Soil Catalase Activity Research Articles

Effects of Biochar on Soil Water-Soluble Sodium, Calcium, Magnesium and Soil Enzyme Activity of Peach Seedlings

The effects of biochar (rape straw, paddy straw, wheat straw and corn straw) on soil water-soluble sodium (Na), calcium (Ca), magnesium (Mn) and soil enzyme activity of peach seedlings was studied by pot experiment. The experimental result indicated that the effect of paddy straw biochar on soil water-soluble Na content was not significant compared with control, but caused a significant increase in the content of soil water-soluble Ca and Mn. Corn straw biochar significantly increased the content of soil water-soluble Na, and the content of soil water-soluble Ca and Mg were little different from that of control. The soil water-soluble Ca content under wheat straw biochar treatments was significant lower than that of other treatments. Soil enzyme activity is a comprehensive index of soil fertility, and all the biochar treatments led to a significant increase in soil urease activity, which significantly decreased the soil invertase and acid phosphatase activities, and the soil catalase activity between biochar treatments and control had no obviously difference. In conclusion, paddy straw biochar and corn straw biochar have a better effect on soil water-soluble mineral elements such as Ca and Mg, and biochar can promote or inhibit soil enzyme activity under planting peach seedlings.

ВЛИЯНИЕ ЗАГРЯЗНЕНИЯ СЕРЕБРОМ НА АКТИВНОСТЬ КАТАЛАЗЫ ЧЕРНОЗЕМОВ, БУРЫХ ЛЕСНЫХ ПОЧВ И СЕРОПЕСКОВ

Due to the widespread use of products based on silver nanoparticles, the risk of contamination of the soil cover and surface water increases, since an element in this form can leach out of the material. The amount of silver emissions into the environment is increasing every year. There is growing evidence of silver toxicity for living organisms of not only aquatic, but also terrestrial ecosystems. Silver, accumulating in soil in large quantities, like other heavy metals, can have a toxic effect on the physical, chemical and biological properties of the soil.High doses of the element can have a significant effect on the biological properties and ecological condition of soils. The study of enzyme activity can be used to identify major changes in the soil under the influence of silver. In this regard, it is relevant to study the effect of silver on catalase activity, since this enzyme is an indicator of the potential biological activity of the soil and reflects the intensity of mineralization processes in it. The aim of the work was to study the effect of silver pollution on the activity of soil catalase most characteristic of the southern regions of Russia. The object of the study identified soils characteristic of southern Russia: ordinary chernozems, seropesks and brown forest soils. For model studies, soil samples were taken from the upper arable layer (0‑10 cm), since silver accumulates in the surface soil layers. Silver pollution was modeled in a laboratory. Used silver nitrate at a concentration of 1 mg / kg, 10 mg / kg and 100 mg / kg, the experiment was 3 times biological repetition. The choice of biological indicators is due to the fact that oxidoreductases are most sensitive to chemical pollution among enzymes. This enzyme is an indicator of the biological activity of the soil and reflects the intensity of the mineralization processes in it. Laboratory and analytical studies were carried out using generally accepted methods in biology, soil science and ecology. Catalase activity was determined by the volumetric method according to A.Sh. Galstyan. As a result of the study of the effect of silver on three types of soils, the most characteristic of the southern regions of Russia, a decrease in catalase activity was noted. The degree of reduction of this indicator depended on the dose of the element introduced into the soil. The degree of resistance to silver contamination has the following sequence: common chernozem> sulfur sands ≥ brown forest soil. This is probably due to the light particle size distribution of sulfur sand and the acidic reaction of the environment of brown forest soils (pH = 5.8), as well as a low content of organic matter (1.8 % and 2.3 %, respectively), which contributes to high mobility, and therefore and high ecotoxicity of silver in these soils. A decrease in the activity of catalase of ordinary chernozem was observed for 90 days. At 1 UDC on the 30th and 90th day of the experiment, the same decrease in the studied parameter was observed. A similar pattern was observed at 10 UDC at the same experimental time. At 100 UDC (100 mg / kg) on the 90th day after contamination, a tendency toward restoration of catalase activity was observed, however, control values before silver contamination were not achieved. Chernozems have a high number of microorganisms and their high activity, and pollution tolerance mechanisms provide detoxification of soils from exposure to silver.

