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Gao T, Tian H, Niu H, Wang Z, Dai Y, Megharaj M, He W. Soil phosphatase assay to evaluate arsenic toxicity should be performed at the soil's actual pH. Sci Total Environ 2023; 859:160184. [PMID: 36395829 DOI: 10.1016/j.scitotenv.2022.160184] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/29/2022] [Revised: 11/08/2022] [Accepted: 11/10/2022] [Indexed: 06/16/2023]
Abstract
Soil phosphatase is considered an indicator to assess soil arsenic (As) pollution. In the phosphatase activity determination, a fixed buffer value (pH 5-10) is commonly used for all soils, ignoring the soil's actual pH. Here, we determined the soil phosphatase activity of 20 soils under As stress at the soils' pH, and the As inhibition mechanism was also explored by the enzyme kinetics. Our results show that soil phosphatase activity was significantly inhibited under As stress. The inhibition rate in acid soils (39.2 %) was considerably higher than in alkaline soils (25.4 %) when As concentration was 600 mg kg-1. For alkaline soils, As inhibited phosphatase by competitive inhibition or linear mixed inhibition, while for acid soils, it was more complex, including linear mixed inhibition, non-competitive inhibition, and anti-competitive inhibition. Simultaneously, our results showed that the ecological dose (ED10) described by the partial inhibition model was far below than the complete inhibition model. According to the partial inhibition model, the ED10 of As ranged from 2.66 to 164.07 mg kg-1 for alkaline soils and 0.11 to 89.95 mg kg-1 for acid soils. Moreover, Vmax/Km of phosphatase is a more sensitive index for evaluating As contamination than Vmax in partial inhibition models. The ED10 obtained based on the relationship between Vmax/Km and As concentration was 0.64-34.75 mg kg-1 for acid soils and 8.48 to 20.16 mg kg-1 for alkaline soils. This also confirms Vmax/Km as a sensitive and ideal index for assessing As pollution under soils' actual pH. Furthermore, soil pH and cation exchange capacity are dominant factors affecting As inhibition on soil phosphatase. The above kinetic studies indicate that performing the assay by adjusting the buffer pH to the soil pH is essential for more accurately evaluating arsenic toxicity.
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Affiliation(s)
- Tiancong Gao
- College of Natural Resources and Environment, Northwest A&F University, Key Laboratory of Plant Nutrition and Agro-environment in Northwest China, Ministry of Agriculture, Yangling 712100, Shaanxi, China
| | - Haixia Tian
- College of Natural Resources and Environment, Northwest A&F University, Key Laboratory of Plant Nutrition and Agro-environment in Northwest China, Ministry of Agriculture, Yangling 712100, Shaanxi, China
| | - Huimin Niu
- College of Natural Resources and Environment, Northwest A&F University, Key Laboratory of Plant Nutrition and Agro-environment in Northwest China, Ministry of Agriculture, Yangling 712100, Shaanxi, China
| | - Ziqi Wang
- College of Natural Resources and Environment, Northwest A&F University, Key Laboratory of Plant Nutrition and Agro-environment in Northwest China, Ministry of Agriculture, Yangling 712100, Shaanxi, China
| | - Yunchao Dai
- College of Natural Resources and Environment, Northwest A&F University, Key Laboratory of Plant Nutrition and Agro-environment in Northwest China, Ministry of Agriculture, Yangling 712100, Shaanxi, China
| | - Mallavarapu Megharaj
- Global Centre for Environmental Remediation, College of Engineering, Science and Environment, University of Newcastle, Callaghan, NSW 2308, Australia
| | - Wenxiang He
- College of Natural Resources and Environment, Northwest A&F University, Key Laboratory of Plant Nutrition and Agro-environment in Northwest China, Ministry of Agriculture, Yangling 712100, Shaanxi, China.
