Lirong Cheng

Review on utilization of biochar for metal-contaminated soil and sediment remediation

Biochar is a carbon-neutral or even carbon-negative material produced through thermal decomposition of plant- and animal-based biomass under oxygen-limited conditions. Recently, there has been an increasing interest in the application of biochar as an adsorbent, soil ameliorant and climate mitigation approach in many types of applications. Metal-contaminated soil remediation using biochar has been intensively investigated in small-scale and pilot-scale trials with obtained beneficial results and multifaceted effects. But so far, the study and application of biochar in contaminated sediment management has been very limited, and this is also a worldwide problem. Nonetheless, there is reason to believe that the same multiple benefits can also be realized with these sediments due to similar mechanisms for stabilizing contaminants. This paper provides a review on current biochar properties and its use as a sorbent/amendment for metal-contaminated soil/sediment remediation and its effect on plant growth, fauna habits as well as microorganism communities. In addition, the use of biochar as a potential strategy for contaminated sediment management is also discussed, especially as regards in-situ planning. Finally, we highlight the possibility of biochar application as an effective amendment and propose further research directions to ensure the safe and sustainable use of biochar as an amendment for remediation of contaminated soil and sediment.

A screen-printed, amperometric biosensor for the determination of organophosphorus pesticides in water samples

An amperometric biosensor based on screen-printed electrodes (SPEs) was developed for the determination of organophosphorus pesticides in water samples. The extent of acetylcholinesterase (AChE) deactivation was determined and quantified for pesticide concentrations in water samples. An enzyme immobilization adsorption procedure and polyacrylamide gel matrix polymerization were used for fabrication of the biosensor, with minimal losses in enzyme activity. The optimal conditions for enzyme catalytic reaction on the SPEs surfaces were acetylthiocholine chloride (ATChCl) concentration of 5 mmol/L, pH 7 and reaction time of 4 min. The detection limits for three organophosphorus pesticides (dichlorvos, monocrotophs and parathion) were in the range of 4 to 7 microg/L when an AChE amount of 0.1 U was used for immobilization.

Characterizing Microbial Activity and Diversity of Hydrocarbon-Contaminated Sites

Hydrocarbons, one of the major petroleum constituents, mainly include saturated alkanes and cycloalkanes, unsaturated alkenes, alkynes and aromatic hydrocarbons. The usual composition of light crude oil is 78% saturates, 18% aromatics, 4% resins and <2% asphaltenes (Olah and Molnar 2003). The hydrocarbon fractions in the order of decreasing volatility are C6C10; C10 – C16; C16 C34 and C34 C50, in which Cx is referred to the number of carbon molecules in the alkane backbone.

The performance of a sulfate-radical mediated advanced oxidation process in the degradation of organic matter from secondary effluents

The effects of sulfate radical-mediated advanced oxidation processes with transition metal and energy activation methods were investigated during effluent organic matter (EfOM) degradation. The results showed that transition metal systems and energy systems performed well with some outstanding EfOM removal efficiencies. Specifically, the EfOM removal rate with the Ag(I)/PS (persulfate) system reached 90%, which was far greater than those of Co(II)/PMS (peroxymonosulfate) (56%) and ZVI (zero valence iron)/PS (58%), respectively. Regarding the energy activation systems, they all exhibited both better combined efficiency and the highest efficiency at strong energy intensity (such as heating at 80 °C or treating with UV at 40 W). Further analysis by UV-visible spectroscopy during the reaction process provided a better understanding of the overall changes in every system.

Biodegradation of Indeno (1,2,3-cd) Pyrene by a Pure Bacterial Culture of Pandoraea sp.

Three new isolated bacterial cultures of Pandoraea sp., Stenotrophomonas sp., and T Pseudoxanthomonas mexicana that could efficiently degraded Indeno (1,2,3-cd) pyrene (Inp) were reported in this paper. The biodegradation performance of Inp by Pandoraea sp was studied under different pH conditions. Under the conditions of pH=8, the removal efficiency of Inp fluctuated sharply among 8% and 40%. The optimal condition for InP removal was pH=7, and removal efficiency was nearly 60% after the incubation of 25days.

