Inhibition of TTX-S Na+ currents by a novel blocker QLS-278 for antinociception.

Genetic loss-of-function mutations of Nav1.7 channel, abundantly expressed in peripheral nociceptive neurons, cause congenital insensitivity to pain (CIP) in humans, indicating that selective inhibition of the channel may lead to potential therapy of pain disorders. In this study, we investigated a novel compound, 5-chloro-N-(cyclopropylsulfonyl)-2-fluoro-4-(2-(8-(furan-2-ylmethyl)-8-azaspiro [4.5] decan-2-yl) ethoxy) benzamide (QLS-278) that inhibits Nav1.7 channel and exhibits anti-nociceptive activity. Compound QLS-278 exhibits inactivation- and concentration-dependent inhibition of macroscopic currents of Nav1.7 channels stably expressed in HEK293 cells with an IC50 of 1.2 {plus minus} 0.2 µM. QLS-278 causes a hyperpolarization shift of the channel inactivation and delays recovery from inactivation, without an obvious effect on voltage-dependent activation. In mouse DRG neurons, QLS-278 suppresses native TTX-sensitive Nav currents and also reduces neuronal firing. Moreover, QLS-278 dose-dependently relieves neuropathic pain induced by spared nerve injury and inflammatory pain induced by formalin without significant alteration of spontaneous locomotor activity in mice. Altogether, our identification of the novel compound QLS-278 may hold developmental potential for the treatment of chronic pain. Significance Statement QLS-278, a novel voltage-gated sodium Nav1.7 channel blocker, inhibits native TTX-S Na+ current and reduces action potential firings in DRG sensory neurons. QLS-278 also exhibits antinociceptive activity in mouse models of pain, thus demonstrating potential for the development of a treatment for chronic pain.

Novel selective κ agonists SLL-039 and SLL-1206 produce potent antinociception with fewer sedation and aversion.

SLL-039 (N-cyclopropylmethyl-7α-4'-(N'-benzoyl) amino-phenyl-6,14-endoethano-tetrahydronorthebaine) and SLL-1206 (N-cyclopropylmethyl-7α-3'-(p-methoxybenzyl) amino-phenyl-6,14-endoethano-tetrahydronorthebaine) are two 4,5-epoxymorphinan-based high selective κ receptor agonists that we recently discovered. In the present study we characterized their pharmacological properties in comparison with arylacetamide-based typical κ agonist U50,488H. We showed that both SLL-039 and SLL-1206 produced potent and long-lasting antinociceptive actions in three different rodent models of pain via activation of κ opioid receptor. In hot-plate assay, the antinociceptive potency of SLL-039 and SLL-1206 increased about 11-and 17.3-fold compared to U50,488H and morphine, respectively, with ED50 values of 0.4 mg/kg. Following repeated administration, SLL-1206, SLL-039, and U50,488H all developed analgesic tolerance tested in hot-plate assay. U50,488H and SLL-039 produced antipruritic effects in a dose-dependent manner, whereas SLL-1206 displayed some antipruritic effects only at very low doses. In addition, SLL-1206 was capable of decreasing morphine-induced physical dependence. More importantly, SLL-039 and SLL-1206 at effective analgesic doses did not cause sedation and conditioned place aversion (CPA), whereas U50,488H did. In comparison with SLL-039, SLL-1206 caused similar antinociceptive responses, but fewer sedation and CPA. In conclusion, our results suggest that SLL-039 and SLL-1206 have potential to be developed as novel analgesic agents, and 4,5-expoxymorphinan scaffold is an attractive structure for the development of selective κ agonists with fewer side effects.

Inhibition of Nav1.7 channel by a novel blocker QLS-81 for alleviation of neuropathic pain.