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Ma X, Tian H, Dai Y, Yang Y, Megharaj M, He W. Respecting catalytic efficiency of soil arylsulfatase as soil Sb contamination bio-indicator by enzyme kinetic strategy. Environ Sci Pollut Res Int 2023; 30:17644-17656. [PMID: 36197608 DOI: 10.1007/s11356-022-23338-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/23/2022] [Accepted: 09/25/2022] [Indexed: 06/16/2023]
Abstract
Antimony (Sb), a toxic metalloid, is ubiquitous in the environment and threatens human and ecological health. Soil arylsulfatase (ARS) activity indicates heavy metal pollution. However, the enzyme's substrate concentration can affect the toxicity evaluation of heavy metals using enzyme activity. Enzyme kinetic parameters directly reflect the potency of heavy metals, and the magnitude of these parameters does not change with the substrate concentration of soil enzyme. In this work, seventeen soils were exposed to Sb contamination to investigate the change of kinetic parameters of soil arylsulfatase under Sb stress. Results showed that Sb inhibited soil arylsulfatase activity. The maximum reaction rate (Vmax) of soil arylsulfatase was reduced by 11.58-46.72% in 16 tested soils and unchanged in S15 when exposed to Sb. The Michaelis constant (Km) presented three trends: unchanged, increased by 28.46-41.27%, and decreased by 19.71-29.91% under Sb stress. The catalytic efficiency (Ka as the ratio of Vmax to Km) decreased by 12.56-55.17% in all soils except for S12 and S16. Antimony acted as a non-competitive and linear mixed inhibitor by decreasing ARS activity in S1-S12, S14, and S17-S18 soils, as an uncompetitive inhibitor in S13 and S16 soils and as a competitive inhibitor in S15. The competitive and uncompetitive inhibition constants (Kic and Kiu) were 0.058-0.142 mM and 0.075-0.503 mM. The ecological dose values of Sb to catalytic efficiency (Ka) of ARS (ED10-Ka) ranged from 50 to 1315 mg kg-1. Soil pH and total phosphorus (TP) contents were the dominant factors responsible for Sb toxicity on Ka by affecting the interaction of inhibitor (Sb) with enzyme-substrate (ES) complex. The findings of this study advance the current knowledge on Sb toxicity to soil enzymes and have significant implications for the risk assessment of Sb in soils.
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Affiliation(s)
- Xing Ma
- College of Natural Resources and Environment, Northwest A&F University, Key Laboratory of Plant Nutrition and Agro-environment in Northwest China, Ministry of Agriculture, Yangling, 712100, Shaanxi, China
| | - Haixia Tian
- College of Natural Resources and Environment, Northwest A&F University, Key Laboratory of Plant Nutrition and Agro-environment in Northwest China, Ministry of Agriculture, Yangling, 712100, Shaanxi, China
| | - Yunchao Dai
- College of Natural Resources and Environment, Northwest A&F University, Key Laboratory of Plant Nutrition and Agro-environment in Northwest China, Ministry of Agriculture, Yangling, 712100, Shaanxi, China
| | - Yizhe Yang
- Cultivated Land Quality and Agricultural Environment Protection Workstation of Shaanxi Province, Xi'an, 710000, Shaanxi, China
| | - Mallavarapu Megharaj
- Global Centre for Environmental Remediation, College of Engineering, Science and Environment, University of Newcastle, Callaghan, NSW, 2308, Australia
| | - Wenxiang He
- College of Natural Resources and Environment, Northwest A&F University, Key Laboratory of Plant Nutrition and Agro-environment in Northwest China, Ministry of Agriculture, Yangling, 712100, Shaanxi, China.
