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     

土壤酸化与油菜锰毒关系研究

对湖北省的主要旱地土壤种植多茬作物后的油菜生产锰毒的原因进行了研究,结果供试土壤ＰＨ值较原土样下降了１．０个单位。除石灰柱土壤外,其它中酸性土壤交换性锰明显增加,造成油菜对锰吸收过量,同时由于吸收过程中锰铁拮抗作用的存在,植株在土壤锰毒发生后吸上的铁量下降。使体内锰铁比上升。     

变动氧化还原状况下酸性土壤中活性锰的变化

锰是一种常见的变价元素,其在土壤中的有效性主要依赖于土壤总锰量、pH、有机质含量、通气状况及微生物活性等,其中,最直接的是土壤通气状况和pH。自20世纪50年代以来,渍水土壤中锰的化学行为及移动性就引起了人们的关注[1~7]。在自然状态下,锰以多种氧化物形式存在,Mn(Ⅲ)和Mn(Ⅳ)发生在氧化环境中,Mn2+主要存在于还原条件下,土壤体系中的氧化还原状况显著地影响着土壤锰的溶出和生物有效性。到目前为止,有关土壤pH、Eh和Mn2+的关系研究的较少。1970年,Bohn[8]通过测定土壤pH、Eh和全锰含量预测了土壤悬浮液中Mn2+的含量。刘鑫等[9]运用能斯特方程式研究了盆栽土壤pH、Eh和     

黄土高原旱地连续施用锰肥的土壤效应研究

采用连续浸提形态分级方法，研究了连续施用锰肥17a后锰的土壤化学特性变化。结果表明：经过长期连续施用锰肥，土壤全锰和DTPA—Mn含量增加不多。土壤DTPA—Mn含量随试验时间的延长呈增加趋势，施锰土壤有效锰提高不多，土壤DTPA—Mn含量只增加了0．4～1．7mgkg^-1。土壤中的锰主要以矿物态存在，占土壤全锰含量的比例为87．3％～91.8％。碳酸盐态、氧化锰态和紧结有机态锰占全锰的比例相当，土壤中各形态锰按含量大致呈矿物态〉碳酸盐态〉氧化锰态〉紧结有机态〉松结有机态〉交换态的顺序。施入土壤的锰肥有91．1％～98．6％进入碳酸盐结合态、氧化锰结合态、紧结有机态和矿物态，只有很少一部分仍留在有效态锰库中。交换态和松结有机态锰对土壤锰的有效性起着主要作用，可以反映土壤锰的供给状况，碳酸盐态和紧结有机态锰不能反映土壤锰的有效性。     

碳酸钙和硼对棕红壤油菜锰毒缓解作用

对已酸化的棕红壤进行的油菜锰毒缓解研究表明,施用碳酸钙在提高土壤ＰＨ和降低土壤交换性锰的基础上,改善了土壤营养状况,其中施用０．５％碳酸钙处理的效果最好,在这一碳酸钙水平下,土壤硼处于较高的活性,土壤速效钾被油菜幼苗充分利用,油菜幼苗对营养元素具有最大吸收量,使植株生物学产量达到最大值。酸化的棕红壤只需施用０．５％的碳酸钙,其土壤酸碱度便可恢复到正常鲨和更多的碳酸钙。会造成土壤营养再度失调,油菜轩     

电动模拟土壤酸化及其交换性离子组成变化

土壤酸化及其环境效应研究是土壤环境领域的重要内容。自行设计了模拟土壤酸化的电动装置,该装置由直流电源、反应槽、石墨电极组成,并采用四种不同类型土壤,研究了电动模拟土壤酸化后土壤pH、交换性酸和交换性阳离子组成的变化。实验结果显示,经电动处理后土壤pH发生明显变化,土壤pH由阳极到阴极逐渐升高,pH变幅为水稻土燥红土红壤赤红壤,水稻土的pH变化比红壤更为明显;土壤交换性H+和Al~(3+)含量在阳极附近最高,交换性Al~(3+)占交换性酸总量达65%以上;交换性Ca~(2+)、Mg~(2+)、K~+和Na~+表现出离阳极越远,含量越大的规律,其中交换性Ca~(2+)和Mg~(2+)在模拟酸化后含量变化较大,而交换性K~+和Na~+的变化幅度相对较小。结果表明,电动处理可快速获得不同pH梯度的土壤样品,并模拟了土壤酸化过程中的阳离子迁移过程,是模拟土壤酸化及其效应研究的有效方法。     

