Effectiveness of different soil amendments to reduce the Pb and Zn extractability and plant uptake in soils contaminated by anticorrosion paints beneath pylons

Abstract

Red lead (Pb3O4)‐ and ZnO‐containing anticorrosion paints in the past have been extensively applied to high‐voltage steel pylons which has led to heavy metal (HM) soil contaminations in their vicinity. Since pylons are commonly found on agricultural land, there is a potential risk of HM plant uptake. This is promoted by the fact that in contrast to the moderate total Pb contents (several 100 mg kg–1) in three nutrient‐poor and acidic pylon soils the Pb amounts extractable with NH4NO3 were extremely high, reaching almost 20% of total Pb. A 18‐week field pot trial (three harvests in a six‐week interval) using Lolium multiflorum was conducted to study the HM plant uptake and the efficiency of the four soil additives, lime (LI), Novaphos (NP), water‐treatment sludge (WS), and ilmenite residue (IR) in reducing the plant uptake and NH4NO3‐extractability of Pb and Zn in the soils. Lead concentrations in L. multiflorum shoots grown in the untreated soils reached maximum values of 128 mg (kg dry weight)–1. Novaphos was most efficient in decreasing shoot Pb (–90%) followed by LI (–78%) and WS (–73%). For Zn, too, LI (–82%), NP, and WS (both –66%) substantially reduced plant uptake. Ilmenite residue was generally only poorly efficient. The dry‐matter yield in the NP, LI, and WS treatments was significantly increased. While the relationship between Pb‐NH4NO3 and Pb‐plant was high when considering the three harvests separately (R > 0.93) a poor relationship (R = 0.63) exists over all harvests together. This was attributed to different transpiration rates affecting the HM flux into the plants, since the temperature regime changed greatly during the cultivation period. For Zn, no such close relationship between the NH4NO3‐extractable soil fraction and shoot Zn was found, most likely due to antagonistic effects from Mg which greatly varied in the three soils.

Unique Characteristics of Pb in Soil Contaminated by Red Lead Anti-Corrosion Paint

“…In contrast to the relatively moderate total Pb content of the three pylon soils, the Pb amounts extractable with NH 4 NO 3 are high, reaching almost 15% of total Pb in soil B. These high Pb NH 4 NO 3 -extractabilities and the respective high Pb plant uptake were already described and discussed by Brokbartold et al (2012a;2012b), coming to the conclusion that the assumed extremely low water solubility of red lead (Haynes, 2010) is apparently not valid in soil environments. The presence of anglesite in the anti-corrosion paint can be explained by Pb interacting with SO 4 2− in rainwater from SO 2 emissions (Sanusi et al, 1996).…”

“…In a greenhouse experiment, the Pb uptake by loose-leaf lettuce plants cultivated on red-lead-paint-contaminated soil limed to neutral pH still resulted in Pb concentrations twice as high as the permissible level for leafy vegetables of the European Union of 0.30 mg kg −1 fresh weight (EC, 2006), although the total Pb soil content of about 350 mg kg −1 was relatively low (Brokbartold et al, 2012a). In plant experiments under field conditions using Italian ryegrass cultivated on red lead anti-corrosion paint-contaminated pylon soils the Pb content in the plant biomass exceeded the permitted maximum Pb-content in green fodder (30 mg kg −1 at a moisture content of 12%) defined in the EC directive 2005/87/EC (EC, 2005) in two soils by up to about 350% (Brokbartold et al, 2012b). Until now, this high solubility and bioavailability are poorly understood since Pb 3 O 4 is considered insoluble in water (Haynes, 2010), with a reported water solubility of 6.86 ng L −1 (McKinley et al, 2002).…”

“…Pb derived from red lead anti-corrosion paint is an exception since earlier studies have shown that Pb derived from red lead anti-corrosion paint represents a Pb source that provides substantial amounts of extractable and plant available Pb, even if (a) the total Pb soil content (150 to 750 mg kg −1 ) would normally cause no major concern in terms of plant uptake; (b) at soil pH around 5, whereby Pb contaminations from other sources are generally immobile and uncritical in terms of plant availability and uptake (Brokbartold et al, 2012a;Brokbartold et al, 2012b), but so far the reasons for this remain obscure. In a greenhouse experiment, the Pb uptake by loose-leaf lettuce plants cultivated on red-lead-paint-contaminated soil limed to neutral pH still resulted in Pb concentrations twice as high as the permissible level for leafy vegetables of the European Union of 0.30 mg kg −1 fresh weight (EC, 2006), although the total Pb soil content of about 350 mg kg −1 was relatively low (Brokbartold et al, 2012a).…”

Trace Elements in the Soil-Plant Systems of Copper Mine Areas-A Case Study From Murgul Copper Mine From the Black Sea Region of Turkey

“…The single most important factor affecting trace element availability is soil pH. For cationic species, lower pH values result in higher mobility and thus availability [72][73][74][75][76], while the opposite is true for anionic species [76,77]. Epstein [60] has reported that aluminyum is usually toxic to plants in acid soils.…”

Effects of paper sludge addition on the bioavailability and distribution of Pb in contaminated soil

“…[7,8] Soil amendments, mainly by adding materials to soil to improve soil quality, are often used to reduce the metal concentration and bioavailability. [9][10][11][12] Commonly used soil amendments include organic matter, [13] calcium hydroxide, [14] phosphates, [15] and nanometallic materials. [16] Municipal sludge has been demonstrated to have several advantages for immobilization of heavy metals in soil, including low cost and high effectiveness.…”