High rates of domestic sewage sludge on a calcareous soil and their effect on wheat growth using a pot experiment

A pot experiment was carried out to explore the use of high loading rates of domestic sewage sludge from Jeresh (Jordan) on a calcareous soil. Sludge was mixed with soil in volume ratios of 1:8, 1:6, 1:4, 1:2, 1:1, 2:1, and 4:1 with the unamended soil as a control. Wheat (Triticum durum L.) was grown in the pots for 60 days. The addition of sludge at a ratio of 1:8 increased wheat growth significantly; 1:6 ratio resulted in better growth than the control, although the increase was not significant at the 5% probability level. Other ratios suppressed wheat growth. The analysis of sludge-soil mixtures indicated that the addition of sludge increased the extractable P, K, Fe, Zn, Mn, and Cu in the mixtures. The addition of sludge to soil increased N and P in wheat tissue to optimum levels, but decreased K content. Iron and Zinc increased in wheat tissue due to the addition of sludge to soil, however Mn and Cu were not much affected.     

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.     

Temporal variation of total and DTPA-extractable heavy metal contents as influenced by sewage sludge and perlite in a calcareous soil

Continuous application of sewage sludge (SS) as a source of organic matter, may increase available heavy metals (HMs) up to their critical levels. As a consequence their uptake by plants, risks of accumulation in food chain and groundwater pollution increases. To evaluate the effects of perlite and SS on total content and available fraction of iron (Fe), manganese (Mn), lead (Pb), copper (Cu), nickel (Ni), cadmium (Cd) and zinc (Zn) over 45 and 90 days a completely randomized pot experiment was conducted. Treatments consisted of SS (0, 2 and 4%) and combined SS and perlite levels (1:1, 1.5:0.5 and 0.5:1.5% SS:perlite). Mean available Fe, Ni, Cd, Mn and Zn fractions decreased over time by 7–27%, whereas, total contents did not change. Available HMs in SS-treated soils increased by 0.5–25%; whereas, only total Zn, Cu and Pb concentrations increased with SS application (although concentrations fall in the range of critical levels). The lowest (1.6 fold) and highest (22.1 fold) increases obtained for available Cu and Zn, respectively. Perlite could mitigate the adverse effect of high rate application of SS on amplification of HMs extractability. Therefore, their concomitant applications can be suggested considering the perlite durability and its positive effects on soil physical properties.     

污泥农用对土壤和作物重金属累积及作物产量的影响

以3 a定位试验为基础,比较3种不同处理的污泥肥料（消化污泥、污泥堆肥及污泥复混肥）农田施用下土壤养分、土壤和作物籽粒中Mn、Cu、Zn、Pb、Cd 5种重金属的积累以及作物产量的变化情况,以阐明污泥农用对土壤及作物的影响。研究表明,3种污泥肥料提高了土壤中氮素和有机质的含量;与空白和普通化肥处理相比,3种污泥肥料增加了土壤中Mn和Cu的含量,而对土壤交换态重金属含量没有显著影响;3种污泥处理均增加了小麦籽粒中Zn的含量;相对普通化肥处理,3种污泥肥料处理对小麦和玉米产量均无显著影响。合理施用污泥肥料可以有效地提高作物产量;污泥肥料施用对土壤重金属有一定累积效应,但短期施用对土壤比较安全。     

The soil solution in a soil treated with digested sewage sludge

Toxic trace metals may percolate to the ground water from sewage sludge disposed onto land. Analyses are presented of the soil solution from a slightly acid loamy soil treated 7 years earlier with single applications of digested sewage sludge in amounts equivalent to 0, 150 & 330 t dry matter ha⁻¹
These very heavy dressings correspond to 2 & 4.5 times the recommended 30–year limit. Samples of soil and soil solution from four depths to 80 cm were analysed for Al, B, Ba, Ca, Cl, Cu, Fe, K, Li, Mg, Mn, Na, Ni, P, S, Sr, V, Zn, together with the OM of the soil, and the pH, alkalinity, dissolved organic carbon, and absorbance at 350 nm of the solutions.
These very heavy sludge applications were apparently still releasing substantial quantities of NO₃, and some SO₄ even after 7 years. Nitrate, SO₄, Mg, Ca, Sr, B, and possibly Ba are still moving through the profile, possibly to the ground water. Solution concentrations of Cu and Zn are considerably higher at all depths than those in the untreated plot, but they fall off sharply with depth. It is unlikely that any Cu or Zn is now reaching the ground water.
The paper also presents a set of published solution analyses for soils, sludge–treated soils and digested sludge, as a basis for further studies.     

