The transfer of heavy metals to barley plants from soils amended with sewage sludge with different heavy metal burdens

Purpose

Our main aim objective was to evaluate the transfer of Cd, Cr, Cu, Ni, Pb and Zn to barley (Hordeum vulgare) grown in various soils previously amended with two sewage sludges containing different concentrations of heavy metals. This allowed us to examine the transfer of heavv metals to barley roots and shoots and the occurrence of restriction mechanisms as function of soil type and for different heavy metal concentration scenarios.

Material and methods

A greenhouse experiment was performed to evaluate the transfer of heavy metals to barley grown in 36 agricultural soils from different parts of Spain previously amended with a single dose (equivalent to 50 t dry weight ha^?1) of two sewage sludges with contrasting levels of heavy metals (common and spiked sludge: CS and SS).

Results and discussion

In soils amended with CS, heavy metals were transferred to roots in the order (mean values of the bio-concentration ratio in roots, BCF_Roots, in brackets): Cu (2.4)?~?Ni (2.3)?>?Cd (2.1)?>?Zn (1.8)?>?Cr (0.7)?~?Pb (0.6); similar values were found for the soils amended with SS. The mean values of the soil-to-shoot ratio were: Cd (0.44)?~?Zn (0.39)?~?Cu (0.39)?>?Cr (0.20)?>?Ni (0.09)?>?Pb (0.01) for CS-amended soils; Zn (0.24)?>?Cu (0.15)?~?Cd (0.14)?>?Ni (0.05)?~?Cr (0.03)?>?Pb (0.006) for SS-amended soils. Heavy metals were transferred from roots to shoots in the following order (mean values of the ratio concentration of heavy metals in shoots to roots in brackets): Cr (0.33)?>?Zn (0.24)?~?Cd (0.22)?>?Cu (0.19)?>?Ni (0.04)?>?Pb (0.02) for CS-amended soils; Zn (0.14)?>?Cd (0.09)?~?Cu (0.08)?>?Cr (0.05)?>?Ni (0.02)?~?Pb (0.010) for SS-amended soils.

Conclusions

Soils weakly restricted the mobility of heavy metals to roots, plant physiology restricted the transfer of heavy metals from roots to shoots, observing further restriction at high heavy metal loadings, and the transfer of Cd, Cu and Zn from soils to shoots was greater than for Cr, Ni and Pb. Stepwise multiple linear regressions revealed that soils with high sand content allowed greater soil-plant transfer of Cr, Cu, Pb and Zn. For Cd and Ni, soils with low pH and soil organic C, respectively, posed the highest risk.     

Effect of zeolite and phosphogypsum on yield,plant uptake,and content of strontium in soil

Abstract

Natural zeolite (clinoptilolite containing tuff) can be used as an adsorbent of strontium (Sr) from phosphogypsum when applied as a solonetzic soil amendment. This study investigated the influence of the zeolite on biological yield, content of water‐soluble Sr in soil, its availability, and plant uptake. A field experiment was conducted from 1993 to 1995 in the Volgogradskaya region of Russia. Two methods of phosphogypsum and zeolite application were used: “separate” and “as a mixture” (10 tons ha^‐1 of phosphogypsum and 0.5 ton ha^‐1 of zeolite in both cases). After the application of the amendments, barley (Hordeum vulgare) and grass sorghum (Sorghum sudanensis) were grown on the ameliorated sites in 1994 and 1995, respectively. Our results suggest that zeolite, being applied with phosphogypsum as a mixture, decreased by 15 to 75% the content of water‐soluble Sr in the soil, minimizing the risk of soil pollution. The uptake of Sr by plants depended on the biological character of the crop grown. Barley was found to be a “strong‐anticoncentrative” type of plant. However, grass sorghum was found to be more sensitive to the rise of Sr content in the soil. The highest biomass production of barley and grass sorghum was obtained with the application of zeolite and zeolite plus phosphogypsum. Plants grown on a single phosphogypsum‐treated sites had a declining tendency in biological yield. Our results suggest a positive influence of zeolite applied with phosphogypsum for the amelioration of solonetzic soils on the growth and uptake of Sr by plants.     

