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Abstract [Objectives] This study was conducted to provide a scientific basis for the utilization of municipal solid waste resources， the remediation of contaminated substrates and the ecological safety of urban lawn planting.
[Methods] Graphene， multilayer graphene oxide and multiwalled carbon nanotubes were added to municipal solid waste （MSW） compost as turf substrate to determine the morphological indicators such as turfgrass biomass， chlorophyll contents and plant height.
[Results] There were no significant differences in the plant height of Festuca arundinacea between different treatment groups in the first 30 d. The effects of adding different carbon nanomaterials on the fresh and dry weights of F. arundinacea were not significantly different. The aboveground biomass of F. arundinacea was the largest after adding graphene oxide， and the underground fresh weight decreased significantly in the hydroxyl multiwalled carbon nanotube treatment compared with the control. As to the chlorophyll content， the graphene oxide treatment was the highest， but there were no significant differences between all the treatment groups and the control group.
[Conclusions] This study can provide data support for MSW compost substrate， lawn planting system and heavy metal pollutant passivating agents.
Key words Carbon nanomaterial; Passivator; MSW compostsubstrate; Festuca arundinacea
Remediation of pollution caused by municipal solid waste （MSW） and its resource utilization have attracted widespread attention， while MSW composting has also received great attention[1-2]. Compost is widely used in agricultural cultivation because it is rich in organic matter and a variety of substances needed for plant growth， which can effectively promote plant growth[3-4]. However， MSW contains heavy metal substances. When it is applied to soil as fertilizer， on the one hand， it will increase heavy metal concentration in the soil， and after the heavy metals are absorbed by crops， they enter the food web and cause heavy metal enrichment[5]. On the other hand， under the action of irrigation， heavy metals in compost enter groundwater through leaching， causing environmental pollution and bringing potential threats to human health[6]. It can be seen that the addition of an adsorbent to MSW compost will change the heavy metals from a migratory valence state to a stable state， which not only reduces the adsorption of plants， but also reduces the leakage to groundwater[7]. Studies have shown that carbon nanomaterials can effectively remediate heavy metals[8-9]， but most researches focus on the adsorption of heavy metals in the aqueous solution， and there are few studies on the optimization of heavy metalpassivating agents in the substrate. Some studies also have shown that carbon nanomaterials have a certain degree of biological toxicity， which is significantly related to their particle size. The smaller the nanoparticles， the greater the toxicity， so the screening of nanoparticle sizes is also very important[10]. The application of MSW compost to tturf system can not only promote turfgrass growth， but also can help landscape greening and solid waste reuse[11]and prevent heavy metals from entering the food chain. The lawn has important environmental purification and environmental remediation functions in the urban ecosystem， while Festuca arundinacea has a very strong regeneration capacity and high biomass， and its environmental purifier remediation effect is particularly obvious[12]. Therefore， in this study， F. arundinacea was used as a model plant to study the effects of such three kinds of carbon nanomaterials as graphene， graphene oxide and multiwalled carbon nanotubes on the growth of F. arundinacea in compost substrate. This study can provide support for MSW resource utilization， remediation of contaminatedsubstrate and optimization of heavy metalpassivating agents.
Materials and Methods
Experiment material
The MSW compost was taken from Tianjin Xiaodian Municipal Solid Waste Composting Plant， and sieved with a 2 mm sieve. Its basic physical and chemical properties were as follows： organic matter content 22.00%， bulk density 0.79g/cm3， porosity 67.98%， saturated water content 0.67 ml/g， pH 7.49， total nitrogen 0.57%， total phosphorus 0.34%， total potassium 1.21%， available phosphorus 0.078 g/kg， and C/N 8.37. And its metal contents were as follows： Ca 23.23 mg/kg， Fe 30.49 g/kg， Mg 5.78 g/kg， Cu 341.34 mg/kg， Zn 677.33 mg/kg， Pb 216.98 mg/kg， Cd 5.02 mg/kg， Mn 437.88 mg/kg， Cr 702.6 mg/kg and Ni 41.82 mg/kg.
Graphene was purchased from Nanjing Jicang Nano Co.， Ltd. It is black， in irregular flake structure with a size of 0.5-20.0 μm and a thickness of 5-25 nm. And it has a specific surface area of 40-60 m2/g， density of about 2.25 g/cm3， electrical conductivity of 8 000-10 000 S/m， and a carbon content greater than 99.5%.