Voltage-gated sodium channel Nav1.7 robustly expressed in peripheral nociceptive neurons has been considered as a therapeutic target for chronic pain, but there is no selective Nav1.7 inhibitor available for therapy of chronic pain. Ralfinamide has shown anti-nociceptive activity in animal models of inflammatory and neuropathic pain and is currently under phase III clinical trial for neuropathic pain. Based on ralfinamide, a novel small molecule (S)-2-((3-(4-((2-fluorobenzyl) oxy) phenyl) propyl) amino) propanamide (QLS-81) was synthesized. Here, we report the electrophysiological and pharmacodynamic characterization of QLS-81 as a Nav1.7 channel inhibitor with promising anti-nociceptive activity. In whole-cell recordings of HEK293 cells stably expressing Nav1.7, QLS-81 (IC50 at 3.5 ± 1.5 µM) was ten-fold more potent than its parent compound ralfinamide (37.1 ± 2.9 µM) in inhibiting Nav1.7 current. QLS-81 inhibition on Nav1.7 current was use-dependent. Application of QLS-81 (10 µM) caused a hyperpolarizing shift of the fast and slow inactivation of Nav1.7 channel about 7.9 mV and 26.6 mV, respectively, and also slowed down the channel fast and slow inactivation recovery. In dissociated mouse DRG neurons, QLS-81 (10 µM) inhibited native Nav current and suppressed depolarizing current pulse-elicited neuronal firing. Administration of QLS-81 (2, 5, 10 mg· kg-1· d-1, i.p.) in mice for 10 days dose-dependently alleviated spinal nerve injury-induced neuropathic pain and formalin-induced inflammatory pain. In addition, QLS-81 (10 µM) did not significantly affect ECG in guinea pig heart ex vivo; and administration of QLS-81 (10, 20 mg/kg, i.p.) in mice had no significant effect on spontaneous locomotor activity. Taken together, our results demonstrate that QLS-81, as a novel Nav1.7 inhibitor, is efficacious on chronic pain in mice, and it may hold developmental potential for pain therapy.

7ß-Methyl substituent is a structural locus associated with activity cliff for nepenthone analogues.

With the purpose of identifying novel selective κ opioid receptor (KOR) antagonists as potential antidepressants from nepenthone analogues, starting from N-nor-N-cyclopropylmethyl-nepenthone (SLL-020ACP), a highly selective and potent KOR agonist, a series of 7ß-methyl-nepenthone analogues was conceived, synthesized and assayed on opioid receptors based on the concept of hybridization. According to the pharmacological results, the functional reversal observed in orvinol analogues by introduction of 7ß-methyl substituent could not be reproduced in nepenthone analogues. Alternatively, introduction of 7ß-methyl substituent was associated with substantial loss of both subtype selectivity and potency but not efficacy for nepenthone analogues, which was not found in 7ß-methyl orvinol analogues. Surprisingly, SLL-603, a 7ß-methyl analogue of SLL-020ACP, was identified to be a KOR full agonist. The possible molecular mechanism for the heterogeneity in activity cliff was also investigated. In conclusion, 7ß-methyl substituent was a structural locus associated with activity cliff and demonstrated as a pharmacological heterogeneity between nepenthone and orvinol analogues that warrants further investigations.

Phytotoxicity and groundwater impacts of leaching from thermal treatment residues in roadways.

The use of coal fly ash (CFA), municipal solid waste incinerator bottom ash (MSWIBA) and flue gas desulfurization residue (FGDR) in road construction has become very common owing to its economical advantages. However, these residues may contain toxic constituents that pose an environmental risk if they leach out and flow through the soil, surface water and groundwater. Therefore, it is necessary to assess the ecotoxicity and groundwater impact of these residues before decisions can be made regarding their utilization for road construction. In this study, the physico-chemical characteristics, leaching and phytotoxicity of these residues were investigated. Specifically, multivariate analyses were used to evaluate the contributions of the leaching constituents of the CFA, MSWIBA and FGDR leachates to the germination index of wheat seeds. B, Ba, Cr, Cu, Fe and Pb were found to be more toxic to the wheat seeds than the other heavy metals. Furthermore, the leached concentrations of the constituents from the CFA, MSWIBA and FGDR were below the regulatory threshold limits of the Chinese identification standard for hazardous wastes. Analyses conducted using a numerical groundwater model (WiscLEACH) indicated that the predicted field concentrations of metals from the CFA, MSWIBA and FGDR increased with time up to about 30years at the point of compliance, then decreased with time and distance. Overall, this study demonstrated that the risks resulting from MSWIBA, CFA and FGDR leaching could be assessed before its utilization for road construction, providing crucial information for the adoption of these alternative materials.

