Samples of surface sediment were collected off the north Shandong Peninsula for grain size and element analyses. Based on the grain size analysis, the surface sediments were dominated by silt and sand, with a small portion of clay, and were probably from the coastal erosion of the Shandong Peninsula. The spatial distribution patterns of the heavy metals were primarily controlled by the sediment types. The geo-accumulation indexes suggest that there was no Cu, Zn and Cr pollution in the study area; Pb and Cd contaminations appeared only at a few stations, while As pollution was distributed widely. The enrichment factors indicated that Cu, Zn and Cr were primarily from terrigenous materials. By contrast, Cd, Pb and As, and especially Cd and As, were probably largely provided by anthropogenic sources. Due to the dilution of coarse-grained matters, there was no contamination at some of the stations at which the influence of human activities was obvious.

The aim of this study was to assess the levels of heavy metal pollution in the clay/silt fraction (<63μm fraction) of marine sediments from Quintero Bay, Chile. For this, sediment samples were collected from 14 sites from the bay and analyzed for major and minor element determination. The metal concentrations found suggest an anthropogenic origin related with Cu, Se, Mo, As, Sb and Pb. The mineralogical characteristics of the samples were determined by XRD and selected samples were examined by SEM to determine morphological differences. The results showed heavy metal-bearing particles such as Cu, Zn, As and Pb, which are most likely associated with by the copper smelter.

Soil is a primary resource used by mankind to ensure its needs mainly through agriculture. Its sustainability is regulated by the indigenous organisms it contains such as microorganisms. Current agricultural practices employ mixtures of pesticides to ensure the crops yield and can potentially impair these non-target organisms. However despite this environmental reality, studies dealing the susceptibility of microorganisms to pesticide mixtures are scarce. In this context, we designed a 3-month microcosm study to assess the ecotoxicity of realistic herbicide mixtures of formulated S-metolachlor (Dual Gold Safeneur®), mesotrione (Callisto®), and nicosulfuron (Milagro®) on the abundance, the diversity, and the activities of microorganisms from a “clay/organic matter-rich” soil, with a particular attention given to N-cycle communities. These communities appeared to be quite resistant to realistic mixtures even if transient effects occurred on the N-cycle-related communities with an increase of ammonification and an inhibition of nitrification as a short-term effect, followed by an increase of denitrification and an accumulation of nitrates. As nitrates are known to be highly leachable with a strong pollution potential, intensive studies should be carried out at field level to conclude on this potential accumulation and its consequences. Moreover, these data now need to be compared with other agricultural soils receiving these herbicide mixtures in order to bring general conclusion on such practices.

Various geochemical studies have yielded conflicting data on whether humic coatings decrease or increase adsorption of heavy metals by soil minerals. The objective of the present study is to determine how humate pre-adsorption affects subsequent retention of Cd and Pb by palygorskite and sepiolite, as special silicate clay minerals of soil in many arid regions. For this purpose, a series of equilibrium batch experiments were conducted on the interactions of Pb and Cd with Ca–palygorskite and Ca–sepiolite before and after humate adsorption. The results showed that the Langmuir (L), Freundlich (F), Langmuir–Freundlich (LF), and Toth (T) equations satisfactorily described metal sorption data on the minerals. In the presence of humate as the pre-adsorbate, the values for sorption capacities of palygorskite and sepiolite for Cd and Pb slightly decreased. This can be attributed to the competition between humates and metal ions for mineral active sites and steric hindrance of the adsorbed humates, which reduces the access of metal ions to the mineral surface and internal channels. Humate coatings decreased the adsorption equilibrium constants of Cd, suggesting that the affinity of the organo-clays for Cd sorption is lower than those of Ca–clays. The values for the heterogeneity factor (β) generally showed an increasing trend with increasing humate coverage on palygorskite and sepiolite, which can be explained by the increased diversity of adsorption centers on humate–clay complexes. It may be concluded that the presence of humate bound on fibrous clay surfaces can influence the sorption, and hence the bioavailability and mobility of heavy metals in fibrous clay-containing arid and semiarid soils.

