Diep River Research Articles

The impact of informal settlement on water quality of Diep River in Dunoon

Water quality is declining due to the rise of urbanization, overpopulation, industrial production, climate change, non-compliance of wastewater treatment plants, and agricultural waste. The mushrooming of informal settlements along the bank of the Diep River due to population growth in Dunoon compromises the quality of water. Inadequate sanitation and waste disposal practices in the Dunoon informal settlement are a major problem, leading to the contamination of water resources. This research aimed to investigate the impact of Dunoon informal settlement on the Diep River water quality. Water samples were collected for 4 months from four sites of the river to cover the spatial distribution. The laboratory determined the concentrations of nitrates, phosphates, dissolved oxygen, chemical oxygen demand, total suspended solids, and E. coli, while the field study used a multiparameter reader to determine turbidity, temperature, electrical conductivity, pH, salinity, and dissolved oxygen. The results were compared with the South African water quality guidelines for irrigation, recreation, and aquatic ecosystems, and South African National Standards. The study revealed that the average concentrations of E. coli, dissolved oxygen, electrical conductivity, salinity, turbidity, chemical oxygen demand, and ammonia exceeded the recommended limits in both the wet and dry seasons. Based on the findings, the water quality in Diep River is poor and the Dunoon informal settlement has contributed to this to some extent. The pollution of the river may be linked to health problems and environmental degradation. Considering this, the waste discharged into the neighbouring aquatic environments needs to be monitored and managed frequently.

Occurrence and probabilistic risk assessment of PAHs in water and sediment samples of the Diep River, South Africa

This study investigated the levels of polycyclic aromatic hydrocarbons (PAHs) in water and sediment samples of the Diep River freshwater system of Western Cape Province, South Africa. A solid-phase extraction - gas chromatography - flame ionisation detection (SPE-GC-FID) method was utilised to simultaneously determine the 16 United States Environmental Protection Agency (US EPA) listed priority PAHs in water and sediment samples. The seasonal averages of individual PAH detected at the studied sites, ranged between not detected (Nd) and 72.38 ± 9.58 μg/L in water samples and between Nd and 16.65 ± 2.63 μg/g in the corresponding sediment samples. The levels of PAHs measured in water and sediment samples were subjected to probabilistic risk assessment to predict the possibility of regulatory values being exceeded. The average percentage exceedence of 63.26 was obtained for PAHs in water samples of the Diep River, while the corresponding average percentage exceedence obtained for sediment sample was 63.71. Sufficient exposure of humans and aquatic organisms to the exceedance levels obtained, would cause adverse health effect.

A Late Holocene community burial area: Evidence of diverse mortuarypractices in the Western Cape, South Africa.

Over several decades, human skeletal remains from at least twelve individuals (males, females, children and infants) were recovered from a small area (ca. 10 x 10 m) on the eastern shore of Table Bay, Cape Town, near the mouth of the Diep River where it empties into the sea. Two groups, each comprising four individuals, appear to have been buried in single graves. Unusually for this region, several skeletons were interred with large numbers of ostrich eggshell (OES) beads. In some cases, careful excavation enabled recovery of segments of beadwork. One collective burial held items including an ostrich egg-shell flask, a tortoise carapace bowl, a fragmentary bone point or linkshaft and various lithic artefacts. This group appears to have died together and been buried expediently. A mid-adult woman from this group sustained perimortem blunt-force trauma to her skull, very likely the cause of her death. This case adds to the developing picture of interpersonal violence associated with a period of subsistence intensification among late Holocene foragers. Radiocarbon dates obtained for nine skeletons may overlap but given the uncertainties associated with marine carbon input, we cannot constrain the date range more tightly than 1900–1340 calBP (at 2 sigma). The locale appears to have been used by a community as a burial ground, perhaps regularly for several generations, or on a single catastrophic occasion, or some combination thereof. The evidence documents regional and temporal variation in burial practices among late Holocene foragers of the south-western Cape.