A comparison of chemical MSW compositional data between China and Denmark.

Chemical waste compositions are important for municipal solid waste management, as they determine the pollution potentials from different waste strategies. A representative dataset for chemical characteristics of individual waste fractions is frequently required to assess chemical waste composition, but it is usually reported in developed countries and not in developing countries. In this study, a dataset for Chinese waste was established through careful data screening and assessment, named as CN dataset. Meanwhile, a dataset for Danish waste (DK dataset) was also summarized based on previous studies. In order to quantitatively evaluate the reliabilities of CN and DK datasets, the chemical waste compositions in four Chinese cities were estimated by utilizing both of them, respectively. It is indicated that the usage of CN datasets led to significantly lower discrepancies from the actual values based on laboratory analysis in most cases. Within the datasets, the moisture contents of food waste, paper, textiles, and plastics, the carbon content of food waste, as well as the oxygen content of plastics would induce significant divergences, which should be paid special attention when gathering the information. In addition, the fractional waste compositions in China showed similar features with other developing countries but differ significantly with developed countries. Thus the above-mentioned conclusions could also be true in other developing countries.

Discovery, synthesis, biological evaluation and structure-based optimization of novel piperidine derivatives as acetylcholine-binding protein ligands.

The homomeric α7 nicotinic receptor (α7 nAChR) is widely expressed in the human brain that could be activated to suppress neuroinflammation, oxidative stress and neuropathic pain. Consequently, a number of α7 nAChR agonists have entered clinical trials as anti-Alzheimer's or anti-psychotic therapies. However, high-resolution crystal structure of the full-length α7 receptor is thus far unavailable. Since acetylcholine-binding protein (AChBP) from Lymnaea stagnalis is most closely related to the α-subunit of nAChRs, it has been used as a template for the N-terminal domain of α-subunit of nAChR to study the molecular recognition process of nAChR-ligand interactions, and to identify ligands with potential nAChR-like activities.Here we report the discovery and optimization of novel acetylcholine-binding protein ligands through screening, structure-activity relationships and structure-based design. We manually screened in-house CNS-biased compound library in vitro and identified compound 1, a piperidine derivative, as an initial hit with moderate binding affinity against AChBP (17.2% inhibition at 100 nmol/L). During the 1st round of optimization, with compound 2 (21.5% inhibition at 100 nmol/L) as the starting point, 13 piperidine derivatives with different aryl substitutions were synthesized and assayed in vitro. No apparent correlation was demonstrated between the binding affinities and the steric or electrostatic effects of aryl substitutions for most compounds, but compound 14 showed a higher affinity (Ki=105.6 nmol/L) than nicotine (Ki=777 nmol/L). During the 2nd round of optimization, we performed molecular modeling of the putative complex of compound 14 with AChBP, and compared it with the epibatidine-AChBP complex. The results suggested that a different piperidinyl substitution might confer a better fit for epibatidine as the reference compound. Thus, compound 15 was designed and identified as a highly affinitive acetylcholine-binding protein ligand. In this study, through two rounds of optimization, compound 15 (Ki=2.8 nmol/L) has been identified as a novel, piperidine-based acetylcholine-binding protein ligand with a high affinity.

Inhibitory effect of high calcium concentration on municipal solid waste leachate treatment by the activated sludge process.

