Persistent organic pollutants (POPs) are a group of 28 toxic compounds of different chemical classes listed in the Stockholm Convention on POPs, which aims to protect the environment and human health .......
Even though the genetic attributes suggest presence of multiple degradation pathways, most of rhodococci are known to transform PCBs only via regular biphenyl (bph) pathway. Using GC-MS analysis, we ...monitored products formed during transformation of 2,4,4′-trichlorobiphenyl (PCB-28), 2,2′,5,5′-tetrachlorobiphenyl (PCB-52) and 2,4,3′-trichlorobiphenyl (PCB-25) by previously characterized PCB-degrading rhodococci Z6, T6, R2, and Z57, with the aim to explore their metabolic pleiotropy in PCB transformations. A striking number of different transformation products (TPs) carrying a phenyl ring as a substituent, both those generated as a part of the bph pathway and an array of unexpected TPs, implied a curious transformation ability. We hypothesized that studied rhodococcal isolates, besides the regular one, use at least two alternative pathways for PCB transformation, including the pathway leading to acetophenone formation (via 3,4 (4,5) dioxygenase attack on the molecule), and a third sideway pathway that includes stepwise oxidative decarboxylation of the aliphatic side chain of the 2-hydroxy-6-oxo-6-phenylhexa-2,4-dienoate. Structure of the identified chlorinated benzoic acids and acetophenones allowed us to hypothesize that the first two pathways were the outcome of a ring-hydroxylating dioxygenase with the ability to attack both the 2,3 (5,6) and the 3,4 (4,5) positions of the biphenyl ring as well as dechlorination activity at both, -ortho and -para positions. We propose that several TPs produced by the bph pathway could have caused the triggering of the third sideway pathway. In conclusion, this study proposed ability of rhodococci to use different strategies in PCB transformation, which allows them to circumvent potential negative aspect of TPs on the overall transformation pathway.
•Tested rhodococci use complex metabolic hub for PCB transformation.•Rhodococci use regular bph pathway in PCB transformation.•Alternative pathways works via production of acetophenones.•Third pathway includes stepwise oxidative decarboxylation of the aliphatic side chain of the HOPDA.•Rhodococci harbor specific ring-hydroxylating dioxygenase with dechlorination ability.
Field experiments were carried out to compare the effect of herbicide application rate on the distribution and persistence of atrazine (ATR), terbuthylazine (TBA), and their dealkylated degradation ...products in two conventionally cultivated cornfield soils: a silt loam soil and a silty clay loam soil, both typical for the crop-producing area of continental Croatia. Herbicides were applied pre-emergence at the registered (R) (1.0–1.5kgha−1), double-registered (2R), and triple-registered (3R) rates. Topsoil (0–30cm) and subsoil (30–60cm) samples were collected periodically during a crop rotation cycle of 17months. Soil microcosm experiments were performed under controlled conditions to investigate the influence of the herbicide application rate on their biodegradation in herbicide-treated cornfield topsoils. The herbicide half-lives (DT50) calculated by using monophasic and biphasic first-order kinetics models were compared. The herbicide sorption intensity in the studied soils was evaluated in terms of the Freundlich sorption isotherm. Under field conditions, TBA was retained within the first 60cm of both agricultural soils at least twice as long as ATR. While ATR residues persisted in soil only until corn harvest (5months), the residues of TBA and its N-deethylated degradation product were still measurable at the end of the crop rotation cycle (17months). The persistence of both herbicides was higher in soil with higher herbicide sorption intensity. ATR and TBA application rates higher than registered generally did not significantly influence the herbicide biodegradation rates or dissipation from the topsoil layers. The enhanced application rate slightly decreased the TBA persistence only in soil exhibiting a rather slow biodegradation. A temperature-leaching potential index for ATR and TBA applied at R rate showed the same leachability class for both herbicides. The leachability class of TBA could be higher than that of ATR in soil with moderate TBA persistence (DT50=30–100days). From an environmental perspective, TBA could pose a similar risk for groundwaters as ATR.
•Atrazine persisted in crop-cultivated soils until corn harvest (5months).•Terbuthylazine persisted in the same soils three times as long as atrazine.•Deethylterbuthylazine was detectable in soils equally long as terbuthylazine.•Higher herbicide application rates may slightly promote their biodegradation in soil.•Longer TBA persistence in soil need not imply lower leaching.
