Springer Science and Business Media LLC

In recent years, many previous studies have well documented that wild and cultivated edible mushrooms have the ability to bioaccumulate metal ions, but the process of mycoremediation and the detoxification strategy of mushrooms in co-contaminants (heavy metals and polycyclic aromatic hydrocarbons (PAHs)) are rarely reported. The study was to investigate the mycoremediation potential and tolerance responses of Oudemansiella radicata in cadmium and pyrene co-contaminated soil. Soil samples collected and sieved from Sichuan province, China, which was spiked with cadmium (0, 5, 15, and 30 mg/kg) and pyrene (0, 200, and 400 mg/kg). After harvest, biomass, bioaccumulation of cadmium, residual pyrene, and antioxidant enzymes activities were measured. Results showed that dry biomass was not apparently influenced by the co-contamination, even in highly polluted soils. In cadmium of 5 and 15 mg/kg, the bioaccumulation of cadmium enhanced when pyrene was added, the bioconcentration factor value even reached 1.09. The removal of pyrene (added at concentrations of 200 and 400 mg/kg) was significantly higher in O. radicata-planted soils than those in the unplanted soils and was inhibited in lower level of cadmium whereas promoted in higher level of cadmium, indicating that the highly adapted cadmium-resistant microbes could promote the dissipation of pyrene. Besides, antioxidant enzyme activities including superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) represented significantly changes in co-contamination as compared with control. Using O. radicata for remediation of cadmium-pyrene-contaminated soils could be an interesting alternative, considering its short life time, metal tolerance, and bioaccumulation capacity.

Collapsing gullies, which involve considerable erosion and extreme landform changes, frequently occur in the granite region of Southern China. Capturing the evolution of collapsing gullies is useful and effective for predicting erosion amount and landform changes. However, the evolution of collapsing gullies is too complex to simulate using conventional models. The aim of this study is to modify the traditional cellular automata (CA)-Markov model for simulating the evolution of collapsing gullies and then quantify their morphology using landscape pattern metrics. A hillslope eroded by collapsing gullies located in Longmen Town of the granite region of Southern China is used as a case study. Three digital elevation models (DEMs) were derived on 11 March 2017, 21 July 2017, and 2 December 2017 from a remotely piloted vehicle and global positioning system (GPS) real-time kinematics. Rainfall data for the corresponding time was recorded by a tipping-bucket rain gauge. Using these data, the CA-Markov model for simulating the evolution of collapsing gullies was developed, and then the most accurate one was chosen to predict the evolution on 2 December 2018. Evolution of the case study hillslope was interpreted and assessed using landscape metrics to capture the erosional trends of collapsing gullies. The area differences of the modified CA-Markov model are lower than those of the traditional model while the kappa coefficients of the modified CA-Markov model are higher than those of the traditional model; that is, the modified CA-Markov model performs better for simulating and predicting the evolution of collapsing gullies. The kappa coefficients also demonstrate that both scouring and gravity impact collapsing gullies, and scouring force is more effective than gravity. Based on the evolution prediction, the erosion amount of collapsing gullies in the subsequent year is predicted to be 904.1 m3. Spatial pattern analysis showed that the mid-lower part of a hillslope eroded by collapsing gullies will continue to be intensively eroded and the ground surface will become more fragmented. The use of a modified CA-Markov model and landscape pattern metrics provide an improved and effective method for understanding the spatial and temporal variations of collapsing gullies landform and ground surface, as well as better capturing the erosional trends of collapsing gullies.

The aim of this study was to quantify the release of the hydrophobic contaminant emamectin (EMA) from marine sediments in response to inputs of organic material (OM) and/or oil, in the presence or absence of two different bioturbating species. Specifically, it was designed to test whether oil would decrease the release of EMA and whether OM and/or the presence of bioturbating macrofauna would increase the release of EMA from sediment. Experimental sediments were spiked with EMA (5 μg kg−1 wet sediment). The different treatments were prepared by the addition of OM (310 g algae m−2) and/or an aliphatic oil (29.6 g oil m−2). In addition, two bioturbating species, Brissopsis lyrifera or Ennucula tenuis, were added in some aquaria, resulting in a total of 12 treatments with four replicates each. Water samples for analyses of silicate and EMA and sediment samples for analyses of total organic carbon (TOC) were taken at the start and end of the experimental exposure. In addition, oxygen was measured during the experimental period of 8 days. Fluxes were calculated and compared between treatments using generalised linear models (GLMs). The EMA release flux was significantly increased in treatments with added OM, possibly reflecting the presence of soluble complexes formed between EMA and dissolved OM. The presence of B. lyrifera caused a small, but statistically significant, increase in EMA release from sediment. This species would be expected to have a stronger effect on bioirrigation and particle mixing than E. tenuis, particularly when the population density of the latter species is low (as in the present experiment). There were no consistent effects of oil in this experiment, but the presence of oil decreased the EMA release flux when co-occurring with added OM and/or B. lyrifera. Increased retention of hydrophobic contaminants in the presence of oil is consistent with the existing literature on contaminant fate. The results from this study highlight the need to consider both the infauna present in polluted areas and the level of organic enrichment of the sediment when modelling the environmental fate of hydrophobic contaminants. It also highlights that labile OM and refractory oil appear to differ in their effects on the remobilisation of hydrophobic organic contaminants, by reducing and increasing release, respectively.

Land use conversion from rice paddy to upland has been shown to decrease soil pH due to enhanced proton production from nitrification of ammonium-based N fertilizers and base cation loss. Parent material and altitude have a dominant impact on spatiotemporal distribution of soil base cations, but little information is available about their effects on soil acidification. This study examined changes in acidity indicators after the conversion, and their relationship with parent materials and altitude in a typical hilly region of southern China. To explore the effects, soils derived from limestone, quaternary red clay, and sandshale were sampled from 11 sites in Qiyang and Qidong counties, Hunan Province, China. In each sampling site, paddy field as control and upland maize under different conversion ages were selected in adjacent and pairs. The information on management and conversion ages were surveyed from local farmers, and altitude was recorded for each site. Soil pH, exchangeable acidity, base cations, cation exchange capacity, soil organic matter, nutrients, and their inner relationships were examined. The conversion significantly decreased soil pH, which was parent material dependent. Soils derived from limestone had much higher pH than that from quaternary red clay and sandshale. Soil pH negatively correlated with altitude ranging from 96.2 to 138.3 m in the study area. The conversion significantly increased exchangeable acidity of soils derived from quaternary red clay and sandshale by 1.53 and 1.13 cmol(+) kg−1, respectively, dominated by Al, but no change for soils derived from limestone. The boosted regression tree model driven by soil properties explained 96.5%, 91.8%, and 98.1% of the pH variation of soils derived from limestone, quaternary red clay, and sandshale, respectively. Soil exchangeable Ca was the most influential trigger on pH variability of limestone- and quaternary red clay-derived soils, while soil total N and available N loss played critical roles in accelerating acidification of sandshale-derived soils after land use conversion. Our data indicated that Ca and N loss play critical roles in accelerating soil acidification from enhanced nitrification after land use conversion in the red soil hilly region, which could be influenced by parent materials and altitude. Practices such as liming, straw mulching, or catch crop should be taken to prevent Ca and N loss, and alleviate acidification as the conversion occurring, especially for soils at high altitude.