Accumulation of cadmium and uranium in arable soils in Switzerland

Abstract

Mineral phosphorus (P) fertilizers contain contaminants that are potentially hazardous to humans and the environment. Frequent mineral P fertilizer applications can cause heavy metals to accumulate and reach undesirable concentrations in agricultural soils. There is particular concern about Cadmium (Cd) and Uranium (U) accumulation because these metals are toxic and can endanger soil fertility, leach into groundwater, and be taken up by crops. We determined total Cd and U concentrations in more than 400 topsoil and subsoil samples obtained from 216 agricultural sites across Switzerland. We also investigated temporal changes in Cd and U concentrations since 1985 in soil at six selected Swiss national soil monitoring network sites. The mean U concentrations were 16% higher in arable topsoil than in grassland topsoil. The Cd concentrations in arable and grassland soils did not differ, which we attribute to soil management practices and Cd sources other than mineral P fertilizers masking Cd inputs from mineral P fertilizers. The mean Cd and U concentrations were 58% and 9% higher, respectively, in arable topsoil than in arable subsoil, indicating that significant Cd and U inputs to arable soils occurred in the past. Geochemical mass balances confirmed this, indicating an accumulation of 52% for Cd and 6% for U. Only minor temporal changes were found in the Cd concentrations in topsoil from the six soil-monitoring sites, but U concentrations in topsoil from three sites had significantly increased since 1985. Sewage sludge and atmospheric deposition were previously important sources of Cd to agricultural soils, but today mineral P fertilizers are the dominant sources of Cd and U. Future Cd and U inputs to agricultural soils may be reduced by using optimized management practices, establishing U threshold values for mineral P fertilizers and soils, effectively enforcing threshold values, and developing and using clean recycled P fertilizers.

An Interdisciplinary Approach to Evaluate the Mobility and Toxicity of Cadmium in a Soil–Plant System

“…The results of X-ray diffraction revealed kaolinite (Si 4 Al 4 O 10 (OH) 8 ) and illite ((K, H 2 O) 2 (Si) 8 (Al, Mg, Fe) 4 (O) 20 (OH) 4 ) in argillaceous and silty fractions, while goethite (α-FeOOH) and hematite (α-Fe 2 O 3 ) were exclusively found among clay particles. Feldspar ((K, Na, Ca)(Si, Al) 4 O 8 ) and quartz (SiO 2 ) were also identified; feldspar was only found in the sandy fraction, and quartz in all granulometric fractions.…”

“…The transfer of cadmium to plants is regulated by the physical and chemical characteristics of soils . Consequently, plants grown in argillaceous soils contaminated with cadmium can assimilate limited (sublethal) amounts of this pollutant, thus maintaining their normal growth.…”

“…[3] The transfer of cadmium to plants is regulated by the physical and chemical characteristics of soils. [4][5][6] Consequently, plants grown in argillaceous soils contaminated with cadmium can assimilate limited (sublethal) amounts of this pollutant, thus maintaining their normal growth. However, if the considered plant is an edible plant, this raises public health concerns, since cadmium concentrations that are sublethal to a plant can be harmful to humans.…”

Phosphorus Processing—Potentials for Higher Efficiency

“…On the contrary, some of these components are undesirable or classified as pollutant that may hamper the beneficial use of fertilizers or the recycling potential of waste streams, in particular regarding the use of phosphogypsum [33,34] In a linear economy and a business as usual scenario, these resources are extracted as long as they can be sold and supplied in response to an apparent market demand and directly contribute to the profits of the phosphate industry. In a Circular Economy, solutions should be sought by joint efforts By implementing enhanced heat recovery system (e.g., Outotec's Heros ® ), the conversion efficiency of sulfur combustion could be increased from close to 58% to 71%, a big step in resource efficiency.…”

Impact of cadmium levels in fertilisers on cadmium accumulation in soil and uptake by food crops

“…At present however, it is unclear how fast and to what degree a reduction of Cd levels in soil can be obtained so as to reduce exposure of Cd below the TWI. Recent inventories in Switzerland (Bigalke et al, 2017) and New Zealand for example showed that inputs of Cd inputs to arable cropping systems have been reduced, but the response of the soil Cd level to such reduced inputs is slow or absent.…”