Changes in Chemical Structure and Biological Activity of L-DOPA as Influenced by an Andosol and Its Components

Velvetbean ( Mucuna pruriens ) has been reported to release 3-(3',4'-dihydroxyphenyl)-L-alanine (L-DOPA) as an allelochemical that inhibits the growth of other plants, although the inhibitory activity depends on the soil type and it is extremely reduced in Andosols. To clarify the effects of Andosols and their components on the chemical structure and plant-growth-inhibitory activity of L-DOPA, an L-DOPA solution was reacted with an Andosol and its components (weathered pumice and purified allophane), and the resultant solution was subjected to ¹H nuclear magnetic resonance and ultraviolet-visible spectral analyses, and plant-growth-inhibitory activity tests. When the L-DOPA solution was added to the soil components, the concentration of L-DOPA in the solution decreased by adsorption and transformation (polymerization) reactions. The adsorption mechanism included a ligand exchange reaction. The rate of L-DOPA transformation was faster at higher pH values. The soil components displayed a catalytic activity and accelerated the transformation of L-DOPA. Similar transformation occurred when light was irradiated. At pH values higher than 4.0, the transformed products from L-DOPA consisted of humic substances-like heterogeneous components, whereas specific components with low molecular weight were included when L-DOPA was transformed at a pH value of 9.7 or higher. The plant-growth-inhibitory activity of L-DOPA was extremely weakened when L-DOPA was adsorbed on or transformed (polymerized) by soil components. Therefore, in soils with high abilities of adsorption and transformation of L-DOPA such as in Andosols, it was likely that the L-DOPA concentration in the soil solution decreased quickly by adsorption and transformation reactions and the allelopathic activity of L-DOPA was lost.     

硼的吸附-解吸对土壤表面性质的影响

对三种不同类型土壤———棕红壤、黄棕壤、灰潮土在特定条件下的电荷零点(PZC) :ck—PZC(无硼 )、ads—PZC(硼吸附 )和des—PZC(硼解吸 )的研究发现 ,棕红壤和黄棕壤的ads—PZC与其ck—PZC相比 ,都有较为明显的下降。灰潮土 ,由于本身碳酸盐的缓冲作用 ,其ads—PZC与ck—PZC几乎相等。在硼吸附发生后 ,3种供试土壤的des—PZC较之它们的ads—PZC ,改变甚小 ,但这时灰潮土却保持强劲吸附电位离子的趋势 ,其吸附H 离子数量是棕红壤和黄棕壤的 2倍 ,表明在灰潮土上 ,原先被土壤胶体吸附的硼这时才显示利于电位离子的吸附。研究还表明 ,硼在酸性土壤中的吸附会引起 1 0倍量的质子的吸附     

Effect of Water Extract of Compost on the Adsorption of Arsenate by Two Calcareous Soils

The increasing mobility of arsenate will increase its leachingpotential to groundwater and uptake by plants. The mobility ofarsenate in soils is related to the competitive adsorption with other substances. The effect of organic substances on the adsorption of arsenate by soils was evaluated using the water extract of compost (WEC) as a complex anion source in a batch experiment. Two calcareous slate alluvial soils, Chiwulan andShuipientou, with higher arsenic contents of 23.7 and 12.9 mg kg^-1, respectively, were used. The Langmuir equation has been used to describe successfully the As adsorption isotherm for the two soils. The maximum adsorption of As was 6.098 and 4.785 μmol g^-1 for Chiwulan and Shuipientou soils, respectively. There was competitive adsorption for binding siteson the soils between arsenate oxyanions and organic anions derived from the dissolved organic carbon (DOC) of WEC. Differentcritical pH values were for arsenate addition related to arsenateadsorption on both soils in the absence of DOC of WEC but not inthe presence of DOC of WEC. The soil properties related to arsenate adsorption by the two soils may govern the critical pH values.     

