Coastal sediment heavy metal(loid) pollution under multifaceted anthropogenic stress: Insights based on geochemical baselines and source-related risks.

Contamination and risk assessments generally ignore the potential bias in results caused by the variation of background values at different spatial scales due to the spatial heterogeneity of sediments. This study aims to perform quantitative source-ecological risk assessment via establishing geochemical baselines values (GBVs) of heavy metal(loid)s (HMs) in Daya Bay, China. Cumulative frequency distribution (CFD) curves determined the GBVs of 12.44 (Cu), 30.88 (Pb), 69.89 (Zn), 0.06 (Cd), 47.85 (Cr), 6.80 (As), and 0.056 mg kg-1 (Hg), which were comparable to the background values of Guangdong Province surface soils, and implied a potential terrestrial origin of the coastal sediments. Principal component analysis (PCA) and positive matrix factorization (PMF) identified three sources (F1: natural processes; F2: anthropogenic impacts; F3: specific sources) with contributions of 51.7%, 29.2%, and 19.1%, respectively. The source-specific risk assessment revealed an ecological risk contribution potential of 73.8% for the mixed anthropogenic sources (F2 + F3) and only 26.2% for natural processes. Cd and Hg were the priority management of metallic elements, occupying 63.5% and 72.5% of the contribution weights of F2 and F3, respectively, which showed multi-level pollution potentials and ecological risk levels. The spatial distribution patterns demonstrated the hotspot features of HM pollution, and priority concerns should be given to the management of marine traffic and industrial point source pollution in Daya Bay. The results of the study provide a scientific approach and perspective for pollution treatment and risk management in the coastal environment.

Heavy metal(loid)s in multiple media within a mussel mariculture area of Shangchuan Island, China: Partition, transfer and health risks.

Limited research has been conducted on the heavy metal (loid) (HM) exchanges among seawater, sediments and cultured mussels in mariculture areas. To determine the impacts of mussel mariculture on the transfer and risks of HMs in coastal environments, samples of seawater, sediments and cultured mussels from a typical mariculture area in the South China Sea were analysed. The logarithmic partition coefficients of sediment/water indicated that HMs were preferentially retained by sediments. There were relatively low ecological risks in mussel raft mariculture areas. Principal component analysis and correlation analysis revealed the influences of terrestrial input and ocean circulation on the HMs in seawater, and the bioaccumulation factors reflected the possible accumulation of HMs in seawater by cultured mussels. Mussel farming was the indirect source of HMs in sediments, and the biochemical processes of cultured mussels promoted the transfer and accumulation of HMs into sediments. Health risk assessment revealed that children were more susceptible than adults, and Cd, As and Cr were among the threatening elements. Nonetheless, the health risks that were possibly caused by the daily consumption of farmed mussels were still within safe limits. Thus, the potential pollution remediation and biomonitoring functions of mussel aquaculture in coastal water environments will be further studied in the future.

Transcriptomic analysis dissects the regulatory strategy of toxic cyanobacterium Microcystis aeruginosa under differential nitrogen forms.

The critical role of nitrogen in the global proliferation of cyanobacterial blooms is arousing increasing attention. However, the mechanism underlying the algal responses to differential nitrogen forms remains unclarified. The physiological and transcriptomic changes of Microcystis aeruginosa supplied with different nitrogen forms (nitrate and ammonium) were highlighted in this study. The results indicated that ammonium behaves better in stimulating the initial growth in N-limited cells than nitrate. However, a concomitant side effect is that cellular growth and photosynthesis decreased due to photosystem II damage induced by excess absorbed light energy under 10 mg L-1 ammonium. By contrast, adequate nitrate supply favored more efficient photosynthesis, higher biomass yield and microcystin quotas than ammonium. Depending on the supplied nitrogen form, different transcriptomic patterns were observed in M. aeruginosa. Under nitrate, the upregulation of genes involved in Arg biosynthesis, ornithine-urea cycle and photosynthesis increased nitrogen storage and cellular growth, while genes involved in cyclic electron flow around photosystem I and CO2-concentrating mechanism were heightened to dissipate excess energy under high ammonium. These insights provided important clues for understanding the physiological and molecular effects of available nitrogen forms on the frequent outbreaks of cyanobacteria.

