Changes in organic matter and enzymatic activity of an agricultural soil amended with metal‐contaminated sewage sludge compost

Abstract

The effect of organic amendment with sewage sludge composts of varying heavy metal content on the organic matter content and enzymatic activity of an agricultural soil supporting barley (Hordeum vulgare L.) or lettuce (Lactuca sativa L.) crops was studied. The organic amendments did not improved lettuce growth, the contaminated composts having a negative effect on yield. However, all organic amendments improved barley straw yields although they did not affect grain yields. The addition of the organic materials increased the total carbohydrate content of the soil although this content decreased with cultivation. There was a clearly observed effect of crop type and the degree of heavy metal contamination of the amendment on the most labile carbon (C) fractions (water‐soluble C, carbohydrates, and polyphenolics). In general, soil enzymatic activities were stimulated by addition of sewage sludge compost with low heavy metal content. The compost containing high level of cadmium (Cd), copper (Cu), nickel (Ni), and zinc (Zn) inhibited protease‐BAA activity with respect to the other composts. After cultivation, urease activity increased in soil amended with the high dose of composts, regardless their degree of metallic contamination. Both crop type and metallic contamination contained in the organic materials added influenced phosphatase and ß‐glucosidase activity.     

Toxic effect of cadmium and nickel on soil enzymes and the influence of adding sewage sludge

Sewage sludge is increasingly used as an organic amendment to soil, especially to soil containing little organic matter. However, little is known about the utility of this organic amendment in the reclamation of soil polluted with heavy metals. We studied the effects of adding sewage sludge on enzymatic activities of a semi-arid soil contaminated with Cd or Ni in the laboratory. The activities of urease, phosphatase, β-glucosidase and protease-BAA were measured in soil containing concentrations of Cd or Ni in the range 0–8000 mg kg⁻¹ soil, and their inhibition was compared with those of the enzymatic activities in the same soil amended with sewage sludge and containing similar concentrations of the heavy metals. The inhibition was tested for three different incubation times to determine changes in the effect of the heavy metals on hydrolase activity with the time elapsed after contamination. Ecological dose (ED) values of Cd and Ni were calculated from three mathematical models which described the inhibition of the enzymatic activities with increasing concentrations of heavy metal in the soil. For urease and phosphatase activities, the ED values for Cd and Ni increased after application of sewage sludge to soil, indicating a decrease in Cd and Ni toxicity. The other two enzymes (β-glucosidase and protease-BAA) were less sensitive to Cd or Ni contamination, and it was more difficult to determine whether addition of sewage sludge had affected the inhibition of these enzymes by the heavy metals.     

土壤酶活性对土壤中土霉素的动态响应

采用室内培养试验研究了土霉素（OTC）对土壤过氧化氢酶、磷酸酶、脲酶、蔗糖酶和脱氢酶活性的影响。结果表明,在整个培养期间,土霉素对土壤过氧化氢酶和土壤磷酸酶活性具有明显的抑制作用;对土壤蔗糖酶和脱氢酶活性在培养前期具有轻微的抑制作用,但培养后期（培养第112 d）具有较强的抑制作用;而对土壤脲酶活性的影响则相反,在培养第1 d,OTC 100 mg/kg处理对脲酶具有显著的刺激作用,以后土霉素对脲酶活性影响不明显。土壤过氧化氢酶和磷酸酶对土霉素污染响应比土壤脲酶、蔗糖酶和脱氢酶更敏感,因而可以表征土壤受土霉素的污染程度。     

Effects of Sewage Sludge and Acacia dealbata Composts on Soil Biochemical and Chemical Properties

We studied the effects of different composts made of different mixtures of sewage sludge and Acacia plants on the soil biochemical and chemical properties. The proportions of mixed acacia plant and sewage sludge were: AL1/1 (50% acacia/50% sewage sludge), AL1/2 (33.3% acacia/66.6% sewage sludge), and AL1/3 (25% acacia/75% sewage sludge). Composts were added to the soil at a rate of 2%. Soil samples were collected during 150 days and analyzed for soil enzyme activities and chemical properties. An unamended soil was used as the control. Compared to the AL1/1 treatment, soil dehydrogenase, urease, phosphatase and β-glucosidase activities decreased respectively by 14.6%, 15.4%, 12.5%, and 19.3% for AL1/2 treatment and by 20.7%, 25.6%, 23.7%, and 28.4% for AL1/3 treatment. Soil water-soluble carbohydrates and polyphenols were the greatest in AL1/1. The lowest contents of heavy metals in the AL1/1 compost may be responsible for the increase of soil biochemical and chemical properties.     