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.     

污灌区土壤重金属累积影响因素研究

本文研究了大气沉降、化学肥料施用、污水灌溉3个外源因素对污灌区土壤中重金属Hg、Cd、Pb累积的影响,结果表明:污灌区大气干湿沉降和施肥输入土壤中3种重金属元素的数量顺序为Pb>Cd>Hg。污灌水中重金属Hg、Cd、Pb含量的高低与相对应的灌区土壤中重金属的累积量的多少基本一致,对土壤Cd累积影响最大的是污水灌溉,对土壤Hg累积影响最大的是大气沉降,污灌与大气沉降对土壤Pb累积影响作用相近,施肥对3种重金属元素累积影响最小。     

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.     

Influence of sewage sludge and heavy metals on nematodes in an arable soil

Summary The abundance of nematodes was investigated in agricultural plots treated in three different ways, the first with no treatment, the second with 300 m³ ha^-1 a^-1 raw sewage sludge and the third with 300 m³ ha^-1 a^-1 sewage sludge with the addition of heavy metals. The nematodes were determined down to the genus and were assigned to five feeding groups. Total nematode numbers were highest in the site treated with sewage sludge and heavy metals. The smallest total numbers were found in the control site. The plant-feeding nematode genera showed different patterns of abundance depending on the sludge treatment and heavy metal content. For the mycophagic and bacteriophagic nematodes, numbers increased with the amount of sludge, especially in the sites with a higher heavy metal content. The family Rhabditidae was the most numerous group in the sludge plus heavy metals treatment. In contrast to these findings, the omnivorous nematodes were very rare in the sludgetreated plots and were completely absent in plots treated with sludge plus heavy metals, whereas predatory nematodes were numerous only after the application of sludge alone.     

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.     

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。     

用固定剂减少污泥中重金属污染土壤的研究

该研究将加有重金属固定剂的污泥装入废弃塑料容器制成施肥器,利用人工淋水或自然降水,使污泥中的养分从施肥器中流入土壤,而重金属被固定在污泥中,减少重金属土壤污染,再收集处理残渣,防止二次污染。通过淋滤试验和种植油麦菜、蕹菜的盆栽试验得出以下结论：硫酸钾作为固定剂和污泥混合,不仅肥效好,作物产量高,而且污泥重金属被水淋出量少,植物体内重金属的含量低。该文为污泥合理农用提供了新方法,同时充分利用了废弃塑料容器等废弃物,成本低而收效显著。     

Inorganic nitrogen in a tropical soil with frequent amendments of sewage sludge

Accurate prediction of plant-available N release from sewage sludge is necessary to optimize crop yields and minimize NO₃^– leaching to groundwater. We conducted a 1.5-year study with three maize crops to determine N mineralization from an urban sewage sludge from Barueri, State of São Paulo, Brazil, and its potential to contaminate groundwater with NO₃^–. The soil at the experimental site was a loamy/clayey-textured Dark Red Dystroferric Oxisol. The treatments consisted of: plots without chemical fertilization or sludge, plots with complete chemical fertilization, and plots receiving four different doses of sewage sludge. Dose 1 was calculated at the agronomic N rate, while doses 2, 3 and 4 were, respectively, two, four, and eight times dose 1. The inorganic N addition increased with the rate of biosolid application. The high NO₃^– concentrations in relation to NH₄⁺ were associated with intense soil nitrification. High N losses occurred for the first 27 days after soil sludge incorporation, even at the lowest dose, suggesting that land application of sewage sludge based on the N requirement of the crop may be overestimating the amount of sewage sludge to be applied.     

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.     

Protozoan bioassays of soil amended with sewage sludge and heavy metals,using the common soil ciliate Colpoda steinii

