Degradation of extracellular genomic,plasmid DNA and specific antibiotic resistance genes by chlorination

Extracellular DNA structure damaged by chlorination was characterized. Integrity of extracellular ARG genetic information after chlorination was determined. Typical chlorine doses will likely effectively diminish extracellular DNA and ARGs. Plasmid DNA/ARGs were less readily broken down than genomic DNA. The Bioanalyzer methodology effectively documented damage incurred to DNA. There is a need to improve understanding of the effect of chlorine disinfection on antibiotic resistance genes (ARGs) in order to advance relevant drinking water, wastewater, and reuse treatments. However, few studies have explicitly assessed the physical effects on the DNA. Here we examined the effects of free chlorine (1–20 mg Cl₂/L) on extracellular genomic, plasmid DNA and select ARGs. Chlorination was found to decrease the fluorometric signal of extracellular genomic and plasmid DNA (ranging from 0.005 to 0.05 mg/mL) by 70%, relative to a no-chlorine control. Resulting DNA was further subject to a fragment analysis using a Bioanalyzer, indicating that chlorination resulted in fragmentation. Moreover, chlorine also effectively deactivated both chromosomal- and plasmid-borne ARGs, mecA and tetA, respectively. For concentrations >2 mg Cl₂//L × 30 min, chlorine efficiently reduced the qPCR signal when the initial concentration of ARGs was 10⁵ copies/mL or less. Notably, genomic DNA and mecA gene signals were more readily reduced by chlorine than the plasmid-borne tetA gene (by ~2 fold). Based on the results of qPCR with short (~200 bps) and long amplicons (~1200 bps), chlorination could destroy the integrity of ARGs, which likely reduces the possibility of natural transformation. Overall, our findings strongly illustrate that chlorination could be an effective method for inactivating extracellular chromosomal- and plasmid-borne DNA and ARGs.     

The role of lipids in fermentative propionate production from the co-fermentation of lipid and food waste

● Lipid can promote PA production on a target from food waste. ● PA productivity reached 6.23 g/(L∙d) from co-fermentation of lipid and food waste. ● Lipid promoted the hydrolysis and utilization of protein in food waste. ● Prevotella , Veillonella and norank _f _Propioni bacteriaceae were enriched. ● Main pathway of PA production was the succinate pathway. Food waste (FW) is a promising renewable low-cost biomass substrate for enhancing the economic feasibility of fermentative propionate production. Although lipids, a common component of food waste, can be used as a carbon source to enhance the production of volatile fatty acids (VFAs) during co-fermentation, few studies have evaluated the potential for directional propionate production from the co-fermentation of lipids and FW. In this study, co-fermentation experiments were conducted using different combinations of lipids and FW for VFA production. The contributions of lipids and FW to propionate production, hydrolysis of substrates, and microbial composition during co-fermentation were evaluated. The results revealed that lipids shifted the fermentation type of FW from butyric to propionic acid fermentation. Based on the estimated propionate production kinetic parameters, the maximum propionate productivity increased significantly with an increase in lipid content, reaching 6.23 g propionate/(L∙d) at a lipid content of 50%. Propionate-producing bacteria Prevotella, Veillonella, and norank_f_Propionibacteriaceae were enriched in the presence of lipids, and the succinate pathway was identified as a prominent fermentation route for propionate production. Moreover, the Kyoto Encyclopedia of Genes and Genomes functional annotation revealed that the expression of functional genes associated with amino acid metabolism was enhanced by the presence of lipids. Collectively, these findings will contribute to gaining a better understanding of targeted propionate production from FW.     

Treatment,residual chlorine and season as factors affecting variability of trihalomethanes in small drinking water systems

Seasonal variability in source water can lead to challenges for drinking water providers related to operational optimization and process control in treatment facilities. The objective of this study is to investigate seasonal variability of water quality in municipal small water systems (<3000 residents) supplied by surface waters. Residual chlorine and trihalomethanes (THM) were measured over seven years (2003–2009). Comparisons are made within each system over time, as well as between systems according to the type of their treatment technologies. THM concentrations are generally higher in the summer and autumn. The seasonal variability was generally more pronounced in systems using chlorination plus additional treatment. Chloroform, total THM (TTHM) and residual chlorine concentrations were generally lower in systems using chlorination plus additional treatment. Conversely, brominated THM concentrations were higher in systems using additional treatment. Residual chlorine was highest in the winter and lowest in the spring and summer. Seasonal variations were most pronounced for residual chlorine in systems with additional treatment. There was generally poor correlation between THM concentrations and concentrations of residual chlorine. Further study with these data will be beneficial in finding determinants and indicators for both quantity and variability of disinfection byproducts and other water quality parameters.     