Enzyme Activities in a Sandy Soil Amended with Sewage Sludge and Coal Fly Ash

Previous studies showed that coal fly ash could stabilize sewage sludge by reducing metal availability, but fly ash may cause an adverse effect on soil microbial activities. Therefore, an experiment was performed to evaluate the effects of amendment of soil with anaerobically digested dewatered sewage sludge, stabilised with alkaline coal fly ash, on soil enzyme activity and the implications for soil nutrient cycling. Sewage sludge was amended with 0, 5, 10, 35 and 50% w/w of fly ash, and then the ash-sludge mixtures were incubated with a sandy soil at 1:1 (v/v). Dehydrogenase activity decreased with an increase in fly ash amendment level and the time of incubation. Soil receiving 5% ash-sludge amendment had a higher dehydrogenase activity than other treatments. Soil receiving 10% ash-sludge mixture had the highest urease activity and in general, urease activity decreased with increasing incubation time. Phosphatase activity was the highest at 5% ash-sludge mixture amended soil and no general trend was observed with time. Water-soluble Zn, Mn and Cu contents were suppressed by the addition of fly ash. The present experiment indicated that addition of 10% ash-sludge mixture should have a positive benefit on the activity of soil microorganisms, N and P nutrient cycling, and reduce the availability of heavy metals.     

Amidase and urease activity in soil as affected by sludge,salinity and wetting and drying cycles

Three incubation experiments were carried out to assess the effect of different levels of sludge, salinity and of different wetting and drying cycles on amidase and urease activity in a calcareous silt loam soil. Both amidase and urease activities were largely increased with the increase in the amount of sludge applied. The addition of NH₄⁺ - N with sludge slightly reduced both activities. Addition of increasing amounts of a 1:1 NaCl: CaCl₂ salt mixture increasingly reduced the soil activities of amidase and urease. This effect was less severe in sludge amended soil. The data also showed that drying of either unamended or sludge amended soil cause a marked drop in amidase and urease activity. Rewetting increased both enzyme activities.     

铅对两个红壤中酶活性的影响

Enzyme activities have the potential to indicate biological functioning of soils. In this study, soil urease, dehydrogenase, acid phosphatase and invertase activities and fluorescein diacetate（FDA） hydrolysis were measured in two red soils spiked with Pb^2＋ ranging from 0 to 2 400 mg kg^-1 to relate the enzyme activity values to both plant growth and the levels of available and total Pb^2＋ concentrations in soils, and to examine the potential use of soil enzymes to assess the degrees of Pb contamination. Soil samples were taken for enzyme activities assaying during 3 month’s incubation and then after planting of celery（Apium graveolens L.） and Chinese cabbage（Brassica chinensis L.）. Enzyme activities in the red soil derived from arenaceous rock（RAR） were generally lower than those in the red soil developed on Quaternary red earths（REQ）. At high Pb^2＋ loadings, in both incubation and greenhouse studies, urease activity and FDA hydrolysis were significantly inhibited. But there were no significant relationships between soil dehydrogenase, acid phosphatase or invertase activity and soil Pb^2＋ loadings in both RAR and REQ soils. The growth of celery and Chinese cabbage increased soil urease activity and FDA hydrolysis, but had minimal effect on dehydrogenase and invertase activities. There were positive correlations between celery biomass and soil urease activity and FDA hydrolysis. These results demonstrate that urease activity and FDA hydrolysis are more sensitive to Pb^2＋ than acid phosphatase, dehydrogenase and invertase activities in the RAR and REQ soils.     

