Plant availability of heavy metals in a soil amended with a high dose of sewage sludge under drought conditions

The objective of this research was to study the effect of water deficit on soil heavy metal availability and metal uptake by ryegrass (Lolium multiflorum Lam.) plants grown in a soil amended with a high dose of rural sewage sludge. Three fertility treatments were applied: sewage sludge (SS), mineral fertilizer (M), and control (C); unamended). The levels of irrigation were: well-watered (W) and water deficit (D). Microbial respiration decreased the total organic C (TOC) in sludge-treated soils, but this did not enhance soil DTPA-extractable heavy metal concentrations. Indeed, Zn, Cu, Mn and Ni availability decreased during the experiment. C- and M-treated soils showed either no changes or increases of some trace element concentrations during the incubation. In the plant experiment, ryegrass dry matter (DM) yield, relative water content (RWC) and leaf water potential (_w) decreased in drought conditions. Sludge addition increased metal concentrations in plants. However, in some instances, SS-treated plants showed either similar or lower transfer coefficient (Tc) values than did plants in the C and M treatments. Water deficit decreased the concentration and the Tc of some metals in roots of M and SS plants. Results indicate that sludge-borne heavy metals were maintained in chemical forms of low availability. The lower metal uptake by SS and M plants under dry conditions cannot be attributed to a lower availability of these elements in soil.     

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.     

The change of heavy metals fractions during hydrochar decomposition in soils amended with different municipal sewage sludge hydrochars

Purpose

This study was to investigate the changes of heavy metals in the soils amended with different municipal sewage sludge hydrochars.

Materials and methods

Sewage sludge hydrochars prepared at either 190 or 260 °C, for 1, 6, 12, 18, or 24 h, respectively, were added to soil samples and then incubated for 60 days. Water-extractable organic carbon (WEOC) and CO₂ evolution were determined during the incubation. The total quantities of heavy metals and their different fractions were analyzed by inductively coupled plasma spectrometry (ICP).

Results and discussion

Hydrochar-amended soils had much higher water-extractable carbon and more CO₂ evolution than control soil, indicating that the added hydrochars contained a significant amount of WEOC and could be decomposed during the incubation. Hydrochar addition immediately and significantly increased the total heavy metals of the soil. Moreover, both oxidizable and residual fractions of all heavy metals were significantly higher in all the hydrochar-added soils than those in control soil. Both oxidable and residual fractions of heavy metals decreased in the hydrochar-amended soils during 60-day incubation. In contrary, both acid soluble and reducible fractions of heavy metals increased in the hydrochar-amended soils during incubation. It is thus obvious that the heavy metals in both oxidable and residual fractions may be released during hydrochar decomposition and then be adsorbed by soil matrix such as carbonates, iron oxides, and clays.

Conclusions

Municipal sewage sludge can be readily carbonized into hydrochar. However, it is watchful of applying the hydrochar into soil since hydrochar addition increases in both total and bioavailable heavy metals in soil. More work is particularly required to investigate the long-term impacts on soil and environment.

     

The quantitative changes of nutrients in two contrasting soils amended with sewage sludge compost evaluated by various statistical tools

Introduction: The application of organic fertilisers to replenish soil organic matter and improve soil fertility and productivity has become common agricultural practice.

Aim of the study: This research deals with the effects of soil amendment with sewage sludge compost (SSC) on organic carbon, nitrogen total, nitrogen mineral and available P, K, S and Mg mineralisation in two contrasting soils. The various statistical tools used in this study have allowed us to present another conceptualisation of nutrient increments or losses as an effect of SSC applied. In order to distinguish groups of nutrients which are similar, a cluster analysis was used. A two-way analysis of variance was applied to compare the increments of the content of nutrients in the soils.

Material and Methods: A 3-year pot experiment was conducted, employing a randomised, factorial design with two soils (light and medium) and one amendment treatment as a compost at a rate equivalent to 6 Mg ha^?1. The following parameters of chemical soil properties were determined: contents of organic carbon (Corg), total nitrogen (Ntot), amounts of available P, K, Mg, S and mineral nitrogen (Nmin).

Results: The SSC showed a similar influence on the fertility of both soils. It was affirmed that application of SSC results in a statistically significant increase in the contents of soil organic carbon. The amounts of total and mineral N, as well as available P and S were subjected to different patterns of quantity changes expressed by both increase and loss. Moreover, a statistically significant loss of available K amounts was observed in both soils.