Biochar prepared from maize straw and molasses fermentation wastewater: application for soil improvement.

A novel method was applied to improve biochar properties and its soil application by introducing molasses fermentation wastewater into a maize straw pyrolysis process. In this study, maize straw biochar (MSB) was prepared from maize straw mixed with different amounts (1, 2 and 3 mL g−1 straw, v/w) of molasses fermentation wastewater which contained high organics and nitrogen contents. Characterization results indicated that the yield, carbon content, N/C, and cation exchange capacity (CEC) of MSB increased gradually with the increasing dosage of fermentation wastewater. In addition, the prepared MSB was added into sandy soil with four mixing proportions (1%, 3%, 5% and 10%, w/w) to investigate its effects on plant growth, soil properties and soil catalase activity (CAT) by pot experiments. The results indicated that MSB amendments increased soil pH, soil total organic carbon (TOC) and nutrients contents (TN, TP). It was suggested that 5% biochar proportion in soil derived from maize straw with 2 mL g−1 fermentation wastewater addition was more suitable for ryegrass growth, soil fertility and CAT activity improvement. This study provides a promising way to realize the resource utilization of fermentation wastewater and agricultural wastes at the same time.

Effect of green garlic/cucumber crop rotation for 3 years on the dynamics of soil properties and cucumber yield in Chinese anthrosol.

Long-term drastic anthropic inputs in conventional monoculture systems cause negative plant-soil feedback that will largely affect sustainable cucumber cultivation. The inclusion of multicropping in intensive cropping systems could reduce the detrimental effects of continuous cropping obstacles. The present study investigated the dynamics of soil microbial communities, soil enzyme activities and cucumber yield under plastic tunnel cultivation for three successive growing seasons (2013, 2014 and 2015). In the amended crop rotation system, soil pH decreased with increasing number of cropped garlic bulbs. The soil electrical conductivity significantly changed during the entire growth period and increased with increasing number of incorporated garlic bulbs. The level of soil organic matter content increased in the last year (2015). Soil catalase activity was generally induced by the treatments of 10, 15, 20 and 25 garlic bulbs, and soil invertase activity was also enhanced by all the treatments in the last year. Similarly, fungal species richness dramatically increased under these crop rotation systems. In this study, we found the highest cucumber yield under the cropping treatment of 20 garlic bulbs. The results indicate that the green garlic/cucumber cropping system is a sustainable and efficient cropping system for cucumber production and can improve the soil environment to a certain extent. © 2019 Society of Chemical Industry.

Responses of polyphenoloxidase and catalase activities of rhizosphere and bulk soils to warming during the growing season in an alpine scrub ecosystem.

To understand the effects of climate warming on rhizosphere ecological processes in the alpine scrub ecosystem, the responses of polyphenoloxidase and catalase activities in the rhizosphere and bulk soils to experimental warming (1.3 ℃) were examined during the growing season in a Sibiraea angustata scrub ecosystem on the eastern Qinghai-Tibetan Plateau, China. The results showed that the activities of polyphenoloxidase in rhizosphere and bulk soils in the middle growing season were significantly higher than those in the early or late growing season. The activities of catalase in the bulk soil increased gradually during the growing season, while they showed no seasonal changes in the rhizosphere soil. In the bulk soil, warming significantly increased the activity of polyphenoloxidase by 17.5% in the late growing season and increased that of catalase by 2.2% in the middle growing season, whereas it did not affect soil enzyme activities in early or late growing seasons. In the rhizosphere soil, warming only significantly increased the activities of polyphenoloxidase and catalase by 6.5% and 1.3% in the early growing season. The rhizosphere effect of soil polyphenoloxidase activity was positive throughout the growing season, while there was no obvious rhizosphere effect for soil catalase activity. Furthermore, warming significantly decreased the rhizosphere effect of soil polyphenoloxidase activity by 15.2% during the late growing season. These results indicated that the activities of polyphenoloxidase and catalase activities differed between rhizosphere and bulk soils, with consequences on the rhizosphere soil ecological processes under climate warming in the alpine scrub ecosystem on the eastern Qinghai-Tibetan Plateau.

