Assessment of contamination load on water,soil and sediment affected by the Kongjujeil mine drainage,Republic of Korea

Environmental pollution in the Kongjujeil mine creek was determined on the basis of physicochemical and mineralogical properties for various kinds of waters, soils, precipitates and sediments collected in August and December 1998. The hydrochemistry of water is characterized by an enrichment in concentrations of Ca ²⁺, Si, alkali ions, NO ₃ ^- and Cl ^- in ground and surface water, where relatively the mine waters are significantly enriched in Ca ²⁺+Mg ²⁺, Al, heavy metals and SO ₄ ^2- concentrations. The mine waters have lower pH (3.24) and higher EC (613 µS/cm) compared with those of ground and surface water. The ranges of dD and d ¹⁸O values (SMOW) in the water are -50.2 to -61.6‰ and -7.0 to -8.6‰. Using a computer code, the saturation indices of albite, calcite and dolomite in the mine water show that it is undersaturated, and has progressively evolved toward the equilibrium state. Ground and surface water are nearly saturated. The gibbsite, kaolinite and smectite are supersaturated in the surface and groundwater. Geochemical modeling shows that mostly toxic metals exist largely in the form of metal sulfates and free metals in mine water. These metals in the surrounding fresh water could be formed of carbonate or hydroxide complex ions. Minerals within the soil and sediment near the mining area were partly variable consisting of quartz, mica, alkali feldspar, plagioclase, chlorite, vermiculite, berthierine and clay minerals. The separated heavy minerals, soil and sediment are composed of some pyrite, arsenopyrite, chalcopyrite, sphalerite, galena, malachite, goethite and various hydroxide minerals. Some potentially toxic elements (As, Cd, Cu, Pb, Sb and Zn) are found in extremely high concentrations in the surface soils in the vicinity of the mine. The enrichment index of heavy metals in sediment and surface soil of the mine drainage was very severe, while it was not so great in the cultivated soil.     

Lead enrichment, adsorption and speciation in urban garden soils under long-term wastewater irrigation in northern Nigeria

Unsafe lead (Pb) concentrations in leafy vegetables raised in urban and peri-urban agricultural production systems have been reported across cities in Northern Nigeria, even though Pb concentrations in soils are within regulatory safe levels. This study examined the soil enrichment, adsorption and chemical species of Pb in urban garden fields irrigated with untreated wastewater at three industrial locations in Kano, northern Nigeria. Total Pb in the soil profiles ranged from 9 to 91 mg kg^?1 and decreased rapidly from the surface to the subsurface layer, but attaining nearly constant concentration at depth ≥1.2 m in the profiles. The potentially labile Pb maintained fairly constant concentration with depth up to 0.9 m, but decreased fairly rapidly with depth thereafter. There was a significant Pb enrichment of the soils, extending up to 30–60 cm depth in the soil profiles. The adsorption of Pb by the soils increased drastically with pH, and attained maximum adsorption at pH ≥ 7.0 in the surface layer, and at pH ≥ 6 in the subsurface layer. The surface soils adsorbed between 85 and 97 % of added Pb at pH ≤ 5. Free Pb²⁺ activities in soil solution accounted for between 46 and 87 % at pH 5–7 of total dissolved Pb (Pb_T). The quantifiable chemical species of Pb in solution consisted mainly of PbOH⁺, PbSO ₄ ^· , PbCl⁺ and PbOH ₂ ^· which accounted for between 0.9 and 26 % of Pb_T in soil solution at pH ≥ 5.0, but declining to between 0.1 and 2.1 % at pH ≥ 7.5. There was no apparent equilibrium between Pb²⁺ activities and known Pb-compounds in the soils. It was concluded from the data that reports of excess Pb concentrations in leafy vegetables raised in these soils are consistent with high free Pb²⁺ activities maintained in soil solution by these predominantly sandy-textured soils.     