河北主要土壤中Cd和Pb的形态分布及其影响因素

采用网室盆栽试验和大田取样 ,运用连续提取方法 ,研究了河北平原潮土和潮褐土两种土壤中Cd、Pb的化学形态特征及与其影响因素的关系。结果表明 :随着Cd、Pb污染程度的增加 ,其交换态有增加趋势。当高浓度重金属污染土壤时 ,Cd(潮土 >1mgkg- 1、潮褐土 >5mgkg- 1)主要以交换态存在 ,并表现为 :交换态 >碳酸盐结合态 >铁锰氧化物结合态 >有机结合态 >残留态 ;Pb主要以碳酸盐结合态和铁锰氧化物结合态存在。在低浓度重金属污染的土壤中 ,Cd (潮土 <1mgkg- 1、潮褐土 <5mgkg- 1)的残留态、有机结合态成倍增加 ,甚至超过交换态 ,表现为 :残留态 >碳酸盐结合态 >有机结合态 >交换态 >铁锰氧化物结合态 ;Pb主要以铁锰氧化物结合态和残留态存在。Cd、Pb在土壤中的分布与土壤的pH值 ,有机质含量密切相关。     

土壤营养元素吸附特性指导中,酸性土壤施肥的研究

根据供试土壤营养元素吸附特性进行的幼苗试验和盆栽试验的结果表明，在满足氮、钾、钙、镁、硫等营养元素基础上，对鄂中黄棕壤、鄂南棕红壤和湘中红壤以ＡＳＩ法确定有效磷临界值三倍（４２ｍｇ／ｋｇ）水平对三种土壤施入的磷分别为２２０、１２５和２１０ｍｇ／ｋｇ，高梁生物幼苗产量均最高，用幼苗试验和盆栽试验的结果指导田间试验时，施磷后使供试土壤可浸提有效磷达到１５－２５ｍｇ／ｋｇ水平，油菜产量最高。     

海南岛砖红壤中铅、镉的化学形态与转化

采用土培实验和连续提取.原子吸收分光光度法,研究了重金属Pb、Cd在海南岛花岗岩砖红壤中的形态组成、外源Pb、Cd污染及化学修复剂磷、钙、硫对土壤重金属形态的影响.结果表明:在供试原土壤中,重金属Pb的化学形态以结合态和残余态为主,土壤有效态Pb含量较低,其中残余态Pb>有机质结合态Pb>铁锰氧化物结合态Pb>碳酸盐结合态Pb>交换态Pb>水溶态Pb,说明土壤Pb的环境风险较低;重金属Cd的化学形态以铁锰氧化物结合态和碳酸盐结合态为主,土壤中交换态Cd含量较高,其中铁锰氧化物结合态Cd>碳酸盐结合态Cd>交换态Cd>有机结合态Cd>残余态Cd>水溶态Cd,说明土壤Cd的环境风险较高.当外源Pb、Cd污染土壤时,有铁锰结合态Pb>残余态Pb>有机态Pb>碳酸盐结合态Pb>交换态Pb>水溶态Pb,交换态Cd>铁锰氧化物结合态Cd>碳酸盐结合态Cd>残余态Cd>有机态Cd>水溶态Cd的趋势.向污染土壤施加化学改良剂过磷酸钙、硫化钠和石灰,能显著降低水溶态Pb、Cd和交换态Pb、Cd的含量,并使有机结合态Pb、碳酸盐结合态Pb和铁锰氧化物结合态Pb含量下降,但残余态Pb、碳酸盐结合态Cd、铁锰氧化物结合态Cd和有机态Cd有增加的趋势,残余态Cd的含量基本稳定.     

