No abstract

Open‐pit mining activities for metals and minerals have impacted vast areas of the Earth's surface and left behind highly disturbed and degraded landscapes. However, our understanding of tree species and recovery time on the restoration of biotic and abiotic soil properties remains incomplete. Topsoil (0–15 cm) was collected from plantations of 4 tree species: alder, acacia, pine, and cypress. A chronosequence of restoration was selected to assess the effect of recovery time: vegetation‐free postmining land (unrestored control), 5–10 years (young plantation), and 20–25 years (old plantation). The soil physicochemical characteristics and phospholipid fatty acids were analysed. After 20 years of restoration, the soil organic carbon (SOC) concentration increased, on average, from 1.4% to 4.7% for alder, cypress, and acacia. However, SOC was similar under pine plantations in unrestored control and at the late stage of restoration. The restoration of soil total nitrogen was faster than the SOC pools for all tree species investigated. Compared with that in the unrestored control, the total microbial biomass increased by 74% after 20–25 years of restoration. A similar increase was observed for bacterial biomass. The studied sites partly exhibited residues of trace elements that exceeded Chinese environmental quality standards (Cd, As, Cu, and Cr). However, only Cu affected the soil community; arbuscular mycorrhizal biomass decreased with an increase in Cu concentration. In conclusion, the recovery time, rather than the tree species, was the main determinant in the alteration of key soil physicochemical parameters in the restoration of phosphate‐mining‐degraded landscapes, at least during the first 20–25 years.

In regions with high livestock densities, the usage of antibiotics and metals for veterinary purposes or as growth promoters poses a risk in manured soils. We investigated to which degree the concentrations and depth distributions of Cu, Zn, Cr and As could be used as a tracer to discover contaminations with sulfonamides, tetracyclines and fluoroquinolones. Besides, we estimated the potential vertical translocation of antibiotics and compared the results to measured data. In the peri-urban region of Beijing, China, soil was sampled from agricultural fields and a dry riverbed contaminated by organic waste disposal. The antibiotic concentrations reached 110 μg kg(-1) sulfamethazine, 111 μg kg(-1) chlortetracycline and 62 μg kg(-1) enrofloxacin in the topsoil of agricultural fields. Intriguingly, total concentrations of Cu, Zn, Cr and As were smaller than 65, 130, 36 and 10 mg kg(-1) in surface soil, respectively, therewith fulfilling Chinese quality standards. Correlations between sulfamethazine concentrations and Cu or Zn suggest that in regions with high manure applications, one might use the frequently existing monitoring data for metals to identify potential pollution hotspots for antibiotics in topsoils. In the subsoils, we found sulfamethazine down to ≥2 m depth on agricultural sites and down to ≥4 m depth in the riverbed. As no translocation of metals was observed, subsoil antibiotic contamination could not be predicted from metal data. Nevertheless, sulfonamide stocks in the subsoil could be estimated with an accuracy of 35-200 % from fertilisation data and potential leaching rates. While this may not be sufficient for precise prediction of antibiotic exposure, it may very well be useful for the pre-identification of risk hotspots for subsequent in-depth assessment studies.

Background and aims Microbial community characterization is used as a disturbance indicator for soils.