The common soil protozoan Colpoda steinii was used to study the toxicity of sulphate solutions of Ni, Cd, Cu, and Zn. The growth of C. steinii was reduced by 50% in the presence of 0.10, 0.22, 0.25, and 0.85 mg litre^-1 of Ni, Cd, Cu and Zn, respectively, during 24 h of incubation at 25°C, as calculated from a regression analysis of probit-transformed data. The same growth assay was used to assess the toxicity of soil solution extracted by centrifugation from soil samples of field plots of a grass/clover ley on a sandy loam treated with sewage sludge spiked with additional Cd, Cu, Cr, Ni, Pb, or Zn at concentrations either equivalent to or twice the limits for heavy metals recommended in recent EC guidelines (Commission of European Communities directive 86/278/EEC). The toxicity of these soil solutions varied with the season of the year. None of the soil solutions extracted in winter (February 1991) inhibited the growth of C. steinii. In summer (July 1991), the growth was reduced in solutions extracted from plots that were amended with sludge plus additional Zn or Ni at twice the maxima recommended by the EC. The changes in toxicity to C. steinii of the soil solutions between February and July were positively correlated with increases in heavy metal concentrations of Zn and Ni between winter and summer. These preliminary results suggest that regular protozoan bioassays may be used to monitor the biological availability of heavy metals in soils, especially when combined with other microbial assays and with chemical analyses of soil solutions.     

Carbon sequestration in a limestone quarry mine soil amended with sewage sludge

To reclaim a limestone quarry, 200 and 400 Mg/ha of municipal sewage sludge were mixed with an infertile calcareous substrate and spread as mine soil in 1992. Soil samples were taken 1 week later and again after 17 yr of mine soil rehabilitation so as to assess changes in the amount and persistence of soil organic carbon (SOC). Sludge application increased SOC as a function of the sludge rate at both sampling times. Seventeen years after the sludge amendments, the nonhydrolysable carbon was increased in the 400 Mg/ha of sludge treatment. The recalcitrance of SOC was less in sludge‐amended soils than in the control treatment at the initial sampling, but 17 yr later this trend had reversed, showing qualitative changes in soil organic carbon. The CO₂‐C production had not differed between treatments, yet the percentage of mineralized SOC was less in the high sludge dose. When the size of active (C_active) and slow (C_slow) potentially mineralizable C pools was calculated by curve fitting of a double‐exponential equation, the proportion of C_active was observed to be smaller in the 400 Mg/ha sludge treatment. Soil aggregate stability, represented by the mean weight diameter of water‐stable soil aggregates, was significantly greater in mine soil treated with the high dose of sludge (18.5%) and SOC tended to be concentrated in macro‐aggregates (5–2 mm). Results suggest that SOC content in sludge‐amended plots was preserved due by (i) replacement of the labile organic carbon of sludge by more stable compounds and (ii) protection of SOC in aggregates.     

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     

Effect of wetting conditions on the fractional composition of heavy metal compounds in agrosoddy-podzolic soils contaminated with sewage sludge

Excessive wetting significantly affects the physicochemical, chemical, and biological properties of soils and changes the valence of Fe and Mn and the fractional composition of their compounds, as well as the compounds of the microelements and heavy metals bound to them. It was found that the metals are subdivided into three groups with respect to the soil wetting conditions: (1) the iron-group metals, the state of which is determined by the soil wetting conditions, the development of the reduction processes, and the status of the Fe and Mn compounds as the main sorption complexes closely bound to Co and Ni; (2) the Cu and Pb compounds, the status of which depends on the soil wetting and redox conditions and which are closely bound to organic matter and Fe and Mn compounds; and (3) the Zn and Cd compounds, the status of which little depends on the soil wetting and redox conditions and which are characterized by a low affinity for Fe, Mn, and organic compounds.     

Chemical extractability of heavy metals during and after long-term applications of sewage sludge to soil

Sequential extractions were used on soils from a long-term experiment treated with either metal-contaminated sewage sludge or inorganic fertilizers between 1942 and 1961. The four extracts employed were CaCl₂, NaOH, EDTA and aqua regia. These showed that large increases in the proportions of Pb, Cu, Zn, Ni and Cd in at least one of the first three fractions occurred during the first 10 years of sewage sludge additions. Cr always remained predominantly in the aqua regia-soluble fraction. For 30 years after this, including a period of more than 20 years after application of sludges to the field had ceased, there was very little change in the percentage of each metal extracted by each reagent. Although the ‘residual’ (aqua regia-soluble) and EDTA fractions usually contained the largest amounts of metals in either sludge- or fertilizer-treated soils, there were clear differences between the metals: Pb represented the largest fraction of any metal extracted by EDTA, Cu of any metal extracted by NaOH and Cd of any metal extracted by CaCl₂. The same extractions were made of the sewage sludges that were applied to the field, and the distributions of the metals differed from those found in the treated soils. It was particularly apparent that more Pb and Cu was present as the ‘residual’ (aqua regia) fraction in sludges than in the soils.