Effect of soil composition and dissolved organic matter on pesticide sorption

The effect of the solid and dissolved organic matter fractions, mineral composition and ionic strength of the soil solution on the sorption behaviour of pesticides were studied. A number of soils, chosen so as to have different clay mineral and organic carbon content, were used to study the sorption of the pesticides atrazine (6-chloro-N2-ethyl-N4-isopropyl-1,3,5-triazine-2,4-diamine), 2,4-D ((2,4-dichlorophenoxy)acetic acid), isoproturon (3-(4-isopropylphenyl)-1,1-dimethylurea) and paraquat (1,1'-dimethyl-4,4'-bipyridinium) in the presence of low and high levels of dissolved organic carbon and different background electrolytes. The sorption behaviour of atrazine, isoproturon and paraquat was dominated by the solid state soil components and the presence of dissolved organic matter had little effect. The sorption of 2,4-D was slightly affected by the soluble organic matter in the soil. However, this effect may be due to competition for adsorption sites between the pesticide and the soluble organic matter rather than due to a positive interaction between the pesticide and the soluble fraction of soil organic matter. It is concluded that the major factor governing the sorption of these pesticides is the solid state organic fraction with the clay mineral content also making a significant contribution. The dissolved organic carbon fraction of the total organic carbon in the soil and the ionic strength of the soil solution appear to have little or no effect on the sorption/transport characteristics of these pesticides over the range of concentrations studied.     

颗粒活性炭吸附对预臭氧后微污染原水水质影响研究

在不同的预臭氧浓度条件下处理微污染原水,考察了颗粒活性灰（GAC）吸附对处理后水样水质的影响.选择化学需氧量（CODMn）、溶解性有机碳（DOC）、生物可降解溶解性有机碳（BDOC）、UV254和氨氮（NH;-N）含量及有机物分子量分布作为考察吸附效果的检测指标.结果表明,在静态吸附时间达到5天时,颗粒活性炭吸附曲线开始趋于平缓,吸附时间超过5天之后吸附趋于饱和;预臭氧含量为2.5 mg/L时,颗粒活性炭对有机物的吸附效果最佳,对CODMn、DOC、BDOC的去除率分别为53.2％,63.2％和36.2％;在不同预臭氧处理条件下,颗粒活性炭对NH;-N的吸附效果并未表现出较大的差异,吸附去除率约为5％;颗粒活性炭优先吸附水中分子量＞ 10kDa的有机物,其次为分子量＜1 kDa的有机物.     

The cumulative effect of three decades of phosphogypsum amendments in reclaimed marsh soils from SW Spain: (226)Ra, (238)U and Cd contents in soils and tomato fruit

Phosphogypsum (PG), a by-product of the phosphate fertiliser industries, has been applied as soil amendment to reduce Na saturation in soils, as in the reclaimed marsh area from SW Spain, where available PG has a typical fingerprint of 710+/-40 Bq kg(-1) of (226)Ra, 165+/-15 Bq kg(-1) of (238)U and 2.8+/-0.4 mg kg(-1) of Cd. This work was focussed on the cumulative effects of PG amendments on the enrichment of these pollutants in cultivated soils and plants (Lycopersicum esculentum Mill L.) from the area studied, where PG has been applied since 1978 at recommended rates of 20-25 Mg ha(-1) every 2-3 years. A field experiment was conducted over three years to compare activity concentrations of (226)Ra ((214)Pb) and (238)U ((234)Th) in non-reclaimed soils, reclaimed soils with no additional PG application, and reclaimed soils with two additional PG applications. A non-significant effect of two PG amendments (in three years) was observed when compared with non-amended reclaimed plots. Nevertheless, a significant (p<0.05) enrichment of (226)Ra was observed in the surface horizon (0-30 cm) of reclaimed plots relative to deeper horizons and also when compared with the surface horizon of non-reclaimed soil (p<0.05), thereby revealing the cumulative effect of three decades of PG applications. Furthermore, the effect of a continuous application of PG was studied by analysing soils and tomato fruits from six commercial farms with different cumulative rates of PG applied. Cadmium concentrations in tomatoes, which were one order of magnitude higher than those found in tomatoes from other areas in South Spain, were positively correlated (r = 0.917) with (226)Ra-concentration in soils, which can be considered an accurate index of the cumulative PG rate of each farm.     