Some factors affecting behaviour of boron in soil

It has been reported by many workers that various soil properties influence the retention of boron added to soils, but there is little infomration on the relative importance of these properties to boron retention and there is something controversial in the published results regarding the effects of different soil properties such as organic matter content, soil reaction, available calcium content and texture on boron retention (15). The present study was undertaken to obtain more detailed informations on the relationships between boron adsorption and different properties of soils, and on comparative contribution of soil constituents such as organic matter, sesquioxides and inorganic colloids to boron adsorption of soils. In Japan, boron deficiency symptoms of crops often appear in the fields of volcanic ash soils, and many experiments on boron application have been conducted to amend the boron deficiencies of the soils. It is considered that volcanic ash soils may have special characteristics concerning boron retention in comparison with nonvolcanic ash soils. In the present study, therefore, some volcanic ash soils were also taken as samples in addition to non-volcanic ash soils to confirm their speciality to boron retention.     

草酸对土壤和矿物中钾素的释放规律研究

Oxalic acid plays an important role in improving the bioavailability of soil nutrients. Batch experiments were employed to examine the influences of oxalic acid on extraction and release kinetics of potassium （K） from soils and minerals along with the adsorption and desorption of soil K^＋. The soils and minerals used were three typical Chinese soils, black soil （Mollisol）, red soil （Ultisol）, and calcareous alluvial soil （Entisol）, and four K-bearing minerals, biotite, phlogopite, muscovite, and microcline. The results showed that soil K extracted using 0.2 mol L^-1 oxalic acid was similar to that using 1 mol L^-1 boiling HNO3. The relation between K release （y） and concentrations of oxalic acid （c） could be best described logarithmically as y = a ＋ blogc, while the best-fit kinetic equation of K release was y = a ＋ b√t, where a and b are the constants and t is the elapsed time. The K release for minerals was ranked as biotite 〉 phlogopite 〉〉 muscovite 〉 microcline and for soils it was in the order： black soil 〉 calcareous alluvial soil 〉 red soil. An oxalic acid solution with low pH was able to release more K from weathered minerals and alkaline soils. Oxalic acid decreased the soil K^＋ adsorption and increased the soil K^＋ desorption, the effect of which tended to be greater at lower solution pH, especially in the red soil.     

黄河流域土壤研究——Ⅱ.华北平原土壤的发生和演变

华北平原的土壤过去尚无系统的研究。侯光炯等^[1]在河北省定期会进行土壤详测,将土壤划分为石灰性棕色土、镬土及冲积土等。     

MICROMORPHOLOGY OF SOILS DEVELOPED FROM VOLCANIC ASH AND RIVER ALLUVIUM IN THE KOKODA VALLEY, NORTHERN DISTRICT, PAPUA

Soils found on fan surfaces in the Kokoda Valley are derived from both volcanic ash and river alluvium. The alluvium is variable, some of it being mixed with volcanic ash. The main differences in the micromorphology of the soils appear to be related to the relative amounts of volcanic ash present in the soil profile. The plasma of soils formed on volcanic ash is isotropic in thin section. The plasma of alluvial soils exhibits increasing birefringence with decreasing amounts of volcanic ash. It is suggested that random structures in the clay fraction of the volcanic ash may account for its isotropic nature.     

Geochemical Fractionation and Adsorption Characteristics of Zinc in Thai Major Calcareous Soils

Zinc (Zn) is a vital plant nutrient that is widely deficient in Thai cultivated calcareous soils. The chemical fractionation and adsorption of Zn are among the most important solid- and liquid-phase interactions that determine the retention of Zn in the soils. This study aimed to investigate the fractionation and adsorption isotherms of Zn in cultivated Thai calcareous soils. The results of sequential extractions showed that Zn is mainly distributed in residual fractions followed by organic-bound, iron and manganese oxides-bound, carbonate-bound, and exchangeable Zn, respectively. Zinc adsorption was well fitted by the Langmuir and Freundlich isotherms. Thai calcareous soils had high Zn adsorption capacity. Soil pH, organic carbon, calcium carbonate, cation exchange capacity, and extractable calcium were the major soil properties that affected the Zn adsorption isotherms in these soils. Zinc hydroxide was the solid precipitate and the Zn hydroxide ion (ZnOH⁺) was the dominant Zn ion in alkaline equilibrium solution.     