生物炭对红壤和褐土中镉形态的影响

【目的】重金属对环境危害的大小主要取决于其形态分布,尤其是生物有效态镉 (Cd) 的含量和存在比例。添加生物炭可以降低Cd超标土壤中生物有效态Cd的含量,本文研究了施用生物炭后红壤和褐土中Cd形态的变化及其与生物炭施用量的关系,以加深对生物炭修复Cd污染土壤机理的认识。【方法】选择红壤 (pH 5.21) 和褐土 (pH 7.75) 两类土壤进行了室内培养试验。将两个过2 mm筛的自然风干土壤各40 kg,分别装于20 L塑料盒中,加Cd(NO₃)₂溶液使土壤外源Cd含量达到5 mg/kg,保持70%田间最大持水量,于25℃条件下平衡两周;之后,在每1000 g土内,分别添加生物炭0、5、10、20 g,均匀混合后,室温培养50 d;在培养1、4、7、14、21、35、49 d时分别取样,测定土壤pH和有机碳含量,利用Tessier分级法测定土壤Cd形态。【结果】红壤pH随生物炭施用量的增加显著升高,培养14天后,生物炭施加量为2%时,土壤由酸性变为弱碱性,生物炭对褐土pH的提高作用不显著。红壤和褐土有机碳含量均随生物炭施用量的增加而升高。培养49天后,红壤可交换态Cd含量的降幅较大,降幅为0.31～0.82 mg/kg,且处理2%的可交换态Cd含量最低,为1.24 mg/kg,生物炭施用量2%的红壤碳酸盐结合态Cd含量最高,为1.06 mg/kg,施用生物炭的红壤碳酸盐结合态Cd和Fe、Mn氧化物结合态Cd所占比例增加了3.14%～14.21%、8.20%～23.96%,施用生物炭的褐土碳酸盐结合态Cd和Fe、Mn氧化物结合态Cd升高了0.94%～2.61%、0.80%～7.90%。褐土的土壤有机碳含量和生物炭施用量与土壤可交换态Cd呈极显著负相关关系,与土壤碳酸盐结合态Cd,土壤Fe、Mn氧化物结合态Cd和土壤有机结合态Cd呈极显著正相关关系;红壤pH、有机碳含量和生物炭施用量均与土壤可交换态Cd呈极显著负相关关系,与土壤其他四种形态Cd呈极显著正相关关系。但在红壤中土壤有机碳和生物炭施用量与各形态Cd的相关系数均大于在褐土中的相关系数。【结论】综合分析两种类型土壤中Cd形态的变化,发现生物炭对红壤的修复效果优于对褐土的修复效果,因此生物炭可以作为Cd污染的酸性土壤的一种修复改良材料。     

EFFECT OF BORON-DOPED GOETHITE ON SOIL ACIDITY,DIFFERENT FORMS OF MANGANESE IN RED SOIL AND THE GROWTH OF RAPE (BRASSICA NAPUS L.) SEEDLINGS

Rape (Brassica napus L.) seedling pot experiments were performed with a red soil treated with goethite which had boron (B) either adsorbed (ad-B-goethite) or occluded (oc-B-goethite). Soil acidity, different forms of manganese in the soils and different elements content of the rape seedlings were determined. It was found that the addition of boron-containing goethite to the soils resulted in increased rape growth, elevated soil pH and decreased exchangeable acidity. Compared with the control, boron-containing goethite elevated the content of exchangeable manganese (Mn) (EXC-Mn), organic matter bound Mn (OM-Mn), reducible oxide Mn (RO-Mn) and residual Mn (RES-Mn) which were difficult to use for plant. Low labile organic matter was significantly correlated with easily reducible oxide Mn (ERO-Mn) (P < 0.01) and RO-Mn (P < 0.05). Middle organic matter and soil pH was significantly (P < 0.05) correlated with RES-Mn. Stepwise regression was used to select the combination of variables that best estimates shoot and root dry weight of rape seedling. Among them, soil pH, EXC-Mn, OM-Mn, RO-Mn and RES-Mn significantly influenced the dry weight of rape seedlings. The addition of boron-containing goethite improved the uptake of iron (Fe), calcium (Ca), magnesium (Mg), and copper (Cu) element and decreased the uptake of Mn and zinc (Zn) element in rape seedling. The results suggested that boron-containing goethite could provide a better soil acidity environment for plant growth; it was also an important agent increasing a part of manganese difficult to use for plant and reducing the activity of soil manganese, which was beneficial to altering rape seedling growth.     

