Determination of chemical oxygen demand (COD) using an alternative wet chemical method free of mercury and dichromate.

Worldwide, the standard methods for the determination of the important wastewater parameter chemical oxygen demand (COD) are still based on the use of the hazardous chemicals, mercury sulfate and chromium(VI). However, due to their properties they are meanwhile classified as "priority pollutants" and shall be phased out or banned in the frame of REACH (current European Chemical Law: Registration, Evaluation, Authorization and restriction of Chemicals) by the European Union. Hence, a new wet-chemical method free of mercury and chromium(VI) was developed. Manganese(III) was used as oxidant and silver nitrate for the removal of chloride ions. The quantification was performed by back titration of manganese(III) with iron(II) as done in the standard method. In order to minimize losses of organic substances during the precipitation of silver chloride, suspended and colloid organic matter had to be separated by precipitation of aluminum hydroxide in a first step. In these cases, two fractions, one of the suspended and colloid matters and a second of the dissolved organic substances, are prepared and oxidized separately. The method was tested with potassium hydrogen phthalate (KHP) as conventional COD reference substance and different types of wastewater samples. The oxidation of KHP was reproducible in a COD range of 20-500 mg/L with a mean recovery rate of 88.7% in comparison to the standard COD method (DIN 38409-41). Also in presence of 1000 mg/L chloride a recovery rate of 84.1% was reached. For a series of industrial and municipal wastewater samples a high correlation (R2 = 0.9935) to the standard method with a mean recovery rate of 78.1% (±5.2%) was determined. Even though the results of the new method are not 100% of the standard method, its high correlation to the standard method and reproducibility offers an environmentally benign alternative method with no need to purchase new laboratory equipment.

Effects of long-term irrigation with untreated municipal wastewater on soil properties and crop quality.

Irrigating crops with untreated wastewater leads to elevated concentrations of heavy metals both in soil and cultivated crops. The current study was designed to determine heavy metal (i.e., Pb, Cd, Cr, Cu, Ni, Zn, Hg) accumulation in Konya soils in selected nine sites irrigated with wastewater for over 40 years. Non-irrigated soil samples and soil samples irrigated with well water were taken as control samples. Transport of these pollutants to the wheat samples cultivated in the investigated site was also examined. The obtained results reveal that high alkaline properties and clay structure of Konya soil reduce the mobility of contaminants and cause accumulation in the top layer of soil. Intense effect of wastewater irrigation on soil EC was determined. The highest concentrations of Pb, Cr, Cu, Cd, Zn, Ni, and Hg in wastewater irrigated soil were 5.32, 37.1, 31.5, 11.4, 91.5, 134, and 0.34 mg kg(-1), respectively. Wastewater irrigated soils were strongly polluted by means of Cd (8.23-11.6 mg kg(-1)) and moderately to strongly polluted by means of Ni (47.7-134 mg kg(-1)), exceeding Maximum Admissible Concentrations for Trace Elements in Agricultural Soils and Sewage Sludge Regulation limit values of Turkey. Maximum concentrations found for Pb, Cr, Cu, Cd, Zn, and Ni in wastewater irrigated wheat grain were 8.44, 1.30, 9.10, n.d, 29.31, and 0.94 mg kg(-1), respectively. Besides, Hg was not detected in any samples of wheat grain. Based on the regulation of Turkish Food Codex, Pb contamination in wheat samples grown in the sampling site was evidenced.

Application of simple and low-cost toxicity tests for ecotoxicological assessment of industrial wastewaters.