This research focused on the inhibitory effects of Ca on the aerobic biological treatment of landfill leachate containing extremely high Ca concentrations. When the Ca concentration in leachate to be treated was more than 4500 mg l-1, the total organic carbon removal rate was significantly reduced and the processing time to achieve the same removal efficiency was 1.4 times that in the control treatment without added Ca. In contrast, the total nitrogen and ammonia nitrogen (NH4+-N) removal efficiencies were positively related to the Ca concentration, increasing from 65.2% to 81.2% and from 69.2% to 83.7%, respectively, when the dosage of added Ca increased from zero to 8000 mg l-1. During aerobic treatment, the reductions of solution Ca concentration were in the range of 1003-2274 mg l-1 and were matched with increases in the Ca content in the residual sludge. The inhibition threshold of Ca in the leachate treated by the activated sludge process appeared to be 4500 mg l-1, which could be realized by controlling the influent Ca concentration and using an appropriate sludge return ratio in the activated sludge process.

[Dynamic Posturography of Injured Lower Limb in Postural Evoked Response].

OBJECTIVE: To analyze the balance function of injured lower limb by dynamic posturography. METHODS: Using the dynamic posturography instrument, the postural evoked responses of sixty-two normal people and two hundred and fifty-eight people with injured lower limb bones and joints were detected. The test was included sensory organization test (SOT) and adaption test (ADT). The results of two groups were compared by t test. RESULTS: Compared with the normal people, the impaired people had significant statistical differences in balance scores of SOT3-SOT6 and proportion score of dynamic proprioception (P < 0.05). There was no obvious decrease in ADT. CONCLUSION: The balance function of injured lower limb significantly decreases.

Drug-drug interaction of rabeprazole and clopidogrel in healthy Chinese volunteers.

PURPOSE: This study was aimed to determine the impact of rabeprazole (RBRZ) on the antiplatelet efficacy of clopidogrel (CPG) in healthy Chinese volunteers, and further to predict the effect of CYP2C19 genetic polymorphism on the efficacy of rabeprazole and clopidogrel. METHODS: The open-label, two period cross-over study was conducted in 20 healthy Chinese subjects with different CYP2C19 genotypes receiving clopidogrel, rabeprazole or the two drugs, respectively. All the volunteers were divided into two groups, poor metabolizers (PMs) and extensive metabolizers (EMs), depending on CYP2C19 genotypes. Blood samples were collected at baseline and at 0.5, 1, 2, 3, 4, 6, 8, 10, and 12 h after administration. The plasma concentrations of rabeprazole and clopidogrel were analyzed by LC-MS/MS and ADP-induced platelet aggregation was detected by the optical turbidimetric method. RESULTS: There were no significant differences in the mean plasma concentration-time curves of clopidogrel (CPG), the inactive metabolite clopidogrel carboxylic acid (CPG-CA), the active metabolite clopidogrel-MP-Derivative (MP-AM), and rabeprazole (RBRZ) according to the co-administration of CPG and RBRZ. There were no major changes in the pharmacokinetics of CPG and RBRZ. The maximal ADP-induced platelet aggregation (2 µmol/L) was decreased in EMs compared with PMs. CONCLUSION: Co-administration of rabeprazol and clopidogrel did not affect the antiplatelet efficacy of clopidogrel. The CYP2C19 genetic polymorphism may impact the efficacy of clopidogrel.

Greenhouse gas emissions during MSW landfilling in China: influence of waste characteristics and LFG treatment measures.

Reducing greenhouse gas (GHG) emissions from municipal solid waste (MSW) treatment can be highly cost-effective in terms of GHG mitigation. This study investigated GHG emissions during MSW landfilling in China under four existing scenarios and in terms of seven different categories: waste collection and transportation, landfill management, leachate treatment, fugitive CH4 (FM) emissions, substitution of electricity production, carbon sequestration and N2O and CO emissions. GHG emissions from simple sanitary landfilling technology where no landfill gas (LFG) extraction took place (Scenario 1) were higher (641-998 kg CO2-eq·t(-1)ww) than those from open dump (Scenario 0, 480-734 kg CO2-eq·t(-1)ww). This was due to the strictly anaerobic conditions in Scenario 1. LFG collection and treatment reduced GHG emissions to 448-684 kg CO2-eq·t(-1)ww in Scenario 2 (with LFG flare) and 214-277 kg CO2-eq·t(-1)ww in Scenario 3 (using LFG for electricity production). Amongst the seven categories, FM was the predominant contributor to GHG emissions. Global sensitivity analysis demonstrated that the parameters associated with waste characteristics (i.e. CH4 potential and carbon sequestered faction) and LFG management (i.e. LFG collection efficiency and CH4 oxidation efficiency) were of great importance. A further learning on the MSW in China indicated that water content and dry matter content of food waste were the basic factors affecting GHG emissions. Source separation of food waste, as well as increasing the incineration ratio of mixed collected MSW, could effectively mitigate the overall GHG emissions from landfilling in a specific city. To increase the LFG collection and CH4 oxidation efficiencies could considerably reduce GHG emissions on the landfill site level. While, the improvement in the LFG utilization measures had an insignificant impact as long as the LFG is recovered for energy generation.