Effect of Pollution On the Occurrence, Distribution and Sulphur Transformation Ability of the Thiobacilli in the River Ganga

The occurrence, distribution and nature of ambient thiobacilli along with their ability to oxidize different sulphur species under simulated natural and in vitro culture conditions were studied in the polluted and unpolluted sites of the River Ganga.

Thiobacillus thioparus, T. thiooxidans and T. denitrificans were isolated from the river water. the former two occurred in both polluted and unpolluted sites, while T. denitrificans occurred in polluted areas only. the paper pulp mill effluent discharge area contained the highest population of T. thioparus. the sewage drainage area showed relatively higher populations of T. thiooxidans and T. denitrificans.

The present study revealed that only biological oxidation of either thiosulphate or elemental sulphur occurred in the river water. All the thiobacilli screened oxidized thiosulphate, and three-fourths of them oxidized elemental sulphur. Some strains were found to be very good acidifiers. in spite of such acidification by the ambient thiobacilli, the pH of the river water remained alkaline. the specific rates of thiosulphate (0.18 -0.51 μMmolh^-1 mg^-1 cell) and sulphur (1.3 - 6.2 Normality day^-1 mg^-1 biomass) oxidations under simulated natural condition were found to be higher in polluted areas when compared with the unpolluted one (sulphur: 0.8 - 1.0 Normality day^-1 mg^-1).

Further, addition of thiouslphate or elemental sulphur in the river water in simulated in vitro condition resulted in the increase of respective oxidation rates. the variations in the natae of pollutants discharged into the river water influenced the oxidation rate of thiosulphate or sulphur.     

Effect of ultra-sonication and its use with sodium hypochlorite as antifouling method against <Emphasis Type="Italic">Mytilus edulis</Emphasis> larvae and mussel

Biofouling is a stubborn problem in cooling systems where using raw water from lakes, rivers, and sea. The effect of ultrasound and its sequential application with sodium hypochlorite (chlorination) upon marine bivalve Mytilus edulis (blue mussel), a massive fouling organism, has been studied and discussed here. The results obtained from the work carried out have shown that 42 kHz ultrasound is better than 28 kHz in accordance with veliger larvae mortality. The 42 kHz ultrasound has enhanced the mortality rate of veliger larvae than only free-residual chlorination up to 99%. On the other side, the 14-mm size mussel was less resistance than 25-mm size mussel to 42 kHz ultrasonication, among the studied two sizes (14 and 25 mm) of the blue mussel. Lethal time (100%) have decreased by 1–12% used for the sequential action of 42 kHz ultrasonic followed by free-residual chlorination compare with only free-residual chlorination treatment. The obtained results are put forward that the application of ultra-sonication before chlorination can reduce the mussel extinct time up to 12%. Obviously, this result will provide a possible use of ultra-sonication with famous chlorination antifouling treatment and eventually can decrease the chlorine exposure time and dose. It could discharge low chlorine by-products that may provide an environment friendly way.     

Effects of rape straw and red mud on extractability and bioavailability of cadmium in a calcareous soil

Screening of cost-effective soil amendments is important to develop “in situ” remediation techniques for cadmium (Cd) contaminated soils. In this study, different soil amendments, including red mud, a by-product of the alumina industry, and acid-treated, nano-treated by nano-particle milling, nano and acid-treated red muds, zeolite, corn straw, and rape straw, were evaluated to immobilize Cd in two added levels (2 and 5 mg Cd·kg^-1 soil) in a calcareous soil by single and sequential extractions and by cucumber (Cucumis sativus L.) pot experiments. Results indicated that cruciferous rape straw significantly decreased the concentrations of water soluble, extractable Cd in soils, and Cd in cucumber plants, and it was more effective than gramineous corn straw. Also, red mud generally decreased the extractability and bioavailability of Cd added to calcareous soils more effectively than zeolite. Furthermore, the efficiency of red mud could be increased by the treatment of nano-particle milling due to the increase in specific surface area of red mud. It is potential to use rape straw and red mud as soil amendments to develop a cost-effective and efficient “in situ” remediation technology for Cd mildly contaminated calcareous soils.     