Phosphate retention on soils in the central valley of Chile

The retention of phosphate and the content of available phosphate were estimated by a new method with monobasic sodium phosphate (pH 4.5) and the Olsen's method, respectively, on the Principal soils in the central valley in Chile. Trumaos (Andosols) are, in general, distinctly in the value of P-retention than other soils with the exception of trumaos of alluvial origins. This characteristic of trumaos can be employed for the identification of trumaos among r soils and alluvial trumaos among ordinary ones. The P-retention value of volcanic ash soils of decreases with the crystallization of the amorphous inorganic materials. According to the data of P-retention, certain rojos arcillosos (red clays) are presumed to have surface horizons of volcanic ash origins. Granitic rojos arcillosos are notably low in P-retention compared with other arcillosos. The organic matter content and P-retention value of soils are closely related to each other, suggesting that both organic matter and phosphate are retained by soils on the same a erials though by different mechanisms.

The content of available phosphate in surface horizons varied from soil to soil and no difference was noticeable among the soil groups of trumaos, rojos arcillosos, and paddy soils. Also no relation was found between the P-retention value and available phosphate content. However, in lower horizons where plant roots are scarce or absent, no available phosphate was found in trumaos in contrast to the presence of an appreciable amount of phosphate in rojos arcillosos. Phosphate of native trumaos appear to be practically insoluble. The surface soil rich in available phosphate was limited to cultivated fields, suggesting that the available phosphate was largely due to the remnant of applied fertilizers and partly to the remains of organic phosphorus from plants and soil organisms. The content of available phosphate tends to decrease with time after application of phosphates, and a significant negative correlation coefficient was obtained between the amount of available phosphate and the P-retention value of soils at least by three months after application of phosphate. The higher the P-retention value of soils, the less the content of available phosphate, and the faster the fixation of phosphate.     

土壤硼吸附热及温度对硼滞后解吸特性影响的研究

对棕红壤（９７０１）、黄棕壤（９７０２）和灰潮土（９７０３）在２５℃和４０℃条件下,硼吸附－解吸特性,土壤硼吸附热以及温度对土壤滞后解吸的影响进行了研究。结果表明,９７０１、９７０２和９７０３号土壤硼的吸附热分别为－１５．４、－１５．６和－２２．６ｋＪ／ｍｏｌ,处于化学吸附热的范围,从热力学上证明了硼在土壤上专性吸附的存在。与２５℃相比,４０℃时土壤硼滞后解吸得到加强。与此相应,施入土壤中的外源硼     

Chronology of anthropedogenesis in the Omiya tableland,Japan, based on a 14C age profile of humic acid

Volcanic ash soils along the western edge of the Omiya tableland, Japan, are covered with thick anthropogenic soil horizons. The formation of anthropogenic soil horizons occurs because of the soil dressing practice known as “Dorotsuke,” where alluvial soil materials are deposited on fields and mixed with volcanic ash topsoil by tillage over the years. To clarify the chronology of this anthropedogenesis, carbon-14 (¹⁴C) age profiles were estimated using humic acid fractions from three pedons: an anthropogenic soil, an undressed Andosol, and a Fluvisol. Soil charcoal fragments were also dated to estimate maximum burial age. Charcoal fragments displayed vertically random age distributions, indicating that the fragments may have had multiple origins. However, the age of charcoal in the lower part of the anthropogenic soil horizons indicated that the initiation of anthropedogenesis occurred later than the late 13th century. The ¹⁴C age profile of humic acid in the Andosol exhibited little variation in age with depth in the subsoil. The ¹⁴C age profile of humic acid in the Fluvisol suggested that the humic acid fraction included allochthonous old carbon (C), although the soil itself had been formed from recent sediments. The ¹⁴C age profile of humic acid in the anthropogenic soil showed features of its two component soils. The ¹⁴C ages in the volcanic ash subsoil matched with those in the Andosol, whereas the ages increased in the anthropogenic soil horizons because of supplementation with old C from alluvial soil materials. However, the peak ¹⁴C ages occurred in the lower part of the anthropogenic horizons, whereas the middle part on the peak position displayed a gradual age-depth gradient. This feature was interpreted as a sign of ¹⁴C activity equilibrium throughout anthropedogenesis. On the basis of this postulated ¹⁴C activity equilibrium, the linear age-depth gradient at the peak position was derived from differences in burial time, and burial ages were calculated by estimating steady-state ¹⁴C. The calculated ages were lower than the charcoal ages. These age estimates suggest that anthropedogenesis was initiated in the Middle Ages and reached an intermediate stage before or during the first half of the Edo period.     