A sensitive, high-throughput, and cost-effective method for screening bacterial pathogens in the environment was developed. A variety of environmental samples, including aerosols, soil of various types (sand, sand/clay mix, and clay), wastewater, and vegetable surface (modeled by tomato), were concomitantly spiked with Salmonella enterica and/or Pseudomonas aeruginosa to determine recovery rates and limits of detection. The various matrices were first enriched with a general pre-enrichment broth in a dilution series and then enumerated by most probable number (MPN) estimation using quantitative PCR for rapid screening of amplicon presence. Soil and aerosols were then tested in non-spiked environmental samples, as these matrices are prone to large experimental variation. Limit of detection in the various soil types was 1–3 colony-forming units (CFU) g⁻¹; on vegetable surface, 5 CFU per tomato; in treated wastewater, 5 CFU L⁻¹; and in aerosols, >300 CFU mL⁻¹. Our method accurately identified S. enterica in non-spiked environmental soil samples within a day, while traditional methods took 4 to 5 days and required sorting through biochemically and morphologically similar species. Likewise, our method successfully identified P. aeruginosa in non-spiked aerosols generated by a domestic wastewater treatment system. The obtained results suggest that the developed method presents a broad approach for the rapid, efficient, and reliable detection of relatively low densities of pathogenic organisms in challenging environmental samples.

The objective of this study was to investigate the removal of multi-pesticides through a combined treatment process with coagulation–adsorption on nano-clay. Nano-clays like nano-bentonite, nano-halloysite and organically modified nano-montmorillonite were used as the adsorbent, and alum and polyaluminium chloride (PAC) were used as the coagulants. The coagulation method alone was not sufficient to purify water, whereas coagulation plus adsorption methods provided superior purification. Amongst the nano-clays used, organically modified nano-montmorillonite gave the best result in terms of pesticide removal from water. In order to evaluate the effect of coagulant addition on the removal efficiency of nano-clay, the respective adsorption isotherms were also calculated in the presence and absence of coagulants. Freundlich isotherm constants have shown that adsorption of pesticides on different nano-clay depends on the type of clay, presence and absence of coagulants as well as the properties of pesticides. The treatment combination having the maximum removal capacity was used efficiently for the removal of pesticides from natural and fortified natural water. The results indicated that alum–PAC coagulation aided by nano-clay as an adsorbent was the superior process for the simultaneous removal of multi-pesticides from water.

The large spatial heterogeneity in soil physico-chemical and microbial parameters challenges our ability to predict and model pesticide leaching from agricultural land. Microbial mineralization of pesticides is an important process with respect to pesticide leaching since mineralization is the major process for the complete degradation of pesticides without generation of metabolites. The aim of our study was to determine field-scale variation in the potential for mineralization of the herbicides glyphosate, bromoxyniloctanoate, diflufenican, and bentazone and to investigate whether this variation can be predicted by variations in basic soil parameters. Sixty-five soil samples were sampled from an agricultural, loamy field in Silstrup, Denmark, from a 60 × 165 m rectangular grid. The mineralization potential of the four pesticides was determined using a 96-well microplate ¹⁴C-radiorespirometric method. Initial mineralization rates were determined using first-order kinetics for glyphosate and bromoxyniloctanoate and zero-order kinetics for diflufenican and bentazone. The mineralization rates of the four pesticides varied between the different pesticides and the different soil samples, but we could not establish correlations between the pesticide mineralization rates and the measured soil parameters. Only the glyphosate mineralization rates showed slightly increasing mineralization potentials towards the northern area of the field, with increasing clay and decreasing OC contents. The mineralization potentials for glyphosate and bentazone were compared with 9-years leaching data from two horizontal wells 3.5 m below the field. The field-scale leaching patterns, however, could not be explained by the pesticide mineralization data. Instead, field-scale pesticide leaching may have been governed by soil structure and preferential flow events.