The objective of this study was to identify and to apply appropriate biotests having the advantages of being highly sensitive, easy to run, relatively inexpensive and able to substitute fish toxicity tests due to ethical reasons of animal welfare. To perform an ecotoxicological assessment of industrial wastewaters, different microbiotests were conducted to substitute the fish toxicity test with Lebistes reticulatus through Vibrio fischeri, Thamnocephalus platyurus, Daphnia magna, Lemna minor and Lepidium sativum representing different trophic levels in the aquatic and terrestrial ecosystems. Also, Algaltox F(TM) with Pseudokirchneriella subcapitata and Protox F(TM) with Tetrahymena thermophila tests were carried out. However, they could not be applied successfully for the wastewater samples. Wastewater samples from seven different industrial zones comprising different industries were subjected to characterization through measuring their physical-chemical parameters and their toxicity versus the above-mentioned organisms. T. platyurus, D. magna and L. reticulatus were the most sensitive test organisms investigated for the wastewaters. Considering toxic unit values, generally wastewater samples were toxic according to Thamnotox F(TM), Daphtox F(TM) and fish toxicity tests. As an important outcome, it was concluded that Daphtox F(TM) and Thamnotox F(TM) could be a good alternative for the fish toxicity test, which is so far the sole toxicity test accepted by the Turkish Water Pollution Control Regulation.

Effects of insecticide formulations used in cotton cultivation in West Africa on the development of flat-backed toad tadpoles (Amietophrynus maculatus).

In the West African savanna zone, traditional subsistence farming increasingly shifts to cash crop farming and in particular to cotton cultivation, which is accompanied by application of pesticides. Increasing use of pesticides by smallholder farmers is suspected to have negative effects on non-target organisms. In this study, possible pesticide impact on the development of tadpoles was investigated. Two insecticide formulations used in cotton cultivation in Benin were compared: Cotofan® (active ingredient (a.i.): α- and ß-endosulfan) and Tihan® (a.i.: spirotetramat and flubendiamide). Tadpoles of the widespread species Amietophrynus maculatus were kept in small water basins with increasing insecticide concentrations (1, 10 and 100 µg a.i./L) over a period of 28 days. Tadpoles showed reduced survival at the highest endosulfan concentrations (100 µg/L). Survival of tadpoles undergoing metamorphosis was not influenced by Tihan®. Endosulfan in concentrations of 10 and 100 µg/L negatively impacted the movement of the tadpoles which was not the case for the mixture of spirotetramat and flubendiamide. Time to metamorphosis was not significantly different in the various treatments. Tail length of tadpoles was significantly shorter in Cotofan® treatments compared to controls. Pesticide residues in the tadpoles were relatively low after keeping them in concentrations of 1 and 10 µg a.i./L (25 and 26 µg/kg wet weight (w/w) for the sum of α-endosulfan, ß-endosulfan and endosulfan sulphate and below the detection limits for flubendiamide and spirotetramat). For the 100 µg a.i./L treatments, 1,600 µg/kg w/w was found of α-endosulfan, ß-endosulfan and endosulfan sulphate together in the survived tadpoles and 21 µg/kg w/w of flubendiamide.

Insecticide residues in bats along a land use-gradient dominated by cotton cultivation in northern Benin, West Africa.

Many regions in Africa are currently being converted from subsistence to cash crop farming such as cotton. Agricultural intensification is usually accompanied by increased use of pesticides, which can have an impact on non-target organisms. Bats are particularly sensitive to insecticide loads while providing substantial ecosystem services as predators of herbivorous insects. In this study, pesticide residues in bats in a landscape in northern Benin were investigated, which spanned a land use gradient from an agricultural zone dominated by cotton farms, through a buffer zone, and into a national park. Insecticides used in cotton cultivation, such as endosulfan, chlorpyrifos, flubendiamide, and spirotetramat, as well as persistent insecticides such as bis(4-chlorophenyl)-1,1,1-trichloroethane (DDT), lindane, and aldrine, were analysed. Insecticide residues detected in bats comprised DDT, endosulfan, and their corresponding transformation products. Maximum concentrations in the sampled bats were 11.2 mg/kg lipid of p,p'-DDE (median: 0.0136 mg/kg lipid) and 0.797 mg/kg lipid of ß-endosulfan (median: below detection limit [DL]). While insecticide concentrations were below lethal concentrations our data suggest that DDT had probably been recently used in the study region, and larger scale use would pose an increased risk for bat populations due to the high biomagnification of DDT.

An amperometric acetylcholine biosensor based on a conducting polymer.