Influence of pH on the redox chemistry of metal (hydr)oxides and organic matter in paddy soils

Purpose

The primary purpose of this study was to determine how flooding and draining cycles affect the redox chemistry of metal (hydr)oxides and organic matter in paddy soils and how the pH influences these processes. Our secondary purpose was to determine to what extent a geochemical thermodynamic equilibrium model can be used to predict the solubility of Mn and Fe during flooding and draining cycles in paddy soils.

Material and methods

We performed a carefully designed column experiment with two paddy soils with similar soil properties but contrasting pH. We monitored the redox potential (Eh) continuously and took soil solution samples regularly at four depths along the soil profile during two successive flooding and drainage cycles. To determine dominant mineral phases of Mn and Fe under equilibrium conditions, stability diagrams of Mn and Fe were constructed as a function of Eh and pH. Geochemical equilibrium model calculations were performed to identify Mn and Fe solubility-controlling minerals and to compare predicted total dissolved concentrations with their measured values.

Results and discussion

Flooding led to strong Eh gradients in the columns of both soils. In the acidic soil, pH increased with decreasing Eh and vice versa, whereas pH in the alkaline soil was buffered by CaCO₃. In the acidic soil, Mn and Fe solubility increased during flooding due to reductive dissolution of their (hydr)oxides and decreased during drainage because of re-oxidation. In the alkaline soil, Mn and Fe solubility did not increase during flooding due to Mn(II) and Fe(II) precipitation as MnCO₃, FeCO₃, and FeS. The predicted levels of soluble Mn and Fe in the acidic soil were much higher than their measured values, but predictions and measurements were rather similar in the alkaline soil. This difference is likely due to kinetically limited reductive dissolution of Mn and Fe (hydr)oxides in the acidic soil. During flooding, the solubility of dissolved organic matter increased in both soils, probably because of reductive dissolution of Fe (hydr)oxides and the observed increase in pH.

Conclusions

Under alternating flooding and draining conditions, the pH greatly affected Mn and Fe solubility via influencing either reductive dissolution or carbonate formation. Comparison between measurements and geochemical equilibrium model predictions revealed that reductive dissolution of Mn and Fe (hydr)oxides was kinetically limited in the acidic soil. Therefore, when applying such models to systems with changing redox conditions, such rate-limiting reactions should be parameterized and implemented to enable more accurate predictions of Mn and Fe solubility.     

钙盐诱导下土壤锰和铁的释放及其对胡椒的生物有效性

Releases of manganese and iron ions from an albic soil (Albic-Udic Luvisol), a yellow-red soil (Hap-Udic Ferrisol) and a yellow-brown soil (Arp-Udic Luvisol) induced by calcium salt addition and their bioavailability to pepper (Capsicum frutescens L.) were studied in a pot experiment. Addition of Ca(NO₃)₂ decreased soil pH and increased both exchangeable and DTPA (diethylenetriamine pentaacetic acid)-extractable Mn and Fe in soils. Meanwhile, total Mn accumulation in the shoots of Capsicum frutescens L. on the salt-treated soils increased significantly (P< 0.01) compared with the control, suggesting that salt addition to soil induced Mn toxicity in Capsicum frutescens L. Although exchangeable and DTPA-extractable Fe increased also in the salt-treated soils, Fe uptake by the shoots of Capsicum frutescens L. decreased. The effect of added salts in soils on dry matter weight of pepper varied with the soil characteristics, showing different buffer capacities of the soils for salt toxicity in an order of yellow-brown soil > albic soil > yellow-red soil. Fe/Mn ratio in shoots of Capsicum frutescens L. decreased with increasing salt addition for all the soils, which was ascribed to the antagonistic effect of Mn on Fe accumulation. The ratio of Fe/Mn in the tissue was a better indicator of the appearance of Mn toxicity symptoms than Mn concentration alone.     

