Distribution Of Organochlorine Pesticides Research Articles

Assessing the distribution and ecotoxicological risks of organochlorine pesticides in a river-wetland system of the Manipur River basin, India

ABSTRACT The present study aims to evaluate the distribution of organochlorine pesticides in the Loktak Lake and its draining rivers over a spatial and seasonal scale. Organochlorine pesticides including α- HCH, β- HCH, γ- HCH, δ- HCH, Aldrin, 4,4-DDE, Endrin, Endosulfan II, 4,4-DDD, Endrin Aldehyde, Endosulfan sulphate and 4,4-DDT were analysed in the water and sediments adopting gas chromatography and mass spectrometric techniques. The concentration of pesticides recorded the highest concentration of 2271 ng/l in the water samples and 5319 ng/g in sediment samples. In water samples, Endosulfan II, Endrin and γ- HCH were present at the higher concentrations, whereas α-BHC was recorded at the lowest at 0.78 ng/l. In sediment samples, 4, 4-DDT recorded the highest concentration, followed by 4,4-DDD and Endosulfan II. Human health risk assessment based on water consumption shows higher risk potential from five pesticides. Pesticides in the region may pose a threat to the wetland comprising vital flora and fauna of the biodiversity hotspot. The bacterial population was more or less related to the pesticide concentration, with a lower population at less contaminated sites.

Spatial pattern and compositional distribution of organochlorine pesticides in the black soil region of Shenyang

Organochlorine pesticides (OCPs) are persistent organic pollutants (POPs) prevalent in soils with carcinogenic, teratogenic and mutagenic hazards that are commonly found in soils and remain in the environment even though they have been banned. In order to fill the gap of fewer studies after the ban, soil samples were collected from 308 agricultural fields of cash crops and grain crops in the black soil area of Shenyang City (Liaozhong District, Faku County, Xinmin City and Kangping County) in this study. The aim was to determine, the use and distribution characteristics of OCPs in agricultural soils in the black soil region of Shenyang City. Compositional analysis showed that the detection rate of banned OCPs in agricultural soils was 71.75%, including contaminants such as technical dichloro-diphenyl-trichloroethane (DDT), chlordane and hexachlorobenzene (HCB), which were widely distributed in Liaozhong District, Faku County, Xinmin City and Kangping County, with 45.25% of the fields having compounded contamination of OCPs, and several areas were involved in the fresh inputs of contaminants such as technical DDT. Among them, Kangping County and Faku County are more seriously polluted, with 66.29% and 60.71% of OCPs exceeding the standard. Soil OCPs is more serious in cabbage and rice farmland among cash and food crop farmland. Based on Chinese policy on control, prevention and other pesticide management measures, it was concluded that the framework should be strengthened to prevent further illegal use of banned OCPs.

Investigation of the Dispersed-Phase Distribution of Organochlorine Pesticides, Polychlorinated Biphenyls and Polycyclic Aromatic Hydrocarbons in Natural Water Systems

The article analyzes the patterns of the dispersed-phase distribution of organic ecotoxicants, namely organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), and polycyclic aromatic hydrocarbons (PAHs), in natural water systems. The relationship between the dispersed-phase distribution of individual OCPs, PCBs, and PAHs and the logarithm of the octanol-water partition coefficient log Ko/w (hydrophobicity coefficient) was established. It was shown that the water-soluble part of individual organic ecotoxicants decreases with an increase in their hydrophobicity coefficient. Eight of the given eleven correlations are clear, significant and reliable. The influence of the characteristics of the water system on the dispersed-phase distribution of organic ecotoxicants was also investigated. It was shown that the total water-soluble part of OCPs, PCBs, and PAHs decreases with an increase in the chemical oxygen demand (COD), biological oxygen demand (BOD), and the total concentration of heavy metals (Cr, Ni, Cu, Mn, Zn, Cd, Pb). Four of the nine relevant correlations are clear, significant, and reliable.