Efficiency assessment of aerobic biological effluent treatment plant treating pharmaceutical effluents

The present paper undertakes a study of the physico-chemical properties and toxic heavy metals content in the untreated and treated pharmaceutical effluents in order to evaluate the working efficiency of industrial effluent treatment plants. The treatment efficiency achieved for various parameters was conductivity (79.94%), alkalinity (93.91%), hardness (87.70%), chloride (89.24%), cyanide (79.66%), phosphate (99.19%), total dissolved solids (85.89%), total suspended solids (96.87%), salinity (52.41%), dissolved oxygen (27.32%), biochemical oxygen demand (83.39%) and chemical oxygen demand (72.21%). The removal efficiency achieved for different heavy metals was Cu²⁺ (79.66%), Ni²⁺ (69.22%), Cr⁶⁺ (80.15%), Pb²⁺ (72.14%), Fe³⁺ (92.59%) and Zn²⁺ (90.61%). The level of biochemical oxygen demand (64 mg L^?1) in the treated effluents was above the limit of 30.0 mg L^?1, chemical oxygen demand level (208 mg L^?1) was close to a limit of 250 mg L^?1, while average Pb²⁺ concentration (0.10 mg L^?1) was on the borderline of maximum permissible limit of 0.10 mg L^?1 set by Central Pollution Control Board for safe discharge of industrial effluent in inland surface water. The average concentration of cyanide (0.01 mg L^?1) in the treated industrial effluent of our study is of great concern to the fisheries of freshwater ecosystem in which the effluents finally get discharged. Based on the results of the present study, it is concluded that the pollution level in the discharged pharmaceutical effluent is of the great concern requiring proper treatment and regular scientific monitoring so as to protect the environmental degradation of water resources and facilitate the propagation of the aquatic life.     

Assessing cadmium risk in wheat grain using soil threshold values

At present, the prior-established threshold values are widely used to classify contaminated agricultural soils with heavy metals under the cultivation of a variety of crops, without considering the different sensitivity of plants to heavy metals. Evaluation of the characteristics of cadmium transfer from a polluted calcareous soil to cultivated wheat crop and assessment of the efficiency of using the threshold values to reflect the soil pollution risk by cadmium in Zanjan Zinc Town area at the northwest of Iran were the goals of this study. Totally, 65 topsoil (0–20 cm) and corresponding wheat samples of an agricultural region in the proximity of a metallurgical factory were collected and analyzed for cadmium concentration. The results revealed that industrial activities strongly control cadmium distribution in the studied soils. Relatively high bioavailable cadmium contents (mean 0.77 mg kg^?1) were found in the soils, notwithstanding their alkalinity. It was observed that just 22.5% of the studied area around the Zinc Town is covered by polluted soils with the cadmium concentration exceeding the maximum permissible concentration of 5 mg kg^?1, whereas cadmium concentration in wheat grains of 19 sampled plants is higher than the threshold value of 0.2 mg kg^?1. Among these polluted plants, a total of eight samples were grown in areas classified as unpolluted soils with cadmium, based on the soil threshold value. It seems that this misclassification of polluted soils is mainly related to the crop sensitivity to heavy metals uptake from the soil which should be considered.     

Adsorption characteristics of heavy metals in soil zones developed on spilite

Various soil zones such as Bw, C1, and C3 are developed on spilite. Montmorillonite, vermiculite and chlorite is moderately occurred in the C1 and C3 soil zones, in contrast montmorillonite and vermiculite are absent in Bw soils whereas illite and sesquioxide are relatively increased. The high cation exchange capacity (CEC) of montmorillonite and vermiculte and moderate CEC of chlorite and illite resulted in the high adsorption of heavy metals. The adsorption of the heavy metals on spilite soil zones was studied at different concentrations and pH levels. Heavy metals like lead, cadmium, and copper were selected for adsorption studies considering their contribution as toxic metals in the environment. The initial solute concentrations ranged from 7.0 × 10⁻³ to 1.0 × 10² mg/L. The sorption behavior of Cd²⁺, Pb²⁺, and Cu²⁺ on soil zones of spilite was investigated using the batch equilibrium technique at 25°C. The characteristics of the adsorption process were investigated using Scatchard plot analysis (q/C vs. q) by the batch equilibrium technique at 25°C. In the adsorption of heavy metals, deviation from linearity in the plot of q/C versus q was observed, indicating the presence of multi-model interaction and non-Langmuirean behavior. When the Scatchard plot showed a deviation from linearity, greater emphasis was placed on the analysis of the adsorption data in terms of the Freundlich model, in order to construct the adsorption isotherms of the metal(s) at particular concentration(s) in solutions. The adsorption behavior of these metal ions on spilite soil zones is expressed by the Freundlich isotherms. Adsorption constants and correlation coefficients for the Cd, Pb, and Cu on spilite soil zones were calculated from Freundlich plots.     