Experimental and modelling study on the uptake and desorption kinetics of 133Ba by suspended estuarine sediments from southern Spain

Dispersion of pollutants in aquatic environments depends on their uptake by suspended solids. This work deals with the uptake kinetics of 133Ba (gamma-emitter and a good analogue of 226Ra) by suspended estuarine sediments (which can be resuspended into the water column under certain conditions). This study presents a wide set of tracing experiments, including second tracing, decantation and desorption processes. The purpose is to characterize 133Ba uptake by sediments and to investigate the use and limitations of box models in order to describe the uptake kinetics. Water and sediment samples were collected in the Huelva estuary (Spain), where environmental 226Ra concentrations have been increased by two phosphate fertilizer industries. Samples were characterized by granulometric, organic carbon content, cation exchange capacity and XRF-EP analyses. Results revealed three-step kinetics, with characteristic times of minutes, hours and days. These results enabled the selection and calibration of a suitable box model and facilitated the testing of its use as a fully predictive tool.     

Radium migration through clay liners at waste disposal sites

The migration of 226Ra through the bottom compacted clay liner of the wastewater disposal reservoirs of an industrial plant that processes uranium ore was evaluated. An instrumental method for 226Ra analysis in soils, consisting of detector calibration, the determination of detector counting efficiency, cumulative counting of both background and soil samples in regular counting intervals, and photo-peak smoothing was developed. The 226Ra was analyzed by means of its granddaughter 214Bi, at a photo-peak of 609 keV. The results showed that most of the 226Ra which diffused from the solution into the soil was retained in the upper layer of the sample, and that just a small percentage migrated to the subjacent layers. This methodology is adequate for the assessment of the migration of radionuclides through soil layers and for environmental impact studies related to contamination of soils by radionuclides.     

Arsenic speciation and mobilization in CCA-contaminated soils: influence of organic matter content

A laboratory incubation experiment was conducted to investigate the influence of organic matter content on arsenic speciation and mobilization in chromated copper arsenate (CCA)-contaminated soils. The study was performed with four synthetic CCA-contaminated soils, with a range of organic matter content (mixture of peat moss and poultry manure) varying between 0.5% and 15% (w/w), under unsaturated and aerobic conditions for 40 days. Changes in water-soluble arsenic speciation (As(V), As(III), MMAA, DMAA) were monitored over time in soil extracts by HPLC-ICP-MS and in the soil solid phase (As(III), As(V)) by a solvent extraction method. Irrespective of organic matter content, As(V) was the predominant soil bound and aqueous phase arsenic species. However, over 40 days, a high soil organic matter content (7.5% and 15%) was able to entail formation of soil bound As(III). Moreover, total water-soluble arsenic was positively correlated with dissolved organic carbon (r(2)=0.88). However, the organic matter content did not influence arsenic speciation in the soluble fraction; neither As(V) reduction nor arsenic biomethylation occurred within 40 days. An increase in dissolved organic carbon content promoted both As(V) and As(III) solubilization in soils. Also, over time, organic matter contents of 7.5% and 15% entailed the persistence of soluble As(V), likely due to the high content of dissolved organic compounds which prevented its sorption onto soil. Based on this data, the environmental risk of aerobic CCA-contaminated soils rich in organic matter may be due to an enhanced availability of soluble As(V) over time, rather than to the formation of the more toxic and more mobile As(III).     

