A preliminary evaluation of the DDT contamination of sediments in lakes Natron and Bogoria (Eastern Rift Valley, Africa)

Freshwater Lacustrine Zooplankton and Microplastic: An Issue to Be Still Explored

Lakes are essentially interlinked to humans as they provide water for drinking, agriculture, industrial and domestic purposes. The upsurge of plastic usage, its persistence, and potential detrimental effects on organisms cause impacts on the trophic food web of freshwater ecosystems; this issue, however, still needs to be explored. Zooplankton worldwide is commonly studied as an indicator of environmental risk in aquatic ecosystems for several pollutants. The aim of the review is to link the existing knowledge of microplastic pollution in zooplankton to assess the potential risks linked to these organisms which are at the first level of the lacustrine trophic web. A database search was conducted through the main databases to gather the relevant literature over the course of time. The sensitivity of zooplankton organisms is evident from laboratory studies, whereas several knowledge gaps exist in the understanding of mechanisms causing toxicity. This review also highlights insufficient data on field studies hampering the understanding of the pollution extent in lakes, as well as unclear trends on ecosystem-level cascading effects of microplastics (MPs) and mechanisms of toxicity (especially in combination with other pollutants). Therefore, this review provides insight into understanding the overlooked issues of microplastic in lake ecosystems to gain an accurate ecological risk assessment.

Seasonal variation in pesticide residue occurrences in surface waters found in Narok and Bomet Counties, Kenya

Narok and Bomet are agricultural counties in Kenya which depend on flowing surface waters for farming activities. Agrochemicals have frequently been used to increase agricultural produce in this region. Occasionally, appropriate pesticide utilization measures are not followed. These surface waters are also consumed domestically by humans, livestock, and wild animals thus posing safety concerns to them. The current study sought to evaluate the levels and nature of pesticide residues found in surface waters in the dry and wet seasons of these counties. Eight water samples were collected in July (dry season) and October (wet season) at four different river sites in each of the two counties predetermined by the agricultural activity of its proximate environs. Pesticides extracted by solid phase extraction were analyzed by gas chromatography-mass spectrometry. At least 38 different pesticides were detected in the two counties with the highest concentration being recorded for chlorpyrifos and piperidine in Narok and Bomet counties, respectively. The pesticides chlorpyrifos, cypermethrin, cyfluthrin, and cyhalothrin were more prevalent in Narok County while triazine, semicarbazone, and epinephrine were more prevalent in Bomet County. There were significantly more pesticides detected during the wet season (P ≤ 0.05). Out of the nine prevalent pesticides detected, four of them posed serious ecotoxicology concerns with risk quotients above 1.0 (high risk); thus, there is a need for more government policy interventions in deterring farming near riparian lands and in training of famers regarding best practice for pesticide applications.

Environmental threat and change detection in saline lakes from 1960 to 2021: background, present, and future

Saline lakes are internationally known for unique chemical compositions, incorporate assorted foliage, and give a few biological system benefits and have high environmental, financial, and social qualities are additionally assigned as the Ramsar site for giving wetlands to migratory birds. The anthropogenic and regular unsettling influences have influenced the water nature of these lakes by immediate or circuitous tainting of various contaminations in releases from refining, mining, and modern locales. The impacts of such exercises bring about changes to the typical attributes of saline lakes, principal limnological changes, and loss of biodiversity that debase the upsides of saline lakes. Saline water bodies are not expected and are perceived as significant inland sea-going environments. To review the present circumstance, there is a need to bring issues to light of the idea of dangers and their effects on the environment. The article remembers the situation with water contamination for some saline lakes and its unfavorable impact on biodiversity. The audit plans to cause notice the broad harm of saline lakes that have now gone through because of contamination from last years.

Pesticide residue levels in surface water, using a passive sampler and in the sediment along the littoral zone of Lake Ziway at selected sites

