Detection of herbicide subclasses by an optical multibiosensor based on an array of photosystem II mutants

Massive use of herbicides in agriculture over the last few decades has become a serious environmental problem. The residual concentration of these compounds frequently exceeds the maximum admissible concentration in drinking water for human consumption and is a real environmental risk for the aquatic ecosystem. Herbicides inhibiting photosynthesis via targeting photosystem II function still represent the basic means of weed control. A multibiosensor was constructed for detecting herbicides using as biosensing elements photosynthetic preparations coupled to an optical fluorescence transduction system (Giardi et al. EU patent EP1134585, 01830148.1-2204); this paper is about its application in the detection of herbicide subclasses in river water. Photosynthetic material was immobilized on a silicio septum inside a series of flow cells, close to diodes so as to activate photosystem II (PSII) fluorescence. The principle of the detection was based on the factthat herbicides selectively modify PSII fluorescence activity. The multibiosensor has the original feature of being able to distinguish the subclasses of the photosynthetic herbicides by using specific immobilized biomediators isolated from mutated organisms. This setup resulted in a reusable, portable multibiosensor for the detection of herbicide subclasses with a half-life of 54 h for spinach thylakoids and limit of detection of 3 x 10(-9) M for herbicides present in river water.     

Indicators for the exposure assessment of transformation products of organic micropollutants

Environmental transformation products of organic micropollutants have the potential to be similarly or even more mobile, persistent, ortoxic than their parent compounds. They should, therefore, be included in chemical hazard and risk assessment procedures as well as in the assessment of soil and water quality. To fulfill this requirement most efficiently, screening approaches that select relevant transformation products for detailed assessment are needed. This paper presents two process-based multimedia, multispecies models that allow us to quantitatively estimate the environmental fate of transformation products. The resulting exposure patterns are assessed with two indicators: joint persistence (JP), which describes the temporal extent of environmental exposure to a parent compound and its transformation products, and the predicted relative aquatic concentrations (RAC), which estimate the relative concentrations of parent compounds and their transformation products in surface water bodies. As a case study, JP and RAC are calculated for 16 pesticides and their relevant transformation products. The results for the JP indicator confirm the importance of considering transformation products in the assessment of overall persistence; for example, in the context of PBT assessments. Comparison of RAC results with monitoring data on herbicides and their transformation products shows the suitability of our approach for estimating relative concentrations in surface water, and as a consequence, its usefulness in identifying transformation products for future water quality monitoring programs. Transformation products of triketones and other highly used acidic herbicides are specifically identified as targets.     

Prioritization of pesticide environmental transformation products in drinking water supplies

Receiving waters within catchments may be exposed to many different transformation products following the application of pesticides. As environmental waters are abstracted for drinking water treatment these compounds may pose a risk to human health. This paper describes a prioritization approach for identifying the most important transformation products in drinking water sources. The approach can be applied to different geographical areas that have suitable pesticide usage data. The risk based approach incorporates data on pesticide usage and toxicity as well as transformation product formation, mobility, and persistence. The application of the approach is illustrated for two geographical areas that have good quality pesticide usage data: Great Britain and California. The transformation products with the highest risk index and a complete experimentally derived data set for Great Britain were 3,5,6-trichloro-2-pyridinol, thifensulfuron acid, and kresoxim-methyl acid and for California were carbendazim, aldicarb sulfoxide, and RP30228.     

An efficient methodology for quantification of synergy and antagonism in single electron transfer antioxidant assays

