The formation of spherical clay balls on the slopes of sandpit quarry,the Rudice-Seč (Czech Republic)

Clays on the steep slopes of a small artificial sedimentary basin (sandpit quarry) alternately desiccate/crack and erode during hot dry and rainy seasons, respectively. Small irregular blocks of clay (IBC) predefined by cracks are released by gully erosion. The IBCs are quickly transported to the slope base and then rolled down the basin bottom by runoff. Due to rotation about a randomly changing axis and under an effect of deformation forces, the IBCs are transformed into spherical clay balls (SCB). The SCBs are transported, in general, towards the depositional base where they are buried by assorted sandy/clayey sediment. As soon as the kinetic energy of the runoff has decreased, the SCBs remain spread along transport path. From their distribution, the shaping process was evaluated. Based on data processing, the dependency,relating the clay ball projection sphericity, ψ, to the effective diameter, d_ef, and to the distance from the steep slope base, λ, was found. Based on this equation, the length of clay ball transport can be estimated if the projection sphericity and effective diameter are known.     

800 years of mining and smelting in Kutná Hora region (the Czech Republic)—spatial and multivariate meta-analysis of contamination studies

Purpose

Kutná Hora was a centre of medieval mining and remains an important contamination source in the present day. Surprisingly, very little attention has been paid to the associated contamination. Although some studies have been performed, the majority of information regarding contamination is only accessible in the archives and no overview has been published. The purpose of this study is to perform a meta-analysis of all accessible data and to shed light on this topic.

Materials and methods

The data mainly come from analyses of HNO₃ solutions of sediments. We used statistical analyses (exploratory data analysis, PCA). The results were visualised and evaluated in the GIS environment.

Results and discussion

The complex of heavy metals As, Be, Cd, Co, Cr, Cu, Hg, Pb, V, and Zn can be divided into three main groups of different interpretation: (1) uninfluenced by mining activities—Be, Co, Cr, Hg, and V; (2) smelting processes—Cu, Pb, and Zn; and (3) mining—As and Cd. These groups also show different spatial distribution patterns, absolute concentration values and binding with different environmental types—landscape features.

Conclusions

The contamination of Kutná Hora can be characterised by element grouping and also by spatial diversification. This could be used in future research as a bearer of proxy information. Surprisingly, it also seems that the spatial range of contamination of sediments could be shorter than is generally presumed.

     

Isotopic Record of Lead Contamination in Alluvial Soils and Tree Rings on Recent Floodplains (Southern Québec, Canada)

Current and past industrial pollution leaves many traces in the environment, in particular along rivers in industrial and urban areas. The isotopic analysis of the lead found in soils and tree rings offers a kind of environmental archive for presenting a portrait of the pollutant distribution in the environment in both spatial and temporal terms. This study is an attempt to identify and compare the source of contamination found in soils and tree rings located along two rivers affected by pollution over several years. Specifically, the focus is on the pattern of lead concentrations and lead isotopic signatures (206Pb/207Pb, 208Pb/206Pb, and 206Pb/204Pb) detected in soils and tree rings located on polluted floodplains. The concentration of Pb in overbank sediments does not rise with the increasing distance downstream from the point source (mining area), suggesting that significant fluvial transport of the pollutant particles over 80 km is involved. For the soil profiles, Pb concentration levels range between 12.32 and 149.13 mg/kg, with the highest concentrations found at the base of the profiles (>1 m). For the lead isotope ratios in the soil profiles, the values obtained range from 0.851 to 0.872 (206Pb/207Pb), 2.081 to 2.111 (208Pb/206Pb), and 0.547 to 0.562 (206Pb/204Pb). The tree ring analysis of red ash (Fraxinus pennsylvanica Marsh.) shows average lead concentrations of 0.63 μg/g, and the lead values of all the tree specimens range between 0.03 and 11.38 μg/g. Pb concentrations varied greatly between the specimens in selected sites and lead isotope ratios in the tree rings showed a strong variability in the time series, particularly from 1945 to 1970. The greater number of variations in the lead concentration rates and isotopic ratios suggest that many more events associated with pollution and contamination have in fact occurred in this area. The study demonstrates the utility of combining stable isotope analyses (soils and tree rings) to examine the source and dispersion of contaminant Pb in fluvial systems by providing reliable and robust indicators for the detection of environmental changes on a local and regional scale.     

