The dynamics of agricultural and forestry biomass are highly sensitive to climate change, particularly in high latitude regions. Heilongjiang Province was selected as research area in North-east China. We explored the trend of regional climate warming and distribution feature of biomass resources, and then analyzed on the spatial relationship between climate factors and biomass resources. Net primary productivity (NPP) is one of the key indicators of vegetation productivity, and was simulated as base data to calculate the distribution of agricultural and forestry biomass. The results show that temperatures rose by up to 0.37°C/10a from 1961 to 2013. Spatially, the variation of agricultural biomass per unit area changed from -1.93 to 5.85 t·km–2·a–1 during 2000–2013. More than 85% of farmland areas showed a positive relationship between agricultural biomass and precipitation. The results suggest that precipitation exerts an overwhelming climate influence on agricultural biomass. The mean density of forestry biomass varied from 10 to 30 t·km–2. Temperature had a significant negative effect on forestry biomass in Lesser Khingan and northern Changbai Mountain, because increased temperature leads to decreased Rubisco activity and increased respiration in these areas. Precipitation had a significant positive relationship with forestry biomass in south-western Changbai Mountain, because this area had a warmer climate and stress from insufficient precipitation may induce xylem cavitation. Understanding the effects of climate factors on regional biomass resources is of great significance in improving environmental management and promoting sustainable development of further biomass resource use.
Pentachlorophenol (PCP) was investigated in freshwater sediments and human breast milk collected from the Pearl River Delta, China. The average level of PCP in river sediments was 7.93 ng/g based on dry weight, ranging from 1.44 to 34.4 ng/g. As to the sediments from fishponds, samples from Zhongshan had the highest PCP levels (37.5 ng/g on average), followed by Dongguan (21.1 ng/g on average) and the least in Shenzhen (3.69 ng/g on average) and Shunde (2.20 ng/g on average). Negative relationship was obtained between the PCP level and pH value in sediment (r=0.553, n=13, p<0.05), while positive relationship was found between the PCP levels and the total organic matter (TOM) levels in sediment (r=0.700, n=17, p<0.01). These results indicated that pH and TOM played important roles during the process of PCP settling down to the sediment. PCP was also detected in human breast milk with an average of 2.15 ng/g. The PCP concentration increased with the age increasing of donors. The estimated PCP body burden for mother, daily and yearly PCP intake of infants ranged from 0.16 to 4.17 mg/person, from 0.26 to 10.23 mug/infant.day and from 0.09 to 3.73 mg/infant.year, respectively. 相似文献
The direct contact membrane distillation applied for fluoride removal from brackish groundwater was investigated.The self-prepared polyvinylidene fluoride membrane exhibited high rejection of inorganic salt solutes.The maximum permeate flux 35.6 kg/(m2 ·hr) was obtained with the feed solution at 80°C and the cold distillate water at 20°C.The feed concentration had no significant impact on the permeate flux and the rejection in fluoride.The precipitation of CaCO3 would clog the hollow fiber inlets and foul the membrane surface with increasing concentration factor when natural groundwater was used directly as the feed,which resulted in a rapid decline in the module efficiency.This phenomenon was diminished by acidification of the feed.The experimental results showed that the permeate flux and the quality of obtained distillate kept stable before concentration factor reached 5.0 with the acidified groundwater as feed.The membrane module efficiency began to decline gradually when the feed continued to be concentrated,which can be mainly attributed to the formation of CaF2 deposits on the membrane surface.In addition,a 300 hr continuous fluoride removal experiment of acidified groundwater was carried out with concentration factor at 4.0,the permeate flux kept stable and the permeate fluoride was not detected. 相似文献
The feasibility of employing nanofiltration for the removal of chromium(VI) from wastewater was investigated. Poly (m-phenylene
isophthalamide) (PMIA) was used to fabricate asymmetric nanofiltration membrane through the phase-inversion technique. Scanning
electron microscopy (SEM) and atomic force microscopy (AFM) were used to characterize the obtained membrane, and the both
confirmed a much smoother surface which could reduce membrane fouling. The PMIA membrane showed di erent rejections to
electrolytes in a sequence of Na2SO4 > MgSO4 > NaCl > MgCl2, which was similar to the sequence of the negatively charged
nanofiltration membranes. Separation experiments on chromium(VI) solution were conducted at various operating conditions, such
as feed concentration, applied pressure and pH. It is concluded that chromium(VI) could be e ectively removed from chromiumcontaining
wastewater by the PMIA nanofiltration membranes while maintaining their pollution resistance under alkaline condition. 相似文献
ZnBiYO4 was synthesized by a solid-state reaction method for the first time. The structural and photocatalytic properties of ZnBiYO4 were characterized by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy and UV–Vis diffuse reflectance.ZnBiYO4 crystallized with a tetragonal spinel structure with space group I41/A. The lattice parameters for ZnBiYO4 were a = b = 11.176479 and c = 10.014323 . The band gap of ZnBiYO4 was estimated to be 1.58 e V. The photocatalytic activity of ZnBiYO4 was assessed by photodegradation of methyl orange under visible light irradiation. The results showed that ZnBiYO4 had higher catalytic activity compared with N-doped Ti O2 under the same experimental conditions using visible light irradiation. The photocatalytic degradation of methyl orange with ZnBiYO4 or N-doped Ti O2 as catalyst followed first-order reaction kinetics, and the first-order rate constant was 0.01575 and 0.00416 min-1for ZnBiYO4 and N-doped Ti O2, respectively. After visible light irradiation for 220 min with ZnBiYO4 as catalyst, complete removal and mineralization of methyl orange were observed. The reduction of total organic carbon, formation of inorganic products, SO2-4and NO-3, and evolution of CO2 revealed the continuous mineralization of methyl orange during the photocatalytic process. The intermediate products were identified using liquid chromatography–mass spectrometry. The ZnBiYO4/(visible light) photocatalysis system was found to be suitable for textile industry wastewater treatment and could be used to solve other environmental chemical pollution problems. 相似文献
