MODERN BIOGEOCHEMISTRY: SECOND EDITION Phần 9 potx

356 CHAPTER 17 Figure 19. Critical loads of sulfur at terrestrial ecosystems of South Korea (Park and Bashkin, 2001). the Pusan-Ulsan industrial agglomeration takes place and minimum in the north- eastern part. Accordingly, a significant part of Korean ecosystems was subjected n intensive input of S acid-forming compounds. The values of exceedances of sulfur deposition over sulfur critical loads (ExS) are shown in Figure 20. During 1994–1997 the S dep values were higher than CLmaxS values at about one third of terrestrial Korean ecosystems (38%). Among them, the ExS values were in the range 176–500 eq/ha/yr for 16.1% of total number of ecosystems, in the range of 500–1,000 eq/ha/yr were for 7.9%, in the range of 1,000–2,000 eq/ha/yr were 10.7% and the values even higher than 2,000 eq/ha/yr were found for 3.5% of Korean ecosystems. The other part of Korean territory (61.8%), where the sulfur depositions were relatively less but critical load values are relatively higher (see Figure 18), was not subjected to excessive input of sulfur-induced acidity. This area can be considered as sustainable to sulfur input. As we have mentioned above, during the 1990s up to 30–35% of sulfur deposition was due to emission of SO 2 by transboundary sources, occurred mainly in China. TRANSBOUNDARY N AND S AIR POLLUTION 357 Figure 20. Exceedances of critical loads of sulfur over South Korea (Park and Bashkin, 2001). Thus, the emission abatement strategy in South Korea has to be developed taking into account both local and transboundary emission reduction in the whole East Asian domain. The values of CL and their mapping can present a good possibility for the creation of ecological optimization models. At present, these CL values and corresponding mappings have been carried out by national research teams in almost all the East Asian countries, such as China, Japan, South Korea, Asian part of Russia and Taiwan (Bashkin and Park, 1998). Accordingly, this national-based mapping can be considered as a scientific basis for decreasing local and regional air pollution in the East Asian domain. 3.6. Acid Deposition Influence on the Biogeochemical Migration of Heavy Metals in Food Webs An interesting study of acid rain effects on the biogeochemical accumulation of heavy metals (Cd, Cu, Pb, and Zn) in crops has been presented by Chen et al., 1998. The authors have compared the ratios of relative concentration of four heavy metals in the brown rice and leaves of vegetables sampled from acid rain affected areas and 358 CHAPTER 17 Table 5. The ratios of relative concentration of heavy metals in brown rice and the leaves of vegetable species growing in Lung-tang area (affected by acidic rains) and Lung–luan–tang area (non-affected by acidic rains) from 1996 to 1997 in Taiwan (Chen et al., 1998). acid rain/non-acid Ratio in acid rain/non-acid rain affected area rain area Rice and vegetable species (sampling number) Cd Cu Pb Zn Rice Rice, (Oryza sativa Linn.) 24/15 1.25 1.05 1.09 1.03 Vegetables Sweet potato, (Ipomoea bataus) 14/9 1.00 1.45 1.07 1.11 Welsh onion, (Allium fistulosum) 10/12 0.89 1.48 3.08 2.03 Pickled cabbage, (Brassica chineniss) 3/10 5.03 1.23 — # 1.33 Chinese chives, (Allium tuberosum) 7/5 4.97 0.70 0.08 1.56 Mustard, (Brassica juncea) 2/4 — 1.59 — 2.19 Lettuce, (Lactuce sativa) 6/8 3.73 1.87 1.00 1.97 Chickweed, (Alsine media) 3/1 — 2.40 — 0.36 Garlic, (Allium sativum) 6/7 0.85 2.44 — 4.64 Kohlrabi, (Brassica campestris) 1/1 2.00 2.00 — 5.50 Cabbage, (Brassica oleracea) 2/1 — 1.99 — 3.06 Tassel flower, (Amaranthus caudatus) 6/2 0.97 2.23 — 1.47 Celery, (Apium graveolens) 2/1 — — — 1.55 Spinach, (Spinacia oleracea) 2/1 — 0.75 0.80 0.42 Coriander, (Coriandrum stivum) 1/4 8.02 5.01 — 1.80 Basil, (Ocimum basilicum) 1/3 — 8.05 — 0.36 Radish, (Raphanus sativus) 4/2 — 2.76 — 1.08 Pepper, (Capsicum frutescens) 3/4 1.97 2.04 3.92 0.88 Kidney bean, (Phaseolus vulgaris) 3/10 2.07 1.78 1.09 1.44 Water