Effect of 2(N‐morpholino)ethane)sulfonic acid (MES) on the growth and tissue composition of cucumber

The effect of 2(N‐morpholino)ethane)sulfonic acid (MES) on the growth of cucumber (Cucumis sativa L. var. Marketer) in hydroponic culture was determined at 0, 1, 5, and 10 mM concentrations. The effect of adding the MES to the solution at the time of transfer to hydroponic culture or waiting one week was also determined. MES was observed to strongly affect plant growth with increasing concentration in nutrient solution. Tissue and nutrient solution analysis determined that MES affects manganese (Mn) uptake. MES appears to be reduced by Mn, precipitating the Mn out of solution. The suitability of MES as a pH buffer in hydroponic culture is discussed in terms of this effect.     

Effect of Fluoride Pollution on pH AND Solubility of Al,Fe, Ca,Mg, K and Organic Matter in Soil from Årdal (Western Norway)

The effect of fluoride (F) on pH and solubility of organic matter (TOC), aluminium (Al), iron (Fe), calcium (Ca), magnesium (Mg) and potassium (K) in soil samples collected near an aluminium smelter in Norway was studied. Increased addition of F to the soil samples led to an increase in pH and concentrations of TOC, Al and Fe in solution. Most of the F and Al in solution were in the forms of ALF_x-complexes. K solubility decreased in some soil samples, but there were no consistent effect on the solubility of Ca or Mg. The effect of NaF addition was significantly different from equimolar NaCl-treatments. The concentrations of Al, Fe, TOC and the pH-values were lower, while the concentrations of K, Mg and Ca were higher in the NaCl-treatments than in the NaF-treatments. The results from the experiment imply that F-pollution of soil induces breakdown of Al- and Fe-oxides/hydroxides and solubilize organic material in the soil. This may influence the availability of potentially toxic elements, such as AIF_x-complexes, to microorganisms and plant roots.     

Abiotic drivers and their interactive effect on the flux and carbon isotope (14C and δ13C) composition of peat-respired CO2

Feedbacks to global warming may cause terrestrial ecosystems to add to anthropogenic CO₂ emissions, thus exacerbating climate change. The contribution that soil respiration makes to these terrestrial emissions, particularly from carbon-rich soils such as peatlands, is of significant importance and its response to changing climatic conditions is of considerable debate. We collected intact soil cores from an upland blanket bog situated within the northern Pennines, England, UK and investigated the individual and interactive effects of three primary controls on soil organic matter decomposition: (i) temperature (5, 10 and 15 °C); (ii) moisture (50 and 100% field capacity – FC); and (iii) substrate quality, using increasing depth from the surface (0–10, 10–20 and 20–30 cm) as an analogue for increased recalcitrance of soil organic material. Statistical analysis of the results showed that temperature, moisture and substrate quality all significantly affected rates of peat decomposition. Q₁₀ values indicated that the temperature sensitivity of older/more recalcitrant soil organic matter significantly increased (relative to more labile peat) under reduced soil moisture (50% FC) conditions, but not under 100% FC, suggesting that soil microorganisms decomposing the more recalcitrant soil material preferred more aerated conditions. Radiocarbon analyses revealed that soil decomposers were able to respire older, more recalcitrant soil organic matter and that the source of the material (deduced from the δ¹³C analyses) subject to decomposition, changed depending on depth in the peat profile.     