Spillover-feedback effects of social, economic, and environmental footprints based on the "Belt and Road Initiative".

The Belt and Road Initiative (BRI) links China to markets and sources of raw materials around the world while stimulating economic growth in developing countries and leading to widespread and occasionally unexpected social and environmental impacts. Considering that few studies have focused on the trade-embodied social and environmental impacts and two-way impact mechanisms throughout the BRI, this study, for the first time, uses social-economic-environmental footprints and the corresponding indicators of ecological efficiency and environmental stress to methodically measure the spatial distribution and regional transfer among three major regions comprising China (CHN), countries along the Belt and Road countries except China (CBR), and the rest of world (REW) from the standpoint of spillover and feedback effects, to better coordinate sustainable development between environment, economy, and society of the BRI. The results indicated the importance of spillover-feedback effects. Its significance lies not in comparison with the multiplier effect or the rates to TF, but in the indication of the two-way influence between regions through the numerical value of spillover-feedback effects of different regions and different industries. We identified that CBR and REW displayed the highest regional correlation in environment-economic aspects, followed by CHN and REW. The biggest contribution to the total footprint stemmed from the multiplier effects, suggesting the possibility that initiatives (e.g., BRI) could reduce the multiplier effects through internal drive optimization to offset the negative impact of spillover-feedback effects between regions (e.g., pollution transfer). Regarding employment, the feedback effects in CBR were the highest, suggesting that the indirect response due to the world's final demand pulled the largest employment in CBR. Moreover, REW was the net exporter of WF, CF, and EF, while the net importer of VAF and TOF. Furthermore, if ecological efficiency and environmental stress indicators were not considered, the stress of regional water resource use and carbon emission will be underestimated to a certain extent. For example, I-AGR of CHN and CBR in water resources stress, and III-HIS and V-EGW of CHN in carbon emissions stress. Finally, the proportions of different industries should be considered to evade misestimating the level of cleaner production in various industries during policymaking. Elucidating these mechanisms is essential to support decision-making that leads to sustainable development.

The proliferation rule of Microcystis aeruginosa under different initial pH conditions and its influence on the pH value of the environment.

This study investigated the characteristics of the proliferation process of Microcystis aeruginosa and its changes to environmental pH values under different initial pH values and different initial inoculation densities. The results showed that although the initial pH value or the initial inoculation density was different, the pH values of the culture systems fluctuated up and down throughout the proliferation of M. aeruginosa, both on a daily and hourly time scale, and then tended to stabilize around the same value of 10.0 at the end of proliferation. The optimal pH value for the proliferation of M. aeruginosa was 9.55. This study creatively proposes that the period when the environmental pH value starts to rise rapidly toward 9.0 could be selected as an early warning period for a cyanobacterial outbreak, and the environmental pH value could be adjusted to below 8.0 to delay the outbreak. These results provide a scientific basis for further understanding the mechanism of cyanobacterial blooms and formulating pH-based control strategies.

Effects of operating conditions on microbial consortium of the heterotrophic ammonia oxidation process.

This study aimed to investigate the ammonia removal by the consortium mainly comprising of ammonia-oxidizing bacteria under different initial pH, temperatures and stress of heavy metals. The results showed that the consortium exhibited a strong adaptation for broad pH ranging from 5 to 9. When the temperature dropped to 15℃, its ammonium removal and nitrate accumulation rates decreased by 72.23% and 95.12%, respectively. Meanwhile, the temperature correction coefficients of the ammonium removal and nitrate accumulation rates reached the maximum. In addition, the consortium could survive in the solutions containing 0-1.0 mg·L-1 Cu2+ and 0-5.0 mg·L-1 Fe3+. Moreover, the inhibition of free nitrous acid (FNA) against nitrite oxidation activity was found to be much more significant than that low-temperature treatment. Microbial diversity analysis showed that the bacterial community structure was shift significantly by the temperature drop, especially change the abundance of Nitrosomonas, Paracoccus, Pseudomonas and Nitrospirae.

Exploring the formulation of ecological management policies by quantifying interregional primary ecosystem service flows in Yangtze River Delta region, China.