convolvulus, (Ipomoea aquatica) 6/3 0.28 1.97 3.50 0.66 # The ratios of relative concentration can not be calculated because the heavy metal contents of rice or vegetables growing in an acidic rain area or in a non-acidic rain area is lower than the method detection limit (MDL) of heavy metals. non-affected areas. The data indicated that the ratios of relative concentration of Cd, Cu, Zn in brown rice and 19 vegetable species growing in an acid rain area (Lung– tang) and growing in an acid rain non-affected area (Lung–luan–tang) sampled from 1996 to 1997 are almost higher than 1, or higher than 3, except for Pb (Table 5). These TRANSBOUNDARY N AND S AIR POLLUTION 359 results suggested that biogeochemical accumulation of heavy metals in brown rice seems not affected by long-term acid rains but on the contrary for vegetables species in northern Taiwan. Therefore, these accumulations are dangerous for humans eating the vegetables produced in acid rain affected area. Table 5 also revealsthatthemeanconcentrationofPbinbrownriceandleavesof19 vegetable species from acid rain affected areas and non-affected areas are almost the same. On the other hand, the ratio is close to 1. This result indicated that acid rain does not influence the biological accumulation of Pb in brown rice and leaves of vegetables species sampled in Taiwan. Some studies have indicated that concentration of Pb in the crops was only affected when the concentration of Pb in the soils is higher than 500 mg/kg (Kabata–Pendias and Pendias, 1992). Sloan et al. (1997) also indicated that the relative bioavailability of biosolids-applied heavy metals in agricultural soils was Cd  Zn >Ni >Cu Cr >Pb, for the soils 15 years after biosolids application. It is quite consistent with the results achieved by research of Chen et al. (1998). Thus, the phyto-availability of heavy metals caused by acid deposition followed the trend: Cd >Zn >Cu  Pb. Finally, this determines the exposure pathways and environmental risk values to human beings. CHAPTER 18 TRANS-BOUNDARY HM AIR POLLUTION Pollution of the environment by heavy metals is the subject of concern of a number of national and international bodies. In 1998 a number of Parties to the Convention on Long-Range Trans-boundary Air Pollution (hereinafter the Convention) signed the Protocol on Heavy Metals (Protocol). The aim of the Protocol was to control atmo- spheric emissions of toxic metals (lead, cadmium and mercury). In accordance with the Protocol the Co-operative Program for Monitoring and Evaluation of Long-Range Transmission of Air Pollutants in Europe (EMEP) provides assessments of pollution levels of heavy metals in the European region. Measurements of heavy metal concen- trations in the air and precipitation are carried out at the EMEP monitoring network. Along with that the Meteorological Synthesizing Centre-East (MSC-E) performs model assessments of depositions and air concentrations of heavy metals throughout the European region as well as trans-boundary fluxes between the European coun- tries (http://www.msceast.org/reps). In 2003 the Protocol on Heavy Metals came into force, and at present the second priority metals (As, Ni, Cr, Zn, Cu) are under pollution assessment. In order to correlate the existing pollution levels with the environment risk to human and ecosystem health, they are compared with scientifically sound crit- ical loads, developed by the Working Group on Effects (WGE). The environmental risk of heavy metals is related to various sources, and the trans-boundary pollution plays a very important role for the European region. 