Composition and function of soil fungal community during the establishment of Quercus acutissima (Carruth.) seedlings in a Cd-contaminated soil

This study was designed to explore the functions of soil fungal communities in the Cd tolerance of Q. acutissima seedling. Three Cd levels of 15, 30, and 40 mg kg−1 were set up using the soils collected from Q. acutissima forests. The benomyl was applied to inhibit the fungal communities in the soil. Following a 100-day pot cultivation of Q. acutissima seedlings, the plant growth, Cd content, N uptake, and fungal communities were evaluated. The results showed that the root dry weights were significantly reduced after the benomyl addition at the Cd concentrations of 30 and 40 mg kg−1. Root fungi colonization was enhanced under higher Cd concentrations when soil fungi are present (without the benomyl treatment). The fungi associated with root increased the Cd accumulation in the roots while decreased the Cd transfer to the shoot at 40 mg Cd kg−1. The 15N enrichment in root tip was positively correlated with enzyme activities of soil catalase and urease. And the activities of acid phosphatase, catalase, and urease were inhibited at each Cd level. The abundance of the dominant fungal genus differed in their response to Cd contamination. The ectomycorrhizal fungi of Tomentella and Cortinarius were identified under the higher Cd levels (40 mg kg−1). Our results implied Tomentella and Cortinarius could be applied to enhance the capacity of Quercus acutissima in the bioremediation of Cd polluted soil.

The inhibitory effect of cadmium and/or mercury on soil enzyme activity, basal respiration, and microbial community structure in coal mine–affected agricultural soil

The Cd and Hg contents in soils can be elevated due to coal mining. To estimate the effects of these two heavy metals on soil enzymes and the key microbial groups, coal mine–affected agricultural soils were cultured for 30 days with Cd and/or Hg. Soil enzyme activities were measured by a colorimetric method, and microbial abundance was assessed according to real-time quantitative PCR analysis of the 16S rRNA and 18S rRNA genes. In addition, the microbial communities were analyzed by Illumina sequencing. Heavy metals inhibited soil enzyme activities. For example, both Cd and Hg decreased 25.52–34.89% of the soil catalase activity; the highest level of Hg (30 mg kg−1) decreased 76.50–89.88% of the soil urease activity and 85.60–92.92% of the soil dehydrogenase activity; and the soil acid phosphatase activity significantly decreased by 15.18–32.64% under all the levels of Cd and decreased 17.09–30.32% under the high levels of the Cd–Hg combination (> 3 mg kg−1). In addition, increased Cd levels affected bacterial number more than fungal abundance; however, addition of Hg alone decreased the bacterial number but increased the fungal abundance. Furthermore, the bacterial communities but not fungal communities were altered by heavy metals. A total of 23 highly sensitive genera and 16 highly resistant genera were identified. The sensitive genera were assigned to Actinobacteria, Acidobacteria, Candidate division WS3, Chloroflexi, Gemmatimonadetes, Proteobacteria, and Thermotogae, while the resistant genera were affiliated to Bacteroidetes and Proteobacteria. Soils containing the highest level of the combination of Cd and Hg exhibited the lowest soil enzyme activities; bacterial communities were more sensitive to heavy metal contamination than fungi.

Response of Soil Microbes to Vegetation Restoration in Coal Mining Subsidence Areas at Huaibei Coal Mine, China.