酸化及施碳酸钙对土壤各形态锰的影响

以灰潮土为对照 ,研究了华中地区 3种已明显发生酸化的土壤在施用碳酸钙前后各形态锰的变化情况。结果表明 ,已酸化的红壤、棕红壤和黄褐土施用碳酸钙降低了土壤酸度 ,土壤交换态锰随 pH值上升而降低 ,其降幅分别为 42 % ,49%和 39% ;其它形态锰的增减随各土而异 ,残留态锰较稳定 ,变幅小。作为对照 ,灰潮土虽与前 3种已酸化土壤一样种植过多茬作物 ,但其交换态锰含量仍甚微。无论是否施用碳酸钙 ,在灰潮土的交换态锰、碳酸钙结合态锰和易还原态锰 3种形态锰中 ,易还原态锰占 80 %以上 ,说明易还原态锰是其活性锰的主要部分     

Comparison of Five Adsorption Isotherms for Prediction of Zinc Retention in Calcareous Soils and the Relationship of their Coefficients with Soil Characteristics

Abstract

Zinc (Zn) deficiency is believed to be a consequence of reactions taking place between soluble Zn and the soil solid phase. This study was carried out to obtain quantitative relationships between Zn in equilibrium solution and that retained by the soil solids in calcareous soils. Twenty calcareous soils (saturated paste pH 6.9–7.9; calcium carbonate equivalent 4.64–22.80%) from Tehran province, Iran, were equilibrated with varying solution concentrations of Zn, and the amounts removed from the solution were used to check the fit to five adsorption isotherms, namely, Freundlich, Langmuir, Temkin, Gunary, and two‐surface Langmuir. Adsorption data of all soils showed statistically significant fit to the first four adsorption isotherms, but only 7 of the 20 soils tested showed fit to the two‐surface Langmuir. Coefficients of the adsorption isotherms showed statistically significant relationship with soil characteristics. Clay percentage, calcium carbonate equivalent percentage, and cation exchange capacity appeared to be the most influential soil characteristics with regard to Zn adsorption, whereas soil organic matter seemed to be of no importance under the conditions of this study.     

The mineralization rate of black soil carbon in the deep layers of Japanese volcanic ash soil may be easily accelerated by labile carbon supply

ABSTRACT

The stability of black soil carbon in the deep layers of Japanese volcanic ash soil (i.e., buried A horizons) is often explained by its unique chemical (molecular structure) and physical (associated with short-range-order minerals) recalcitrance. However, the stability of black soil C in buried A horizons may be changed by labile C supply for soil microbes. Here, we hypothesized that the mineralization of black soil C in buried A horizons of Japanese volcanic ash soil could be easily accelerated by a supply of labile C (i.e., a priming effect; PE). To test our hypothesis, we investigated the direction and magnitude of the PE with a buried A horizon in Japan using ¹³C-labeled glucose (2.188 atom %) in a short-term (21 days) incubation study. We also investigated the effect of mineral nitrogen (N), which could contribute to microbial activity in this incubation study. We found that a positive PE occurred by glucose supply with (182%) or without (181%) mineral N input over the 21-day incubation, and its values were very similar to the PE ratios previously reported in other deep soils. The estimated mean residence time (MRT) of black soil C considering PE was clearly accelerated by glucose supply, regardless of mineral N input, compared with the initial soil MRT. These results strongly support our hypothesis that the mineralization rate of black soil C in buried A horizons is easily accelerated by a labile C supply, and it also demonstrates important implications for the effects of global warming on buried A horizons (e.g., increased root exudation, fine root biomass supply, and N deposition) in Japanese volcanic ash soils.     