Graphene oxide was purchased from Suzhou Hengqiu Nano Co.， Ltd. It is a black or brownyellow powder with an average thickness of 3.4-7.0 nm， a flake diameter of 10-50 μm and a layer number of 5-10 layers. And it has a specific surface area of 100-300 m2/g and purity greater than 90%.
Carboxylic multiwalled carbon nanotubes were purchased from Beijing Boyu Gaoke New Material Technology Co.， Ltd. They have a diameter of 20-40 nm and a length of 10-30 μm. And the nanotubes have aCOOH content of 1.43%， purity greater than 90wt%， an ash content lower than 8wt%， a specific surface area greater than 110 m2/g and electrical conductivity greater than 102 s/cm. Hydroxyl multiwalled carbon nanotubes were purchased from Beijing Boyu Gaoke New Material Technology Co.， Ltd. They have a diameter of 20-40 nm and a length of 10-30 μm. And the nanotubes have a OH content of 1.63%， purity greater than 90 wt%， an ash content lower than 8wt%， a specific surface area greater than 110 m2/g and electrical conductivity greater than 102 s/cm.
The turfgrass species was F. arundinacea， a common gramineous plant in the north.
Experiment design
F. arundinacea is planted in PVC columns 25 cm in height and 5 cm in diameter， with the bottom covered with doublelayer gauze. One control group （CK） and four treatment groups were set up in the experiment. The control group was not added with carbon nanomaterials， and the treatment groups were added with graphene （G）， graphene oxide （GO）， carboxylic multiwalled carbon nanotubes （CCH）， and hydroxyl multiwalled carbon nanotubes （COH）， respectively. In each PVC column， the bottom layer was filled with 30 g of sand， and the upper layer was filled with a mixed substrate of MSW compost and 1% of carbon nanomaterials. Each treatment had three replicates. The carbon nanomaterials and compost were mixed thoroughly and then loaded into the columns， and then stabilized for 7 d. During the stabilization period， irrigation was performed daily to maintain the soil water holding capacity. After the solidification， F. arundinacea was planted at a seeding rate of 0.2 g/cm2. The plants were then cultured at a room temperature of 18-25 ℃ and relative humidity of 35%-65%， and irradiated with natural light （6 856-27 090 LX）. The positions of the columns were changed frequently to ensureuniform illumination. The water content of the compost was maintained at 70% to ensure plant growth. The plants were harvestedon the 70thd， followed by determination of related indexes.
Determination of indexed
Determination of biomass
The aboveground part was dried at 108 ℃ for 20 min and then at 80 ℃ to constant weight. The underground part was cleaned with water， dried with filter paper， and dried at 80 ℃ to constant weight， and the biomass was finally weighed.
Plant height dynamics
The plant height was measured every 5 d from 5 d after sowing. Five plants with uniform growth were randomly selected in each column to measure the plant height， and the average value was taken as the plant height of each treatment.
Determination of relative chlorophyll content Before harvesting， the relative chlorophyll content was measured with a chlorophyll analyzer （SPAD520）. Ten uniform leaves were randomly selected from each column for determination， and the average value was used as the relative chlorophyll content of F. arundinacea[13].
Data processing
Oneway analysis of variance was performed to the data using SPSS 20.0 statistical software. Significant differences between the treatment groups and the control were determined using the Tukeys test at at the level of P<0.05. Microsoft Excel 2007 was used to plot the graphs.
Results and Analysis
Effects of carbon nanomaterials on plant height of F. arundinacea
The dynamics of F. arundinacea plant height is shown in Fig. 1. In the early stage of germination （5 d）， the plant height of the CCH treatment was the highest， and that of the G treatment group was the lowest. There were no significant differences in F. arundinacea plant height between the treatment groups in the first 30 d， but the treatments added with carbon nanomaterials all showed a decrease in plant height compared with the control subsequently. From 35 to 50 d， the plant height of the CCH treatment group was significantly reduced compared with the control， and the plant heights of the G， GO and COH treatment groups were lower than the control without significant differences.