1. MONITORING OF HEAVY METALS IN EUROPE 1.1. Emissions of Heavy Metals in Europe The resulting maps of the spatial distribution of lead, cadmium and mercury anthro- pogenic emissions in Europe in 2002 are presented in Figures 1–3 respectively (Ilyin et al., 2004). According to the available data the most significant sources of lead emissions are located in Central Europe (Poland, Germany), Southern Europe (Italy, Croatia, Serbia and Montenegro, Romania, Greece) and Eastern Europe (Russia). In contrast, emissions of cadmium are distributed more or less uniformly over Western, Central and Southern Europe except Poland, where emission levels are significantly higher. Low emissions are in Northern Europe and in some countries of Eastern Eu- rope (Belarus, Ukraine). The most significant emissions of mercury are also located in Western, Central and Southern Europe. The total emission of lead, cadmium and mercury in Europe in 2002 amounts to 8,003 t/yr, 257 t/yr and 180 t/yr respectively. 361 362 CHAPTER 18 Figure 1. Spatial distribution of lead anthropogenic emission in Europe in 2002. Apart from anthropogenic emissions, heavy metals enter the atmosphere ofEurope due to re-emissionof previously deposited substances andfrom natural sources. These types of sources aretakeninto account on thebasis of expert estimates made inMSC-E (Ryaboshapko and Ilyin, 2001; Travnikov and Ryaboshapko, 2002). Figure 2. Spatial distribution of cadmium anthropogenic emission in Europe in 2002. TRANS-BOUNDARY HM AIR POLLUTION 363 Figure 3. Spatial distribution of mercury anthropogenic emission in Europe in 2002. 1.2. Re-emission of Mercury Natural emission and re-emission processes are particularly important for the mercury cycle in the environment. The distribution of mercury re-emission from soil in Europe is illustrated in Figure 4. The most significant re-emission fluxes are in Central Europe Figure 4. Spatial distribution of mercury re-emission from soils in Europe. 364 CHAPTER 18 Figure 5. Spatial distribution of mercury natural emission in Europe. in the regions where intensive depositions have been observed for a long time. The spatial distribution of estimated natural emission of mercury in European region is shown in Figure 5. Rather high emission fluxes are from soil of the geochemical belt in the south of Europe and from coastal seawater with intensive primary carbon production. According to these estimates the total annual emission of mercury from natural sources and re-emission from European soil and marginal seas are 100 and 50 tons respectively (Ilyin et al., 2004). 2. MODELING OF HM CYCLING As a rule, simulations consider emissions of heavy metals from anthropogenic and natural sources, transport in the atmosphere and deposition to the underlying surface (Figure 6). It is assumed that lead and cadmium are transported in the atmosphere only as a part of aerosol particles. Besides, chemical transformations of these metals do not change removal properties of their particles-carriers. On the contrary, mercury enters the atmosphere in different physical and chemical forms and undergoes numerous transformations during its pathway in the atmosphere (Ilyn et al., 2002; 2004; Ilyin and Travnikov, 2003). 2.1. Atmospheric Transport The transport of heavy metals in the atmosphere is described by means of a monotone version of Bott’s advection scheme. Pressure-based s-coordinate in the vertical makes possible totakeintoaccountaneffectoftheunderlyingsurface elevation.Verticaleddy TRANS-BOUNDARY HM AIR POLLUTION 365 Figure 6. The model scheme of heavy metal behavior in the atmosphere (Ilyin et al., 2004). diffusion is described in the models to consider air mass mixing in the atmospheric boundary layer. 2.2. Mercury Transformation Scheme Both models apply the same chemical scheme of mercury transformations. It is as- sumed that mercury occurs in the atmosphere in two gaseous forms—gaseous ele- mental Hg0, gaseous oxidized Hg(II); particulate oxidized Hgpart, and four aque- ous forms—elemental dissolved Hg0 dis, mercury ion Hg 2+ , sulphite complex Hg(SO 3 ) 2− 2 , and aggregate chloride complexes HgnClm. Physical and chemical trans- formations include dissolution of Hg0 in cloud droplets, gas-phase and aqueous-phase oxidation by ozone and chlorine, aqueous-phase formation of chloride complexes, reactions of Hg 2+ reduction through the decomposition of sulphite complex, and adsorption by soot particles in droplet water. 