几种物质对水稻吸收镉的影响及机理

在添加Cd的红壤上,CaCO₃、Na₂SiO₃、有机物均不同程度地抑制了水稻植株对Cd的吸收,而磷酸盐和氯化物则促进了植株对Cd的吸收。CaCO₃和有机物促使土壤中交换态Cd向低有效性的络合态转化,磷酸盐和氯化物则抑制这种转化。     

黄棕壤添加重金属的毒性评价及其临界浓度确定

在连续盆栽水稻、小麦的过程中研究了加入黄棕壤的Cu、Cd、Pb的毒性(发光细菌法)。结果表明,当以水提取黄棕壤中三元素,浓度低,不显毒性,这与水提取红壤的结果相反;当以0.1mol L^-1HCI提取黄棕壤中三元素,则浓度明显提高而显示毒性。在相关显著水平P=0.001的基础上建立了土壤金属浓度与剩余发光度(毒性指标)优化拟合方程。规定含金属土壤的临界剩余发光度为90%(EC₁₀)。据此,估算出黄棕壤中Pb、Cu、Cd的临界浓度(μg/g土)分别为:488-587,17.8-25.3,2.11-2.12。     

徐淮地区石灰性土壤磷素固定的研究

用化学和物理化学的方法研究了纯CaCO₃固磷机制和特性.结果表明,随着起始磷浓度从低(0-10ppm P)到高(>10ppm P)变化,CaCO₃与磷先后发生吸附、沉淀反应,CaCO₃对磷具有很强的固定作用.徐淮地区石灰性土壤(黄潮土)固磷机制和特性的研究指出:起始磷浓度较低(0-200ppm P)时,以粘粒固定作用为主,CaCO₃的沉淀怍用不明显;起始磷浓度较高(>200ppm P)时,则粘粒与CaCO₃同时起作用,其中CaCO₃和磷之间的沉淀反应非常突出.石灰性土壤的固磷量和固磷强度均较高.     

用氯化铵提取法测定石灰性土壤中碳酸盐含量

测定石灰性土壤中的碳酸盐,通常采用气量法。但气量法测出的是CaCO₃及MgCO₃等碳酸盐的总和,称之为“CaCO₃相当物”,而不能分别检出CaCO₃和MgCO₃。     

影响土壤中铬迁移转化的几个因素

环境中的铬主要以三价和六价态存在,六价铬的毒性比三价铬大.天然水中的三价铬和六价铬可以相互转化,土壤中的铬通常以三价态的Cr⁺³阳离子及CrO^-₂的阴离子和六价态的Cr₂O₇^2-及Cr₂O₄^2-存在^[3].     

油蒿群落土壤碳酸钙和脱氢酶对土壤有机质的响应

Little attention has been paid to the role of soil organic matter (OM) in the formation of pedogenic carbonate in desert soils. The relationships among soil OM, soil dehydrogenase activity (DHA), and soil CaCO₃ in a plant community dominated by Artemisia ordosica, located on the eastern boundary of Tengger Desert in the Alxa League, Inner Mongolia, China, were studied to understand whether OM was directly involved in the formation of pedogenic carbonate. The results showed that DHA and CaCO₃ positively correlated with OM content, and DHA, OM, and CaCO₃ were correlated with each other in their spatial distribution, indicating that abundant OM content contributed to the formation of CaCO₃. Therefore, the formation of pedogenic CaCO₃ was a biotic process in the plant community dominated by A. ordosica.     

改良剂对镉污染酸性水稻土的修复效应与机理研究

为探明田间条件下施用石灰、钙镁磷肥、海泡石和腐殖酸等改良剂对Cd污染酸性水稻土的修复效应和作用机理, 通过在Cd污染区建立田间小区试验, 研究了改良剂单施和与石灰配施对Cd污染酸性水稻土中Cd作物有效性的影响。结果表明, 施用改良剂有效地改变了土壤中Cd的存在形态, 除腐殖酸外, 其他改良剂均使土壤酸提取态Cd不同程度地转化为可还原态Cd和残渣态Cd; 施用改良剂可使0.1 mol·L^-1 NaNO₃和 0.01 mol·L^-1CaCl₂提取态Cd 降低26%~97%, 降低效果为石灰+海泡石>海泡石>石灰+钙镁磷肥>钙镁磷肥>石灰>石灰+腐殖酸>腐殖酸; 改良剂使水稻地上部分的Cd吸收量降低6%~49%。试验结果还显示, 施用改良剂提高土壤pH是引起土壤中Cd作物有效性降低的主要原因之一。根据田间试验的结果, 海泡石可推荐作为Cd污染酸性水稻土的改良剂, 而腐殖酸则不宜使用。     