Occurrence of PAHs in water samples of the Diep River, South Africa

Occurrence of polycyclic aromatic hydrocarbons (PAHs) in freshwater may aggravate the water crisis currently being experienced in the Western Cape Province of South Africa. However, there is dearth of data on the levels of PAHs, which is necessary for effective assessment of water quality as well as remediation strategies. This study therefore assessed levels of PAHs in the Diep River freshwater system of Western Cape Province, South Africa. A liquid-liquid extraction solid-phase extraction gas chromatography flame ionisation detection (LLE-SPE-GC-FID) method was developed to simultaneously determine the 16 United States Environmental Protection Agency (USEPA) listed priority PAHs in water samples. The SPE-GC-FID method allowed an acceptable linearity (R2 > 0.999) within the calibration range of 1 to 50 µg/mL. Instrument detection limits ranged between 0.02 and 0.04 µg/mL and instrument quantification limits between 0.06 and 0.13 µg/mL. Recovery study results were also acceptable (83.69–96.44%) except for naphthalene, which had recovery of 60.05% in spiked water matrix. The seasonal averages of individual PAH detected at the studied sites ranged between not detected (nd) and 72.38 ± 9.58 µg/L in water samples.

Improving the Viability of Stormwater Harvesting through Rudimentary Real Time Control

Stormwater Harvesting (SWH) to alleviate water scarcity is often hindered by the lack of suitable available storage in urban areas. This research aimed to discover an economically viable strategy of storing runoff in existing stormwater ponds with the assistance of rudimentary Real Time Control (RTC) techniques to increase the effective storage capacity. The Diep River sub-catchment situated in the southern suburbs of Cape Town, South Africa, that has several stormwater ponds that were largely constructed for the purposes of flood mitigation, was used as a case study. Six SWH scenarios utilising three distinct RTC strategies coupled with two alternative water demand alternatives were simulated with the aid of 10 years’ of historical rainfall data with a view to determining the unit cost of supplying selected developments with non-potable water. The use of RTC to increase the effective storage of the ponds was shown to improve the volumetric yield without significantly impairing the flood mitigation provided by the system at a cost that was comparable to what the local residents were already paying for potable water. This finding is important as it suggests a cost-effective way of overcoming one of the greatest limitations associated with stormwater harvesting.

Disentangling the identities and distribution patterns of the introduced beachfleas Orchestia gammarellus and Platorchestia platensis (Crustacea: Amphipoda: Talitridae) in South Africa

Two introduced beachfleas, Orchestia gammarellus and Platorchestia platensis, have been recorded from South Africa, but have been misidentified by some earlier researchers and, prior to this study, each was also known from just a few, scattered observations, such that their true distributions remained obscure. We illustrate both species to clarify the features that identify and distinguish them and determine their true distributions by re-examining historical samples and by collecting new material from estuaries and lagoons along the west and south coasts of South Africa. Adult males of O. gammarellus have slender antennae and characteristic expanded, flattened, oar-like distal segments on pereopod 7. Adult males of P. platensis have the peduncle of antenna 2 strongly swollen and have bulbous, but not flattened, distal segments on pereopod 7. Both species occur under wrack and other debris along the banks of estuaries and sheltered lagoons. Orchestia gammarellus is found only along the south-west coast, in the Berg River Estuary, Langebaan Lagoon and the Diep River Estuary. Previous records from Knysna were misidentifications of P. platensis. Platorchestia platensis is found at one west coast site, Langebaan Lagoon, but is widely distributed from Cape Point eastwards to at least Algoa Bay. Both species share the same habitats as several other native beachfleas and competitive interactions between native and introduced species merit investigation.

Investigation into the bacterial pollution levels at various sites along the Diep and Plankenburg river systems, 3 Western Cape, South Africa

This study sought to investigate and compare bacterial contamination levels at six different sites along the Diep and Plankenburg river systems in the Western Cape, South Africa. Surface water and sediment samples were collected monthly from the six selected sampling sites along both river courses between January 2014 and December 2014 and were evaluated for bacterial contaminants. Microbial isolation, characterisation and identification were done using conventional techniques (serial dilution, Gram staining, and biochemical testing) and molecular identification techniques (polymerase chain reaction and DNA sequencing). A total of 19 bacterial isolates belonging to the genera Raoultella, Bacillus, Pseudomonas, Klebsiella, Escherichia, Enterobacter, Exiguobacterium, Acinetobacter, Serratia, Aeromonas, Staphylococcus and Citrobacter were isolated from the surface water and sediment samples at the end of the survey. Higher microbial load was obtained from sediment samples compared to surface water samples. Seasonal variation was also observed in terms of microbial counts. Higher microbial counts were obtained during summer sampling time compared to winter sampling time. The most contaminated site was located on Plankenburg River with average bacterial counts ranging between 3.1 × 10(5)-6.9 × 10(8) CFU/ml and 3.9 × 10(6)-2.88 × 10(9) CFU/ml from surface water and sediment, respectively, recorded at this site during winter and summer. Although lower microbial counts were recorded along the Diep River course, most of the bacterial counts recorded along both rivers exceeded the acceptable maximum limits for river water.

