Scholarly article on topic 'Effect of Chlorophytum Comosum Growth on Soil Enzymatic Activities of Lead-contaminated Soil'

Effect of Chlorophytum Comosum Growth on Soil Enzymatic Activities of Lead-contaminated Soil Academic research paper on "Agriculture, forestry, and fisheries"

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{" Chlorophytum comosum " / "Lead (Pb)" / "Soil enzyme" / "Soil recovery"}

Abstract of research paper on Agriculture, forestry, and fisheries, author of scientific article — Youbao Wang, Dan Wu, Nannan Wang, Shan Hu

Abstract Through determined the activities of urease, phophatase, invertase and catalase by pot-planting, we researched the effect of Lead (Pb) on Soil enzyme Activities and Chlorophytum comosum on the effect of Pb- pollution soil. The results showed that Pb pollution apparently advanced the activities of catalase and invertase. Urease activities were all reduced with the increasing Pb concentration, the activity of urease appears to be more sensitive to pollution than that of other soil enzymes. The physicochemical indexes, activities of soil urease, phophatase, invertase and catalase, have responded differently between plant groups and control groups (P<0.05). In conclusion, urease activity of soil can be used as the main biochemical indicators of Pb-pollution soil. C. comosum demonstrated outstanding repairing effects in Pb-contaminated soil.

Academic research paper on topic "Effect of Chlorophytum Comosum Growth on Soil Enzymatic Activities of Lead-contaminated Soil"

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Environmental Sciences

Procedia Environmental Sciences 10 (2011) 709 - 714

2011 3rd International Conference on Environmental Science and Information Application Technology (ESIAT 2011)

Effect of Chlorophytum Comosum Growth on Soil Enzymatic Activities of Lead-contaminated Soil

Youbao Wanga*, Dan Wua, Nannan Wanga and Shan Hua

aCollege of Life Sciences, Anhui Normal University, Wuhu, Anhui, 241000, China

Abstract

Through determined the activities of urease, phophatase, invertase and catalase by pot-planting, we researched the effect of Lead (Pb) on Soil enzyme Activities and Chlorophytum comosum on the effect of Pb- pollution soil. The results showed that Pb pollution apparently advanced the activities of catalase and invertase. Urease activities were all reduced with the increasing Pb concentration, the activity of urease appears to be more sensitive to pollution than that of other soil enzymes. The physicochemical indexes, activities of soil urease, phophatase, invertase and catalase, have responded differently between plant groups and control groups (P < 0.05). In conclusion, urease activity of soil can be used as the main biochemical indicators of Pb-pollution soil. C. comosum demonstrated outstanding repairing effects in Pb-contaminated soil.

© 2011 Published by Elsevier Ltd. Selection and/or peer-review under responsibility of Conference ESIAT2011 Organi zation Committee.

Keywords:Chlorophytum comosum, Lead (Pb) , Soil enzyme, Soil recovery;

1. Introduction

Although heavy metals are naturally present in soils, contamination of soils comes from mostly industry and agricultural practices, combustion of fossil fuels and road traffic [1]. With the rapid development of industry, soil environment pollution becomes an increasingly important issue worldwide [2]. Heavy metal contamination in environment by industrial emissions and agricultural chemicals has a negative effect on animals, plant and physicochemical properties of soils [3]. Pollution of the soil environment with heavy metals also negatively influences on basal soil respiration rate and enzyme activities [4] depending on the soil pH, organic matter content and other chemical properties [5, 6].

As one of these heavy metal pollutants, we must give some attention to Lead (Pb), therefore, it is

* Corresponding author. E-mail address: wybpmm@126.com

1878-0296 © 2011 Published by Elsevier Ltd. Selection and/or peer-review under responsibility of Conference ESIAT2011 Organization Committee. doi:10.1016/j.proenv.2011.09.114

urgent to mitigate the Pb-polluted soils. Compared to physical and chemical remediation, phytoremediation is preferred because of its safety and lower cost [7]. Nowadays ornamental plants have become a new source of phytoremediation species for they not only are used for landscaping but also have practical applications in the air pollution monitoring and control [8].

In this study, we chose one popular ornamental plant C. Comosum to investigate the feasibility and scientific basis for repairing the Pb-polluted soil by C. Comosum.