在DAP-CaCO3体系与DAP-石灰性土壤体系中NH3的挥发与磷的吸附之间的关系

本工作是研究在CaCO₃体系和石灰性土壤体系中NH₃的挥发与磷的吸附之间相互作用的化学变化,结果表明:在NH₄Cl—CaCO₃体系中,通气的pH值比不通气的低,但溶液中Ca²⁺浓度正好相反。在K₂HPO₄-CaCO₃体系中,在24小时内,通气与不通气的,CaCO₃吸附磷没有差异。在24小时反应期间,在DAP-CaCO₃体系中,因溶液pH值不断增高,NH₃的挥发对CaCO₃吸附磷的影响也就逐渐降低。在石灰性土壤体系中,施用尿素加过磷酸钙或单施尿素时,几乎没有发现NH₃的挥发,而施DAP时,在6天后,NH₃的挥发损失占加入的56%,且DAP处理的土壤,其水溶性磷未通气比通气的高。尿素加过磷酸钙处理的,其水溶性磷通气与未通气的没有差异。另外,尿素加过磷酸钙或过磷酸钙单独处理的土壤,水溶性磷含量均相同。所有这些均表明,在石灰质体系中,NH₃的挥发(如果发生的话)能够加强CaCO₃对磷的吸附,而磷的吸附又能加强NH₃的挥发,两者是相互影响和相互促进的过程。     

土壤中镉、砷、铅的微生物效应及其临界值

测试了盆栽(水稻)土壤添加Cd,As,Pb对土壤微生物的效应。确定了真菌、放线菌、细菌以及硝化细菌在供试浓度范围内呈现显著刺激效应或显著抑制效应的浓度范围。计算了各类菌的ED₃₀值,据此确定,三元素对菌的毒性大小顺序为:As>Cd>Pb。还测定了Cd,As,Pb对明亮发光杆菌T₃,变种的效应。在盆栽试验中,发光度与土壤添加金属浓度呈显著高度负相关。在大田调查中,发光度与土壤可提取性金属浓度呈显著高度(Cd)或中度(As,Pb)负相关。通过盆栽试验证明,T₃,发光度100%和80%可作为二个级别的临界发光度,从而估算出相应的添加金属临界浓度。若从T₃临界发光度100%预测污染土壤可提取性金属临界浓度与容量,可望得到满意的结果。     

纳米羟基磷灰石对重金属污染土壤Cu/Cd形态分布及土壤酶活性影响

通过室内培养实验,研究了纳米羟基磷灰石对重金属污染土壤Cu/Cd形态分布及土壤酶活性的影响。结果表明,施加纳米羟基磷灰石显著提高了土壤pH,其中3%和5%添加剂量处理60 d后使土壤pH分别提高了1.23个和1.35个单位;纳米羟基磷灰石显著减少了毒性较强的离子交换态Cu/Cd的含量,增加了毒性中等的碳酸盐结合态、铁锰氧化物结合态、有机结合态及毒性最低的残留态Cu/Cd含量,使Cu/Cd由植物可利用态向潜在可利用态转变;纳米羟基磷灰石不同程度地提高了土壤过氧化氢酶、脲酶和酸性磷酸酶活性。3种酶活性与Cu/Cd形态分布的相关性表明,过氧化氢酶和酸性磷酸酶对土壤重金属Cu/Cd活性变化比较敏感,可以作为重金属Cu/Cd污染土壤的评价指标。     

Toxicity of Cu and Cd in Soils and Detoxication by Additives

Results from laboratory experiments indicated that the concentrations and toxicities of both water-soluble and 0.1 M HCl-extractable Cu and Cd from soils were in the order of red soil> yellow brown earth> black earth. The toxicity of soil varied with the concentrations of metals. The form, concentration and toxicity of Cu and Cd in soils were determined by cation exchange capacity, content of organic matter and composition of clay minerals in the soil. Addition of CaCO3 could significantly decrease the concentration and toxicity of water-soluble and 0.1 M HCl-extractable Cu or Cd from the red soil, and could notably transform the Cu and Cd from the water-soluble or exchangeable form into the organic, free oxides-occluded or sulfic form.     