The role of oxidative stress in spring barley cross-adaptation to different heavy metals

The aim of this study is to investigate the possibilities and the mechanisms of spring barley (Hordeum vulgare L.) cross-adaptation to different heavy metals after hardening with ozone (O₃), drought and UV-B radiation. Dry shoot biomass, accumulation of superoxide (O₂˙^?) and malondialdehyde (MDA), and activities of enzymes superoxide dismutase (SOD), glutathione reductase (GR) and catalase (CAT) were measured after hardening and heavy metal treatments. Seedlings, exposed to ozone and drought prior to copper (Cu) treatment, showed significantly increased tolerance to this heavy metal. The most possible causes of cross-adaptation to this redox-active heavy metal, which triggered very strong oxidative stress in nonhardened barley seedlings, were increased CAT activity, mitigation of O₂˙^? accumulation and lipid peroxidation. Cross-adaptation to cadmium (Cd) was induced only by drought hardening. In this case, however, adaptation had lower effect on antioxidative enzymes, did not altered O₂˙^? accumulation and even slightly increased the intensity of lipid peroxidation. The study reveals that stimulation of CAT activity and mitigation of oxidative stress are the main reasons for plant adaptation to Cu; whereas cross-adaptation to Cd, heavy metal with much lower oxidative capacity, is determined by the mechanisms that are not related to oxidative stress directly.     

The uptake and distribution of heavy metals by spring wheat

Pot experiments were carried out with two soils from long-term field experiments to examine heavy metal distribution in spring wheat. The soils (Luvisol pH 6.5 and Cambisol pH 5.5) were manured with sewage sludge for 18 ys and now show heavy metal contamination. The Cd-, Zn-, Pb- and Cr-contents of the grain were appreciably lower than those of straw. Nickel and Cu levels in the grain, however, exceeded those of the straw. In the unpolluted control the grain was enriched in Zn. Grain with a Cd-content lower than the German guide value was produced only with Cd concentrations of the soil lower than 0.5 mg kg^–1 and a pH value greater than 5.7. Higher Ni and Pb contents were found in the chaff than in the straw. Roots were enriched in Cd, Zn, Ni and Cu, as compared with the soil. However, Pb and Cr were hardly taken up by the roots. Liming decreased the Cd-, Zn- and Ni-content in the plant. pH variation was found to have a negligible effect on the uptake of Cu, Pb and Cr.     

Comparison of methods for measuring heavy metals and total phosphorus in soils contaminated by different sources

The relationships between the concentrations of zinc (Zn), lead (Pb), copper (Cu), nickel (Ni) and chromium (Cr) as measured by X-ray fluorescence analysis (XRF), aqua regia, and HNO₃ pressure digestion were studied in soil samples covering a wide range of heavy metal concentrations. The soils were contaminated by sewage sludge, exhaust depositions, river sediments of mining residues, and dump material. The question was addressed whether the source of heavy metals or other soil properties affect the relationship between these three methods. The aqua regia-digestible fraction of the five heavy metals reached on average 64% of the XRF-detectable content. The pressure accelerated HNO₃-digestible fraction of the five heavy metals was on average 71% of the XRF-detectable content; the respective phosphorus (P) fraction reached a median of 75%. This suggests that HNO₃ pressure digestion can also be used for characterizing the total P content of soils. Aqua regia extraction and HNO₃ pressure digestion gave similar values for Zn, Pb, and Cu, which dominate the heavy metal load of most contamination sources. Significantly higher Cr values were obtained by HNO₃ pressure digestion than by aqua regia extraction. Additionally, the Cr contents were affected by the source, e.g. sewage sludge had relatively high contents of aqua regia and HNO₃ pressure extractable contents in comparison to the XRF values. The element-specific relationships between the three methods were all highly significant. However, the respective multiple linear regression models were in most cases affected by soil organic carbon (C), in some cases by clay or soil pH.     