Effect of nutrients and liming on changes in pH,redox potential,and uptake of iron and manganese by wetland rice in iron-toxic soil

In a greenhouse experiment, the nutrients NPK, NPK + lime, K, and Mn were applied to an iron-toxic soil (Typic Haplastulf). Soil pH and dry matter production were increased and Eh and available Fe in the soil were decreased. Though liming the soil decreased available Fe and Mn and increased pH to the greatest extent, the highest dry matter production was obtained with NPK application. NPK + lime produced a smaller yield than NPK without lime. Though the application of K or Mn alone produced much less dry matter than NPK or NPK + lime, no symptoms of Fe toxicity were observed. We conclude that Fe toxicity can be reduced with a balanced use of fertilizers (NPK or NPK + lime) and its occurrence was mostly due to nutrient stress.     

不同土壤的还原状况对铁镉形态转化和水稻吸收的影响

采用土壤-蛭石联合培养,以填充蛭石的网袋模拟根际,置于红壤、水稻土、盐土中后淹水栽培水稻13 d.试验结果表明,水稻栽培期问,红壤、水稻土、盐土pH变化范围分别为6.05 ～6.78、6.47 ～7.33、6.42 ～7.44;有机质处理下,除红壤根际pH明显升高外,其余土壤根际和非根际pH均有所下降.各土壤对照根际Eh保持在233 ～ 385 mV;有机质处理使根际Eh下降,同时也导致除盐土外的非根际Eh上升.土壤还原溶解Fe与蛭石吸附Fe的90％以上均米自铁锰氧化物结合态铁(Oxide-Fe)组分,与溶液Eh、pe+ pH均有显著相关性,表明两表面同为Fe的氧化还原反应,但方向相反.水稻根表Fe膜的形成与根际氧化还原状况有关,在对照根际(高Eh)环境下,根表Fe含量随pH升高而降低,在有机质处理根际(低Eh)环境下则随pH升高而升高;在红壤中,根表Fe膜阻碍Fe的吸收,在水稻土和盐土中,根表Fe膜促进Fe吸收.根表Cd含量与根内Cd、地上部Cd有显著正相关;在红壤中,根表Fe膜阻碍了水稻Cd的吸附和吸收;水稻土和盐土中,根表Fe膜促进了水稻Cd的吸附和吸收.     

上海地区水稻土氮素矿化模拟

Three types of paddy soils, derived from granite, Quaternary red clay and basalt, respectively, were selected to study the effects of Fe and Mn in paddy soils on methane production and emission through pot and incubation experiments. The results indicated that the difference of Fe and Mn in paddy soils was one of the important factors causing obvious differences in methane emission from different soil types. Soil Fe and Mn affecting methane emission from the paddy soils was likely through affecting soil Eh and forming Fe and Mn plaques on rice roots. Different rates and valences of added Fe and Mn significantly affected methane production from paddy soils. Therefore, this study enhanced understanding of processes controlling methane emission from paddy soils and may help to improve modeling and estimating regional and global methane emission from paddy soils.     

