Environmental Impact of Heavy Metals from Poultry Waste Discharged into the Olosuru Stream , Ikire , Southwestern Nigeria

Rivers play a vital role in rural communities, particularly for the fishing industry, for agricultural purposes and as a source of water for local people.1,2 River contamination affects humans directly and indirectly. However, increasing anthropogenic activities and natural processes decrease the quality of water and pose a threat to all forms of life. Poultry farms provide one of the leading sources of high-grade, protein-rich foods (eggs and meat) globally, however, domestic, industrial and agricultural poultry wastes are regularly discarded into water bodies.3


Introduction
Rivers play a vital role in rural communities, particularly for the fishing industry, for agricultural purposes and as a source of water for local people. 1,2 River contamination affects humans directly and indirectly. However, increasing anthropogenic activities and natural processes decrease the quality of water and pose a threat to all forms of life. Poultry farms provide one of the leading sources of high-grade, protein-rich foods (eggs and meat) globally, however, domestic, industrial and agricultural poultry wastes are regularly discarded into water bodies. 3 According to Okonkwo et al., about 10 percent of the Nigerian population is engaged in poultry production, mostly at subsistence levels or on small and medium-sized farms. 4 The increased use of trace elements as nutritional supplements in poultry diets to improve feed efficiency, facilitate weight increase and for disease prevention results in high levels of trace elements in poultry waste. 5,6 Many metals are added to poultry feed, including copper (Cu), manganese (Mn), iron (Fe), selenium (Se), zinc (Zn), and arsenic (As). Iron and Cu are added to prevent anemia, selenium is added to prevent oxidative damage to cells, and Zn and Mn are added to ensure proper egg shell deposition and feather development. Antioxidants are added to retard degradation of vitamins in feed. Tranquilizers maybe used to keep flocks quiet in the house and before transport. A broad spectrum of antibiotics maybe added to poultry feed, both to combat pests and to increase availability of certain nutrients. Topical pesticides are used to combat flies, lice, beetles and mice. 7 Unfortunately, contaminants from poultry farms can have adverse effects Research on air, soil and water quality if their wastes are improperly managed and disposed of into the environment. 8 The improper disposal of wastes generated by poultry operations has been a long-standing concern due to the contribution to nutrient pollution in water resources. 9 Poultry wastes can degrade water quality when they are channeled directly into surface water or enter water bodies via surface runoff. The main environmental and health risks associated with animal wastes are the introduction of pollutants such as nutrients (including nitrogen and phosphorous), organic matter, sediments, pathogens (including bacteria and viruses) and heavy metals. 10 The danger lies in accumulation of manure-borne metals, since they are not biodegradable and eventually become phytotoxic. 11 Longterm application of poultry waste on soil has also been shown to result in accumulation of trace elements, increasing the potential bioavailability and toxicity of metals in the environment. 12-15 Such accumulation has the potential of restricting soil function, contaminating the food chain and water, and causing toxicity to plants, animals, water and humans. 16,17 Poultry waste is more toxic than other animal wastes. 18 Land application of poultry manure may result in the uptake of toxicants by plants, animals and humans through absorption, ingestion, bioaccumulation or other processes. Following the introduction of heavy metal contaminants into a river, whether via natural or anthropogenic sources, they partition between aqueous (pore water and overlying water) and solid phases (sediment, suspended particulate matter and biota). 19,20 Although some heavy metals are required as micronutrients, they can be toxic when present in higher amounts than their requirements. Anthropogenic metals may consistently persist within water bodies or maybe taken up by organisms such as plankton, benthos or fish and finally transferred to humans. 21 As heavy metals cannot be degraded, they are deposited, assimilated or incorporated in water, sediment and aquatic animals, thus causing heavy metal pollution in water bodies. 22 Lead is a toxic metal that is particularly harmful to children. 23 Lead affects the central and peripheral nervous system, organs, bones and kidneys. 24 Lead has no beneficial biological function and is known to accumulate in the body. 25-27 Lead exposure can cause adverse health effects, especially in young children and pregnant women, since Pb is a neurotoxin that permanently interrupts normal brain development. It also accumulates in the skeleton and its mobilization from bones during pregnancy and lactation causes exposure to fetuses and breastfed infants. 28,29 Lead on a cellular and molecular level may increase carcinogenic events involved in DNA damage and suppress DNA repairs and regulation of tumors. 30 A number of studies have been carried out on heavy metal concentrations in animal feeds and manure. Hill et al. carried out an experiment on the impact of animal waste application on runoff water quality in field experimental plots and concluded that a major concern of using animal waste as a source of fertilizer is the potential of degrading any nearby natural water sources. 31 Zhang et al. studied the heavy metal content of poultry waste collected from several farms in northeast China, with concentrations ranging from 2.88-98.08 mg/kg, 0.02-6.42 mg/ kg and non-detectable-8.00 mg/kg for Cu, As and cadmium (Cd) respectively. Their results indicate that some animals can build up heavy metals through their feed. 32 Islam et al. found that the various sources of raw materials used for poultry feed production are likely associated with anthropogenic heavy metal pollution. They also reported mean concentrations of heavy metals in some poultry feeds sold in Bangladesh ranging from 0.1852-0.0232 ppm for Cd, 20.6498-0.6019 ppm for lead (Pb), 0.7640-0.0069 ppm for As, 0.0579-0.0116 ppm for mercury (Hg), 0.0347-0.0069 ppm for Se, 5.7875-0.0926 ppm for chromium (Cr), 302.2001-0.0695 ppm for Mn, 5.1625-0.0125 ppm for nickel 37.5725-0.0463 ppm for Cu and 422.3023-0.0232 ppm for Zn. 33 The present study of the Olosuru stream is important, as residents of Olosuru village obtain water for domestic purposes from the stream only a few meters upstream from a poultry farm discharge point. Additionally, agricultural products, including vegetables and banana are cultivated along the path of the stream after the point of discharge. Thus, the aim of the present study was to assess the environmental stress and potential harm in relation to heavy metal concentrations that can result from improper discharge of untreated poultry wastes on the water quality of Olosuru stream at Ikire, southwest Nigeria.

