Shaoliang Zhang

Efficient remediation of PAH-metal co-contaminated soil using microbial-plant combination: A greenhouse study

A 2-year greenhouse study was conducted to remediate an actual wastewater-irrigated soil co-contaminated with polycyclic aromatic hydrocarbons (PAHs) and heavy metals (Cd and Zn). The remediation methods included microbial remediation, phytoremediation, and microbe-assisted phytoremediation. The maximum PAH removal (96.4%), PAH mineralization, and metal phytoextraction (36.1% Cd and 12.7% Zn) were obtained by interplanting ryegrass with Seduce alfredii with regular re-inoculation with Microbacterium sp. KL5 and Candida tropicalis C10 in the co-contaminated soil. The plants shoots were harvested at a 4-month interval. After 2 years, the concentrations of 16 individual PAHs were reduced to below the limit of Chinese soil quality standard for agricultural use (grade II, pH 6.5-7.5), and the metal concentrations in ryegrass shoots were below the Chinese national limit for animal feeds (GB13078-2001). The exogenous microbes gradually disappeared with time, and thus a 2-month re-inoculation interval was applied for a purpose to maintain high cell density and activity of the inoculants. KL5 introduction increased soil enzyme activity, plant growth, PAH removal and metal phytoextraction, while C10 promoted soil enzyme activity and removal of high-molecular-weight PAHs. Interplanting with S. alfredii reduced metal concentrations in ryegrass tissues. Ryegrass showed stronger rhizosphere effects than S. alfredii did.

Spatial Variability of PAHs and Microbial Community Structure in Surrounding Surficial Soil of Coal-Fired Power Plants in Xuzhou, China

This work investigated the spatial profile and source analysis of polycyclic aromatic hydrocarbons (PAHs) in soil that surrounds coal-fired power plants in Xuzhou, China. High-throughput sequencing was employed to investigate the composition and structure of soil bacterial communities. The total concentration of 15 PAHs in the surface soils ranged from 164.87 to 3494.81 μg/kg dry weight. The spatial profile of PAHs was site-specific with a concentration of 1400.09–3494.81 μg/kg in Yaozhuang. Based on the qualitative and principal component analysis results, coal burning and vehicle emission were found to be the main sources of PAHs in the surface soils. The phylogenetic analysis revealed differences in bacterial community compositions among different sampling sites. Proteobacteria was the most abundant phylum, while Acidobacteria was the second most abundant. The orders of Campylobacterales, Desulfobacterales and Hydrogenophilales had the most significant differences in relative abundance among the sampling sites. The redundancy analysis revealed that the differences in bacterial communities could be explained by the organic matter content. They could also be explicated by the acenaphthene concentration with longer arrows. Furthermore, OTUs of Proteobacteria phylum plotted around particular samples were confirmed to have a different composition of Proteobacteria phylum among the sample sites. Evaluating the relationship between soil PAHs concentration and bacterial community composition may provide useful information for the remediation of PAH contaminated sites.

Incorporating ecological vulnerability assessment into rehabilitation planning for a post-mining area

A practical issue is present in sustaining and rehabilitating the ecologically vulnerable post-mining area in which the environmental condition varies spatially and therefore influenced by multiple factors. This paper attempts to integrate the ecological vulnerability assessment and rehabilitation treatment to assist land managers in revealing vulnerable features along with developing treatments of vulnerability mitigation. Using a post-mining site in a mountainous area in western China as study area, an indicator system and framework for assessing and reducing vulnerability were developed based on a vulnerability analysis. Geo-informatics, such as satellite image processing and spatial analysis, were employed to perform the assessment and planning. It was found that higher exposure and sensitivity are the main causes of increased vulnerability in a seriously disturbed post-mining area. Rehabilitation treatments were arranged spatially and structurally based on the framework of vulnerability mitigation. A pre-evaluation of the effectiveness shows this type of rehabilitation has a convergence effect that clusters and lowers the ecological vulnerability index (EVI). The average value of EVI will be reduced by 15.02% if the minimum standards of rehabilitation can be completed. Altogether, an integration of rehabilitation treatments and the quantification of vulnerability in a spatially explicit manner are critical for planners to gain more insight into ecological vulnerability in post-mining area, which provides guidance to simplify rehabilitation planning with respect to vulnerability mitigation.