Conclusions: The findings of the study indicated that mature SSC becomes a long lasting fertiliser, slowly subjected to decomposition processes. Therefore, it may influence small increases in nutrient amounts in soils, in relation to the contents obtained for the control soil.     

污泥及其复合肥对蔬菜产量及重金属积累的影响

通过盆栽和小区试验初步探讨了污泥复合肥对蔬菜的增产效应及其对蔬菜吸收累积重金属的影响。结果表明 ,污泥复合肥可显著提高蔬菜产量 ,蔬菜可食部分中的Cu、Zn、Cd含量均在国家食品卫生标准范围内 ,但Pb的含量超出了国家食品卫生标准     

黄粉虫幼虫对城市污泥重金属的积累作用

室内采用正交试验设计进行4 因素多水平试验, 研究了温度、城市污泥和麦麸配比、饲养密度、幼虫体重对黄粉虫幼虫生长速度、死亡率以及幼虫重金属含量变化的影响, 探讨黄粉虫幼虫在城市污泥中的生长状况和对城市污泥重金属的积累作用。结果表明: 随着温度的升高, 幼虫生长率和死亡率都呈上升趋势, 饲养密度、污泥和麦麸配比对黄粉虫幼虫生长率、死亡率无显著影响; 15 ℃、密度为0.2 g·cm^-2、污泥/麸皮为1∶2、幼虫体重为85.4±5.9 mg 时, 幼虫对Cu、Se、Hg 的积累作用较显著; 15 ℃、密度为0.4 g·cm^-2、污泥/麸皮为1∶0、幼虫体重为85.4±5.9 mg 时, 黄粉虫幼虫对Cd 的积累能力显著; 20 ℃、密度为0.4 g·cm^-2、污泥/麸皮为1∶0、幼虫体重为34.9±4.9 mg 时, Zn 的积累系数较大; 黄粉虫幼虫对Cu、Cd、Se、Hg 和Zn 等重金属元素有很强的积累作用。     

Wheat grown on volcanic ash with slow releasing nitrogen fertilizer and amended with sewage sludge compost

Abstract

The volcanic ash of the Mount Pinatubo in Philippines is used in this study. The major drawbacks of this volcanic ash for growing agricultural crops are nitrogen (N) and iron (Fe) deficiencies with low organic matter contents. The objective of this study is to investigate the effect of sewage sludge compost on wheat through shoot and root development as well as dry matter production by pot culture. Either oxamide or polyolefinresin‐coated urea (PORCU) along with potash and phosphate fertilizers is applied to each pot containing volcanic ash. Application of sewage sludge compost in oxamide treatment yield a better plant height with an extended root length and high dry matter production compared to PORCU. However, statistical analysis of the data on plant height shows significant level (p<0.001, n=36), while those on root growth and dry matter production show no significant difference (p<0.335 and 0.564, n=36). Thus it is concluded that the coupling effect of oxamide and sewage sludge compost has a greater impact on plants, while growing on this ash.     

Biological and physical resilience of soil amended with heavy metal-contaminated sewage sludge

Stability and resilience of a variety of soil properties and processes are emerging as key components of soil quality. We applied recently developed measures of biological and physical resilience to soils from an experimental site treated with metal‐contaminated sewage sludge. Soils treated with cadmium‐, copper‐ or zinc‐contaminated, digested or undigested sewage sludge were studied. Biological stability and resilience indices were: (i) the time‐dependent effects of either a transient stress (heating to 40°C for 18 hours) or a persistent stress (amendment with CuSO₄) on decomposition, and (ii) the mineralization of dissolved organic carbon (DOC) released by drying–rewetting cycles. Physical stability and resilience measures were: (i) compression and expansion indices of the soils, and (ii) resistance to prolonged wetting and structural regeneration through drying–rewetting cycles. Soil total carbon and DOC levels were greater in the sludge‐amended soils, but there were no differential effects due to metal contamination of the sewage sludge. Effects of metals on physical resilience were greater than effects on soil C, there being marked reductions in the expansion indices with Cd‐ and Cu‐contaminated sludge, and pointed to changes in soil aggregation. The rate of mineralization of DOC released by drying and wetting was reduced by Zn contamination, while biological resilience was increased in the Zn‐contaminated soil and reduced by Cd contamination. We argue that physical and biological resilience are potentially coupled through the microbial community. This needs to be tested in a wider range of soils, but demonstrates the benefits from a combined approach to the biological and physical resilience of soils.     

