Heavy Metals, Phosphorus and Some Other Elements in Urban Soils of Hangzhou City, China

Health implications of inhaling and/or ingesting dust particles with high concentrations of heavy metals from urban soils are a subject of intense concern. Understanding the geochemistry of these metals is key to their effective management. Total concentrations of heavy metals,phosphorus (P) and 8 other elements from topsoil samples collected at 82 locations in Hangzhou City were measured to:a) assess their distribution in urban environments; and b) understand their differentiation as related to land use. Metal mobility was also studied using a three-step sequential chemical fractionation procedure. About 8.5%,1.2%,3.6%,11.0% and 30.3% of the soil samples had Cd,Cr,Cu,Pb,and Zn concentrations,respectively,above their allowable limits for public and private green areas and residential use. However,in commercial and industrial areas,most samples had metal concentrations below their allowable limits. Statistical analyses revealed that the 16 measured elements in urban soils could be divided into four groups based on natural or anthropic sources using a hierarchical cluster analysis. Additionally,Cu,Pb,and P showed similar spatial distributions with significant pollution in commercial zones,suggesting vehicle traffic or commercial activities as dominant pollutant sources. Also,Cd,Co,Cr,Ni,Zn,Mn and Fe had the highest concentrations in industrial locations,signifying that industrial activities were the main sources of these seven metals. Moreover,the data highlighted land-use as a major influence on heavy metal concentrations and forms found in topsoils with large proportions of soil Cd,Co,Cr,and Ni found in residual fractions and soil Cu,Pb and Zn mainly as extractable fractions.

Copper and Zinc Enrichment in Different Size Fractions of Organic Matter from Polluted Soils

Bioavailability of heavy metals in soil organic matter depends on itscomponents. Characterization of heavy metal distributions in different fractions of soil organicmatter is needed for better understanding of the fate of heavy metals. This study investigated theaccumulation and partitioning of copper and zinc among different size particulate organic matter(POM) fractions in polluted soils from a former iron ore processing site in western Shaoxing County,Zhejiang Province. Physical fractionations were carried out to separate soil primary particlesaccording to their size and density. Copper and Zn had a heterogeneous distribution among soilparticle fractions. Copper and Zn were significantly (p < 0.05) enriched in the POM fractions. >0.05 mm POM and < 0.05 mm fine soil fractions were mainly responsible for Cu and Zn retention insoils. The POM fraction contained up to 1 322 mg Cu kg^(-1) and 1115 mg Zn kg^(-1) and the fine soilfraction contained up to 422 mg Cu kg^(-1) and 537 mg Zn kg^(-1). The total POM fraction wasresponsible for 15.8%-41.2% and 12.2%-31.7% of the total amount of Cu and Zn, respectively, in thepolluted soils. The percentages of Cu and Zn associated with organic matter in < 0.05 mm fine soilfractions for the polluted soils ranged from 14.1% to 24.5%, and 5.4% to 15.8%, respectively.Accumulation of soil organic matter could increase enrichment of Cu (or Zn) in the POM fractions.Also, Cu provided a greater enrichment in the POM fractions than Zn.

Sorption of dissolved organic matter and its effects on the atrazine sorption on soils

The dissolved organic matter(DOM), water soluble organic matter derived from sewage sludge was separated into hydrophobic fraction(Ho) and hydrophilic fraction(Hi). The sorption of DOM and its fractions on soils and the effects of DOM sorption on a nonionic pesticide(atrazine(2-chloro-4-ethylamino-6-isopropylamino-1,3,5-trazine)) distribution between soil and water were investigated using a batch equilibrium technique. The total DOM sorption on soils described by the Langmuir equation reached saturation as the DOM concentration increased. The sorption of Ho fit the Freundlich model. In contrast, a negative retention evidently occurred as adding Hi at higher level in tested soils. The sorption of Ho dominated the total DOM sorption and the release of soil organic matter(SOM). Effects of DOM on the atrazine sorption by soils were DOM-concentration dependent and dominated by the interaction of atrazine, DOM, and soil solids. Generally, the presence of DOM with lower concentration promoted atrazine sorption on soils, namely the apparent partitioning constant(K*_d) for atrazine sorption in the presence of DOM was larger than the distribution constant(K_d) without DOM; whereas the presence of DOM with higher concentration inhibited atrazine sorption(i.e., K*_d<K_d). The overall effects of DOM on atrazine sorption in soils might be related to the DOM sorption and the release of soil intrinsic organic matter into aqueous solution. The sorption of Ho on soils promoted the atrazine sorption on soil, while the release of SOM by Hi and the competitive sorption between Hi and atrazine on soil surface led to a decrease of atrazine sorption. Information provided in this work may contribute to a better understanding of the DOM sorption and its impacts on the contaminant soil-water distribution.

Release behavior of copper and zinc from sandy soils

The concentrations and chemical forms of copper(Cu) and zinc(Zn) in surface soils directly influence the movement of Cu and Zn. In this study, thirteen sandy soil samples with a wide range of total Cu and Zn concentrations were collected for evaluating the relationships between Cu and Zn release and extraction time, ratio of soil to water, pH and electrolyte types. The results indicated that Cu released in batch extraction that represents long-term leaching was mainly from exchangeable, and carbonate bound Cu fractions, and Zn released in the batch extraction was mainly from its carbonate bound fraction. However, the Cu and Zn leached from the soils using the column leaching that represents short-term leaching were mainly from their exchangeable fractions. Soil column leaching at different pH values indicated that the amounts of leached Zn and Cu were greatly affected by pH. The Cu and Zn release experiments with varying extraction times and ratio of soil to water suggest that long-term water-logging in the soils after rain may increase contact time of the soils with water and the release of Cu and Zn to water from the soils, and total amounts of Cu or Zn released from the soils increase, but the Cu or Zn concentration in the surface runoff decrease with increasing rainfall intensity. The increased Ca concentration in soil solution increased stability of organic matter-mineral complexes and might decrease the dissolution of organic matter, and thus decreased the release of Cu-binding component of organic matter. However, high concentration of Na in the soil solution increased the dispersion of the organic matter-mineral complexes and increased dissolution of organic matter and the release of Cu from the soils.