2. Materials and methods

2.1 Sample collection

The C. comosum seedlings with prop-aerial roots were collected from a same matrix plant. Seedlings were collected in similar growth stage and taked for the experiment one week later. The soil for test were collected from the back hill in Anhui Normal University. The soil is yellow brown soil whose pH is 4.775, the electrical conductivity (EC) is 107.5^s-cm-1, oxidation reduction potential(ORP) is -150 mV, and the content of N, P and organic matter were 0.770*10-3, 0.949 *10-3, and 4.127*10-3. The soils were air-dried, grinded, and passed through a 3 mm sieve.

The soil samples were polluted artificially with 8 levels of Pb and added to plastic pots (®=12.5cm), 250g-pot-1. The treatments consisted of CK(a soil sample with no additional Pb), 250, 500, 750, 1000, 1250, 1500 and 2000 mg Pb (in the form of Pb(Ac)2-3H2O ) per kilogram of dry soil. After these soils in pot equilibrated at room temperature for two weeks, two seedlings were grown in each pot. Separately, set the pot without plant served as the control group. Each treatment had three replicates.

About 90 days later, C. comosum was carefully uprooted, and the surface soils (0-1 mm) were shaken off and collected. The residual roots were removed, and the soil samples were air-dried, grinded, and passed through a 0.15 mm sieve.

2.2 Soil analysis

The physical and chemical properties of the soil samples, such as pH, EC, organic matter, and ORP were determined according to the Environmental Monitoring of China (1992). The soil enzymatic activities are determined as per Guan (1986). To avoid cross-contamination of Pb with other metals, all receptacles had been soaked in 2% HNO3 for more than 24 h before used.

Data were analyzed by Microsoft Office Excel 2003 and SPSS 17.0 software package. Average values and standard deviations (S.D.) were calculated by the Microsoft Office Excel 2003. T-test was used to compare the otherness between different treatments and the correlation analysis and t-test were used to determine the difference among various groups of plant and soil samples.

3. Results and Discussion

3.1 Effects of Pb treatments on soil enzymatic activities

The soil enzymes are important components of soil, and soil enzymatic activities are correlated significantly with the soil fertility and efficiency of nutrition to plants. They are important indexes for determining the biological activity and productivity of soil [2]. We can Seen from table 1, phosphatase activity reached the maximum when Pb concentration was 500 mg-kg-1. Pb pollution apparently advanced the activities of catalase and invertase (it reduced slightly at 250 mg-kg-1 Pb concentration, and then increased markedly), nevertheless, urease activities were all reduced with the increasing Pb concentration.

Compared to the enzymatic activities of CK, the inhibiting rate of urease activities were 20.77%, 25.30%, 27.32%, 30.32%, 31.49%, 32.51% and 41.37%, respectively. The promoting rate of catalase activities were 5.33%, 16.67%, 7.20%, 9.33%, 33.33%, 37.33% and 89.33%, respectively.

Table 1. Effects of Pb treatments on soil enzymatic activities

Treatment (mg-kg"1) Invertase activity (0.1N NaS2Ö3, ml-g"1'day"1) Urease activity (NH3-N, mg-g'May"1) Phosphatase activity (P2O5, mg-100g"1-2h"1) Catalase activity (0.1N KMnO4, ml'g"1)

CK 1.768±0.072aa 95.251±1.527a 19338.026±1074.221ab 0.375±0.035ac

250 1.764±0.101a 75.472±0.055b 21426.896±4335.250ab 0.395±0.021ac

500 1.792±0.054a 71.153±0.164c 26893.224±2436.180bc 0.400±0.071ad

750 1.802±0.026a 69.225±2.672bcdef 22946.074±6138.407ab 0.402±0.003ac

1000 1.807±0.257a 66.372±0.600d 21765.998±2896.561ad 0.410±0.014acd

1250 1.854±0.566ab 65.254±0.763de 19704.256±671.388ac 0.500±0.071acd

1500 2.302±0.176b 64.290±0.382e 17954.488±537.111bd 0.515±0.064bc

2000 2.660±0.962ab 55.846±0.218f 18293.591±57.548ab 0.710±0.014bd

a Values followed by different letters for a given treatment are significantly different at p<0.05.