Methods
This present study was carried out on a stretch of the Olosuru stream (latitudes 07º20' N -07º22'N; Longitude 004º10'E Research -004º11'E), which is a tributary of the Asejire River, southern Nigeria ( Figure 1). The Olosuru stream drains into Asejire River at Ikire, Osun State. The headquarters of Irewole Local Government area of Osun State is located in the Ikire urban area. The Local Government Area shares boundaries with Ayedire to the north, to the south with Isokan, to the east with Ayedaade, and to the south east by Ife-North Local Government Areas of Osun state respectively. It also bounds with Egbeda Local Government Area of Oyo state to the west. Ikire Urban area has a land mass of approximately 270 km 2 . According to the 2006 census by the National Population Council, Ikire had an estimated population of about 144,000. 34 The climate of the area is humid and tropical with a mean annual temperature of about 27ºC and a mean annual rainfall of over 1,400 mm. A geology survey map indicates that the basement complex in this area are migmatised, gneisses and granite. There are occurrences of schist and quartzite, occasionally amphibolite, gabro, diorites; the dominant in the studied area is gneisses. 35,36 The soils are primarily well-drained, Apomuseries soils known as cambicarenosols. 37 The study area falls within the rainforest belt of Nigeria, with a wet season (April to October) and a dry season (November to March).

Sampling stations and collection
Three sampling stations were established along the stream namely: upstream (A), the discharge point (B) and downstream (C). The upstream station was located about 500 meters away from the discharge point at Olosuru community. Human activities here include mechanical workshops, car washes and occasional road side oil spillage. The discharge point was located where poultry waste is directly discharged into the stream. The downstream sampling point is about 500 meters from the discharge point. This station was established to determine the recovery ability of the stream from the discharge point. The downstream station has the highest level of human activities/disturbance, including bathing, swimming, local fishing and washing of clothes and household utensils.
Water samples were collected six times, from the rainy season (September, October 2014 and April 2015) through the dry season (November 2014, January and February 2015) to study changes in heavy metal loads. Water samples were collected in 2-litre double-capped polyethylene bottles prewashed with detergent diluted with nitric acid and double distilled deionized water. In the field, sampling bottles and covers were rinsed three times with sampling water prior to sampling. Samples were acidified with 1% nitric acid to prevent heavy metals from adhering to the wall of the sampling bottle and were subsequently stored at 4°C for a minimal period of time, before analysis, to minimize changes in the physico-chemical characteristics of the metals.

Heavy metal analysis
For each sampling station, a 50 ml water sample was measured into a 250 ml conical flask and digested with 10 ml nitric acid. The samples were heated on a hot plate to a reduced volume of 5-7 ml. Digested samples were filtered using Whatman No.4 filter paper and deionized water was added to increase the volume to 100 ml. A blank was also prepared as a control. 38 The determination of heavy metals in each sample was carried out using an atomic absorption spectrophotometer (PG-990 model) calibrated with the standard for each metal under investigation at individual wavelengths of 248.3, 283.3, 228.8, 279.4 and 119.3 nm for Fe, Pb, Cd, Mn and As, respectively.

Results
Cadmium was significantly positively correlated with As, Mn and Pb at p<0.01 and with Fe at p<0.05. Arsenic, Fe and Mn were significantly positively correlated with Pb at p<0.05. Lead had a positive significantly correlation with Mn at p<0.01 (Table 1).