The development of new antioxidant compounds for incorporation in foods is a rapidly growing research area. The resulting interactions between complex antioxidant mixtures are a key issue; however, research in this area is still in its infancy. Experimental antioxidant models based on conventional dose–responses, that can predict joint effects of chemical mixtures, are urgently needed. This paper illustrates a methodological procedure for single electron transfer (SET) antioxidant assays to determine the synergistic and antagonistic effects of combining binary mixtures of antioxidants. Despite the abundance of theories and procedures to describe the synergistic/antagonistic effects in SET assays, they appear to be inadequate. Some features hindering advances in this field include the lack of: (1) experimental design, as a result of the extended use of unambiguous and simplistic procedures to quantify the effects of joint responses, based on single-dose values; (2) detailed mathematical hypotheses to quantify dose–response values, which in addition causes the associated difficulties for assessing the statistical consistence of the results; and (3) functional approaches that consider the possibility of interactive effects. This paper proposes solutions for each of these limitations. Established ideas from existing fields are used to replace the current simplistic procedures, in order to quantify the effects of joint responses. One of the common hypothesis (known as concentration addition) for describing the combined effects is established for SET assays. A dose dependent mathematical model representative of this hypothesis, based on probability functions with meaningful parameters, is applied. The interactive effects between antioxidants are introduced into the model with simple auxiliary functions that describe the variations induced by each antioxidant in the parameters that define the effects of the other. Finally, a comprehensive index to summarize the complex parametric responses in one single value is proposed. Although the approach was experimentally demonstrated just in two classical SET assays (DPPH and ABTS), the results could be directly expanded in future to other types of classical SET assays. The methodology proposed is more complex than some relatively common approaches; nevertheless we believe that it is free of the controversial aspects listed above. Statistically consistent responses of null, synergy and antagonism effects were found when characterizing the interactions between several pairs of individual and complex mixtures of chemical antioxidant agents.     

Chloroacetanilide herbicide metabolites in Wisconsin groundwater: 2001 survey results

A survey of agricultural chemicals in Wisconsin groundwater was conducted between October 2000 and April 2001 to obtain a current picture of agricultural chemicals in groundwater used for private drinking water. A stratified, random sampling procedure was used to select 336 sampling locations. Water from private drinking water wells randomly selected from within the 336 sampling locations was analyzed for 18 compounds including herbicides, herbicide metabolites, and nitrate. This report focuses on the frequency and concentration of chloroacetanilide herbicides and their metabolites. Analysis of data resulted in an estimated proportion of 38+/-5.0% of wells that contained detectable levels of a herbicide or herbicide metabolite. The most commonly detected compound was alachlor ESA with a proportion estimate of 28+/-4.6%. Other detected compounds in order of prevalence were metolachlor ESA, metolachlor OA, alachlor OA, acetochlor ESA, and parent alachlor. Estimates of the mean concentration for the detects ranged from 0.15+/-0.082 microg/L for acetochlor ESA to 1.8+/-0.60 microg/L for alachlor OA. Water quality standards have not been developed for these chloroacetanilide herbicide metabolites. The results of this survey emphasize the need for toxicological assessments of herbicide metabolite compounds and establishment of water quality standards at the state and federal levels.     

Quantitative risk-based approach for improving water quality management in mining

The potential environmental threats posed by freshwater withdrawal and mine water discharge are some of the main drivers for the mining industry to improve water management. The use of multiple sources of water supply and introducing water reuse into the mine site water system have been part of the operating philosophies employed by the mining industry to realize these improvements. However, a barrier to implementation of such good water management practices is concomitant water quality variation and the resulting impacts on the efficiency of mineral separation processes, and an increased environmental consequence of noncompliant discharge events. There is an increasing appreciation that conservative water management practices, production efficiency, and environmental consequences are intimately linked through the site water system. It is therefore essential to consider water management decisions and their impacts as an integrated system as opposed to dealing with each impact separately. This paper proposes an approach that could assist mine sites to manage water quality issues in a systematic manner at the system level. This approach can quantitatively forecast the risk related with water quality and evaluate the effectiveness of management strategies in mitigating the risk by quantifying implications for production and hence economic viability.     

Ultrasonic velocity measurements in ethanol–water and methanol–water mixtures

In this study, ultrasonic velocity measurements were used to estimate the alcohol type and volume concentration in water–alcohol binary mixtures. Varying mixtures of ethanol in water and methanol in water were prepared and the ultrasonic velocities for each concentration level were measured between 10 and 50 °C. Results of the statistical analyses indicated that ultrasonic velocity measurements can be used to distinguish between ethanol and methanol in a water–alcohol binary mixture and to estimate the alcohol concentration level. The results were validated by testing three commercial liquids with a known ethanol concentrations and one commercial liquid with known methanol concentration.     