Risk surveillance with spatial distribution of Organochlorine Pesticides (OCPs) from sedimentary samples of Chenab River

A pioneering study employed a holistic geostatistical approach to predict the spatial variability of a non sampled area in the Chenab River, Pakistan, using kriging interpolation for organochlorine pesticide (OCP)-polluted risk zones. The Present research intended to investigate the carcinogenic and non-carcinogenic human health risks, contamination levels, and spatial variation of OCPs in the Chenab River, Pakistan. The residual OCP content in sediment samples (n = 120) ranged from 0.056 to 32.14 ng/g. DDE and α-HCH were prevalent among all the samples analyzed, with mean concentrations of 15.84 ± 8.02 and 12.45 ± 6.72 ng/g, respectively. The order of magnitude of OCPs in sediment samples was DDTs > α-HCH > chlorothalonil > heptachlor > endosulfan > aldrin > dieldrin. The findings of the single (SPI) and Nemerow (Nel) pollution index of α-HCH, heptachlor, and aldrin depicted the Chenab River as a serious pollution risk zone. The outcomes of the Pearson correlation coefficient analysis represent the positive correlation among all OCPs, revealing the common origin. Distribution trends showed substantially higher (p < 0.05) contents of analyzed OCPs along the downstream zone. With regards to USEPA human health hazard assessment model, the estimated non-carcinogenic (ΣHI) and non-carcinogenic (ΣTCR) risk ranged from 1.1 × 10−5 to 1.0 × 10−1, 4.0 × 10−8 to 3.2 × 10−4 respectively. TCR >10−4 illustrated a substantial cancer health risk posed by α-HCH, heptachlor, aldrin, and dieldrin in the downstream zone. We recommend the urgent cessation of the ongoing discharge of OCPs into the Chenab River, which needs to be highlighted owing to the significant cancer risk to public health to ensure the good health and wellbeings.

Enrichment, bioaccumulation and human health assessment of organochlorine pesticides in sediments and edible fish of a plateau lake.

The organochlorine pesticides (OCPs) are with features of persistence, high toxicity, bioaccumulation and adverse impact on ecosystems and human beings. Although OCPs pollutions have been observed in the plateau lakes, comprehensive understandings in the distribution characteristics and human health risks of OCPs in these valuable but fragile ecosystems are limited. We here investigated the distribution, bioaccumulation process and health risks of OCPs in the Jianhu lake, a representative plateau lake in China. The endrin ketone, endrin aldehyde and heptachlor were the most dominant species in surface and columnar sediments. Their total contents ranged between 0 ~ 1.92 × 103ng·g-1. The distribution of OCPs in sediment cores combined with chronology information indicated that the fast accumulation of OCPs happened during the last decades. Combining the distribution features of OCPs in different sources with mixing model results of carbon isotope (δ13C), farming area was identified as the main source (46%), and the OCPs were transported to lake by inflow-rivers (37%). The enrichment of OCPs in sediments caused considerable bioaccumulation of OCPs in local fish (∑OCPs 0-3199.93ng·g-1, dw) with the bio-sediment accumulation factor (BSAF) ranging from ND to 9.41. Moreover, growing time was another key factor governing the accumulation in specific species (Carassius auratus and Cyprinus carpio). Eventually, the carcinogenic risk index (CRI) and exposure risk index (ERI) of the endrin category and aldrin exceeded the reference value, indicating relatively high health risks through consumption of fish. Overall, this study systematically illustrated the bioaccumulation process and health risks of OCPs in the typical plateau lake, providing theoretical support for the better protection of this kind of lakes.

Distribution of organochlorine pesticides (OCPs) in surface-mixed layer water and intertidal sediments of Lagos lagoon, Gulf of Guinea

Organochlorinated pesticides (OCPs) were analysed in intertidal sediments and surface-mixed layer water of Lagos lagoon in Nigeria in order to elucidate the contamination levels, sources and distribution characteristics, and potential human and ecological health risks associated with exposures to OCPs. The total ∑ OCPs in sediments ranged from 222.35 to 2585.30 μg/kg dw, with a mean concentration range between 13.08 and 172.35 μg/kg dw, respectively. The most dominant OCP compounds in the sediments were dichlorodiphenylethanes (40%), chlors (26%), cyclodienes (17%), HCHs (9%), and endos (8%). The concentration (μg/kg) of individual ∑OCP groups in sediment decreased in the following order: ∑ dichlorodiphenylethanes > ∑ Chlors > ∑ Cyclodienes > ∑ HCHs > ∑ Endos. The ∑ OCPs in water ranged from 23.63 (mean concentration: 1.97 ng/L) to 172.05 ng/L (mean concentration: 13.23 ng/L). Dichlorodiphenylethanes (46%), cyclodienes (21%), chlors (14%), HCHs (12%), and endos (7%) were the most prevalent OCP compounds in investigated water samples. These locations are pollution hotspots for potential wastes arising from industrial effluents, heavy shipping activities, municipal wastes and discharges of transformer oil from abandoned power generation and transmission facilities. The total composition and β-, γ- and δ-HCH isomeric ratios suggest recent anthropogenic introduction of the HCHs into the lagoonal ecosystem compared to historical deposits. Dichlorodiphenylethanes (p,p′-DDD, p,p′-DDE, and methoxychlor) were ubiquitous except p,p′-DDT. Results indicate historical inputs of technical DDT with considerable biodegradation and photochemical transformations. Generally, the ∑ chlors in sediments and surface-mixed layer water samples decreased following heptachlor > heptachlor epoxide > α-Chlordane > γ-Chlordane. The α-chlordane/γ-chlordane ratios indicate a mix of recent commercial and historical chlordane contamination sources. Concentrations of most OCPs significantly exceeded sediment quality guidelines suggesting that toxicity to benthic-dwelling faunas is estimated to be likely.