The emission patterns of volatile organic compounds during aerobic biotreatment of municipal solid waste using continuous and intermittent aeration.

Because volatile organic compounds (VOCs) are one of the main concerns during municipal solid waste (MSW) treatment, the release patterns and the environmental effects of VOCs were investigated during laboratory-scale aerobic biotreatments of MSW with continuous and intermittent negative ventilation. When the same airflow amounts were used, intermittent ventilation was found to reduce the total VOC emissions from continuous ventilation process by 28%. In this study, 23 types of volatile organic compounds were analyzed, of which butyraldehyde, ethanol, and butanone were emitted in the highest concentrations of 748, 372, and 260 mg/m3, respectively. During the aerobic biotreatment process, ketones, aldehydes, and alcohols were primarily released during the first 4 days, accounting for 86-98% of the total VOC emissions during this period. The emission concentrations of malodorous sulfide compounds displayed two peaks on day 4 and day 9, with the contribution to the total VOC emissions being enhanced from less than 10% to 76-83%. The release of terpenes and aromatics lasted for more than 10 days with no significant emission peaks and the proportions of those compounds in the total VOCs increased gradually, but no more than 50% even at the end of the process. Considering the strength of the odors, aldehydes were the predominant contributors at the beginning of the experiment, whereas malodorous sulfide compounds became the most odorous compound as the biological process continued. Most of the VOCs emitted at the concentrations beneath the level causing health threat to the workers.

Biodrying of municipal solid waste under different ventilation modes: drying efficiency and aqueous pollution.

Ventilation is very important during the biodrying process because it affects the biodrying efficiency and secondary pollution. In this study, three ventilation modes-intermittent negative ventilation (IN), continuous negative ventilation (CN) and intermittent positive ventilation (IP)-were used to provide the same amount of total air during biodrying of municipal solid waste (MSW). During the entire 16-day experiment, 68.4%, 68.7% and 67.2% of water contained in the initial waste was removed under IN, CN and IP trials respectively. The ratio of water loss to volatile solid loss was used to evaluate the biodrying efficiency, with values of 5.35, 5.93 and 4.82 being observed for IN, CN and IP trials respectively. The total organic carbon concentrations of the leachate generated from the biodrying of waste were as high as 25,000 mg/l, while those of the condensate were not higher than 3500 mg/l. During the entire process, the average ammonia concentrations of leachate and condensate were 1350 mg/l and 2140 mg/l respectively. From the aspect of biodrying efficiency, continuous negative ventilation was the most preferable ventilation mode for biodrying of MSW, while special care should be taken to prevent aqueous pollution if it is used in a MSW treatment plant.

[Temporal and Spatial Variation in Odor Pollution and Membrane Barrier Effect in Municipal Solid Waste Landfill].