Vegetation restoration is an available way to ameliorate degraded lands. In order to study the response of soil microbes to vegetation restoration in coal mining subsidence areas, the composition and distribution of soil microbes were discussed through three plots: unsubsided area (CA), new subsided area (NSA), and old subsided area (OSA) with different vegetation restoration time in Huabei coal mine. Meanwhile, changes in soil catalase and urease activity were explored and the correlation between soil bacteria, fungi, and environmental factors was analysed. The results demonstrated that Nitrospira was the dominant bacteria in all areas sampled. Microorganisms in the 0–20 cm and 40–60 cm soil layers of OSA had the highest Simpson index, whereas the index in NSA was lowest (at all soil depths). The catalase activity in NSA was significantly higher than that in CA, and there was no significant difference in catalase activity with soil depth, while the urease activity declined gradually with increasing soil depth. The urease activity in the 20–60 cm soil layer of NSA and OSA was significantly higher than that of CA. Furthermore, the distribution of bacteria was mainly affected by soil organic matter, available potassium, available phosphorus, and alkali-hydrolyzable nitrogen, whereas pH and catalase activity mainly affected fungal distribution. These results implied that soil catalase activity in NSA and urease activity in the 20–40 cm soil layer of NSA and OSA were significantly enhanced after vegetation restoration, and that long-term plant restoration could improve soil fertility and soil microbial community diversity in coal mining areas.

Effects of applying hyperaccumulator straw after planting grape seedlings on soil enzyme activity under cadmium stress

The effects of mulching with four hyperaccumulator plants Crassocephalum crepidioides, Galinsoga parviflora, Youngia japonica, and Gnaphalium affine straws on soil enzyme activity of grape seedlings under cadmium (Cd) stress were studied by a pot experiment. The results showed that mulching with four kinds of hyperaccumulators straws, the soil catalase, phosphatase and sucrase activity were increased compared with the monoculture. Only the straw-mulch Y. japonica decreased the soil urease activity, which decreased by 0.10%, and others treatments all increased the soil urease activity. In conclusion, the treatment of G. affine is the best, C. crepidioides followed it.

Effects of grape seedlings intercropping with post-grafting generation of two floricultural accumulator plants on soil enzymes activity under cadmium stress

Pot experiments were conducted to study the effects of grape seedlings intercropping with post-grafting generation of Cosmos sulphureus and Impatiens balsamina on soil enzymes activity under cadmium (Cd) stress. The result showed that: under Cd stress, grape intercropping with the post-grafting generation of C. sulphureus had significant effect, and grape intercropping with the generation of ungrafted C. sulphureus (C.CK) significantly increased soil catalase, soil urease and soil invertase activity compared to grape monoculture (MG). Grape intercropping with the post-grafting generation of self-rooted grafting by two uniform plant seedlings of I. balsamina (I.UG), the generation of ungrafted I. balsamina (I.CK) and the post-grafting generation of self-rooted grafting by the same one seedling of I. balsamina (I.SG) also significantly increased thses three enzymes activity compared to MG. Grape intercropping with I.UG was the most, and next were I.CK and I.SG. In conclusion, when grape intercropping with C.CK, I.UG, I.CK and I.SG, respectively, the enzymes activity all significantly increased.

Effect of roxarsone metabolites in chicken manure on soil biological property

Roxarsone (ROX), an organoarsenic feed additive, occurs as itself and its metabolites including As(V), As(III), monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA) in animal manure. Animal manure improves soil biological property, whereas As compounds impact microorganisms. The integral influence of animal manure bearing ROX metabolites on soil biological quality is not clear yet. Herein, the effect of four chicken manures excreted by chickens fed with four diets containing 0, 40, 80 and 120 mg ROX kg−1, on soil biological attributes. ROX addition in chicken diets increased total As and ROX metabolites in manures, but decreased manure total N, ammonium and nitrate. The elevated ROX metabolites in manures increased soil total As, As species and total N, and increased first and then decreased soil nitrate and nitrite, but did not affect soil ammonium in manure-applied soils. The promoting role of both soil As(III) and ammonium on soil microbial biomass carbon and nitrogen, respiration and saccharase activity, were exceeded or balanced by the inhibiting effect of soil nitrate. The suppression of soil catalase activity by soil As(V) was surpassed by the enhancement caused by soil nitrate and nitrite. Soil urease, acid phosphatase and polyphenol oxidase activities were not suitable bioindicators in the four manure-amended soils. Soil DMA did not affect soil biological properties, and MMA was not detectable in all manure-amended soils. The above highlights the complexity of joint influence of soil As and N on biological attributes. Totally, when ROX is used at allowable dose in chicken diet, soil biological quality would be suppressed in manure-amended soil.