超积累植物吸收重金属的生理及分子机制

超积累植物从根际吸收重金属 ,并将其转移和积累到地上部 ,这一过程包括跨根细胞质膜运输、从根表皮细胞向中柱的横向运输、从根系的中柱薄壁细胞装载到木质部导管、木质部长途运输、从木质部卸载到叶细胞 (跨叶细胞膜运输 )、跨叶细胞的液泡膜运输等主要环节和调控位点。本文就近十年来这方面的研究进展作一综述     

土壤添加不同颗粒组成沸石粉对玉米生长及养分吸收的影响

采用土柱试验,研究不同颗粒组成的沸石粉添加到0~20 cm砂壤土耕层对玉米生长、养分累积的影响,为改良沙地提供理论依据。本研究共设8个处理:CK0:不施肥+0 g沸石粉体(简称粉体);CK:施肥+0 g粉体;A:施肥+8 g粉体a;B:施肥+8 g粉体b;C:施肥+8 g粉体c;D:施肥+8 g粉体d;E:施肥+8 g粉体e;F:施肥+8 g粉体f。结果表明,处理A、B、C、D、E、F与CK之间的玉米株高均不存在差异;但其生物量均高于CK,粉体颗粒构成中0.002 mm的含量最高的两个处理E、F达显著水平,分别比CK高71.36%和63.69%。结果还表明,生物量与不同粉体颗粒5个粒级分布的百分比x1、x2、x3、x4、x5即0.05~0.25 mm、0.02~0.05 mm、0.01~0.02 mm、0.002~0.01 mm、0.002 mm百分率之间存在多元回归方程Y=3.69-0.050 6x1+0.082 5x2-0.093 4 x3-0.009 44 x4+0.064 86 x5,表明了玉米生长与颗粒组成之间的密切关系;方程系数表明生物量与细小颗粒含量呈极强的正相关,而与粗颗粒含量呈负相关。与CK处理相比,加粉体处理A、B、C、D、E、F均促进了氮和钾的吸收,但只有处理F对氮的吸收以及E和F处理对钾的吸收达显著水平。显著促进吸收的氮量达74.52%、钾量分别达63.39%和63.62%,而对磷没有显著促进作用。由此可以推论,在此土壤条件下,只有沸石粉体粘粒级颗粒含量高于39%时才显著促进玉米生长发育以及增加植株对氮、钾的吸收和利用。     

Content of some heavy metals in soil and corn grain

Abstract

In an attempt to find causes for lower than expected corn (Zea mays L.) production along the bottomlands of the Green and Pond Rivers in western Kentucky, corn fields were sampled for soil and corn grain to determine heavy metal content. Samples from sixteen carefully selected fields were analyzed for Cd, Cr, Pb, and Ni content. Yield of corn was not related to either soil or grain content of these heavy metals. There was also no relationship between soil pH and heavy metal accumulation by grain or heavy metal accumulation by grain and soil content of heavy metals within the range of levels found. Soil contents of Cr, Pb, and Ni were within the range of values reported in the literature for uncontaminated soils. However, soil content of Cd was near or above the upper end of the ranges reported in the literature, even on control samples taken upstream from sites of potential heavy metal pollution. Karnak soils (fine, montmorillonitic, nonacid, mesic Vertic Haplaquepts), which are high in montmorillonitic clay content and have high cation exchange capacities, had higher Cd content than the other soils sampled. Except for two sites, grain Cd content was similar to values reported in the literature. Corn yields were found to be generally lower on Karnak soils than on other soils, raising the possibility that observed lower than expected yields are related to the poor physical characteristics of these soils rather than heavy metal pollutants in floodwaters.     

Evaluation of yield and some physiological changes in corn and sorghum under irrigation regimes and application of barley residue,zeolite and superabsorbent polymer