Optimal Conditions for Biodegradation of Indeno (1,2,3-cd) Pyrene in Soil Slurry Reactors

Soil slurry reactor technology is one of the effective methods for treating PAHs contaminated soil. In this paper, removal of high molecular weight PAHs, Indeno (1,2,3-cd) pyrene (Inp), was studied in soil slurry reactors with isolated bacteria from PAHs contaminated soil. The factors affecting Inp biodegradation and the optimal conditions were investigated using orthogonal experimental design (L9(34)). The highest degradation efficiency of Inp was 50.71% after the incubation of 12 days. The most significant influencing factors were aeration rate, water to soil ratio and salinity, while pH was less significant. The optimal conditions for Inp degradation in soil slurry reactor was: aeration rate 120L/h, water to soil ratio 2:1, salinity 10%, pH=6.

Quick Assessment of Contamination Threat to Groundwater after NAPL Spill

Environmental accidents occur frequently in China in recent years. A quick estimation of the extent and distribution of contamination after environmental accidents is important for immediate treatment of the contaminated sites. This paper proposed a methodology to estimate the velocity and maximum infiltration depth of NAPL after spill accidents to provide quick and quantitative information for the emergency treatment of the site. The proposed methodology uses only the basic information of the accident: contaminant type and its properties, groundwater level, soil type and average properties, and estimated infiltration area. By comparing the maximum infiltration depth of NAPL with the depth to groundwater, one can identify whether there is an immediate threat to groundwater. If there is such a danger, proper measures should be taken within the suggested time frame to prevent NAPL from entering the saturated zone.

MTBE Attenuation in a Chalk Aquifer

A conceptual model of MTBE attenuation in a chalk aquifer was built and validated by both field observations and modeling following the accidental spill of storage tanks at a petrol station in southern England. It was shown: (1) Dual porosity transport plays an important role in MTBE attenuation in the chalk aquifer; (2) MTBE concentration measured in monitoring wells may depend more on dual porosity transport effects than degradation; (3) For this dual porosity aquifer (the Chalk) with its large portion of immobile water, a single porosity model is not able to predict the plume evolution. The dual porosity model was able to accurately produce the quick response of fracture transport and the measured concentration level at different distances and depths; (4) Examination of MTBE fate with lab measured MTBE degradation rates showed that MTBE is unlikely to degrade within the Chalk matrix. MTBE may be degraded in fractures with a maximum degradation rate (kMTBE-O2) of not more than 3.62E-12 mol/L/s; (5) Physical processes such as advection, dispersion, diffusion and dual porosity mass transfer are more important than degradation in controlling plume development in this system.

Microcosm Study on Response of Soil Microorganisms to Polycyclic Aromatic Hydrocarbons Contamination

Soil and groundwater contamination by petroleum and coal tar becomes one of the urgent environmental issues concerned by more and more scientists with regards to the public health. With the induction of organic contaminants to soil and groundwater it will change the environmental conditions within the plume and hence lead to the variation of indigenous microorganisms. The article aims to investigate the response of indigenous microorganisms to the petroleum contamination. Three polycyclic aromatic hydrocarbons (PAHs) phenanthrene, anthracene and pyrene were selected as the contaminants and tested using laboratory microcosm. The response of indigenous microorganisms to the PAHs induction was analyzed by measuring the change of soil microbial activity, soil catalase activity, contaminants concentration and geochemical parameters. The experimental results showed that: (1) the major parts of the PAHs were absorbed by the soil, its transport was retarded, (2) the soil microbial activity was inhibited at the initial stage of PAHs induction and then slowly increased, (3) the soil catalase activity was stimulated at first with PAHs induction and then inhibited within the range -0.05 mL (0.1 M KMnO 4 )/g (soil).