Fate of endocrine-disruptor, pharmaceutical, and personal care product chemicals during simulated drinking water treatment processes

The potential occurrence of endocrine-disrupting compounds (EDCs) as well as pharmaceuticals and personal care products (PPCPs) in drinking water supplies raises concern over the removal of these compounds by common drinking water treatment processes. Three drinking water supplies were spiked with 10 to 250 ng/L of 62 different EDC/ PPCPs; one model water containing an NOM isolate was spiked with 49 different EDC/PPCPs. Compounds were detected by LC/MS/MS or GC/MS/MS. These test waters were subjected to bench-scale experimentation to simulate individual treatment processes in a water treatment plant (WTP). Aluminum sulfate and ferric chloride coagulants or chemical lime softening removed some polyaromatic hydrocarbons (PAHs) but removed <25% of most other EDC/ PPCPs. Addition of 5 mg/L of powder activated carbon (PAC) with a 4-h contact time removed 50% to >98% of GC/ MS/MS compounds (more volatile) and 10% to >95% of LC/ MS/MS compounds (more polar); higher PAC dosages improved EDC/PPCP removal. EDC/PPCP percentage removal was independent of the initial compound concentration. Octanol-water partition coefficients served as a reasonable indicator of compound removal under controlled PAC test conditions, except for EDC/PPCPs that were protonated or deprotonated at the test pH and some that contained heterocyclic or aromatic nitrogen. Separate chlorine or ozone experiments decreased the EDC/PPCP initial concentration by <10% to >90%; EDC/PPCPs were likely transformed to oxidation byproducts. Ozone oxidized steroids containing phenolic moieties (estradiol, ethynylestradiol, or estrone) more efficiently than those without aromatic or phenolic moieties (androstenedione, progesterone, and testosterone). EDC/PPCP reactivity with oxidants were separated into three general groups: (1) compounds easily oxidized (>80% reacted) by chlorine are always oxidized at least as efficiently by ozone; (2) 6 of the -60 compounds (TCEP, BHC, chlordane, dieldrin, heptachlor epoxide, musk ketone) were poorly oxidized (<20% reacted) by chlorine or ozone; (3) compounds (24 of 60) reacting preferentially (higher removals) with ozone rather than chlorine. Conventional treatment (coagulation plus chlorination) would have low removal of many EDC/PPCPs, while addition of PAC and/or ozone could substantially improve their removals. Existing strategies that predict relative removals of herbicides, pesticides, and other organic pollutants by activated carbon or oxidation can be directly applied for the removal of many EDC/PPCPs, but these strategies need to be modified to account for charged (protonated bases or deprotonated acids) and aliphatic species. Some compounds (e.g., DEET, ibuprofen, gemfibrozil) had low removals unless ozonation was used. Other compounds had low removals by all the WTP processes considered (atrazine, iopromide, meprobamate, TCEP), and removal processes capable of removing these types of compounds should be investigated.     

Assessing the safety of co-exposure to food packaging migrants in food and water using the maximum cumulative ratio and an established decision tree

Food contact materials can release low levels of multiple chemicals (migrants) into foods and beverages, to which individuals can be exposed through food consumption. This paper investigates the potential for non-carcinogenic effects from exposure to multiple migrants using the Cefic Mixtures Ad hoc Team (MIAT) decision tree. The purpose of the assessment is to demonstrate how the decision tree can be applied to concurrent exposures to multiple migrants using either hazard or structural data on the specific components, i.e. based on the acceptable daily intake (ADI) or the threshold of toxicological concern. The tree was used to assess risks from co-exposure to migrants reported in a study on non-intentionally added substances (NIAS) eluting from food contact-grade plastic and two studies of water bottles: one on organic compounds and the other on ionic forms of various elements. The MIAT decision tree assigns co-exposures to different risk management groups (I, II, IIIA and IIIB) based on the hazard index, and the maximum cumulative ratio (MCR). The predicted co-exposures for all examples fell into Group II (low toxicological concern) and had MCR values of 1.3 and 2.4 (indicating that one or two components drove the majority of the mixture’s toxicity). MCR values from the study of inorganic ions (126 mixtures) ranged from 1.1 to 3.8 for glass and from 1.1 to 5.0 for plastic containers. The MCR values indicated that a single compound drove toxicity in 58% of the mixtures. MCR values also declined with increases in the hazard index for the screening assessments of exposure (suggesting fewer substances contributed as risk potential increased). Overall, it can be concluded that the data on co-exposure to migrants evaluated in these case studies are of low toxicological concern and the safety assessment approach described in this paper was shown to be a helpful screening tool.     