In order to explore the source characteristics as well as the temporal and spatial variations in odor pollution in municipal waste landfills, gas samples were collected from a landfill in an eastern coastal area of China throughout winter and summer. The total concentration of malodorous substances reached 60000 µg·m-3. There were more types of odor pollutants detected in summer than in winter, the average concentration was 30-300 times higher than that in winter, and the concentration of sulfur compounds increased by 4.7-136.7 times in summer. Oxygenated compounds had the highest concentration, and the total concentration of sulfur compounds accounted for less than 10% of malodorous substances. However, sulfur compounds contributed more than 90% to the theoretical odor concentration. Sulfur compounds such as methyl mercaptan and propane mercaptan were the key odorants in the landfill. After the landfill unit was covered, the concentration of odorous substances and the theoretical odor concentration on the surface of the landfill showed an increasing trend with time, indicating that the covering had a certain odor barrier effect; however, the landfill unit still had a large odor release potential. The similarity analysis showed that the odorous gas accumulated in the unit with temporary cover and without an exhaust system could be released to the environment through the overlapping gap of the membrane and the location of membrane rupture, resulting in more serious odor pollution around the landfill at night than that during the day.

Repercussions of clinical waste co-incineration in municipal solid waste incinerator during COVID-19 pandemic.

During coronavirus disease 2019 pandemic, the exponential increase in clinical waste (CW) generation has caused immense burden to CW treatment facilities. Co-incineration of CW in municipal solid waste incinerator (MSWI) is an emergency treatment method. A material flow model was developed to estimate the change in feedstock characteristics and resulting acid gas emission under different CW co-incineration ratios. The ash contents and lower heating values of the feedstocks, as well as HCl concentrations in flue gas showed an upward trend. Subsequently, 72 incineration residue samples were collected from a MSWI performing co-incineration (CW ratio <10 wt%) in Wuhan city, China, followed by 20 incineration residues samples from waste that were not co-incineration. The results showed that the contents of major elements and non-volatile heavy metals in the air pollution control residues increased during co-incineration but were within the reported ranges, whereas those in the bottom ashes revealed no significant changes. The impact of CW co-incineration at a ratio <10 wt% on the distribution of elements in the incineration residues was not significant. However, increase in alkali metals and HCl in flue gas may cause potential boiler corrosion. These results provide valuable insights into pollution control in MSWI during pandemic.

Upcycling waste polyvinyl chloride: One-pot synthesis of valuable carbon materials and pipeline-quality syngas via pyrolysis in a closed reactor.

Polyvinyl chloride (PVC) is one of the most commonly used plastics. The treatment and recycling of PVC waste is still challenging, due to its non-biodegradability, low thermal stability, high Cl content and low product value. In this study, a one-pot method was developed to upcycle PVC into valuable carbon materials, pipeline-quality pyrolysis gas and chlorides. The well-designed process included dechlorination by Cl-fixative (ZnO or KOH), carbonization of dechlorinated polyenes, and modification of carbon materials in sequence. ZnO and KOH converted 84.48% and 94.15% of total Cl into corresponding chlorides, respectively. CH4 and H2 accounted for 81.87-99.34 vol% of pyrolysis gas with higher heat values of 30.11-32.84 MJ m-3, which can be used as substitute natural gas. As high as 83.13% of the C element was converted into carbon materials. The morphology, structure and property of carbon materials can be modified by different Cl-fixatives. Millimeter-scale carbon spheres with mono-dispersity and porous carbon with a high specific surface area of 1922 m2 g-1 were obtained when ZnO and KOH were added, respectively. Moreover, the reaction mechanisms of PVC with Cl-fixatives were also deciphered through thermogravimetric analysis and thermodynamic simulation.

Predominant contribution of syntrophic acetate oxidation to thermophilic methane formation at high acetate concentrations.

To quantify the contribution of syntrophic acetate oxidation to thermophilic anaerobic methanogenesis under the stressed condition induced by acidification, the methanogenic conversion process of 100 mmol/L acetate was monitored simultaneously by using isotopic tracing and selective inhibition techniques, supplemented with the analysis of unculturable microorganisms. Both quantitative methods demonstrated that, in the presence of aceticlastic and hydrogenotrophic methanogens, a large percentage of methane (up to 89%) was initially derived from CO(2) reduction, indicating the predominant contribution of the syntrophic acetate oxidation pathway to acetate degradation at high acid concentrations. A temporal decrease of the fraction of hydrogenotrophic methanogenesis from more than 60% to less than 40% reflected the gradual prevalence of the aceticlastic methanogenesis pathway along with the reduction of acetate. This apparent discrimination of acetate methanization pathways highlighted the importance of the syntrophic acetate-oxidizing bacteria to initialize methanogenesis from high organic loadings.