Long-term physical, chemical and biological changes in a small, urban estuary

The Diep River estuary, a small estuary in suburban Cape Town, South Africa, has been subject to disturbance for centuries. Several earlier studies have documented conditions in the system, providing baselines against which to measure more recent changes. This study: (i) describes major physical and hydrological changes that have occurred within this estuary; (ii) documents faunistic changes subsequent to earlier biological surveys; and (iii) provides an up-to-date faunal list. Salinity measurements and both invertebrate and fish samples were taken at five stations along the estuary in summer and winter 2014. A census of sandprawn Callichirus kraussi densities was also undertaken to compare with earlier surveys. Developments within the Diep River catchment and estuary have resulted in extensive changes in flow and salinity regimes, causing marked reductions in summer salinity levels, changes in frequency of mouth closure, and deteriorations in water quality. These have resulted in major changes in faunal composition and distribution, including an increase in numbers of non-indigenous species. Surveys in the early 1950s recorded 47 invertebrate species, whereas only 23 were found in 1974. A total of 23 species were again recorded in 2014, but these included several freshwater forms not previously reported, which had entered the system due to lowered salinity values, as well as new alien introductions. Only six of the 69 taxa recorded were reported by all three surveys. There have been substantial declines in sandprawn abundance, from 40 million in 1998 to just over 12 million in 2014. In all, 12 fish species were recorded in the 1950s, nine in 1974, but only five in 2014, including the newly detected invasive mosquito fish Gambusia affinis and the translocated tilapia Tilapia sparrmanii. Thus, only three of the original native fish species remain. Contrary to these losses, the present bird fauna appear to be more abundant and diverse than previously. Regular monitoring is recommended to obtain a clearer understanding of ongoing changes, and major management interventions will be needed if further degradation is to be prevented.

Polybrominated diphenyl ethers (PBDEs) and hexabromobiphenyl in sediments of the Diep and Kuils Rivers in South Africa

This study reports the concentrations of polybrominated diphenyl ethers and hexabromobiphenyl in bottom sediment of two rivers within the city of Cape Town. Following the isolation of the target compounds by mechanical shaking technique, the routine analyses and structural elucidation of the target analytes were performed with high capillary gas chromatography with electron capture detection (GC-µECD) and gas chromatography-time-of-flight-mass spectrometry (GC-TOF-MS) techniques, respectively. The mean concentrations of the total PBDE varied in the range of 0.06 – 2.47ng/g in the Diep River. These values were relatively higher in the Kuils River. The mean concentrations of BB 153 ranged from not detected (ND) –0.39ng/g. Similarly, the mean concentrations of BB 153 in the Kuils River were in the range of ND –1.21ng/g. The statistical analyses performed on these data showed that majority of the PBDE congeners, except BDE 209 had strong positive correlation with the total organic carbon (TOC). Although effluent discharges from nearby wastewater treatment plants were identified as important source of PBDEs, other notable sources, including grey water intrusion could contribute to the contamination of the upstream of both rivers.

Perfluorooctanoate and perfluorooctane sulfonate in South African river water

This study examined the prevalence of perfluorooctanoate (PFOA) and perfluorooctane sulfonate (PFOS) in river water samples (n = 56) and suspended solids (n = 5) from three major Western Cape rivers, in South Africa. Solid phase extraction (SPE) followed by liquid chromatography combined with electrospray tandem mass spectrometry (LC-MS/MS) using an analytical method developed in ISO 25101 (2009), PFOS and PFOA concentration in river water and in suspended solids from the rivers was investigated and quantified. From the results, PFOA and PFOS were detected in all the river water samples and were found in concentrations up to 314 and 182 ng/L for Diep River; 390 and 47 ng/L for Salt River; and 146 and 23 ng/L for Eerste River, respectively. In suspended solids, concentrations for PFOS and PFOA were 28 and 26 ng/g for Diep River; 16 and less than limit of detection for Eerste River; and 14 and 5 ng/g for Salt River, respectively. Some of these concentrations are higher than those previously reported in similar studies in various countries, and this suggests there is a cause for concern, in the Western Cape, South Africa, particularly in catchments where river and ground water is drawn for agricultural purposes in the province.