Effects of N-enriched sewage sludge on soil enzyme activities

Sewage sludge is increasingly used as an organic amendment to soil, especially to soil containing little organic matter. However, little is known about utility of this organic amendment with N-enriched or adjusted C:N ratios in soil. We studied the effects of adding of different doses (0, 100, 200 and 300 t ha⁻¹) and C:N ratios (3:1, 6:1 and 9:1) of sewage sludge on enzyme activities (β-glucosidase, alkaline phosphatase, arylsulphatase and urease) in a clay loam soil at 25 °C and 60% soil water holding capacity. Nitrogen was added in the form of (NH₄)₂ SO₄ solution to the sludge to reduce the C:N ratio from 9:1 to 6:1 and 3:1. The addition of different doses and C:N ratios of the sludge caused a rapid and significant in the enzymatic activities in soils, this increase was specially noticeable in soil treated with high doses of the sludge. In general, enzymatic activities in sludge-amended soils tended to decrease with the incubation time. All activities reached peak values at 30 days incubation and then gradually decreased up to 90 days of incubation. Sewage sludges also the increased available metal (Cu, Ni, Pb and Zn) contents in the soils. However, the presence of available soil metals due to the addition of the sludge at all doses and C:N ratios did negatively affect all enzymatic activities in the soils. This experiment indicated that all doses and C:N ratios of sewage sludge applied to soil would have harmful effects on enzymatic activity. Some heavy metals found in sewage sludge may negatively influence soil enzyme activities during the decomposition of the sludge.     

土壤锗污染对土壤酶活性的生态毒理效应

通过室内培养和盆栽试验,研究了土壤添加锗(Ge)对黄棕壤过氧化氢酶、脱氢酶、脲酶、碱性磷酸酶、转化酶的生态毒理效应。结果表明,在土壤Ge含量2~200 mg kg-1范围,土壤Ge对脱氢酶、碱性磷酸酶、转化酶活性抑制作用不明显。土壤Ge对土壤过氧化氢酶和脲酶活性有明显抑制作用,脲酶受Ge的抑制作用最强。土壤Ge含量与脲酶活性之间具有显著负相关,脲酶抑制率可作为Ge生态风险评价的一项生物指示物。     

Effect of Sewage Sludge and Rice Straw Compost on Yield,Micronutrient Availability and Soil Quality under Rice–Wheat System

ABSTRACT

There is a need to improve the way in which crop residues and industrial organic wastes are managed and also to study their potential use in agriculture for improving soil fertility and biological activity. This study evaluated the effects of integrated use of organic (sewage sludge (SS) and rice straw compost (RSC)) and inorganic fertilizers on crop yield, soil enzymes activity, macro- and micro-nutrients availability under rice–wheat cropping system after three consecutive years of cropping in a subtropical semi-arid area. Different combinations of inorganic nitrogen and two doses of organic sources (SS and RSC) were applied to the soil. The results revealed that substitution with 50% N through RSC significantly increased the yield and biochemical properties as compared to inorganic fertilizers (NPK) alone. Micronutrients availability was found increased in treatment having substitution of 50% N through SS @10 t ha^?1. All the enzymatic activities viz. dehydrogenase, fluorescein diacetate (FDA), phosphatase, phytase, and urease) were found to be maximum by substitution of 50% N through RSC. Also, a significant positive correlation was found between soil enzymes (dehydrogenase and FDA) and organic carbon as well as crop yield. Thus, the study demonstrated that substitution of 50% inorganic nitrogen through organic sources will be a better alternative for improving soil quality and productivity.     

