We investigated the impacts of all anthropogenic aerosols and black carbon (BC) on the diurnal variations of cloud and precipitation over East China during August 2008 using a coupled meteorology and chemistry model (WRF-Chem). Comparison of the model results with observations showed that the model reproduced reasonably well the distribution patterns of the aerosol optical depth (AOD), the horizontal wind, precipitation, and the liquid water path (LWP). The results from ensemble numerical experiments showed the aerosol-induced cloud droplet number concentration (CDNC) increased by 20–160 cm⁻³ over East China. The aerosol-induced cloud fraction (CF) increased by 0.03–0.08 below 850 hPa and at around 750 hPa over East China; it decreased by up to 0.06 between 750 and 850 hPa at around 25°N and over Central China. These increases were larger at early morning and nighttime, whereas the decreases were larger in the afternoon and evening. Other scattering aerosols were the main contributor to the increase of CDNC and offset the decrease induced by BC. The decrease of CF over Central China was mainly caused by BC. The precipitation induced by aerosols decreased by 20–200 mm over South and North China with the largest decrease over the North China Plain and southwest China. There was an increase of 20–100 mm over Central China. The decrease in precipitation over South and North China mainly occurred during the day, whereas the increase in precipitation over Central China mainly occurred at night which was caused by BC.

The effect of solids retention time (SRT) on volatile fatty acids (VFAs) accumulation and microbial community evolutions in enzymolysis-pretreated waste activated sludge (WAS) fermentation process was investigated. SRT played important roles on VFA accumulation efficiency and composition with a best performance of over 2200 mg COD/L at an SRT of 8 days. Volatile suspended solids (VSS)/total suspended solids (TSS) of fermentative sludge decreased obviously during the fermentation tests at various SRTs. Distribution spread index (DSI) of fermentative WAS augmented from 1.175 to 1.218 in accordance with SRT rising from 6 to 11 days. SRT changes led to microbial community (bacterial and archaeal) shifts clearly as well as the community diversity in the fermentation system. Bacterial community evenness tended to be more uneven at an SRT of 8 days compared to SRTs of 6 and 11 days, which indicated that high dominance of bacterial community could be formed at 8 days SRT with more VFA accumulation in WAS fermentation system. RDA inferred that microbial consortia could be driven by the preponderant individual VFA accumulation (acetate, propionate, and N-butyrate) with getting to a relative balance level by SRT optimization in the system.

The textile industry is responsible for the disposal of a large volume of effluents containing synthetic dyes, which are considered to be highly toxic compounds for both human health and the environment. The aim of the present study was to test potential use of a renewable, low-cost product—Luffa cylindrica in disk and powder form—as adsorbent material for the treatment of textile effluents containing dyes. Saccharomyces cerevisiae cells were also immobilized on L. cylindrica to increase the adsorbent capacity. Batch experiments were conducted for the evaluation of the removal of the azo dye Direct Red 23. The Langmuir, Freundlich, and Temkin isotherms were used for a better interpretation of the data. The results showed that adsorption is more efficient at acidic pH and all adsorbent materials best fit the Langmuir model, indicating the formation of a monolayer. The isotherm results also demonstrated that the materials immobilized with the yeast had a greater sorption rate, but the cell-free L. cylindrica powder had a higher adsorbate/adsorbent interaction. The comparison with a spectrophotometrically defined standard revealed that the powder without and with yeast cells was able to achieve an acceptable removal rate of the dye from the solution. Moreover, the difference in adsorption between the powder without and with yeast cells was very small. Thus, the application of the cell-free L. cylindrica powder is economically more feasible. The findings demonstrate the potential use of L. cylindrica powder as an adsorbent for the treatment of effluents containing textile dyes.

We present a study on the radioactivity of selected Croatian agricultural soils that vary considerably with respect to geological background; physical, chemical, and biological characteristics; soil type; land use; and soil management. Our investigation is focused on the main naturally occurring radionuclides (⁴⁰K, ²³⁸U, ²²⁶Ra, ²³²Th, ²³⁵U) and ¹³⁷Cs as the most threatening long-lived anthropogenic radionuclide. We find that the radioactivity level is not influenced by the application of different soil amendments, at least in moderate quantities, and that no effect of soil management can be detected as well. In contrast, geological and location-specific properties influence radionuclide content in soil, especially regarding the naturally occurring ones. Moreover, physical and chemical soil properties such as texture and soil adsorption complex, respectively, seem to be the main factors regarding fixation of ¹³⁷Cs in soil. Calculated dose rates for external exposure to the gamma radiation originating from soil have been found to be generally low, except for two locations where they are higher but not at a level that would lead to health problems for workers on the field.