Impact of heavy metal amended sewage sludge on forest soils as assessed by bacterial and fungal biosensors

Bacterial and fungal bioluminescence-based biosensors were used as indicators of potential heavy metal toxicity to microorganisms in the needle litter of a mature Pinus radiata forest under heavy metal contaminated sewage sludge. Sewage sludge was amended with increasing concentrations of Cu, Ni and Zn and applied to the surface of a mature P. radiata forest. The response of the bacterial and fungal biosensors to soluble Cu, Ni and Zn in needle litter extracts was investigated. The bioluminescence response of the bacterial biosensor Escherichia coli HB101 pUCD607 declined as water-soluble Zn concentrations increased. The effective concentrations that gave a 50% reduction in bioluminescence (EC₅₀ values) for water-soluble Zn and total litter Zn were 1.3 mg l⁻¹ and 3700 mg kg⁻¹, respectively. The bioluminescence response of the fungal biosensor Armillaria mellea declined as soluble Cu concentrations increased. The EC₅₀ values for water-soluble Cu and total litter Cu were 0.12 mg l⁻¹ and 540 mg kg⁻¹, respectively. No decline in bioluminescence was noted for either the bacterial or fungal biosensor on exposure to increasing concentrations of water-soluble Ni. The use of a combination of bacterial and fungal biosensors offers a rapid and sensitive tool for assessing toxicity of heavy metals to microorganisms and, thus, elucidating the environmental impact of contaminants in sewage sludge on litter dwelling microorganisms.     

Heavy metal uptake by blue grama growing in a degraded semiarid soil amended with sewage sludge

Sewage sludge application to semiarid grassland may represent a beneficial means of utilizing this waste product for restoration of degraded sites. Consequently, dried municipal sewage sludge was applied at three rates (22.5, 45, and 90 Mg ha^–1) to a degraded semiarid grassland soil in order to determine the effects of sludge amendments on forage productivity, soil heavy metal content, and metal uptake by blue grama (Bouteloua gracilis).Soil and plant properties in control and amended plots were measured after 1, 2, and 5 growing seasons.Soil nutrients increased linearly with increased sludge application in the first two growing seasons. Consequently, forage quality and total production of blue grama improved significantly over the unamended control as the tissue levels of N, P, K, and crude protein increased. Cadmium and Pb in the sludge-treated plots did not increase significantly over the control after 1 and 2 growing seasons. Levels of DTPA-extractable soil micronutrients (Cu, Fe, Mn, Zn) increased linearly with increased sludge application rate to soil concentrations recommended for adequate plant growth. Soil N, P, and K concentrations remained higher in the sludge-amended soils after 5 growing seasons, while Cu and Cd increased to slightly above desireable limits as the soil pH decreased to 7.4 and 7.0 in the 45 and 90 Mg ha^–1 treatments, respectively. However, with the exception of Mn which remained within desirable limits, metal concentrations (including Cu and Cd) in blue grama tissue were not significantly different from the control treatment after five growing seasons. Based on soil and plant tissue metal concentrations, it appears that sludge applied at rates between 22.5 and 45 Mg ha^–1 will maintain the most favorable nutrient levels coupled with significant improvements in forage production in this semiarid grassland environment.     

Assessment of chemical composition of plants cultivated on two different soils amended with sewage sludge compost using MANOVA

Abstract

Application of organic fertilizers may replenish soil organic matter, improve soil fertility and increase plant yield and its quality. This research deals with the effects of soil amendment with sewage sludge compost (SSC) on the chemical composition of plants (white mustard, triticale and white lupine) cultivated on two contrasting soils (light vs. medium). A 3-year pot experiment was conducted and SSC at the rate of 6?Mg ha^?1 was applied to the soils.The study clearly demonstrated that SSC as an organic fertilizer had a minor influence on the modification of the chemical composition of shoots and grain cultivated in crop rotation plants and it was more evident in medium soil. The statistically confirmed effect was mainfested in higher c ontents of N and P in grain of plants in the 2^nd and 3^rd year of the experiment.     

