In this study, electrokinetic remediation (EKR) was carried out to remove arsenic (As) from soil washing residue. We screened various processing fluids and found that oxalic acid was most effective for As removal because it reductively dissolved Fe and As from the soil. In EKR, however, NaOH was a more effective agent for removing As, implying that the main removal mechanism of As was ion exchange between OH– and oxyanionic As. Oxalic and citric acid, both of which were efficient agents for removing As in the screening tests, did not effectively remove As by EKR, probably due to the relatively high pH and low soil-to-agent ratio. In EKR, As was mainly removed by electromigration toward the anode, even under high amounts of accumulated electro-osmotic flow. Therefore, strategies that increase electromigration have potential for enhancing As removal.

From April 2008 to November 2009, a field decomposition experiment was conducted to investigate the effects of sediment burial on macro (C, N) and microelement (Pb, Cr, Cu, Zn, Ni, and Mn) variations in decomposing litter of Phragmites australis in the coastal marsh of the Yellow River estuary. Three one-off sediment burial treatments [no sediment burial (0 mm year⁻¹, S₀), current sediment burial (100 mm year⁻¹, S₁₀), and strong sediment burial (200 mm year⁻¹, S₂₀)] were laid in different decomposition sites. Results showed that sediment burials showed significant influence on the decomposition rate of P. australis, in the order of S₁₀ (0.001990 day⁻¹) ≈ S₂₀ (0.001710 day⁻¹) > S₀ (0.000768 day⁻¹) (p < 0.05). The macro and microelement in decomposing litters of the three burial depths exhibited different temporal variations except for Cu, Zn, and Ni. No significant differences in C, N, Pb, Cr, Zn, and Mn concentrations were observed among the three burial treatments except for Cu and Ni (p > 0.05). With increasing burial depth, N, Cr, Cu, Ni, and Mn concentrations generally increased, while C, Pb, and Zn concentrations varied insignificantly. Sediment burial was favorable for C and N release from P. australis, and, with increasing burial depth, the C release from litter significantly increased, and the N in litter shifted from accumulation to release. With a few exceptions, Pb, Cr, Zn, and Mn stocks in P. australis in the three treatments evidenced the export of metals from litter to environment, and, with increasing burial depth, the export amounts increased greatly. Stocks of Cu and Ni in P. australis in the S₁₀ and S₂₀ treatments were generally positive, evidencing incorporation of the two metals in most sampling times. Except for Ni, the variations of C, N, Pb, Cr, Cu, Zn, and Mn stocks in P. australis in the S₁₀ and S₂₀ treatments were approximated, indicating that the strong burial episodes (S₂₀) occurred in P. australis marsh in the future would have little influence on the stocks of these elements. With increasing burial depths, the P. australis was particularly efficient in binding Cu and Ni and releasing C, N, Pb, Cr, Zn, and Mn, implying that the potential eco-toxic risk of Pb, Cr, Zn, and Mn exposure might be very serious. This study emphasized the effects of different burials on nutrient and metal cycling and mass balance in the P. australis marsh of the Yellow River estuary.

Phytotoxic effects of a single heavy metal on different crops are widely reported; however, consequences of combined metal toxicity on maize are rarely investigated. In this study, a pot experiment was conducted to assess the phytotoxic effects both Al and Cr on morphophysiological and biochemical traits, photosynthetic gas exchange capacities, metal uptake, and translocation in different plant parts. Plants were exposed to Al³⁺ (100 μM), Cr⁶⁺ (100 μM), and Al³⁺ + Cr⁶⁺ (100 + 100 μM), and data were collected at pre- and post-silking stages while uncontaminated pots were served as control (Ck). Results depicted that both Al and Cr impaired maize growth and yield response and inhibited photosynthesis and gas exchange attributes i.e., transpiration, stomatal conductance, inter-cellular CO₂, as well as water use efficiency (WUE) and intrinsic water use efficiency (WUEi). Moreover, Al and Cr toxicities caused lipid peroxidation and membrane damage while activated antioxidative defense system in terms of superoxide dismutase (SOD), peroxidaes (POD), and catalase (CAT) and mediated reduced glutathione contents (GSH). Increased proline and reduced protein contents were also observed with a combined metal toxicity. Interestingly, Cr proved to be more toxic than Al whereas affects were more apparent where both Al and Cr were applied simultaneously. Plant exposure to both Al and Cr increased metal contents in different plant parts, while maximum metal contents were recorded in roots followed by stem, leaves, corn ear, and grains. Overall severity in phytotoxic effects was observed as Al+Cr > Cr > Al > Ck. Additionally, values of combined application of both Al + Cr were higher than those of the linear sum of Al and Cr alone, suggesting that synergistic effects of Al + Cr were more toxic than their individual effects. Hence, combined metal toxicity proved more damaging for maize than individual metal stress.

