Spatial distribution of legacy pesticides in river sediment from the Republic of Moldova

Historical use of organochlorine pesticides (OCPs) in the Republic of Moldova could pose a potential risk for the aquatic environment due to the persistence, bioaccumulation and toxic properties of these environmental pollutants. However, knowledge on environmental concentrations of legacy OCPs in Moldova is limited. In this study, surface sediment from the two main rivers; Dniester (8 sites, n = 15) and Prut (6 sites, n = 12), and two tributary rivers; Bîc (11 sites, n = 11) and Răut (6 sites, n = 6), were collected during 2017-2018 and analyzed for hexachlorocyclohexanes (HCHs), dichlorodiphenyltrichloroethanes (DDTs) and their transformation products (DDDs and DDEs) using gas chromatography coupled to mass spectrometry (GC-MS/MS). Sediment concentrations of Ʃ₆DDX (1.9-140 ng g^-1 dry weight (dw)) and Ʃ₄HCHs (n.d-2.5 ng g^-1 dw) were found. In the big rivers, the average Ʃ₆DDX concentration (18 ng g^-1 dw) were 35 times higher than Ʃ₄HCHs (0.51 ng g^-1 dw). Whereas, in the small rivers the average Ʃ₆DDX concentration (32 ng g^-1 dw) was approximately 41 times higher than Ʃ₄HCHs (0.77 ng g^-1 dw). Compared to previous studies from Eastern Europe, the sediment levels were generally similar as found in Moldova's neighboring countries (Romania and Ukraine). Overall, the contamination profile indicates long-term ageing of OCPs used in the past in the agricultural sector. Less than half of the sites (45%) had levels that pose a potential risk for benthic organisms. Hence, further work is needed to determine the bioaccumulation of OCPs in the aquatic food web in this region and the associated risks to ecosystems and human health.

Lactic acid fermentation of human urine to improve its fertilizing value and reduce odour emissions

During storage of urine, urea is biologically decomposed to ammonia, which can be lost through volatilization and in turn causes significant unpleasant smell. In response, lactic acid fermentation of urine is a cost-effective technique to decrease nitrogen volatilization and reduce odour emissions. Fresh urine (pH = 5.2-5.3 and NH₄⁺-N = 1.2-1.3 g L^-1) was lacto-fermented for 36 days in closed glass jars with a lactic acid bacterial inoculum from sauerkraut juice and compared to untreated, stored urine. In the lacto-fermented urine, the pH was reduced to 3.8-4.7 and the ammonium content by 22-30%, while the pH of the untreated urine rose to 6.1 and its ammonium content increased by 32% due to urea hydrolysis. The concentration of lactic acid bacteria in lacto-fermented urine was 7.3 CFU ml^-1, suggesting that urine is a suitable growth medium for lactic acid bacteria. The odour of the stored urine was subjectively perceived by four people to be twice as strong as that of lacto-fermented samples. Lacto-fermented urine induced increased radish germination compared to stored urine (74-86% versus 2-31%). Adding a lactic acid bacterial inoculum to one week old urine in the storage tanks in a urine-diverting dry toilet reduced the pH from 8.9 to 7.7 after one month, while the ammonium content increased by 35%, probably due to the high initial pH of the urine. Given that the hydrolyzed stale urine has a high buffering capacity, the lactic acid bacterial inoculum should be added to the urine storage tank of a UDDT before urine starts to accumulate there to increase the efficiency of the lactic acid fermentation.

Assessment of copper and zinc levels in fish from freshwater ecosystems of Moldova

PURPOSE

The aim of this work was to assess the levels of copper and zinc in fish from the main freshwater ecosystems of Moldova, in relation with species, habitat, age, sex, season, and development stage.

METHODS

Fish from Cyprinidae and Percidae families (Cyprinus carpio, Carassius auratus gibelio, Rutilus rutilus heckeli, Abramis brama, Aristichthys nobilis, Hypophtalmichthys molitrix, Sander lucioperca) were collected from Prut and Dniester rivers, Cuciurgan, Dubasari, and Costesti-Stanca reservoirs, and ponds of farms in the Dniester delta. The Cu and Zn content of fish tissues (skeletal muscles, liver, gonads, gills, skin, and scales) was determined by flame atomic absorption spectrophotometer AAS-3, of water by graphite furnace HGA 900 of AAnalist 400.

RESULTS

The level of heavy metals accumulation in muscles of immature fish follows their dynamics in water. The highest concentration of zinc was registered in the gonads of mature fish, and of copper-in the liver. The lowest Cu and Zn contents were recorded in the muscles and are in the United Nations Food and Agriculture Organization safety-permissible levels for human consumption. Cu and Zn contents in muscles of fish depend on specimen age. Their level in fish gonads was sharply increasing during pre-spawning period. During the early developmental stages, the metal concentration in fish eggs and larvae varies within wide limits, but the accumulation pattern is similar in the investigated species.