Major nutrients and acidity: budgets and trends at four remote boreal stands in Finland during the 1990s

Major nutrients and acidity were studied at six plots in four Integrated Monitoring catchments in Finland, located along a south-north deposition gradient. The quality and quantity of bulk precipitation, throughfall, soil water, and litterfall were monitored during the period 1989-1997. The results showed a marked decline in SO4 and H+ concentrations overall. Trends in throughfall ANC values were positive, while those in soil water were mostly negative. The increase in throughfall ANC values indicates recovery from acid deposition. The adsorption of base cations and release of organic acids was implicated in the decrease in soil water ANC trends. For all variables, the changes tended to be the greatest in the most southerly catchment, which received the most deposition loads. Mass balance budgets showed that total deposition inputs were greater than soil leaching outputs (at 40 cm) for NO3, NH4 and SO4, and were attributed to nutrient uptake and cycling processes. In contrast, for Ca, Mg, K and Na, and S (Valkea-Kotinen3 and Vuoskoj?rvi2 plots only), inputs were less than outputs, indicating net leaching. Throughfall + litterfall inputs to the forest floor showed that the organic layer is particularly important in the retention of Ca, Mg and N. Sulfur was retained in the lower soil layers, and attributed to Al and Fe hydroxide adsorption in the B horizon.     

The isolation and characterization of fulvic acid and humic acid from river water

Many rivers in New Hampshire are rich in dark brown organic matter from natural sources. Because the interactions between metal ions like Fe³⁺ and the organic fulvic and humic acids makes water treatment difficult, we are studying the nature of the organic acids.

Fulvic acid was isolated from the B₂ horizon of a Podzol soil obtained at Conway, NH, and fulvic and humic acids were isolated from the Oyster River (Lee, NH) and Jewel Pond (Stratham, NH). The method of isolating the organic matter from water involves new techniques. The oxygen-containg functional groups, carbon, hydrogen, and nitrogen were analyzed for all samples. The fulvic acid and humic acid samples isolated from water are different from each other, but similar to analogous soil samples.     

Removal of exhausted oils by adsorption on mixed Ca and Mg oxides

Adsorption tests were performed on two different exhausted oils to reduce their polluting and health hazard potential: a "water-insoluble oil", utilised for automotive engine lubrication, and an "emulsified" oil, used as coolant for metal-cutting tools. Dolomite, a low-cost recovery material, was used to prepare two effective adsorbents: (a) a mixed Ca and Mg oxide obtained by thermal decomposition of dolomite at 1800 degrees C, and (b) an activated material obtained by submitting this product to chemical treatment with HCl. Preliminary tests carried out with an excess of the former material showed that the insoluble oil was adsorbed with lower yield (Y = 0.40) than the soluble (emulsified) oil (Y = 0.60). The material activation with HCl remarkably improved the adsorption of soluble oil organic fraction (Y > 0.90), while only a little increase in the removal yield was observed for the insoluble oil (Y = 0.44). The results presented and discussed in this work pointed out that the products of dolomite calcination can successfully replace the conventional adsorbing materials in the removal of organic pollutants, with particular concern to exhausted soluble oils, which cannot usually be recycled, thus reducing the operational costs of their treatment.     

Binding and mobility of mercury in soils contaminated by emissions from chlor-alkali plants

Chlor-alkali plants are known to be an important source of Hg emissions to the atmosphere and related contamination of soils in their vicinity. In the present study, the results of Hg speciation and mobility of Hg in soils affected by Hg emissions from three chlor-alkali plants are compared. Solid phase mercury speciation analyses was carried out using a mercury-thermo-desorption technique with the aim of distinguishing elemental Hg [Hg(0)] from Hg(II)-binding forms. Mercury species in soil leachates were distinguished using an operationally defined method, which is based on the reactivity of soluble Hg compounds. Results show that the Hg(0) emitted from the plants could not be detected in any of the investigated soils. This indicates quantitative re-emission or oxidation of this Hg species in the atmosphere or soils. In most soils Hg was predominately bound to organic matter. Only in sandy soils deficient in organic matter was Hg, to a larger extent, sorbed onto mineral soil components. Leachable Hg in most soils occurred as non-reactive, soluble organic Hg complexes such as fulvic acid-bound Hg, and reach their highest values (90 microg kg(-1)) in soils rich in organic matter. Concentrations of reactive, soluble Hg compounds were highest in sandy soils where the content of organic matter was low. Leachability of Hg was found to be inhibited in soils with a high content of clayey soil components. The distribution of Hg in soil profiles suggests that migration of Hg to deeper soil layers (approx. 20 cm) is most effective if Hg is bound to soluble organic complexes, whereas reactive Hg or weak Hg complexes are effectively retained in the uppermost soil layer (5 cm) through sorption on mineral surfaces.     