A high-dimensional driving function for Microcystis bloom warning was developed, in which both the inhibition and promotion impacts on Microcystis growth activation energy are integrally considered. Five factors, including flow disturbance, temperature, light intensity, nutrient concentration, and biological inhibition, are embedded in the equation, which results in a high-dimensional problem. The projection pursuit principle was applied for dimension reduction to resolve the numerical problem, and an integrated hydro-environmental model was established. Jinshan Lake, a typical riverside lake, was selected as the research area, and six bloom grades were determined for warning analysis. Based on the established model, the processes of Microcystis growth under varied hydrodynamic conditions were simulated. It was found that the established warning model could well reveal the Microcystis bloom processes in Jinshan Lake. The low-water year was characterized by the largest number of days on which Microcystis bloom might occur for its poor water exchange frequency; The areas where Microcystis bloom might occur in the flood seasons of high-water year, common-water year, and low-water year varied with the uneven-distributed dynamic conditions, which were respectively 0.15, 0.91, and 1.26 km².

The cell density-dependent gene expression in gram-negative bacteria is through the activity of acyl homoserine lactone signal molecules. The novel strain Pseudomonas putida JMQS1 isolated from detergent-contaminated soil exhibited quorum sensing along with its ability to degrade phenol. The response to Chromobacterium violaceum DSTS-1 mutant biosensor and luxI and luxR gene-specific amplification was used to characterize the quorum sensing property of the isolate. A regulation in the synthesis of various acyl homoserine lactone molecules, viz C₆HSL in the initial stages of phenol stress, C₈HSL during degradation, and 3OC₁₂HSL on completion of degradation could be identified by liquid chromatography-quadrupole time of flight. Thin-layer chromatography, Fourier transform infrared spectroscopy, and gas chromatography mass spectrometry confirmed the complete degradation of phenol in 48–56 h. P. putida JMQS1 exhibited adaptation over phenol stress through the selective activation of the quorum sensing signal molecules depending on the changing physiological conditions. This study proposes an efficient method for enhancing the degradation of toxic organic pollutants by the supplementation of acyl homoserine lactone signal molecules.

The Songhua River (SHR) is one of the seven major rivers in China. It feeds into Heilongjiang River, which is the natural border river between China and Russia. The water quality and security of the border river plays an important role in relations of two countries and the economic development for border region. This article collects the papers about researches on organic pollutant in SHR of recent 40 years. With the research study result, this article analyses organic pollutant change trend in terms of detected category, amount and distribution. It shows that the organic pollution is severe and caused negative impact on ecological environment because of industrial development near river bank during 1970–2000. The water quality of SHR has been improved and changed to slight pollution due to the implementation of basin pollution prevention planning in 21st century. The pollutant categories have decreased with lower concentration trend. This study suggests the research orientation for organic pollution of SHR in the future.

Copper-based algaecides are used to control algae that compromise uses of lakes and reservoirs. However, there are concerns regarding potential adverse effects to benthic macroinvertebrates following long-term, repeated applications. Multiple lines-of-evidence are useful for evaluating potential ecological risks. These lines-of-evidence are encompassed in the sediment quality triad (SQT) and include sediment copper concentrations, in situ benthic invertebrate abundance, and sediment toxicity testing. The objective of this study was to measure potential ecological risks associated with long-term applications of copper algaecides in coves in Lay Lake, Alabama. Sediments from three coves treated for 7, 10, and 20 years were compared to sediments from three untreated coves in terms of copper concentrations, in situ benthic macroinvertebrate total abundance, and survival of Hyalella azteca and Chironomus dilutus in laboratory sediment toxicity tests. Sediment copper concentrations were not different between treated and untreated coves, with the exception of one treated cove (PC-1S) that contained elevated sediment copper concentrations compared to all other coves. However, the copper was not bioavailable to organisms based on in situ macroinvertebrate abundance and laboratory toxicity tests. In situ benthic invertebrate abundance was not different between treated and untreated coves. In all sediments tested, there were no measurable adverse effects to H. azteca and there were no significant differences in survival of C. dilutus between treated and untreated coves. Based on the weight-of-evidence approach utilized in this study, long-term copper use in three Lay Lake coves has not resulted in adverse effects to benthic invertebrates compared to untreated coves.

