Soil Pollution Characteristics and Microbial Responses in a Vertical Profile with Long-Term Tannery Sludge Contamination in Hebei, China

Abstract

An investigation was made into the effects of tannery sludge on soil chemical properties and microbial communities in a typical soil profile with long-term tannery sludge contamination, North China. The results showed that trivalent chromium (Cr(III)), ammonium, organic nitrogen, salinity and sulfide were the predominant contaminants in tannery sludge. Although the tannery sludge contained high chromium (Cr, 3,0970 mg/kg), the proportion of mobile Cr forms (exchangeable plus carbonate-bound fraction) only accounted for 1.32%. The X-ray diffraction and X-ray photoelectron spectroscopy results further demonstrated that the Cr existed in a stable state of oxides and iron oxides. The alkaline loam soil had a significant retardation effect on the migration of salinity, ammonium, Cr(III) and sulfide, and the accumulation of these contaminants occurred in soils (0–40 cm). A good correlation (R2 = 0.959) was observed between total organic carbon (TOC) and Cr(III) in the soil profile, indicating that the dissolved organic matter from sludge leachate promoted the vertical mobility of Cr(III) via forming Cr(III)-organic complexes. The halotolerant bacteria (Halomonas and Tepidimicrobium) and organic degrading bacteria (Flavobacteriaceae, Tepidimicrobium and Balneola) became the dominant microflora in the soil profile. High contents of salinity, Cr and nitrogen were the main environmental factors affecting the abundance of indigenous microorganisms in soils.

Soil Characteristics and Microbial Responses in Post-Mine Reclamation Areas in a Typical Resource-Based City, China

“…And AN content is likely to be affected by soil moisture, temperature variation, and soil organism activities. Furthermore, AN content plays an important role in the evolution of reclaimed soil by affecting the nutrient cycling and microbial communities (Kong et al, 2019;Shrestha et al, 2009;Yuan et al, 2017).…”

Leaching Behaviors of Chromium(III) and Ammonium-Nitrogen from a Tannery Sludge in North China: Comparison of Batch and Column Investigations

“…The calculated average ratio of dissolved Fe/Cr(III) concentration was 3.56, which was rather close to the value 3.0 [ 32 ] and 3.33 [ 33 ] of Fe/Cr content in the precipitation pattern of Cr 0.25 Fe 0.75 (OH) 3 reported by the literature. Besides, the XRD, XRF, and XPS results have demonstrated the Cr(III) was immobilized as a stable Fe/Cr co-precipitation state in the tannery sludge in our previous study [ 14 ]. Thus, the small release amount of Cr(III) was mainly from the Cr 0.25 Fe 0.75 (OH) 3 dissolution in the tannery sludge, which was mainly influenced by the low pH and high temperature of leaching solution.…”

“…The alkaline tannery sludge has high contents of moisture and organic matter. Due to the simple pretreatment by ferric flocculant and precipitation with alkali before sludge dumping, the high content of Cr(III) (30,800 mg/kg) mainly existed in a stable state of Fe/Cr oxides in the tannery sludge, which was demonstrated by the X-ray diffraction (XRD), X-ray fluorescence (XRF) and X-ray photoelectron spectroscopy (XPS) results in our previous study [ 14 ]. The NH 4 + -N (16,080 mg/kg) and organic-nitrogen (16,500 mg/kg) were extremely high in the tannery sludge, which were generated during the tanning processes of NH 4 + -N deliming and protein catabolism [ 15 ].…”

“…Under the long-term action of indigenous nitrifying bacteria, NH 4 + -N is easily transformed in the soil to nitrate (NO 3 − -N) [ 13 ], causing the secondary contamination to deep soils and groundwater. New investigation of a typical soil profile with long-term tannery sludge contamination demonstrated that the characteristic contaminants were Cr(III) and NH 4 + -N in shallow soil [ 14 ]. Nevertheless, limited efforts have been directed towards the assessment of Cr(III) and NH 4 + -N release behaviors from the tannery sludge under different leaching conditions.…”

Assessing Chromium Contamination in Red Soil: Monitoring the Migration of Fractions and the Change of Related Microorganisms

“…The result indicated that soil properties were the key factors affecting the occurrence of Cr fractions in the red soil. Meanwhile, some studies have proved that different soil properties could significantly affect the occurrence of Cr fraction [28]. However, there was no significant difference (P > 0.05) in the contents of RES fraction with time and space distribution, and some researches showed that Cr in the RES fraction was not easily released in nature conditions, so the proportion of RES fraction heavy metals remained basically stable [41,44,45].…”