Evaluation of Spatial Variability of Soil Arsenic Adjacent to a Disused Cattle-Dip Site, Using Model-Based Geostatistics

Abstract

This study investigated the spatial variability of total and phosphate-extractable arsenic (As) concentrations in soil adjacent to a cattle-dip site, employing a linear mixed model-based geostatistical approach. The soil samples in the study area (n = 102 in 8.1 m(2)) were taken at the nodes of a 0.30 × 0.35 m grid. The results showed that total As concentration (0-0.2 m depth) and phosphate-extractable As concentration (at depths of 0-0.2, 0.2-0.4, and 0.4-0.6 m) in soil adjacent to the dip varied greatly. Both total and phosphate-extractable soil As concentrations significantly (p = 0.004-0.048) increased toward the cattle-dip. Using the linear mixed model, we suggest that 5 samples are sufficient to assess a dip site for soil (As) contamination (95% confidence interval of ±475.9 mg kg(-1)), but 15 samples (95% confidence interval of ±212.3 mg kg(-1)) is desirable baseline when the ultimate goal is to evaluate the effects of phytoremediation. Such guidelines on sampling requirements are crucial for the assessment of As contamination levels at other cattle-dip sites, and to determine the effect of phytoremediation on soil As.

Cadmium Bioavailability, Uptake, Toxicity and Detoxification in Soil-Plant System

“…These dynamic processes are strongly affected by variations in redox conditions , cation exchange capacity (Jiang et al 2012), soil pH (Saeki and Kunito 2012), soil texture (Qi et al 2012), biological and microbial conditions (Joubert et al 2007), metal burdens (Gao et al 2009), organic and inorganic ligands (Niazi et al 2011a;Shahid et al 2014b;Austruy et al 2014), competing cations (Helios-Rybicka and Wójcik 2012) and temperature (Silber et al 2012) (Fig. 2).…”

Relationships between heavy metal concentrations in soils and reclamation history in the reclaimed coastal area of Chongming Dongtan of the Yangtze River Estuary, China

“…Wide use of agrochemicals may result in heavy metal enrichment in topsoils (Niazi et al 2011a, b;Plumlee 2002;Shomar 2006;Shan et al 2013). It is reported that commercial phosphate fertilizers, containing small amounts of heavy metal contaminants from their raw material-phosphate rock, were the major source leading to the heavy metal enrichment in agricultural soils (Mortvedt 1996;Nziguheba and Smolders 2008).…”

Mid-infrared spectroscopy and partial least-squares regression to estimate soil arsenic at a highly variable arsenic-contaminated site

“…The MIR-PLS-based predictive model has possible application to estimate the total soil As in situations where total As concentration is required for a large number of soil samples, for example (1) for monitoring the effect of phytoremediation technology on soil As content at a particular site (Niazi et al 2011c) or (2) to estimate the variability in total soil As at contaminated sites, such as cattledip sites (Niazi et al 2011a). The MIR-PLS model is site specific, and a more robust prediction model is needed for estimating total soil As at sites for other soil types and where As may also be present in different mineral forms, e.g.…”

“…Arsenic-contaminated soil samples were taken from a disused cattle-dip site located at Wollongbar as described elsewhere (Niazi et al 2011a). The soil samples were taken from three depths, i.e.…”

“…Potassium dihydrogen phosphate solution (0.5 M KH 2 PO 4 , 1:25 soil:solution ratio, 4 h shaking time at room temperature) was used to extract the specifically sorbed (bioavailable) As in the soil samples (Niazi et al 2011a). The concentration of phosphate-extractable As (mg As kg -1 soil dry weight) in the extracts was measured using a hydride generation atomic absorption spectrometer (HG-AAS, Varian Ò Spectraa 220Z).…”