Heavy metals make soil enzymes 3 times weaker, says a soil scientist from RUDN University

August 26, 2020

Heavy metals suppress enzyme activity in the soil by 3-3.5 times and have especially prominent effect on the enzymes that support carbon and sulfur circulation. This was discovered by a soil scientist from RUDN together with his colleagues from Chile, Germany, the UK and Venezuela. The data obtained by the team can lead to more efficient use and fertilization of agricultural lands. The results of the study were published in the Science of the Total Environment journal.

Soil enzymes promote chemical reactions in soils, regulate cellular metabolism of soil organisms, participate in the decomposition of organic matter, and in the formation of humus. The quality and fertility of soil depend to a great extent on the activity of soil enzymes. Heavy metals, such as lead, zinc, cadmium, copper, and arsenic reduce the catalytic abilities of enzymes, thus interfering with the circulation of chemical elements.

Yakov Kuzyakov, a soil scientist from RUDN, together with his colleagues from Chile, Germany, UK and Venezuela analyzed 46 studies of the effect of heavy metals on soil enzymes. The authors of the work chose six enzymes and grouped them by the chemical elements they affected. For example, arylsulphatase is an enzyme that promotes reactions between water and sulfur-bearing acids. Therefore, it is associated with the biogeochemical cycle of sulfur. Similarly, other enzymes play their roles in the cycles of carbon, nitrogen, or phosphorus.

The team compared the activity of enzymes in healthy soils and ones contaminated with heavy metals. Intracellular enzymes (i.e. those found in the cells of plant roots and microbes) associated with carbon and sulfur cycles turned out to be the most sensitive to contamination. This might be due to the fact that extracellular enzymes bind with clays and organic matter which makes them more stable.

"Extracellular enzymes are more resistant due to the organo-mineral complex that stabilizes them in the soil environment and that intracellular enzymes lack. Enzymes that participate in nitrogen and phosphorus circulation showed medium to low activity reduction levels because they are predominantly extracellular," said Yakov Kuzyakov, a PhD in Biology, the Head of the Center for Mathematical Modeling and Design of Sustainable Ecosystems at RUDN.

Arylsulphatase and dehydrogenase, two enzymes in charge of gas exchange, glycolysis, and fermentation, were found the most sensitive. In soils contaminated with heavy metals, their activity reduced by 64% and 72% respectively, i.e. by 3-3.5 times. Some enzymes, such as beta-glucosidase and catalase, demonstrated reduced activity even when the concentration of heavy metals in the soil was very low (up to 200 mg per 1 kg). Unlike them, urease, an enzyme that plays a role in nitrogen circulation, is less sensitive to heavy metal concentration: its activity reduces by 10% at low levels of contamination and by up to 70% when contamination values are extremely high. Notably, the activity of acid phosphatases increases in the presence of small amounts of cadmium and copper in small amounts.

"Our study leads to a better understanding of the processes that cause soil systems to degrade under the influence of heavy metal contamination. The obtained results may help develop new methods of restoring contaminated soils," added Yakov Kuzyakov.
-end-
The participants of the study also represented the University of La Frontera (Chile), James Hutton Institute (UK), Venezuelan Institute for Scientific Research, University of Goettingen (Germany), and Kazan Federal University (Russia).

RUDN University

Related Science Articles from Brightsurf:

75 science societies urge the education department to base Title IX sexual harassment regulations on evidence and science
The American Educational Research Association (AERA) and the American Association for the Advancement of Science (AAAS) today led 75 scientific societies in submitting comments on the US Department of Education's proposed changes to Title IX regulations.

Science/Science Careers' survey ranks top biotech, biopharma, and pharma employers
The Science and Science Careers' 2018 annual Top Employers Survey polled employees in the biotechnology, biopharmaceutical, pharmaceutical, and related industries to determine the 20 best employers in these industries as well as their driving characteristics.

Science in the palm of your hand: How citizen science transforms passive learners
Citizen science projects can engage even children who previously were not interested in science.

Applied science may yield more translational research publications than basic science
While translational research can happen at any stage of the research process, a recent investigation of behavioral and social science research awards granted by the NIH between 2008 and 2014 revealed that applied science yielded a higher volume of translational research publications than basic science, according to a study published May 9, 2018 in the open-access journal PLOS ONE by Xueying Han from the Science and Technology Policy Institute, USA, and colleagues.

Prominent academics, including Salk's Thomas Albright, call for more science in forensic science
Six scientists who recently served on the National Commission on Forensic Science are calling on the scientific community at large to advocate for increased research and financial support of forensic science as well as the introduction of empirical testing requirements to ensure the validity of outcomes.

World Science Forum 2017 Jordan issues Science for Peace Declaration
On behalf of the coordinating organizations responsible for delivering the World Science Forum Jordan, the concluding Science for Peace Declaration issued at the Dead Sea represents a global call for action to science and society to build a future that promises greater equality, security and opportunity for all, and in which science plays an increasingly prominent role as an enabler of fair and sustainable development.

PETA science group promotes animal-free science at society of toxicology conference
The PETA International Science Consortium Ltd. is presenting two posters on animal-free methods for testing inhalation toxicity at the 56th annual Society of Toxicology (SOT) meeting March 12 to 16, 2017, in Baltimore, Maryland.

Citizen Science in the Digital Age: Rhetoric, Science and Public Engagement
James Wynn's timely investigation highlights scientific studies grounded in publicly gathered data and probes the rhetoric these studies employ.

Science/Science Careers' survey ranks top biotech, pharma, and biopharma employers
The Science and Science Careers' 2016 annual Top Employers Survey polled employees in the biotechnology, biopharmaceutical, pharmaceutical, and related industries to determine the 20 best employers in these industries as well as their driving characteristics.

Three natural science professors win TJ Park Science Fellowship
Professor Jung-Min Kee (Department of Chemistry, UNIST), Professor Kyudong Choi (Department of Mathematical Sciences, UNIST), and Professor Kwanpyo Kim (Department of Physics, UNIST) are the recipients of the Cheong-Am (TJ Park) Science Fellowship of the year 2016.

Read More: Science News and Science Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.