Structure-activity relationships of α-, β(1)-, γ-, and δ-tomatine and tomatidine against human breast (MDA-MB-231), gastric (KATO-III), and prostate (PC3) cancer cells

Partial acid hydrolysis of the tetrasaccharide (lycotetraose) side chain of the tomato glycoalkaloid α-tomatine resulted in the formation of four products with three, two, one, and zero carbohydrate side chains, which were separated by high-performance liquid chromatography (HPLC) and identified by thin-layer chromatography (TLC) and liquid chromatography ion-trap time-of-flight mass spectrometry (LCMS-IT-TOF). The inhibitory activities in terms of IC(50) values (concentration that inhibits 50% of the cells under the test conditions) of the parent compound and the hydrolysates, isolated by preparative HPLC, against normal human liver and lung cells and human breast, gastric, and prostate cancer cells indicate that (a) the removal of sugars significantly reduced the concentration-dependent cell-inhibiting effects of the test compounds, (b) PC3 prostate cancer cells were about 10 times more susceptible to inhibition by α-tomatine than the breast and gastric cancer cells or the normal cells, (c) the activity of α-tomatine against the prostate cancer cells was 200 times greater than that of the aglycone tomatidine, and (d) the activity increased as the number of sugars on the aglycone increased, but this was only statistically significant at p < 0.05 for the normal lung Hel299 cell line. The effect of the alkaloids on tumor necrosis factor α (TNF-α) was measured in RAW264.7 macrophage cells. There was a statistically significant negative correlation between the dosage of γ- and α-tomatine and the level of TNF-α. α-Tomatine was the most effective compound at reducing TNF-α. The dietary significance of the results and future research needs are discussed.     

Effect of herbicide used with years (8 + 1) on soil enzymic activity and microbial population diversity

Purpose

Soil microbes play important roles in plant nutrition and soil conservation, and the diversity and population of soil microbe are influenced by abiotic and biotic factors associated with different soil managements. However, the information concerning soil microbe diversity and population structure and its relation with soil fertility and enzyme activities are scarce in crop rotation under different soil management system.

Materials and methods

This paper reports the effects of three weeding managements (herbicide (2-chloro-N-(ethoxymethyl)-N-(2-ethyl-6-methylphenyl) acetomide, C1₄H₂₀ClNO₂), manual weeding, and no weeding (CK)), on soil microbial diversity, population structure, and its relationship with soil active organic matter (AOM) and pH, and the activity of soil enzymes like sucrase, catalase, and urease activities from long-term test area in red soil upland field in southeast China, which was set up since 2006. Soil samples at 0–20-cm depths were collected before (8 years) and after (8 + 1 years) weeding management in April 2014.

Results and discussion

Soil enzymes (sucrase, catalase, and urease activity) and soil microbial populations had no significant difference (P > 0.05) under the three weeding treatments. Based on richness of microbial population up to 0.10%, the phyla Proteobacteria and Actinobacteria highly dominated the three soil treatments, averagely accounting for 21.76 and 21.44%. Chloroflexi was the next phylum, about accounting for 6.84%. Firmicutes, Verrucomicrobia, and Planctomycetes phylum accounted for 4.98, 4.78, and 4.23%, respectively. The percentage of Gemmatimonadetes was 2.76%, and that of Bacteroidetes was about 1.45%. Armatimonade and Nitrospira were the lowest, with 0.69 and 0.26%, respectively. Among the 20 phyla, only 5 had significant correlation with some of the soil properties. Twenty-one in 46 classes had significant correlation with some of the soil properties. Armatimonadetes and Fusobacteria had positive correlation with moisture. Acidobacteria_Gp3, Deltaproteobacteria, Chthonomonadetes, Armatimonadetes_gp4, and Euryarchaeota also were positively correlated with moisture. Negative correlation between Armatimonadetes, Chloroflexi, Chthonomonadetes, and Armatimonadetes_gp5 and AOM exists, and Armatimonadetes, Chthonomonadetes, Clostridia, Armatimonadetes, and pH were negatively correlated. Fusobacteria was positively correlated with catalase. Acidobacteria_Gp10 and Armatimonadia were positively correlated with catalase. Chthonomonadetes, Clostridia, and Armatimonadetes_gp5 were correlated with urease. Gammaproteobacteria and Flavobacteria were correlated with sucrase.