Ecosystem services (ESs) play an important supporting role in the development of human society and the economy. Despite the increasing number of ESs quantitative evaluation studies that have been conducted at different scales, the assessment of ESs flows between different administrative regions, which provides valuable implications for ecological protection and compensation, has drawn little attention. The aim of this study is to fill in this gap by providing a comprehensive ES interregional flow analysis method that evaluates ecosystem service values (ESVs) and quantifies the interregional flows in the Yangtze River Delta (YRD), which is home to one of the largest urban agglomerations in China. The results showed that the total ESV of the YRD increased from 2.02E+12 Chinese Yuan (CNY) in 2000 to 2.33E+12 CNY in 2019, a 15.23% increase rate. All types of ESVs displayed an increasing trend during the 20 years. According to the analysis of interregional ES flows in the YRD, Zhejiang province played a crucial role as a service providing area (SPA) for the spatial value transfer at the provincial level in both 2000 and 2019. Anhui province was the largest service benefitting area (SBA) of water conservation and CSOP, while Jiangsu province was the largest SBA of soil retention. The recognition of interregional ESV flows can provide valuable information for environmental planning and management to help improve China's ecological compensation policies for different administrative divisions.

A strategy of high-efficient nitrogen removal by an ammonia-oxidizing bacterium consortium.

An ammonia-oxidizing bacterium consortium showed approximately 100% removal of NH4+-N with an initial concentration of 262.28 ±â€¯8.21 mg·L-1 within 10 days, and only 16.54 ±â€¯0.52% of NH4+-N was converted to NO2--N in this study. The consortium removed ammonium by heterotrophic nitrification and aerobic denitrification (HNAD) without N2O emission. The activity of AOB was not affected by low concentrations of FA or FNA, but completely inhibited by 0.04 mg HNO2·L-1. In a bioaugmentation treatment of eutrophic wastewater using the consortium, the removal efficiency of NH4+-N reached 90.85 ±â€¯0.8% and 77.88 ±â€¯1.86% at initial concentrations of 1.80 ±â€¯0.04 mg·L-1 and 40.31 ±â€¯0.57 mg·L-1, respectively, and the dissolved oxygen level had a significant impact on the consortium activity. No significant changes in the bacterial community structure were observed after the consortium addition, and local functional bacteria were enriched by aeration and contributed to ammonium nitrogen removal with AOB.

Growth, extracellular alkaline phosphatase activity, and kinetic characteristic responses of the bloom-forming toxic cyanobacterium, Microcystis aeruginosa, to atmospheric particulate matter (PM2.5, PM2.5-10, and PM>10).

Atmospheric particulate matter (APM), commonly seen and widely excited in environment, appears great enough to influence the biochemical processes in aquatic microorganisms and phytoplankton. Understanding the response of cyanobacteria to various factors is fundamental for eutrophication control. To clarify the response of cyanobacteria to APM, the effects of PM2.5, PM2.5-10, and PM>10 on Microcystis aeruginosa were researched. Variabilities in cell density, chlorophyll a, soluble protein, malondialdehyde, extracellular activity, and kinetic parameters of alkaline phosphatase were evaluated by lab-cultured experiments. Results showed that the PM2.5 had a slight stimulation impact on the growth and enhanced both of the 48- and 72-h extracellular alkaline phosphatase activity (APA), the affinity of alkaline phosphatase for substrate, and the 72-h maximum enzymatic reaction velocity (Vmax). Moreover, the stimulations in extracellular APA and Vmax enhanced with the increasing exposure concentrations. We also found there were no obvious distinctions on the effects of growth and alkaline phosphatase in M. aeruginosa between PM2.5-10 and PM>10 exposure groups. Obviously, inhibitory effects on growth existed in 4.0 and 8.0 mg/L PM2.5-10 and 8.0 mg/L PM>10 at 120 h. Furthermore, PM2.5-10 and PM>10 exerted inhibitory effects on the extracellular APA during the 72-h exposure. Simultaneously, the Vmax was notably inhibited and the affinity of alkaline phosphatase for substrate was more inseparable compared with control in PM2.5-10 and PM>10 treatments. Nevertheless, the inhibitors in extracellular APA and kinetic parameters were unrelated to PM2.5-10 and PM>10 exposure concentrations. Two-way ANOVA results revealed that there were significant interactions between exposure concentration and diameter of APM on the 120-h cell density, soluble protein content, APA, and 72 h APA of M. aeruginosa. These results in our study would be meaningful to further researches on relationships between APM deposition and cyanobacterial bloom.

