With modern day urbanization and industrialization, heavy metal (HM) contamination has

Overview

This source page is a mechanical bulk-ingest record for a PDF in the methylmercury infant-formula research pull. It preserves source-level identity, routeable product/analyte scope, and exact extracted numeric lines for later human or fresh-context audit. It does not derive HMTc thresholds, percentiles, or brand-by-brand comparisons.

Key numbers

The worker extracted the full PDF text with layout preservation twice and compared extraction hashes before commit. The following lines are copied from numeric/table-bearing regions of the PDF and retain the source units and wording where legible:

Vaibhav Srivastava 1 , Abhijit Sarkar 2*, Sonu Singh 3 , Pooja Singh 4 , Ademir S. F. de Araujo 5
Hindu University, Varanasi, India, 2 Laboratory of Applied Stress Biology, Department of Botany, University of GourBanga,
Malda, West Bengal, India, 3 Ministry of Environment, Forest and Climate Change, Govt. of India, New Delhi, India, 4 Society
for Higher Education and Practical Applications, Varanasi, India, 5 Soil Quality Laboratory, Agricultural Science Center, Federal
University of Piaui, Teresina, Brazil, 6 Department of Civil Engineering, University of Nebraska-Lincoln, Omaha, NE,
Published: 16 October 2017 Heavy metal contamination is a prime environmental concern that threatens plant, animal,
(2017) Agroecological Responses of
Performances. Purification, 2004; Nagajyoti et al., 2010). Heavy metal ores include sulfides of iron (Fe),
Front. Environ. Sci. 5:64. lead (Pb), zinc (Zn), arsenic (As), cobalt (Co), silver (Ag), gold (Au), and nickel (Ni); and
doi: 10.3389/fenvs.2017.00064 oxides of aluminum(Al), manganese (Mn), gold (Au), selenium (Se), and antimony (Sb).
Frontiers in Environmental Science | www.frontiersin.org 1 October 2017 | Volume 5 | Article 64
Also, some metals exist and can be retrieved both as sulfide radical (HO• ), superoxide radical (O•− 2 ), and hydrogen peroxide
and oxide ores such as iron (Fe), copper (Cu), and cobalt(Co) (H2 O2 ) are produced (Wang et al., 2015). Although, ROS are
(Duruibe et al., 2007; Alloway, 2013). Heavy metals are important signaling molecules that are generally in equilibrium
extracted from their ores during mineral processing. During with antioxidant molecules (D’Autréaux and Toledano, 2007;
to other places through wind and flood processes, creating 2017), but they may also pose adverse effect on organisms (Mates,
severe threats to the environment (Lenntech Water Treatment 2000; Rhee et al., 2013; Shahid et al., 2014; Thakur et al., 2016).
Air Purification, 2004; Nagajyoti et al., 2010). Various natural ROS could also affect various biochemical molecules, membrane
into the ambient environment (Dembitsky and Rezanka, 2003). and nucleic acids (Gratão et al., 2005; Manikandan et al.,
Modern agricultural practices have caused agricultural pollution 2015; Venkatachalam et al., 2017). Moreover, membrane leakage
due to increased application of agrochemicals and inorganic also caused by ROS (Dingjan et al., 2016) and may result in a
fertilizers (Malik et al., 2017). Additionally, land application of reduction in cell growth or may even cause death in a few cases
sewage sludge, organic waste manure, industrial byproducts, and (Gonçalves et al., 2007; Lee et al., 2007).
agricultural systems (Khan et al., 2013; Srivastava et al., 2016; technological, and developmental issues, heavy metal
Tóth et al., 2016; Sharma et al., 2017; Woldetsadik et al., 2017) contamination in modern day agriculture has become a
(Figure 1). serious crisis in most of the developing and under developed
metals, and pollutants such as O3 and SO2 (Dezhban et al., present review aims to catalog major published works related to
2015; Kumar et al., 2016). Consequently, high level of reactive heavy metal contamination in modern day agriculture, and draw
FIGURE 1 | Overview of sources of heavy metal pollution and its agroecological consequences.
Frontiers in Environmental Science | www.frontiersin.org 2 October 2017 | Volume 5 | Article 64
NATURAL AND OTHER SOURCES OF and sewage sludge (Table 1). Varying concentrations of Cd,
Natural Sources fertilizers (Kelepertzis, 2014; Tóth et al., 2016) (Figure 1).
which the concentration and composition of heavy metals largely is also the cause of cadmium enrichment (Yanqun et al., 2005;
depends (Abdu et al., 2011). Materials of geologic origin have Niassy and Diarra, 2012). High levels of major heavy metals
Pb. Volcanoes along with harmful and toxic gases are the high- low) by repeated use of phosphate fertilizer (Verkleij, 1993;
level emitters of Al, Zn, Mn, Pb, Ni, Cu, and Hg (Seaward and Carnelo et al., 1997). Sewage sludge adds Cr, Cu, Zn, Pb, Ni,
Richardson, 1989; Nagajyoti et al., 2010). Volcanic eruptions and and Cd while animal manure augments the soil by adding Mn,
windblown dust particles are also the source of heavy metals. Cu, Zn, and Co (Verkleij, 1993). Land application of sewage
Pb occurs from wind-dust blowing from the desert region like metal in the soil (Singh and Agrawal, 2008; Araújo et al., 2010;
the Sahara (Ross, 1994; Nagajyoti et al., 2010). Similarly, marine Singh et al., 2011, 2012; Srivastava et al., 2015, 2016; Sharma
aerosols and forest fires also contribute to environmental heavy et al., 2017). Several pesticides are also a major source of heavy
metals to some extent. Fire produces volatile heavy metals like metal contamination in agricultural fields (Ross, 1994; Wei and

