A defined mesophile consortium including Acidithiobacillus ferrooxidans, Acidithiobacillus thiooxidans, and Leptospirilum ferriphilum was applied in bioleaching sediments contaminated with multiple heavy metals. Flask experiments showed that sulfur favored the acidification in the early stage while pyrite led to a great acidification potential in the later stage. An equal sulfur/pyrite ratio got the best acidification effect. Substrate utilization started with sulfur in the early stage, and then the pH decline and the community shift give rise to the utilization of pyrite. Solubilization efficiency of Zn, Cu, Mn, and Cd reached 96.1, 93.3, 92.13, and 87.65 %, respectively. Bioleaching efficiency of other elements (As, Hg, Pb) was not more than 30 %. Heavy metal solubilization was highly negatively correlated with pH variation. Logistic models were well fitted with the solubilization efficiency, which can be used to predict the bioleaching process. The dominant species in the early stage of bioleaching were A. ferrooxidans and A. thiooxidans, and the abundance of L. ferriphilum increased together with pyrite utilization and pH decline.

Forty-four indoor and outdoor dust samples were collected from e-waste workshops and were analyzed to characterize the heavy metals and brominated flame retardants (BFRs) as well as on-site human exposure. The results showed that the most abundant Polybrominated diphenyl ethers (PBDE) congener from three sites was deca-BDE, and it was penta-BDE for the other site. A significant and positive association was found between BDE-209 and decabromodiphenyl ethane (DBDPE). The high percentage of nona-BDE indicated the debromination of deca-BDE during e-waste recycling. The ratio comparison of BDE-47 to (BDE-100 + BDE-99) indicated that the outdoor dust went through more physiochemical processes. The enrichment factors for Cu and Pb were high in both the indoor and outdoor samples. Cd significantly exceeded the Chinese soil guideline grade III. The PCA results combined with the enrichment factor (EF) values suggested common sources and behaviours of Cu, Pb and Sb in the indoor dust. Co, Cr, Ni, Zn and Mn in the outdoor samples were more likely affected by crust. Strong correlations were found only for Pb and Sb with polybrominated diphenyl ethers (PBDEs). The hazard index for on-site human exposure to Pb was at a chronic risk. Despite the low deleterious risk of BFRs, concern should be given to DBDPE; the chronic toxicity of which is not known.

Heavy metal pollution is one of the most serious environmental issues globally. To evaluate the metal pollution in the Red Sea coast of Hodeida, Yemen Republic, the concentrations of Fe, Cu, Ni, Pb, and Cd in water, sediment, and some vital organs of sea catfish, Arius thalassinus collected from polluted and unpolluted sites, were determined. The risk of these metals to humans through fish consumption was then assessed. The results showed that the concentration order of metals in water, sediment, and fish tissues were Fe > Cu > Ni > Pb > Cd. The levels of studied metals in water, sediment, and fish tissues were significantly higher in the polluted site than those of the unpolluted site, with few exceptions. Linear correlation incorporating paired variables (water-sediment, water-fish, and fish-fish) exhibited several significant correlations indicating a common metal pollution. The risk assessment performed revealed that fish consumption was safe for consumers. This field investigation provides a baseline data on metal pollution in this region.

The effects of singlet oxygen (¹O₂) transfer to bacteria attached on phytodetritus were investigated under laboratory-controlled conditions. For this purpose, a nonaxenic culture of Emiliania huxleyi in late stationary phase was studied for bacterial viability. Our results indicated that only 9 ± 3 % of attached bacteria were alive compared to 46 ± 23 % for free bacteria in the E. huxleyi culture. Apparently, under conditions of low irradiance (36 W m⁻²), during the culture, the cumulative dose received (22,000 kJ m⁻²) was sufficiently important to induce an efficient ¹O₂ transfer to attached bacteria during the senescence of E. huxleyi cells. At this stage, attached bacteria appeared to be dominated by pigmented bacteria (Maribacter, Roseobacter, Roseovarius), which should resist to ¹O₂ stress probably due to their high contents of carotenoids. After subsequent irradiation of the culture until fully photodegradation of chlorophyll, DGGE analyses showed that the diversity of bacteria attached to E. huxleyi cells is modified by light. Photooxidative alterations of bacteria were confirmed by the increasing amounts of cis-vaccenic photoproducts (bacterial marker) per bacteria observed during irradiation time. Interestingly, preliminary chemotaxis experiments showed that Shewanella oneidensis considered here as a model of motile bacteria was attracted by phytodetritus producing or not ¹O₂. This lack of repulsive effects could explain the high mortality rate of bacteria measured on E. huxleyi cells.

Eighty-seven soil samples collected from North China were analyzed for decabromodiphenyl ethane (DBDPE). The concentrations of DBDPE ranged from undetectable to 1612 ng/g, with the highest concentration present in Shandong. Additionally, the mean concentration of DBDPE in Shandong was found to be onefold higher than those found in Hebei and Shanxi, likely due to DBDPE production in Shandong. Relatively high concentrations of DBDPE in soils were also present in the south of Tianjin, where e-waste recycling may provide a source in this region. The fractions of DBDPE [DBDPE/(DBDPE + BDE209)] were lower than 0.5 in most soil samples, in agreement with the fact that deca-BDE is currently the main additive in brominated flame retardants (BFR) used in China. An obvious decreasing trend in DBDPE concentrations from east to west in North China was noted, with relatively higher DBDPE concentrations present in Shandong. A soil ingestion exposure assessment showed that for most sites, soil ingestion EDI was slightly lower than inhalation EDI; exceptions were found in several polluted sites, where soil ingestion was a more significant exposure route.