Kinetic of biogenic sulfide production for microbial consortia isolated from soils with different bioaccessible concentrations of lead

Different technologies have been implemented for the treatment of acid mine drainage. Among these are technologies such as geochemical barriers and sulfidogenic reactors, which use biogenic sulfide (produced by sulfate-reducing bacteria) for metallic stabilization. Because both processes involve microorganisms, it is important to have a clear understanding of the factors that influence their activity in different toxic environments. Given that microbial communities isolated from polluted sites could have a higher tolerance to toxic ions, two consortia with sulfate-reducing activity were isolated from different soils impacted by mining activities. These soils had different total (401 and 19,300 mg Pb kg^?1), mobile (54 and 1,415 mg Pb kg^?1) and bioaccessible (316 and 3,175 mg Pb kg^?1) concentrations of lead. The kinetics of biogenic sulfide production (BSP) for both consortia were monitored in a batch reactor after they were exposed to different initial lead concentrations. These lead concentrations were established based on the results of lead mobility tests. The estimated BSP rates and biomass concentrations of both consortia showed different responses to the presence of lead. Results highlighted that lead sulfide precipitation on microbial cell is a tolerance mechanism identified and this one is triggered for the lead bioaccessible concentrations threshold in soil. These results could be useful for the designing of processes based on sulfate reducing activity for the removal or stabilization of metal present in water or soil, respectively.     

Oxidation mechanisms and chemical bioavailability of chromium in agricultural soil – pH as the master variable

Chromium (Cr) is a heavy metal that exists in soils in two stable oxidation states, +III and +VI. The trivalent species is an essential nutrient, whereas the hexavalent species is highly toxic. This study investigated the environmental impact of Cr^III potentially released into soil from wastes and various materials by determining the risk of oxidation of initially soluble inorganic Cr^III into hazardous Cr^VI. The principal aim was to describe the pH-dependent mechanisms that regulate 1) the formation of Cr^VI from the easily soluble Cr^III and 2) the potential bioavailability of Cr^III and that of Cr^VI species produced in the oxidation of Cr^III in agricultural soil (fine sand, organic carbon 3.2%). The amount of Cr^VI formed in oxic soil conditions was regulated by two counteracting reactions: 1) oxidation of Cr^III into Cr^VI by manganese oxide (Mn^IVO₂) and 2) the subsequent reduction of Cr^VI by organic matter back to Cr^III. The effect of pH on this net-oxidation of Cr^III and on the chemical availability of both Cr^III and Cr^VI species was investigated in soil samples incubated with or without excessive amounts of synthetic MnO₂, over the chemically adjusted pH range of 3.9–6.3 (+22 °C, 47 d). In soil subsamples without added MnO₂, the net-oxidation of Cr^III into Cr^VI (1 mM CrCl₃ in soil suspensions, 1:10 w/V) was negligible. As for the MnO₂-treated soils, at maximum only 4.7% of added Cr^III was oxidized – regardless of the high oxidation potential of these subsamples. The lowest production of Cr^VI was observed under acidic soil conditions at pH ∼4. At low pH, the net-oxidation diminished as result of enhanced reduction of Cr^VI back to Cr^III. At higher pHs, the oxidation was limited by enhanced precipitation (or adsorption) of Cr^III, which lowered the overall amount of Cr^III susceptible for oxidation. Moreover, the oxidation reactions by MnO₂ were inhibited by formation of Cr(OH)₃ coverage on its surface. The pH-dependent chemical bioavailability of added Cr^III differed from that of the Cr^VI formed. At elevated pHs the chemical availability of Cr^III decreased, whereas that of Cr^VI produced increased. However, the risk of Cr^VI formation through oxidation of the easily soluble inorganic Cr^III was considered to be low in agricultural soils high in organic matter and low in innate MnO₂.     