CK is the control group; G is the addition of graphene; GO is the addition of graphene oxide; CCH is the addition of carboxylic multiwalled carbon nanotubes; and COH is the addition of hydroxyl multiwalled carbon nanotubes. The same below 2.2 Effects of carbon nanomaterials on the biomass of F. arundinacea
Table 1 showed that the effects of adding different carbon nanomaterials on the fresh and dry weights of F. arundinacea were not significantly different （P>0.05）. The addition of GO achieved the largest biomass， and the fresh weight was 8.52 g/column. After adding carbon nanomaterials， the fresh weight of the underground biomass decreased compared with the control. Among the different carbon nanomaterial treatments， the COH treatment group showed an underground fresh weight decreased significantly compared with the control group （P<0.05）， with a decrease of 21.30%， while other treatment groups were not significantly different from the control. There were no significant differences in the underground dry weight between the different treatments， but they all showed a decrease compared with the control. Agricultural Biotechnology 2020
Effects of carbon nanomaterials on the chlorophyll content of F. arundinacea
The GO treatment group showed the highest relative chlorophyll content， which was significantly different from those of the multiwalled carbon nanotube treatment groups， but had no significant differences from those of the control group and the G treatment group （Fig. 2）. There were no significant differences between all treatment groups and the control group. The lowest relative chlorophyll content was observed in the COH treatment， which was only 79.08% of the control group.
Conclusions and Discussion
There were no significant differences in F. arundinacea indicators such as biomass， chlorophyll content and plant height between the treatment groups and the control group， indicating that the addition of the carbon nanomaterials at the ratio of 1% did not inhibit the growth of turfgrass. It was further clarified that carbon nanomaterials had no negative effect on the growth of the synergistic remediation plant F. arundinacea within the added dosage of carbon nanomaterials， and the effectiveness of the carbon nanomaterials in the passivation of heavy metals in compost substrate could be ensured. In short， the present research can not only provide scientific basis for the effective remediation of substrate heavy metals with passivators， but also can provide support for the utilization of MSW compost resources.
References
[1] DUTTA S， PRIYA DN， CHAKRADHAR B， et al. Value added byproducts recovery from municipal solid waste[M]//Waste Valorisation and Recycling. Springer， Singapore， 2019： 71-80.
[2] LIMA JZ， RAIMONDI IM， SCHALCH V， et al. Assessment of the use of organic composts derived from municipal solid waste for the adsorption of Pb， Zn and Cd[J]. Journal of Environmental Management， 2018（226）： 386-399.
[3] NADEEM SM， IMRAN M， NAVEED M， et al. Synergistic use of biochar， compost and plant growth‐promoting rhizobacteria for enhancing cucumber growth under water deficit conditions[J]. Journal of the Science of Food and Agriculture， 2017， 97（15）： 5139-5145.
[4] BAHRAMISHARIF A， ROSE LE. Efficacy of biological agents and compost on growth and resistance of tomatoes to late blight[J]. Planta， 2019， 249（3）： 799-813.
[5] ISLAM MS， HOSSAIN MB， MATIN A， et al. Assessment of heavy metal pollution， distribution and source apportionment in the sediment from Feni River estuary， Bangladesh[J]. Chemosphere， 2018（202）： 25-32. [6] HUAN H， XU J， WANG J， et al. Groundwater pollution characteristics and source apportionment[M]//Groundwater Pollution Risk Control from an Industrial Economics Perspective. Springer， Singapore， 2018： 43-62.
[7] GOPINATH A， KRISHNA K， KARTHIK C. Adsorptive removal and recovery of heavy metal ions from aqueous solution/effluents using conventional and nonconventional materials[M]//Modern Age Waste Water Problems. Springer， Cham， 2020： 309-328.
[8] LEBRUN M， MIARD F， NANDILLON R， et al. Biochar effect associated with compost and iron to promote Pb and As soil stabilization and Salix viminalis L. growth[J]. Chemosphere， 2019（222）： 810-822.
[9] YU G， LU Y， GUO J， et al. Carbon nanotubes， graphene， and their derivatives for heavy metal removal[J]. Advanced Composites and Hybrid Materials， 2018， 1（1）： 56-78.
[10] SENGUPTA I， BHATTACHARYA P， TALUKDAR M， et al. Bactericidal effect of graphene oxide and reduced graphene oxide： Influence of shape of bacteria[J]. Colloids and Interface Science Communications， 2019（28）： 60-68.
[11] MA W， LIU F， CHENG X， et al. Environmental evaluation of the application of compost sewage sludge to landscaping as soil amendments： a field experiment on the grassland soils in Beijing[J]. Desalination and Water Treatment， 2015， 54（4-5）： 1118-1126.
[12] ZHU H， AI H， CAO L， et al. Transcriptome analysis providing novel insights for Cdresistant tall fescue responses to Cd stress[J]. Ecotoxicology and Environmental Safety， 2018（160）： 349-356.
[13] LI R， LI G， YUAN Y， et al. Effect of Se on some physiological characteristics of wheat seedling under Hg stress[J]. Ecology and Environmental Sciences， 2011， 20（5）： 975-979.