Occurrence of halonitromethanes (HNMs) in drinking water has been a concern recently due to the potentially high human health risks of HNMs. Mechanisms of formation of HNMs during disinfection has remained controversial. The objective of this study was to investigate the effects of nitrite on the formation of trichloronitromethane (TCNM), a dominant HNM species occurring in chlorinated water. Polyhydroxy-phenols (hydroquinone, catechol, resorcinol, and phloroglucinol) and sugars (glucose, maltose, and lactose) were compared as surrogates/model compounds of common organic precursors of humic and non-humic substances in natural organic matter, respectively. The results showed that TCNM was not detectable after chlorinated sugars with the addition of nitrite. Upon chlorinating the polyhydroxy-phenols, TCNM formation varied greatly among different compounds, i.e., resorcinol > phloroglucinol > catechol >> hydroquinone. The results demonstrated that TCNM formation in the presence of nitrite was a function of aromaticity as well as the position and number of hydroxyl groups on the benzene rings of a compound, and the TCNM formation potential of humic substances was greater than that of non-humic substances. For catechol, resorcinol, and phloroglucinol, TCNM formation varied greatly with pH but generally remained stable with the increase of reaction time and temperature.

Land application of organic manure, crop residue, and biosolid, an important means for the disposal and recycling of wastes, has been shown to significantly increase the amount of dissolved organic matter (DOM) in soil. However, limited information is available on the dynamics of DOM, the concentration is usually expressed by dissolved organic carbon (DOC), and its influence on Cd behaviors in paddy soil amended with and without organic materials during rice (kinmaze) growing season. In this study, in situ field experiments were conducted to investigate the dynamics of DOC in paddy soil amended with green manure (GM), pig manure (PM), and chemical fertilizer (F) and its effect on Cd mobility and bioavailability. The results showed that DOC concentrations in soil solutions extracted from different depths were higher in GM and PM plots than those in F plot, and DOC concentrations all declined with time and rice growth. DOC concentrations in the root zone soil for all treatments were higher than those in the non-root zone due to root exudation and the higher pH value. The temporal dynamics of DOC in the root zone were found to be correlated to rice growth stage, as DOC concentrations decreased in the initial stage (week 1 to 6) of rice seedling and then gradually increased and reached the highest levels with 30.42 mg DOC L⁻¹ for GM, 28.88 mg DOC L⁻¹ for PM, and 19.19 mg DOC L⁻¹ for F at rice heading and flowering stage (week 10), hereafter decreased again until when the rice was harvested. However, soil DOC in the non-root zone exhibited a continuous decrease trend and remained at a relatively low level after week 10 with 15.36 mg DOC L⁻¹ for GM, 15.31 mg DOC L⁻¹ for PM, and 8.43 mg DOC L⁻¹ for F. The dynamics of water soluble Cd displayed statistically significant positive relationship with DOC (r ₀.₀₁ = 0.765, n = 9) regardless of soil depth and root presence/absence, suggesting that DOC enhanced the mobility and transport of through the formation of Cd-DOC complexes. As a result, DOC could increase the potential uptake of Cd by rice as well as the downward Cd migration to deeper soil. In these experiments, the uptake of Cd by rice grown in the GM and PM plots reached 5.55 and 3.71 mg plot⁻¹, respectively, which were much higher than that in the F plot with 1.88 mg plot⁻¹. The amounts of Cd downward migration were 17.0 mg plot⁻¹ for GM plot, 14.74 mg plot⁻¹ for PM plot, and 4.13 mg plot⁻¹ for F plot, respectively. It could be concluded that the application of green manure and pig manure to Cd-contaminated paddy soil will increase the risk of Cd uptake by rice and Cd downward migration into groundwater. For this reason, care should be taken when organic manures was applied to contaminated soil to remediate or alleviate soil pollution and maintain soil fertility as well as provide nutrients for plant growth.