Heavy metals concentration in soils under rainfed agro-ecosystems and their relationship with soil properties and management practices

Heavy metals are governed by parent material of soils and influenced by the soil physicochemical properties and soil and crop management practices. This paper evaluates total heavy metal concentrations in rainfed soils under diverse management practices of tropical India. Vertisols (clayey soils with high shrink/swell capacity) had the highest concentrations of heavy metals. However, chromium (Cr) content was above the threshold value in Aridisol [calcium carbonate (CaCO₃)]-containing soils of the arid environments with subsurface horizon development. Concentration increased at lower depths (>30 cm). Basaltic soils showed higher concentrations of nickel (Ni), copper (Cu) and manganese (Mn). Cadmium (Cd), cobalt (Co), Cu and Mn concentrations were higher in soils cultivated to cotton, whereas Cr concentration was above the threshold level of 110 mg kg^?1 in food crop cultivated soils. As the specific soil surface is closely related to clay content and clay type, soil’s ability to retain heavy metals is more closely tied to the specific surface than to the soil cation exchange capacity. Higher positive correlations were found between heavy metal concentrations and clay content [Cd(r = 0.85; p ≤ 0.01); Co (r = 0.88; p ≤ 0.05); Ni (r = 0.87; p ≤ 0.01); Co (r = 0.81; p ≤ 0.05); Zn (r = 0.49; p ≤ 0.01); Cr (r = 0.80; p ≤ 0.05); Mn (r = 0.79; p ≤ 0.01)]. The amounts of nitrogen–phosphorus–potassium applied showed a positive correlation with Co and Ni (r = 0.62; p ≤ 0.05). As several soils used for growing food crops are high in Ni, Cr and Mn, the flow of these metals in soil–plant–livestock/human chain needs further attention.     

Environmental risk assessment of some potentially toxic elements in El-Tabbin region (Cairo, Egypt)

As much as 24 soil samples and 6 stream sediments from the River Nile were studied in El-Tabbin region (Great Cairo, Egypt). Twelve chemicals, potentially toxic elements posing potential environmental risk, were the object of concern in this study. Mean contents of analysed elements (in mg kg^?1) in soils and the River Nile stream sediments were the following: As_s 3.6/As_ss 1.5, Cd_s 0.33/Cd_ss 0.12, Cr_s 87.7/Cr_ss 141.5, Cu_s 40.3/Cu_ss 43.8, Hg_s 0.03/Hg_ss 0.13, Pb_s 33.3/Pb_ss 20.2, Zn_s 150/Zn_ss 109, Se_s 0.24/Se_ss 0.05, Ni_s 37.2/Ni_ss 48, Sb_s 1.25/Sb_ss 1, Ba_s 892/Ba_ss 431, V_s 103.3/V_ss 167.8. Furthermore, geochemical background values were derived for soil and stream sediment samples. The values are as follows (in mg kg^?1): As_s 1.33/As_ss 1, Cd_s 0.48/Cd_ss 0.05, Cr_s 54.7/Cr_ss 106.5, Cu_s 23.8/Cu_ss 23, Hg_s 0.025/Hg_ss 0.095, Pb_s 15.3/Pb_ss 13.5, Zn_s 70/Zn_ss 55, Se_s 0.13/Se_ss 0.05, Ni_s 19.5/Ni_ss 32.5, Sb_s 1/Sb_ss 1, Ba_s 266/Ba_ss 275, V_s 50.7/V_ss 119. More than two-thirds of soil and sediment samples exceeded established (based on literature data) risk limit values for non-polluted environment. Based on environmental risk assessment for potentially toxic elements in soils and sediments in more than 45% of total area disturbed environment (I _ER = 1–3) was documented and more than 13% of territory was characterised with highly disturbed environment (I _ER > 3).     