In order to investigate the changes in chlorophyll fluorescence, chlorophyll, relative water content (RWC) and forage yield of corn and sorghum under various irrigation regimes and combination treatments of barley residue, zeolite and superabsorbent polymer, an experiment was conducted over 2 years in Kerman, Iran. A randomized complete block design arranged in a factorial split was used with three replications. Two irrigation regimes of normal and drought stress based on 70 and 140 mm cumulative pan evaporation, respectively, and two plant species (corn and sorghum) as factorial combinations were compared in the main plots. Five treatments, (1) 10 t ha^?1 zeolite + 4.5 t ha^?1 residue, (2) 60 kg ha^?1 superabsorbent + 4.5 t ha^?1 residue, (3) 5 t ha^?1 zeolite + 30 kg ha^?1 superabsorbent + 4.5 t ha^?1 residue, (4) 4.5 t ha^?1 residue and (5) – control, were compared in subplots. In both plants, forage yield, potential quantum yield (Fv/Fm), chlorophyll a, total chlorophyll and carotenoid contents decreased significantly under drought stress. Chlorophyll a content, SPAD index and Fv/Fm were higher in corn than in sorghum, but RWC was higher in sorghum. Corn produced higher forage yield (62.8 t ha^?1) than sorghum (49.3 t ha^?1). The application of 10 t ha^?1 zeolite with 4.5 t ha^?1 residue increased most traits more than any of the other treatments, but the superabsorbent had no significant effect on the studied traits.     

Mobility of heavy metals in pine forest soils as influenced by experimental acidification

The mobility of Pb, Zn, Cd and Cu was examined at two adjacent experimental plots at åmli, southern Norway, B-1 and B-2. Both experiments were established on the same glacifluvial deposits, with forest consisting of uniform stands of Pinus sylvestris L. The forest in B-1 was planted between 1968 and 1970, while B-2 consisted of naturally regenerated trees. The experiments included plots supplied with artificial rain of varying acidity over a period of seven and eight years for B-1 and B-2, respectively, in addition to control plots. In experiment B-1, experimental acidification was carried out both in unlimed plots and in plots applied with three different levels of lime. The two experiments showed distinct differences with respect to effects of the acidification on mobilization of heavy metals from the O horizon. In experiment B-1, the amount of Zn and Cd decreased with decreasing pH in artificial rain, while Pb and Cu were not appreciably affected. The reduction in Zn and Cd concentrations ceased after termination of the acidification experiment. Liming reduced the leachability of Zn, but still appreciable amounts of Zn were obviously leached from the O horizon during the experiment. In experiment B-2 a high retention even of Zn and Cd was observed in the O horizon, probably due to microbial uptake and accumulation.     

Effect of concentration on uptake of some trace metals by plants

Abstract

The uptake by plants of somes trace metals at different concentrations was related closely to the decay constant, I. This means that for a 10‐fold increase in applied concentration, the increase in uptake was close to 4. 93 (10^0.693 = 4. 93). With some trace metals the value of Y (10^Y = ratio of uptake for 10‐fold increase in metal concentration was around 1. For generalized conditions the value of Y in the expression, (/ = uptake ratio, for different concentrations and varied around I. Some values of Y for whole plants were Ni, 0.699 with C.V. (coefficient of variation) 12.2%, Cu, 0.468 with C.V. 12.1%, Zn, 0.606 with C V. 31.5%, and Cd, 0.903 with C.V. 10.9%. From soil the values for shoots for Co were 0.855 (C.V. = 14.8%) without EDTA (ethylenediamine tetraacetic acid) and 0. 941 (C. V. = 20. 8%) with EDTA; for Cu with EDTA it was 0. 562 (C. V. = 25.8%). with EDTA; for Cu with EDTA it was 0.562 (C.V. =25.8%).     

Growth,photosynthesis and protein content in cucumber plants as affected by supplied nitrogen form

Cucumber plants were grown hydroponically in three different nutrient solutions to determine the effect of NO₃ ^‐/NH₄ ⁺ ratio on several parameters. Top and root growth, CO₂ fixation, and ion content (K⁺, Ca⁺², NO₃ ^‐) were always lower when urea and ammonium nitrate were the major N source as compared with a Hoagland solution in which nitrate was the major N source. No significant differences were found in total N and protein content among the three nutrient solution treatments.     