An amperometric acetylcholine biosensor was prepared by the generation of the conducting polymer poly(4-(2,5-di(thiophen-2-yl)-1H-pyrrol-1-yl)benzenamine) (poly(SNS-NH2)) on graphite electrodes. For pesticide detection, the enzymes acetylcholinesterase (AChE) and choline oxidase (ChO) were co-immobilized onto the conducting polymer poly(SNS-NH2) films using covalent binding technique. Electrochemical polymerization was carried out using a three-electrode cell configuration via cyclic voltammetry. Characterization of resulting acetylcholine biosensor was done in terms of optimum pH, enzyme loading, range of linear response and shelf-life. Linear range was 0.12-10mM and shelf-life 4 weeks. Sensitivity was calculated as 2.19µAmM(-1)cm(-2). The designed biosensor was tested for the determination of paraoxon-ethyl in spiked tap water samples. The results were compared with a conventional quantification method using HPLC-DAD. Linear correlation of the quantification results with both methods (R(2)=0.998) was obtained.

Risk posed by chlorinated organic compounds in Abu Qir Bay, East Alexandria, Egypt.

INTRODUCTION: In Egypt, the picture of threats to humans and the environment from the exposure to organic pollutants is still incomplete. Thus the objectives of this study were to assess the occurrence and distribution of polychlorinated biphenyls (PCBs), organochlorine pesticides, and chlorpyrifos in sediments and mussels of Abu Qir Bay and their risks for environment and human health. MATERIALS AND METHODS: Twenty-three different compounds organochlorines were determined in 20 surfacial sediment and 10 mussel samples by gas chromatography-electron capture detector. A Screening Level Ecological Risk Assessment (SLERA) and a Human Health Risk Assessment (HHRA) were performed with the data. RESULTS AND DISCUSSION: ΣDDT (DDT, DDE, DDD) (average concentration 27 µg/kg dw) dominated the detected organic pollutants in the sediments, followed by CHLs (chlordane, heptachlor, heptachloro epoxide), hexachlorocyclohexane, chlorpyrifos, endosulfane, dieldrine, Σ6 PCBs, aldrine, hexachlorobenzene, pentachlorobenzene, methoxychlor, and mirex. In general, concentrations of Σ6 PCBs in mussels were higher than their corresponding sediment concentrations reflecting their relatively high bioavailability and bioaccumulative potential. However, concentrations of the organochlorine pesticides in mussels were lower than their corresponding sediment samples. Nevertheless, the SLERA on the bay sediments revealed that adverse ecological effects to benthic species are expected to occur whereas the HHRA showed that adverse health effects are not expected to occur from the consumption of the mussels. CONCLUSIONS: With the help of a SLERA, it was possible to indicate which class of chlorinated organic compounds is of highest concern to assess and to improve the environmental quality of the bay. Monitoring of organochlorines and chlorpyrifos would be needed to control the future trend of pollution.

Risk assessment of polycyclic aromatic hydrocarbons in a Mediterranean semi-enclosed basin affected by human activities (Abu Qir Bay, Egypt).

The contamination of sediments and mussels sampled from Abu Qir Bay by polycyclic aromatic hydrocarbons (PAHs) was investigated. Concentrations of PAHs recorded in the bay sediments ranged from less than MDL to 2660 microg/kg dw. In general, concentrations of PAHs in mussels were higher than their corresponding sediment concentrations reflecting their great bioavailability (242-3880 microg/kg dw). The highest concentration was observed in the western part of the bay, a location affected by intensive shipping activities. The distribution pattern of PAHs was similar for mussels and sediments, particularly for sediments characterized by high contamination level, and they were dominated by the high molecular weight PAHs (4-6-rings). Applying different PAHs ratios, it was found that PAHs originated predominantly from the pyrogenic source either from the combustion of grass, wood and coal (majority of the samples) or from petroleum combustion (harbour area). The output of a Screening Level Ecological Risk Assessment (SLERA) on the bay sediments revealed that adverse ecological effects to benthic organisms are expected to occur in only one sample, and thus PAHs are not considered as contaminants of concern in Abu Qir Bay. Also adverse health effects are not expected to occur from the consumption of the investigated mussels with respect to PAHs in Abu Qir Bay.