紫色土可溶性有机碳的吸附-解吸特征

选择代表性的酸性、中性和石灰性紫色土为实验材料,采用平衡吸附和动力学吸附法研究了紫色土对可溶性有机碳（DOC）的吸附-解吸特征,分析了土壤理化性质与DOC吸附量之间的关系。结果表明,紫色土对DOC的吸附容量呈以下顺序：酸性紫色土〉中性紫色土〉石灰性紫色土。石灰性紫色土对DOC的解吸率明显高于酸性、中性紫色土,其迁移淋失问题值得重视。紫色土对DOC的吸附过程包括快速吸附和慢速吸附2个阶段,0~0.5 h内吸附速率最大,随后吸附速率逐渐减小,4~6 h内基本达到吸附平衡。土壤pH值、有机质、粘粒和活性铁铝氧化物含量是影响土壤DOC吸附量与解吸率的重要因素。通径分析表明,土壤理化性质对DOC吸附量的直接作用系数大小顺序为活性铝含量〉土壤pH值〉有机质,对DOC解吸率的直接作用系数大小顺序为活性铁含量〉粘粒〉有机质。多元线性回归模型能较好地预测土壤对DOC的吸附及解吸的变化。     

Addition of Calcareous Metal Waster to Acid Soils: Consequences for Metal Solubility

A model was tested which predicts the pH and solution metal concentration in the solution phase of soil amended with (waste-) incinerator fly ash (FA). Graded quantities of calcareous metal-rich FA were equilibrated with an acid clay soil, in aerated CaCl2 suspensions (0.01 M), to give a pH range of 3.1 (100% soil) to 7.5 (100% FA). As the FA loading was increased, the concentrations of Zn, Cd and Pb in solution passed through a maximum and then declined until the pH of the soil/ash mixtures approximated that of the pure FA (pHFA). This apparently complex pattern was accurately described by a simple pH- dependent adsorption equation relating adsorbed metal (Mads) to divalent metal concentration in solution (M2+) and pH through 3 constants designated n, Kads} and m: For pH < pHFA, log (Mads (M2+)n) = Kads + m pH However, at greater ash loadings the solution metal concentration and pH remained constant with FA addition and a solubility product (Ks) could be applied: For pH ≥ pHFA, og(M2+) = log Ks - 2 pH Metal concentrations in solution [Msoln] were greatest at very low FA loadings (around 2%); at lower FA additions [Msoln] was limited by total metal concentration while at higher additions of ash the solubility of metals was suppressed by the liming effect of the fly ash. It was therefore concluded that low levels of dust transfer from disposal sites to surrounding acidic soils may be the greatest source of metal pollution to biological and aquatic systems.     

Adsorption of silica in river waters by soils in central Chile

The adsorption of the silica in water by soils was investigated using principal river waters and soils collected in central Chile from about 34° to 41° south latitude. The adsorption of silica in water (y) was linearly proportional to the silica concentration in river waters (x) as shown by the following equation:

y=bx-a

where a and b were constants being subject to the nature of the soils. The silica contentration in river waters appeared to relate closely to the rocks in the catchment area. and was high in rivers from volcanic ash areas. However, the salt concentration had no correlation with the silica concentration, and tended to lower to the southward with an increase in annual precipitation and a decrease in annual mean temperature. Sulphate appreciably lowered the adsorption of silica by soils, although chloride and nitrate had little effect on the adsorption. The a-value, dissolution of silica in pure water, was the largest in paddy and alluvial soils, and both the a- and b-values were less in surface soils .in comparison with those of lower horizons. Soils caused neither adsorption nor dissolution of silica at a certain silica concentration. This silica zero adsorption concentration differed greatly from soil to soil, and the largest value which was observed in the surface soil of an irrigated paddy soil was so large that it could not adsorb silica from any river water in the central Chile. In contrast to this soil, an imogolitic subsoil of an Ando soil exhibited the highest adsorption concentration, i.e. it was possible to adsorb silica from every river water in the central Chile. Humus seemed to protect soil silica from dissolution and at the same time to prevent adsorption of silica by soils. Allophanic colloids were labile in water without humic-material, readily releasing silica into the water.     