Amendments affect lead mobility and modulated chemo-speciation under different moisture regimes in normal and salt-affected lead-contaminated soils

The total lead content in the soil itself is insufficient as a measure to indicate the actual environmental risks related to the presence of lead in the soil. Understanding the mobility of lead and its chemical speciation in soil solution is of great importance for accurately assessing environmental risks posed by lead. Therefore, a laboratory study was carried out to evaluate the effect of inorganic amendments (gypsum, rock phosphate and di-ammonium phosphate) on lead mobility and chemical speciation under different moisture regimes (flooding regime and 75 % field capacity) in normal and salt-affected lead-contaminated soils. After 2, 7, 15, 30, 100 and 110 days of incubation, pore water samples were collected by using Rhizon soil moisture samplers. In order to estimate the chemical speciation of lead in pore water, Visual MINTEQ 3.0 modeling approach was used. The results showed that presence of free Pb²⁺, PbCl⁺, Pb(SO₄) ₂ ^2? , and PbH₂PO₄ ⁺ was significantly (P ≤ 0.05) affected by the soil moisture regime, incubation time and applied amendments in lead-contaminated soils. The Visual MINTEQ 3.0 predicted free Pb²⁺ species concentration was found higher in lead-contaminated soils, while PbCl⁺ was more pronounced in salt-affected soils. Gypsum increased the occurrence of Pb(SO₄) ₂ ^2? , while di-ammonium phosphate and rock phosphate enhanced the PbH₂PO₄ ⁺ species formation and decreased free Pb²⁺ species in pore water. Thus, gypsum is the most effective in reducing lead and free Pb²⁺ species concentrations in the pore water under different soil moisture regimes and incubation times in normal and salt-affected lead-contaminated soils.     

Carcinogenic risk evaluation for human health risk assessment from soils contaminated with heavy metals

Human activities have progressively increased in recent years. Consequently, significant environment deterioration resulted. Soils have a particularly varied vulnerability to heavy metal pollution, especially in the vicinity of industrial areas. Heavy metal contamination of soil may induce risks and hazards to humans and the ecosystem, while toxic metals in soil can severely inhibit the biodegradation of organic contaminants. This paper is focused on human health risk assessment from extremely contaminated soil with heavy metals, mainly with carcinogenic elements. The study refers to an agricultural area in the vicinity of an old metallurgical processing industrial facility. The contaminants evaluated in the present paper are beryllium (Be), cadmium (Cd), chromium (Cr), nickel (Ni) and lead (Pb). Contamination level is pointed out through laboratory analysis results of soil samples taken from 0–0.2 m, 0.2–0.4 m soil layers and up to 2.1 m soil depth. Some heavy metal concentrations (Cd, Cr and Pb) exceed the intervention thresholds for sensitive areas, as they are stipulated in the national regulation in Romania. The identified average concentration levels of Cd, Cr^VI and Pb in the first layer of the investigated land are 23.83, 7.71 and 704.22 mg/kg_d.w, respectively. The results show that the potential risk of human health is relevant (higher than the acceptable one after World Health Organization) and a possible solution for the remediation should become a major concern for the investigated area.     

Iron and Pyritization in Wetland Soils of the Florida Coastal Everglades

We explored environmental factors influencing soil pyrite formation within different wetland regions of Everglades National Park. Within the Shark River Slough (SRS) region, soils had higher organic matter (62.65 ± 1.88 %) and lower bulk density (0.19 ± 0.01 g cm^?3) than soils within Taylor Slough (TS; 14.35 ± 0.82 % and 0.45 ± 0.01 g cm^?3, respectively), Panhandle (Ph; 15.82 ± 1.37 % and 0.34 ± 0.009 g cm^?3, respectively), and Florida Bay (FB; 5.63 ± 0.19 % and 0.73 ± 0.02 g cm^?3, respectively) regions. Total reactive sulfide and extractable iron (Fe) generally were greatest in soils from the SRS region, and the degree of pyritization (DOP) was higher in soils from both SRS (0.62 ± 0.02) and FB (0.52 ± 0.03) regions relative to TS and Ph regions (0.30 ± 0.02 and 0.31 ± 0.02, respectively). Each region, however, had different potential limits to pyrite formation, with SRS being Fe and sulfide limited and FB being Fe and organic matter limited. Due to the calcium-rich soils of TS and Ph regions, DOP was relatively suppressed. Annual water flow volume was positively correlated with soil DOP. Soil DOP also varied in relation to distance from water management features and soil percent organic matter. We demonstrate the potential use of soil DOP as a proxy for soil oxidation state, thereby facilitating comparisons of wetland soils under different flooding regimes, e.g., spatially or between wet years versus dry years. Despite its low total abundance, Fe plays an important role in sulfur dynamics and other biogeochemical cycles that characterize wetland soils of the Florida coastal Everglades.     

