Cameron Highlands is a mountainous region with steep slopes. Gradients exceeding 20∘ are common. The climate is favourable to the cultivation of tea, sub-tropical vegetables and flowers (under rain-shelter).
Crop production is sustained by high fertiliser and manure applications. However, agriculture in this environment is characterised
by high levels of soil erosion and environmental pollution. A study on the sustainability of these agro-ecosystems was conducted.
Results indicated that soil loss was in the range of 24–42 ton/ha/yr under vegetables and 1.3 ton under rain-shelter. Sediment
load in the vegetable sub-catchment reached 3.5 g/L, 50 times higher than that associated with flowers under rain-shelter
and tea. The sediments contained high nutrient loads of up to 470 kg N/ha/yr. The N, P and K lost in runoff from cabbage farms
was 154 kg/season/ha, whereas in chrysanthemum farms it was 5 kg. In cabbage farms, the N, P, and K lost through leaching
was 193 kg/season/ha. The NO3–N concentration in the runoff from the cabbage farms reached 25 ppm but less than 10 ppm in runoff from rain-shelters. Inorganic
pollution in the rivers was within the acceptable limit of 10 ppm. The sustainability of the agro-ecosystems is in the order
of tea { > } rain–shelter ≫ vegetables. 相似文献
Cadmium solubility and sorption in an arable clay loam soil that had received sewage sludge for 41 years were compared to an unsludged control in batch studies. Soil pH dominated Cd sorption, explaining >92% of the variation in Kd values in both treatments. At any pH, Cd sorption was apparently slightly but significantly (p < 0.05) smaller in the sludge-amended soil compared to the control, even though the organic carbon content was 70% larger and the ammonium oxalate-extractable iron content was roughly doubled. Correction for dissolved organic carbon (DOC) complexation with the speciation model WHAM reduced the difference in sorption between treatments, but the sludged soil still had significantly smaller Kd values (p < 0.01). Batch equilibrations without addition of Cd showed that there was no significant difference in the solubility of "native" cadmium (defined as EDTA-extractable Cd) in sludged and control soils. The reason for the lack of increase in Cd sorption in the sludge-amended soil has not been established, but it may be due to competition for sorption sites on humic compounds with sludge-derived Fe and trace metals such as zinc. The fact that the pyrophosphate-extractable (i.e., organically associated) iron content was seven times larger in the sludged soil provides some supporting evidence for this hypothesis. 相似文献
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. 相似文献
Conservation organizations have increasingly raised concerns about escalating rates of illegal hunting and trade in wildlife. Previous studies have concluded that people hunt illegally because they are financially poor or lack alternative livelihood strategies. However, there has been little attempt to develop a richer understanding of the motivations behind contemporary illegal wildlife hunting. As a first step, we reviewed the academic and policy literatures on poaching and illegal wildlife use and considered the meanings of poverty and the relative importance of structure and individual agency. We placed motivations for illegal wildlife hunting within the context of the complex history of how wildlife laws were initially designed and enforced to indicate how hunting practices by specific communities were criminalized. We also considered the nature of poverty and the reasons for economic deprivation in particular communities to indicate how particular understandings of poverty as material deprivation ultimately shape approaches to illegal wildlife hunting. We found there is a need for a much better understanding of what poverty is and what motivates people to hunt illegally. 相似文献
Pollutant emissions from co-firing of refuse derived fuel (RDF) and coal were investigated in a vortexing fluidized bed combustor (VFBC). RDF-5 was made of common municipal solid waste (MSW). CaCO3 was injected in the combustor to absorb HCl at 850 °C. The results show that NOx and HCl emissions increase with RDF-5 co-firing ratio. The NOx concentration in flue gas at the bottom of the combustor is higher than that at the top. However, the trend of HCl released is reverse compared with NOx emissions. It was found that the HCl concentration decreases with increasing the molar ratio of Ca/Cl. However, the effect of CaCO3 addition on HCl retention is not significant when the molar ratio of Ca/Cl is higher than 5. The chlorine content in fly ash increases obviously with the molar ratio of Ca/Cl. PCDD/Fs emissions decrease slightly with an addition of CaCO3. In this study incomplete combustion is regarded as the main cause for polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) formation. 相似文献
Environmental Science and Pollution Research - The aim of this study was to analyze dispersion behavior characteristics and pollution hazard risk after a release of liquid chlorine. A full-scale... 相似文献
Animal manure is an important source of antibiotics and antibiotic resistance genes (ARGs) in the environment. However, the difference of antibiotic residues and ARG profiles in layer and broiler manure as well as their compost remains unexplored. In this study, we investigated the profiles of twelve antibiotics, seventeen ARGs, and class 1 integrase gene (intI1) in layer and broiler manure, and the corresponding compost at large-scale. Compared with layer manure, broiler manure exhibited approximately six times more residual tetracyclines, especially chlortetracycline. The relative abundances of qnrS and ermA genes in broiler manure were significantly higher than those in layer manure. The concentration of tetracyclines not only had a significantly positive correlation with tetracycline resistance genes (tetA and tetC) but was also positively correlated with quinolone resistance (qepA, qnrB, and qnrS) and macrolide resistance (ermA and ermT). Most ARGs in manure were reduced after composting. However, the relative abundance of sulfonamide resistance gene sul1 increased up to 2.41% after composting, which was significantly higher than that of broiler (0.41%) and layer (0.62%) manure. The associated bacterial community was characterized by high-throughput 16S rRNA gene sequencing. The relative abundances of thermophilic bacteria had significant positive correlations with the abundance of sul1 in compost. The composting has a significant impact on the ARG-associated gut microbes in poultry manure. Variation partitioning analysis indicated that the change of bacterial community compositions and antibiotics contributed partially to the shift in ARG profiles. The results indicate that at industry-scale production broiler manure had more antibiotics and ARGs than layer manure did, and composting decreased most ARG abundances in poultry manure except for sulfonamide resistance genes.