Temporal trends, sources, and ecological risk of residual organochlorine pesticides (OCPs) in sediment core from the Dongping Lake, North China.

A sedimentary record of the 19 organochlorine pesticides (OCPs) pollutants from Dongping Lake, north China, is presented in this study. According to the dating of core sediment and OCP content analysis in samples, from 1904 to 2016, the total concentration of OCPs varied from undetectable levels (n.d.) to 33.1ng/g. The OCP concentration was first detected in the samples of 1938, and then gradually increased to a peak level in 2000 thereafter decreased until 2016. Among the detected OCPs, hexachlorocyclohexanes (HCHs) and dichlorodiphenyltrichloroethanes (DDTs) were the predominant and the most frequently detected contaminants in the core sediment, with concentrations ranging from n.d. to 16.9ng/g and from n.d. to 8.8ng/g, respectively. The distribution of OCPs in the sediments was affected by organic carbon concentration, showing a significant positive correlation (r = 0.93, p < 0.001), especially for HCHs (r = 0.98, p < 0.001). The source analysis showed that HCH contamination mainly derived from historical use of technical HCHs, while in recent years, it derived from lindane usage. DDT pollution was attributed to historical use of technical DDTs, as well as the microbial degradation of historic DDT residues. Finally, risk analysis was performed for OCPs in sediment cores based on sediment quality guidelines from the Canadian Council of Ministers of the Environment, showing that DDTs presented a high ecological toxicity risk during the period of 1959-2010.

Spatio-temporal distribution of organochlorine pesticides in agricultural soils of southeast China during 2014-2019

Organochlorine pesticides (OCPs) are organic pollutants that are persistent and undegradable in the environment. To investigate their residual concentrations, spatial and temporal distributions, and the relationship with the crops planted, 12 individual OCPs in 687 soil samples from Jiangsu, Zhejiang and Jiangxi provinces of southeast China were examined. The detection frequencies of OCPs in the studied areas were 1.89%–64.9%. The concentrations of dichloro-diphenyl-trichloroethanes (DDTs), hexachlorocyclohexanes (HCHs), and endosulfans ranged from 0.01 to 5659 μg/kg, 0.03–3.58 μg/kg, and 0.05–3235 μg/kg, respectively. Jiangsu was mainly contaminated by p,p'-DDT, p,p'-DDD and endosulfan sulfate, Zhejiang was more polluted by OCPs except δ-HCH, and Jiangxi was more vulnerable to the contamination of OCPs except o,p'-DDE. The partial least-squares discrimination analysis (PLS-DA) model with RX2 36.3–36.8% revealed that compounds with similar chemical properties tended to appear in the same year and month. All crop lands were polluted by DDTs and Endosulfans. The highest concentrations of DDTs and Endosulfans were found in citrus and vegetable fields, respectively. This study offers new insight into the layout and partitioning of OCPs in agricultural land and into insecticide management on public health and ecological safety.