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Aponte H, Mondaca P, Santander C, Meier S, Paolini J, Butler B, Rojas C, Diez MC, Cornejo P. Enzyme activities and microbial functional diversity in metal(loid) contaminated soils near to a copper smelter. Sci Total Environ 2021; 779:146423. [PMID: 33752014 DOI: 10.1016/j.scitotenv.2021.146423] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/13/2021] [Revised: 03/07/2021] [Accepted: 03/08/2021] [Indexed: 06/12/2023]
Abstract
The monitoring of soil metal(loid) contamination is of global significance due to deleterious effects that metal(loid)s have on living organisms. Soil biological properties such as enzyme activities (EAs) are good indicators of metal(loid) contamination due to their high sensitivity, fast response, and low-cost. Here, the effect of metal(loid) contamination on physicochemical properties and microbial functionality in soils sampled from within 10 km of a Cu smelter is investigated. Soil composite samples were randomly taken within 2, 4, 6, 8 and10 km zones from a mining industry Cu smelter. The EAs of dehydrogenase (DHA), arylsulfatase (ARY), β-glucosidase, urease, and arginine ammonification (AA) were studied as indicators of metal(loid) contamination, which included the ecological dose (ED50) with respect to Cu and As contents. The community level physiological profile (CLPP), functional diversity, and catabolic evenness were evaluated based on the C-substrate utilisation. All EAs decreased in zones with high degrees of metal(loid) contamination, which also had low TOC and clay contents, reflecting long term processes of soil degradation. Positive and strong relationships between EAs and TOC were found. DHA and ARY activities decreased by approximately 85-90% in highly metal(loid) contaminated soils. DHA and AA showed significant ED50 values associated with available Cu (112.8 and 121.6 mg CuDTPA kg-1, respectively) and total As contents (30.8 and 31.8 mg As kg-1, respectively). The CLPP showed different metabolic profiles along the metal(loid) contamination gradients. Long-term stress conditions in soils close to industrial areas resulted in the decreasing of general biological activity, catabolic capacity, and functional diversity.
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Affiliation(s)
- Humberto Aponte
- Centro de Investigación en Micorrizas y Sustentabilidad Agroambiental, CIMYSA, Universidad de La Frontera, Temuco, Chile; Doctoral Program in Sciences of Natural Resources, Universidad de La Frontera, Temuco, Chile; Universidad de O'Higgins, Institute of Agri-Food, Animal and Environmental Sciences (ICA3), Laboratory of Soil Microbial Ecology and Biogeochemistry, San Fernando, Chile
| | - Pedro Mondaca
- Facultad de Ciencias Agronómicas y de los Alimentos, Pontificia Universidad Católica de Valparaíso, Valparaíso 2340025, Chile
| | - Christian Santander
- Centro de Investigación en Micorrizas y Sustentabilidad Agroambiental, CIMYSA, Universidad de La Frontera, Temuco, Chile
| | - Sebastián Meier
- Instituto de Investigaciones Agropecuarias (INIA), Centro de Investigación Regional de Investigación Carillanca, P.O. Box 58-D, Temuco, Chile
| | - Jorge Paolini
- Instituto Venezolano de Investigaciones Científicas (IVIC), Centro de Ecología, Altos de Pipe, Apdo. 21827, Caracas 1020-A, Venezuela
| | - Benjamin Butler
- The James Hutton Institute, Craigiebuckler, Aberdeen AB15 8QH, UK
| | - Claudia Rojas
- Universidad de O'Higgins, Institute of Agri-Food, Animal and Environmental Sciences (ICA3), Laboratory of Soil Microbial Ecology and Biogeochemistry, San Fernando, Chile
| | - María Cristina Diez
- Centre of Environmental Biotechnology, BIOREN, Universidad de La Frontera, Temuco, Chile
| | - Pablo Cornejo
- Centro de Investigación en Micorrizas y Sustentabilidad Agroambiental, CIMYSA, Universidad de La Frontera, Temuco, Chile.
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Li H, Tian H, Liu C, Lu G, Wang Z, Tan X, Jia H, Megharaj M, He W. The effect of arsenic on soil intracellular and potential extracellular β-glucosidase differentiated by chloroform fumigation. Sci Total Environ 2020; 727:138659. [PMID: 32325318 DOI: 10.1016/j.scitotenv.2020.138659] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/09/2019] [Revised: 04/09/2020] [Accepted: 04/10/2020] [Indexed: 06/11/2023]
Abstract
Arsenic (As) contamination of soil is a global issue of serious ecological and human health concern. For better use of soil enzymes as biological indicators of As pollution, the response of soil β-glucosidase in different pools of soil (total, intracellular and potential extracellular) to As(V) stress was investigated. Chloroform fumigation method was employed to distinguish the intracellular and potential extracellular β-glucosidase in three soils. The intracellular and potential extracellular β-glucosidase accounted about 79% and 21% of the total β-glucosidase activity in the tested soils. Moreover, it was found that the response of these three enzyme pools to As(V) pollution was different. Under the stress of 400 mg kg-1 As(V), the β-glucosidase activities decreased by 69%, 79%, and 28% for the total, intracellular and potential extracellular pools, respectively. The calculated median ecological dose (ED50) showed the highest value for potential extracellular β-glucosidase (19.55-27.63 mg kg-1 for total, 18.49-27.42 mg kg-1 for intracellular, and 32.27-52.69 mg kg-1 for potential extracellular β-glucosidase). As(V) exhibited an uncompetitive inhibition for total and intracellular β-glucosidase and non-competitive inhibition for potential extracellular enzyme. The inhibition constant (Kiu) is biggest for potential extracellular β-glucosidase among the three enzyme pools (0.61-0.79 mmol L-1 for total, 0.34-0.36 mmol L-1 for intracellular, and 4.01-23.90 mmol L-1 for potential extracellular β-glucosidase). Thus, compared to potential extracellular β-glucosidase, the total and intracellular β-glucosidases are more suitable for their use as sensitive indicators of As(V) pollution.