Conclusions

For long-term herbicide experiment conducted on the Dongxiang upland site, no significant effect of herbicide on soil microbial community composition and enzyme activities was found. Further work is needed to relate microbial community structure and function in different herbicide systems or season sampling, even to detect herbicide effect on community structure during the growing season.

     

Impact of high-pressure processing on vitamin E (α-, γ-, and δ-tocopherol), vitamin D (cholecalciferol and ergocalciferol), and fatty acid profiles in liquid foods

In the present study, four high-pressure (HP) treatments (100, 200, 300, and 400 MPa) of 9 min duration were evaluated to assess their effect on the lipid fraction (fat-soluble vitamins and fatty acid profile) of an orange juice-milk and a vegetable beverage. After HP treatment, nonsignificant changes in vitamin D(2) and D(3) contents were observed for both beverages. An increase in vitamin E activity was observed in HP beverages when pressures >100 MPa were applied, mainly due to an increase in α-tocopherol content. Only a small reduction in fat content was found for the orange juice-milk beverage, but no changes were observed for the vegetable beverage. A significant decrease in SFA levels was observed in HP-treated (300-400 MPa) orange juice-milk. With regard to MUFA, a significant increase in oleic acid (C(18:1)) was found in both liquid foods. Nonsignificant differences in the PUFA profiles were observed after HP processing.     

Abiotic drivers and their interactive effect on the flux and carbon isotope (C and δC) composition of peat-respired CO2

Feedbacks to global warming may cause terrestrial ecosystems to add to anthropogenic CO₂ emissions, thus exacerbating climate change. The contribution that soil respiration makes to these terrestrial emissions, particularly from carbon-rich soils such as peatlands, is of significant importance and its response to changing climatic conditions is of considerable debate. We collected intact soil cores from an upland blanket bog situated within the northern Pennines, England, UK and investigated the individual and interactive effects of three primary controls on soil organic matter decomposition: (i) temperature (5, 10 and 15 °C); (ii) moisture (50 and 100% field capacity – FC); and (iii) substrate quality, using increasing depth from the surface (0–10, 10–20 and 20–30 cm) as an analogue for increased recalcitrance of soil organic material. Statistical analysis of the results showed that temperature, moisture and substrate quality all significantly affected rates of peat decomposition. Q₁₀ values indicated that the temperature sensitivity of older/more recalcitrant soil organic matter significantly increased (relative to more labile peat) under reduced soil moisture (50% FC) conditions, but not under 100% FC, suggesting that soil microorganisms decomposing the more recalcitrant soil material preferred more aerated conditions. Radiocarbon analyses revealed that soil decomposers were able to respire older, more recalcitrant soil organic matter and that the source of the material (deduced from the δ¹³C analyses) subject to decomposition, changed depending on depth in the peat profile.     

Effect of inhibitor compounds on Nε-(carboxymethyl)lysine (CML) and Nε-(carboxyethyl)lysine (CEL) formation in model foods

The possible adverse effects on health of diet-derived advanced glycation endproducts (AGEs) and advanced lipoxidation endproducts (ALEs) is of current interest. This study had the objective of determining the effects of the addition of AGE/ALE inhibitors and different types of sugar and cooking oil on Nε-(carboxymethyl)lysine (CML) and Nε-(carboxyethyl)lysine (CEL) formation in model foods (sponge cakes). The cake baked using glucose produced the highest level of CML (2.07±0.24 mmol/mol lysine), whereas the cake baked using fructose produced the highest concentration of CEL (25.1±0.15 mmol/mol lysine). There were no significant differences between CML concentrations formed in the cakes prepared using different types of cooking oil, but significant differences (P<0.001) were observed between the cakes prepared using different proportions of cooking oil. The cakes containing oil generated greater concentrations of CML than sucrose. α-Tocopherol and rutin did not inhibit CML and CEL formation. In contrast, ferulic acid and thiamin, thiamin monophosphate, and thiamin pyrophosphate reduced CML and CEL formation.     

Effect of seed‐placed fertilizer on the emergence (germination) of soybeans (Glycine max L.) and snapbeans (Phaseolus vulgaris L.)

