Botswana's environmental policy on recycling

Recycling operations have become one of the primary strategies for waste management, worldwide. Especially, recycling operations are viewed as among the most effective techniques for reducing the amount of municipal solid waste disposed at landfill sites. Botswana's environmental policy on recycling stipulates, among others, that all waste management authorities should provide information on the classification and quantities of controlled waste targeted for recycling. This paper, therefore, examines the extent to which recycling operations in Botswana have either been conducted in compliance with or in violation of some major environmental requirements as enunciated on statutory guidelines. Compatibility between environmental policies on recycling and actual practice is evaluated focusing on two companies (Dumatau trading and Botswana Tissue) involved in recycling operation. Data from the two companies is complemented by one collected from the Gaborone landfill site. Finally, this study discusses on the role played by various stakeholders in policy formulation and implementation with particular emphasis being placed on a select number of non-governmental organisations (NGO).     

Runoff phosphorus losses from surface-applied biosolids

Runoff losses of dissolved and particulate phosphorus (P) may occur when rainfall interacts with manures and biosolids spread on the soil surface. This study compared P levels in runoff losses from soils amended with several P sources, including 10 different biosolids and dairy manure (untreated and treated with Fe or Al salts). Simulated rainfall (71 mm h(-1)) was applied until 30 min of runoff was collected from soil boxes (100 x 20 x 5 cm) to which the P sources were surfaced applied. Materials were applied to achieve a common plant available nitrogen (PAN) rate of 134 kg PAN ha(-1), resulting in total P loading rates from 122 (dairy manure) to 555 (Syracuse N-Viro biosolids) kg P ha(-1). Two biosolids produced via biological phosphorus removal (BPR) wastewater treatment resulted in the highest total dissolved phosphorus (13-21.5 mg TDP L(-1)) and total phosphorus (18-27.5 mg TP L(-1)) concentrations in runoff, followed by untreated dairy manure that had statistically (p = 0.05) higher TDP (8.5 mg L(-1)) and TP (10.9 mg L(-1)) than seven of the eight other biosolids. The TDP and TP in runoff from six biosolids did not differ significantly from unamended control (0.03 mg TDP L(-1); 0.95 mg TP L(-1)). Highest runoff TDP was associated with P sources low in Al and Fe. Amending dairy manure with Al and Fe salts at 1:1 metal-to-P molar ratio reduced runoff TP to control levels. Runoff TDP and TP were not positively correlated to TP application rate unless modified by a weighting factor reflecting the relative solubility of the P source. This suggests site assessment indices should account for the differential solubility of the applied P source to accurately predict the risk of P loss from the wide variety of biosolids materials routinely land applied.     

Residues of endosulfan and other selected organochlorine pesticides in farm areas of the Lower Fraser Valley, British Columbia, Canada

Crop soils, ditch sediments, and water flowing from several farm areas to salmon tributary streams of the Fraser River in the Lower Fraser Valley (LFV) of British Columbia, Canada, were sampled in 2002-2003 to quantify for residues of an organochlorine cyclodiene pesticide, endosulfan (END = alpha-endosulfan + beta-endosulfan + endosulfan sulfate). Residues from historical use of other selected organochlorine pesticides, namely, cyclodienes (aldrin, alpha-chlordane, gamma-chlordane, dieldrin, endrin, endrin aldehyde, heptachlor, and heptachlor epoxide), hexachlorocyclohexanes [alpha-benzene-hexachloride (alpha-BHC), beta-BHC, delta-BHC, and gamma-BHC (lindane)], and DDT-related compounds (p,p-DDT, p,p-DDD, p,p-DDE, and methoxychlor) were also determined. Reference and background levels of these pesticides in ditches leading to fish streams were obtained from pristine watershed areas. Varying amounts of END residues were detected in soils (<0.02-5.60 mg kg(-1) dry wt.) and ditch sediments (<0.02-3.33 mg kg(-1) dry wt.) in mainly three of five farm areas sampled. Likewise, residues (excluding END) of other selected organochlorine compounds such as aldrin, BHC, chlordane, endrin, p,p-DDT, methoxychlor, and their respective major transformation products (endosulfan sulfate, dieldrin, endrin aldehyde, heptachlor, heptachlor epoxide, p,p-DDD, and p,p-DDE) were found in crop soils (<0.02-16.2 mg kg(-1) dry wt.) and sediments (<0.02-9.73 mg kg(-1) dry wt.). Most of these pesticides (END: <0.01-1.86 microg L(-1); other selected organochlorine pesticides: <0.0.1-1.50 microg L(-1)) were also found in ditch water leading to salmon streams in several farms. The END levels of crop soils from the same LFV study farms in 1994 and 2003 indicated an estimated decline of 22% to 1.35 mg kg(-1) dry wt. during that period. This reduction was probably due to the increasing use of alternate pesticides (e.g., organophosphorus compounds). Some possible biological implications of these pesticide residues on nontarget organisms in the LFV are discussed.     