The influence of ammonia and carbon dioxide on the sorption of a basic organic pollutant to a mineral surface

Indoor surfaces have a sorptive capacity for organic pollutants which may be significantly influenced by other gases and the pH of the surface. In this research, we examine the influence of a common indoor gaseous acid, CO2, and base, NH3, on the adsorption of a volatile organic base, trimethylamine (TMA), to a mineral surface, zirconium silicate beads. Varying ammonia and CO2 within concentration ranges of indoor relevance substantially influences the sorptive capacity of this mineral surface. Increasing the CO2 mixing ratio to 1000 p.p.m. enhances surface capacity of TMA by 40-50%; increasing the NH3 mixing ratio to 10 p.p.m. decreases the TMA surface capacity by approximately 5-80% depending on relative humidity. The phenomena of dissolution of TMA into bulk surface water and acid-base chemistry in the surface water do not adequately describe equilibrium adsorption on this surface. Instead, adsorption to the dry solid or to adsorbed water layers appears to dominate. Reduction in the equilibrium partition coefficient, ke, in the presence of NH3 is due to a competition between TMA and ammonia molecules for adsorption sites. Site competition appears to follow the Langmuir competitive model and most ke values range from 0.003-0.045 m. PRACTICAL IMPLICATIONS: Sorptive interactions with indoor surfaces strongly influence indoor exposure to pollutants. For basic or acidic compounds, these interactions are themselves influenced by surface pH and competition with other acidic or basic gases such as CO2 and NH3. We show that CO2 tends to cause mineral surfaces to store more amines but NH3 tends to decrease this surface capacity. Given the typical range of indoor CO2 and NH3 concentrations, the indoor sorbtive capacity of amines on mineral surfaces may vary by greater than an order of magnitude.     

Fate of carbamazepine and anthracene in soils watered with UV-LED treated wastewaters

Water disinfection technologies based on ultraviolet (UV) radiations emitted by Light-Emitting Diodes (LED), as a wastewater tertiary treatment, have been shown to be promising for water reuse. Here, we assessed the fate of two ubiquitous pollutants, carbamazepine and anthracene, in soil watered with either UV-LED treated wastewaters or irrigation water. After 3 months, anthracene and carbamazepine were transformed two and three times faster respectively, in soils watered with UV-LED wastewater than in soils watered with tap water (probably because of the addition of organic matter by the effluent). Laccase activity was induced in the presence of the pollutants and anthraquinone was found as anthracene product of oxidation by laccases. Moreover, the addition of these pollutants into soil did not affect the functional diversity of autochthonous microbial communities assessed by Ecolog plates. Cellulase, protease and urease activities increased in soils watered with UV-LED treated wastewaters (UV-LED WW), showing transformation of organic matter from the effluent and lipase activity increased by anthracene addition, confirming the potential role of these enzymes as indicators of hydrocarbon contamination.     