Generally, Pb2+ can directly interact with the active functional sites of the enzymes, and change their spatial conformation. When a heavy metal replace the active functional sites of an enzyme by combining with their mercapto, amino, or carboxyl, the enzymatic activity inhibition would occur, called enzymatic passivation. Activation may also appear when the combination of enzymatic active functional sites and their substrate were improved by heavy metals. On the other hand, some heavy metals such as Cd, Pb, and Zn can also constrain soil enzymatic activities by suppressing the growth of soil microbes or depressing the synthesis and secretion of enzymes [9].

3.2 Effects of C. comosum growth on soil enzymatic activities

We can Seen from table 2, the enzymatic activities of planted groups has the same trend with the enzymatic activities of control groups. Phosphatase activity reached the maximum when Pb concentration was 500 mg • kg-1. Pb pollution apparently advanced the activities of catalase and invertase (it reduced slightly at 250 mg • kg-1 Pb concentration, and then increased markedly), nevertheless, urease activities were all reduced with the increasing Pb concentration. That means the activity of urease appears to be

Table 2. Effects of C. comosum growth on soil enzymatic activities

Treatment (mg'kg-1) Invertase activity (0.1 NNaS2O3, ml-g"1-day"1) Urease activity (NH3-N, mg-g"1-day"1) Phosphatase activity (P2O5, mg-100g"1-2h"1) Catalase activity (0.1N KMnO4, ml'g"1)

CK 2.570±0.035aa 100.341±4.166a 24130.671±2306.108a 0.433±0.029a

250 2.542±0.086a 79.160±6.339b 24420.038±4511.143abc 0.483±0.029ab

500 2.642±0.278ac 72.169±3.678b 27386.053±6470.929abc 0.487±0.023b

750 2.706±0.389ac 72.117±4.021b 24754.619±1195.591a 0.500±0.087abc

1000 2.796±0.172ac 68.955±1.989b 22828.518±5710.230abc 0.513±0.055bc

1250 3.260±0.081bc 68.596±1.020b 20025.273±990.953b 0.533±0.058abc

1500 3.496±0.051bc 68.081±0.579b 18741.206±954.126cd 0.580±0.026c

2000 3.586±0.521ac 56.026±1.997c 18524.180±354.747bd 0.800±0.050d

a Values followed by different letters for a given treatment are significantly different at p<0.05.

more sensitive to pollution than that of other soil enzymes [10]. It was reported that urease is the most sensitive to the inhibition of single element and combined pollution of Cd, Pb, and Zn, which are some of the most important soil pollutants in China [11]. Urease activity of soil can be used as the main biochemical indicators of Pb-pollution soil.

Compared with the control group, the activities of invertase, urease, phosphatase, and catalase were all increased evidently, suggesting a significant difference between the planted and control groups (P<0.05) (Table 3). The increased rate of urease activities reached its peaks in 1500 mg-kg-1 Pb concentration, which are 1.058 times higher than the control groups. These demonstrating that C. comosum had some repairing effects on the activities of urease at every Pb concentration. We believe that C. comosum demonstrated outstanding repairing effects in Pb-contaminated soil.

Table 3. The Results of T-test of the difference of soil enzymatic activities between the planted group and the control group (n = 8)

Index Invertase activity Urease activity Phosphatase activity Catalase activity

T -12.870 4.950 2.765 9.036

P 0.000 0.002 0.028 0.000

3.3 Effects of Pb treatments on physical and chemical properties of soil

Table 4 exposed the changes of the physicochemical properties of the soil in control groups under different Pb concentrations. The physicochemical properties of soil are not only the base to determine the soil quality, but also the most direct index in evaluating the recovery effect of plants. Seen from our results, it was evident that the pH values of the control groups increased gradually from 4.775 to 5.170 with the increasing Pb concentration, and the ORP value increased from -150 to -130 mV, accounting for 2.007%, 2.007%, 2.676%, 6.355%, 7.692%, 11.706% and 13.378%, respectively. And the EC vauel increased at lower Pb concentrations but decreased at high Pb concentrations. In terms of nutrient component in soil, the Organic matter did not changed much, fluctuating within a certain range.