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Affiliation(s)
- Huayong Li
- College of Natural Resources and Environment, Northwest A&F University, Key Laboratory of Plant Nutrition and Agro-environment in Northwest China, Ministry of Agriculture, Yangling, 712100, Shaanxi, China
| | - Haixia Tian
- College of Natural Resources and Environment, Northwest A&F University, Key Laboratory of Plant Nutrition and Agro-environment in Northwest China, Ministry of Agriculture, Yangling, 712100, Shaanxi, China
| | - Chaoyang Liu
- College of Natural Resources and Environment, Northwest A&F University, Key Laboratory of Plant Nutrition and Agro-environment in Northwest China, Ministry of Agriculture, Yangling, 712100, Shaanxi, China
| | - Guannan Lu
- College of Natural Resources and Environment, Northwest A&F University, Key Laboratory of Plant Nutrition and Agro-environment in Northwest China, Ministry of Agriculture, Yangling, 712100, Shaanxi, China
| | - Ziquan Wang
- College of Natural Resources and Environment, Northwest A&F University, Key Laboratory of Plant Nutrition and Agro-environment in Northwest China, Ministry of Agriculture, Yangling, 712100, Shaanxi, China
| | - Xiangping Tan
- College of Natural Resources and Environment, Northwest A&F University, Key Laboratory of Plant Nutrition and Agro-environment in Northwest China, Ministry of Agriculture, Yangling, 712100, Shaanxi, China
| | - Hanzhong Jia
- College of Natural Resources and Environment, Northwest A&F University, Key Laboratory of Plant Nutrition and Agro-environment in Northwest China, Ministry of Agriculture, Yangling, 712100, Shaanxi, China
| | - Mallavarapu Megharaj
- Global Centre for Environmental Remediation, Faculty of Science, University of Newcastle, Callaghan, NSW 2308, Australia
| | - Wenxiang He
- College of Natural Resources and Environment, Northwest A&F University, Key Laboratory of Plant Nutrition and Agro-environment in Northwest China, Ministry of Agriculture, Yangling, 712100, Shaanxi, China.
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Wang Z, Tian H, Lei M, Megharaj M, Tan X, Wang F, Jia H, He W. Soil enzyme kinetics indicate ecotoxicity of long-term arsenic pollution in the soil at field scale. Ecotoxicol Environ Saf 2020; 191:110215. [PMID: 31978765 DOI: 10.1016/j.ecoenv.2020.110215] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/05/2019] [Revised: 12/11/2019] [Accepted: 01/13/2020] [Indexed: 05/27/2023]
Abstract
Information on the kinetic characteristics of soil enzymes under long-term arsenic (As) pollution in field soils is scarce. We investigated Michaelis-Menten kinetic properties of four soil enzymes including β-glucosidase (BG), acid phosphatase (ACP), alkaline phosphatase (ALP), and dehydrogenase (DHA) in field soils contaminated by As resulting from long-term realgar mining activity. The kinetic parameters, namely the maximum reaction velocity (Vmax), enzyme-substrate affinity (Km) and catalytic efficiency (Vmax/Km) were calculated. Results revealed that the enzyme kinetic characteristics varied in soils and were significantly influenced by total nitrogen (N) and total As, which explained 31.8% and 30.7% of the variance in enzyme kinetics respectively. Enzyme pools (Vmax) and catalytic efficiency (Vmax/Km) of BG, ACP and DHA decreased with elevated As pollution, while the enzyme affinity for substrate (Km) was less affected. Redundancy analysis and stepwise regression suggested that the adverse influence of As on enzyme kinetics may offset or weakened by soil total N and soil organic matter (SOM). Concentration-response fitting revealed that the specific kinetic parameters expressed as the absolute enzyme kinetic parameters multiplied by normalized soil total N and SOM were more relevant than the absolute ones to soil total As. The arsenic ecological dose values that cause 10% decrease (ED10) in the specific enzyme kinetics were 20-49 mg kg-1, with a mean value of 35 mg kg-1, indicating a practical range of threshold for As contamination at field level. This study concluded that soil enzymes exhibited functional adaptation to long-term As stress mainly through the reduction of enzyme pools (Vmax) or maintenance of enzyme-substrate affinity (Km). Further, this study demonstrates that the specific enzyme kinetics are the better indicators of As ecotoxicity at field-scale compared with the absolute enzyme parameters.