Short-term effects of CO2 leakage on the soil bacterial community in a simulated gas leakage scenario

The technology of carbon dioxide (CO2) capture and storage (CCS) has provided a new option for mitigating global anthropogenic emissions with unique advantages. However, the potential risk of gas leakage from CO2 sequestration and utilization processes has attracted considerable attention. Moreover, leakage might threaten soil ecosystems and thus cannot be ignored. In this study, a simulation experiment of leakage from CO2 geological storage was designed to investigate the short-term effects of different CO2 leakage concentration (from 400 g m−2 day−1 to 2,000 g m−2 day−1) on soil bacterial communities. A shunt device and adjustable flow meter were used to control the amount of CO2 injected into the soil. Comparisons were made between soil physicochemical properties, soil enzyme activities, and microbial community diversity before and after injecting different CO2 concentrations. Increasing CO2 concentration decreased the soil pH, and the largest variation ranged from 8.15 to 7.29 (p < 0.05). Nitrate nitrogen content varied from 1.01 to 4.03 mg/Kg, while Olsen-phosphorus and total phosphorus demonstrated less regular downtrends. The fluorescein diacetate (FDA) hydrolytic enzyme activity was inhibited by the increasing CO2 flux, with the average content varying from 22.69 to 11.25 mg/(Kg h) (p < 0.05). However, the increasing activity amplitude of the polyphenol oxidase enzyme approached 230%, while the urease activity presented a similar rising trend. Alpha diversity results showed that the Shannon index decreased from 7.66 ± 0.13 to 5.23 ± 0.35 as the soil CO2 concentration increased. The dominant phylum in the soil samples was Proteobacteria, whose proportion rose rapidly from 28.85% to 67.93%. In addition, the proportion of Acidobacteria decreased from 19.64% to 9.29% (p < 0.01). Moreover, the abundances of genera Methylophilus, Methylobacillus, and Methylovorus increased, while GP4, GP6 and GP7 decreased. Canonical correlation analysis results suggested that there was a correlation between the abundance variation of Proteobacteria, Acidobacteria, and the increasing nitrate nitrogen, urease and polyphenol oxidase enzyme activities, as well as the decreasing FDA hydrolytic enzyme activity, Olsen-phosphorus and total phosphorus contents. These results might be useful for evaluating the risk of potential CO2 leakages on soil ecosystems.

A GIS-Based Web Approach for Serving Land Price Information

Participants in the land market are usually hampered to browse and analyze the land price information due to the lack of information sources and available analysis tools. A service-oriented GIS-based web system was developed to provide a practical solution, its essential data sources contain basic geographic elements and benchmark land price (BLP)-related information. Core models for land price analysis were implemented, including land price index, spatial distribution, and parcel appraisal. The system was developed based on a four-level Browse Server (B/S) architecture using GIS and web service technologies, which enables the publishing, browsing, and analysis of the land price information via the Internet. With effective functionalities, the system has been employed in a project for updating BLP in a case study city located in China. The main advantage of the GIS-based web approach lies in its integration of spatial-temporal analysis models and web GIS technology, which allows more investors and administrators with limited domain knowledge to obtain further understanding on the change pattern and spatial distribution of land price by an online means. The experience in the case study city demonstrates that the approach has strong practicality for land price information services.

Influence of CO2 leakage from oil-producing wells on crop growth based on improved CASA model

ABSTRACT As a significant application of CO2 geological storage technology, CO2-enhanced oil recovery (CO2-EOR) considers impacts on ecosystems due to the risk of CO2 leakage from oil-producing wells. It is critical to clarify the relationship between CO2 leakage and vegetation growth, because large numbers of wells are situated in the midst of cropland. In this study, we calculated the net primary productivity (NPP) of crops to examine the correlation between oil-producing wells and crop growth using Pleiades’ high-spatial resolution remote-sensing imaging in a CO2-EOR experimental area in Shandong Province, China, basing our methods on the improved Carnegie–Ames–Stanford approach (CASA) model. Atmospheric CO2 concentrations at varying distances from one of the producing wells were collected by wireless sensors and hand-held equipment, and analysis was conducted in regard to the impact of CO2 leakage from producing wells on crop growth according to a simple sampling method. The results indicated that increased CO2 concentration resulting from leakage from producing wells has a slightly positive influence on crop productivity, with the influence ranges correlated with wind direction and velocity. The variance of NPP resulting from increased CO2 concentration and wind direction ranged from 5.0 to 33.7%.