2.3. Removal Processes Heavy metals are removed from the atmosphere by means of surface uptake and precipitation scavenging. The ecosystem-specific dry deposition scheme is based on the resistance analogy approach and distinguishes 16 land use types. Wet removal by precipitation considers both in-cloud and sub-cloud scavenging. 366 CHAPTER 18 2.4. Model Development The following modifications of the models have been conducted this year: The advection scheme of the regional model is improved to take into account the surface orography. Terrain following vertical structure of the model domain with higher resolution was incorporated.Wet removal of heavy metals from the atmosphere was enhanced by developing new parameterizations of precipitation scavenging. Both in-cloud and sub-cloud wet removal were modified on the basis of the up-to-date scientific literature data. The general structure of a low-resolution multi-compartment model of mercury circulation in the environment was formulated. The atmospheric part of the model was developed and tested. 3. TRANS-BOUNDARY AIR POLLUTION BY LEAD, CADMIUM AND MERCURY IN EUROPE Assessments of atmospheric pollution have been made by the regional (MSCE-HM) and the hemispherical (MSCE-HM-Hem) transport models developed in MSC-E (Ilyin et al., 2004). The regional model covers the EMEP region (European domain) with the spatial resolution of 50 × 50 km; the hemispheric model describes the atmo- spheric transport within the Northern Hemisphere with the spatial resolution of 2.5  × 2.5  . The main outputs of the modeling include data on heavy metal concentration in the air and precipitation as well as levels of deposition to the surface. Since the negative impact of heavy metals on human health and biota is mainly attributed to their long-term accumulation in environmental media, particular attention has been given to the assessment of their depositions from the atmosphere. 3.1. Pollution Levels in Europe Depositions and concentrations of lead, cadmium and mercury were evaluated on the basis of emissions and meteorological data for 2002. Lead In 2002 anthropogenic emissions of lead in Europe amounted to 8 × 10 3 tons per year (kt/yr). This is about 11% less than in 2001. In addition, natural emissions and re-emissions made up 1 kt/yr. The total depositions to Europe in 2002 were 6.7 kt. Spatial distributionoflead depositions in Europe variestoa largeextent. A detailed pattern of the spatial distribution is given in Figure 7. In the central and southeastern parts of Europe, e.g. in Belgium, Poland, Italy, Serbia and Montenegro, depositions are the highest and can exceed 2 kg/km 2 /yr. Similar values of depositions are char- acteristic of the central region of Russia. These high depositions are caused by the significant emission sources located in these regions. Atmospheric pollution in dif- ferent countries can be illustrated by deposition fluxes averaged over the country area, and Serbia and Montenegro are characterized by the highest averaged deposi- tion flux of lead (about 1.5 kg/km 2 /yr). High deposition fluxes are also obtained for [...]... HELCOM countries’ emission of lead, cadmium, and mercury deposited to the Baltic Sea (mean values for years 199 0, 199 5 and 2000) TRANS-BOUNDARY HM AIR POLLUTION 3 79 Catchments Study Small catchment study of biogeochemical mass balance of mercury was carried out in southern Sweden in early 199 0s The fluxes of methyl Hg (Hgm ) and total Hg (Hgt ) were monitored (Figure 23) Much of the Hgt pool was found... during 197 5– 199 0 (Figure 25) These long-term small catchment study results suggest that stream water concentrations are very low and not a water quality concern In addition, a study of lead in soil solution and stream water following a commercial whole-tree harvest at Hubbard Brook showed that Pb was not released to drainage waters from clearcutting