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Affiliation(s)
- Ziquan Wang
- College of Natural Resources and Environment, Northwest A&F University, Key Laboratory of Plant Nutrition and Agro-environment in Northwest China, Ministry of Agriculture, Yangling, 712100, Shaanxi, China; Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, 210008, China
| | - Haixia Tian
- College of Natural Resources and Environment, Northwest A&F University, Key Laboratory of Plant Nutrition and Agro-environment in Northwest China, Ministry of Agriculture, Yangling, 712100, Shaanxi, China
| | - Mei Lei
- Center for Environmental Remediation, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, 100101, China
| | - Mallavarapu Megharaj
- Global Centre for Environmental Remediation, Faculty of Science, University of Newcastle, Callaghan, NSW, 2308, Australia
| | - Xiangping Tan
- College of Natural Resources and Environment, Northwest A&F University, Key Laboratory of Plant Nutrition and Agro-environment in Northwest China, Ministry of Agriculture, Yangling, 712100, Shaanxi, China; Key Laboratory of Vegetation Restoration and Management of Degraded Ecosystems, South China Botanical Garden, Chinese Academy of Sciences, 723 Xingke Rd., Tianhe District, Guangzhou, 510650, China
| | - Fang Wang
- Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, 210008, China; University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Hanzhong Jia
- College of Natural Resources and Environment, Northwest A&F University, Key Laboratory of Plant Nutrition and Agro-environment in Northwest China, Ministry of Agriculture, Yangling, 712100, Shaanxi, China.
| | - Wenxiang He
- College of Natural Resources and Environment, Northwest A&F University, Key Laboratory of Plant Nutrition and Agro-environment in Northwest China, Ministry of Agriculture, Yangling, 712100, Shaanxi, China.
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Tan X, He Y, Wang Z, Li C, Kong L, Tian H, Shen W, Megharaj M, He W. Soil mineral alters the effect of Cd on the alkaline phosphatase activity. Ecotoxicol Environ Saf 2018; 161:78-84. [PMID: 29859411 DOI: 10.1016/j.ecoenv.2018.05.069] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/04/2018] [Revised: 05/07/2018] [Accepted: 05/24/2018] [Indexed: 06/08/2023]
Abstract
The toxicity of heavy metals (HMs) to soil enzymes is directly influenced by the status of the enzyme (free vs. immobilized on minerals) and the duration of exposure. However, little information is available on the interaction effect of HMs, mineral, and exposure time on soil enzyme activities. We investigated the interaction mechanism of alkaline phosphatase (ALP) with minerals (montmorillonite and goethite) and the response of free and immobilized ALP to cadmium (Cd) toxicity under different exposure times. The adsorption isotherms of ALP on both minerals were L-type. The maximum adsorption capacity of goethite for ALP was 3.96 times than montmorillonite, although both had similar adsorption constant (K). Goethite showed a greater inhibitory effect on ALP activity than montmorillonite. The toxicity of Cd to free- and goethite-ALP was enhanced with increasing exposure time, indicating a time-dependent inhibition. However, Cd toxicity to montmorillonite-ALP was not affected by the exposure time. The inhibition of Cd to soil enzyme activity is influenced by the properties of mineral complexes and the duration of exposure. A further understanding of the time pattern of HMs toxicity is helpful for accurately assessing the hazards of HMs to soil enzyme activity.