CONCLUSIONS

The fish represent one of the most indicative factors for the estimation of trace metals pollution in freshwater systems and this is important not only for monitoring purposes, but also for the fish culture ones.

Occurrence of pesticides, polychlorinated biphenyls (PCBs), and heavy metals in sediments from the Dniester River, Moldova

The aim of this study was to evaluate sediments of the Dniester River, in the former Soviet republic of Moldova, for the occurrence of agricultural pesticides, polychlorinated biphenyls (PCBs), and heavy metals. In October 2001, sediment samples were collected at three locations of the Dniester River: upstream, downstream, and at the tributary of the River Byk. DDT and its metabolites were observed most frequently. Total DDT sediment concentrations ranged from 8.2 to 34.7 ng/g dry weight with the highest average concentration detected at the tributary location. Heptachlor epoxide (< 0.2-3.0 ng/g dry weight), chlordane (< 0.1-6.1 ng/g dry weight), endrin (< 0.2-2.5 ng/g dry weight), phosalone (< 0.2-1.1 ng/g dry weight), and methylparathion (< 0.2-16.8 ng/g dry weight) were also detected. Total PCB concentrations observed in sediments ranged from 68 to 763 ng/g dry wt. Total average PCB concentrations were significantly (p < or = 0.004) higher for sediments from the downstream sampling sites compared to the upstream samples. Tetra- and trichlorobiphenyls accounted for 84 and 88% of the total residues measured in the downstream and tributary locations, respectively. In contrast, heptachlorobiphenyls were the prevailing homologues in sediments from the upstream sampling site, contributing 51% of the total PCB concentration. Predominant PCB homologues were: trichlorobiphenyl congener 28 and 37, tetrachlorobiphenyl congeners 44, 49, 52, 74, 77, and 81, and heptachlorobiphenyl congener 170. Sediment concentrations of SigmaDDE (19.7 ng/g dry weight) in the tributary, heptachlor epoxide (3.0 ng/g dry weight) in the downstream, and nickel (128-170 microg/g dry weight) in all locations exceeded Probable Effect Levels (PELs) established for sediment quality in fresh water, indicating probable environmental stress and the potential for adverse effects to benthic organisms in the Dniester River.

Evaluation of pesticides and metals in fish of the Dniester River, Moldova

The Dniester River is one of the largest rivers in Eastern Europe and receives input from numerous anthropogenic activities. In October 2001, fish samples (Abramis brama, Rutilus rutilus heckeli, Perca fluviatilis, Chondrostoma nasus, Carassius auratus gibelio, and Cyprinus carpio) were collected and analyzed for metals and various pesticides. Maximum total DDT pesticide concentrations were between 27.7 and 34.2 ng/g wet weight in muscles and gonads, respectively. DDE isomers comprised up to 70% of total DDT measurement in fish tissues, indicating historical rather than recent DDT pollution. Chlordane and lindane were also detected in amounts up to 37 and 76 ng/g wet weight in gonads, respectively. Among organophosphorous pesticides, malathion showed extremely high concentrations--3 microg/g wet weight in muscles and 46 microg/g wet weight in gonads, indicating recent exposure. Copper concentrations in muscles (1.8-7.2 microg/g) exceeded Threshold Effect Concentrations for copper in fish. Detection of high concentrations of malathion and copper in fish tissues indicated potential anthropogenic stress for more sensitive aquatic biota, likely from agricultural sources in the Dniester River.

Effects of salinity on the uptake, biotransformation, and toxicity of dietary seleno-L-methionine to rainbow trout

Selenium (Se) is an element that has been of environmental concern in aquatic systems that drain arid regions heavily used for agricultural purposes. As hypersaline conditions are associated with these ecosystems, this study examined the effect of hypersaline water on the uptake, biotransformation, and toxicity of seleno-L-methionine (SeMe) in juvenile rainbow trout. Fish were acclimated for 5 days to four different salinity regimes (0.5, 6.3, 11.9, 16.8 deciSiemens (dS/m) per meter. To mimic arid agricultural runoff solutes, the water was reconstituted with ions found in drainage water of the San Joaquin River in California. Following 7 days of dietary exposure to 180 mg/kg SeMe, mortality, as well as hepatic selenium concentrations and reduced:oxidized glutathione ratios were measured. Hypersaline conditions protected fish from dietary SeMe toxicity. Fish exposed to 0.5 dS/m water experienced 100% lethality in 2.5 days, whereas fish acclimated to 16.8 dS/m water-only experienced 16.7% mortality, which took 5-7 days to occur. There were no significant differences in hepatic selenium concentrations, but diminishment of reduced glutathione:oxidized glutathione (GSH:GSSG) ratios was observed in SeMe-treated fish held in 0.5 dS/m water. SeMe inhibited flavin-containing monoxygenase catalyzed trimethylamine oxidase activity, but salinity failed to induce expression in trout, indicating an oxygenation of organoselenides may play a minor role in SeMe toxicity.