Effects of Dihydroartemisinin and Artemether on the Growth, Chlorophyll Fluorescence, and Extracellular Alkaline Phosphatase Activity of the Cyanobacterium Microcystis aeruginosa.

Increased eutrophication in the recent years has resulted in considerable research focus on identification of methods for preventing cyanobacterial blooms that are rapid and efficient. The objectives of this study were to investigate the effects of dihydroartemisinin and artemether on the growth of Microcystis aeruginosa and to elucidate its mode of action. Variations in cell density, chlorophyll a, soluble protein, malondialdehyde, extracellular alkaline phosphatase activity (APA), and chlorophyll fluorescence parameters (Fv/Fm, ΦPSII, ETR, rapid light curves, fast chlorophyll fluorescence curves on fluorescence intensity, and relative variable fluorescence) were evaluated by lab-cultured experiments. Our results demonstrated that both dihydroartemisinin and artemether inhibited the growth of M.aeruginosa by impairing the photosynthetic center in photosystem II and reducing extracellular APA, with a higher sensitivity exhibited toward artemether. The inhibitory effects of dihydroartemisinin on M.aeruginosa increased with concentration, and the maximum growth inhibitory rate was 42.17% at 24 mg·L-1 after 120h exposure, whereas it was 55.72% at 6 mg·L-1 artemetherafter 120h exposure. Moreover, the chlorophyll fluorescence was significantly inhibited (p<0.05) after 120h exposure to 12 and 24 mg·L-1 dihydroartemisinin. Furthermore, after 120h exposure to 6 mg·L-1 artemether, Fv/Fm, ΦPSII, ETR and rETRmax showed a significant decrease (p<0.01) from initial values of 0.490, 0.516, 17.333, and 104.800, respectively, to 0. One-way analysis of variance showed that 6 mg·L-1 artemether and 24 mg·L-1 dihydroartemisinin had significant inhibitory effects on extracellular APA (p<0.01). The results of this study would be useful to further studies to validate the feasibility of dihydroartemisinin and artemether treatment to inhibit overall cyanobacterial growth in water bodies, before this can be put into practice.

Effects of garlic and diallyl trisulfide on the growth, photosynthesis, and alkaline phosphatase activity of the toxic cyanobacterium Microcystis aeruginosa.

To identify a botanical algicide and elucidate the response of cyanobacteria to the extract from higher plants, the effects of garlic and garlic-derived diallyl trisulfide on Microcystis aeruginosa were studied. Effects were evaluated by changes in cell density, chlorophyll a, maximum effective quantum yield (Fv/Fm), effective quantum yield (YII), non-photochemical quenching (NPQ), and rapid light curves of M. aeruginosa. In addition, alkaline phosphatase activity (APA) was measured when M. aeruginosa was incubated with diallyl trisulfide. Results indicated that the inhibition by garlic and diallyl trisulfide was significant. The 120-h 50 % effective concentrations of garlic and diallyl trisulfide (EC50) were 0.75 g L(-1) and 2.84 mg L(-1), respectively. Moreover, the inhibitory rate increased with increasing concentration and the growth of M. aeruginosa was inhibited by 90.0 % at the highest concentrations. We also show that the response of M. aeruginosa to stress could involve both impairment of the photosynthetic center PSII and alteration of APA. For example, at high garlic concentration (2.0 g L(-1)), Fv/Fm significantly decreased from 0.501 to 0.084 (p < 0.05) after 120 h of exposure. Furthermore, the total APA was significantly decreased by exposure to a high diallyl trisulfide concentration after 24 h exposure. As new algal inhibitors, there are several advantages for their utilization, such as being common, cheap, non-toxic, and with high efficiency. It would be meaningful to further research on garlic as an environmentally friendly algicide.

A novel photocatalytic material for removing microcystin-LR under visible light irradiation: degradation characteristics and mechanisms.