Effect of controlled-release urea on heavy metal mobility in a multimetal-contaminated soil

Controlled-release N fertilizers can affect the availability of heavy metals in the contaminated paddy soil.A soil incubation experiment was conducted to investigate the effects of prilled urea(PU),S-coated urea(SCU),and polymer-coated urea(PCU)on the solubility and availability of heavy metals Cd,Pb,Cu,and Zn in a multimetal-contaminated soil.The results showed that the application of different coated urea significantly affected the solubility and availability of heavy metals.At 5 d of incubation,the application of PU,SCU,and PCU had significantly decreased the concentrations of water-soluble and available Cd,Pb,Cu,and Zn,when compared with the control.At 60 d of incubation,the depletory effects of PU on water-soluble and available heavy metals had reduced,and the initial decrease in the concentrations of water-soluble Cd,Pb,Cu,and Zn caused by SCU had changed to an increase.The concentrations of water-soluble Pb,Cu,and Zn in the SCU-treated soil were higher than those in the control.Application with PCU led to a higher water-soluble Cu than that in the control,while the available Cd,Pb,and Zn were lower than those in the control.The effect of different coated urea was much stronger on the water solubility of the heavy metals than on their availability.The effects of controlled-release urea on the transformation of heavy metals resulted in changes in the concentrations of NH4^+,water-soluble SO4^2-,and soil p H.The results further suggested that PCU could be used in dry farming operations in multimetal-contaminated acid soils.     

不同磷水平对红壤溶液中锰、铝、镁和钙浓度变化以及小麦生长的影响

为了探明不同磷水平对红壤中土壤溶液主要金属离子变化的影响以及小麦对磷的响应,确定红壤中小麦适宜的施磷水平,采用原位提取土壤溶液和比较生物量的方法,监测了短期内红壤溶液中主要金属离子浓度变化及小麦生物量的变化。结果表明:碳酸钙的加入可以显著升高酸性红壤的p H,土壤溶液中铝、锰和镁浓度显著低于未加碳酸钙处理;800 mg/kg磷处理后铝、锰、镁和钙的浓度要比未加磷处理分别至少降低47%、44%、37%和33%。随着施磷量的增加,小麦在200 mg/kg磷处理时积累的生物量最大,随后磷增加,小麦生物量反而降低。而加碳酸钙处理小麦地下部生物量随着施磷量增加则降低。结果表明碳酸钙不仅可以有效升高土壤p H,降低土壤溶液铝浓度,还降低土壤溶液中锰的浓度。磷的加入同样可以降低锰和铝的浓度,缓解铝和锰毒害。红壤中生长小麦的适宜施磷量为200 mg/kg。     

三种有机肥水溶性分解产物对铜、镉吸附的影响

研究了稻草、紫云英和猪粪的水溶性分解产物对铜和镉的沉淀作用及其在红壤和潮土上的吸附影响。结果表明三种水溶性分解产物对铜镉的沉淀及吸附有双重效应：铬合效应和ｐＨ提高效应。在相同的ｐＨ值条件下,有机分解产物通过络合作用而不同程度地抑制了铜和镉的沉淀作用及其在两种土壤上的吸附。由于铜具有较强的形成络合物的能力,所以有机分解产物对铜的抑制效果对于镉的抑制效果。吸附等温线表明,在不调节ｐＨ时,三种有机分解产     

DISTRIBUTION AND SEQUENTIAL EXTRACTION OF SOME HEAVY METALS FROM SOILS IRRIGATED WITH WASTEWATER FROM MEXICO CITY

A sequential extraction procedure was used to fractionate Cu, Cd, Pb and Zn in 4 soil profiles into the designated forms of water soluble + exchangeable, organically bound, carbonate and Mn oxides bound. Soil profiles were obtained from the Rural Development District 063, State of Hidalgo, which have been irrigated with wastewater coming out of the basin of Mexico. The total heavy metal contents range as follows: Cu, 8.9 to 86.5 mg kg^-1 Cd, 0.86 to 5.07 mg kg^-1 Pb, 18.1 to 131.7 mg kg^-1 and Zn, 101 to 235.5 mg kg^-1. The highest concentrations of total heavy metals were found in the surface layers at all soil profiles. Sequential chemical fractionation indicated that the four metals were predominantly associated with the organic fraction at most soil samples. The contents in all fractions of the four metals showed a decrease with depth which has been explained by the variations in the organic matter and CaCO₃ contents in the different layers of soils. These soil properties were also the most important variables in the biological availability of the metals in these soils.     

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     

SOME PHYSICAL AND CHEMICAL PROPERTIES OF SOILS IN THE BEQA'A PLAIN, LEBANON

Physical and chemical properties of red soils, white rendzina, light chestnut, dark chestnut, grey, black, and recent alluvial soils as mapped by Geze (1956) were compared statistically. No statistically significant differences were found between surface soil (0–15 cm) and upper subsoil (15–30 cm) in any properties. Red soils were significantly lower than the others in total N, CEC, and CaCO₃ content. Recent alluvial soils were high in montmorillonite probably derived from the white rendzinas. The rendzinas were significantly higher in available P and CaCO₃ than any other soil. Black and grey soils, previously classified as one category, should be separated as they were significantly different in most properties.     