污灌时间对土壤肥力及土壤酶活性的影响

通过时空互代、野外调查和采样分析的方法,研究了石家庄栾城县不同污水灌溉时间下（0~52 a）耕地土壤肥力及土壤酶活性特征。结果表明：与对照点相比,污水灌溉区土壤有机质、全氮、全磷含量,蔗糖酶、脲酶和磷酸酶活性均相对较高,而土壤阳离子交换量、过氧化氢酶和脱氢酶活性无明显的变化规律;污水灌溉区土壤全氮、蔗糖酶、磷酸酶与污灌时间之间表现出显著正相关性（P〈0.05）,其他指标与污灌时间之间均无显著相关性;土壤肥力（有机质和全氮）、重金属（总Cr和总Cd）与水解酶（脲酶和磷酸酶）之间表现出显著正相关性,交换态Cr与脱氢酶活性之间呈现出显著负相关性。上述特征反映了污水灌溉时间对土壤肥力及土壤酶活性具有复杂的影响效应,而这些效应是决定污水灌溉区土地生产力能否高产的重要因素。     

Short-term effects of sewage sludge application on phosphatase activities and available P fractions in Mediterranean soils

The aim of this study was to investigate factors regulating phosphatase activities in Mediterranean soils subjected to sewage sludge applications. Soils originating from calcareous and siliceous mineral parent materials were amended with aerobically digested sewage sludge, with or without physico-chemical treatment by ferric chloride. Sludge amendments, ranging from 6.2 to 10 g kg⁻¹ soil, were carried out in order to provide soil with a P total quantity equivalent to 0.5 g P₂O₅ per kg of soil. Bacterial density, phosphatase activities (i.e. acid and alkaline phosphomonoesterases and phosphodiesterases) and available P (i.e. P Olsen and P water) were measured after 25 and 87 days of incubation. Results showed significant effects of sewage sludge application and incubation period. Sewage sludge effect resulted in an increase in phosphatase activities, microbial density and available P. Incubation period increased available P while decreasing phosphatase activities. This study also revealed that the origin of sludge and its chemical characteristics may show different effects on certain variables such as phosphodiesterases or bacterial density, whereas mineral parent materials of soils did not show any significant effects.     

Microbiological Properties in Earthworm Cast and Surrounding Soil Amended with Various Organic Wastes

Abstract

Changes produced in the microbiological properties of earthworm Lumbricus terrestris casts and surrounding soil by the addition of various organic wastes such as wheat straw (WS), tea production waste (TEW), tobacco production waste (TOW), cow manure (CM), and hazelnut husk (HH) were evaluated in an incubation experiment. Twenty‐one days after organic waste treatment, analyses of microbial biomass (Cmic), basal soil respiration (BSR), metabolic quotient (qCO₂), and enzyme activities (dehydrogenase, catalase, β‐glucosidase, urease, alkaline phosphatase, and arylsulphatase) were carried out on collected cast and soil samples. Addition of organic wastes to the soil increased values of Cmic, BSR, and enzyme activities in soil and earthworm casts, indicating activation by microorganisms. Except for catalase activity, these values of microbiological parameters in casts were higher than in surrounding soil at all waste treatments and control. The addition of organic wastes caused a rapid and significant increase in organic carbon, total nitrogen, and microbiological properties in both soils; this increase was especially noticeable in soils treated with TEW.     

Urease activity in sewage sludge-amended soils

Three diverse field-moist soil samples were treated with five sewage sludges (applied at five loading rates) containing high concentrations of heavy metals. Urease activity was assayed after 0, 3, 7, 14 and 30 days of incubation. Results showed that when soils were treated with the sewage sludges, urease activity was often inhibited at the lower loading rates (2.2 and 8.9mg sludge g^?1 soil), but was enhanced substantially with the higher application rates (22.2, 44.4 and 100 mg sludge g^?1 soil). Inhibition of urease activity in the sewage sludge amended-soils ranged from 4 to 37% (Domino soil), 8–27% (Hesperia soil), and 3–49% (Ramona soil) at various times of incubation. Inhibition of the enzyme activity was attributed to the presence of heavy metals in the sludges. The increased activity of urease in the sludge-amended soils at the highest application rate (100 mg sludge g^?1 soil) ranged from 1.13 to 5.00-fold (Domino soil), 1.20–4.04-fold (Hesperia soil), and 1.13–5.40-fold (Ramona soil). Enhanced urease activity was believed to be due to the additional source of organic matter and nutrients supplied by the sludge which stimulated microbial activity and subsequent urease synthesis.     