[Methods] Graphene， multilayer graphene oxide and multiwalled carbon nanotubes were added to municipal solid waste （MSW） compost as turf substrate to determine the morphological indicators such as turfgrass biomass， chlorophyll contents and plant height.
[Results] There were no significant differences in the plant height of Festuca arundinacea between different treatment groups in the first 30 d. The effects of adding different carbon nanomaterials on the fresh and dry weights of F. arundinacea were not significantly different. The aboveground biomass of F. arundinacea was the largest after adding graphene oxide， and the underground fresh weight decreased significantly in the hydroxyl multiwalled carbon nanotube treatment compared with the control. As to the chlorophyll content， the graphene oxide treatment was the highest， but there were no significant differences between all the treatment groups and the control group.
[Conclusions] This study can provide data support for MSW compost substrate， lawn planting system and heavy metal pollutant passivating agents.
Key words Carbon nanomaterial; Passivator; MSW compostsubstrate; Festuca arundinacea
Remediation of pollution caused by municipal solid waste （MSW） and its resource utilization have attracted widespread attention， while MSW composting has also received great attention[1-2]. Compost is widely used in agricultural cultivation because it is rich in organic matter and a variety of substances needed for plant growth， which can effectively promote plant growth[3-4]. However， MSW contains heavy metal substances. When it is applied to soil as fertilizer， on the one hand， it will increase heavy metal concentration in the soil， and after the heavy metals are absorbed by crops， they enter the food web and cause heavy metal enrichment[5]. On the other hand， under the action of irrigation， heavy metals in compost enter groundwater through leaching， causing environmental pollution and bringing potential threats to human health[6]. It can be seen that the addition of an adsorbent to MSW compost will change the heavy metals from a migratory valence state to a stable state， which not only reduces the adsorption of plants， but also reduces the leakage to groundwater[7]. Studies have shown that carbon nanomaterials can effectively remediate heavy metals[8-9]， but most researches focus on the adsorption of heavy metals in the aqueous solution， and there are few studies on the optimization of heavy metalpassivating agents in the substrate. Some studies also have shown that carbon nanomaterials have a certain degree of biological toxicity， which is significantly related to their particle size. The smaller the nanoparticles， the greater the toxicity， so the screening of nanoparticle sizes is also very important[10]. The application of MSW compost to tturf system can not only promote turfgrass growth， but also can help landscape greening and solid waste reuse[11]and prevent heavy metals from entering the food chain. The lawn has important environmental purification and environmental remediation functions in the urban ecosystem， while Festuca arundinacea has a very strong regeneration capacity and high biomass， and its environmental purifier remediation effect is particularly obvious[12]. Therefore， in this study， F. arundinacea was used as a model plant to study the effects of such three kinds of carbon nanomaterials as graphene， graphene oxide and multiwalled carbon nanotubes on the growth of F. arundinacea in compost substrate. This study can provide support for MSW resource utilization， remediation of contaminatedsubstrate and optimization of heavy metalpassivating agents.
Materials and Methods
Experiment material
The MSW compost was taken from Tianjin Xiaodian Municipal Solid Waste Composting Plant， and sieved with a 2 mm sieve. Its basic physical and chemical properties were as follows： organic matter content 22.00%， bulk density 0.79g/cm3， porosity 67.98%， saturated water content 0.67 ml/g， pH 7.49， total nitrogen 0.57%， total phosphorus 0.34%， total potassium 1.21%， available phosphorus 0.078 g/kg， and C/N 8.37. And its metal contents were as follows： Ca 23.23 mg/kg， Fe 30.49 g/kg， Mg 5.78 g/kg， Cu 341.34 mg/kg， Zn 677.33 mg/kg， Pb 216.98 mg/kg， Cd 5.02 mg/kg， Mn 437.88 mg/kg， Cr 702.6 mg/kg and Ni 41.82 mg/kg.
Graphene was purchased from Nanjing Jicang Nano Co.， Ltd. It is black， in irregular flake structure with a size of 0.5-20.0 μm and a thickness of 5-25 nm. And it has a specific surface area of 40-60 m2/g， density of about 2.25 g/cm3， electrical conductivity of 8 000-10 000 S/m， and a carbon content greater than 99.5%.
Graphene oxide was purchased from Suzhou Hengqiu Nano Co.， Ltd. It is a black or brownyellow powder with an average thickness of 3.4-7.0 nm， a flake diameter of 10-50 μm and a layer number of 5-10 layers. And it has a specific surface area of 100-300 m2/g and purity greater than 90%.