Residual metal reactivity of humic acids extracted,from soil amended with sewage sludge

Copper, Fe, and Mn were used as probes to investigate residual metal reactivity for humic acid (HA) samples extracted from a loam soil, either non-amended or amended with anaerobically digested sewage sludge for 4, 5, 6, or 7 yr at 90 t ha^?1. yr^?1. Irrespective of their origin, the HA complexes significant amounts of metal, in forms stable against intense water-leaching, in the order Fe > Cl > Mn. Sludge-amended soil HA adsorbed and retained Fe in amounts greater than HA extracted fron non-amended soil. Metal adsorption occurred mainly by cation-exchange replacement of metals previousl: bound to HA. Water-stable Fe³⁺-HA complexes prepared in the laboratory were partially stable agains H⁺ and metal ion exchange reactions, whereas Cu²⁺ and Mn²⁺ in laboratory-prepared, water-stabl HA complexes were desorbed almost completely by these two reactions. Electron spin resonance spectra indicated that the laboratory-prepared metal-HA complexes had a chemical composition and molecula structure similar to that of indigenous metal-HA complexes, which were stable against all leachin, and cation-exchange treatments. Although the HA samples showed a maximal metal binding (i.e. saturation) as metal loading of the sludge-amended soil increased, they still exhibited a high residua binding capacity for the three metals used as probes.     

Comparison of phosphorus availability with application of sewage sludge,sludge compost,and manure compost

Abstract

The objectives were to determine if phosphorus (P) from different organic wastes differs in availability to crops. Four materials: digested, dewatered sewage sludge (DSS); irradiated sewage sludge (DISS); irradiated and composted sewage sludge (DICSS); and composted livestock manure (CLM) were applied for two years at five rates (0, 10, 20, 30, 40 Mg#lbha^‐1#lbyr^‐1) with four replicates. Uptake of P was measured in lettuce [Lactuca saliva L. (cv. Grand Rapids)], bean [Phaseolus vulgaris L. (cv. Tender Green)], and petunia [Petunia hybrida Vilm. (cv. Superior Red)] in 1990, and in consecutively harvested two cuts of lettuce in 1991. Percentage of total P that was extractable by 0.5M sodium bicarbonate (NaHCO₃) in CLM (30–70%) was much higher than in DSS, DISS, and DICSS (0.8–5.6%). Phosphorus uptake by crops harvested in an early stage of growth, lettuce in 1990 and first cut lettuce in 1991, and the extractable soil P linearly increased with total P applied. The lack of response in P uptake with bean pod and petunia in 1990, and the second cut lettuce in 1991, was possibly due to their advanced stage of maturity. Much larger amounts of P were applied with DSS, DISS, and DICSS than with CLM, while P uptake and extractable soil P did not increase compared to that in the treatment that received no P. The low availability of P in sludge was likely caused by iron (Fe) and aluminum (Al) which precipitated P. Sludge irradiation and/or composting had no significant effect on P availability.     

Behaviour of cadmium and nickel in a soil amended with sewage sludge

Various urban and industrial sewage sludges were applied to a soil at two doses (50 and 100 t ha⁻¹ y⁻¹) during eight years in a field experiment. The soil was analysed at two depths (0–30 and 30–60 cm) for extractable cadmium and nickel. In general these trace metal increased with dosage. However, cadmium formed complexes with organic matter and nickel bound to iron and manganese oxides. Hence, the available fractions of these metals constituted a small proportion of the total content. The results obtained show a low risk of contamination due to the available fractions of these metals at sludges dosages of up to 100 t ha⁻¹. Copyright © 2001 John Wiley & Sons, Ltd.     

Renovation of a pear orchard site with sludge compost

Abstract

A lime‐stabilized sewage sludge compost was used as a surface amendment to improve the soil and nutritional status of a number of established pear cultivars grown on an acidic, low ferility soil site. Leaf Ca status was significantly increased while trace metals were not elevated and in most cases decreased by sludge compost over the course of the study. Soil chemical properties were modified in a manner similar to liming. Addition of sludge composts, particularly low metal containing materials, appears to represent an acceptable aid in renovating established pear orchards located on poor soil sites. Leaf, fruit flesh or peel Cd were not significantly effected by the compost addition. The compost added twice the recommended level of available N the first year and sub‐optimum N the following two years. Leaf N, although significantly increased in the composted versus non‐composted controls, was below sufficiency levels by the third year after addition. This indicates that compost cannot fully supply required N from a one time application even over the short term.     