The acetochlor registration partnership surface water monitoring program for four corn herbicides

A surface drinking water monitoring program for four corn (Zea mays L.) herbicides was conducted during 1995-2001. Stratified random sampling was used to select 175 community water systems (CWSs) within a 12-state area, with an emphasis on the most vulnerable sites, based on corn intensity and watershed size. Finished drinking water was monitored at all sites, and raw water was monitored at many sites using activated carbon, which was shown capable of removing herbicides and their degradates from drinking water. Samples were collected biweekly from mid-March through the end of August, and twice during the off-season. The analytical method had a detection limit of 0.05 microg L(-1) for alachlor [2-chloro-N-(2,6-diethylphenyl)-N-(methoxymethyl)-acetamide] and 0.03 microg L(-1) for acetochlor [2-chloro-N-(ethoxymethyl)-N-(2-ethyl-6-methylphenyl)-acetamide], atrazine [6-chloro-N-ethyl-N'-(1-methylethyl)-1,3,5-triazine-2,4-diamine], and metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)-acetamide]. Of the 16528 drinking water samples analyzed, acetochlor, alachlor, atrazine, and metolachlor were detected in 19, 7, 87, and 53% of the samples, respectively. During 1999-2001, samples were also analyzed for the presence of six major degradates of the chloroacetanilide herbicides, which were detected more frequently than their parent compounds, despite having higher detection limits of 0.1 to 0.2 microg L(-1). Overall detection frequencies were correlated with product use and environmental fate characteristics. Reservoirs were particularly vulnerable to atrazine, which exceeded its 3 microg L(-1) maximum contaminant level at 25 such sites during 1995-1999. Acetochlor annualized mean concentrations (AMCs) did not exceed its mitigation trigger (2 microg L(-1)) at any site, and comparisons of observed levels with standard measures of human and ecological hazards indicate that it poses no significant risk to human health or the environment.     

BIOECONOMIC ANALYSIS OF SELECTED CONSERVATION PRACTICES ON SOIL EROSION AND FRESHWATER FISHERIES1

ABSTRACT: Farmers can generate environmental benefits (improved water quality and fisheries and wildlife habitat), but they may not be able to quantify them. Furthermore, farmers may reduce their incomes from managing lands to produce these positive externalities but receive little monetary compensation in return. This study simulated the relationship between agricultural practices, water quality, fish responses to suspended sediment and farm income within two small watersheds, one of a cool water stream and one of a warm water stream. Using the Agricultural Drainage and Pesticide Transport (ADAPT) model, this study related best management practices (BMPs) to calculated instream suspended sediment concentrations by estimating sediment delivery, runoff, base flow, and streambank erosion to quantify the effects of suspended sediment exposure on fish communities. By implementing selected BMPs in each watershed, annual net farm income declined $18,000 to $28,000 (1 to 3 percent) from previous levels. “Lethal” fish events from suspended sediments in the cool water watershed decreased by 60 percent as conservation tillage and riparian buffers increased. Despite reducing suspended sediments by 25 percent, BMPs in the warm water watershed did not reduce the negative response of the fisheries. Differences in responses (physical and biological) between watersheds highlight potential gains in economic efficiency by targeting BMPs or by offering performance based “green payments.”     