Nitrogen mineralization and nitrogen uptake by maize as influenced by light and heavy organic matter fractions

On a sandy tropical soil, organic materials (prunings of Leucaena leucocephala, Senna siamea and maize stover) with contrasting C/N ratio (13, 18 and 56, respectively) were applied at the rate of 15 t ha^?1a^?1 in order to increase the amount of soil organic matter. Two light fractions (LF1 = LF > 2 mm and LF2 = 0.25 mm < LF < 2 mm) and the heavy fraction (HF) of the soil organic matter pool were determined by means of a combined density/particle size fractionation procedure and data obtained were related to soil nitrogen mineralization under controlled conditions and to nitrogen uptake by maize under field conditions. Under controlled conditions and when the LF1 fraction was excluded, nitrogen mineralization was found not to be correlated to total organic carbon content in the soil (R²=0.02). The R²-value of the linear regression increased considerably, when amount and C/N ratio of the LF2 fraction was taken into account in the regression analysis (R² = 0.88). Under field conditions, a multiple linear regression with amount and C/N ratio of HF, LF1 and LF2 better explained variation in crop nitrogen content and nitrogen uptake of maize (R² = 0.78 and 0.94) than a simple linear regression with total organic carbon (R² = 0.48 and 0.76). The results illustrate the importance of the two light and heavy organic matter fractions for estimating soil nitrogen mineralization. Determination of light and heavy soil organic matter fractions by density/particle size fractionation seems to be a promising tool to characterize functional pools of soil organic matter.     

The uptake of phosphate by barley plants from soil under aseptic and non-sterile conditions

The uptake of phosphorus by barley plants growing in soil has been compared in the presence and absence of microorganisms. The soil chosen for study was basaltic loam which earlier investigations had shown required the addition of supplementary phosphate to obtain successful growth of plants.Despite a rapid turnover of the phosphorus in microorganisms as a result of death and lysis, less was absorbed by plants grown under non-sterile conditions causing a considerable reduction in the yield of dry matter. These microbial effects were obviated by the addition of a small quantity of KH₂PO₄ (0.15 m-equiv/500 g soil). In this soil therefore, competition appears to exist between microorganisms and plants similar to that demonstrated previously in water culture.     

水稻籽实对不同形态重金属的累积差异及其影响因素分析

在分析成都平原核心区土壤重金属（Cd、Cr、Pb、Cu、Zn）全量、各形态含量及相应点位种植的水稻籽实重金属含量的基础上，通过统计分析、空间插值及线性回归方程的模拟，研究了土壤Cd、Cr、Pb、Cu、Zn全量的空间分布状况、各形态重金属含量统计特征，以及水稻籽实对重金属各形态的累积差异及其影响因素。结果表明，成都平原水稻土重金属污染较轻，除Cd外，均低于国家土壤环境质量二级标准。土壤中重金属的可交换态含量均较低，Cd主要以铁锰氧化态存在，Cr、Cu、Zn、Pb主要以残渣态存在。水稻籽实对5种重金属的累积效应顺序为：Cd＞Zn＞Cu＞Pb＞Cr。与水稻重金属累积关系密切的重金属活性形态（可交换态、碳酸盐结合态、铁锰氧化物结合态和有机物结合态）主要有：Cd的碳酸盐结合态、Cr的可交换态、Pb的有机物结合态和Cu的碳酸盐结合态含量；Zn各活性形态对水稻籽实含量的影响不明显。土壤理化性质对不同活性形态重金属元素的影响效应各不相同。活性态Cd主要受有机质、pH和容重的影响；活性态Cr与pH、有机质、CEC和容重密切相关；活性态Pb与有机质、容重、中细粉粒、砂粒等均有密切的关系；Cu的活性主要受粘粒、有机质含量的影响；Zn的有效性主要受pH、有机质、砂粒、容重的影响。总的看来，对土壤Cd、Cr、Pb、Cu、Zn各活性形态含量影响效应较强的是有机质、pH、容重，而与土壤吸附性能密切相关的颗粒组成、CEC的影响不甚明显。     