Iron‐manganese interactions among clones of Nilegrass

Tetraploid clones of Nilegrass (Acroceras macrum, Stapf.) develop a chlorosis resembling iron (Fe) deficiency on acid (pH 5.0) soils in the Midlands of KwaZulu, Natal, South Africa. Hexaploid and pentaploid clones appear more resistant to the disorder. Iron deficiency would not be expected in such acid soils, but foliar sprays of Fe sulfate reduce the symptoms within 24 hours. Aluminum (Al) toxiciry has been ruled out as a cause of this chlorosis on the basis of soil tests. Manganese (Mn)‐induced Fe deficiency has been postulated. Six Nilegrass clones, differing in ploidy levels, were grown under low Fe or high Mn levels in nutrient solutions, in Mn‐toxic soil, in calcareous soil and in a standard potting soil at pH 7.0. Differential chlorosis symptoms, similar to those observed in the field, were reproduced in plants grown in low Fe or high Mn solutions, in neutral potting soil and in calcareous soil at pH 7.8. Based on plant symptoms and dry weights, the tetraploids were generally more sensitive to these conditions than hexaploid or pentaploid clones. However, in Mn‐toxic soil, plants had leaf tip necrosis rather than the chlorosis typical of Fe deficiency. When grown in a standard potting soil at pH 7.0, plants showing chlorosis accumulated higher concentrations of phosphorus (P), Al, copper (Cu), Mn, Fe, and zinc (Zn) than non‐chlorotic plants. Differential susceptibility to chlorosis is apparently associated with interference of such elements in Fe metabolism, and not with differential Fe concentrations in plant shoots. Additional studies are needed to determine the chemical states of Fe and Mn in root zones and within plant shoots of these clones. Resolution of the differential chlorosis phenomenon would contribute to fundamental knowledge in mineral nutrition and could be helpful in tailoring plant genotypes to fit problem soils.     

Accumulation of atmospherically deposited metals in Wetland soils of Sudbury,Ontario

Concentrations of Cu, Ni, Fe, and Mg in soil/sediment material from 25 wetlands in the Sudbury, Ontario, region decline logarithmically with increasing distance from several ore smelters. Total Cu and Ni reach concentrations potentially toxic to plant life in soil/sediment material near the smelters. Despite random variation in soil/sediment pH and Eh, NH₄OAc extractable Cu, Ni and Fe, and DTPA extractable Cu Ni and Mg show the same pattern as total Cu, Ni, Fe, and Mg. The failure of DTPA extractable Fe to show the same pattern as total Fe may be due to the inadequacy of the DTPA soil test when testing Fe in acid soils. Soil/sediment organic C content increases with distance from the smelters, but is unrelated to pH or Eh.     

Methane emission and entrapment in flooded rice soils as affected by soil properties

Laboratory incubation experiments were conducted to study the effects of soil chemical and physical properties on CH₄ emission and entrapment in 16 selected soils with a pH range of 4.7–8.1, organic matter content of 0.72–2.38%, and soil texture from silt to clay. There was no significant correlation with CH₄ emission for most of the important soil properties, including soil aerobic pH (measured before anaerobic incubation), total Kjeldahl N, cation exchange capacity, especially soil organic matter, and soil water-soluble C, which were considered to be critical controlling factors of CH₄ emission. A lower CH₄ emission was observed in some soils with a higher organic matter content. Differences in soil Fe and Mn contents and their chemical forms contributed to the this observation. A significant correlation between the CH₄ emission and the soil organic C content was observed only after stratifying soils into subgroups according to the level of CH₄ emission in soils not amended with organic matter. The results also showed that the soil redox potential (Eh), anaerobic pH, anerobic pH, and biologically reducible Fe and Mn affected CH₄ emission significantly. Urea fertilization promoted CH₄ emission in some soils and inhibited it in others. This result appeared to be related to the original soil pH. CH₄ entrapment was positively correlated with soil clay content, indicating the importance of soil physical characteristics in reducing CH₄ emissions to the atmosphere.     

茶园—土壤系统铝和氟的生物地球化学循环及其对土壤酸化的影响

黄棕壤植茶以后,土壤pH下降,土壤酸度随植茶年限的增长而增大,且上层土壤pH的减幅大于下层土壤。茶园土壤的酸化是与茶树对铝和氟的生物积聚、土壤交换性铝与铝络合物的增加以及土壤盐基的淋溶有关。茶树落叶中铝和氟的含量分别高达5836—6136 ppm和469—520ppm;茶树透冠水和土壤渗漏液中均有相当多的Al和F,茶园土壤系统中铝和氟的循环,不仅导致土壤Al³⁺及F^-的增多,还使表土的有机络合态铝以及土壤交换性复合体和土壤溶液中的氟铝络合物积聚。因此,土壤中铝和氟的积累、转化及其生物地球化学循环是茶园土壤酸化的主要原因。