Triclosan (TCS) is an antimicrobial agent that is extensively used in personal care products (PCPs), and its residue is frequently reported in aquatic environments. In this study, we investigated the reaction behavior of TCS during enzyme-catalyzed oxidative coupling reactions (ECOCRs) by laccase from Pleurotus ostreatus and determined how the presence of natural organic matter (NOM) influenced the formation of the products. Results indicated that the optimum pH for TCS transformation was 6.0 in laccase-mediated ECOCRs. At pH values below 5.0 and above 7.0, the pseudo first-order kinetic rate constants (k) of TCS transformation declined significantly. Moreover, the k values of TCS transformation increased as the laccase activity increased (0.1179–0.5757 h⁻¹). A total of four product peaks were generated, and they were more hydrophobic than TCS. High-resolution mass spectrometry (HRMS) analysis indicated that these products could be the oligomers resulting from TCS self-coupling reactions. The relative peak areas of these oligomers displayed strong linear correlations with the different initial TCS concentrations, and the saturation point of laccase (3.0 U mL⁻¹), when the binding with TCS was 40 μmol L⁻¹. In the presence of NOM (i.e., humates and fulvates), humates in particular strongly inhibited TCS transformation and lowered the extent of its self-coupling, which likely resulted from the cross-coupling between TCS and NOM. Our study improves a better understanding of the reaction behavior of TCS in the natural aquatic environment during laccase-mediated ECOCRs.

A greenhouse experiment was accomplished to investigate the feasibility of excess sludge modified by coal fly ash pretreatment and γ-ray irradiation in soil application for cultivation of Artemisia ordosica. The results showed that modified excess sludge provided a positive effect on the growth of Artemisia ordosica. The modified excess sludge and aeolian sandy soil at the volume ratio of 1:2 was optimal, and nutrient concentrations of Artemisia ordosica reached the highest. In the aeolian sandy soil, the bio-concentration factor values of most heavy metals were less than 1.0 except for Cu, Zn, and Ni. The average bio-concentration factor values of heavy metals in Artemisia ordosica increased in a sequence of Mo < Cd < Fe < V < Cr < Co < Mn < Pb < Cu < Zn < Ni for all samples. Artemisia ordosica could be used to decrease the bioavailability and eco-toxicity of Ni, V, and Mo in all cultivation experiments of artificial soil, and Artemisia ordosica could also reduce the bioavailability and eco-toxicity of Cu, Cd, Cr, and Mn in the artificial soil of modified excess sludge and aeolian sandy soil at the volume ratio of 1:2.

Ecological ditches have demonstrated the ability to filter and control nutrient transport to rivers. Few studies, however, have examined the internal loading of nitrogen (N) and phosphorus (P) in these systems due to vegetation decomposition. Most often, this concept is overlooked during evaluation of the nutrient removal rate of the ditches. Thus, the litter bag technique was used to analyze nutrient release to surface water during these processes. Mesocosm and field experiments were conducted to assess the growth characteristics and consequent nutrient accumulation by six ditch plant species. Of the six, Canna indica had the highest aboveground accumulation of N and P. About 85–95 % increase in the aboveground biomass was recorded at the end of the experimental period. The removal efficiencies of TN, TP, and NH₄-N from the sewage reached up to 72–99.4, 64–98.7, and 75 %–100, respectively. Complete removal of all NO₃-N was achieved. The amounts of N and P uptake by plant species were closely related to the biomass of plants. During the decaying process, N and P concentrations in the aboveground biomass decreased. These lost nutrients were eventually shifted to the system, which led to a deterioration of the water quality. Therefore, harvesting of aboveground biomass from inside the ditch is an appropriate intervention to prevent the release of N and P in the dormant season. The finding is important for planning an efficient eco-ditch system and predicting the influence of nutrient loading in the eco-ditches upon senescence of ditch plants.