Copper bioavailability, specially to plants, is strongly dependent on its chemical form, as for most metals. Copper-contaminated soil can be treated in situ by the addition of minerals such as Na-bentonite, which mixed with surface soil, can transform this pollutant to non-bioavailable forms. In this work, shelter experiments were conducted to study the time evolution of Cu speciation, in pristine soil as well as in amended one. A selective sequential extraction method was employed to determine the metal speciation in the samples. The results show that the major metal fraction is the organic matter-bound one, whereas the exchangeable fraction is very low, even the first day after Cu addition. The time evolution shows a slow decrease of the organic-bound Cu and a corresponding increase of the most stable mineral fractions. With the addition of Na-bentonite to copper-contaminated soil, the most stable mineral fractions increase whereas the organic-bound one decreases, showing essentially similar time dependence of the several metal fractions. Sodium bentonite could be effectively used for remediation of soils polluted with Cu.

Soil salinization is a worldwide problem of which secondary salinization is increasingly more frequent, threatening agricultural production. Salt accumulation affects not only plants but also the physio-chemical characteristics of the soil, limiting its potential use. Climate change will further increase the rate of salinization of soil and groundwater as it leads to increased evaporation, promotes capillary rise of saline groundwater as well as increased irrigation with brackish water. Episodic seawater inundation of coastal areas is likely to increase in frequency as well. This work analyzed three types of salinization: seawater inundation (by irrigating soils with a 54 dS m⁻¹NaCl solution), saline groundwater capillary rise (soil contact with a 27 dS m⁻¹NaCl solution), and irrigation with two types of brackish water with different residual sodium carbonate (RSC). Two soils were used: a mineral soil (7.0 % clay; 0.7 % organic matter) and an organic soil (2.7 % clay; 7.4 % organic matter). The tested soils had different resilience to salinization: The mineral soil had higher sodium adsorption ratio (SAR) due to low levels of calcium + magnesium but had higher leaching efficiency and more limited effects of RSC. The organic soil however was more prone to capillary rise but seemingly more structurally stable. Our results suggest that short-term inundation with seawater can be mitigated by leaching although soil structure may be affected and that capillary rise of brackish groundwater should be carefully monitored. Also, the impact of irrigation with brackish water with high RSC can be inferior in soils with higher exchangeable acidity.

The study investigated phosphate adsorption from aqueous solutions using chemical- and thermal-modified bentonite in batch system. The adsorbent was characterized by SEM, BET, and FTIR spectroscopy. Contact time, beginning phosphate concentration, pH of the solution, and the effects of the temperature on phosphate adsorption capacity were determined by a series of experimental studies. In a wide pH range (3–10), high phosphate removal yields were obtained (between 94.23 and 92.26 %), and with the increase in temperature (from 25 to 45 °C), phosphate removal increased. Langmuir and Freundlich isotherms were used to determine the sorption equilibrium, and the results demonstrated that equilibrium data displayed better adjustment to Langmuir isotherm than the Freundlich isotherm. Phosphate sorption capacity, calculated using Langmuir equation, is 20.37 mg g⁻¹ at 45 °C temperature and pH 3. Mass transfer and kinetic models were applied to empirical findings to determine the mechanism of adsorption and the potential steps that control the reaction rate. Both external mass transfer and intra-particle diffusion played a significant role on the adsorption mechanism of phosphate, and adsorption kinetics followed the pseudo-second-order-type kinetic. Furthermore, thermodynamic parameters (ΔH°, ΔG°, ΔS°) which reveal that phosphate adsorption occur spontaneously and in endothermic nature were determined. The results of this study support that bentonite, which is found abundant in nature and modified as an inexpensive and effective adsorbent, could be used for phosphate removal from aqueous solutions.