Effects of biogas residues containing antibiotics on soil enzyme activity and lettuce growth.

To investigate the effects of biogas residues containing antibiotics on lettuce growth and soil enzyme activity, the antibiotics oxytetracycline and sulfadiazine were used as additives; two kinds of feedstocks including pig manure and straw were chosen. Results showed that the higher the concentrations of the antibiotics are, the stronger the inhibition of soil sucrase activity becomes. The activity of sucrose enzyme in the test group with a single concentration of 60mg/kg was significantly lower than the group that was treated with 0mg/kg. In the mass, the organic fertilizer containing antibiotics can improve the soil urease activity and increase the urease activity of the soil. In the growth phase, urease activity increased by 27% from 0.85mg NH3-N/(gday) in the blank group to 1.08 NH3-N/(gday) in the 0-mg test group. During all growing stages of lettuce, though the effects of the biogas residues containing oxytetracycline and sulfadiazine on the soil catalase activity were not obvious, the field application could inhibit the activity of soil catalase to some extent.

Effects of Solanum nigrum, Crassocephalum crepidioides and Bidens pilosa straws on the nutrients content of soil and grape seedlings under cadmium stress

In order to improve the nutrients absorption of grape seedlings under cadmium (Cd) stress, the effects of Solanum nigrum, Crassocephalum crepidioides and Bidens pilosa straws on the nutrients content of soil and grape seedlings under Cd stress were studied by pot experiment. According to the results, the activity of soil phosphatase, soil catalase and soil sucrose by soil application of straws observed higher than CK to varying degrees. And soil application of straws increased the contents of soil alkaline nitrogen and available phosphorus in different degrees, while soil application of B. pilosa straws decreased the content of soil available potassium. In addition, the soil application of straws had a certain promoting effect on the total nitrogen content, total phosphorus content and total potassium content of grape seedlings compared with the CK. Among all treatments, C. crepidioides straws maximized the nutrients content in the shoots of grape seedlings, which could provide reference for grape cultivation in Cd-contaminated areas.

Comparison of the effects of different maize straw returning methods on saline soil improvement

Using corn straw as raw material, the effects of three different ways of returning corn straw to the field, namely direct returning corn straw to the field, decomposed corn straw returning to the field and maize straw biochar returning to the field, on saline-alkali soil were studied by indoor culture. The results showed that maize straw directly returned to the field was the best way to improve the stability of saline-alkali soil aggregates; maize straw biochar returned to the field was the best way to reduce the alkalinity of saline-alkali soil; maize straw directly returned to the field and decomposed maize straw returned to the field enhanced the activity of soil urease and alkaline phosphatase, while reducing the activity of soil catalase. Maize straw biochar returned to field reduced soil urease activity and increased soil catalase activity, but had no significant effect on soil alkaline phosphatase activity.

Contrasting Effects of Chinese Fir Plantations of Different Stand Ages on Soil Enzyme Activities and Microbial Communities

Soil enzymes and microbial communities are key factors in forest soil ecosystem functions and are affected by stand age. In this study, we studied soil enzyme activities, composition and diversity of bacterial and fungal communities and relevant physicochemical properties at 0–10 cm depth (D1), 10–20 cm depth (D2) and 20–30 cm depth (D3) soil layers in 3-(3a), 6-(6a), 12-(12a), 18-(18a), 25-(25a), 32-(32a) and 49-year-old (49a) Chinese fir plantations to further reveal the effects of stand age on soil biotic properties. Spectrophotometry and high-throughput sequencing was used to assess the soil enzyme activity and microbial community composition and diversity of Chinese fir plantation of different stand ages, respectively. We found that soil catalase activity increased as the stand age of Chinese fir plantations increased, whereas the activities of urease, sucrase and β-glucosidase in 12a, 18a and 25a were lower than those in 6a, 32a and 49a. Shannon and Chao1 indices of bacterial and fungal communities first decreased gradually from 6a to 18a or 25a and then increased gradually from 25a to 49a. Interestingly, the sucrase and β-glucosidase activities and the Shannon and Chao1 indices in 3a were all lower than 6a. We found that the relative abundance of dominant microbial phyla differed among stand ages and soil depths. The proportion of Acidobacteria first increased and then decreased from low forest age to high forest age, and its relative abundance in 12a, 18a and 25a were higher than 3a, 32a and 49a, but the proportion of Proteobacteria was opposite. The proportion of Ascomycota first decreased and then increased from 6a to 49a, and its relative abundance in 12a, 18a and 25a was lower than 3a, 6a, 32a and 49a. Our results indicate that soil enzyme activities and the richness and diversity of the microbial community are limited in the middle stand age (from 12a to 25a), which is important for developing forest management strategies to mitigate the impacts of degradation of soil biological activities.

