Fertilizers as a Source of Melamine and Cyanuric Acid in Soils: A Nationwide Survey in China

Abstract

The use of melamine and cyanuric acid in agriculture, industry, and consumer products has led to their ubiquitous environmental distribution. Nevertheless, little is known about the contamination of soils by melamine and cyanuric acid. Contamination of soils with melamine can lead to plant uptake and food chain transfer of these chemicals. In this study, concentrations of melamine and its three derivatives (cyanuric acid, ammeline, and ammelide) were determined in 98 surface soils and 16 fertilizers collected across China in 2017. Elevated concentrations of ∑melamine (sum of melamine and its three derivatives) were found in soils at concentrations that ranged from 8.67 to 2020 ng/g dry weight (dw), with an average value of 213 ng/g dw. Melamine accounted for 63% of the total concentrations in soils, which was followed by cyanuric acid (28%). Elevated concentrations of melamine and cyanuric acid were found in nitrogenous fertilizers such as nitrolime (n = 3; mean: 284 μg/g) and urea (n = 4; mean: 3160 μg/g), respectively. The measured concentrations in fertilizers were 3 to 4 orders of magnitude higher than those found in soils. Farmland soils (mean: 545 ng/g dw) contained significantly higher concentrations of ∑melamine than those of urban and background (forest) soils (92.5 ng/g dw). Our findings suggest that fertilizers are an important source of melamine and cyanuric acid in farm soils. Spatial distribution of melamine and cyanuric acid in soils showed the highest concentrations in eastern China, which corresponded well with population density, industrial, and agricultural activities. An ecological hazard assessment was performed of melamine in soils through a hazard quotient (HQ) approach. The mean HQ value was 0.35, and 7 of 98 surface soils had values above 1. Further studies are needed to discern uptake of melamine and its derivatives by crops and the fate of these chemicals in agricultural ecosystems.

Are Melamine and Its Derivatives the Alternatives for Per- and Polyfluoroalkyl Substance (PFAS) Fabric Treatments in Infant Clothes?

“…These ∑MEL concentrations mostly comprised of CYA with concentrations of up to 9120 ng/g, which was more than 2 orders of magnitude higher than that in conventional cotton (<MDL471 ng/g). Commercial nitrogen-based fertilizers, such as urea, nitrolime, and ammonia-based natural fertilizers, contain high levels of CYA (up to 250,000 ng/g) relative to MEL (up to 90,400 ng/g) and are used in growing organic cotton, which must meet strict federal regulations on the use of less toxic pesticides and fertilizers . Heavy use of nitrogen-based fertilizers containing large amounts of CYA may result in plant uptake ,, and possibly contribute to CYA levels in organic cotton.…”

Occurrence of Melamine and Its Derivatives in Breast Milk from the United States and Its Implications for Exposure in Infants

“…Our results suggest ongoing exposure to melamine and its derivatives in lactating women in the US. Melamine and its derivatives have been reported to occur in foodstuffs, soil, indoor dust, sewage sludge, and melamine-based tableware, , which are potential sources of exposure.…”

“…The mean FIR values for various age were reported in the U.S. Environmental Protection Agency's Exposure Factors Handbook. 32 The risks from melamine and cyanuric acid intake were estimated as hazard quotients (HQ), as shown in eq 2,…”

Cyanuric Acid Biodegradation via Biuret: Physiology, Taxonomy, and Geospatial Distribution

“…1). Cyanuric acid is produced indirectly as a contaminant of urea fertilizer, typically comprising 0.2% of the mass (4). With an estimated 60 billion kilograms of urea fertilizer used per year worldwide (5), approximately 120 million kilograms of cyanuric acid is applied in agricultural fields as a contaminant.…”

“…FIG4 Prevalence of biuH and atzEG within eight genes of atzD (A) and anywhere in genome assemblies (B) from the NCBI database. The largest circle represents total genomes with atzD, and each inner circle represents a subset of atzD genomes or gene regions with biuH and/or atzEG.…”