Distributions of OCPs and CUPs in the Sediment and Surface Water Close to a Drinking Water Reservoir in Northeastern China

In the Chinese city of Wuchang, Heilongjiang Province, a survey was conducted to track the concentrations and distributions of several organic pollutants near drinking water reservoirs, such as conventional organochlorine pesticides (OCPs) and currently in use pesticides (CUPs), including organophosphorus pesticides (OPPs) and neutral herbicides (NHs). From October 2007 to July 2008, a total of 32 pairs of water and sediment samples were gathered and examined. The results showed that the total concentrations of OCPs, OPPs, and NHs in the sediments were 0.42–7.8 ng/dm3 below the detection limit of these pollutants in sediments. The total concentration of OPPs in the water varied from the LoD to 180 ng/dm3 while NHs were 6.3 to 740 ng/dm3. While the CUP concentrations changed significantly throughout the year, the OCP concentrations were less impacted by seasonal fluctuations, indicating no recent introduction of these chemicals. The use of pesticides on crops in the primarily agricultural area was the main factor contributing to higher concentrations of CUPs during the summer.

Distribution of organochlorine pesticides in surface and deep waters of the Southern Indian Ocean and coastal Antarctic waters

Antarctica is a remote and pristine region. Yet it plays a vital role in biogeochemical cycles of global anthropogenic contaminants, such as persistent organic pollution (POPs). This work reports the distribution of legacy and new POPs in surface and depth profiles/deeper water of the Southern Indian Ocean (SIO) and the coast of Antarctica (COA). Samples were collected during the 10th Indian Southern Ocean expedition (SOE-10) in the year 2017. Concentrations of ∑HCH (hexachlorocyclohexane), ∑DDT (dichlorodiphenyltrichloroethane), and ∑ENDO (endosulfan) in surface seawater from the SIO region ranged between not detected (ND) to 1.21 pg/Liter (pg L−1) (average. ± s.d.: 0.35 ± 0.42 pg L−1), ND to 1.83 pg L−1 (0.69 ± 84 pg L−1), and ND - to 2.06 pg L−1 (0.56 ± 0., 88 pg L−1), respectively. The concentrations of ∑HCH, ∑DDT, and ∑ENDO in COA ranged from ND to 0.98 pg L−1 (0.25 ± 0.27 pg L−1), ND to 3.61 pg L−1(0.50 ± 1.08 pg L−1), and ND to 2.09 pg L−1 (0.45 ± 0.84 pg L−1), respectively. Concentrations of isomers of endosulfan, and largely of HCHs, suggested an aged source. Some concentration ratios of α-to γ-HCH were close to 1, indicating a contribution from ongoing sources. Results indicate the important role of ocean currents in mediating the transport and detection of OCPs. As such, OCPs dynamics in deeper oceans may play an important role in OCPs cycling in the marine environment.

National-scale monitoring of historic used organochlorine pesticides (OCPs) and current used pesticides (CUPs) in Chinese surface soil: Old topic and new story.

Along with the restriction and prohibition of historic used organochlorine pesticides (OCPs), current used pesticides (CUPs) were widely used as alternatives. In order to investigate the pollution characteristics of pesticides, the levels and spatial distributions of OCPs and CUPs in 154 surface soil across China were comprehensively compared. Totally, 107 target pesticides were screened, and 20 OCPs and 34 CUPs were detected. The numbers of co-occurred pesticides in single soil sample were from 17 to 36 indicating the diversity and complexity of pesticides pollution. The concentrations of OCPs in urban soils were higher than rural soils, while rural >urban for CUPs. Furthermore, obviously different spatial distribution patterns were found for OCPs and CUPs. For OCPs, the secondary distribution pattern was dominant. For CUPs, the primary distribution pattern was obviously observed due to their current extensive usage. In addition, higher concentrations of both CUPs and OCPs were accumulated in the Northeast China Plain due to long-range atmospheric transport and deposition. Along with the old topic of OCPs, the study pointed out the preliminary understanding of CUPs pollution characteristic in surface soil of China, which provided a new story with the deep understanding of their environmental fate in both China and the world.

A national-scale distribution of organochlorine pesticides (OCPs) in cropland soils and major types of food crops in China: Co-occurrence and associated risks

