Spatial Distribution and Estimation Model of Soil pH in Coastal Eastern China.

Soil pH is an essential indicator for assessing soil quality and soil health. In this study, based on the Chinese farmland soil survey dataset and meteorological dataset, the spatial distribution characteristics of soil pH in coastal eastern China were analyzed using kriging interpolation. The relationships between hydrothermal conditions and soil pH were explored using regression analysis with mean annual precipitation (MAP), mean annual temperature (MAT), the ratio of precipitation to temperature (P/T), and the product of precipitation and temperature (P*T) as the main explanatory variables. Based on this, a model that can rapidly estimate soil pH was established. The results showed that: (a) The spatial heterogeneity of soil pH in coastal eastern China was obvious, with the values gradually decreasing from north to south, ranging from 4.5 to 8.5; (b) soil pH was significantly correlated with all explanatory variables at the 0.01 level. In general, MAP was the main factor affecting soil pH (r = -0.7244), followed by P/T (r = -0.6007). In the regions with MAP < 800 mm, soil pH was negatively correlated with MAP (r = -0.4631) and P/T (r = -0.7041), respectively, and positively correlated with MAT (r = 0.6093) and P*T (r = 0.3951), respectively. In the regions with MAP > 800 mm, soil pH was negatively correlated with MAP (r = -0.6651), MAT (r = -0.5047), P/T (r = -0.3268), and P*T (r = -0.5808), respectively. (c) The estimation model of soil pH was: y = 23.4572 - 6.3930 × lgMAP + 0.1312 × MAT. It has been verified to have a high accuracy (r = 0.7743, p < 0.01). The mean error, the mean absolute error, and the root mean square error were 0.0450, 0.5300, and 0.7193, respectively. It provides a new path for rapid estimation of the regional soil pH, which is important for improving the management of agricultural production and slowing down soil degradation.

Dynamic changes in the intestinal microbial community of two time-aged soils under combined cadmium and ciprofloxacin contaminated conditions.

The effects of combined contaminated soils containing cadmium (Cd) and ciprofloxacin (CIP) on the human gut microbiota are demonstrated using an in vitro test. Uncontaminated soil samples were artificially polluted with Cd and CIP using three different treatments (CK: 0 mg·kg-1; CIPI: 5 mg·kg-1, CIPII: 25 mg·kg-1, and Cd: 80 mg·kg-1). An experiment was performed to investigate the effect of Cd and CIP on the human colon microbiota using two aging times (D30: Day 30; D60: Day 60), and then the method of high-throughput 16S rRNA gene sequencing was used. In this study, we observed five phyla: Proteobacteria, Firmicutes, Synergistetes, Bacteroidetes, and Actinobacteria in colon microbial community. In addition, our results indicated that the relative abundances of the gut bacteria varied at the phylum level. Nevertheless, a slight decline in the relative abundance of Bacteroidetes among all the sets (compared to the D30-CK + Cd set) was revealed, and the lowest decline percentage of 90% was observed in the D60-CIPI + Cd set. Our results validated that the relative abundance of Rhodococcus increased with an increase in the CIP concentration in D30. In addition, this may disrupt normal physiological functions of the intestine after exposure to contaminated soil via the mouth. This study provides a theoretical basis for human risk assessment of oral exposure to Cd and CIP contaminated soils.