Accumulation and transformation of atmospheric mercury in soil

https://doi.org/10.1016/S0048-9697(02)00569-7Get rights and content

Abstract

Field investigation and simulating experiments were carried out for understanding the accumulation and transformation of mercury in soil in relation to the deposition of atmospheric mercury. A positive correlation between the atmospheric mercury concentration and the content of mercury in soil was observed in the field investigation, with the correlation coefficient being 0.741** (n=52). The mercury content in soil decreased with the increasing distance from the mercury emission source. Simulated experiment demonstrated that the higher the mercury content in air was, the higher was the amount of mercury accumulated in soil, which was in accordance with the results found from the field investigation. Transformation process occurred once mercury deposited into the soil. Analyses of soil samples exposed to air with mercury contents of 796.4±186.3 ng/m3 for 2 months indicated that 24.58–26.86% of total mercury deposited into the soil existed in Hg0 form, 0.10–0.12% in active form, 14.56–18.75% in HCl-dissoluble form, 0.86–5.84% in organic-bound form and 52.64–55.29% in residual form.

Introduction

Mercury (Hg) is a special highly toxic non-essential heavy metal element. It has been considered as a global pollutant due to its ability to undergo long distance transportation in the atmosphere. Thus, great attention has been paid to the study of mercury behaviors in the environment internationally since the 1980s. Global emissions of Hg had been estimated to be approximately 6000–7500 t/yr, more than 50–75% of which was due to anthropogenic activities (Nriagu, 1989, Lindqvist et al., 1991). After being transported some distance in the atmosphere, the emissive Hg would come back to the earth's surface through wet and dry deposition. More than 90% of it entered terrestrial ecosystem (Lindqvist et al., 1991, Fitzgerald, 1995) in which the soil was the largest Hg recipient.

Hg in atmosphere consists primarily of two main forms, element Hg (Hg0) and divalent Hg compounds, either in the gaseous phase or bound to particles. Hg0(g) is the predominated species (>95%) in the atmosphere in ambient air (Iverfeldt, 1991, Lindqvist et al., 1991). In the past 20 years, global atmospheric Hg0 concentrations appear to have increased at an annual rate of 1.5% for the Northern Hemisphere and 1.2% for the Southern Hemisphere (Slemr and Langer, 1992). Correspondingly, the atmospheric Hg deposition rates have also increased (Johnson, 1987, Lindqvist et al., 1991, Swain et al., 1992). The potential danger levels of Hg accumulation in food chain would be increased (Mou and Qing, 1995, Mou and Tang, 1992, Temmerman et al., 1986). Thus, it is of great importance to understand the relationship between atmospheric Hg and the Hg accumulation in soil.

In this paper, the processes involved in the accumulation and transformation of atmospheric Hg in the soil will be discussed based on the studies conducted both in laboratory and field investigations.

Section snippets

Field investigation

Field investigations were carried out at the urban district, the suburb and the outer suburb of Chongqing City, an important industrial city in southwest China. One hundred and fifty-eight samples of air were collected by gold traps with Model QC-II air-collection instrument. The working principle of gold traps for the collection of Hg is based on the formation of amalgamation with Hg0 and surface adsorption of Hg(II) (Brosset and Inerfeldt, 1989, Dumarey et al., 1985, Schroeder et al., 1985).

Effect of atmospheric Hg on the accumulation of mercury in soil

The Hg contents of soils in the investigated region were in the range of 0.064–0.881 mg/kg, with an average content of 0.219±0.178 mg/kg. Comparison of the Hg contents of soils with the concentrations of atmospheric Hg at the soil sampling site showed that the Hg content of soil increased with the increasing concentration of atmospheric Hg, and there was a positive correlation between them with a correlation coefficient being 0.741** (n=52). The result demonstrated that atmospheric Hg obviously

Acknowledgements

The authors would like to acknowledge the financial support for this work that was provided by the International Atomic Energy Agency (IAEA), research contract no. PRC-10874/R1.

References (16)

  • E. Temmerman et al.

    Sensitive determination of gaseous mercury in air by cold vapour atomic fluorescence spectrometry after amalgamation

    Anal Chem Acta

    (1990)
  • C. Brosset et al.

    Interaction of solid gold with mercury in ambient air

    Water, Air, Soil Pollut

    (1989)
  • R. Dumarey et al.

    Comparison of the collection and adsorption efficiency of activated charcoal, silver and gold for the determination of vapor-phase atmospheric mercury

    Anal Chem

    (1985)
  • X.B. Feng et al.

    The distribution of various mercury species in soil

    Chinese J Geochem

    (1997)
  • W.F. Fitzgerald

    Is mercury increasing in the atmosphere? The need for an atmosphere mercury network (AMNET)

    Water, Air, Soil Pollut

    (1995)
  • Å. Iverfeldt

    Occurrence and turnover of atmospheric mercury over the Nordic countries

    Water, Air, Soil Pollut

    (1991)
  • M.G. Johnson

    Trace element loading to sediments of fourteen Pntario lakes and correlation with concentrations in fish

    Can J Fish Aquat Sci

    (1987)
  • O. Lindqvist et al.

    Mercury in the Swedish environment

    Water, Air, Soil Pollut

    (1991)
There are more references available in the full text version of this article.

Cited by (0)

View full text