DRY AND WET WEATHER FLOW NUTRIENT LOADS FROM A LOS ANGELES WATERSHED1

Effective watershed management requires an accurate assessment of the pollutant loads from the associated point and nonpoint sources. The importance of wet weather flow (WWF) pollutant loads is well known, but in semi‐arid regions where urbanization is significant the pollutant load in dry weather flow (DWF) may also be important. This research compares the relative contributions of potential contaminants discharged in DWF and WWF from the Ballona Creek Watershed in Los Angeles, California. Models to predict DWF and WWF loads of total suspended solids, biochemical oxygen demand, nitrate‐nitrogen, nitrite‐nitrogen, ammonia‐nitrogen, total Kjeldahl nitrogen, and total phosphorus from the Ballona Creek Watershed for six water years dating from 1991 to 1996 were developed. The contaminants studied were selected based on data availability and their potential importance in the degradation of Ballona Creek and Santa Monica Bay beneficial uses. Wet weather flow was found to contribute approximately 75 percent to 90 percent of the total annual flow volume discharged by the Ballona Creek Watershed. Pollutant loads are also predominantly due to WWF, but during the dry season, DWF is a more significant contributor. Wet weather flow accounts for 67 to 98 percent of the annual load of the constituents studied. During the dry season, however, the portion attributable to DWF increases to greater than 40 percent for all constituents except biochemical oxygen demand and total suspended solids. When individual catchments within the watershed are considered, the DWF pollutant load from the largest catchment is similar to the WWF pollutant load in two other major catchments. This research indicates WWF is the most significant source of nonpoint source pollution load on an annual basis, but management of the effects of the nonpoint source pollutant load should consider the seasonal importance of DWF.     

BASE FLOW RECESSION RATES,LOW FLOWS,AND HYDROLOGIC FEATURES OF SMALL WATERSHEDS IN PENNSYLVANIA,USA1

This paper examines the relationships between measurable watershed hydrologic features, base flow recession rates, and the Q_7,10 low flow statistic (the annual minimum seven‐day average streamflow occurring once every 10 years on average). Base flow recession constants were determined by analyzing hydrograph recession data from 24 small (>130 km²), unregulated watersheds across five major physiographic provinces of Pennsylvania, providing a highly variable dataset. Geomorphic, hydrogeologic, and land use parameters were determined for each watershed. The base flow recession constant was found to be most strongly correlated to drainage density, geologic index, and ruggedness number (watershed slope); however, these three parameters are intercorrelated. Multiple regression models were developed for predicting the recession rate, and it was found that only two parameters, drainage density and hydrologic soil group, were required to obtain good estimates of the recession constant. Equations were also developed to relate the recession rates to Q_7,10 per unit area, and to the Q_7,10/Q₅₀ ratio. Using these equations, estimates of base flow recession rates, Q_7,10, and streamflow reduction under drought conditions can be made for small, ungaged basins across a wide range of physiography.     

Biological treatment of clogged emitters in a drip irrigation system

This study was conducted to investigate microbial organisms that can be used for preventing clogging in drip irrigation systems caused by biological factors. A total of 25 fungi isolate and 121 bacterial strains were isolated from water samples collected from drip irrigation systems in tomato greenhouses in the eastern Anatolia region of Turkey in the spring season of 2001. Biological clogging of emitters in a model drip irrigation system was experimentally caused by application of the microorganisms (fungi and bacteria) isolated in the study. Three antagonistic bacterial strains in the genus Bacillus spp (ERZ, OSU-142) and Burkholdria spp (OSU-7) were used for treatment of biological clogging of the emitters. The results showed that the antagonistic bacterial strains tested have the potential to be used as anti-clogging agents for treatment of emitters in drip irrigation system. This is the first study that demonstrated that antagonistic microorganisms can be utilized for treatment of clogging in drip irrigation systems.     

Estimating the economic burden from illnesses associated with recreational coastal water pollution--a case study in Orange County, California

A cost-of-illness framework was applied to health and income data to quantify the health burden from illnesses associated with exposure to polluted recreational marine waters. Using data on illness severity due to exposure to polluted coastal water and estimates of mean annual salaries and medical costs (adjusted to 2001 values) for residents of Orange County, California, we estimated that the economic burden per gastrointestinal illness (GI) amounts to 36.58 dollars, the burden per acute respiratory disease is 76.76 dollars, the burden per ear ailment is 37.86 dollars, and the burden per eye ailment is 27.31 dollars. These costs can become a substantial public health burden when millions of exposures per year to polluted coastal waters result in hundreds of thousands of illnesses. For example, exposures to polluted waters at Orange County's Newport and Huntington Beaches were estimated to generate an average of 36,778 GI episodes per year. At this GI illness rate, one can also expect that approximately 38,000 more illness episodes occurred per year of other types, including respiratory, eye, and ear infections. The combination of excess illnesses associated with coastal water pollution resulted in a cumulative public health burden of 3.3 million dollars per year for these two beaches. This paper introduces a public health cost variable that can be applied in cost-benefit analyses when evaluating pollution abatement strategies.