Adsorption and desorption of heavy metals in bottom mud of urban rivers

An adsorption experiment has been carried out to determine the factors affecting the uptake of heavy metals by bottom mud in urban rivers. The adsorption of Cu, Zn, Cd, and Pb was described using the Freundlich adsorption equation. The Freundlich constant (K) was related to the grain size and organic matter content of bottom mud. It was found that the main factor controlling the adsorption of metal was organic matter, since the adsorbed metals decreased remarkably due to the destruction of organic matter from the fine bottom mud. The desorption experiment proved that the metals adsorbed by mud were extracted approx. 100% with dilute HCI. Therefore, the amount of heavy metal adsorbed per 1 g of TOC can be calculated from the acid soluble metal content of bottom mud. Moreover, the method of extraction by 2 N CH₃COONH₄ can be used to distinguish between an ion exchangeable form by minerals and a chemical form by organic matter.The adsorption and desorption experiments indicated that fine bottom mud with a high organic matter content contributes to the uptake of metals in urban rivers and that such metals can be extracted with 0.5 N HCI.     

Perfluoroalkyl acids in urban stormwater runoff: Influence of land use

Perfluoroalkyl acids (PFAAs) are persistent organic pollutants in the environment and have been reported to have nonpoint sources. In this study, six PFAAs with different chain lengths were monitored in stormwater runoff from seven storm events (2009–2011) at various outfall locations corresponding to different watershed land uses. We found PFAA(s) in 100% of stormwater runoff samples. Monitoring results and statistical analysis show that PFAAs in stormwater runoff from residential areas mainly came from rainfall. On the other hand, non-atmospheric sources at both industrial and commercial areas contributed PFAAs in stormwater runoff. The mass flux of PFAAs from stormwater runoff in the Twin Cities (Minneapolis and St. Paul, MN) metropolitan area is estimated to be about 7.86 kg/year. In addition, for the first time, we monitored PFAAs on the particles/debris in stormwater runoff and found high-level PFOS on the particulate matter in runoff collected from both industrial and commercial areas; the levels were so high that the finding could not be explained by the solid–water partitioning or adsorption. PFOS on the particulate matter is suspected to have originated from industrial/commercial products, entering the waste stream as PFOS containing particles.     

Indicators of change in the organic matter in arid soils

Soil organic matter is a key component in ecosystems, as it is the essential part of a set of relevant processes and constitutes an important carbon pool contributing to Global Change. The design of environmental monitoring programmes should include indicators of the current status of ecosystems, alerting to incipient changes in them. In this context, a sampling scheme has been designed taking into account the main processes and soil uses affecting the dynamics of soil organic matter. Well-tested parameters were determined in order to assess which of them are most useful as indicators of soil organic matter evolution in arid soil, such as that in the "Cabo de Gata-Níjar" Natural Park (SE Spain). The parameters characterising the lability of the different fractions indicate changes in soil organic matter triggered by changes in soil use and soil dynamics. Changes in soil use, when drastic, are best reflected by those fractions comprising a high percentage of the total soil carbon, while the processes having slower dynamics are best demonstrated by the labile fractions. As a result of the sensitivity analysis of parameters versus changes, and taking into account the operational difficulties for determining them, the following indicators are proposed for a monitoring programme: total organic carbon, active fraction of the organic carbon and ratios of this fraction versus total organic carbon (%) (as given by the lability index proposed).     

Treatment of pulp and paper mill wastewater--a review

Pulp and paper mills generate varieties of pollutants depending upon the type of the pulping process. This paper is the state of the art review of treatability of the pulp and paper mill wastewater and performance of available treatment processes. A comparison of all treatment processes is presented. Combinations of anaerobic and aerobic treatment processes are found to be efficient in the removal of soluble biodegradable organic pollutants. Color can be removed effectively by fungal treatment, coagulation, chemical oxidation, and ozonation. Chlorinated phenolic compounds and adsorable organic halides (AOX) can be efficiently reduced by adsorption, ozonation and membrane filtration techniques.     