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Affiliation(s)
- Xiangping Tan
- College of Natural Resources and Environment, Northwest A&F University, Key Laboratory of Plant Nutrition and Agro-Environment in Northwest China, Ministry of Agriculture, Yangling 712100, China; Key Laboratory of Vegetation Restoration and Management of Degraded Ecosystems, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou 510650, China
| | - Yike He
- College of Natural Resources and Environment, Northwest A&F University, Key Laboratory of Plant Nutrition and Agro-Environment in Northwest China, Ministry of Agriculture, Yangling 712100, China
| | - Ziquan Wang
- College of Natural Resources and Environment, Northwest A&F University, Key Laboratory of Plant Nutrition and Agro-Environment in Northwest China, Ministry of Agriculture, Yangling 712100, China
| | - Chenghui Li
- College of Natural Resources and Environment, Northwest A&F University, Key Laboratory of Plant Nutrition and Agro-Environment in Northwest China, Ministry of Agriculture, Yangling 712100, China
| | - Long Kong
- College of Natural Resources and Environment, Northwest A&F University, Key Laboratory of Plant Nutrition and Agro-Environment in Northwest China, Ministry of Agriculture, Yangling 712100, China; School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Haixia Tian
- College of Natural Resources and Environment, Northwest A&F University, Key Laboratory of Plant Nutrition and Agro-Environment in Northwest China, Ministry of Agriculture, Yangling 712100, China
| | - Weijun Shen
- Key Laboratory of Vegetation Restoration and Management of Degraded Ecosystems, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou 510650, China
| | - Mallavarapu Megharaj
- Global Centre for Environmental Remediation, Faculty of Science, University of Newcastle, Callaghan, NSW 2308, Australia
| | - Wenxiang He
- College of Natural Resources and Environment, Northwest A&F University, Key Laboratory of Plant Nutrition and Agro-Environment in Northwest China, Ministry of Agriculture, Yangling 712100, China.
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Wang Z, Tian H, Lu G, Zhao Y, Yang R, Megharaj M, He W. Catalytic efficiency is a better predictor of arsenic toxicity to soil alkaline phosphatase. Ecotoxicol Environ Saf 2018; 148:721-728. [PMID: 29175755 DOI: 10.1016/j.ecoenv.2017.11.040] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/29/2017] [Revised: 11/11/2017] [Accepted: 11/16/2017] [Indexed: 06/07/2023]
Abstract
Arsenic (As) is an inhibitor of phosphatase, however, in the complex soil system, the substrate concentration effect and the mechanism of As inhibition of soil alkaline phosphatase (ALP) and its kinetics has not been adequately studied. In this work, we investigated soil ALP activity in response to As pollution at different substrate concentrations in various types of soils and explored the inhibition mechanism using the enzyme kinetics. The results showed that As inhibition of soil ALP activity was substrate concentration-dependent. Increasing substrate concentration decreased inhibition rate, suggesting reduced toxicity. This dependency was due to the competitive inhibition mechanism of As to soil ALP. The kinetic parameters, maximum reaction velocity (Vmax) and Michaelis constant (Km) in unpolluted soils were 0.012-0.267mMh-1 and 1.34-3.79mM respectively. The competitive inhibition constant (Kic) was 0.17-0.70mM, which was lower than Km, suggesting higher enzyme affinity for As than for substrate. The ecological doses, ED10 and ED50 (concentration of As that results in 10% and 50% inhibition on enzyme parameter) for inhibition of catalytic efficiency (Vmax/Km) were lower than those for inhibition of enzyme activity at different substrate concentrations. This suggests that the integrated kinetic parameter, catalytic efficiency is substrate concentration independent and more sensitive to As than ALP activity. Thus, catalytic efficiency was proposed as a more reliable indicator than ALP activity for risk assessment of As pollution.