Carboxylic multiwalled carbon nanotubes were purchased from Beijing Boyu Gaoke New Material Technology Co.， Ltd. They have a diameter of 20-40 nm and a length of 10-30 μm. And the nanotubes have aCOOH content of 1.43%， purity greater than 90wt%， an ash content lower than 8wt%， a specific surface area greater than 110 m2/g and electrical conductivity greater than 102 s/cm. Hydroxyl multiwalled carbon nanotubes were purchased from Beijing Boyu Gaoke New Material Technology Co.， Ltd. They have a diameter of 20-40 nm and a length of 10-30 μm. And the nanotubes have a OH content of 1.63%， purity greater than 90 wt%， an ash content lower than 8wt%， a specific surface area greater than 110 m2/g and electrical conductivity greater than 102 s/cm.
The turfgrass species was F. arundinacea， a common gramineous plant in the north.
Experiment design
F. arundinacea is planted in PVC columns 25 cm in height and 5 cm in diameter， with the bottom covered with doublelayer gauze. One control group （CK） and four treatment groups were set up in the experiment. The control group was not added with carbon nanomaterials， and the treatment groups were added with graphene （G）， graphene oxide （GO）， carboxylic multiwalled carbon nanotubes （CCH）， and hydroxyl multiwalled carbon nanotubes （COH）， respectively. In each PVC column， the bottom layer was filled with 30 g of sand， and the upper layer was filled with a mixed substrate of MSW compost and 1% of carbon nanomaterials. Each treatment had three replicates. The carbon nanomaterials and compost were mixed thoroughly and then loaded into the columns， and then stabilized for 7 d. During the stabilization period， irrigation was performed daily to maintain the soil water holding capacity. After the solidification， F. arundinacea was planted at a seeding rate of 0.2 g/cm2. The plants were then cultured at a room temperature of 18-25 ℃ and relative humidity of 35%-65%， and irradiated with natural light （6 856-27 090 LX）. The positions of the columns were changed frequently to ensureuniform illumination. The water content of the compost was maintained at 70% to ensure plant growth. The plants were harvestedon the 70thd， followed by determination of related indexes.
Determination of indexed
Determination of biomass
The aboveground part was dried at 108 ℃ for 20 min and then at 80 ℃ to constant weight. The underground part was cleaned with water， dried with filter paper， and dried at 80 ℃ to constant weight， and the biomass was finally weighed.
Plant height dynamics
The plant height was measured every 5 d from 5 d after sowing. Five plants with uniform growth were randomly selected in each column to measure the plant height， and the average value was taken as the plant height of each treatment.
Determination of relative chlorophyll content Before harvesting， the relative chlorophyll content was measured with a chlorophyll analyzer （SPAD520）. Ten uniform leaves were randomly selected from each column for determination， and the average value was used as the relative chlorophyll content of F. arundinacea[13].
Data processing
Oneway analysis of variance was performed to the data using SPSS 20.0 statistical software. Significant differences between the treatment groups and the control were determined using the Tukeys test at at the level of P<0.05. Microsoft Excel 2007 was used to plot the graphs.
Results and Analysis
Effects of carbon nanomaterials on plant height of F. arundinacea
The dynamics of F. arundinacea plant height is shown in Fig. 1. In the early stage of germination （5 d）， the plant height of the CCH treatment was the highest， and that of the G treatment group was the lowest. There were no significant differences in F. arundinacea plant height between the treatment groups in the first 30 d， but the treatments added with carbon nanomaterials all showed a decrease in plant height compared with the control subsequently. From 35 to 50 d， the plant height of the CCH treatment group was significantly reduced compared with the control， and the plant heights of the G， GO and COH treatment groups were lower than the control without significant differences.