Organochlorine pesticides (OCPs) are persistent organic pollutants (POPs) that resist degradation in the environment. OCPs remain detectable in cropland systems in China. However, spatial distribution of OCPs across China and associated ecological and health risks, as well as the relationship between levels of OCPs in cropland soils and crops, remain to be elucidated. To fill these gaps, we conducted a national-scale characterization of 19 individual OCPs in cropland soils and food crops including cereals and legumes in China, which were on-spot sampled simultaneously. Sparse canonical correlation analysis was employed to investigate the co-occurrence of OCPs in cropland soils and corresponding food crops. The ecological soil screening levels and risk quotient method were adopted for ecological and health risk assessment, respectively. Dichlorodiphenyltrichloroethanes (DDTs) were dominant in cropland systems, with its levels ranging up to 337 and 22.8 μg/kg in cropland soils and food crops, respectively. The mean ∑OCP levels in cropland soils varied from below the limit of detection to 337 μg/kg. Peanuts were the most contaminated crop, in which endosulfans and hexachlorobenzene (HCB) were co-occurrent with those in cropland soils (correlation coefficient R = 0.999 and 0.947, respectively). Besides, lindane and β-endosulfan in rice were co-occurrent with those in cropland soils (R = 0.810 and 0.868, respectively). The componential ratio analysis indicated fresh inputs of technical DDT, lindane, chlordane, endosulfan, HCB and aldrin. Among these pesticides, ecological impacts of DDTs, lindane, aldrin and β-endosulfan could be expected. Human health risk assessment suggested that daily consumption of the OCP-contaminated food crops raises a health concern especially for male teens. It is concluded that OCPs remain present in cropland systems in China at levels that raise a concern for both environment and human health.

Organochlorine pesticide contamination in sediments from Richards Bay, South Africa: spatial trends and ecotoxicological risks

The occurrence and distribution of organochlorine pesticides (OCPs) in aquatic systems is a matter of global concern and poses significant toxicological threats to both organisms and human health. Despite the extensive use of OCPs for pest and disease control in southern Africa, relatively few studies have examined the occurrence and toxicological risks of OCP residues in the region. This study investigates the composition, distribution, and potential sources of OCP contamination in sediments from Richards Bay, a rapidly developing industrial port on the northeast coast of South Africa. Surface sediments collected from Richards Bay Harbour and surrounding areas indicate that OCP contamination in the region is widespread. Total concentrations (∑OCP) in surface samples ranged from 135 to 1020 ng g−1, with hexachlorocyclohexanes (∑HCH; 35–230 ng g−1) and dichlorodiphenyltrichloroethanes (∑DDT; 12–350 ng g−1) the dominant contaminant groups detected. Metabolite isomeric compositions indicate that the presence of aldrin and endosulfan likely result from historical agricultural usage, while recent input of γ-HCH, heptachlor, and endrin may be linked to the illegal use of old pesticide stockpiles. Total DDT concentrations were dominated by p,p′-DDT (80 ± 64 ng g−1), which was attributed to its ongoing use in malaria vector control in the region. A 210Pb-dated sediment core revealed that OCP input to the local environment increased dramatically from relatively low concentrations in the mid-1940s (∑OCP, 355 ng g−1) to peak levels (∑OCP, 781 ng g−1) in the 1980s/1990s. An overall decrease in ∑OCP concentration from the mid-2000s is likely related to restrictions on use following the Stockholm Convention in 2004. Despite current restrictions on use, OCP concentrations exceeded sediment quality guidelines in the vast majority of cases, raising concerns for protected estuarine and mangrove habitats in the area, as well as for local fishing and farming communities.

The application of sediment quality guidelines and toxicity assessment to identify contaminant hotspots in an urbanised West Australian estuary.

This paper presents a tiered assessment approach that enabled identification, triage, interrogation and confirmation of significantly contaminated areas of an urbanised West Australian estuary. The spatial distribution of organochlorine pesticides (OCPs), polycyclic aromatic hydrocarbons (PAHs) and bioavailable metals was determined in surficial sediments of the Swan-Canning Estuary through broad-scale screening (500 cores, 100 composite samples, 20 locations). The application of sediment quality guideline values (SQGVs) enabled ranking of locations through risk-based scoring and identification of contaminant hotspots. Subsequent targeted ecotoxicological and chemical assessment was undertaken at the highest scoring location in each tributary (80 cores, 16 composite samples, 3 locations, 16 sites). In the Canning tributary, Bull Creek sediments demonstrated the highest metal concentrations and greatest number of SQGVs exceeded. High-level toxicity was experienced in copepods and moderate toxicity in mussels (test sensitivity: copepod>mussel>amphipod). Toxicity-inducing contamination was attributable to two stormwater outfalls and limited to 300 m from points of discharge. In the Swan tributary, Claisebrook sediments demonstrated the highest concentrations of all PAHs, most OCPs and metals and the greatest number of SQGVs exceeded. High-level toxicity was reported in fish and mussels and moderate toxicity in copepods and amphipods (test sensitivity: fish>mussel>amphipod>copepod). Toxicity-inducing contamination included a stretch of estuary >1 km long, and two stormwater outfalls in the area were likely sources. The distribution and nature of PAH contamination suggested an additional source at Claisebrook. This combined chemistry and biological effects dataset provides critical information for the management of planned major development and concomitant estuary-bed disturbance in the coming decade.