BACKGROUND AND PURPOSE: Microcystin-LR (MC-LR), a common toxic species in contaminated aquatic systems, persists for long periods because of its cyclic structure. Ag3PO4 is an environment-friendly photocatalyst with relatively good degradation capacity for hazardous organic pollutants. This study aimed to investigate the degradation capacity of Ag3PO4 for MC-LR under visible light. METHODS: An Ag3PO4 photocatalyst was synthesized by the ion-exchange method and characterized by X-ray diffraction, field-emission scanning electron microscope, and UV-Vis spectrophotometer. MC-LR was quantified in each sample through high-performance liquid chromatograph. The degradation efficiency of MC-LR was affected by initial pH, initial Ag3PO4 concentration, initial MC-LR concentration, and recycle experiments. The degradation intermediates of MC-LR were examined by liquid chromatography-mass spectrometry (LC/MS). RESULTS: The degradation process can be well fitted with the pseudo-first-order kinetic model. The maximum MC-LR degradation rate of 99.98% can be obtained within 5 h under the following optimum conditions: pH of 5.01, Ag3PO4 concentration of 26.67 g/L, and MC-LR concentration of 9.06 mg/L. Nine intermediates were detected and analyzed by LC/MS. Three main degradation pathways were proposed based on the molecular weight of the intermediates and the reaction mechanism: (1) hydroxylation on the aromatic ring of Adda, (2) hydroxylation on the diene bonds of Adda, and (3) internal interactions on the cyclic structure of MC-LR. CONCLUSION: Ag3PO4 is a highly efficient catalyst for MC-LR degradation in aqueous solutions.

Performance of hybrid vertical up- and downflow subsurface flow constructed wetlands in treating synthetic high-strength wastewater.

The performance and temporal variation of hybrid vertical-subsurface flow constructed wetlands (VFCWs) in response to two-stage combinations of vertical upflow (VUF) and vertical downflow (VDF) were analyzed in this research. The results of high carbon (C) treatment and high nitrogen (N) treatment were similar. The Lythrum salicaria treatment showed higher removal efficiency than CWs planted with Acorus calamus. Under high C- and N-loading treatments, the optimum two-stage combination was VDF-VUF VFCWs planted with A. calamus. Furthermore, the highest nutrient removal efficiencies were achieved in late summer (July and August) and early autumn (September). The chemical oxygen demand and total nitrogen removal efficiencies were significantly affected (P < 0.05) by season, system, and wetland plant.

Kinetic and mechanistic study of microcystin-LR degradation by nitrous acid under ultraviolet irradiation.

Degradation of microcystin-LR (MC-LR) in the presence of nitrous acid (HNO(2)) under irradiation of 365nm ultraviolet (UV) was studied for the first time. The influence of initial conditions including pH value, NaNO(2) concentration, MC-LR concentration and UV intensity were studied. MC-LR was degraded in the presence of HNO(2); enhanced degradation of MC-LR was observed with 365nm UV irradiation, caused by the generation of hydroxyl radicals through the photolysis of HNO(2). The degradation processes of MC-LR could well fit the pseudo-first-order kinetics. Mass spectrometry was applied for identification of the byproducts and the analysis of degradation mechanisms. Major degradation pathways were proposed according to the results of LC-MS analysis. The degradation of MC-LR was initiated via three major pathways: attack of hydroxyl radicals on the conjugated carbon double bonds of Adda, attack of hydroxyl radicals on the benzene ring of Adda, and attack of nitrosonium ion on the benzene ring of Adda.

A sustainable landscape ecosystem design: a case study.

Landscape planning is clearly ecologically and socially relevant. Concern about sustainability between human and environment is now a driving paradigm for this professional. However, the explosion of the sustainable landscape in China is a very recent phenomenon. What is the sustainable landscape? How is this realized in practice? In this article, on the basis of the reviews of history and perplexities of Chinese landscape and nature analysis of sustainable landscape, the ecothinking model, an implemental tool for sustainable landscape, was developed, which applies ecothinking in vision, culture, conservation and development of site, and the process of public participation for a harmonious relationship between human and environment. And a case study of the south entrance of TongNiuling Scenic Area was carried out, in which the most optimum scenario was chosen from among three models according to the ecothinking model, to illustrate the construction of the ecothinking model and how to achieve a sustainable landscape.

Asymmetric tandem Michael addition-ylide olefination reaction for the synthesis of optically active cyclohexa-1,3-diene derivatives.

The reaction of a crotonate-derived chiral phosphonium salt with alpha,beta-unsaturated carbonyl compounds in the presence of Cs(2)CO(3) affords optically active cyclohexa-1,3-diene derivatives with up to 90% ee in good yields.