CK is the control group; G is the addition of graphene; GO is the addition of graphene oxide; CCH is the addition of carboxylic multiwalled carbon nanotubes; and COH is the addition of hydroxyl multiwalled carbon nanotubes. The same below 2.2 Effects of carbon nanomaterials on the biomass of F. arundinacea
Table 1 showed that the effects of adding different carbon nanomaterials on the fresh and dry weights of F. arundinacea were not significantly different （P>0.05）. The addition of GO achieved the largest biomass， and the fresh weight was 8.52 g/column. After adding carbon nanomaterials， the fresh weight of the underground biomass decreased compared with the control. Among the different carbon nanomaterial treatments， the COH treatment group showed an underground fresh weight decreased significantly compared with the control group （P<0.05）， with a decrease of 21.30%， while other treatment groups were not significantly different from the control. There were no significant differences in the underground dry weight between the different treatments， but they all showed a decrease compared with the control. Agricultural Biotechnology 2020
Effects of carbon nanomaterials on the chlorophyll content of F. arundinacea
The GO treatment group showed the highest relative chlorophyll content， which was significantly different from those of the multiwalled carbon nanotube treatment groups， but had no significant differences from those of the control group and the G treatment group （Fig. 2）. There were no significant differences between all treatment groups and the control group. The lowest relative chlorophyll content was observed in the COH treatment， which was only 79.08% of the control group.
Conclusions and Discussion
There were no significant differences in F. arundinacea indicators such as biomass， chlorophyll content and plant height between the treatment groups and the control group， indicating that the addition of the carbon nanomaterials at the ratio of 1% did not inhibit the growth of turfgrass. It was further clarified that carbon nanomaterials had no negative effect on the growth of the synergistic remediation plant F. arundinacea within the added dosage of carbon nanomaterials， and the effectiveness of the carbon nanomaterials in the passivation of heavy metals in compost substrate could be ensured. In short， the present research can not only provide scientific basis for the effective remediation of substrate heavy metals with passivators， but also can provide support for the utilization of MSW compost resources.
References
[1] DUTTA S， PRIYA DN， CHAKRADHAR B， et al. Value added byproducts recovery from municipal solid waste[M]//Waste Valorisation and Recycling. Springer， Singapore， 2019： 71-80.
[2] LIMA JZ， RAIMONDI IM， SCHALCH V， et al. Assessment of the use of organic composts derived from municipal solid waste for the adsorption of Pb， Zn and Cd[J]. Journal of Environmental Management， 2018（226）： 386-399.
[3] NADEEM SM， IMRAN M， NAVEED M， et al. Synergistic use of biochar， compost and plant growth‐promoting rhizobacteria for enhancing cucumber growth under water deficit conditions[J]. Journal of the Science of Food and Agriculture， 2017， 97（15）： 5139-5145.
[4] BAHRAMISHARIF A， ROSE LE. Efficacy of biological agents and compost on growth and resistance of tomatoes to late blight[J]. Planta， 2019， 249（3）： 799-813.
[5] ISLAM MS， HOSSAIN MB， MATIN A， et al. Assessment of heavy metal pollution， distribution and source apportionment in the sediment from Feni River estuary， Bangladesh[J]. Chemosphere， 2018（202）： 25-32. [6] HUAN H， XU J， WANG J， et al. Groundwater pollution characteristics and source apportionment[M]//Groundwater Pollution Risk Control from an Industrial Economics Perspective. Springer， Singapore， 2018： 43-62.
[7] GOPINATH A， KRISHNA K， KARTHIK C. Adsorptive removal and recovery of heavy metal ions from aqueous solution/effluents using conventional and nonconventional materials[M]//Modern Age Waste Water Problems. Springer， Cham， 2020： 309-328.
[8] LEBRUN M， MIARD F， NANDILLON R， et al. Biochar effect associated with compost and iron to promote Pb and As soil stabilization and Salix viminalis L. growth[J]. Chemosphere， 2019（222）： 810-822.
[9] YU G， LU Y， GUO J， et al. Carbon nanotubes， graphene， and their derivatives for heavy metal removal[J]. Advanced Composites and Hybrid Materials， 2018， 1（1）： 56-78.
[10] SENGUPTA I， BHATTACHARYA P， TALUKDAR M， et al. Bactericidal effect of graphene oxide and reduced graphene oxide： Influence of shape of bacteria[J]. Colloids and Interface Science Communications， 2019（28）： 60-68.
[11] MA W， LIU F， CHENG X， et al. Environmental evaluation of the application of compost sewage sludge to landscaping as soil amendments： a field experiment on the grassland soils in Beijing[J]. Desalination and Water Treatment， 2015， 54（4-5）： 1118-1126.
[12] ZHU H， AI H， CAO L， et al. Transcriptome analysis providing novel insights for Cdresistant tall fescue responses to Cd stress[J]. Ecotoxicology and Environmental Safety， 2018（160）： 349-356.
[13] LI R， LI G， YUAN Y， et al. Effect of Se on some physiological characteristics of wheat seedling under Hg stress[J]. Ecology and Environmental Sciences， 2011， 20（5）： 975-979.