城市生活污泥蚯蚓处理过程中相关酶活性的动态变化特征

利用大平2号蚯蚓处理城市生活污泥,分析了其对污泥磷酸酶、脲酶、蛋白酶、蔗糖酶活性的影响。结果表明,污泥经蚯蚓处理后,相关酶的活性发生了较大的变化,污泥酸性和碱性磷酸酶活性先升高而后下降,中性磷酸酶的活性则持续下降;污泥脲酶的活性先升高后下降;蛋白酶和蔗糖酶的活性则持续下降。总体来说,所研究的4种酶的活性随着时间延长有下降的趋势,其中污泥蛋白酶的活性下降最为显著,其他相对较小。污泥蚯蚓处理过程中有机质等的降低可能是酶活性下降的主要原因。     

Soil enzymatic response to addition of heavy metals with organic residues

Changes in organic C, available P, available heavy metal contents and enzymatic activities induced by addition of two heavy metal rich organic residues [a municipal solid waste compost (MWC) and a non-composted paper sludge (PS)] were determined in two different soils during a 280-day incubation experiment. The addition of the organic materials caused a rapid and significant increase in the organic C and enzymatic activities in both soils, this increase was specially noticeable in soils treated with MWC. In general, enzymatic activities in amended soils tended to decrease with the time. Organic materials also increased heavy metal contents in soil. However, the presence of available soil heavy metals due to the addition of the organic materials at doses of 50,000 kg ha^-1 did not negatively affect dehydrogenase, #-glucosidase or urease activities in the soils. There were significant and negative correlations between heavy metals and phosphatase activity in the soils at the beginning of the incubation. This negative correlation was probably due to the decrease in the enzyme activity in soils treated with PS in which high levels of available P were also found. It is difficult, therefore, to attribute an inhibition of the enzyme activity to the presence of these heavy metals because a high available P concentration in soils also depresses phosphatase activity.     

Stabilized municipal sewage sludge addition to improve properties of an acid mine soil for plant growth

Purpose

Degraded soils, such as those encountered in areas of mine activities, need to be ameliorated by liming to correct soil acidity and by addition of organic inputs to improve soil properties and fertility.

Materials and methods

Non-amended mine soil and soil amended with stabilized sewage sludge were incubated for 45 days. Soil physicochemical and biological indicators were periodically measured along incubation and other enzyme activities at the end of incubation. In improved soils, a study of plant development in 250-g pots was carried out with three vegetal species: tomato, rye grass and ahipa. Germination and mortality rates, biomass production and photosynthetic pigments were measured.

Results and discussion

Soil incubation with sewage sludge slightly increased soil pH and led to an enhancement of soil electrical conductivity, organic carbon and dehydrogenase activity, especially for the higher doses (5 and 10%). However soil respiration was more promoted with the 2% dose, pointing to a possible toxic effect of the sludge. At the end of incubation, physicochemical and biological properties were in general enhanced. Biomass production was improved in tomato and rye grass by sewage sludge addition (more at the 2% dose), whilst ahipa growth was not affected by sewage sludge treatments. Tomato mortality reached 73% with high sludge doses (10%).

Conclusions

According to this set of parameters, amendment with sewage sludge of a limed acid mine soil would be considered as a good strategy for soil amelioration in view of plant establishment and development.     

Effects of organic and mineral amendments on available P and phosphatase activities in a degraded Mediterranean soil under short-term incubation experiment