热加工食物中糠醛类化合物的剂量安全与减控研究进展

糠醛类化合物作为美拉德反应的中间过程产物之一,在各类热加工食品中广泛存在,其中羟甲基糠醛和糠醛是最常见的2种糠醛类化合物,而反应物种类、加工方式、贮藏条件、水分活度、pH等因素都会影响其产生与积累。目前围绕糠醛类化合物展开的安全性报道并不多见且并未得出一致的结论,少量报道指出了低浓度糠醛类化合物的有益作用和高浓度的不良影响。基于糠醛类化合物在食物中分布的广泛性、多样性,以及潜在的安全风险,考虑到食物中糠醛类化合物的过量暴露可能会给人体带来健康风险,因此有必要对其进行系统的安全性评价并对其含量加以减控。本文旨在归纳包括乳制品在内的各种热加工食物中糠醛类化合物的分布情况,围绕国内外糠醛类化合物的安全性研究现状、减控技术展开综述,以期为食品质量安全控制提供理论参考。     

PCR detection of specific pathogens in water: a risk-based analysis

The relative concentration of pathogens in water samples collected from storm drains and adjacent surfaces was evaluated using established PCR-based protocols. Out of the 58 samples collected from 21 different storm drains, 22% were PCR positive for Escherichia coli ETEC, Salmonella, or adenovirus. The risk of swimming related illnesses associated with detection of E. coli ETEC and Salmonella ranged from 0.39 to 30:100 000 and 0.3-25:1000, respectively. The detection limit corresponding to a negative-PCR result was evaluated in reference to water quality standards developed using a risk-based approach that integrates human dose-response data with acceptable levels of risk promulgated by the U.S. EPA for recreational contact. The percent of samples with an acceptable detection limit ranged from 0% for Giardia lamblia and Shigella to 100% for E. coli ETEC. The principal factor influencing the detection limit of G. lamblia and Shigella was sample volume. The principal factor influencing the detection limit of the remaining bacteria and protozoa, including E. coli O157:H7, Salmonella, and Cryptosporidium parvum, was the presence of inhibitory compounds in the purified nucleic acid extracts. Both recovery and inhibition adversely impacted the detection limit of viruses. Ambient water quality standards based on the occurrence of specific pathogens enumerated with PCR-based assays could serve as a method of evaluating the biological quality of water but only after significant improvements in filtration and purification protocols. The risk-based methodology developed in this study can be used to evaluate future improvements in filtration and purification protocols.     

Use of duplex polymerase chain reaction (duplex-PCR) technique to identify bovine and water buffalo milk used in making mozzarella cheese

Molecular biology techniques have been used for species identification in food of animal origin in relatively recent years. A polymerase chain reaction (PCR) based method, the multiplex PCR, was recently applied to species identification in meat and meat products. It allows co-amplification of separate regions of a single gene or specific fragments, each typical of a different animal species in a single PCR reaction, using different pairs of primers in the same reaction mix. In the present paper, the duplex-PCR technique is proposed to identify bovine and water buffalo DNA in a single PCR assay in milk and mozzarella cheese (a typical Italian cheese, originally made from pure water buffalo milk). Because of its lower cost, undeclared bovine milk is added to water buffalo milk for making different kinds of mozzarella cheese. The results of this experiment indicate the applicability of this method, which showed an absolute specificity for the two species and a high sensitivity even down to low DNA concentrations (1 pg). In bovine and water buffalo mixtures of both milk and mozzarella cheese, the minimum concentration tested was 1% of bovine in water buffalo milk and water buffalo in bovine milk. The importance of the somatic cell content in raw milk is also discussed with special reference to the evaluation of mixtures (milk or cheese) of the two species.     