Distribution of organochlorine pesticides and polychlorinated biphenyls present in surface sediments of the Sabaki and Tana estuaries, Kenya

Polychlorinated biphenyls (PCBs) and Organochlorine pesticides (OCPs) in the surface sediments of the Sabaki and Tana estuaries were studied to determine distribution as well as their ecological risk. The concentration range of PCBs and OCPs were 0.65-9.29 ng/g dw and 0.47-9.84 ng/g dw, respectively. Sabaki Bridge in the Sabaki River and Tana 4 in the Tana River recorded high levels of both PCBs and OCPs. The calculated values of DDD+DDE/ DDT showed that the presence of DDT from both the rivers is a result of historical input. The ecotoxicological impact of sediment pollution by PCBs and OCPs was assessed using sediment quality guidelines specified by the Canadian Council of Ministers of the Environment. The concentration values for PCB, HCB, Heptachlor epoxide, and Chlordane in this study indicate low ecological risk to sediment dwelling organisms. DDT showed an adverse biological effect to sediment dwelling organisms. As a result, there is a need to establish a programme for monitoring persistent organic pollutants in Kenya, so that any elevation in concentration above the environmental quality standards can be detected and appropriate actions taken to minimize potential adverse effects to the environment and public health.

Vertical profiles of legacy organochlorine pesticides in sediment cores from lake Nakaumi, Japan

Two sediment core samples from the brackish Lake Nakaumi in Japan were analyzed to determine the historical profiles of organochlorine pesticides (OCPs). It was observed that from the 1940s to 2005, the vertical distribution of OCPs in sediment cores reflected the temporal trend of pesticide usage in Japan. Dichlorodiphenyltrichloroethane (DDT) and its metabolites were predominant, with concentrations of 0.008–8.27 ng g−1 dry weight, and their contribution to ΣOCPs was over 58%. The results also confirmed that the DDTs in the sediment cores originated from past input. Further, even though hexachlorocyclohexanes were the most used OCP in Japan, their residual concentrations were lower than those of DDTs and chlordane related compounds (CHLs). The concentrations of CHLs were 0.163–1.539 ng g−1 dry weight, whereas hexachlorobenzene (HCB), drins, heptachlor, and mirex showed very low concentrations. Interestingly, although HCB was never registered as a pesticide in Japan, it was detected in both core samples. This HCB contamination might be attributed to pentachlorophenol. Additionally, the hierarchical cluster analysis results corresponding to both sediment cores could be classified under four groups based on a similarity of over 50%. The results also showed that the OCP burden in Lake Nakaumi for the past 60 years was 130 kg and 1153 kg at Honjo and at the center of Lake Nakaumi, respectively. Overall, the results of this study indicate that the distribution of OCPs in Lake Nakaumi reflects the trend of pesticide usage in Japan.

Level, source, and distribution of organochlorine pesticides (OCPs) in agricultural soils of Tanzania.

This study investigated the level, composition, and spatial and vertical distribution of the organochlorine pesticides (OCPs) at 0-2cm and 2-20cm in the agricultural surface soils from Southeastern to Central-western Tanzania. Although the most abundant OCPs were DDT with a mean concentration of 2.29ng/g, dieldrin (1.57ng/g), and methoxychlor (0.79ng/g), HCH was the most dominant (with detection frequency of 88%). OCP dominance was in the Southern Highlands, which is the most productive agricultural zone. Though there were indicators of recent inputs for some sites, OCP contamination was mainly historical. DDT contamination was dominated by p,p'-DDE and resulted from both technical DDT and dicofol while HCH contamination was dominated by γ-HCH and resulted from both technical HCH and lindane. Based on depth, the OCPs dominated mainly the upper 2cm, which was associated with soil and environmental factors rather than recent inputs since most of the detected compounds were historical. Nevertheless, some sites showed exceptional high abundance in the lower soil with more concentration of parent compounds. Therefore, this study recommends the need for further studies on the influence of soil properties on OCPs' transport in the soil, surface water, and air. Besides, detection of recent inputs at some sites calls for more mapping of the OCPs in the country to strengthen their control and prevention of future risks.