As part of our OPENTOX project, we evaluated the incidence and mass concentrations of multiclass pesticide residues in 23 river/stream water samples collected in urban and agricultural areas of ...northwest Croatia at various points of the pesticide application season in 2015. The study included 16 compounds of five herbicide classes and seven compounds of three insecticide classes. Pesticide residues were accumulated from water by solid-phase extraction and analysed using high performance liquid chromatography with UV-diode array detection and/or gas chromatography-mass spectrometry. Herbicide residues were more common than the insecticide ones, and, as expected, they peaked in the middle of the application season. Metolachlor showed the highest concentrations and was found in 91 % of all samples, followed by terbuthylazine, found in 70 % of the samples. The highest total mass concentration of detected pesticides was measured in the water samples of the Krapina (3992 ng/L) and Sutla (3455 ng/L) collected in rural areas with intensive agriculture. Our findings strongly speak in favour of continued monitoring of surface waters and possibly extending the list of priority water pollutants.
This review summarises our two decades of polychlorinated biphenyl (PCB) monitoring in different marine organisms along the eastern Adriatic Sea. The aim was to gain an insight into the trends of PCB ...distribution in order to evaluate the effectiveness of past and current legislation and suggest further action. Here we mainly focus on PCB levels in wild and farmed Mediterranean mussels, wild and farmed bluefin tuna, loggerhead sea turtles, common bottlenose dolphins, and small pelagic fish. The use of artificial intelligence and advanced statistics enabled an insight into the influence of various variables on the uptake of PCBs in the investigated organisms as well as into their mutual dependence. Our findings suggest that PCBs in small pelagic fish and mussels reflect global pollution and that high levels in dolphins and wild tuna tissues raise particular concern, as they confirm their biomagnification up the food chain. Therefore, the ongoing PCB monitoring should focus on predatory species in particular to help us better understand PCB contamination in marine ecosystems in our efforts to protect the environment and human health.
Methods based on reversed-phase liquid chromatography with UV detection of 4-nitrobenzoyl- or 3,5-dinitrobenzoyl azide derivatives lack in accuracy and stability of derivatives to be applied for ...azide determination in pharmaceutical protein samples with high sodium chloride concentrations. This paper describes a sensitive and selective ion chromatographic method, with simple sample preparation and suppressed conductivity detection, developed for trace determination of azide in protein samples containing sodium chloride in concentrations as high as 11.6
g
L
−1. Anion exchange stationary phase with quaternary alkyl amine functional groups and gradient elution with sodium hydroxide enabled good resolution of anions with similar retention times: azide, bromide and nitrate, as well as chloride whose retention time was shorter than azide's. Anions with high affinity to stationary phase (phosphate and citrate) were also eluted within acceptable analysis time of 32
min. The stability of sample solutions and the method selectivity, accuracy, precision and sensitivity satisfied the validation criteria of international organizations competent for pharmaceutical industry. The detection and quantitation limit ranges of sodium azide in protein samples were 0.007–0.02
mg
L
−1 and 0.02–0.06
mg
L
−1, respectively. Both limits increased with the concentration of sodium chloride.
We studied the occurrence and levels of hexachlorobenzene, α-, β-, and γ-hexachlorocyclohexane, 4,4'-DDT, 4,4'-DDE, 4,4'-DDD, and 17 PCBs (six indicator and eleven other toxicologically significant ...congeners) in PM.sub.10 and/or PM.sub.2.5 particle fractions collected between 2000 and 2003 and in 2010 at a site in the northern residential part of Zagreb, Croatia. Twenty-four-hour particle samples were collected on glass or quartz microfibre filters from approximately 100 m.sup.3 of ambient air per filter. Filters with particles collected over seven consecutive days were combined for ultrasonic extraction with 1: 1 acetone : n-hexane mixture followed by capillary gas chromatography with electron capture detection. In the monitored periods, the mass concentrations of organochlorine compounds in atmospheric particles were characteristic of global environmental pollution and showed a decreasing trend. Local input was observed only for γ-hexachlorocyclohexane. There were no pronounced seasonal variations in the mass fraction levels of any pesticide or PCB in airborne particles. A decreasing trend in the mass concentrations of some compounds with higher air temperatures was mostly related to the lower particle concentrations in warmer seasons and, consequently, to less particle-bound organochlorine compounds in the atmosphere. Keywords: organochlorine pesticides, PM.sub.10, PM.sub.2.5, polychlorinated biphenyls
The recognition of certain herbicides as endocrine disrupting compounds has raised concerns due to their ability to interfere with the normal functioning of the endocrine system, which regulates ...various physiological processes in organisms. The objective of this study was to assess the possible human health risks associated with terbuthylazine and endocrine-disrupting herbicides atrazine, acetochlor, and metolachlor in the drinking, surface, and groundwater of the Zagreb city region, Croatia. We relied on advanced statistical methods and principal component analysis (PCA), which revealed higher levels of atrazine and acetochlor in drinking and groundwater samples and higher presence of metolachlor and terbuthylazine in surface waters. To evaluate the danger to human health, various exposure scenarios have been assessed. The risk of direct human exposure to analyzed herbicides through drinking or bathing with drinking (tap) or groundwater, as well as from recreational activities like swimming in rivers, streams, and lakes, has been quantified. In addition to these direct exposure scenarios, indirect ones based on consumer goods, fruits, and vegetables, treated with surface and groundwater for irrigation, were assessed to investigate the danger to human health. Judging by the reported herbicide levels there was no significant risk of carcinogenic (CR ≤ 1 × 10
−6
) or non-carcinogenic (HI < 1) diseases, not even when we assessed the so-called “cocktail effect” of combined the herbicide exposure in different waters.