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Affiliation(s)
- Ziquan Wang
- College of Natural Resources and Environment, Northwest A&F University, Key Laboratory of Plant Nutrition and Agro-environment in Northwest China, Ministry of Agriculture, Yangling, Shaanxi 712100, China; Rocky desertification research institute, Southwest Forestry University, Kunming, Yunnan 650224, China
| | - Haixia Tian
- College of Natural Resources and Environment, Northwest A&F University, Key Laboratory of Plant Nutrition and Agro-environment in Northwest China, Ministry of Agriculture, Yangling, Shaanxi 712100, China
| | - Guannan Lu
- College of Natural Resources and Environment, Northwest A&F University, Key Laboratory of Plant Nutrition and Agro-environment in Northwest China, Ministry of Agriculture, Yangling, Shaanxi 712100, China
| | - Yiming Zhao
- College of Natural Resources and Environment, Northwest A&F University, Key Laboratory of Plant Nutrition and Agro-environment in Northwest China, Ministry of Agriculture, Yangling, Shaanxi 712100, China
| | - Rui Yang
- College of Natural Resources and Environment, Northwest A&F University, Key Laboratory of Plant Nutrition and Agro-environment in Northwest China, Ministry of Agriculture, Yangling, Shaanxi 712100, China
| | - Mallavarapu Megharaj
- Global Centre for Environmental Remediation, Faculty of Science, University of Newcastle, Callaghan, NSW 2308, Australia
| | - Wenxiang He
- College of Natural Resources and Environment, Northwest A&F University, Key Laboratory of Plant Nutrition and Agro-environment in Northwest China, Ministry of Agriculture, Yangling, Shaanxi 712100, China.
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Tan X, Liu Y, Yan K, Wang Z, Lu G, He Y, He W. Differences in the response of soil dehydrogenase activity to Cd contamination are determined by the different substrates used for its determination. Chemosphere 2017; 169:324-332. [PMID: 27886534 DOI: 10.1016/j.chemosphere.2016.11.076] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/01/2016] [Revised: 11/01/2016] [Accepted: 11/15/2016] [Indexed: 06/06/2023]
Abstract
Dehydrogenase activity (DHA) is an important indicator of heavy metal toxicity in contaminated soils. Different instances of DHA were determined using various substrates and which could affect the description of heavy metal toxicity. Currently, too few investigations have been done on selecting appropriate substrates. This study employed indoor simulation to determine soil DHA and its response to external cadmium (Cd) using two substrates (TTC and INT). Hormesis for DHA obtained using the TTC method (DHA-TTC) in low Cd concentration was observed which was quickly inhibited in high Cd concentration. While DHA obtained using the INT method (DHA-INT) decreased slowly when Cd concentration increased. The DHA-TTC and DHA-INT in soils at Cd concentration of 500 mg kg-1 decreased 86% and 53%, respectively, compared to the control. The dose-response relationship of Cd to DHA can be well simulated using the logistic model (p < 0.01), which indicated DHA could be used to indicate soil Cd toxicity. Multiple stepwise regression analysis revealed that total organic matter (TOC) is the major factor influencing the toxicity of Cd to DHA-TTC, while TOC, pH and cation exchange capacity (CEC) are major factors influencing the toxicity of Cd to DHA-INT. The different responses of soil DHA-TTC and DHA-INT to Cd are due to the differences in electron transport chain characteristics between TTC and INT, as well as the influence of soil properties. Although both DHA-TTC and DHA-INT can monitor soil Cd contamination, DHA-INT is recommended as a superior bio-indicator to indicate and assess contamination of Cd in soil.