Evaluation of Soil-Applied Chemical Fungicide and Biofungicide for Control of the Fusarium Wilt of Chrysanthemum and Their Effects on Rhizosphere Soil Microbiota

Chemical fungicides are a frequently used intervention for the control of the Fusarium wilt of chrysanthemum, but are no longer considered environmentally friendly. However, the biofungicides offer one of the best alternatives to reduce the use of chemical fungicides. In this study, a series of two-year greenhouse experiments were conducted to evaluate the soil-applied chemical fungicide (dazomet, DZ) and biofungicide (biocontrol agent combined with B. subtilis NCD-2, BF) for controlling the Fusarium wilt of chrysanthemum and its effects on rhizosphere soil microbiota. The results indicated that DZ and BF showed good control efficacy of Fusarium wilt of chrysanthemum in the two-year application evaluation. However, the DZ treatment significantly decreased the soil catalase and urease activities compared with the control, while BF showed a significant increase in bacterium/fungus ratios (B/F), soil urease and acid phosphatase activities. Abundances of potential plant pathogens F. oxysporum, Rhizoctonia zeae and Rhizoctonia solani were also lower, while potential plant-growth-promoting micro-organisms like the Rhizobiales bacterium and Mariniflexile sp. were higher in the BF treatment than in the control. Our findings suggested that the overall effect of the soil biota on chrysanthemum growth was more positive and stronger in the BF treatment than in the DZ treatment.

Effects of soil amendments applied on cadmium availability, soil enzyme activity, and plant uptake in contaminated purple soil

Soil Cd pollution resulting from human activities has become a serious food safety concern. This study was to investigate the impacts of eight soil amendments including a humic acid material (XZ), three organic-inorganic combined materials (FY, PX and PLY) and four inorganic materials (FS, LIME, PLL and PL) on soil Cd availability, enzyme activity, and the uptake by vegetables under incubation, greenhouse and field conditions. Results showed that soil exchangeable Cd (EX-Cd) concentrations under four amendments (FY, XZ, PX, FS) significantly decreased by 12.10–13.59% after 20d treatments, and both PX and PLY resulted in reduced soil EX-Cd fraction while increased fractions of Fe-Mn oxides (OX-Cd), organic matter (OM-Cd) and residual (Res-Cd) in the Cd-contaminated purple soil. PX significantly reduced soil EX-Cd and carbonate-bound (CB-Cd) fractions by 4.4% and 11.4%, and decreased vegetable Cd uptake by 38.8% and 49.1% in greenhouse and field experiments, respectively. Moreover, PX elevated the activities of soil catalase, urease and saccharase by 15.7%, 53.6% and 48.2% in pot soil, which were ~4, ~5 and ~14 times higher those in field soil, respectively. This research demonstrated that PX could be an effective soil amendment to reduce the Cd health and ecological riskthe 1s in the Cd-contaminated purple soil.