Diffusion of municipal waste contaminants in compacted lateritic soil treated with bagasse ash

Compacted clay can minimize infiltration of liquid into waste or control the release of contaminated liquids to the surrounding soils and groundwater. Compacted lateritic soil treated with up to 12 % bagasse ash and municipal solid waste (MSW) leachate sourced from a domestic waste land fill were used in diffusion test studies to access the diffusion characteristics of some inorganic species present in the municipal solid waste leachate. Diffusion set-up were prepared containing 0, 4, 8 and 12 % bagasse ash—soil mixes compacted at 2 % wet of optimum using the modified proctor effort. The set up was saturated with water for 30 days before the introduction of MSW leachate and initiation of diffusion test for another 90 days. After diffusion testing, water content within the soil column showed a decrease with depth. Diffusion test results generally showed that diffusion is an active means of transport of chemical species even at very low flow rates in the compacted soil-bagasse ash mixes, and the effective diffusion coefficient is affected by bagasse ash. The pore fluid concentration profile for the various chemical species tested showed that the compacted soil-bagasse ash mix has the capacity to attenuate Ca²⁺, Pb²⁺ and Cr³⁺ ions.     

The synergistic effect of calcium on organic carbon sequestration to ferrihydrite

Sequestration of organic carbon (OC) in environmental systems is critical to mitigating climate change. Organo-mineral associations, especially those with iron (Fe) oxides, drive the chemistry of OC sequestration and stability in soils. Short-range-ordered Fe oxides, such as ferrihydrite, demonstrate a high affinity for OC in binary systems. Calcium commonly co-associates with OC and Fe oxides in soils, though the bonding mechanism (e.g., cation bridging) and implications of the co-association for OC sequestration remain unresolved. We explored the effect of calcium (Ca²⁺) on the sorption of dissolved OC to 2-line ferrihydrite. Sorption experiments were conducted between leaf litter-extractable OC and ferrihydrite at pH 4 to 9 with different initial C/Fe molar ratios and Ca²⁺ concentrations. The extent of OC sorption to ferrihydrite in the presence of Ca²⁺ increased across all tested pH values, especially at pH ≥ 7. Sorbed OC concentration at pH 9 increased from 8.72 ± 0.16 to 13.3 ± 0.20 mmol OC g^?1 ferrihydrite between treatments of no added Ca²⁺ and 30 mM Ca²⁺ addition. Batch experiments were paired with spectroscopic studies to probe the speciation of sorbed OC and elucidate the sorption mechanism. ATR-FTIR spectroscopy analysis revealed that carboxylic functional moieties were the primary sorbed OC species that were preferentially bound to ferrihydrite and suggested an increase in Fe-carboxylate ligand exchange in the presence of Ca at pH 9. Results from batch to spectroscopic experiments provide significant evidence for the enhancement of dissolved OC sequestration to 2-line ferrihydrite and suggest the formation of Fe–Ca-OC ternary complexes. Findings of this research will inform modeling of environmental C cycling and have the potential to influence strategies for managing land to minimize OM stabilization.     

Reclamation of calcareous saline–sodic soil using different amendments: Time changes of soluble cations in leachate