The aim of this study was to determine the effects of mineral and organic-P-fertilizers on soil P availability, bacteria densities and phosphatase activities, in a degraded Mediterranean soil characterized by low level in soil organic matter and nutrients. A typical degraded Mediterranean soil, originating from a siliceous mineral parent material, was amended with different organic or mineral P-sources: aerobically digested sewage sludge (SS), with or without physico-chemical treatment by ferric chloride; sewage sludge compost (SSC); Na or K mineral P-salts (Pi-salts). All the amendments were carried out in order to provide soil with a P total quantity equivalent to 0.5 g P₂O₅/kg of soil. Bacterial density, phosphatase activities (i.e. acid (APH) and alkaline (BPH) phosphomonoesterases and phosphodiesterases), BPH/APH ratio, and available P (P Olsen) were measured after 25 and 87 days of incubation. Results showed that all the P-sources used to fertilize soil during this study resulted in significant increase in P concentration. However, different responses in phosphatase activities and bacterial densities were obtained with regards to the amendment applied to soil. Indeed, it appeared clearly that sewage sludge (SS) considerably stimulated soil biological activity, and more especially the different kinds of phosphatases involved in P mineralization and P turn-over. On the contrary, sewage sludge compost (SSC) as well as P-salts amendments did not affected these parameters in most cases. Results showed also that the incubation time influenced almost all the biological and chemical parameters investigated during this study. As a consequence, P availability was considerably improved in the amended soils between the two sampling dates.     

Effects of a cadmium-contaminated sewage sludge compost on dynamics of organic matter and microbial activity in an arid soil

 An incubation experiment lasting 120 days was carried out to ascertain the effect on the soil microbial activity and organic matter mineralization of adding a sewage sludge compost contaminated with two different levels of Cd to an arid soil. Two composts, with a low (2 mg kg^–1) and high (815 mg kg^–1) Cd content, respectively, were used in this experiment. Both composts increased the total organic C, humic substance and water-soluble C contents, the beneficial effects still being noticeable after 120 days of incubation. The most labile C fraction (water-soluble C) was the most sensitive to the high Cd content. The high Cd concentration decreased soil microbial biomass C and stimulated the metabolic activity of the microbial biomass, the metabolic quotient (qCO₂) revealing itself to be a very sensitive index of the stress that the incorporation of a Cd-contaminated sewage sludge compost causes in a soil. The effect of Cd contamination on enzyme activities (urease, protease that hydrolyse N-α-benzoil-l-arginamide, phosphatase, and β-glucosidase) depended on the enzyme studied. Received: 10 September 1997     

Biogeochemical responses of soil ecosystems to raw coal pollution in Xuanhua,China

Purpose

China is the world’s largest coal producer and consumer. Despite extensive studies on coal-burning pollution, the effect of raw coal pollutants caused by transportation and turnover on soil along the road received little attention. The main purpose of the study was to clarify the biogeochemical response of soil ecosystems to raw coal pollution.

Materials and methods

The raw coal and unpolluted soil from the coal distribution area in Xuanhua, China were collected for the incubation experiments. Combined with the determination of soil physicochemical properties, including pH, electric conductivity, soluble ions, dissolved organic carbon, and available heavy metals, the biogeochemical responses of soil to raw coal pollution, such as soil enzyme activities (β-glucosidase, alkaline phosphatase, and Urease), microbial community composition, and soil respiration, were systematically studied. In addition, a q-PCR analysis of the urease was performed to clarify the inhibitory mechanism of urease by coal pollution. Furthermore, a simple field investigation was carried out to confirm the incubation results.

Results and discussion

Raw coal pollution not only changed the soil physicochemical properties but also made the available Zn, Ni, and Co accumulate significantly. A positive priming effect in soil with the low-dose raw coal addition was trigged, but soil respiration rate and soil enzyme activity, such as β-glucosidase and alkaline phosphatase, were inhibited to different degrees with the increased pollution. Urease activity also decreased under the higher coal contamination, which was due to inhibition of ureC gene expression. In addition to the slight soil acidification caused by coal pollution, microbial communities and diversity was also found to be affected. The relative abundances of the microorganisms related to urease, alkaline phosphatase, and β-glucosidase changed accordingly. The incubation results are in good agreement with the field survey results.

Conclusions

Low-dose raw coal pollution can trigger the soil positive priming effect. However, as the coal pollution increased, the β-glucosidase, alkaline phosphatase, and urease in the soil were inhibited to varying degrees. The compounding effects of soil acidification, increased electric conductivity, and the accumulation of available heavy metals such as Zn, Ni, and Co are the key causes for the biogeochemical response of soil to coal pollution.