Pesticide adsorptivity of aged particulate matter arising from crop residue burns

Particulates (ashes) arising from the burning of crop residues are potentially effective adsorbents for pesticides in agricultural soils. To determine the long-term adsorptive sustainability of ashes, a wheat (Triticum aestivum L.) ash was aged under environmentally relevant conditions (in CaCl(2) solution at room temperature and pH 7) in soil extract for 1 month and in a soil (1% ash) for a period of up to 12 months. The aged ash and ash-amended soil were used to sorb diuron from water. The diuron sorption was also measured in the presence of atrazine as a competing pesticide. There was no observed microbial impact on the stability of the wheat ash in soil. All isotherms with the ash were nonlinear type-I curves, suggestive of the surface adsorption. On a unit mass basis, the ash in soil extract was 600-10000 times more effective than the soil in sorbing diuron. Adsorption of dissolved soil organic matter (DOM) during aging on the ash surfaces reduced the diuron adsorption by 50-60%. Surface competition from the atrazine adsorption also reduced the ash adsorption of diuron by 10-30%. A total of 55-67% reduction in diuron sorption by the ash-amended soil was observed. Due to its high initial adsorptivity, the ash fraction of the aged ash-amended soil contributed >50% to the total diuron sorption. Thus, the wheat ash aged in the soil remained highly effective in adsorbing diuron. As crop residues are frequently burned in the field, pesticides in agricultural soils may be highly immobilized due to the presence of ashes.     

Effects of earthworms on Zn fractionation in soils

Laboratory incubation experiments were conducted to examine the effect of earthworm (Pheretima sp.) activity on soil pH, zinc (Zn) fractionation and N mineralization in three soils. No Zn uptake by earthworms was observed. Zinc addition decreased pH of red soil (soil 1) and hydragric paddy soil (soil 3) by 0.5 and 0.2 unit, respectively, but had no effect on alluvial soil (soil 2). The effect of Zn on soil pH was possibly due to a specific adsorption mechanism between Zn and oxides. Earthworm activity significantly decreased the pH of the red soil, a key factor affecting Zn solubility, but not of the other two soils. Earthworm activity significantly increased DTPA-Zn (DTPA-extractable) and OxFe-Zn (NH₂OH-HCl-extractable) in the red soil, but had little effect on other fractions. In the alluvial soil, earthworm activity significantly increased OxFe-Zn but decreased organic-Zn (organic-associated Zn). In the hydragric paddy soil, earthworm activity significantly increased MgCl₂-Zn (MgCl₂-extractable) and organic-Zn. The level of CaCl₂-extractable Zn in all three soils was not affected by earthworm activity. Nitrogen mineralized as a result of earthworm activity was equivalent to 110, 120 and 30 kg N ha^-1 in soils 1, 2 and 3, respectively. Zinc added at rates less than 400 mg Zn kg^-1 did not seem to affect the activity of N-mineralizing microorganisms. The present results indicated the possibility of increasing the metal bioavailability of relatively low level metal-contaminated soils, with a higher organic matter content, by earthworm inoculation.     

The influence of straw ash on some soil properties that can affect herbicide performance

During autumn 1982, soil samples were collected from 15 winter cereal fields in central and southern England. The soils either contained ash resulting from the burning of straw in the field or were ash free. Ash containing soils had much higher adsorption levels (measured as Kd values for chlortoluron) than ash-free soils. There were smaller differences in organic matter, pH and nutrient content between the 2 soil groups. There was a better correlation between adsorption and organic matter content for ash-free soils than for soils containing ash. The ratio of adsorption level to organic matter content for ash soils was almost twice that for ash-free soils. It was concluded that ash can make a substantial contribution to herbicide adsorption on minimally cultivated soils and that this could affect herbicide performance. In a tillage experiment where ploughing was followed by direct drilling, adsorption levels increased much more rapidly than organic matter.