Diaion® HP-20 resin passive samplers deployed in water and sediment samples collected from Lake Ziway were analyzed for 30 organochlorine, organophosphorus, carboxamide, and pyrethroid pesticide residues. The samples were collected from purposely selected sampling stations in five sites on Lake Ziway. Levels of selected pesticides were determined by GC–MS/MS in all samples. p,p′DDE and boscalid residues were the only detected pesticides in sediment samples. Similarly, only metalaxyl and boscalid residues were recovered from HP-20 resins. The concentration of p,p′DDE and boscalid in sediment ranged from 0.66–7.23 and 0.1–15.26 ng g−1 dry weight respectively. The presence of p,p′DDE but no other metabolites of DDT in all sediment samples indicated that DDT residues in Ziway Lake were aged and probably originated from the weathered agricultural soils of the surrounding region. The highest level of boscalid was recorded at Site 2 (near the floriculture enterprises) both in sediment and in HP-20 resins with a mean concentration of 11.8 ng g−1 dw and 39.6 ng g−1 disk respectively. However, the concertation of metalaxyl was the highest in the HP-20 resins deployed at Site1 and Site 4 (near the intensive small-scale vegetable farm) with a mean concentration of 54.7 ng g−1 disk and 54.3 ng g−1 disk respectively. Generally, most sampling sites of p,p′DDE were found to have a moderate ecological risk based on levels specified in the sediment quality standards. Moreover, the relatively high boscalid and metalaxyl levels in HP-20 deployed in Lake Ziway would be the result of recent intensive pesticide use by floriculture enterprises and small-scale vegetable farmers in the region. A spatial variation on the accumulation of detected pesticides among the sampling sites depends on the anthropogenic activities, around the lake from the point and non-point sources. Although most of the analyzed pesticides were below the detectable limit, further studies and continued monitoring of currently used pesticide residues in the Lake are highly recommended.

Monitoring and Management of Inland Waters: Insights from the Most Inhabited Italian Region

Monitoring of freshwaters allows the detection of the impacts of multiple anthropic uses and activities on aquatic ecosystems, and an eco-sustainable management of natural resources could limit these impacts. In this work, we highlighted two main issues affecting inland waters, referring to findings from the most inhabited Italian region (Lombardy, approximately 10 M inhabitants): the first issue is lake pollution by old generation pesticides, the second is river development for hydropower. In both cases, some management strategies reducing the anthropic impacts on freshwaters were discussed: organic farming and biocontrol as an alternative to diffuse pollution by agrochemicals; environmental flows and controlled sediment flushing operations to limit the hydropower impact on rivers. Although the two mentioned issues were discussed separately in this paper, the management of water resources should be carried out in a comprehensive way, accounting for the multiple impacts affecting freshwater ecosystems, including those related to the climate changes.

Co-Occurrence of Cyanobacteria and Cyanotoxins with Other Environmental Health Hazards: Impacts and Implications

Toxin-producing cyanobacteria in aquatic, terrestrial, and aerial environments can occur alongside a wide range of additional health hazards including biological agents and synthetic materials. Cases of intoxications involving cyanobacteria and cyanotoxins, with exposure to additional hazards, are discussed. Examples of the co-occurrence of cyanobacteria in such combinations are reviewed, including cyanobacteria and cyanotoxins plus algal toxins, microbial pathogens and fecal indicator bacteria, metals, pesticides, and microplastics. Toxicity assessments of cyanobacteria, cyanotoxins, and these additional agents, where investigated in bioassays and in defined combinations, are discussed and further research needs are identified.

Atmospheric ammonia (NH3) emanations from Lake Natron's saline mudflats

In a recent global analysis of satellite-derived atmospheric NH₃ data, a hotspot was observed in the vicinity of Lake Natron, Tanzania. The lake is in the centre of an endorheic (limited drainage) basin and has shallow, saline-alkaline waters. Its remote location and the absence of nearby large anthropogenic sources suggest that the observed NH₃ is mainly of natural origin. Here we explore 10 years of IASI NH₃ satellite data and other publicly available datasets over the area to characterize the natural NH₃ emissions in this unique ecosystem. Temporal analysis reveals that the emissions are episodic and linked with the lake’s surface area. The largest NH₃ column loadings generally occur at the end of the dry season in September–November over Lake Natron’s largest mudflat, that is exposed with receding water levels. The timing is different from the agricultural dominated NH₃ emissions in the wider Natron area, which peak early in the year, after the first wet season. The likely source of NH₃ at Lake Natron is decomposition of organic material, either from rivers and springs or produced in the lake (plankton, bird excreta). High temperatures and alkalinity are known to promote NH₃ losses from soda lakes. We formulate six processes that may explain why the largest losses are observed specifically over concentrated brines and/or exposed sediments. As a by-product, we also show that hyperspectral infrared sounders such as IASI are capable of mapping different types of evaporative minerals such as trona and thermonatrite.