Identification of important precursors and theoretical toxicity evaluation of byproducts driving cytotoxicity and genotoxicity in chlorination

• NOM formed more C-DBPs while amino acids formed more N-DBPs during chlorination • Aspartic acid and asparagine showed the highest toxicity index during chlorination • Dichloroacetonitrile might be a driving DBP for cytotoxicity and genotoxicity • Dichloroacetonitrile dominated the toxicity under different chlorination conditions Chlorination, the most widely used disinfection process for water treatment, is unfortunately always accompanied with the formation of hazardous disinfection byproducts (DBPs). Various organic matter species, like natural organic matter (NOM) and amino acids, can serve as precursors of DBPs during chlorination but it is not clear what types of organic matter have higher potential risks. Although regulation of DBPs such as trihalomethanes has received much attention, further investigation of the DBPs driving toxicity is required. This study aimed to identify the important precursors of chlorination by measuring DBP formation from NOM and amino acids, and to determine the main DBPs driving toxicity using a theoretical toxicity evaluation of contributions to the cytotoxicity index (CTI) and genotoxicity index (GTI). The results showed that NOM mainly formed carbonaceous DBPs (C-DBPs), such as trichloromethane, while amino acids mainly formed nitrogenous DBPs (N-DBPs), such as dichloroacetonitrile (DCAN). Among the DBPs, DCAN had the largest contribution to the toxicity index and might be the main driver of toxicity. Among the precursors, aspartic acid and asparagine gave the highest DCAN concentration (200 g/L) and the highest CTI and GTI. Therefore, aspartic acid and asparagine are important precursors for toxicity and their concentrations should be reduced as much as possible before chlorination to minimize the formation of DBPs. During chlorination of NOM, tryptophan, and asparagine solutions with different chlorine doses and reaction times, changes in the CTI and GTI were consistent with changes in the DCAN concentration.     

Formation of disinfection by-products during sodium hypochlorite cleaning of fouled membranes from membrane bioreactors

•HAAs was dominant among the DBPs of interest. •Rising time, dose, temperature and pH raised TCM and HAAs but reduced HANs and HKs. •Low time, dose and temperature and non-neutrality pH reduced toxic risks of DBPs. •The presence of EPS decelerated the production of DBPs. •EPS, particularly polysaccharides were highly resistant to chlorine. Periodic chemical cleaning with sodium hypochlorite (NaClO) is essential to restore the membrane permeability in a membrane bioreactor (MBR). However, the chlorination of membrane foulants results in the formation of disinfection by-products (DBPs), which will cause the deterioration of the MBR effluent and increase the antibiotic resistance in bacteria in the MBR tank. In this study, the formation of 14 DBPs during chemical cleaning of fouled MBR membrane modules was investigated. Together with the effects of biofilm extracellular polymeric substances (EPS), influences of reaction time, NaClO dosage, initial pH, and cleaning temperature on the DBP formation were investigated. Haloacetic acids (HAAs) and trichloromethane (TCM), composed over 90% of the DBPs, were increasingly accumulated as the NaClO cleaning time extended. By increasing the chlorine dosage, temperature, and pH, the yield of TCM and dichloroacetic acid (DCAA) was increased by up to a factor of 1‒14, whereas the yields of haloacetonitriles (HANs) and haloketones (HKs) were decreased. Either decreasing in the chlorine dosage and cleaning temperature or adjusting the pH of cleaning reagents toward acidic or alkaline could effectively reduce the toxic risks caused by DBPs. After the EPS extraction pretreatment, the formation of DBPs was accelerated in the first 12 h due to the damage of biofilm structure. Confocal laser scanning microscopy (CLSM) images showed that EPS, particularly polysaccharides, were highly resistant to chlorine and might be able to protect the cells exposed to chlorination.     