Abstract

Field trials were established on a loamy fine sand and a silt loam using snapbeans and soybeans as test crops, respectively. Row fertilizer was placed with the seed (seed‐placed). Treatments were arranged in a 3×3×3 factorial experiment, and N, P, and K were applied in all combinations at three rates (0, 3.4, and 6.8 kg/ha). Ammonium nitrate (AN), monoammonium phosphate (MAP), concentrated superphosphate (CSP) and potassium chloride (KCl) were used as sources of N, P and K. Additional treatments compared MAP with diammonium phosphate (DAP) and KCl with potassium nitrate (KNO₃).

The salt index of each treatment was inversely related to emergence, i.e. as the salt index increased, the emergence decreased. Level of N was more important than level of P or K in regards to reduction in emergence. Snapbeans grown on a loamy fine sand were extremely sensitive to damage from seed‐placed fertilizer, even at rates as low as 3.4 kg/ha of N, P or K. Soybeans planted on a silt loam soil were less sensitive than snapbeans planted on a loamy sand. The soybeans were able to tolerate up to 10.2 kg/ha of seed‐placed P plus K or 6.8 kg/ha of seed‐placed N plus P or N plus K without causing a significant delay in emergence.     

Effect of nutrient management and straw mulching on crop yield,uptake and soil fertility in rapeseed (Brassica campestris)–greengram (Vigna radiata)–rice (Oryza sativa) cropping system under Gangetic plains of India

An experiment was conducted at Bidhan Chandra Krishi Viswavidyalaya, West Bengal, India during 2001–2003 to study the effect of levels of fertility and straw mulch on a rapeseed (Brassica campestris var yellow sarson)–greengram (Vigna radiata)–rice (Oryza sativa) cropping system under a rainfed upland ecosystem. The experiment was laid out in a split-plot design having 14 treatment combinations of organic and inorganic nutrients along with straw mulch in three replicates. The results revealed that conjunctive use of organic and inorganic nutrients as well as paddy straw mulch resulted higher yield in both rapeseed and greengram, and the residual effects of different levels of fertilization and mulching also gave rise to higher grain yield in the succeeding rice crop. The uptake of nutrients, by the cropping system as a whole, to the tune of 204.29 and 183.00 kg ha^?1 of N, 72.84 and 74.07 kg ha^?1 of P and 179.95 and 175.41 kg ha^?1 of K took place, with the treatment receiving 10 t ha^?1 of farmyard manure (FYM) applied (to rapeseed) along with 50% recommended dose (RD) of NPK to all the crops in the sequence in two consecutive years, respectively. The same treatment resulted in a higher percentage of porosity vis-à-vis lower bulk density. Soil physico-chemical properties were superior in mulch-treated plots compared with no mulch treatment. Application of organic and inorganic nutrients along with proper moisture conservation practices can enhance the yields maintaining a good soil health.     

The influence of lithology on hillslope development in the area of the Jacupiranga Alkaline Complex and its surroundings (São Paulo,Brazil)

The area of the Jacupiranga Alkaline Complex and its surroundings is characterized by a variety of slope forms. Their spatial differentiation and the differences in relative relief and hilltop heights are a function of lithology. Significant contrasts exist, particularly between the ultramafic rocks of the Alkaline Complex and the quartz-rich rocks of the surrounding Precambrian basement. Although climatic conditions are uniform, the physical and chemical properties of the weathering products formed on the various rock types are very different. Through their properties, they affect the hillslope processes and thereby influence the hillslope development. Slope-forming processes on deeply weathered ultramafic rocks are slow mass movements and chemical denudation. On the more resistant ultramafic rocks, wash processes appear to be more important. Wash and rapid mass movements predominate on gneisses, granites and mica schists.The geomorphological development of the Jacupiranga Alkaline Complex can be explained in terms of a long, continuous downwearing. The large differences in elevation within the Alkaline Complex suggest that the development towards a more differentiated relief may extend well back into the Tertiary. The mutual adjustment of slope forms, processes and lithological controls favoured the development of rock-dependent summit heights, where heights are determined by the steepness of the slopes and the spacing of the drainage lines. Climatic fluctuations in the Pleistocene failed to produce any fundamental change in the long-term development of the hillslopes as their duration was too short with respect to the relaxation time of the hillslopes or their influence was not great enough to alter the overall trend of slope development.     