The introduction of a gene, strain, or microbial consortium into an indigenous bacterial population is known as bioaugmentation. This technique has been proposed as an effective strategy for accelerating and enhancing the removal of recalcitrant and toxic compounds during wastewater treatment. In this study, three types of reactors were used to test whether quorum sensing plays an important role in bioaugmented systems. Reverse transcriptase polymerase chain reaction showed that the inoculated strain, HF-1, successfully colonized in the bioaugmented reactor. Meanwhile, no HF-1 colonization was observed in the quorum-quenching and non-bioaugmented reactors. Removal of nicotine in the bioaugmented reactor was almost 100 %, and removal of total organic carbon (TOC) was higher than 50 %. However, less than 20 % of nicotine and 30 % of TOC was removed in quorum-quenching and non-bioaugmented reactors. Moreover, the release of acylated homoserine lactones reached the threshold for HF-1 biofilm formation in bioaugmented reactors but not in quorum-quenching or non-bioaugmented reactors. The addition of porcine kidney acylase I, a quenching reagent, to the quorum-quenching reactor hampered the colonization of HF-1. Together, these results demonstrate that quorum sensing plays an important role in HF-1 colonization of bioaugmented systems.

The stereoselective dissipation of flutriafol and tebuconazole in grape had been studied. A simple and sensitive method for determination of flutriafol and tebuconazole enantiomers in grape was developed by high-performance liquid chromatography on a cellulose tris(3-chloro-4-methylphenylcarbamate) column. The limits of quantification for flutriafol and tebuconazole in grape were 0.033 and 0.043 mg kg⁻¹, respectively. The dissipations of flutriafol and tebuconazole stereoisomers in grape followed first-order kinetics (R² > 0.93). The stereoisomers of flutriafol and tebuconazole were enantioselectively degraded in grape, and tebuconazole was more enantioselective than flutriafol. The half-life of (−)-tebuconazole was 5.2 days and shorter than (+)-tebuconazole with half-life of 6.4 days. The (−)-flutriafol was also preferentially degraded in grape, the half-lives of which were 6.59 and 6.98 days for (−) and (+)-flutriafol, respectively. The enantiomeric ratio value of the two fungicides was nearly 1.0 at the 1st day and increased to 1.143 for flutriafol and 2.015 for tebuconazole at the 28th day. The stereoselective dissipations could provide a reference to fully evaluate the risks of two important chiral triazole fungicides.

The methylmercury (MeHg) cycling at water–sediment interface in an acid mine drainage (AMD)-polluted reservoir (Aha Reservoir) and a reference site (Hongfeng Reservoir) were investigated and compared. Both reservoirs are seasonal anoxic and alkaline. The concentrations of sulfate, sulfide, iron, and manganese in Aha Reservoir were enriched compared to the reference levels in Hongfeng reservoir due to the AMD input. It was found that the MeHg accumulation layer in Aha Reservoir transitioned from the top sediment layer in winter to the water–sediment interface in spring and then to the overlying water above sediment in summer. It supported the assumption that spring methylation activity may start in sediments and migrate into the water column with seasonal variation. The weaker methylation in sediment during spring and summer was caused by the excessive sulfide (∼15–20 μM) that reduced the bioavailability of mercury, while sulfate reduction potential was in the optimal range for the methylation in the overlying water. This led to a transport flux of MeHg from water to sediment in spring and summer. In contrast, such inversion of MeHg accumulation layer did not occur in Hongfeng Reservoir. The sulfate reduction potential was in the optimal range for the methylation in top sediment, and dissolved MeHg was positively related to sulfide in pore water of Hongfeng Reservoir (r = 0.67, p < 0.001). This result suggested that accumulation of MeHg in lake water and cycling of MeHg at sediment–water interface associate with some sensitive environmental factors, such as sulfur.

A greenhouse pot experiment was conducted to study the effects of conventional nitrogen fertilization on soil acidity and salinity. Three N rates (urea; N0, 0 kg N ha⁻¹; N1, 600 kg N ha⁻¹; and N2, 1,200 kg N ha⁻¹) were applied in five soils with different greenhouse cultivation years to evaluate soil acidification and salinization rate induced by nitrogen fertilizer in lettuce production. Both soil acidity and salinity increased significantly as N input increased after one season, with pH decrease ranging from 0.45 to 1.06 units and electrolytic conductivity increase from 0.24 to 0.68 mS cm⁻¹. An estimated 0.92 mol H⁺was produced for 1 mol (NO₂⁻+ NO₃⁻)-N accumulation in soil. The proton loading from nitrification was 14.3–27.3 and 12.1–58.2 kmol H⁺ ha⁻¹in the center of Shandong Province under N1 and N2 rate, respectively. However, the proton loading from the uptake of excess bases by lettuces was only 0.3–4.5 % of that from nitrification. Moreover, the release of protons induced the direct release of base cations and accelerated soil salinization. The increase of soil acidity and salinity was attributed to the nitrification of excess N fertilizer. Compared to the proton loading by lettuce, nitrification contributed more to soil acidification in greenhouse soils.