Environmental and economic assessment of combined biostabilization and landfill for municipal solid waste.

Biostabilization can remove considerable amounts of moisture and degradable organic materials from municipal solid waste (MSW), and can therefore be an effective form of pretreatment prior to landfill. The environmental and economic impacts of two combined processes, active stage biostabilization + sanitary landfill (AL), and active and curing stage biostabilization + sanitary landfill (ACL), were compared with sanitary landfill (SL) for MSW with high moisture content. The results indicated that land requirement, leachate generation, and CH(4) emission in the ACL process decreased by 68.6%, 89.1%, and 87.6%, respectively, and the total cost was reduced by 24.1%, compared with SL. This implies that a combined biostabilization and landfill process can be an environmentally friendly and economically feasible alternative to landfill of raw MSW with high moisture content. Sensitivity analysis revealed that treatment capacity and construction costs of biostabilization and the oxidation factor of CH(4) significantly influenced the costs and benefits of the AL and ACL process at an extremely low land price. When the land price was greater than 100 USD m(-2), it became the dominating factor in determining the cost of treatment and disposal, and the total costs of ACL were reduced to less than 40% of those of SL.

Leaching behaviour of bisphenol A from municipal solid waste under landfill environment.

With a preliminary insight into the source and leaching behaviour ofbisphenol A (BPA) from municipal solid wastes (MSW), five kinds of plastic and four kinds of paper materials were leached by distilled water. Polyvinyl chloride (PVC) waste was found to have the highest BPA content of 12.1 microg x g(-1) and leachability of 34.7% in distilled water, while cardboard with relatively low BPA content also showed a high ratio of leaching (53.6%). Fresh leachate and leachates from a landfill of age 1.5 and 10 years were adopted as leachants for the PVC plastic and cardboard to simulate the leaching behaviour of BPA under a landfill environment. The enhancement of BPA leachability in the 10-year leachate compared with distilled water was higher than that in the other two leachates due to its basic pH and high content of humic organic matters. Meanwhile, the enhancement of BPA leachability by the fresh leachate was higher than that by the 1.5-year leachate, possibly due to the presence of small molecules such as volatile fatty acids, amino acids, etc. The paper waste was not only a minor origin of BPA leaching, but also a controlling factor in retarding BPA transformation. The BPA sorption K(f) value of the cardboard in the Freundlich equation was 0.2224 mg(1-n)) x L(n) x g(-1) (n = 0.7680), higher than that obtained in sorption experiments by natural organic adsorbents such as sediment. It suggested that the presence of paper with a high sorption capacity in MSW will restrain BPA transport and bioavailability in landfills.

Effect of biostabilization on the release potential and speciation of heavy metals in municipal solid waste.

Biostabilization prior to landfilling of municipal solid waste (MSW) has been developed to reduce leachate pollution and increase landfill capacity and stability. Leaching tests were used in this study to examine the effect of biostabilization on the release potential and fate of heavy metals in MSW. The speciation of heavy metals in leached MSW and leachates, and their distribution in different molecular weight (MW) fractions of organic matter in leachate were studied. The results showed that a 44-day biostabilization period could lower the release potential of Pb, Cr, Cd, Cu, and Zn in MSW by 50 to 84%. With the exception for Zn, biostabilization tended to decrease the percentages of the metals in the leachate organic fraction with MW < 1 kDa, but increase those of metals associated with organic colloids and high-MW fractions. Therefore, the effects of biostabilization on the behaviour and fate of Pb, Cr, Cd and Cu in leachate would vary in treatment facilities that use different methods and in the natural environment. Biostabilization only slightly affected the behaviour and fate of Zn, due to an insignificant variation in the speciation and distribution of Zn in different MW fractions. In addition, the aerobic and hydrolytic-aerobic biostabilization processes showed similar release potential, speciation, and distribution of heavy metals in different MW fractions.