Occurrence of polybrominated diphenyl ethers (PBDEs) and 2,2’,4,4’,5,5’-hexabromobiphenyl (BB-153) in water samples from the Diep River, Cape Town, South Africa

Until recently, studies reporting the concentrations of polybrominated diphenyl ethers (PBDEs) as well as polybrominated biphenyls (PBBs) are generally scarce in the literature. Consequently, this study was aimed to investigate the occurrence and concentrations of certain PBDE congeners (BDE 28, 47, 100, 99, 154, 153, 183 and 209) and BB 153 in river water samples collected bi-monthly from the Diep River. The routine analyses of the target compounds were performed using a high-capillary GC-microelectron capture detection, while their structural elucidation was assessed using GC-TOF-MS technique. The overall mean concentrations of the sum of the eight PBDE congeners were 2.60, 4.83 and 4.29 ng/L for the upstream, point of discharge and downstream sampling points, respectively. Similarly, the overall mean concentrations of BB 153 were 0.25, 4.85 and 1.56 ng/L for the upstream, point of discharge and downstream sampling points, respectively. BDE 47 was the dominant congener found in these samples contributing between 19 and 26 % to the total PBDEs across the sampling points. The statistical analyses performed on the results obtained showed that all the congeners, except BDE 209 in certain instances, had strong positive correlations with one another, thus suggesting that these contaminants could be emanating from the same source. In this study, potential sources of these pollutants other than WWTP discharges into the investigated river were also identified. However, the relatively high concentrations of the target compounds found at the point of discharge sampling point coupled with the large volume of treated effluent being discharged suggested that the contributions from this source could be very significant over time.

Investigation into the metal contamination of the Plankenburg and Diep Rivers, Western Cape, South Africa

Metal contamination in the Plankenburg and Diep Rivers (Western Cape) was investigated over a 12 and 9 month period, respectively. Aluminium (Al), copper (Cu), iron (Fe), lead (Pb), manganese (Mn), nickel (Ni) and zinc (Zn) concentrations were determined using the nitric acid digestion method and analysed by inductively coupled plasma atomic emission spectrometry (ICP-AES). For both rivers the Al and Fe concentrations were higher than that for all the other metals analysed for in sediment and water samples. The highest concentrations recorded in the Plankenburg River were 13.6 mgE.-1 (water . Week 18, Site B) and 15 018 mgEkg-1 (sediment . Week 1, Site C) for Al, and 48 mgE.-1 (water . Week 43, Site A) and 14 363.8 mgEkg-1 (sediment . Week 1, Site A) for Fe. The highest concentrations recorded in the Diep River were 4 mgE.-1 (water . Week 1, Site A) and 19 179 mgEkg-1 (sediment . Week 1, Site C) for Al, and 513 mgE.-1 (water . Week 27, Site A) and 106 379.5 mgEkg-1 (sediment . Week 9, Site C) for Fe. For most of the metals analysed the concentrations were higher than the recommended water quality guidelines as stipulated by the Department of Water Affairs and Forestry, the Canadian Council for the Ministers of the Environment and the accepted eworld averagef. Point sources of pollution could not be conclusively identified, but runoff from both industrial and residential areas could have contributed to the increased concentrations. Metal concentrations should be routinely monitored and the guidelines should be updated and revised based on the current state of the rivers and pollution sources.

Assessment of Metal Concentrations, Chlorophyll Content and Photosynthesis in Phragmites australis along the Lower Diep River, CapeTown, South Africa

Phragmites australis growing at 4 selected sites along the bank of the lower Diep River, Cape Town, South Africa and in adjacent soil was assessed for photosynthesis, chlorophyll content and metal concentrations in shoots and roots. The rate of photosynthesis was determined using the Infra - red gas analyzer (IRGA). Chlorophyll content of leaves was determined by extraction of the pigments using dimethyl sulphoxide (DMSO). Chlorophyll was quantified from the extract using a spectrophotometer (645 and 665 nm). Ten metals (cadmium, copper, iron, lead, manganese, nickel, zinc, aluminium, chromium, and cobalt) in the shoots and roots of Phragmites australis were measured by ICP-MS. The abundance of the metals were in the order Al > Pb > Cd > Co > Ni > Cr; and for micronutrients, Fe > Mn > Zn > Cu both in the shoots and roots from all the sites investigated. Chlorophyll a, b and total chlorophyll (Chl.T), as well as photosynthesis were significantly lower in P. australis from the river bank compared with the adjacent soil. Increased metal loads in plants from the river bank were found to accompany the decreasing chlorophyll concentrations and photosynthetic rate. More metals were found to be accumulated in plants on the river bank compared to plants from adjacent to the river bank.