Effect of the ultraviolet/chlorine process on microbial community structure,typical pathogens,and antibiotic resistance genes in reclaimed water

• UV/chlorine can effectively remove VBNC pathogens, ARGs and MGEs in reclaimed water. • Microbial community was changed with reduced diversity during UV/chlorine process. • CRBs-carried MGEswere the predominant groups during UV/chlorine process. • No direct co-selection strategy was shared between UV/chlorine and resistome. Urban wastewater contains a wide range of pathogens and antibiotic resistance genes (ARGs), which are a serious concern if reusing treated wastewater. However, few studies have explored the microbial communities in reclaimed water using ultraviolet (UV)/chlorine treatment and assessed the changes of the resistome. This study investigated the occurrence of typical pathogens, ARGs, and bacterial communities in UV/chlorine-treated reclaimed water samples. The numbers of culturable and viable but non-culturable pathogens were effectively reduced to 0 CFU/mL within 1–10 and 10–30 min after UV/chlorine treatment, respectively. Meanwhile, the physicochemical indices of water quality were not affected. UV/chlorine treatment could significantly change the bacterial community structure of reclaimed water, showing a decrease in bacterial abundance and diversity. Chlorine-resistant Acinetobacter and Mycobacterium were the dominant bacterial genera (>50%) after UV/chlorine treatment. Moreover, the number of ARGs and mobile genetic elements (MGEs) decreased with an increase in UV/chlorine exposure. However, eight ARGs and three MGEs were consistently detected in more than three seasons, making these major concerns because of their potential role in the persistence and dissemination of antibiotic resistance. Overall, the results of this study suggest that UV/chlorine treatment can potentially improve the microbiological safety of reclaimed water. And more attention should be paid to the pathogens that are both chlorine-resistant and carry MGEs because of their potential for resistance transmission.     

Comparative genotoxicity of water processed by three drinking water treatment plants with different water treatment procedures

• Genotoxicity of substances is unknown in the water after treatment processes. • Genotoxicity decreased by activated carbon treatment but increased by chlorination. • Halogenated hydrocarbons and aromatic compounds contribute to genotoxicity. • Genotoxicity was assessed by umu test; acute and chronic toxicity by ECOSAR. • Inconsistent results confirmed that genotoxicity cannot be assessed by ECOSAR. Advanced water treatment is commonly used to remove micropollutants such as pesticides, endocrine disrupting chemicals, and disinfection byproducts in modern drinking water treatment plants. However, little attention has been paid to the changes in the genotoxicity of substances remaining in the water following the different water treatment processes. In this study, samples were collected from three drinking water treatment plants with different treatment processes. The treated water from each process was analyzed and compared for genotoxicity and the formation of organic compounds. The genotoxicity was evaluated by an umu test, and the acute and chronic toxicity was analyzed through Ecological Structure- Activity Relationship (ECOSAR). The results of the umu test indicated that biological activated carbon reduced the genotoxicity by 38%, 77%, and 46% in the three drinking water treatment plants, respectively, while chlorination increased the genotoxicity. Gas chromatograph-mass spectrometry analysis revealed that halogenated hydrocarbons and aromatic compounds were major contributors to genotoxicity. The results of ECOSAR were not consistent with those of the umu test. Therefore, we conclude that genotoxicity cannot be determined using ECOSAR .     

Reaction of ortho-methoxybenzoic acid with the water disinfecting agents ozone, chlorine and sodium hypochlorite

Ozone, chlorine and sodium hypochlorite are commonly used as disinfecting agents for drinking water production. The reaction pathways of ozonation and chlorination of o-methoxybenzoic acid in aqueous solution were studied using gas chromatography-mass spectrometry (GC-MS) and high pressure liquid chromatography (HPLC). The results show that less than 1% of o-methoxybenzoic acid remains in reaction. The final major products using ozone oxidation are oxalic and glyoxalic acids. Phenols appear only at insufficient ozone levels. Sodium hypochlorite leads to higher levels of primary products. Molecular chlorine leads to the formation of higher amounts of polychlorinated derivatives. Model experiments allow to propose schemes of o-methoxybenzoic acid transformation under the conditions simulating water treatment processes.     