A Negative Feedback Regulation of Replanted Soil Microorganisms on Plant Growth and Soil Properties of Peach

Replant disease is one of the main growth limiting factors, interfering with plant growth and yield of stone fruit trees such as peach trees. The ecological feedback mechanisms by replanted soil microbes regulating peach growth and soil structure are rarely known. In our study, rhizosphere soils collected from 18-year-old peach trees were used to plant new peach seedlings, and all soil microbes (R) and soil microbes with the size of < 100 μm (R<100) and < 40 μm (R<40) were applied into peach rhizosphere. After 90 days of microbial inoculation, compared with no microbe treatment (R0), the treatments such as R, R<40, and R<100 reduced plant growth performance (biomass, leaf number, plant height, and stem diameter) and root morphology (total length, projected area, surface area, diameter, and volume), with treatment R being the most inhibition of all other treatments. Similar response of treatment R was observed on changes in concentrations of chlorophyll a, chlorophyll b, and carotenoid. Interestingly, compared with R0 treatment, R<100 treatment produced a significant increase in glomalin-related soil protein (GRSP), percentage of water-stable aggregates in size of 0.25-0.5 mm, soil polyphenol oxidase activities and soil catalase activities. However, R treatment dramatically decreased the percentage of water-stable aggregates in size of 2-4 mm and soil peroxidase activities. Our results suggested that replanted soil microbes, especially with the size of < 100 μm, played a strong negative role on plant growth and rhizosphere biology of peach.

Dissipation of polycyclic aromatic hydrocarbons (PAHs) in soil amended with sewage sludge and sludge compost

In this study, greenhouse experiments were conducted under the condition of different amendment ratios and planting tall fescue (Festuca arundinacea). The amendment ratios of sewage sludge or sludge compost to soil were of 0, 10, 25, and 50% (w/w). The removal rates of PAH, catalase, and dehydrogenase activities of amended soil and accumulation of PAHs by vegetation were detected to investigate the differences of PAH dissipation in sludge-amended and compost-amended soils. The initial PAH concentrations in three amended soils increased with the more addition of sludge or compost. After 126-day experiment, maximum PAH removal rates were observed in sludge-amended and compost-amended soils with PAH concentration of about 200μgkg-1. And the removal of PAHs showed better efficiencies in compost soil rather than in sludge soil. The more catalase activity and dehydrogenase activity of soil were obtained, respectively, in sludge soil and compost soil. The results indicated that the mechanism of PAH dissipation in two types of amended soils were different. The abundant amount of microorganism dominated PAH dissipation in sludge soils, and PAHs dissipated mainly caused of intense activity of microorganism in compost soils. In addition, PAH accumulation in tall fescue suggested that the transference approach of PAHs was from soil to the roots, and then accumulated in the shoots of tall fescue. It was prone to store up more PAHs in vegetation in the condition of high molar weight of PAHs, more biomass of vegetation, and heavy PAH concentration in soil.

Effects of Different Levels of Irrigation with Reclaimed Water on Soil Enzyme Activity and Distribution of Thermotolerant Coliforms

This study aimed to discern the effect of different levels of irrigation with reclaimed water on soil enzyme activities and on the distribution of thermotolerant coliforms. The effects of two irrigation water qualities (reclaimed water and tap water) and two irrigation levels (full irrigation and insufficient irrigation) on soil enzyme activity and distribution of thermotolerant coliforms were studied through indoor soil column irrigation. Results indicated that:① Reclaimed water irrigation increased soil urease and invertase activity compared with tap water under the same irrigation conditions. Compared with insufficient irrigation with reclaimed water, full irrigation with reclaimed water significantly increased soil invertase activity and deep soil catalase activity. ② At the same irrigation level, the number of thermotolerant coliforms in soil significantly increased with reclaimed water irrigation. The number of thermotolerant coliforms in soil under full irrigation with reclaimed water was significantly higher than with insufficient irrigation using reclaimed water. The number of thermotolerant coliforms in surface soil of the four irrigated treatments was significantly higher than in the deep soil layer, and with progression of irrigation, the number of thermotolerant coliforms in the 0-60 cm soil layer decreased. ③ There was a significant positive correlation between the quantity of thermotolerant coliforms and the activity of soil urease and invertase, and between the quantity of thermotolerant coliforms and the activity of soil catalase. Reclaimed water therefore promoted enzyme activity that can promote transformation of C and N in soil. Reasonable irrigation with reclaimed water can therefore effectively control the number of thermotolerant coliforms in soil.