Principal component analysis of heavy metals
Principal component analysis was established to identify the distribution of metals within the sampling areas. The first two components for the wet season accounted for 99.93% of the cumulative variation.   Generally, all of the selected heavy metals analyzed in the present study increased in concentration toward the downstream station, as shown in Table  3. The Cd concentration varied widely from 0.006 to 0.032 mg/L (0.015±0.001 mg/L) and the highest mean value was at the downstream station  Table 3).
The highest Cd concentration was recorded during the wet season (0.006-0.032 mg/L) and there was a significantly higher concentration recorded during the wet season (0.016±0.003 mg/L) compared to the dry season (0.015±0.001 mg/L) ( Table 4). The highest mean of Pb concentration occurred during the wet season (0.021±0.008 mg/L) compared to dry season (0.017±0.002 mg/L). The difference was highly significant Environmental Impact of Heavy Metals from Poultry Waste in Southwestern Nigeria

Figure 3 -Relationship between heavy metals in the Olosuru stream, Ikire, southwestern Nigeria
Oyewale, Adesakin, Aduwo Research (p<0.01). The mean concentration of Mn was higher during the wet season (0.085±0.013 mg/L) than the dry season (0.064±0.007 mg/L). Iron had a mean concentration of 0.220±0.012 during the wet season and 0.217±0.016 during the dry season. The highest mean concentration of As was recorded during the wet season (0.031±0.020 mg/L) and had a mean concentration of 0.013±0.001 mg/L during the dry season.
The overall coefficient of variation (CV) for Cd was low (36.39%). However, a higher CV of Cd was recorded at the upstream station (39.54%) and during the wet season (46.52%). The overall CV recorded for Pb was also low (29.86%) compared with the CV recorded at the discharge point (59.81%). The CV of Pb recorded during the dry season (30.55%) was higher than the wet season (25.75%). The overall CV for Mn was high (45.49%), while the highest CV was recorded at the discharge station (47.40%) and the CV recorded during the wet season (42.56%) was higher than the dry season (32.11%). The overall CV recorded for Fe during the study period was low (27.11%), while a high CV was recorded at the discharge station (34.73%) and the CV recorded during the wet season (42.66%) was

Table 5 -Coefficient of Variation (%) of Heavy Metals Measured in the Olosuru Stream, Ikire, Southwestern Nigeria
Research higher than the dry season (41.43%). The overall CV recorded for As during the study period was low (38.63%), and the highest recorded CV occurred at the discharge point (46.37%) ( Table 5).

Discussion
The Cd concentrations recorded in the water samples collected from all the sampling stations across all seasons were above the United States Environmental Protection Agency (USEPA) permissible limit of 0.005 mg/L for drinking water. 39 The monthly mean concentrations were higher at the downstream station compared to the upstream station. The highest mean concentration of Cd was recorded at the downstream station during the wet season. The high Cd concentrations in the present study could be due to bioaccumulation and subsequent discharges of poultry waste into the stream at the discharge point. The results obtained in the present study are similar to a report by Alexieva et al., which found elevated concentrations of Cd in poultry and pig feed and manure in Bulgaria. 40 Heavy metals were also found to be retained in animal flesh and in some of their waste, indicating that significant concentrations of heavy metals in animal feed and waste can pose a threat to human health through water, soil and plant contamination. 40 These results align with those of a study by Taiwo  There is no guideline set by the National Environmental Standards and Regulations Enforcement Agency Federal Environmental Protection Agency (NESREA) for Fe content in drinking water, as it is not a health concern at concentrations normally observed in drinking water. 59 The mean As concentration observed in the present study was above the WHO (0.01 mg/L) recommended standard limits for drinking water. The highest mean value of As was observed at the downstream station, where there was a high level of human activity. The increase in As concentration in the present study could be due to the addition of As in poultry feed as an additive to control coccidiosis in chickens, which has resulted in a seven-fold increase in As levels in poultry waste. 60 It is now recognized that at least 140 million people in 50 Research countries have been drinking water containing arsenic at levels above the WHO provisional guideline value of 10 μg/L. 61 Arsenic occurs in two forms, organic As and inorganic As. Inorganic As compounds (such as those found in water) are highly toxic, while organic As compounds (such as those found in seafood) are less harmful to human health. Acute effects of As in water could lead to immediate symptoms such as vomiting, abdominal pain and diarrhea, while long-term effects can be observed in the skin and include pigmentation changes, skin lesions and hard patches on the palms and soles of the feet (hyperkeratosis). The International Agency for Research on Cancer has classified As and As compounds as carcinogenic to humans and has stated that As in drinking water is a carcinogen. 62

Conclusions
The heavy metals contents of the Olosuru stream in the present study were above acceptable limits for drinking water. The study also showed evidence of water pollution across all sampling stations, indicating that the water is not safe for consumption except when treated.