First results on zooplankton community composition and contamination by some persistent organic pollutants in the Gulf of Tadjoura (Djibouti)

The Gulf of Tadjoura is located in the Horn of Africa and is widely recognized as an important site where the zooplanktivorous whale sharks seasonally aggregate from October to February. The surface zooplankton community (0-3m) was weekly sampled from November 2016 to February 2017 in two sites during the whale shark aggregation period. A total of 12 phyla were identified. Copepoda represented the most abundant and diverse group with 29 different genera, and contributed with an average of 82% of the mean zooplankton density of approximately 6600indm^-3. During the sampling period, copepods were dominated numerically by Calanoida (3600indm^-3), followed by Poicilostomatatoida (1300indm^-3). Within the copepods, Paracalanidae, Calanidae, Oncaeidae and Miraciidae were the most common families. The temporal trend in zooplankton biomass at both stations revealed the highest peak in December (41.3±36.4mgm^-3), and the lowest in February (6.6±3.3mgm^-3). As no information is available on the occurrence of legacy contaminants use and release in this area, analysis revealed the consistent presence of both DDT and PCB residues in zooplankton samples in the Gulf of Tadjoura. Total PCB ranged from approximately 110 to 637ngg^-1 d.w., while total DDT from 21 to 80ngg^-1 d.w. The proportion of primary DDT in the total residue was higher than DDE and DDD, which strongly suggests that the area might actually be subjected to DDT inputs of the parent compound.

Blood concentrations of PCBs and DDTs in an avian predator endemic to southern Africa: Associations with habitat, electrical transformers and diet

Persistent pollutants such as organochlorine compounds (OCs) have been highlighted as a cause of population decline in avian predators. Understanding patterns of OCs contamination can be crucial for the conservation of affected species, yet little is known on these threats to African raptors. Here we report on OC concentrations in an endangered predator endemic to southern Africa, the Black Harrier Circus maurus. Blood samples were collected in 2012-2014 from wild nestlings (n = 90) and adults (n = 23) in south-western South Africa, where agriculture and urbanization have developed rapidly since the 1950s. Polychlorinated biphenyl (ΣPCB) and dichlorodiphenyltrichloroethane (ΣDDT, for p,p'-DDT + p,p'-DDE) were detected in 79% and 84% of sampled individuals, respectively, with varying concentrations among demographic groups: nestlings had significantly higher ΣPCB and p,p'-DDT concentrations than adults, while adults had higher levels of p,p'-DDE than nestlings. Levels of ΣPCB significantly increased with an index of electric transformer density, a measure of the number and power of electric transformers around active nests. We propose this index as a useful tool for assessing ΣPCB exposure risk in other wildlife. Levels of p,p'-DDE significantly increased with the proportion of wetlands within the breeding territory, and also with the proportion of bird biomass in the diet. No association was found between OC levels and the protected area status of nesting sites. Physiological effects of contaminants were also manifest in increased white blood cell counts with higher p,p'-DDT levels. Heterophil to lymphocyte ratio increased with higher ΣPCB levels, suggesting increased physiological stress and reduced immunity in contaminated individuals. Our results suggest that OCs are still a current cause of concern for endangered Black Harriers, as well as other sympatric predators.

Ecotoxicity of pp'DDE to Daphnia magna

pp'-Dichlorodiphenyl-dichloroethylene (pp'DDE), a metabolite of pp'-dichlorodiphenyl-trichloroethane poses a risk for many ecosystems in spite of the banning of the parent compound because of its persistence and bioaccumulability. Nevertheless, the knowledge of acute and chronic toxicity on aquatic organisms is still very poor. In the present study, Daphnia magna was exposed to varying concentrations of pp'DDE in water and through diet to determine both acute toxicity and potential for effects on reproduction and survivability. The 48 h IC50 was 5.08 μg L(-1) (3.76-7.01 μg L(-1)). As pp'DDE concentration in water was not stable and the amount assumed by food cannot be established with certainty, the results of chronic toxicity tests were expressed as the concentration in the organism which caused a negative effect. Grazing activity was affected with a pp'DDE concentration in the organism of 24 ng mg(-1) d.w., while the lowest observed effect concentration for fecundity reduction was 109 ng mg(-1) d.w.

Environmental variables affecting the distribution of POPs on Mt. Meru, Tanzania

Tanzania is an equatorial country characterized by warm temperatures, which should increase the volatilization of persistent organic pollutants (POPs), but this scenario could be different in mountainous areas like Mount Meru, a volcano situated in the East African Rift (Tz). We collected soil samples along an altitudinal transect upto 4577 m a.s.l., reporting the first data about POP contamination in this area (DDX, HCHs, HCB and PCBs). The DDX contamination pattern in Mt. Meru shows levels slightly higher than those of other remote places with a strong increase in the metabolites/DDT historical trend, which is different from DDX, PCBs, HCHs and particularly HCB as this shows very low contamination levels. Back trajectory analysis allowed a discussion about putative contamination sources, while analysis of the environmental features (climatic and pedological) allowed us to discriminate their relative importance. The distribution of POPs shows a strong correlation with soil organic matter and vegetation. SOM-normalization evidenced altitudinal dependence according to cold condensation for PCBs and HCHs, while DDX are present in larger amounts in the agricultural area at the volcano foot. OM-normalized concentrations suggested also a possible role of the OM composition on the POPs' distribution.