Evaluation and risk assessment of organochlorine pesticide residues in some fish species in south-south Nigeria

This study reports the presence, distribution pattern, concentration levels and health risk assessment of organochlorine pesticide residues in fresh and cured fish species in South-South Nigeria. The concentrations of organochlorine pesticides in fresh and cured fish were analysed with Gas Chromatography/ Mass Spectrophotometry (GC-MS) after Soxhlet extraction of the fish species. The study revealed that no organochlorine pesticide was present in fresh fish. However, cured fish species from all the markets sampled had at least two organochlorine pesticide residues which ranged from endosulfan (0.252±0.0022–748±0.004ug/g), lindane (0.386±0.010–0.443±0.009 ug/g), heptachlor-epoxide (0.328±0.005–3.162±0.010ug/g), ortho-para-dichloro-diphenyl-trichloro-ethane (o,p’-DDT) (0.021±0.001–0.180±0.030ug/g) and aldrin (0.140±0.040–2.770±0.020ug/g). These levels are far higher than the maximum residual limit and allowable daily intake values recommended by World Health Organization (WHO) and Food and Agricultural Organization (FAO). There were no pesticide residues in fresh fish probably because the fisher folks in the study area may have abolished the use of obnoxious fishing methods due to the awareness of threats to the aquatic ecosystem. The high percentage occurrences, amounts and distribution of organochlorine pesticides in cured-fish from markets sampled could be as a result of the fact that these organochlorine pesticides were consistently used in the study area by fish processors, distributors and sellers. Human risk assessment of this study revealed a potential danger in the consumption of cured-fish containing the organochlorine pesticides seen in the study.

DDT in Crimea coastal waters and blubber of Black Sea cetaceans

This research is based on the multi-year data on the distribution of organochlorine pesticides of the DDT group in the water of the coastal Black Sea areas of Crimea, obtained in expeditions of the “Professor Vodyanitsky” research vessel from 1999 to 2020. Study of content of DDT and its metabolites (DDTs) in the blubber of three species of Black Sea cetaceans that were astrand on the Black Sea coast from the 1980s to the 2020s was grounded on own and literature data. While there was an overall significant variability in ∑DDT content during the study period, there was a significant downward trend in their concentrations in the water of coastal areas of Crimea. Despite the significantly decreased DDTs pollution of the habitat of the Black Sea marine mammals over the last 10 years, high concentrations of DDTs were accumulated in their blubber, the maximum value of the sum of DDTs concentrations reached (163 µg/g of lipids) in the blubber of adult depleted bottlenose dolphin. The minimum concentrations were determined in the blubber of a newborn harbour porpoise female. In blubber samples up to 70% was of DDE, DDD - from 21 to 24%, and the concentration of the initial DDT varied from 6 to 14%. Based on the analysis of own and literature data, it is assumed that in the modern period, as compared to the 1990s, there is a downward trend in the content of the DDTs in the blubber of Black Sea cetaceans.

Polycyclic aromatic hydrocarbons and organochlorine pesticides in floodplain soils: A case study of Onuku River in Okitipupa, Nigeria

We report on the sources, distribution, and toxicity of sixteen polycyclic aromatic hydrocarbons (PAHs) and organochlorine pesticides (OCPs) in floodplain soils of the Onuku River in Okitipupa, Nigeria. Gas chromatography was used to quantify the compounds. Five PAHs with an average trace concentration of 0.25 (benzo(a)pyrene)-21.3 µg/kg (benzo(g,h,i)perylene) were identified, while the OCPs residues ranged from 0.116 (aldrin)-2.18 µg/kg (p,p’-DDT). High spatial distribution of OCPs was mostly recorded among the sampling sites, whereas chlorothalonil, δ-BHC, and p,p’-DDT were the most predominant. High distribution of high molecular weight PAHs (HMW-PAHs) with 6-ring (75.6%) as the most predominant compositions in the study area. The diagnostic ratio of specific PAH compounds revealed pyrogenic origin. Furthermore, the toxic equivalency factors (TEFs) evinced that the carcinogenic potency of benzo(a)pyrene and the equivalent concentration (BaPeq) of PAHs load were relatively low. Hence, regular monitoring of HMW-PAHs is required in the site.