Continuous subcritical water extraction as a useful tool for isolation of edible essential oils

A method for extraction of oregano oil based on the use of subcritical water is proposed. Ground oregano (ca. 1.8 g accurately weighed) was extracted with water at 2.0 MPa, 125 °C and 1 ml min⁻¹ for 24 min. The extracted compounds were removed from the aqueous extract by a single extraction with 4 ml hexane, determined by gas-chromatography-flame ionisation (GC-FID) and identified by mass spectrometry (MS). Hydrodistillation was performed on 30 g of ground oregano with 500 ml water for 3 h for comparison of the results with those provided by the proposed method. The subcritical water extraction-based method is clearly quicker and more efficient than the conventional: yields from the former for eight of the 11 major compounds in the extract are higher after 15-min extraction than after hydrodistillation for 3 h. This enables substantial cost savings of both energy and raw material. In addition, the proposed method has the possibility of manipulating the composition of the oil and thus its quality. The aqueous-oil extract was investigated for essential oil preparative purposes and several fast, cheap and clean alternatives for breaking the emulsion and separating the phases are proposed.     

微萃取技术在水中土霉味化合物检测的应用

土霉味是国内外饮用水处理中最常见的问题之一,它通常与微生物活动有关。虽然土霉味化合物的浓度非常低(ng/L),但仍然达到了人类的感知阈值。因此为了检测这些低浓度的土霉味化合物就必须采用高灵敏度、高选择性的方法进行富集处理。本文综述了吸附微萃取、液相微萃取等微萃取技术在水中土霉味化合物检测的研究进展,为提高水中土霉味化合物检测提供借鉴。微萃取效率主要受萃取纤维的种类、萃取模式、添加无机盐的浓度、萃取温度和萃取时间等因素的影响。微萃取是最近发展起来的一种新型样品前处理技术,该方法操作简单、成本低、富集效率高、所需有机溶剂用量极少,是一种环境友好的萃取新技术,可与气相色谱、液相色谱等仪器联用。     

Effect of organic complexation on copper accumulation and toxicity to the estuarine red macroalga Ceramium tenuicorne: a test of the free ion activity model

Current water quality criteria (WQC) regulations on copper toxicity to biota are still based on total dissolved (<0.4 μm membrane filter) copper concentrations with a hardness modification for freshwaters. There are however ongoing efforts to incorporate metal speciation in WQC and toxicity regulations (such as the biotic ligand model-BLM) for copper and other metals. Here, we show that copper accumulation and growth inhibition of the Baltic macroalga Ceramium tenuicorne exposed to copper in artificial seawater at typical coastal and estuarine DOC concentrations (similar to 2-4 mg/L-C as fulvic acid) are better correlated to weakly complexed and total dissolved copper concentrations rather than the free copper concentration [Cu2+]. Our results using a combination of competitive ligand exchange-adsorptive cathodic stripping voltammetry (CLE-ACSV) measurements and model calculations (using visual MINTEQ incorporating the Stockholm Humic Model) show that copper accumulation in C. tenuicorne only correlates linearly well to [Cu2+] at relatively high [Cu2+] and in the absence of fulvic acid. Thus the FIAM fails to describe copper accumulation in C. tenuicorne at copper and DOC concentrations typical of most marine waters. These results seem to indicate that at ambient total dissolved copper concentration in coastal and estuarine waters, C. tenuicorne might be able to access a sizable fraction of organically complexed copper when free copper concentration to the cell membrane is diffusion limited.     

Variability of herbicide losses from 13 fields to surface water within a small catchment after a controlled herbicide application

Diffuse losses from agricultural fields are a major input source for herbicides in surface waters. In this and in a companion paper, we present the results of a comprehensive field study aimed at assessing the overall loss dynamics of three model herbicides (i.e., atrazine, dimethenamid, and metolachlor) from a small agricultural catchment (2.1 km2) and evaluating the relative contributions of various fields having different soil and topographical characteristics. An identical mixture of the three model herbicides as well as an additional pesticide for identification of a given field were applied within 12 h on 13 cornfields (total area approximately 12 ha), thus ensuring that the herbicides were exposed to identical meteorological conditions. After the simultaneous application, the concentrations of the compounds were monitored in the soils and at the outlets of three subcatchments containing between 4 and 5 cornfields each. Particular emphasis was placed on the two rain events that led to the major losses of the herbicides. The rank orders of herbicide dissipation in the soils and of the compound-specific mobilization into runoff were the same in all three subcatchments and were independent of the field characteristics. In contrast, the field properties caused the relative losses from two subcatchments to differ by up to a factor of 56 during the most important event, whereas compound-specific differences of the three neutral herbicides caused the losses to vary only by a factor of 2 during the same event. The enormous spatial variability was mainly caused by factors influencing the fraction of rain that was lost to surface water by fast transport mechanisms. Thus, the key factors determining the spatially variable herbicide losses were the permeability of the soils, the topography, and the location of subsurface drainage systems. These results illustrate the large potential to reduce herbicide losses by avoiding application on risk areas.     