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Affiliation(s)
- Xiangping Tan
- College of Natural Resources and Environment, Northwest A&F University, Key Laboratory of Plant Nutrition and Agro-environment in Northwest China, Ministry of Agriculture, Yangling, 712100 Shaanxi, China
| | - Yanju Liu
- Global Centre for Environmental Research, The Faculty of Science and Information Technology, University of Newcastle, University Drive, Callaghan, NSW 2308, Australia; Cooperative Research Centre for Contamination Assessment and Remediation of the Environment (CRC CARE), Mawson Lakes, SA 5095, Australia
| | - Kaihong Yan
- Global Centre for Environmental Research, The Faculty of Science and Information Technology, University of Newcastle, University Drive, Callaghan, NSW 2308, Australia; Cooperative Research Centre for Contamination Assessment and Remediation of the Environment (CRC CARE), Mawson Lakes, SA 5095, Australia
| | - Ziquan Wang
- College of Natural Resources and Environment, Northwest A&F University, Key Laboratory of Plant Nutrition and Agro-environment in Northwest China, Ministry of Agriculture, Yangling, 712100 Shaanxi, China
| | - Guannan Lu
- College of Natural Resources and Environment, Northwest A&F University, Key Laboratory of Plant Nutrition and Agro-environment in Northwest China, Ministry of Agriculture, Yangling, 712100 Shaanxi, China
| | - Yike He
- College of Natural Resources and Environment, Northwest A&F University, Key Laboratory of Plant Nutrition and Agro-environment in Northwest China, Ministry of Agriculture, Yangling, 712100 Shaanxi, China
| | - Wenxiang He
- College of Natural Resources and Environment, Northwest A&F University, Key Laboratory of Plant Nutrition and Agro-environment in Northwest China, Ministry of Agriculture, Yangling, 712100 Shaanxi, China.
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Sanchez-Hernandez JC, Notario del Pino J, Domínguez J. Earthworm-induced carboxylesterase activity in soil: Assessing the potential for detoxification and monitoring organophosphorus pesticides. Ecotoxicol Environ Saf 2015; 122:303-312. [PMID: 26300118 DOI: 10.1016/j.ecoenv.2015.08.012] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2015] [Revised: 08/11/2015] [Accepted: 08/12/2015] [Indexed: 06/04/2023]
Abstract
Soil enzyme activities are attracting widespread interest due to its potential use in contaminant breakdown, and as indicators of soil deterioration. However, given the multiple environmental and methodological factors affecting their activity levels, assessment of soil pollution using these biochemical endpoints is still complex. Taking advantage of the well-known stimulatory effect of earthworms on soil microbes, and their associated enzyme activities, we explored some toxicological features of carboxylesterases (CbEs) in soils inoculated with Lumbricus terrestris. A microplate-scale spectrophotometric assay using soil-water suspensions was first optimized, in which kinetic assay parameters (Km, Vmax, dilution of soil homogenate, and duration of soil homogenization) were established for further CbE determinations. Optimal conditions included a soil-to-water ratio of 1:50 (w/v), 30-min of shaking, and 2.5mM of substrate concentration. As expected, CbE activity increased significantly in soils treated with L. terrestris. This bioturbed soil was used for exploring the role of CbE activity as a bioscavenger for organophosphorus (OP) pesticides. Soil treated with two formulations of chlorpyrifos revealed that CbE activity was a significant molecular sink for this pesticide, reducing its impact on soil microbial activity as shown by the unchanged dehydrogenase activity. Dose-dependent curves were adjusted to an exponential kinetic model, and the median ecological dose (ED50) for both pesticide formulations was calculated. ED50 values decreased as the time of pesticide exposure increased (14 d-ED50s=20.4-26.7 mg kg(-1), and 28 d-ED50s=1.8-2.3 mg kg(-1)), which suggested that chlorpyrifos was progressively transformed into its highly toxic metabolite chlorpyrifos-oxon, but simultaneously was inactivated by CbEs. These results were confirmed by in vitro assays that showed chlorpyrifos-oxon was a more potent CbE inhibitor (IC50=35.5-4.67 nM) than chlorpyrifos (0.41-0.84 μM). The results showed that earthworm-induced CbE activity is an efficient bioscavengers for OP pesticides, acting as a soil safeguarding system. Moreover, the simple dose-response curves against OP exposure suggest that this enzyme--combined with other enzyme activities (e.g., dehydrogenase)--may be a suitable biomarker of pesticide exposure.
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Affiliation(s)
- Juan C Sanchez-Hernandez
- Ecotoxicology Lab, Fac. Environmental Science and Biochemistry, University of Castilla-La Mancha, Toledo, Spain.
| | - J Notario del Pino
- Department of Animal Biology, Soil Science and Geology, University of La Laguna, Canary Islands, Spain
| | - Jorge Domínguez
- Departamento de Ecoloxía e Bioloxía Animal, Universidade de Vigo, 36310 Vigo, Spain
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