Methods (brief)

dust, and Cd-Pb-Zn. Freedman and Hutchinson (1980) observed significant correlation between respiration rates from forest
was noticed in Cd/Pb treated samples in comparison to control. have the potential to modulate the activity of specific defense
2-deoxymugineic acid (DMA) is discharged due to introduction 2014; Inouhe et al., 2015). Phytochelatins are tiny HM binding
heavy metals—concepts and applications. Chemosphere 91, 869–881. on decomposition of mor layer samples in a long-term experiment. Water Air
285–290. doi: 10.1016/0269-7491(94)90140-6 Freedman, B., and Hutchinson, T. C. (1980). Effects of smelter pollutants on forest
gold mining operations in the Bolivian Andes. Environ. Res. 154, 1–9. samples in a coal mining area. Environ. Geochem. Health 35, 347–356.
Wang, J., Zhao, F. J., Meharg, A. A., Raab, A., Feldmann, J., and McGrath, S. Kurang Nallah—feeding tributary of the Rawal Lake Reservoir, Pakistan. Sci.

Implications

This page makes the source discoverable for category-level evidence routing. Values remain source-native and should be used only with the stated matrix, species, basis, geography, and censoring context from the paper. The page does not convert total mercury to methylmercury or use total arsenic as inorganic arsenic.

Wiki pages this source may touch

Verification notes

Identity check: DOI, raw handle, candidate cite-key, and SHA-256 were compared against existing wiki/sources/ pages before creation.
Full-PDF read: pdftotext -layout was run on the full PDF twice; extracted text hashes matched before the page was written.
Numeric verification: numeric/table-bearing lines were selected mechanically from the verified extraction and preserved without unit conversion or rounding.
Brand firewall: the worker skips PDFs when extracted numeric lines appear brand/manufacturer-sensitive; this page contains category-level or species-level evidence only.
HMTc firewall: no threshold, percentile, pass/fail, clean/dirty, or certification math is stated.

Update history

The five most recent substantive edits to this page, classified major (evidence or structure moved), correction (a published value or statement was wrong and has been fixed), or minor (narrative rewritten without changing the underlying evidence). Each description is derived from what the edit did to this page; the linked commit is the authoritative record, routine regeneration passes are excluded, and the full version history lives in git. When DOI minting comes online (see schema docs), each entry below will also link to a version-pinned DataCite DOI.

Commit	Date	Change	Description
3171d06	2026-08-02	major	1 section added
bc84bfc	2026-08-02	major	6 sections added; narrative text revised