Remediation of soil and groundwater contaminated with organic chemicals using stabilized nanoparticles: Lessons from the past two decades

▪ Overviewed evolution and environmental applications of stabilized nanoparticles. ▪ Reviewed theories on particle stabilization for enhanced reactivity/deliverability. ▪ Examined various in situ remediation technologies based on stabilized nanoparticles. ▪ Summarized knowledge on transport of stabilized nanoparticles in porous media. ▪ Identified key knowledge gaps and future research needs on stabilized nanoparticles. Due to improved soil deliverability and high reactivity, stabilized nanoparticles have been studied for nearly two decades for in situ remediation of soil and groundwater contaminated with organic pollutants. While large amounts of bench- and field-scale experimental data have demonstrated the potential of the innovative technology, extensive research results have also unveiled various merits and constraints associated different soil characteristics, types of nanoparticles and particle stabilization techniques. Overall, this work aims to critically overview the fundamental principles on particle stabilization, and the evolution and some recent developments of stabilized nanoparticles for degradation of organic contaminants in soil and groundwater. The specific objectives are to: 1) overview fundamental mechanisms in nanoparticle stabilization; 2) summarize key applications of stabilized nanoparticles for in situ remediation of soil and groundwater contaminated by legacy and emerging organic chemicals; 3) update the latest knowledge on the transport and fate of stabilized nanoparticles; 4) examine the merits and constraints of stabilized nanoparticles in environmental remediation applications; and 5) identify the knowledge gaps and future research needs pertaining to stabilized nanoparticles for remediation of contaminated soil and groundwater. Per instructions of this invited special issue, this review is focused on contributions from our group (one of the pioneers in the subject field), which, however, is supplemented by important relevant works by others. The knowledge gained is expected to further advance the science and technology in the environmental applications of stabilized nanoparticles.     

Persistence of polychlorinated biphenyls in marine bivalves

Bivalves (Cerastoderma edule and Macoma balthica) which had previously been exposed to Aroclors^® 1242, 1254 and 1260 were able to reduce their tissue burdens of chlorobiphenyls with 2 to 5 chlorine atoms in short-term static assay systems. Elimination rates decreased with increasing chlorination and removal of isomers with more than 5 chlorine atoms was not recorded. Position, in addition to the number, of chlorine atoms influenced the persistence of chlorobiphenyls. Isomers with most ortho-substituted chlorine atoms were least persistent. Experiments with single isomers indicated variation in the elimination of low chlorinated isomers between bivalve species. These biological and chemical influences on tissue residues, together with environmental parameters such as temperature and suspended solids, are considered in relation to the use of bivalves as bio-indicators of marine pollution.     

Biofiltration and disinfection codetermine the bacterial antibiotic resistome in drinking water: A review and meta-analysis

• Published data was used to analyze the fate of ARGs in water treatment. • Biomass removal leads to the reduction in absolute abundance of ARGs. • Mechanism that filter biofilm maintain ARB/ARGs was summarized. • Potential BAR risks caused by biofiltration and chlorination were proposed. The bacterial antibiotic resistome (BAR) is one of the most serious contemporary medical challenges. The BAR problem in drinking water is receiving growing attention. In this study, we focused on the distribution, changes, and health risks of the BAR throughout the drinking water treatment system. We extracted the antibiotic resistance gene (ARG) data from recent publications and analyzed ARG profiles based on diversity, absolute abundance, and relative abundance. The absolute abundance of ARG was found to decrease with water treatment processes and was positively correlated with the abundance of 16S rRNA (r² = 0.963, p<0.001), indicating that the reduction of ARG concentration was accompanied by decreasing biomass. Among treatment processes, biofiltration and chlorination were discovered to play important roles in shaping the bacterial antibiotic resistome. Chlorination exhibited positive effects in controlling the diversity of ARG, while biofiltration, especially granular activated carbon filtration, increased the diversity of ARG. Both biofiltration and chlorination altered the structure of the resistome by affecting relative ARG abundance. In addition, we analyzed the mechanism behind the impact of biofiltration and chlorination on the bacterial antibiotic resistome. By intercepting influent ARG-carrying bacteria, biofilters can enrich various ARGs and maintain ARGs in biofilm. Chlorination further selects bacteria co-resistant to chlorine and antibiotics. Finally, we proposed the BAR health risks caused by biofiltration and chlorination in water treatment. To reduce potential BAR risk in drinking water, membrane filtration technology and water boiling are recommended at the point of use.     