Linearity assumption in soil-to-plant transfer factors of natural uranium and radium in Helianthus annuus L

The linearity assumption of the validation of soil-to-plant transfer factors of natural uranium and (226)Ra was tested using Helianthus annuus L. (sunflower) grown in a hydroponic medium. Transfer of natural uranium and (226)Ra was tested in both the aerial fraction of plants and in the overall seedlings (roots and shoots). The results show that the linearity assumption can be considered valid in the hydroponic growth of sunflowers for the radionuclides studied. The ability of sunflowers to translocate uranium and (226)Ra was also investigated, as well as the feasibility of using sunflower plants to remove uranium and radium from contaminated water, and by extension, their potential for phytoextraction. In this sense, the removal percentages obtained for natural uranium and (226)Ra were 24% and 42%, respectively. Practically all the uranium is accumulated in the roots. However, 86% of the (226)Ra activity concentration in roots was translocated to the aerial part.     

The role of zeolites in wastewater treatment of printing inks

The adsorption of residual organic pollutants from flocculated printing ink wastewater onto several synthetic zeolites was investigated as a finishing method for additional reduction of TOC. The nonselective removal of total organic content was studied. The amount of adsorbed organics was largest for ZSM-5 and NH4-Beta while the other zeolites studied showed lower efficiency, suggesting that adsorption is independent of pore structure. The adsorption rates of organic pollutants were fast. Although the TOC removal increases with increasing amount of zeolite, because of the necessity of additional filtration to lower turbidity to required levels, 5.0 g/L of zeolite was found to be optimum. The 88% reduction of TOC obtained with a single flocculation treatment was improved with the combination of flocculation and adsorption with ZSM-5 which resulted in the overall TOC efficiency of 95%. The addition of zeolites in decantated supernatant water, obtained after flocculation, was also studied in order to assess the effect of floc on zeolite capacity. A decrease in adsorption capacity occurred only if a coagulant concentration less than optimal was applied. Removal efficiency then decreased by around 10%. It was concluded that flocculation followed by adsorption with zeolites is an effective treatment method for this kind of wastewater.     

生物陶粒反应器水源水处理工艺研究

利用生物陶位反应器对水源水生物预处理进行研究．试验研究了该反应器对水源水法度、色度、有机物、氨氮等的去除效果；分析探讨了水头损失变化规律；分析比较了生物预处理与其它处理方法对水源水中总有机物（ＴＯＣ）的去除．结果表明，生物陶粒反应器是一种有效的生物预处理设备，有着广阔的应用前景．     

Distribution,cycling and mean residence time of 226Ra, 210Pb and 210Po in the Tagus estuary

Results for dissolved and particulate ²²⁶Ra, ²¹⁰Pb and ²¹⁰Po in the Tagus river, estuary and coastal sea system show different distribution and chemical behaviour patterns for these radionuclides in the three aquatic environments. ²²⁶Ra from riverborne particles dissolves in the estuary and contributes to increased concentrations of dissolved ²²⁶Ra in estuarine water. In the estuary, dissolved ²¹⁰Pb and ²¹⁰Po from river discharge and atmospheric deposition are scavenged by suspended matter, which in turn becomes enriched in these nuclides in comparison with riverborne particles. As a result of these processes, the estuarine water flowing into the coastal sea contains enhanced concentrations of dissolved ²²⁶Ra, but is depleted in dissolved ²¹⁰Pb and ²¹⁰Po. Under average river flow conditions, mass balance calculations for dissolved ²¹⁰Po and ²¹⁰Pb in the estuary allowed their mean residence times to be estimated as 18 and 30 days, respectively. Due to the rapid sorption of these radionuclides on to settling particles, bottom sediments in the estuary represent a sink for ²¹⁰Pb and ²¹⁰Po from both natural sources and industrial waste releases. Results also suggest that partial re-dissolution of these radionuclides from bottom sediments and intertidal mudflats is likely to occur in the mid- and low-estuary zones. Nevertheless, box-model computations indicate that the discharge of ²¹⁰Pb and ²¹⁰Po into the coastal sea takes place mainly with the transport of sediment, whereas the discharge in the dissolved fraction can only account for one third of the activities entering the estuary in the soluble phase. Implications of these results to the cycling of radionuclides in phosphate waste releases into estuarine environments are discussed.