Effects of Pb Smelting on the Soil Bacterial Community near a Secondary Lead Plant

Secondary lead smelting is a widespread industrial activity which has exacerbated Pb or Cd contamination of soil and water across the world. Soil physicochemical properties, soil enzyme activities, heavy metal concentrations, and bacterial diversity near a secondary lead plant in Xuzhou, China were examined in this study. The results showed that secondary lead smelting activities influenced nearby soils. Soil acidification decreased one order of magnitude, with a mean value of 7.3. Soil organic matter also showed a downward trend, while potassium and nitrogen appeared to accumulate. Soil urease and protease activity increased in samples with greater heavy metal pollution, but overall the soil microbial biodiversity decreased. Soil heavy metal concentration—especially Pb and Cd—greatly exceeded the concentrations of Chinese Environmental Quality Standard for Soils (GB 15618-1995). Some environmental factors—such as pH, organic matter, enzyme activity, and the concentration of heavy metals—significantly affected bacterial diversity: compared with the control site, the Chao1 estimator decreased about 50%, while the Shannon diversity index dropped approximately 20%. Moreover, some genera have significant relationships with heavy metal concentration—such as Ramlibacter with Zn and Steroidobacter with Cd—which might act as bio-indicators for soil remediation. These results will provide a new insight in the future for reclaiming soil contaminants caused by secondary lead smelting.

Regime shift and redevelopment of a mining area’s socio-ecological system under resilience thinking: a case study in Shanxi Province, China

Theory related to resilience thinking proposes that complex systems evolve in nested adaptive cycles. However, concrete examples are needed to instantiate this proposition and show what merit it might have in practice. This empirical study used a mesoscale landscape that has experienced mining activity and has faced challenges related to environmental protection and sustainable development. Adopting the perspective of resilience thinking, this study investigated the historical dynamics of a post-mining area in Shanxi Province and considered its future development. In the studied area, the main income source was found to have shifted from agriculture to coal mining activity between 1983 and 2010, with more than 41% of the land being used for mining operations. Such activity degraded the net primary productivity of the local ecosystem. The socio-ecological system experienced two states: traditional agriculture and mining. The evolution of the past adaptive cycles was mainly driven by coal exploitation and environmental degradation within the mining area, as well as the cross-scale interactions of economic events and coal policy changes outside the mining area. As a result of exhausted coal resources and small-scale mining closures, the socio-ecological system is currently in a poverty trap. Based on an assessment of the socio-ecological system’s strengths, weaknesses, opportunities, and threats, a new eco-agriculture can be considered an option for future transformation. The post-mining landscape is apparently a coupled socio-ecological system characterized by panarchy and temporal dynamics. Internal resources and cross-scale interactions, such as the regional-scale demand for agricultural products, could help reorganize the stagnant system. This case study shows that a mesoscale landscape can be a sally port for the application and operation of resilience-thinking-related theory, such as panarchy. This concrete example manifests the proposition that complex systems undergo cycles of renewal and collapse and can be nested in adaptive cycles. The merit of this proposition is not just that it helps to establish a theoretical understanding of the dynamics of complex systems; more importantly, it also generates practical measures to manage such dynamics. This case study supports the existence and importance of regional resilience in maintaining or restoring local economies. On these grounds, we propose that resilience thinking can act as a mental model and practical tool for understanding the historical dynamics of stagnant systems, such as legacy mining sites, and navigate their transitions.

Understanding the High Sensitivity of Parallel WO3 Sensor Toward NO2 Gas at Low Temperature

Tungsten trioxide (WO3-x) with different morphologies was synthesized by hydrothermal method. Using a pair of Pt electrodes and Al2O3 ceramics tube as a substrate, NO2 sensing properties of the WO3 products were measured at different working temperatures. And the high sensing properties at low working temperature were also investigated. The results showed that the sensitivity of WO3 product is strongly dependent on morphology and structure. The parallel circuit mode also plays an important role in the NO2 sensing characteristics. The low working temperature can be attributed to the competitive reaction between O2 and NO2 gas. The parallel mode may increase the lifetime of sensor.

Advanced treatment of copper smelting wastewater by the combination of internal micro-electrolysis and electrocoagulation

ABSTRACT In this study, a combined process of internal micro-electrolysis (IME)–electrocoagulation was developed at lab scale for treating a real copper smelting wastewater. By IME, 92.4% of Cu, 88.6% of Pb, and 72.2% of Zn were removed after 30 min at an initial solution pH of 3, a Fe/C dosage of 40 g/L, and a Fe/C mass ratio of 1:1. Removal of residual metals by electrocoagulation was affected by wastewater pH and current density. Electrocoagulation with iron/aluminum electrodes at a current density of 5 mA/cm2, electrocoagulation time of 30 min, and pH 8 resulted in 99.3% Cu, 99.5% Pb, and 98.6% Zn removal. The final effluent quality could satisfy the National Discharge Standard of China. This work demonstrates that the hybrid system has the potential to be applied for the advanced treatment of high-strength copper smelting wastewater.