Enzyme activity and microbial biomass in a field soil amended with municipal refuse

Summary Changes in enzyme activity levels, in biomass-C content, and in the rate of fluorescein diacetate hydrolysis were measured in a loamy soil to which solid municipal refuse had been applied as compost over a 3-year period at two different rates. Addition of the compost caused significant increases in the activity of all enzymes tested. The increases were much higher at 90 t ha^-1 year^-1 than at 30 t ha^-1 year^-1. Significant increases were also observed in the biomass-C content and in the rate of fluorescein diacetate hydrolysis. Significant correlations among changes in biomass-C content and the rate of fluorescein diacetate hydrolysis and the changes in all enzymes tested were found.Two activity indices were calculated; a biological index of fertility and an enzyme activity number. No correlations were found between the biological index of fertility and the changes in the various enzyme activities. However, significant correlations were found either between enzyme activity number and most of the changes in enzyme activity, or between the enzyme activity number index and the biomass-C content (r=0.850). The use of a new activity index, the hydrolysis coefficient, is proposed. This coefficient was significantly correlated with biomass-C content (r=0.925) and with the enzyme activity number index (r=0.780).     

Effects of municipal solid waste compost and sewage sludge on mineralization of soil organic matter

This work sets out to verify whether the application of municipal solid waste compost (MSWC) or treated urban sewage sludge (USS) organic amendments efficiently promote organic matter (OM) increases in a Haplic Podzol (PZha) and in a Calcic Vertisol (VRcc). For that purpose, carbon (C) mineralization and C kinetic parameters were studied, using a laboratory experimental incubation setup. The results showed that the addition of the amendments to the soils increased their mineralization capacities, and that the highest C mineralization rate was reached at the end of the first 2 d of incubation. The different characteristics of the soils seem to have influenced the C mineralization rates during the 28-d incubation. The USS induced higher C mineralization than the MSWC, and the PZha soil gave rise to higher C mineralization than VRcc. For all treatments, C mineralization adjusted well to an exponential plus linear kinetic model, suggesting that the organic C of the amendments was made up of two organic pools of differing degrees of stability. With the exception of the application of USS 60 t ha⁻¹, all the treatments increased the OM content on both soils, or at least the OM remained constant throughout the incubation.     

根际促生菌及其在污染土壤植物修复中的应用

植物对重金属吸收、转运和积累以及植物生物学特征使其成为修复重金属污染土壤的重要手段之一。然而,由于植物对重金属的耐受性有限而限制其广泛实际应用,因而探讨植物修复技术强化措施就显得尤为重要。随着自然资源的开发和技术的发展,微生物调控使植物修复技术变得更为可行和更有价值。回顾近年来新兴的微生物调控技术,植物根际促生菌资源因其对环境无污染,可利用自身的抗性系统减缓重金属对植物的毒性,促进植物的生长和影响重金属的迁移等优势,在修复过程中发挥着重要作用。目前,国内外就植物根际促生菌的筛选、鉴定和应用价值等方面已经做了大量的相关研究。本文综述了根际促生菌-植物相互作用的机制及其促进植物修复重金属污染土壤的作用原理。     

Plant growth and microbial activity in a tropical soil amended with faecal pellets from millipedes and woodlice

The effect of soil fauna-mediated leaf litter (faecal pellets) versus mechanically fragmented (finely ground) leaf litter on biomass production of rice (Oryza sativa, var. Primavera) was assessed in pot tests. Rice seedlings were either grown in soil samples amended with faecal pellets of diplopods and isopods fed on leaf litter of a legume cover crop (Pueraria phaseoloides (Roxb.) Benth) and a peach palm (Bactris gasipaes) or in soil amended with finely ground leaf litter. The addition of faecal pellets caused a significant and dose-related increase in plant biomass compared to pure soil. Ground leaf litter induced a significantly smaller positive effect on plant biomass development with Pueraria litter > Bactris litter > mixed primary forest litter. In contrast, soil microbial biomass development during the 4 weeks plant test was higher in the soil amended with ground litter as compared to soil amended with feacal pellets. The results show a clear positive effect of the soil fauna on soil fertility and indicate differences in the availability of nutrients from the organic substrates to higher plants and soil microorganisms.