Soil salinity and sodicity are escalating problems worldwide, especially in arid and semiarid regions. A laboratory experiment was conducted using soil column to investigate leaching of soluble cations during reclamation process of a calcareous saline–sodic soil (CaCO₃?=?20.7%, electrical conductivity (EC)?=?19.8 dS m^?1, sodium absorption ratio (SAR)?=?32.2[meq L^?1]^0.5). The amendments consisted of control, cattle manure (50 g kg^?1), pistachio residue (50 g kg^?1), gypsum (5.2 g kg^?1; equivalent of gypsum requirement), manure + gypsum and pistachio residue + gypsum, in three replicates which were mixed thoroughly with the soil, while sulfuric acid as an amendment was added to irrigation water. To reflect natural conditions, after incubation period, an intermittent irrigation method was employed every 30 days. The results showed that EC, SAR, and soluble cations of leachate for the first irrigation step were significantly higher than those of the subsequent leaching runs. Moreover, the concentration of removed soluble cations was lower for the control and gypsum-treated soils. It was found that among applied amendments, treatments containing cattle manure showed higher concentrations of sodium, calcium, and magnesium in the leachate, while due to pistachio residue application, further amount of potassium was removed out of soil column. The addition of pistachio residue resulted in the highest reduction in soil salinity and sodicity since the final EC and exchangeable sodium percentage dropped to 18.0% and 11.6% of their respective initial values, respectively. In the calcareous soil, solubility of gypsum found to be limited, in contrast, when it was added in conjunction with organic amendments, greater amounts of sodium were leached.     

Experimental study of the selective adsorption of heavy metals onto clay minerals

The interaction between minerals and heavy metals has been a hot object of study in environmental science,mineralogy and soil science,Through the selective adsorption experiment of Ca-montomorillonite,illite and kaolinite to Cu2 ,Pb^2 ,Zn^2 ,Cd^2 ,and Cr^3 ions at certain conditions,it could be concluded that Cr^3 is most effectively sorbed by all the three minerals.Also,it can be found that Pb^2 shows a strong affinity for illite and kaolinite while cu^2 for montmorillonite .Based on the adsorption experiment at varying pH of solution,it can be found that the amount of heavy etals sorbed by minerals increases with increasing pH of the solution.     

Effect of Fe2+ amendment on photodegradation kinetics of imidacloprid in moist soil

The present study deals with the effect of Fe²⁺ on degradation kinetics of imidacloprid in moist soil under UV system. The moist soil samples were spiked with imidacloprid and irradiated in specially designed UV-photoreactor. The analysis of imidacloprid was carried out by using HPLC–DAD system. UV irradiation caused about ten fold increase in photodegradation rate of the pesticide. Amendment of soil with Fe²⁺ at concentrations of 30 mg/kg led to a further increase in the rate of photodegradation, i.e., a 98 % degradation of imidacloprid was observed in the presence of iron after 32 days of irradiation. Moreover, the half-life of imidacloprid in Fe²⁺ -amended soil was observed to be reduced to 7 days that in the absence of Fe²⁺ was recorded to be 21 days. Iron was also observed to affect the half-life of imidacloprid in dark. When compared with unsterilized Fe²⁺-amended batch treatments, the t _1/2 in sterilized Fe²⁺-amended batch treatments increased from 58 to 96 days. Imidacloprid-urea was detected by HPLC as the only stable photodegradation byproduct of imidacloprid in the soil.     

Enhancement of deltamethrin degradation by soil bioaugmentation with two different strains of Serratia marcescens

Deltamethrin is one of the most commonly used pyrethroid in agricultural practice in different geographic regions of the world. It is detected in many environments, especially in soil and water, and can exhibit toxic effect to human and other organisms. In this study, we describe two bacterial strains DeI-1 and DeI-2, isolated from soil, and both identified as Serratia marcescens based on profile of the fatty acid methyl esters, biochemical test, and 16S RNA gene analysis, which were shown to efficiently degrade deltamethrin. Degradation of deltamethrin in mineral salt medium (50 mg l^?1) proceeded by strains DeI-1 or DeI-2 reached the values of 88.3 or 82.8 % after 10 days, and DT50 was 2.8 or 4.0 days, respectively. Bioaugmentation of deltamethrin-contaminated non-sterile soils (100 mg kg^?1) with strains DeI-1 or DeI-2 (3 × 10⁶ cells g^?1 of soil) enhanced the disappearance rate of pyrethroid, and its DT50 was reduced by 44.9, 33.1, 44.4, and 58.2 days or 39.1, 25.8, 35.6, and 46.0 days in sandy, sandy loam, silty loam, and silty soils, respectively, in comparison with non-sterile soils with only indigenous microflora. The three-way ANOVA indicated that DT50 of deltamethrin was significantly (P < 0.01) affected by soil type, microflora presence, and inoculum, and the interaction between these factors. Generally, the lower content of clay and organic carbon in soil, the higher degradation rate of deltamethrin was observed. Obtained results show that both strains of S. marcescens may possess potential to be used in bioremediation of deltamethrin-contaminated soils.     

