Tb^(3+)-nucleic acid probe-based label-free and rapid detection of mercury pollution in food

Mercury is a threatening pollutant in food,herein,we developed a Tb^(3+)-nucleic acid probe-based label-free assay for mix-and-read,rapid detection of mercury pollution.The assay utilized the feature of light-up fluorescence of terbium ions(Tb^(3+))via binding with single-strand DNA.Mercury ion,Hg^(2+)induced thymine(T)-rich DNA strand to form a double-strand structure(T-Hg^(2+)-T),thus leading to fluorescence reduction.Based on the principle,Hg^(2+)can be quantified based on the fluorescence of Tb^(3+),the limit of detection was 0.0689μmol/L and the linear range was 0.1-6.0μmol/L.Due to the specificity of T-Hg^(2+)-T artificial base pair,the assay could distinguish Hg^(2+)from other metal ions.The recovery rate was ranged in 98.71%-101.34%for detecting mercury pollution in three food samples.The assay is low-cost,separation-free and mix-to-read,thus was a competitive tool for detection of mercury pollution to ensure food safety.

Introductory remarks on mercury pollution in China

China is rich in mercury resources. Mercury and its compounds are quite widely used in China causing pollution in aquatic sediment/soil and atmospheric environment. The general status of mercury pollution in China is briefed. Research achievement on some aquatic ecosystems are reported and some pollution problems need to be urgently studied are suggested.

Mercury pollution and control in China

Before 1970s the Second Songhua River and Ji Canal of China had been polluted seriously by mercury. During peak pollution period, mercury levels in water, sediment and fish body of these rivers were close to or even higher than that of famous Minamata Bay of Japan. Some residents who live near to the polluted rivers were affected and the methyl mercury values in their blood, hair and urine were higher than normal people obviously . Since the fish had decreased even vanished in these rivers, so the food chain that transfers mercury to human also was out off almostly. However, nervous symptoms of Minamata disease were discovered among fisherman who had eaten more fishes. This report relates the stories about the mercury pollution of the Second Songhua River and Ji Canal.

Effects of atmospheric mercury pollution on terrestrial ecosystem in Chongqing, China

The results from investigations indicated that mercury pollution in terrestrial ecosystem was serious due to the anthropogenic mercury emission growing in Chongqing, China. The concentration of atmospheric mercury in Chongqing was 34.4±2.7 ng/m\+3 with the range of 9.2—101.5. The accumulation of mercury in surface soil was increasing with time. The mercury content of some agricultural products have exceeded the food health standard value, especially near the mercury emission sources. The mercury accumulation in soil plant system was affected by atmospheric mercury and a positive correlation between them was found. Volatilization of mercury was the most important processes with which soil mercury joined the global mercury recycling.

Evaluation of the Level of Mercury Pollution in the Sediments of the Rivers Draining the Gold Panning Sites in the Territory of Fizi, Eastern Democratic Republic of Congo

The sediments collected respectively from the Etó, Kacumvi, Kimbi, Lubichako, Makungu, Kuwa, Mandje, Misisi and Kimuti Rivers draining the gold panning sites in the Fizi territory were studied during a 16-month cycle (August and December 2016 to August and December 2017) in order to assess their degree of mercury pollution in the dry season as well as in the rainy season. The assessment of the degree of pollution of the said sediments focused on six parameters including the total mercury content (THg) and the indices of mercury pollution such as the mercury enrichment factor (EF), the mercury contamination factor (CF), the mercury geoaccumulation index (Igeo), the mercury potential ecological risk factor (PERF) and the mercury ecological risk index (ERI). Total mercury was determined by atomic absorption spectrophotometry (AAS) while the mercury pollution indices were successively calculated using the appropriate formulas. The results thus obtained revealed that all the sediments of the rivers studied are considerably polluted by mercury according to the values relative to their total mercury content and mercury pollution indices, including the mercury enrichment factor (EF), the mercury contamination factor (CF), the mercury geoaccumulation index (Igeo), the mercury potential ecological risk factor (PERF) and the mercury ecological risk index (ERI), which greatly exceed the standards recommended by the Canadian Council of Ministers of the Environment. In particular, the sediments of the Kimbi River are highly polluted by mercury compared to those of other rivers studied. This reported pollution is the result of anthropogenic gold panning activities that generate effluents and elemental mercury that pollute the streams.

Feasibility Evaluation of Using Biochar-based Permeable Reactive Barrier for the Remediation of Mercury and Arsenic Composite Polluted Water Bodies

This study employed a modified biochar material to construct a permeable reactive barrier(PRB)for the treatment of water bodies polluted with mercury and arsenic.The experimental results demonstrated that the addition of goethite-modified biochar significantly enhanced the remediation efficiency of As(III),achieving a maximum removal rate of 100%.Conversely,pure biochar exhibited high efficiency in the removal of Hg(II),with a maximum removal rate approaching 100%.Furthermore,the pH level of the water significantly influenced the adsorption efficiency of heavy metal ions,with the optimal removal performance observed at a pH of 6.0.The PRB system demonstrated excellent removal rates under low concentrations of heavy metals.However,as the concentration increased,the remediation efficiency exhibited a slight decrease.In summary,the findings of this study provide compelling evidence for the use of modified biochar in the construction of PRBs for the remediation of mercury and arsenic-polluted water bodies.Furthermore,the study reveals the mechanism by which pH and heavy metal concentration influence remediation efficiency.