Influences of ultra‐violet (UV)‐blue light radiation on the growth of cotton. I. Effect on iron nutrition and iron stress response

Cool white fluorescent (CWF) light reduces Fe³⁺ to Fe²⁺ while low pressure sodium (LPS) light does not. Cotton plants grown under CWF light are green, while those yrown under LPS light develop a chlorosis very similar to the chlorosis that develops when the plants are deficient in iron (Fe). It could be that CWF light (which has ultra violet) makes iron more available for plant use by maintaining more Fe²⁺ in the plant. Two of the factors commonly induced by Fe‐stress in dicotyledonous plants‐‐hydroyen ions and reductants released by the roots‐‐were measured as indicators of the Fe‐deficiency stress response mechanism in M8 cotton.

The plants were grown under LPS and CWF light in nutrient solutions containing either NO₃‐N or NH₄‐N as the source of nitrogen, and also in a fertilized alkaline soil. Leaf chlorophyll concentration varied significantly in plants grown under the two light sources as follows: CWF+Fe > LPS+Fe > CWF‐Fe ≥ LPS‐Fe. The leaf nitrate and root Fe concentrations were significantly greater and leaf Fe was generally lower in plants grown under LPS than CWF light. Hydrogen ions were extruded by Fe‐deficiency stressed roots grown under either LPS or CWF light, but “reductants”; were extruded only by the plants grown under CWF light. In tests demonstrating the ability of light to reduce Fe³⁺ to Fe²⁺ in solutions, enough ultra violet penetrated the chlorotic leaf of LPS yrown plants to reduce some Fe³⁺ in a beaker below, but no reduction was evident through a yreen CWF grown leaf.

The chlorosis that developed in these cotton plants appeared to be induced by a response to the source of liyht and not by the fertilizer added. It seems possible that ultra violet liyht could affect the reduction of Fe³⁺ to Fe²⁺ in leaves and thus control the availability of this iron to biological systems requiring iron in the plant.     

Interactive effects of Si and NaCl on growth,yield, photosynthesis,and ions content in strawberry (Fragaria × ananassa var Camarosa)

The effects of silicon (Si) (0, 1, and 2 mM) and sodium chloride (NaCl) salinity (0, 20, and 40 mM) on the yield, photosynthesis, and ion content in strawberry grown in hydroponics were investigated. Salinity caused a reduction in leaf area and plant biomass, regardless of Si supplement. Leaf area in Si₁Na₂₀ treatment was 37% higher than that of Si₀Na₂₀ treatment. Salinity at 20 mM concentration had a 25% yield reduction in absence of Si, corresponding to no reduction in the yield in the presence of Si compared with the Si treatment without salinity. The highest reduction of photosynthetic rate (Pn) was observed in Si₁Na₄₀ treatment; however, in the presence of Si, there was no reduction in the Pn rate at 20 mM NaCl concentration. An obvious positive relationship was found between potassium/sodium (K/Na) and Pn rate. Within each Si concentration, the increased salinity increased Na concentration in the leaf tissue. However, when Si was supplied to the salinity treatments Na concentration was significantly lower than that of the similar treatments without Si. Supplement of Si to the nutrient solution increased the Si concentration in the roots, and old and young leaves. A clear negative relationship (r² = 0.71) was found between Si and Na concentration in the leaves. Salinity (NaCl₄₀) increased the proline level 2.5-fold in the absence of Si, corresponding to no changes the proline level in the presence of 1 mM Si concentration compared with the Si treatment without salinity. The salinity (40 mM) increased the electroleakage by 50% compared with 0 mM NaCl treatment in the absence of Si supplement. Findings from this study lead to the conclusion that Si supplement to the nutrient solution ameliorated the deleterious effect of salinity on the strawberry growth; these effects were attributed to an enhanced K/Na ratio and the reduction in Na content and electroleakage ability in the leaf tissue.     

