*3.6.3 Methods for arsenic's reduction*

*Protecting Rice Grains in the Post-Genomic Era*

*3.5.3 Status of As toxicity management*

free freshwater sources (about 1000 l/m2

Bioremediation process for getting As-free GW for irrigation that was tested needs additional huge investment (two ponds, DW production cost, cost of labor, etc.). Moreover, an estimated 1.539 g As will remain in the bottom of the pond after treatment. Disposal of the arsenic-loaded DW to nontoxic level through various uses was hazardous (Section 3.5.2). STW and DTW waters were found to become arsenic contaminated in 2–5 years. Withdrawal of the GW contaminates biosphere permanently, i.e., circulating the element in the nature in a matter of weeks or months affecting biotic components (**Figure 3a**–**d**). Therefore, alternative arsenic-

water/kg arsenic-free rice cultivation in clayey soil) have to be managed for feeding millions of people of Bangladesh on the one hand and saving our biosphere on the

There are 64 districts, out of which 26 were arsenicosis affected in various degrees surveyed between 1993 and 1997 [1] (**Figure 1**): (a) highly affected (>100 patients identified) in 7 districts, (b) moderately affected (>50 patients identified) in 11 districts, (c) less affected (<50 patients identified) in 8 districts, and (d) arsenic contamination present (no patient was identified) in 18 districts. Out of 64 districts, 42 were distributed in four floodplains: (a) Ganges had 26 districts (7 highly affected), (b) Meghna 10 districts (1 highly affected) and (c) Surma-Kushiara 5 districts with arsenic presence but no patients were found, (d) Jamuna 2 districts without any patient, and (e) 2 districts in Madhupur tract (less affected) all due to drinking and consuming arsenic-contaminated GW and food grains/vegetables. Two-thirds of the districts/country was affected with arsenic by the year 1997 [1]. Highly affected Bagerhat and moderately affected major part of Sundarbans south of the Ganges floodplain along the coast are alarming, indicating coastal water pollution. Data on arsenic in irrigation water and paddy soil profiles in Bangladesh [16] and West Bengal [51] indicated a yearly input of 1.0 and 1.1 mg As/kg soil, respectively, in the topsoil (soil density of 1 kg/l). Therefore, distribution of arsenicosis reported in 1997 [1] would be much higher over the last two decades through arsenic toxicity of rice, wheat grains/vegetable,

Why the Ganges and Meghna floodplains are so much affected with GW arsenic, when Jamuna floodplain with one of the largest and longest river is not? Is it that the GW of the two highly affected floodplains has some link with arsenic mines/ industries or there are anthropogenic reasons (dumping the contaminant, deep into

The total area under irrigation in Bangladesh is 4 million ha, and 75% is covered by GW resources: 2.5 m ha via 924,000 STWs (main source of GW As) and 0.6 m ha via 23,000 DTWs [11]. DTW for irrigation is installed at about 100 m depth, and in Jessore alone 74 among 85 DTW used for irrigation had >50 μg As/l arsenic [51]. The rest 25% land is irrigated using surface water of rivers, "Beels," "Haors," etc. In dry season, 3.5 m ha is used for Boro rice, 0.23 m ha for wheat, and 2.7 m ha for other crops. Rajshahi Division has the highest percentage under

other hand. It is possible only by using surface water (Section 3.6.3).

**3.6 Current status of arsenic management in Bangladesh**

*3.6.1 Occurrence and level of arsenic toxicity in Bangladesh*

etc. if not by arsenic-contaminated drinking water [17].

/year equivalent to 2500 l or 2500 kg

**142**

the aquifer) in upstream?

*3.6.2 Intensity of irrigation*

It has been clearly indicated that As concentrations in rice are increasing over time because of prolonged input of As-contaminated irrigation water, and three options are proposed to free rice grains from toxicity: reduce As-contaminated irrigation water use in rice cultivation, promote cropping patterns, and select/ breed rice cultivars that are tolerant to As and have limited uptake of As [11]. As per the first option of limited As-contaminated irrigation water use, there must be alternative sources of huge surface water, e. g., initially forming reservoirs and constructing rubber dams in rivers, and execution of long-term "Delta Plan 2100". Regarding the second option, cropping pattern throughout the country has been established over the decades of testing, while selection/breeding of rice varieties tolerant to As and limited uptake are questionable. It is known that As and P elements are in the same position in the periodic table (chemically similar), and thus the rice cultivar that will not absorb As will not absorb P as well. In the present study, arsenic bio-mitigation of irrigation water tested was not effective, and disposal of wastes was hazardous. As arsenic-contaminated GW produces toxic rice grains and accumulates arsenic in the soil year after year, avoiding the use of GW is the only solution for protecting rice grains from arsenic toxicity, including other organisms. Man might alter the quantities of arsenic in any component of an ecosystem in a localized area but cannot change or stop the natural biological processes that occur [52]. Therefore, an alternative immediate attention is needed to provide enormous volume of As-free irrigation water, and that is through the use of surface waters using river network of Bangladesh (**Figure 10**). Bangladesh is a country of rivers having almost one river in each village. The rivers have to be dredged to get continuous flow of waters from the upstreams, converting the rivers as reservoirs simultaneous with the construction of rubber dams. Several rubber dams have so far been installed in Bangladesh, one of which is at Sonargaon (**Figure 11**). Bangladesh government has the plan to establish **"Ganges Barrage"** to supply freshwater to Ganges floodplain and surroundings including Sundarbans [53]. Huge deposit of sediments in the Ganges River bed has been identified as a major problem (what to do with the sediments) for using the Ganges as a reservoir [personal communication, Rawshan Ali Khan, Project Director of Ganges Barrage Project, Dhaka, Bangladesh].