Cooling water chlorination and productivity of entrained phytoplankton

A study to determine the effects of various concentrations of chlorine on the productivity of entrained marine phytoplankton was carried out at a nuclear power station on northeastern Long Island Sound, USA. Chlorine is a biocide used to control the growth of marine fouling organisms on the walls of many power station cooling systems. Chlorine concentrations considerably below those required to eliminate fouling organisms produced large decreases in the productivity of entrained phytoplankton. Generally, between 0.25 and 0.75 ppm residual chlorine at the cooling water discharge, continuously applied, is required to eliminate fouling organisms. At the highest chlorine concentration tested, 0.4 ppm residual at discharge (addition of chlorine at 1.2 ppm at cooling water intake), there was an 83% decrease in productivity as compared with the productivity at the intake. Productivity measurements were made at 6 other continuously applied chlorine concentrations. At the lowest concentration tested, too low to measure with our analytical method (addition of chlorine at 0.1 ppm at the intake), we measured a production decrease of 79%. Thus, a decrease in chlorination dosage of over an order of magnitude produced essentially no reduction in the damage done to entrained phytoplankton. Application of chlorine intermittently produced somewhat less of a decrease in primary productivity. When there was no chlorine addition during the period of study, there was essentially no effect on productivity. These data indicate that chlorine cannot be used effectively as a biocide for fouling organisms without having adverse effects on entrained phytoplankton.Contribution No. 2838 of the Woods Hole Oceanographic Institution.     

The Nature of Biodegradation of Vegetation in Mangrove Ecosystem

Experiments were carried out in situ and in the laboratory for 45 and 90 day periods respectively to study the nature and process of biodegradation of leaves/cladodes of 9 species of halophytes with special reference to mangrove vegetation. The leaching rate of chlorophylls a, b, bacteriochlorophylls a, c, d, phaeopigments, organic carbon and micronutrients such as Zinc, Copper. Iron and Manganese were studied at different intervals (10, 30, 90 days) and in varying salinity media (0.30, 16.60, 33.30%_°S). The organisms involved in fragmentation, decomposition and biodeterioration have been listed. Total litter production in the wooded mangrove area was 7,457.07 tonnes/year (leaf litter alone 5,834.4 tonnes/year). The mangroves export substantial organic material to the neighbouring estuarine and sea waters and the values were estimated at 261 tonnes C/year and 1,566 tonnes C/year respectively. Only 783 tonnes C/year were utilised and retained for use within the mangrove ecosystem.     

Whole pictures of halogenated disinfection byproducts in tap water from China’s cities

When bromide/iodide is present in source water, hypobromous acid/hypoiodous acid will be formed with addition of chlorine, chloramine, or other disinfectants. Hypobromous acid/hypoiodous acid undergoes reactions with natural organic matter in source water to form numerous brominated/iodinated disinfection byproducts (DBPs). In this study, tap water samples were collected from eight cities in China. With the aid of electrospray ionization-triple quadrupole mass spectrometry by setting precursor ion scans of m/z 35, m/z 81, and m/z 126.9, whole pictures of polar chlorinated, brominated, and iodinated DBPs in the tap water samples were revealed for the first time. Numerous polar halogenated DBPs were detected, including haloacetic acids, newly identified halogenated phenols, and many new/unknown halogenated compounds. Total organic chlorine, total organic bromine, and total organic iodine were also measured to indicate the total levels of all chlorinated, brominated, and iodinated DBPs in the tap water samples. The total organic chlorine concentrations ranged from 26.8 to 194.0 μg·L^–1 as Cl, with an average of 109.2 μg·L^–1 as Cl; the total organic bromine concentrations ranged from below detection limit to 113.3 μg·L^–1 as Br, with an average of 34.7 μg·L^–1 as Br; the total organic iodine concentrations ranged from below detection limit to 16.4 μg·L^–1 as I, with an average of 9.1 μg·L^–1 as I; the total organic halogen concentrations ranged from 31.3 to 220.4 μg·L^–1 as Cl, with an average of 127.2 μg·L^–1 as Cl.     

