Relationship between Heavy Metal Concentrations in Soils and Grasses of Roadside Farmland in Nepal

Abstract

Transportation activities can contribute to accumulation of heavy metals in roadside soil and grass, which could potentially compromise public health and the environment if the roadways cross farmland areas. Particularly, heavy metals may enter the food chain as a result of their uptake by roadside edible grasses. This research was conducted to investigate heavy metal (Cu, Zn, Cd, and Pb) concentrations in roadside farmland soils and corresponding grasses around Kathmandu, Nepal. Four factors were considered for the experimental design, including sample type, sampling location, roadside distance, and tree protection. A total of 60 grass samples and 60 topsoil samples were collected under dry weather conditions. The Multivariate Analysis of Variance (MANOVA) results indicate that the concentrations of Cu, Zn, and Pb in the soil samples are significantly higher than those in the grass samples; the concentrations of Cu and Pb in the suburban roadside farmland are higher than those in the rural mountainous roadside farmland; and the concentrations of Cu and Zn at the sampling locations with roadside trees are significantly lower than those without tree protection. The analysis of transfer factor, which is calculated as the ratio of heavy-metal concentrations in grass to those in the corresponding soil, indicates that the uptake capabilities of heavy metals from soil to grass is in the order of Zn > Cu > Pb. Additionally, it is found that as the soils’ heavy-metal concentrations increase, the capability of heavy-metal transfer to the grass decreases, and this relationship can be characterized by an exponential regression model.

Evaluation of accumulation and concentration of heavy metals in different urban roadside soil types in Miranda Park, Sydney

“…In most studies, traffic emission was recognized as the most important factor that would lead to significant quantities of metals deposited in roadside soils, for example, in China (Chen et al 2010;Wei and Yang 2010;Lu et al 2012), Turkey (Guney et al 2010;Kadıoğlu et al 2010), Greece (Massas et al 2009), Pakistan (Karim et al 2015), and Nigeria (Azeez et al 2014). Some studies have focused on the concentrations of heavy metals in roadside soils derived from vehicular emissions and demonstrated their detrimental impacts on the surrounding environment (Khan et al 2011;Yan et al 2012;Vural 2013). In most studies, specific roadside soil pollutant metals such as Pb, Zn, Cu, and Cd were mainly investigated because of their known effect on human health.…”

Traffic-Related Trace Element Accumulation in Roadside Soils and Wild Grasses in the Qinghai-Tibet Plateau, China

“…In Yan’s study [22] the order of TFs of the grasses in Nepal is Zn > Cu > Pb. It can be inferred that TFs varies from one grass species to another.…”

Evaluation of Pb, Cu, Zn and Cd Levels in Some Plants at Roadsides between Mafraq and Jerash, Jordan

“…In Nepal, the corresponding concentrations at roadside farmlands were 62.57 µg/g, 5.57 µg/g, 25.89 µg/g and 0.34 µg/g, respectively [2]. In a study conducted to establish the concentration of these metals in the neighboring Çorlu-Çerkezköy highway in Turkey, the levels were 20 µg/g, 1 µg/g and 8.2 µg/g for Zn, Pb and Cu, respectively [16].…”

“…The increment of traffic volume ultimately increases the accretions of such heavy metals. Vehicles emit a lot of toxic metals, which accumulate or build up along the roadside environments [2]. Consequently, heavy-metal pollution resulting from the increased traffic emissions may significantly contaminate the roadside crops, as well as plants that grow near the major highways [3].…”

“…For instance, copper toxicity may result in health complications such as kidney and liver damages, intestinal and stomach irritation and anemia [10]. Similarly, zinc toxicity may cause arteriosclerosis and pancreatic complications and damages, hence disturbing the body's protein metabolism [2]. As well, Pb and Cd metals may remain toxic even at very low concentration levels, leading to complications such as increased cancer risks [11].…”