Effective alleviation of Cd stress to microbial communities in mining reclamation soils by thiourea-modified biochar amendment

Reclaimed soils in mining area usually display low fertility and present Cd stress. The amendment of modified biochar effectively fixes Cd in soils,enhances soil fertility, and reduces Cd stress in soil microorganisms. However, the effect of thiourea-modified biochar(TBC) on microbial adaptability to Cd stress in mining reclamation soils is still unclear. The present work studied the Cd immobilization and microbial community changes in a mining reclamation soil displaying extreme Cd contaminatio...     

Distribution and provenance implication of rare earth elements and Sr-Nd isotopes in surface sediments of Jiulong River,Southeast China

Purpose

The purposes of this paper are to investigate the geochemical characteristics of rare earth elements (REEs) in the surface sediments of Jiulong River, southeast China, to probe the provenance compositions of the sediments, and to analyze the potential anthropogenic influence on REEs in the sediments. REEs and Sr-Nd isotopes were selected as the tools because REEs can be used to identify the anthropogenic effects on sediments and Sr-Nd isotopes have been widely known as powerful tracers for provenance analysis.

Materials and methods

Fifty-three samples of surface sediments (0~5 cm) were collected from Jiulong River. The concentrations of REEs and Sr-Nd isotopic compositions in the surface sediments were determined by inductively coupled plasma mass spectrometry (ICP-MS) and thermal ionization mass spectrometry (TIMS), respectively. The chondrite-normalized and WRAS-normalized REEs patterns, enrichment factor, plots of La-Th-Sc and La/Yb-∑REE, and plots of ε_Nd(0) vs ⁸⁷Sr/⁸⁶Sr and ε_Nd(0) vs δEu are presented.

Results and discussion

The mean concentration of ΣREEs in the surface sediments of Jiulong River was 254.25 mg kg^?1. The mean values of ΣLREEs (227.6 mg kg^?1), ΣHREEs (26.64 mg kg^?1), and (La/Yb)_N ratios (9.24) suggested an enrichment of LREEs compared to HREEs. Negative Eu anomalies were observed in the surface sediments. The distribution patterns of REEs in the surface sediments from different areas of Jiulong River were remarkably similar. The values of ⁸⁷Sr/⁸⁶Sr, ¹⁴³Nd/¹⁴⁴Nd, and ε_Nd(0) were 0.714091~0.733476, 0.511875~0.512271, and ??14.88~??7.16, respectively. The plots of ε_Nd(0) vs ⁸⁷Sr/⁸⁶Sr, ε_Nd(0) vs 1/[Nd], and ε_Nd(0) vs δEu indicated that the sediments in Jiulong River were mainly derived from natural geological processes and the REEs might be also influenced by anthropogenic activities such as Fujian Pb-Zn deposit, coal ash, and industrial sludge.

Conclusions

The REEs in the surface sediments at different sites are similar in geochemical characteristics, with a right-inclined distribution pattern and higher enrichment of light REEs (LREEs) compared to heavy REEs (HREEs), and a negative Eu anomaly but no evidence of Ce anomaly. The sediments in Jiulong River were mainly derived from natural geological processes (granite and magmatic rocks), and the REEs in the sediments were also influenced by anthropogenic activities (Fujian Pb-Zn deposit, coal ash, and industrial sludge).