The effect of concentrations and properties of phenanthrene, pyrene, and benzo(a)pyrene on desorption in contaminated soil aged for 1 year

Purpose

The choice and timing of microorganisms added to soils for bioremediation is affected by the dominant bioavailable contaminants in the soil. However, changes to the concentration of bioavailable PAHs in soil are not clear, especially when several PAHs coexist. This study investigated the effects of PAH concentration and chemical properties on desorption in meadow brown soil after a 1-year aging period, which could reflect changes of PAH bioavailability during bioremediation.

Materials and methods

Based on the percentage of different molecular weights in a field investigation, high-level contaminated soil (HCS) and low-level contaminated soil (LCS) were prepared by adding phenanthrene (PHE), pyrene (PYR) and benzo(a)pyrene (BaP) to uncontaminated meadow brown soil. The concentrations of HCS and LCS were 250 mg?kg^?1 (PHE, PYR, and BaP: 100, 100, and 50 mg?kg^?1) and 50 mg?kg^?1 (PHE, PYR, and BaP: 20, 20, and 10 mg?kg^?1) respectively. The soils were aged for 1 year, after which desorption was induced by means of a XAD-2 adsorption technique over a 96-h period.

Results and discussion

The range of the rapidly desorbing fraction (F _rap) for PHE, PYR, and BaP in HCS and LCS was from 1.9 to 27.8 %. In HCS, desorption of PYR was most difficult, and the rate constant of very slow desorption (K _vs) of PYR was 8 orders of magnitude lower than that of BaP, which had similar very slow desorbing fractions (49.8 and 50.5 %, respectively). However, in LCS, desorption of PYR was the easiest; the K_vs of PYR was 8–10 orders of magnitude higher than those of PHE and BaP. In HCS, the time scale for release of 50 % of the PAHs was ranked as BaP?>?PYR?>?PHE, while in LCS this was BaP?>?PHE?>?PYR.

Conclusions

The combined effect of PAH concentrations and properties should be taken into account during desorption. The desorption of PAH did not always decrease with increasing molecular weight, and the desorption of four-ring PAHs might be special. These results are useful for screening biodegrading microbes and determining when they should be added to soils based on the dominant contaminants present during different periods, thus improving the efficiency of soil bioremediation.     

Effect of MES [2(N‐morpholino)ethanesulfonic acid] and amberlite IRC‐50 resin on nutrient pH control and soybean growth

The relative effectiveness of Amberlite IRC‐50 resin, in a recirculating ion exchange column, and several concentrations of MES [2(N‐mor‐pholino)ethanesulfonic acid] were evaluated for control of nutrient solution pH of hydroponically cultured soybean (Glycine max [L.] Merr. cv Williams). A low buffering capacity, urea‐based nutrient solution was used. MES buffer, at the concentrations evaluated (1,2, 4, and 10 mM), was less effective at maintaining desired pH than the IRC‐50 resin system. The pH of the 4.0 mM MES buffered nutrient solution decreased from 6.5 to below 4.0 in five days with 25 to 30 day old plants. By comparison, the pH of the IRC‐50 resin buffered nutrient solution dropped from 6.5 to 5.9 during the same period. Nitrate uptake by 27 to 29 day‐old plants was significantly slower when solutions were buffered with MES than with IRC‐50 resin. Rate of nitrate uptake decreased with increasing MES buffer concentrations and decreasing pH in short‐term studies on plants previously grown on IRC‐50 resin buffered nutrient solution. Mass of the plants grown on IRC‐50 resin buffered nutrient solution equaled or exceeded that of plants grown on 1, 2, or 4 mM MES. Total elemental uptake (mg/plant) by plants grown on nutrient solution buffered by IRC‐50 resin, for the ten elements tested, was equal to or greater than uptake by plants grown on nutrient solution buffered by 1, 2, or 4 mM MES. It is concluded that IRC‐50 resin in recirculating columns provides better pH control than does MES buffer for hydroponically grown soybean.