Zinc and copper in some soils of Egypt as related to other soil properties

Total Zn in alluvial and calcareous soils (average 138 and 70 ppm respectively) was significantly related to their contents of CaCO₃ (negatively), O.M. and clay (positively). Extracting Zn by Na₂EDTA gave the highest values for both soil types. Total Cu contents varied widely from 26 to 111 ppm in alluvial and from 15 to 30 ppm in calcareous soils. They were negatively correlated with the CaCO₃ contents. The pot experiments showed that EDTA(NH₄)₂CO₃, Na₂EDTA and DTPA are reasonable extractants for available Zn from both soil types. DTPA was efficient for all soils investigated, while Na₂ EDTA and EDTA-citrate were specific for extracting Cu from calcareous soils.     

Effect of Synergism and Antagonism between Metals on Toxicity in Soils

Synergism and antagonism of cadmium(Cd),copper (Cu) and selenium (Se) to biological toxicities in red soil,yellow brown soil and black soil were evaluated by MICROTOX method.The relation between forms of the tested metals in soil and the synergism or antagonism between them was also studied.Results showed that owing to the difference of soil chemical properties,toxicity of these metals in soils was different.In red soil with acid reaction and low in cation exchange capacity,antagonism occurred significantly between metals when they coexisted at high concentrations,while synergism occurred only under low concentrations.It is indicated that in red soil,toxicity of metals affected by synergism or antagonism depends on concentration of the metals present.For yellow brown soil and black soil with larger cation exchange capacity and lower exchangeable aluminium(Al),no toxicity of metals was observed even if metals were added to soil in high concentrations.Synergism and antagonism between Cd,Cu and Se were controlled by the forms of metals present.The amount of water-soluble metals was the most important factor in determining synergism and antagonism. In this paper,comparisons of synergism and antagkonism between metals in soils and in water solutions were made.There occurred the synergism of metal toxicity in water solutions when the concentration of coexisting metals was high.This is just opposite to the case in soils.     

Immobilization of trace metals by phosphates in contaminated soil near lead/zinc mine tailings evaluated by sequential extraction and TCLP

Purpose

The combined contamination of Pb, Zn, Cu, Cd, and As in the soils near lead/zinc mine waste posed a potential threat to the surrounding environment. Mitigation methods are needed to reduce the environmental risk. The aims of this paper were to evaluate the feasibility and efficiency of different forms of phosphates in remediating combined contamination caused by multi-metals and arsenic near the lead/zinc mining tailings.

Materials and methods

The tested soil was taken from a clayey illitic thermic typic epiaquepts soil (depth of 0–20 cm) near a lead and zinc mine tailing, located in Shaoxing, Zhejiang Province, China. Four pure chemical reagents, K₂HPO₄, Ca(H₂PO₄)₂.2H₂O, Ca₃(PO₄)₂, and Ca₅(PO₄)₃OH, were added to the soil in solution form as the trace metal stabilizing additives at a P application rate equivalent to 2,283 mg P/kg-soil and P/Pb molar ratio of 1. Shifts in trace metal speciation were determined using sequential extraction procedures and relative toxicities were evaluated using the standard EPA toxicity characteristic leaching procedure (TCLP).

Results and discussion

The addition of K₂HPO₄, Ca₃(PO₄)₂, Ca₅(PO₄)₃OH, and Ca(H₂PO₄)₂.2H₂O in the contaminated soil at the phosphorus application rate 2,283 mg P/kg-soil reduced Pb concentrations in TCLP extraction solution from 90.47 to 56.05, 83.80, 67.78, and 86.32 mg/kg (38.0, 7.36, 25.1, and 4.59% reduction), respectively. Sequential extraction analysis showed that phosphate treatments caused the transformation of easily available trace metal species to more stable forms. However, TCLP As in the soil increased from its initial value of 0.23 to 2.1, 0.70, 0.67, and 0.77 mg/kg, respectively, for the four treatments. The TCLP leachable As concentration of the K₂HPO₄-treated soil was about nine times of that from the untreated soil.

Conclusions

The addition of K₂HPO₄, Ca₃(PO₄)₂, Ca₅(PO₄)₃OH, and Ca(H₂PO₄)₂.2H₂O were effective in reducing water soluble and exchangeable Pb, Zn, Cu, and Cd, and minimizing TCLP-extractable Pb, Zn, and Cu. The sequential extraction test and the TCLP indicate that Ca₅(PO₄)₃OH treatment has a higher potential in immobilizing Pb, Zn, Cu, and Cd, though a slight enhancement of As mobility, comparing with other phosphate treatments.