水稻子实对不同形态重金属的累积差异及其影响因素分析

在分析成都平原核心区土壤重金属(Cd、Cr、Pb、Cu、Zn)全量、各形态含量及相应点位种植的水稻子实重金属含量的基础上,通过统计分析、空间插值及线性回归方程的模拟,研究了土壤Cd、Cr、Pb、Cu、Zn全量的空间分布状况、各形态重金属含量统计特征,以及水稻子实对重金属各形态的累积差异及其影响因素。结果表明,成都平原水稻土重金属污染较轻,除Cd外,均低于国家土壤环境质量二级标准。土壤中重金属的可交换态含量均较低,Cd主要以铁锰氧化态存在,Cr、Cu、Zn、Pb主要以残渣态存在。水稻子实对5种重金属的累积效应顺序为:Cd>Zn>Cu>Pb>Cr。与水稻重金属累积关系密切的重金属活性形态(可交换态、碳酸盐结合态、铁锰氧化物结合态和有机物结合态)主要有:Cd的碳酸盐结合态、Cr的可交换态、Pb的有机物结合态和Cu的碳酸盐结合态含量;Zn各活性形态对水稻子实含量的影响不明显。土壤理化性质对不同活性形态重金属元素的影响效应各不相同。活性态Cd主要受有机质、pH和容重的影响;活性态Cr与pH、有机质、CEC和容重密切相关;活性态Pb与有机质、容重、中细粉粒、砂粒等均有密切的关系;Cu的活性主要受粘粒、有机质含量的影响;Zn的有效性主要受pH、有机质、砂粒、容重的影响。总的看来,对土壤Cd、Cr、Pb、Cu、Zn各活性形态含量影响效应较强的是有机质、pH、容重,而与土壤吸附性能密切相关的颗粒组成、CEC的影响不甚明显。     

Solubility and uptake of heavy metals from a Swedish soil

Samples of the surface layer (Ap) and of grass, collected from: (1) grass ley fertilized in the normal way; (2) permanent pasture fertilized in the normal way; and (3) permanent pasture treated with large amounts of sewage sludge five years earlier, were analysed for Mn, Zn, Cu, Cr, Co, Ni, Pb, and Cd.The soil samples were extracted with: (1) distilled water saturated with CO₂; (2) 1 M neutral ammonium acetate; (3) ammonium acetate + acetic acid, pH 4.75; and (4) 2 M nitric acid on a waterbath. The efficiency of these extractants differed greatly and, in relative values, was: 1 for H₂O + CO₂, 3.4 for NH₄OAc, 20.7 for NH₄OAc + HOAc, and 343 for 2 M HNO_3- The dissolving effects of the extractants differed markedly with the kind of element.Grass from the field treated with sewage sludge showed much higher contents of Mn and Zn and somewhat higher contents of Cu and Pb than grass from the untreated field. The levels of Cr, Co, Ni, and Cd were practically uninfluenced by the treatment. Grass from a field close to a highway accumulated large amounts of air-borne Pb and Cd during the summer.It is concluded that the total contents of heavy metals in soils have only limited importance for the uptake by plants. Weak extractants therefore give better information about the plant-available amounts in soils.     

Growth,yield and silicon uptake of rice (Oryza sativa) as influenced by dose and timing of silicon application under water-deficit stress

Two experiments were conducted to evaluate the effects of dose and timing of silicon (Si) application on rice under limited water supply. The treatments for the first study included five Si doses (0, 75, 150, 300 and 600 kg Si ha^–1) under three soil moisture conditions (100%, 75% and 50% field capacity). For the second study, the treatments were four Si application timings [100% basal, 50% basal + 50% panicle initiation (PI), 25% basal + 75% PI and 25% basal + 50% PI + 25% heading] at the dose of 300 kg ha^–1 under the same moisture conditions. The highest number of panicle plant^–1 (14.6) and grain yield (13.6 g plant^–1) were obtained with the dose of 300 kg Si ha^–1. Similarly, an increase of 34–45% in grain yield was observed for different Si application timings compared with the control. Shoot dry matter and grain yield had positive linear relationship with shoot Si content. Grain yield and number of spikelet panicle^–1 were higher at the 300 kg Si ha^–1 dose applied as 100% basal, and hence could be a feasible option for RD57 Thai rice variety under water-deficit conditions.     

农作物叶片对大气沉降重金属的吸收转运和积累机制

近年来,农产品的重金属超标问题已经引起了公众的广泛关注,也是国内外学者研究的热点.要实现农产品重金属污染的有效防控,首先需要解决的就是重金属来源问题.目前已有的研究大多集中在根系对土壤中重金属的吸收机制研究,且已基本探明作物根系对重金属的吸收转运机制,包括根际离子的活化,根细胞的吸附和扩散、跨膜运输,根皮层细胞的横向运...