rhizosphere of plants are discussed in relation to Mn availability and Al toxicity. The differences in behaviour between the two elements are sufficiently great that quite distinctly different procedures are required to estimate availability of Mn and toxicity of Al.