The occurrence and distribution of 11 organochlorine pesticides (OCPs) and their degradation products as well as of 17 polychlorinated biphenyl congeners (PCBs) were investigated for the first time ...in sediments of three (Lake Prošće, Lake Kozjak, Lake Kaluđerovac) out of 16 cascading karst lakes within the protected area of the Plitvice Lakes National Park in central Croatia. The 15-cm-long sediment cores were divided for analysis into three 5-cm-long segments. The abundance and levels of sediment-associated OCPs and PCBs were evaluated with respect to sampling location and sediment depth, presumed age of deposition, and organic carbon content. The burden of sediments with OCPs and PCBs decreased downstream with the highest mass fractions measured in the uppermost Lake Prošće (total OCPs 2.72–5.86 μg kg
−1
d.m., total PCBs 0.37–1.78 µg kg
−1
d.m.) and the lowest in Lake Kaluđerovac (total OCPs 0.30–0.58 μg kg
−1
d.m., total PCBs 0.07–0.12 µg kg
−1
d.m.). The predominant organochlorine pollutants were DDT-type compounds (total DDX,
w
= 0.30–5.72 µg kg
−1
d.m.) with
p,p
′-DDE and
p,p
′-DDD accounting for up to 100% and 50%, respectively, of the total DDX. The findings indicated an old input of
p,p
′-DDT that largely converted to its degradation products. The OCP and PCB mass fractions in the Plitvice lake sediments were at trace levels characteristic for preserved pristine natural environments with no or limited anthropogenic impact wherein long-range atmospheric transport is considered as their main source.
The impact of a coal-fired Plomin Power Plant (PPP) in Croatia on PCB soil burden was examined by comparing the occurrence, levels, and profile of PCBs in soil from the PPP with the values determined ...in urban-industrialized soil (Varaždin, Croatia). Soil burden by organochlorine pesticides (OCPs) were also investigated at both locations. Topsoil samples were collected at five distances (100–800 m) along a downwind pollution gradient from the PPP and across the city. The total content of PCBs in 100-m soil was nearly 20-fold the levels found in 800-m soil, which pointed to the PPP as a local source of soil contamination. The PPP soils were dominated by indicator PCB congeners, particularly hexa-homologs. A different profile and mass fraction range of PCBs in soils from PPP and Varaždin area indicated the different sources of contamination. Levels of total PCBs in PPP soils (0.25–19.07 μg kg
−1
) were higher than PCB levels determined in soils from Varaždin (0.29–5.52 μg kg
−1
), partially as a result of higher OC content in PPP soils. PPP soil burden by PCBs corresponded to a lower end of PCB level ranges reported for cities with high population and heavy industry. OCPs were detected at significantly higher levels in Varaždin soils than in PPP soils, with the highest contribution of the DDT-like compounds (DDX) detected in soils affected by river deposits. The
p
,
p′
-DDE/
p
,
p′
-DDT ratio in Varaždin soils indicated a fresh atmospheric input of
p
,
p′
-DDT. The PPP soil analysis detected a presence of only
p
,
p′
-DDE and HCB at levels corresponding to their global environmental presence.
PDF