Table 4. Effects of Pb treatments on physical and chemical properties of soil

Treatment pH EC ORP Organic matter

(mg^kg-1) (^ cm-1) (mV) (%)

CK 4.775±0.007aca 107.5±0.707ac -150±0.707ac 4.063±0.127a

250 4.785±0.092bc 101.0±2.828ac -147±6.364ad 3.485±0.346ac

500 4.800±0.085bc 115.5±4.950bc -147±0.707ac 3.715±0.000bc

750 4.845±0.078bc 127.5±2.121b -146±0.707ac 3.760±0.079bc

1000 4.915±0.035ac 113.0±0.000abc -140±5.657bc 3.577±0.238ac

1250 4.920±0.127ab 106.0±4.243a -138±5.657bc 3.852±0.138bc

1500 5.020±0.028b 104.0±1.414ac -132±1.414bd 3.669±0.079bc

2000 5.170±0.099a 102.5±3.536a -130±3.536cd 3.715±0.000bc

a Values followed by different letters for a given treatment are significantly different at p<0.05.

3.4 Effects of C. comosum on physical and chemical properties of soil

Table 5 exposed the changes of the physicochemical properties of the soil in planted groups under different Pb concentrations. Seen from Table 4 and Table 5, the pH, EC and ORP values of the planted soils exhibited similar trend to those of control soil. The pH values in the planted soil were lower in every

Pb concentration than those of the control groups, it may be because the weak acid salt in the soil will be hydrolyzed and resulted in alkaline. Compared to the control group, the ORP and EC values in the planted soil were lower in every Pb concentration than those of the controls. The soil in plant groups was richer than the soil in control groups probably because the organic matter was decomposed by microorganisms. Table 6 showed the differences were significant (P<0.01) for pH, EC, ORP and Organic matter between the planted groups and the control groups.

Table 5. Effects of Pb treatments on physical and chemical properties of soil

Treatment pH EC ORP Organic matter

(mg^kg"1) cm"1) (mV) (%)

CK 4.660±0.208acdea 76.0±7.211abc -154±8.544ae 4.127±0.195ac

250 4.733±0.031a 76.3±2.309a -150±5.774ab 3.508±0.097b

500 4.750±0.026ac 86.7±2.082b -148±2.646adf 3.783±0.097a

750 4.770±0.035bc 77.7±6.429abc -147±7.767bf 3.852±0.195ab

1000 4.863±0.067bd 72.3±11.676abc -141±3.464ebg 3.783±0.292ab

1250 4.873±0.131abde 73.0±28.478abc -139±6.557cdg 3.921±0.097bc

1500 4.940±0.046d 74.3±0.577a -136±2.887cfg 3.646±0.097bc

2000 5.087±0.023e 81.7±1.528c -131±0.577cf 3.783±0.097bc

a Values followed by different letters for a given treatment are significantly different at p<0.05.

Table 6. The results of T-test of physical and chemical properties of the soil between the planted group and the control group (n = 8)

Index pH EC ORP Organic matter

T -8.307 -10.000 -4.000 -3.068

P 0.000 0.000 0.005 0.018

4. Conclusions

As a result, Pb pollution apparently inhibited urease activities, while the activities of catalase and invertase were both strengthened with the increasing Pb concentration. The Activitie of urease appears to be more sensitive to pollution than that of other soil enzymes. They can be used as the main biochemical indicators of Pb-contaminated soil. The soil enzymatic activities in the planted group increased significantly than those of the control group. Meanwhile, C. comosum can reduce soil EC and ORP. So it can say that C. comosum not only can bring economic benefits as one kind of ornamental plants but also be used as a plant species for phytoremediation, and it has the advantages such as high biomass, safe, low cost, little secondary pollution, etc. Therefore, there is a tremendous prospect of application for C. comosum in remediating Pb-pollution soils.

Acknowledgements

The author acknowledges the financial support from the National Natural Science Foundation of China (No. 31070401), the Key Foundation of Education Department of Anhui Province (No. KJ 2009 A 104, KJ 2010 A 152), the Foundation of the Provincial Key Laboratory of the Conservation and Exploitation of Biological Resources in Anhui and the Key Laboratory of Biotic Environment and Ecological Safety in Anhui Province.

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