The National Economic Council (NEC) of Bangladesh has recently approved **"Delta Plan 2100"** the key objective of which is to provide food and water security and fight natural disasters [54]. The theme is "let the rivers flow, let the rivers live." In the first phase, the government will be implementing about 80 projects at an estimated cost of US \$ 37 billion by 2030. Out of six goals, Delta goal 3 is "Ensuring sustainable and integrated river systems and estuaries." In a seminar, it has been mentioned that "rivers would be channelized and sediments would be removed." Details are not available regarding what is meant by the "removal." It immediately indicates dumping sediments on to the river banks!

The landmass of Bangladesh has been formed throughout the Pleistocene and up to the present by sediments washed down from the Himalaya Mountains through the Ganges, Jamuna (Brahmaputra), and Meghna Rivers and their numerous tributaries and distributaries [55]. In terms of relative age of the landmass, the region may be divided into four parts: hilly lands of the Tertiary (and older) in the southeast Chittagong and CHT districts, terrace lands of

### **Figure 10.**

*River network of Bangladesh, where three mighty rivers Ganges, Jamuna (Brahmaputra), and Meghna altogether ended into the bay of Bengal.*

Pleistocene in the Barind and Madhupur Jungle, tipper surface of the early Recent in the median eastern part, and the extensive floodplains of the Recent in the rest of the country (Ganges floodplain and southern part of Meghna floodplain) (**Figures 1** and **10**). Geologists believe that in the same way, the present Sundarbans has been established 7000 years ago [56]. From geophysical

**145**

**Figure 11.**

*the bridge) to hold water in the river during afternoon.*

*Protecting Rice Grains from Arsenic Toxicity through Cultural Management...*

changes on the formation of Bangladesh, it is obvious that sediment-loaded river water flow to the Bay of Bengal resulted from extensive floodplains including Sundarbans [56], and any disruption would cause land degradation, which is already done by Farakka Barrage since 1975 [53]. To reclaim environment of all the floodplains, dredging of Ganges, Jamuna, and Meghna River beds along with tributaries and distributaries making them flow round the year is primarily needed and letting the dredged sediments flow along with floodwater during June to October, up to the Bay of Bengal", the way Bengal Delta was formed [53, 56]. The surface water is ideal in the sense that it contains all the nutrient

*Rubber dam installed in the old Brahmaputra River at Sonargaon, Bangladesh, in 2003. (a) Showing low water volume in the river bed at noon time, on the north of bridge, and(b) rubber dam inflated (on the left of* 

*DOI: http://dx.doi.org/10.5772/intechopen.85909*

*Protecting Rice Grains from Arsenic Toxicity through Cultural Management... DOI: http://dx.doi.org/10.5772/intechopen.85909*

### **Figure 11.**

*Protecting Rice Grains in the Post-Genomic Era*

**144**

**Figure 10.**

*altogether ended into the bay of Bengal.*

Pleistocene in the Barind and Madhupur Jungle, tipper surface of the early Recent in the median eastern part, and the extensive floodplains of the Recent in the rest of the country (Ganges floodplain and southern part of Meghna floodplain) (**Figures 1** and **10**). Geologists believe that in the same way, the present Sundarbans has been established 7000 years ago [56]. From geophysical

*River network of Bangladesh, where three mighty rivers Ganges, Jamuna (Brahmaputra), and Meghna* 

*Rubber dam installed in the old Brahmaputra River at Sonargaon, Bangladesh, in 2003. (a) Showing low water volume in the river bed at noon time, on the north of bridge, and(b) rubber dam inflated (on the left of the bridge) to hold water in the river during afternoon.*

changes on the formation of Bangladesh, it is obvious that sediment-loaded river water flow to the Bay of Bengal resulted from extensive floodplains including Sundarbans [56], and any disruption would cause land degradation, which is already done by Farakka Barrage since 1975 [53]. To reclaim environment of all the floodplains, dredging of Ganges, Jamuna, and Meghna River beds along with tributaries and distributaries making them flow round the year is primarily needed and letting the dredged sediments flow along with floodwater during June to October, up to the Bay of Bengal", the way Bengal Delta was formed [53, 56]. The surface water is ideal in the sense that it contains all the nutrient

elements in relatively the same proportion (Redfield ratio) for irrigating rice and other crops and protecting crops and biota from arsenic toxicity. Increased surface water would reduce GW salinity in the southwestern Bangladesh and increase productivity in the hinterlands [53]. To get rid of arsenics, protecting surface water is the only environmentally benign option saying "no to groundwater for irrigation, let the arsenic stay in the underground*.*" The water reservoirs may integrate aquaculture of DW and *A. pinnata* var. pinnata for fish and poultry feeds [57].