activities (Fuller et al., 198 8) CHAPTER 19 TRANS-BOUNDARY... time ( 197 0–2001) In general, the trends of PCDD/Fs content in air and seawater followed the emission variation The trend of PCDD/F accumulation in soil was strongly different from that of emissions Emissions began to reduce in 198 0, whereas the decrease in soil contamination started in 199 0 The rate of the soil content decrease is much lower This causes substantial TRANS-BOUNDARY POP TRANSPORT 3 89 Figure... distribution of lead anthropogenic emission in the Northern Hemisphere (a) and in Kazakhstan and Kyrgyzstan (b) in 199 0 (Ilyin et al., 2004) TRANS-BOUNDARY HM AIR POLLUTION 375 Figure 16 Spatial distribution of annual lead deposition in the Northern Hemisphere (a) and in Kazakhstan and Kyrgyzstan (b) in 199 0 (Ilyin et al., 2004) deposition of lead to Kazakhstan and Kyrgyzstan amounted to 3.5 kt/yr and 0.43 kt/yr,... decreased during the period of 199 0–2001 In particular, annual emissions of cadmium decreased by 45%, whereas lead and mercury emissions reduced by 60% Following this reduction and also due to the changes of heavy metals emissions in other European countries the level of atmospheric depositions to the Baltic Sea has also significantly decreased (Figure 20) Compared to 199 0 Figure 20 Decrease of cadmium,... countries and in the Northern Hemisphere as a whole is assessed with the global emission inventory for 199 5 (Pacyna et al., 2003) According to these data the total anthropogenic emission of mercury in the Northern Hemisphere was about 190 0 t/yr, the emissions of mercury in Kazakhstan and Kyrgyzstan were 49 and 2.6 t/yr, respectively Figure 12 illustrates the spatial distribution pattern of anthropogenic... Forest ecosystems has been studied at the Hubbard Brook Experimental Forest in New Hampshire The small catchment approach has been used to study the lead biogeochemical cycle since 196 3 (Likens et al., 197 7; Driscoll et al., 199 4) By monitoring precipitation inputs and stream output from small watersheds that are essentially free of deep seepage, it is possible to construct accurate lead mass balance The... ecosystems of Hubbard Brook Experimental Forest, USA (Driscoll et al., 199 4) 382 CHAPTER 18 Figure 25 Temporal pattern of the concentration of Pb in the biogeochemical reference watershed at the Hubbard Brook Experimental Forest, NH, USA: (a) bulk precipitation; (b) the forest floor; (c) stream water (after Driscoll et al., 199 4) HBEF, much of the lead entering the ecosystem from the atmosphere appears... and losses in stream water are low There was a strong correlation between concentrations of Pb and dissolved organic carbon (DOC) in soil solution and stream water at Hubbard Brook Driscoll et al., 199 4, 199 8) Pools and uptake of lead in vegetation at Hubbard Brook were insignificant Lead is not a plant essential nutrient and therefore it is not surprising that uptake was low The calculated weathering... emission in the Northern Hemisphere (a) and in Kazakhstan and Kyrgyzstan (b) in 199 5 Black line in the left figure delineates the EMEP region (Ilyin et al., 2004) TRANS-BOUNDARY HM AIR POLLUTION 373 Figure 13 Spatial distribution of annual mercury deposition in the Northern Hemisphere (a) and in Kazakhstan and Kyrgyzstan (b) in 199 5 (Ilyin et al., 2004) emission sources (e.g., in the Central Pacific) On the . by acidic rains) and Lung–luan–tang area (non-affected by acidic rains) from 199 6 to 199 7 in Taiwan (Chen et al., 199 8). acid rain/non-acid Ratio in acid rain/non-acid rain affected area rain area Rice. Zn in brown rice and 19 vegetable species growing in an acid rain area (Lung– tang) and growing in an acid rain non-affected area (Lung–luan–tang) sampled from 199 6 to 199 7 are almost higher than. to Kyrgyzstan—2 .9 t/yr. 4.2. Lead The assessment of lead contamination in Kazakhstan and Kyrgyzstan is based on the global lead emission inventory for 199 0 (Pacyna et al., 199 5), the only available dataset