Accumulation and Distribution of Metals in Bolboschoenus maritimus (Cyperaceae), from a South African River

The Diep River is a major freshwater ecosystem in the Western Cape, South Africa. Although it is surrounded by many sources of metal pollution, the actual metal levels in this river system are unknown. Wetland plants are known to accumulate metals and may possibly be used as biomonitors of metal contamination in a river system. One such species, the sedge Bolboschoenus maritimus, is found in abundance along the banks of this river. The aim of this study was to investigate and monitor the degree of metal contamination in the water and sediments of the lower Diep River, as well as to study the seasonal accumulation and distribution of metals in B. maritimus, and the use thereof as biomonitor species. Two sampling sites were used: one site above the wetland section of the river, receiving runoff mainly from agricultural lands (site 1), and one site close to the river mouth (site 2), exposed to several possible pollution sources. Water, sediment, and plant (root, leaf and stem) samples were collected seasonally for 1 year and analyzed for Al, Zn, Cu, and Fe. There was greater bioaccumulation of metals by plants at site 2, due to greater bioavailability of metals. B. maritimus was shown to be a root accumulator of metals. Seasonal fluctuations in root, stem, and leaf metal concentrations did not follow seasonal sediment concentration patterns. However, using B. maritimus as test species did provide valuable additional information to sediment and water analyses. More extensive research is needed to conclude whether this species is an effective biomonitor in the lower Diep River environment.

Comparison of microbial contamination at various sites along the Plankenburg- and Diep Rivers, Western Cape, South Africa

This study was aimed at investigating and comparing the microbial contamination levels at various sites in the Plankenburg and Diep Rivers in the Western Cape, South Africa. Sampling of sites along the Plankenburg River started in June 2004 and continued for a period of 1 year until June 2005. Sampling of the Diep River sites started in March 2005 and continued for a period of 9 months until November 2005. Faecal coliform (FC) and E. coli (EC) counts were determined by means of the most probable number (MPN) technique, the number of culturable cells were determined using the heterotrophic plate count (HPC) technique and total microbial counts were evaluated by Flow cytometric analysis (FCM). The highest microbial counts for the Plankenburg River were observed at Site B where the highest MPN, FC, E. coli and total FCM counts of 9.2 x 106 (Week 14), 3.5 x 106 (Week 39) and 3.5 x 106 micro-organisms/100 m. (Week 39) and 2.1 x 108 micro-organisms/m. (Weeks 1 and 39) respectively, were recorded. The highest HPC recorded for the Plankenburg River was 7.9 x 106 micro-organisms/100 m. (Week 44, Site A). Site B is situated close to an informal settlement where waste effluents from stormwater drainage pipes enter the river system. In addition, other possible contamination sources included agricultural (Site A) and industrial (Site C) areas bordering the Plankenburg River. The highest total MPN, FC and E. coli counts in the Diep River were 5.4 x 106 (Week 23) and 1.6 x 106 micro-organisms/100 m. (FC and E. coli, respectively (both in Week 23)), recorded at Site B. The highest HPC and total FCM counts of 1.7 x 107 micro-organisms/100 m. (Week 14) and 2.5 x 109 micro-organisms/m. (Week 23), respectively, were also recorded at Site B. This site was identified as the most contaminated site along the Diep River and served as an accumulation point for waste effluents from the residential and industrial areas, which included paint and machine manufacturers. Other sources situated along the Diep River included storage and maintenance facilities for steel containers, a wastewater treatment plant and an oil-refinery. Most of the bacterial counts obtained for the Plankenburg and Diep Rivers exceeded the accepted maximum limit for river water for most of the sampling period.

THE ECOLOGY OF SOUTH AFRICAN ESTUARIES

Section A describes the topography and physico-chemical characteristics of the Milnerton river system. Slightly brackish water from the Diep River flows into the shallow basin of Riet Vlei and from there escapes through Milnerton Lagoon into the sea. The estuary is open to the sea during winter and spring and is closed by a sand-bar in summer. In late summer Diep River and Riet Vlei dry up, the Lagoon becomes hypersaline and a reversed salinity gradient is established. The interaction of the various physical factors is discussed. The biotic divisions of the system are discussed in Section B, and the fauna and flora of each part are described. Seasonal changes are discussed in relation to the changing environment. The fauna of the Milnerton river system is compared with that of other South African estuaries. An annotated faunistic list is appended.