Using chemical analysis and modeling to enhance the understanding of soil solution of some calcareous soils

The chemistry of soil solutions can be altered by human activities, due to the intense agricultural and husbandry, leading to leaching of nutrients and subsequently elevating ground water levels. Multivariate statistical and inverse geochemical modeling techniques were used to determine the main factors controlling soil solution chemistry of calcareous soils. In this research, a total of 21 calcareous soils was characterized and assessed for soil solution using soil column. The major cations in the studied soil solutions were in the decreasing order as Ca²⁺ > Mg²⁺ > Na⁺ > K⁺. The anions were also arranged in decreasing order as HCO $ _{3}^{ - } $  > Cl $ ^{ - } $  > SO $ _{4}^{2 - } $  > NO $ _{3}^{ - } $ . Concentrations of NO $ _{3}^{ - } $ , P, and K⁺ in soil solutions were in the range of 6.8–307.5 mg l^?1 (mean 63.2 mg l^?1), 5.0–10.4 mg l^?1 (mean 5.9 mg l^?1), and 2.8–54.6 mg l^?1 (mean 11.3 mg l^?1), respectively. Results suggest that the concentration of P in the soil solutions could be primarily controlled by the solubility of dicalcium phosphate dihydrate and dicalcium phosphate. Interactions between soil properties and observed solubility of nutrients were described, and put into empirical multivariate formulations. Obtained equations contained electrical conductivity (EC) as a key factor in determining nutrients solubility. Inverse geochemical modeling of soil solution using PHREEQC indicates the dissolution of calcite, anhydrite, halite, CO₂ (g), N₂ (g), and hydroxyapatite, and precipitation of sulfur. Cation exchange between Ca²⁺, Mg²⁺, K⁺ and Na⁺ occurred with Mg²⁺ and K⁺ into the solution, and Ca²⁺ and Na⁺ out of the solution. Determination of soil solution will improve soil management in the area, and preventing groundwater deterioration.     

Flux of nutrients and heavy metals from the Melai River sub-catchment into Lake Chini, Pekan, Pahang, Malaysia

This study was carried out to determine the flux of nutrients and heavy metals from the Melai sub-catchment into Lake Chini through the process of erosion. Melai River is one of the seven feeder rivers that contributed to the present water level of Lake Chini. Three properties of soils, such as particle size, organic matter content, and soil hydraulic conductivity and three chemical soil properties, such as available nutrients, dissolved nutrients, and heavy metals, were analyzed and interpreted. Potential soil loss was estimated using the revised universal soil loss equation model. The results show that the soil textures in the study area consist of clay, silty clay, clay loam, and sandy silt loam. The organic matter content ranges from 3.40 to 9.92 %, while the hydraulic conductivity ranges from 5.2 to 25.3 cm/h. Mean values of available P, K, and Mg amount was 8.5 ± 3.7 μg/g, 24.5 ± 3.4 μg/g, and 20.7 ± 18.6 μg/g, respectively. The highest concentration of soluble nutrients was SO ₄ ^?2 (815.8 ± 624.1 μg/g), followed by NO₃ ^?-N (295.5 ± 372.7 μg/g), NH₄ ⁺-N (24.5 ± 22.1 μg/g) and PO₄ ^3? (2.0 ± 0.8 μg/g). The rainfall erosivity value was 1658.7 MJ mm/ha/h/year. The soil erodibility and slope factor ranges from 0.06 to 0.26 ton h/MJ/mm and 7.63 to 18.33, respectively. The rate of soil loss from the Melai sub-catchment in the present condition is very low (0.0028 ton/ha/year) to low (18.93 ton/ha/year), and low level flow of nutrients and heavy metals, indicating that the Melai River was not the contaminant source of sediments, nutrients, and heavy metals to the lake.