Rapid field testing of mercury pollution by designed fluorescent biosensor and its cells-alginate hydrogel-based paper assay

With increasing industrial activities,mercury has been largely discharged into environment and caused serious environmental problems.The growing level of mercury pollution has become a huge threat to human health due to its significant biotoxicity.Therefore,the simple and fast means for on-site monitoring discharged mercury pollution are highly necessary to protect human beings from its pernicious effects in time.Herein,a"turn off"fluorescent biosensor(mCherry L199 C)for sensing Hg2+was successfully designed based on direct modification of the chromophore environment of fluorescent protein mCherry.For rapid screening and characterization,the designed variant of mCherry(mCherry L199 C)was directly expressed on outer-membrane of Escherichia coli cells by cell surface display technique.The fluorescent biosensor was characterized to have favorable response to Hg2+at micromole level among other metal ions and over a broad pH range.Further,the cells of the fluorescent biosensor were encapsulated in alginate hydrogel to develop the cells-alginate hydrogel-based paper.The cells-alginate hydrogel-based paper could detect mercury pollution in 5 min with simple operation process and inexpensive equipment,and it could keep fluorescence and activity stable at 4℃ for 24 hr,which would be a high-throughput screening tool in preliminarily reporting the presence of mercury pollution in natural setting.

Mercury emission and pollution in Chongqing City, China

Investigation showed that mercury emission in Chongqing City, China is about 2.1 t/a, 70% of which came from coal burning.Mercury in many water bodies have been detected, in vegetables and milk had exceeded the food standard value in some places.

Expression of c-fos and oxidative stress on brain of rats reared on food from mercury-selenium coexisting mining area

Wanshan mercury mine is the largest mercury deposit in Guizhou Province of China, but there were few reports on mercury toxic＂ effect in the mining area. In order to study the neurotoxicity of food from Wanshan mercury mine area and probe into the effect of food from Wanshan mercury miner area on the changes of brain oxidative damage and expression of c-fos gene. The rats were exposed to mercury contaminated food for 20 d. The content of malondialdehyde （MDA）, superoxide dismutase （SOD）, GSH-peroxidase （GSH-px） and Glutathione （GSH） in rat brain was measured, and the effect of mercury contaminated rice on the expression of c-los mRNA in rat brain and the expression of c-FOS protein in cortex, hippocampus were observed using reverse transcription polymerase chain reaction （RT-PCR） and immunocytochemical methods. The results showed the levels of GSH, MDA, SOD and of GSH-dependent enzymes in the rat brain changed between exposure groups and control group; The mercury polluted rice induced significantly the expression of c-los mRNA; the c-FOS positive cells in hippocampus and cortex of exposure groups were significant different from control group （P〈0.01）. It could be concluded that oxidative stress signals could contribute to the induction of immediate early genes （IEGs）; free radicals and their by-products might not only cause oxidative damage, but also influenced gene expression; IEGs c-fos participated in the toxicity process of brain injury by mercury polluted food.

Estimating leaf mercury content in Phragmites australis based on leaf hyperspectral reflectance

Introduction:Highmercury(Hg)concentrations affect the chlorophyll in leaves,therebymodifying leaf spectra.Hyperspectra is a promising technique for the rapid,nondestructive evaluation of leaf Hg content.In this study,we investigated Hg contents and reflective hyperspectra of reed leaves(Phragmites communis)in a gold mining(Jilin province,China).Spectral parameters sensitive to Hg content were identified through basic spectral transformations,continuous wavelet transformation(CWT),and spectral indices techniques.Leaf Hg inversion models were developed using stepwise multiple linear regression,partial least squares regression,and random forest algorithms.Outcomes:The results indicated that:1)leaf Hg content decreased with increasing distance from the mine:Jiapigou(JPG)>Erdaocha(EDC)>Laojingchang(LJC)>Erdaogou(EDG)>Lingqian(LQ)>Weishahe(WSH).2)Hg–sensitive wavelengths were primarily in the visible region;CWT increased the correlation between hyperspectral data and leaf Hg content,and improved the regression and accuracy of inversion;3)the continuumremoval–CWT–stepwise multiple linear regression was better for estimating low leaf Hg content;while the differential spectral index–partial least squares regression was better for estimating high leaf Hg content.Conclusion:These hyperspectral inversion methods could be used for rapid,nondestructive monitoring of wetland plants.

Remediation effect of compost on soluble mercury transfer in a crop of Phaseolus vulgaris

We studied the dynamics of mercury（Hg） transfer in Phaseolus vulgaris plants grown in soil with Hg-doped compost at the maximum levels permitted by Colombian law on organic amendments. Quantitative evaluation of transfer was made in different plant organs： roots,stem, leaves, pods and seeds. Matrix effect was determined in doped soil assays, using soil with and without addition of compost. Results showed that the use of organic matter reduced Hg transfer to the plant and the amount transferred was differentially distributed to the organs. We observed an inverse relationship between concentration and distance from the body to the root. It was evident that transfer was mediated by quantitative factors;the greater the presence of mercury in soil, the larger the amount that will be transferred.Results also indicate the remedial effect of compost and the presence of a barrier, at the root level, against mercury translocation to the plant aerial parts.