Investigating the Aging Effects of Biochar on Soil C and Si Dissolution and the Interactive Impact on Copper Immobilization

Aging tests were used to investigate the long-term effects of BC on the immobilization of Cu, and the soil silicon dissolution of three types soils (black soil, (BS), vegetable garden soil (VS) and red soil (RS)). Litchi branch biochars (BC) at 10% (w/w) were incubated with three Cu (400 mg/kg) contaminated soils. The effect on soil properties of pH, soil organic carbon (SOC), dissolved organic carbon (DOC) and available silicon content were investigated, along with the speciation distribution of Cu. The results indicated that SOC, DOC, and available silicon content (except, BC300) increased with the application of BCs. On the other hand, the DTPA (diethylenetriaminepentaacetic acid) extractable Cu content in BS, VS and RS soils were reduced by 4–12%, 18–25%, and 12–19%, respectively. The Cu availability in all soils first increased, and then decreased during the aging process. The sum of the other four fractions, including the carbonate fraction and the inert component increased by 4–4.5% (BS), 1.4–2.1% (VS), and 0.5–1% (RS) respectively, over the long-term process. Moreover, during the whole aging process, the soil properties (such as pH, SOC, DOC and available silicon content) were almost stable. This study demonstrates that BCs, especially those produced at a higher temperature, are superior to those been produced at 300 °C in immobilizing Cu and releasing available silicon in soils. However, the remediation efficiencies were restricted by the soil type contamination status and remediation time.

Determination of some heavy metals in vegetable garden soil and waste dumpsite soil in Mubi North, Adamawa State, Nigeria

A research conducted on soil samples using different depths were carried out on the determination of heavy metals (Pb, Cu, Zn, Ni, Cd and As) in Wuro-Gude vegetable garden soil and waste dumpsite soil, Mubi Metropolis Adamawa State, Nigeria. The soil samples were collected on different depths and were transported to the department of animal production laboratory for digestion. The mixtures were digested with tri-acid mixture (HNO3: HCO4: H2SO4) and determination of the heavy metals was done using a Buck Scientific 200A Model, Atomic Absorption Spectrophotometer (AAS). It was found that the heavy metals concentration in both types of soils at the depth of 5, 15 and 25cm was as follows: a) Vegetable garden soil: Ni – 7.33mg/g, 5.06mg/g and 3.04mg/g; Zn – 16.31mg/g, 13.08mg/g and 8.37mg/g; Cu – 6.94mg/g, 4.77mg/g and 3.28mg/g; Pb – 1.07mg/g, 0.57mg/g and 0.42mg/g and Cd – 0.35mg/g, 0.31mg/g and 0.29mg/g, respectively; As was not detected in all the depths; b) Waste dumpsite soil: Ni – 6.75mg/g, 4.33mg/g and 1.95mg/g; Zn – 14.67mg/g, 12.55mg/g and 9.04mg/g; Cu – 8.34mg/g, 5.72mg/g and 3.82mg/g; Pb – 2.15mg/g, 1.06mg/g and 0.67mg/g and Cd – 0.68mg/g, 0.57mg/g and 0.84mg/g, respectively; As was not detected in all the samples. All measured heavy metals concentrations were within the permissible limit set by the World Health Organization, except Cd which was above the permissible limit in waste dumpsite soil. Therefore, waste dumpsite soil should not be used for farming and effort should be made to educate the public on the health effect of these metals when ingested, to avoid bioaccumulation and biomagnification in the food chain.

Evaluation and Source Analysis on Heavy Metal Pollution of Vegetable Garden Soil in the Urban-Rural Area of Fushun City

Total of 40 soil samples were collected in vegetable garden soil in the urban-rural area of Fushun city. Heavy metal elements were evaluated including Cu, Zn, Pb, Cd , Cr, Ni, As and Hg. Soil environmental quality was evaluated by a combination of the single quality index method and the complex quality index method. Meantime, the soil potential ecological hazard was evaluated by Hakanson method. It will provide scientific basis for regional agricultural production, environmental protection and industry structural adjustment. The study showed that eight samples were contaminated by Ni, exceeding rate of 20.0%, and seven samples were contaminated by Cu, exceeding rate of 17.5%. In comprehensive study, light polluted accounted for 12.5%; warning and safety level accounted for 87.5%. At the same time, the order of the potential ecological risk of single-factor was Cd>Hg>Cu>Ni>As>Pb>Zn>Cr. Integrated potential ecological hazard was slight with the number of 25.48. Statistical analysis, correlation analysis and factor analysis all suggested that concentration of Cu, Ni, Zn and Hg were mainly affected by human activities, Pb, Cd, Cr and As were mainly controlled by parent rocks.