Adsorption of aromatic compounds from water by treated carbon materials

Carbon materials with different textural and surface chemistry properties have been studied to analyze their behavior in removing aromatic compounds (phenol, o-chlorophenol, p-nitrophenol, aniline, and phenol compound mixtures) from water. A mesoporous high surface area graphite and a microporous activated carbon with (HSAGox and ACox) and without (HSAGT and ACT) oxygen surface groups, were used as adsorbents. Apparent surface areas, surface oxygen groups, and zero points of charge have been determined. The adsorption behavior of single compounds on ACT depends on the relation between the molecular and the pore sizes. The aniline, the nitrophenol, and the chlorophenol interact with the oxygen surface groups of oxidized graphite, while there is no evidence of any type of interaction of the phenol with these groups. The adsorption of the organic compound mixtures on the thermally treated samples is determined by the acid-base character of the adsorbate-adsorbent, whereas on the oxidized carbons, the controlling forces are the specific interactions between organic molecules and the oxygenated groups. Selectivity coefficients for the different mixtures are presented over the entire range of adsorption.     

VOCs,pesticides, nitrate,and their mixtures in groundwater used for drinking water in the United States

Samples of untreated groundwater from 1255 domestic drinking-water wells and 242 public supply wells were analyzed as part of the National Water-Quality Assessment Program of the U.S. Geological Survey between 1992 and 1999. Wells were sampled to define the regional quality of the groundwater resource and, thus, were distributed geographically across large aquifers, primarily in rural areas. For each sample, as many as 60 volatile organic compounds (VOCs), 83 pesticides, and nitrate were analyzed. On the basis of previous studies, nitrate concentrations as nitrogen > or = 3 mg/L were considered to have an anthropogenic origin. VOCs were detected more frequently (44%) than pesticides (38%) or anthropogenic nitrate (28%). Seventy percent of the samples contained at least one VOC, pesticide, or anthropogenic nitrate; 47% contained at least two compounds; and 33% contained at least three compounds. The combined concentrations of VOCs and pesticides ranged from about 0.001 to 100 microg/L, with a median of 0.02 microg/L. Water from about 12% of the wells contained one or more compounds that exceeded U.S. Environmental Protection Agency drinking-water standards or human health criteria, primarily because of nitrate concentrations exceeding the maximum contaminant level in domestic wells. A mixture is defined as a unique combination of two or more particular compounds, regardless of the presence of other compounds that may occur in the same sample. There were 100 mixtures (significantly associated with agricultural land use) that had a detection frequency between 2% and 19%. There were 302 mixtures (significantly associated with urban land use) that had a detection frequency between 1% and <2%. Only 14 compounds (seven VOCs, six pesticides, and nitrate) contributed over 95% of the detections in these 402 mixtures; however, most samples with these mixtures also contain a variety of other compounds.     

Thermodynamic compatibility of proteins in aqueous media. Part. I. Phase diagrams of some water – protein A – protein B systems

The thermodynamic compatibility of proteins belonging to different classes according to Osborne has been investigated in aqueous media. Phase equilibrium for water - ovalbumin - soybean globulin fraction, water - ovalbumin - casein, water - casein - gliadin and water - casein - soybean globulin fraction systems has been investigated. The data obtained were analysed according to the theoretical concepts of Scott, Patterson and Prausnitz concerning the effect of polymer molar masses and the solvent quality on the phase equilibrium in similar systems. The analysis performed indicates that these concepts can be applied to the water - protein A - protein B systems. The phase equilibrium in water - protein A - protein B systems has some distinctive features as compared to that in systems containing two synthetic polymers in the single solvent. Firstly, proteins are usually compatible in a broader concentration range as compared to common polymers. Moreover, the separation of water - protein A - protein B systems into two phases often results in a considerable concentration of one of the protein components. Apparently, the latter fact can be associated with the marked difference in the interaction parameter of proteins belonging to different classes with the solvent, and, hence, with the marked difference in the hydrophilicity of the proteins investigated.