The reaeration coefficient (K ₐ) is an essential parameter to predict the dissolved-oxygen concentration in different aquatic ecosystems. The techniques applied to K ₐ estimates require considerable efforts, since measuring this coefficient is a laborious and expensive task. Thus, the use of predictive equations wherein K ₐ is found through hydraulic flow parameters is common. However, the available prediction equations lead to estimates often different from each other. A new predictive equation is addressed in the present study. The insertion of a dimensionless number resulting from the relation between the RMS (Root Mean Square) of the free-surface vertical velocity and the surface flow velocity is the great innovation of the study. The reaeration experiments and the surface vertical velocity mapping were performed in a circular hydraulic channel. The flow velocity varied from 0.25 to 0.64 m s⁻¹, and depth varied from 0.09 to 0.15 m. The new equation led to more accurate results than the equations based on traditional hydraulic parameters such as the Reynolds and Froude numbers, mainly when it comes to K ₐ values higher than 40 day⁻¹. The sensitivity analysis has shown that the new dimensionless number is the most sensitive parameter of the herein proposed predictive equation and that the influence from the Reynolds and Froude numbers on K ₐ weakens as turbulence gets more intense.

Nanoscale zero valent iron (NZVI) was synthesized by the reduction of natural limonite under hydrogen conditions. The adsorption performance of the as-prepared NZVI on phosphate was evaluated through batch and column experiments. The removal of phosphate (PO₄³⁻) significantly decreased with an increase of pH from 2.0 to 11, whereas a remarkable increase of PO₄³⁻ removal was observed in the presence of SO₄²⁻ and S₂O₃²⁻. In addition, Cl⁻ and NO₃⁻ also improved phosphate removal at concentrations of more than 0.2 mmol/L. Kinetic studies indicated that the removal process of PO₄³⁻ on NZVI can be easily followed with the pseudo-second-order kinetic model. The removal of phosphate from the oxic system was significantly higher than that of the anoxic system, which was attributed to the formation of the secondary phase by the further oxidization of Fe²⁺. The adsorption capacity of the as-prepared NZVI of the oxic system was 16 mg/g, and the pH was 6.3. The column experiments further demonstrated that the as-prepared NZVI presented a high removal capacity for PO₄³⁻-P. These findings indicated that the as-prepared NZVI displayed an excellent ability to remove phosphate from aqueous solutions.

In the present research, the distribution and subcellular localization of cadmium in the roots, shoots, and leaves of Monochoria hastata were evaluated to understand structural and ultrastructural changes caused by the metal. Several visual toxic symptoms such as withering, chlorosis, and falling of leaves appeared in M. hastata, especially at 15 mg L⁻¹ Cd concentration. Analysis of Cd concentration by ICP-OES showed that Cd concentrations in the root were significantly higher than those in the shoot and found to be in the following order: root > stem > leaf. Bioconcentration factor (BCF) and translocation factor (TF) were used to evaluate accumulation and transfer of metals from the root to aerial parts. TF of Cd in M. hastata was <1 in all three Cd concentrations. But it has quite considerable extent of BCF value suggesting that M. hastata is a moderate accumulator. SEM has provided a strong evidence of closing of stomata due to Cd-induced stress. The results of TEM showed the deposition of electron-dense material in vacuoles, cell wall, chloroplasts, and mitochondria. Besides, significant ultrastructural changes such as changes of the shapes of the chloroplasts, reduction of the number of cristae, high vacuolization in the cytoplasm, decrease in the intercellular spaces, shrinkage of vascular bundle, and loss of cell shape were observed in the TEM micrograph study. FTIR analysis revealed the presence of different functional groups which are responsible for binding of Cd ions in the biomass. From the above study, it is clear that M. hastata can potentially be useful for the removal of Cd from Cd-containing wastewater.

This study aimed to investigate a novel method of red mud neutralisation by Ca(NO₃)₂ (NRM), keeping its adsorption capacity in relation to natural red mud (RM) for Ni(II), Pb(II) and Zn(II). Results pointed out that the neutralisation process decreases the pH and electrical conductivity values on NRM due to reaction between the carbonate and bicarbonate alkalinity of red mud and calcium from calcium nitrate to form calcite (CaCO₃). The maximum adsorption capacity values of RM and NRM, respectively, were 1.78 and 1.79 mmol g⁻¹ for Ni(II), 2.13 and 2.23 mmol g⁻¹ for Pb(II) and 1.14 and 1.06 mmol g⁻¹ for Zn(II). Pseudo-second-order model is the main responsible for the adsorption of these metals on RM and NRM. The adsorption reaction is endothermic and these metals have affinity to RM and NRM. Thus, it is possible to neutralise the red mud with Ca(NO₃)₂ without adsorption capacity losses of Ni(II), Pb(II) and Zn(II).