Determining soil quality in urban agricultural regions by soil enzyme-based index

Urban agricultural soils are highly variable, and careful selection of sensitive indicators is needed for the assessment of soil quality. This study is proposed to develop an index based on soil enzyme activities for assessing the quality of urban agricultural soils. Top soils were collected from urban agricultural areas of Korea, and soil chemical properties, texture, microbial fatty acids, and enzyme activities were determined. The soils belonged to five textural classes with the highest frequency of sandy loam. There was no clear correlation between the soil chemical properties and soil microbial properties. Principal component analysis (PCA) and factor analysis were applied to microbial groups for identification of microbial community variation in soils. Two soil groups, namely group 1 (G1) and group 2 (G2), based on microbial community abundance were examined by PCA, and those were more prominent in factor analysis. The G1 soils showed higher microbial community abundance than G2 soils. The canonical discriminant analysis was applied to the enzyme activities of sandy loam soil to develop an index, and the index validation was confirmed using the unused soils and published data. The high-quality soils in published literature assigned the high valued index. Microbial fatty acids and soil enzyme activities can be suitable indicators for soil quality evaluation of urban agricultural soils.

     

Quality assessment of various bottled waters marketed in Saudi Arabia

This study focuses on the chemical analysis of the available brands of domestic bottled water in Riyadh City, Saudi Arabia. The distribution of the chemical constituents (major, minor, and trace elements) is determined and compared with the chemical content labeled on the bottles and with drinking water standards of Saudi Arabian, World Health Organization, and U.S. Environmental Protection Agency. The obtained results indicated that except for fluoride and bromate, the concentrations of dissolved salts, soluble cations and anions, nitrate, and trace elements of most bottled waters on sale were within the permissible limits set by standards used. On the other hand, the comparison between determined and reported label values recorded a substantial variation in some parameter values. Results indicated that more than 18 % of the sampled bottled waters exceeded the allowable limits for drinking water. Generated Piper diagrams revealed that the majority of investigated waters were sodium chloride–sulfate type; however, the hydrochemical modeling indicated that all water samples were undersaturated for anhydrite, gypsum, and halite.     

Correction to: Determining soil quality in urban agricultural regions by soil enzyme-based index

Environmental Geochemistry and Health - Unfortunately, in the original publication of the article, Prof. Yang Sik Ok’s affiliation was incorrectly published. The author’s affiliation is...     

Engineered biochar composites with zeolite,silica, and nano-zerovalent iron for the efficient scavenging of chlortetracycline from aqueous solutions

Date palm waste–derived biochar (DBC) was produced through pyrolysis (600 °C) and modified with zeolite (Z-DBC), silica (S-DBC), or nano-zerovalent iron (nZVI-DBC) to design efficient sorbents. The pristine and engineered biochars were characterized by SEM, XRD, BET, TGA, CHNS-O, and FTIR to investigate the surface, structural, and mineralogical composition. The nZVI-DBC exhibited lowest pH (6.15) and highest surface area (220.92 m² g⁻¹), carbon (80.55%), nitrogen (3.78%), and hydrogen (11.09%) contents compared with other biochars. Isotherm sorption data for chlortetracycline (CTC) removal from aqueous solutions was described well by Langmuir and Redlich–Peterson isotherms showing the highest fitness (R² values in the range of 0.88–0.98 and 0.88–0.99, respectively). Langmuir predicted maximum CTC adsorption capacity was in order of nZVI-DBC (89.05 mg g⁻¹) > S-DBC (45.57 mg g⁻¹) > Z-DBC (30.42 mg g⁻¹) > DBC (28.19 mg g⁻¹). Kinetics adsorption data was best described by power function model (R² = 0.93–0.99), followed by interaparticle diffusion (R² = 0.85–0.96) model. The nZVI-DBC performed outclass by removing 98% of CTC, followed by S-DBC (68%), Z-DBC (35%), and DBC (36%). Chemisorption, H-bonding, and interaparticle diffusion were the operating mechanisms for CTC adsorption onto DBC, S-DBC, and Z-DBC, while π-π electron donor–accepter interactions and redox reactions augmented these mechanisms for highest CTC adsorption onto nZVI-DBC. Therefore, nZVI-DBC may serve as an efficient green technology for the removal of CTC from aqueous solutions and to reduce surface date palm waste pollution.

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Solution chemistry influence on metal mobility in biosolids-amended soils

Many studies have implicated dissolved organic carbon (DOC) as an important contributor to the elevated mobility of trace metals in soils amended with biosolids. Few of these studies, however, have quantified both DOC and metal concentrations. We completed laboratory leaching column studies on a dryland Platner loam (fine, smectitic, mesic Aridic Paleustoll) and an irrigated Osgood sand (loamy, mixed, mesic Arenic Ustollic Haplargid), both with a history of biosolids application. The soils were neutral to slightly alkaline in pH prior to amendment. We performed an additional application of biosolids to one set of columns in the laboratory at a rate of 28 Mg ha(-1) to investigate the effect of time following application on metal mobility. The effect of electrolyte concentration was studied by using both distilled water and simulated irrigation water. Biosolids application increased both DOC and Cu in the column effluents resulting in a positive correlation between Cu and DOC across application treatments for both soils. Both Cu and Pb were mobilized under conditions of low electrical conductivity (EC). This may be the result of the release of a strong metal-binding component of DOC under these conditions. Conversely, Zn mobility was positively correlated with EC, suggesting that either cation exchange or the formation of inorganic complexes influences Zn mobility. Anodic stripping voltammetry measurements indicated that only a small percentage of the total dissolved metals existed as free ions or inorganic complexes; the remainder appears to be complexed to DOC.