Microbial responses to the use of NaClO in sediment treatment

• Chlorine addition enhanced the release of TOC, TN from the sediment. • Chlorine has a long-term negative effect on microbial richness. • Usually enzymes lose activity, and expression of genes was downregulated. • Carbon degradation and nitrification might be strongly inhibited. Chlorine is often used in algal removal and deodorization of landscape waters, and occasionally used as an emergency treatment of heavily polluted sediments. However, the ecological impact of this practice has not been fully studied and recognized. In this study, NaClO at 0.1 mmol/g based on dry weight sediment was evenly mixed into the polluted sediment, and then the sediment was incubated for 150 days to evaluate its microbial effect. Results showed that NaClO addition enhanced the release of TOC, TN, Cr and Cu from the sediment. The microbial richness in the examined sediment decreased continuously, and the Chao1 index declined from 4241 to 2731, in 150 days. The microbial community composition was also changed. The abundance of Proteobacteria and Bacteroidetes increased to 54.8% and 4.2% within 7 days compared to the control, and linear discriminant analysis (LDA) showed gram-negative bacteria and aerobic bacteria enriched after chlorination. The functional prediction with PICRUSt2 showed the functions of the microbial community underwent major adjustments, and the metabolic-related functions such as carbon metabolism, including pyruvate and methane metabolisms were significantly inhibited; besides, 15 out of 22 analyzed key enzymes involved in C cycling and 6 out of 12 key enzymes or genes involved in N cycling were strongly impacted, and the enzymes and genes involved in carbon degradation and denitrification showed remarkable downregulation. It can be concluded that chlorination posed a seriously adverse effect on microbial community structure and function. This study deepens the understanding of the ecological effects of applying chlorine for environmental remediation.     

Transport of Inorganic Phosphate in the Marine Seagrass Posidonia Oceanica By 32P-Phosphate As Tracer

Uptake and loss of inorganic phosphate by Posidonia oceanica leaf tissue has been studied in in vitro experiments. Experimental data have shown that a steady state of inorganic phosphate uptake (about 40 nmol mg^-1 dry wt.) is attained after 48 hours. in particular high accumulation (over 1000-fold the natural level in sea water) and slow loss (biological half-life, 65 days) of inorganic phosphate has been evaluated. Moreover the effect of three different metabolic inhibitors (sodium monovanadate, sodium azide, 2, 4-dinitrophenol) have been tested. Results of this effect and the high degree of inorganic phosphate accumulation in leaf tissue have demonstrated that inorganic phosphate carrier is energy dependent. Furthermore, the inorganic phosphate uptake is probably influenced by bivalent cations (Ca⁺², Mg⁺²) but the mechanism is still uncertain.

Preliminary kinetic study has shown interesting results. in particular, k_m estimated value (2.8 μmol 1^-1) has demonstrated the existence of a relatively high uptake rate (V_max) at low DIP concentration while the kinetic study of inorganic phosphate loss from leaf tissues has shown a low value of the biological half life (about 60-70 days). This evidence could be significant for the existence of a complex distribution of inorganic phosphate in the leaf tissues.     

Elemental Analysis of Water and Sediments by External Beam Pixe Part 3: Axios (Vardar) River, Greece

The Axios (Vardar) River originates from the south west part of Yugoslavia, transverses Greece, and discharges into the Thermaikos bay in the north Aegean Sea.

The proton induced X-ray emission (PIXE) method with external beam was used for the elemental analysis of water and sediment samples, while measurements of water temperature, dissolved oxygen content, conductivity, pH, and the water flow were made in situ. Water samples were also analysed for total phosphates, nitrates, chlorophyll, and BOD. The data collected for a 16-month period indicate that the Axios River is polluted as far as the metal content is concerned; its primary productivity is low and it is slightly enriched during its course into the Greek territory.